Bond, Steven (1991) Control of rhizome growth in Alstroemeria. PhD

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Bond, Steven (1991) Control of rhizome growth in
Alstroemeria. PhD thesis, University of Nottingham.
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CONTROL
OF RHIZOME
IN
GROWTH
ALSTROEMERIA
by
STEVEN
BOND
B. Sc., M. Sc.
Nottingham
Thesis submitted
to the University
of
for the degree of Doctor of Philosophy
October
.
1991
ýcr+sr.
Department of Agriculture and Horticulture
Faculty of Agricultural and Food Sciences
University of Nottingham
Sutton Bonington
Loughborough
LE12 5RD
Abstract
Increases of temperature
in the range from 8 to 18°C in vivo, significantly
enhanced the dry weights of lateral
dry weight
temperatures
in irradiance
rhizomes,
was often seen to decrease.
production
from 100 to 50 per cent in vivo, produced
in the dry weights
of lateral
rhizomes,
of lateral
rhizomes,
tubers
numbers
and irradiance
temperature
hours light
in a 24 hour
the dry weights
in either
daylength
rhizome production
or numbers
influence
had a strong
a temperature
and a short daylength
in vivo produced
of plant
decreases
In contrast,
and shoots were largely
Daylength
Decreases
significant
and shoots.
roots
treatments.
period
At the higher
roots and shoots.
of 8 to 16
few significant
produced.
over the time of flowering.
by
unaffected
treatments
parts
the
changes
However,
For maximum
of between 13 and 18°C, a high irradiance
were required.
Increases of temperature
in the range 8 to 18°C in vitro, caused significant
increases in the number
of lateral
highest
temperature
roots produced
the numbers
was unaffected
rhizomes
often decreased.
produced
by temperature.
produced
no significant
rhizomes,
roots or shoots produced
etiolation
of the shoots.
for the culture
Win-
2 with a daylength
changes in the number
in vitro.
Low irradiance,
were a temperature
of
from
from 8 to 20 hours light
For a good multiplication
environment
The number
Decreases in irradiance
100 to 25 per cent and increases in daylength
a 24 hour period,
At the
and shoots produced.
in
of lateral
however, caused
rate the requirements
irradiance
15°C,
of
an
of 5
of 8 hours of light in a 24 hour period.
The presence or absence of tubers and damage suffered by `splits' prior to
planting
in vivo.
be
found
important
to
were
factors
in the establishment
of plants
Subculture
of rhizome explants
rhizome explants
divided
without
into single internodes
enhanced the rhizome multiplication
lators triiodobenzoic
acid and paclobutrazol
significant
duced.
aerial shoot or rhizome
rate. Addition
acid, thidiazuron,
to culture
changes in the numbers
However, paclobutrazol
with or without
media, with and without
produced
shoot size was reduced and the diameter
aerial shoots,
of the plant growth regu-
a-naphthaleneacetic
of lateral
apices and of
rhizomes,
acid, gibberellic
BAP, caused no
shoots or roots pro-
changes in explant
morphology,
of roots was increased.
i. e.
Acknowledgements
I would like to thank
for their financial
R. A. Goemans and Parigo Horticultural
and technical
for use in this study.
Martin
Mr.
for
the plant material
and
assistance
I would also especially
like to extend
Squire for his help and advice throughout
for the experimental
Co. Ltd.,
provided
my gratitude
to
my work and to Julia Mills,
work to which she contributed.
I would also like to thank my supervisor Dr.
Peter Alderson, for the help
given during my studentship and in the completion of this thesis.
I would
like to thank
maintenance
Howse for her help in the preparation
of many of niy experiments,
for their technical
Hunter
Dorothy
support
for his help with
Mike Yoemans
and help in maintenance
the photographs
that
and Terry
of experiments
and
Travers
and Barry
were taken.
I would like to acknowledge the financial support of the Ministry
of Agricul-
ture, Fisheries and Food, during the first two years of my studentship and
the various institutions,
who helped to provide some of the finance required
for the completion of my work.
Finally, I would like to thank the friends I have made during my time here
for their kindness and generous help.
Contents
List of Figures
V
List of Tables
vii
List of Appendices
ix
List of Abbreviations
1 GENERAL
INTRODUCTION
1.1
INTRODUCTION
1.2
ALSTROEMERIA
1.3
1.4
x
AND AIMS OF THE STUDY
1.2.2
Morphology
1.2.3
Breeding
1.2.4
Propagation
1.2.5
General Culture
1.2.6
Economic
..................
and Development of the Rhizome
In Vitro
APICAL
Rootstock
3
7
10
........................
12
......................
13
..................
IN VIVO AND IN VITRO RESEARCH
1.3.2
1
2
..........................
Importance
1
2
Description
Taxonomic
In Vivo
.......
........................
1.2.1
1.3.1
REVIEW
AND LITERATURE
............
14
..........................
18
..........................
DOMINANCE
.....................
21
1.4.1
The Mechanism
1.4.2
Growth Regulator Control of Apical Dominance
....
of Apical
14
Dominance
..........
1.4.2.1
Triiodobenzoic
1.4.2.2
Cytokinins
1.4.2.3
Auxin-cytokinin
1.4.2.4
Gibberellins
1.4.2.5
Paclobutrazol
1.4.2.6
Ethylene and abscisic acid
...........
synergism
23
23
acid ...............
and thidiazuron
21
..........
...........
...................
..................
25
27
28
29
32
i
2
MATERIALS
GENERAL
2.1
SOURCE OF PLANT
2.2
GROUP BACKGROUNDS
ISTICS
.............
2.3
3
AND
GENERAL
In Vivo
2.3.2
In Vitro
34
MATERIAL
CULTURAL
2.3.1
METHODS
...............
AND GENERAL CHARACTER...............
CONDITIONS
..
............
37
39
..........................
MEDIA
2.5
DATA RECORDING
PREPARATION
THE EFFECT
DAYLENGTH
....................
AND ANALYSIS
40
40
.............
AND
OF TEMPERATURE,
IRRADIANCE
ON RHIZOME
GROWTH
IN VIVO
3.1
INTRODUCTION
3.2
THE EFFECT
......................
OF TEMPERATURE
42
..
..
............
Materials and Methods
................
3.2.2 Results
.........................
THE EFFECT OF IRRADIANCE
.............
3.2.1
3.4
3.3.1
Materials
3.3.2
Results
and Methods
..
..
..
................
..
.........................
..
OF DAYLENGTH
THE EFFECT
.............
..
................
3.4.2 Results
.........................
DISCUSSION
.........................
3.4.1
3.5
3.6 CONCLUSION
4
..
..
..
........................
..
FACTORS
AFFECTING
THE ESTABLISHMENT
PLANT
MATERIAL
OF ALSTROEMERIA
4.1
INTRODUCTION
4.2
THE EFFECT
4.3
4.2.1
Materials
4.2.2
Results
THE
4.3.1
EFFECT
........................
OF TEMPERATURE
and Methods
42
42
42
43
48
48
48
49
49
53
53
61
OF `SPLIT'
63
63
64
..............
64
..................
64
...........................
OF REMOVAL
34
37
..........................
2.4
3.3
34
OF THE
..................
ROOTSYSTEM
..
65
65
11
4.3.2
4.4
5
...........................
THE EFFECT OF TUBER EXTRACTS
4.4.1
Materials
4.4.2
Results
4.5
DISCUSSION
4.6
CONCLUSION
and Methods
EFFECT
IN VITRO
74
74
ON GROWTH
IN VITRO
75
75
Discussion
75
75
.........................
VITRO
OF THE
76
............
5.3.1
..................
76
5.3.2
Results
77
...........................
Discussion
.........................
77
IRRADIANCE
OF TEMPERATURE,
GROWTH
ON RHIZOME
IN VITRO
INTRODUCTION
6.2
THE EFFECT
....................
OF TEMPERATURE
............
................
6.2.2
Results
.........................
THE EFFECT OF IRRADIANCE
6.3.1
Materials
6.3.2
Results
THE EFFECT
and Methods
80
..
..
..
.............
................
.........................
OF DAYLENGTH
AND
..
6.2.1
..
..
..
.............
................
6.4.2 Results
.........................
DISCUSSION
.........................
CONCLUSION
........................
6.4.1
6.6
73
........................
OF EXPLANT DENSITY
6.1
6.5
67
..................
Results
...........................
THE EFFECT
DAYLENGTH
6.4
66
67
COMPARISON OF THE GROWTH IN
CULTIVARS
FOUR ALSTROEMERIA
5.3.3
6.3
.....
..................
INVESTIGATIONS
5.2
5.3
66
..........................
INTRODUCTION
5.2.3
IN VITRO
...........................
5.1
5.2.2
66
...........................
PRELIMINARY
5.2.1
6
Results
..
..
..
..
..
80
81
81
81
84
84
85
85
85
87
87
90
iii
7
OF APICAL
DOMINANCE
RATE OF THE RHIZOME
THE INFLUENCE
MU LTIPLICATION
7.1 INTRODUCTION
7.2
7.3
MECHANICAL
7.2.1
Materials
7.2.2
Results
CHEMICAL
Materials
7.3.2
Results
TIBA
7.3.2.6
8
DISCUSSION
8.1
8.2
94
..................
98
98
.....................
98
106
99
102
..................
106
...........................
Chemical
Control
Control
Dominance
of Apical
of Apical
7.4.2.1
TIBA
7.4.2.2
Thidiazuron
7.4.2.3
BAP/NAA
7.4.2.4
GA3
7.4.2.5
Paclobutrazol
Dominance
........
.........
......................
112
113
...................
114
...................
114
.......................
115
..................
116
..........................
118
CONCLUSIONS
............................
SUGGESTIONS FOR FUTURE
106
112
118
GENERAL
References
.....
94
Paclobutrazol
7.4.2
AND
DOMINANCE
102
Mechanical
SUMMARY
94
......................
Thidiazuron
...................
NAA/BAP
...................
GA3
.......................
7.4.1
CONCLUSION
...
93
93
...........................
7.3.2.2
7.3.2.5
DOMINANCE
..................
and Methods
General
7.3.2.4
7.5
OF APICAL
and Methods
7.3.2.1
7.3.2.3
7.4
........................
CONTROL
91
91
...........................
CONTROL OF APICAL
7.3.1
ON THE
IN VITRO
WORK
............
120
122
IV
List
Figures
of
1.1
The distribution
1.2
The inflorescence
cultivars
of the genus Alstroemeria
and a portion of the stem from three hybrid
of Alstroemeria
.....................
1.3
The morphology
1.4
The morphology
of the distal
s troerneria .............................
1.5
in South America
of Alstroemeria
of the rhizome
Stages in the development
portion
5
6
........
of the rhizome
.4
of Al8
of a lateral
rhizome of Alstroemeria
9
from the second axillary bud of an aerial shoot
.........
2.1
The rhizome rootstocks of the four cultivars chosen
......
38
3.1
of the cultivars `Butterfly'
and `Valiant'
different
three
temperatures
at
..................
46
3.2
3.3
Growth
The effect of temperature
tivars
................................
4.1
4.2
5.1
6.1
6.2
on plant deaths in Alstroerneria
cul47
Growth of the cultivars `Valiant' and Èleanor' after 20 weeks
at three different
3.4
after 24 weeks
irradiances
Growth
...................
`Valiant' and Èleanor'
of the cultivars
daylengths
different
three
at
52
after 20 weeks
56
...................
The effect of tuber extracts on shoot production by rhizome
cultures of Alstroemeria cultivars
................
68
The effect of tuber extracts on lateral rhizome production
rhizome cultures of Alstroemeria cultivars ............
69
Cultures of the cultivars `Valiant',
`Parade', `Butterfly'
Èleanor', after four weeks growth in vitro
...........
The effect of temperature
on the number of lateral
by
in
Alstroemeria
vitro
produced
cultivars ...........
by
and
78
rhizomes
82
The effect of temperature on the number of shoots produced
in vitro by Alstroerneria
cultivars
................
83
V
7.1
The effect of six explant types on the multiplication
the cultivar
7.2
7.3
`Valiant'
.......................
rate of
types on the multiplication
rate of
The effect of six explant
96
97
.......................
The effect of GA3 on the morphology of rhizome explants of
the cultivar
7.5
95
The effect of six explant types on the multiplication
the cultivar `Parade'
.......................
the cultivar Èleanor'
7.4
rate of
Èleanor'
.......................
The effect of paclobutrazol
on the morphology
plants of the cultivar Èleanor' ..................
of rhizome
105
ex108
vi
List
Tables
of
3.1
3.2
The effect of temperature on the numbers of lateral rhizomes,
tubers and shoots produced by Alstroemeria cultivars
.....
The effect of temperature on the dry weights of rhizome, roots
and shoots produced
3.3
3.4
by Alstroemeria
3.6
by Alstroemeria
55
The effect of explant
the cultivar Èleanor'
Comparison
meria
7.1
temperature
density
deaths
on plant
65
...
by rhizome
70
in vitro on shoot production
in
76
.......................
of the growth
in vitro of four cultivars
of Alstroe77
...............................
The effect of temperature on the number of roots produced in
vitro by Alstroemeria
6.3
......
The effect of daylength on the dry weights of lateral rhizomes,
by
Alstroemeria
cultivars ......
roots and shoots produced
The effect of tuber extracts on root production
cultures of Alstroemeria cultivars
................
6.2
51
54
4.2
6.1
50
The effect of daylength on the numbers of lateral rhizomes,
.....
The effect of establishment
5.2
.........
cultivars
4.1
5.1
45
The effect of irradiance on the numbers of lateral rhizomes,
.....
The effect of irradiance on the dry weights of lateral rhizomes,
3.5
cultivars
44
cultivars
84
..................
The effect of irradiance on the numbers of lateral
by
in
Alstroemeria
vitro
shoots and roots produced
rhizomes,
cultivars
.
The effect of daylength on the numbers of lateral rhizomes,
in
by
Alstroemeria cultivars
produced
vitro
and
roots
shoots
.
The effect of TIBA and BAP on the numbers of lateral rhiby
in
Alstroemeria
and
roots
produced
vitro
zomes, shoots
cultivars ..............................
86
88
100
Vll
7.2
rhizomes,
cultivars
7.3
7.4
7.5
on the numbers of lateral
shoots and roots produced in vitro by Alstroemeria
The effect of thidiazuron
and BAP
101
..............................
The effect of NAA and BAP on the numbers of lateral rhizomes, shoots and roots produced in vitro by Alstroemeria
cultivars
..............................
The effect of GA3 and BAP on the numbers of lateral rhizomes,
shoots and roots produced in vitro by Alstroemeria cultivars
The effect of paclobutrazol
lateral
BAP
the
numbers of
and
on
rhizomes, shoots and roots produced in vitro by Alstroemeria
cultivars
..............................
103
.
104
107
vi"
List
Appendices
of
(MS)
Medium
Revised
Skoog
and
A
Formulation
of Murashige
B
Formulation
of Alstroemeria
C
Stock Solutions of Growth Regulators
D
Preparation
of Alstroemeria
Production
Tuber
Medium
.............
Extracts
..........
.......
.
142
143
144
145
LX
List
Abbreviations
of
ABA
BAP
GA3
-
Abscisic
-
6-Benzylaminopurine
-
Gibberellic
acid
acid
IAA
-
Indole-3-acetic acid
NAA
-
a-Naphthaleneacetic
acid
-
2,3,5-Triiodobenzoic
acid
-
Murashige and Skoog revised medium (Appendix A)
-
Plant
TIBA
MS
PGR
growth
regulator
X
Chapter
LITERATURE
AND
1.1
INTRODUCTION
GENERAL
1:
REVIEW
INTRODUCTION
Alstroemeria,
AND
the `Peruvian
has become increasingly
Lily',
AIMS
is grown as a cut flower crop and as such
in the last few years. In terms of crop area
popular
it is now the second most important
cut flower grown in the United
(Deen, 1986). It is grown extensively
there is a great deal of interest
A limited
number
mainly
of papers have been produced
time to flowering
and the length
rootstock.
propagated
This is surprising
by division
Studies on Alstroemeria
in vitro,
establishing
a micro propagation
centrations
of plant
plants.
Very little
temperature
growth
published
and light
ports
on plant growth
cytokinins
for improving
methods
growth
are vegetatively
in vitro.
have taken place over the last two
These have been related
for multiplication
information
regulators
cultivars
refer-
of the rhizome
system with emphasis on optimising
regulators
on the
Very little
period.
in vivo and by rhizome culture
which
environments
different
the
effect of
or on
factors
on the growth
as most Alstroemeria
only a few publications.
decades, have yielded
in vivo. These papers focus
of the flowering
of the rhizome
the effects of tem-
and environmental
these
is
the
to
of
parameters
effects
made
ence
and
States of America.
detailing
of Alstroemeria
on the effects of time of planting
Kingdom
and Colombia
in the Netherlands
in it also in the United
and light on the growth
perature
STUDY
OF THE
is available
on the growth
of subculture.
the con-
and rooting
either
to
of ex-
on the effect of
of Alstroemeria
in vitro
The only published
relate to the use of auxins for rooting
reand
and shoot proliferation.
The aims of this study were to investigate the effects of (i) temperature and
1
light regimes on the growth of the rhizome of Alstroemeria
(ii)
plant growth
and
rhizome
break apical dominance
The following
vivo and in vitro.
1.2
1.2.1
expressed within
of Alstroermeria
thought
part of the study involved
of the literature
review
of
to
attempts
in order to increase the
explants,
a general description
includes
of the concept of apical dominance,
An overview
the plant
growth
of the
in
on the plant
and a review of the work published
by which
mechanisms
on the growth
methods
bud outgrowth.
rate of axillary
growth
The latter
M vitro.
explants
and subculturing
regulators
in vivo and in vitro
and the
used in this study
regulators
are
to affect it, is also included.
ALSTROEMERIA
Description
Taxonomic
belongs to the family
The genus Alstroemeria
cotyledons
Alstroemeria
(Hutchinson,
are four
(2n=16)
of Alstroemeria
(Lakshmi,
cultivars
(2n=4x=32),
occasionally
amongst
Alstroemeria
is a native of South America
or tetraploid
the triploids
1980; Tsuchiya
are triploids
diploid
i. e.
(one species)
Many of the species are endemic
them
(Healy
(2n=3x=24)
with
aneuploidy
with
1987).
a few
occurring
with Chile as its centre of distribu-
to certain
Wilkins,
and
1985; Uphof,
distributions
wide
(Figure
countries
1952), though
1.1).
Their
habitats
or regions within
some are known
The estimate
1987) may prove to be conservative,
survey of the area was undertaken.
and Hang,
pos-
and tetraploids.
tion.
the genus (Bayer,
Leontochir
species in the genus Alstroemeria
being either
have fairly
of the mono-
genera in this family,
(150 species),
Bomarea
have shown that
studies
Corolliferae
(two species).
sess 16 chromosomes
The majority
There
1959).
(50 species),
Schickendaritwia
and
Cytological
in the division
which is included
Alstroemeriales,
in the order
Alstroemeriaceae
to
in
50
species
of
if a full and detailed
range from the tropical
2
Amazon
area to the snowline
forests and river valleys,
Overall,
1979).
3700m and from Ecuador,
The genus, therefore,
ern Chile.
(Healy
and
the genus ranges from sea level to
is on the equator,
which
the high
through
plateau,
to the western coastal deserts of Chile
1985; Verboom,
Wilkins,
of the high Andean
tolerates
many
to Patagonia
varied
in south-
and often
extreme
environments.
Full
descriptions
(1959),
(1952) and Willis
Uphof
perennials
of the genus Alstroemeria
with a rhizomatous
ina.
through
The inflorescences
cymes, each carrying
are composed
one to five sympodially
(Figure
fruit
produced,
1.2.2
Morphology
copious endosperm
and Development
The roots of Alstroemeria
may be produced
the fibrous
on virtually
mainly
from the newly
the roots and tubers.
after
each loculus and
within
Many
explosively.
seeds are
and a small embryo.
of the Rhizome
Rootstock
tubers,
rhizome
The tubers
(Mabberley,
1987) in quantities
Machtasters,
1947).
root
that
In others,
on the species
new roots arise
apex and, to a lesser extent,
are known
similar
hairs.
the size depending
It was also reported
1951).
formed
Some species lack
any part of the rhizome.
roots and possess only fleshy roots with
1.3A) (Buxbaum,
receptive
both
fibrous
thin
and
are
and thick and fleshy, and
the fleshy roots develop into thick
(Figure
splits
dehisce
has
axile
and
tri-locular
The ovules are numerous
that
The perianth
six stamens that
becoming
and tri-lobed,
lamthe
of
or compound
flowers.
arranged
in two series, with
is a dry capsule
containing
of simple
1.2). The ovary is inferior,
the anthers have dehisced.
the mature
of a whorl
on the
alternately
180° at the base, causing inversion
The style is filiform
placentation.
from which aerial shoots and roots,
rootstock,
segments are free and arranged
at daily intervals
in Hutchinson
The genus consists of herbaceous
arise. The leaves are positioned
which may carry tubers,
stem and are twisted
(1985).
be
found
can
from
to be local sources of starch
to that
found
in potato
(Cox
and
3
Colombia
VPr1
P711
Pl
7
:1
* Ec
*p
3 sp
------
---
- ---a-
Figure 1.1: The distribution of the genus Alstroemeria in South America,
denoting presence in a country. (From Buxbaum, 1951)
4
Figure
1.2: The inflorescence
cultivars of Alstroemeria
and a portion
of the stem from
three hybrid
\. ý,
ýý
ýI ý
aerial shoots
roots
II, Ili
first axillarv bud
aerial shoot
I
1ý
ýý
,ý
'`'. ý`'\
ýýi,
311
lý.
ý
ýý ýý1`.
ýýýý,,,
,
t
'r
Jn
root
ý'ý . J/J i__
B
C
first scale leaf
Figure 1.3: The morphology of the rhizome of Alstroemeria, showing the
arrangement of the roots, shoots, scale leaves and axillary buds, viewed from
A the side, B the front and C at the apex. The sequence of numbers 1-5,
indicates the progression from the older to the youngest shoots, respectively.
(From Buxbaum, 1951)
6
The aerial shoots arise from the rhizome and are positioned
(Figure
length
its
ranks along
1.3A and B). The thickened
this large bud is the axillary
However,
(Buxbaum,
vious aerial shoot
is greatly
enlarged
are suppressed
may die.
basal
internodes
chain of enlarged
whereas development
rootstock,
is developed,
of the rhizome
(Figure
second axillary
beginning
a
is sympodial.
1.4A) also bears an axillary
a lateral
rhizome
of the rhizome.
The
for a long time, only developing
when the base of the aerial shoot dies or is removed.
(Buxbaum,
the
aerial shoot
occur on
internodes
long
monopodial
a
imitating
the ramification
bud may often stay dormant
1.4A
it can be seen that
new aerial shoots and consequently
1.5A and B), thereby
(Figure
further
that
From this
The second scale leaf of the aerial shoot (Figure
bud. This may produce
1.3C).
of the aerial shoot
forward
bud is projected
this occurs to such an extent
and the shoot
(Figure
a
bud of the first scale leaf of the pre-
1951). The first internode
and the axillary
and B). Occasionally
apex develops
appears to be monopodial
large
bud
so that the rhizome
very
in two
alternately
No further
1951; Heins and Wilkins,
axillary
buds
1979; Priestly
et al., 1935).
1.2.3
Breeding
breeding
Alstroemeria
has been in progress for about 40 years, but only after
the first ten years was it possible to release some new hybrids,
difficult
proved
(Goemans,
to hybridize
1962).
Early
most two species hybrids
and only a small number
in this breeding
species was used the resulting
progeny
of seeds were produced
it was observed
programme
were more or less fertile
as the species
but
were completely
that
as soon as a third
sterile.
A small number of Alstroemeria species have been used in the production
Alstroemeria
ligtu
Alhybrids,
Alstroemeria
with
aurantiaca,
and
of modern
stroemeria pelegrina prominent amongst the probable progenitors, especially
(Broertjes
Verboom,
has
been
hybrids
It
1974).
the
and
suggested
earlier
of
that the cause of sterility
in these hybrids was probably through interspe-
aerial shoot
first axis
second scale leaf
first sca]
enlarged basal internode
first axillary bud
first
scz
enlarged basal internode
rvo L
-ý
Figure 1.4: The morphology of the distal portion of the rhizome of Alstroeleaves
the
arrangement
of
shoots,
roots,
scale
and axillary
showing
meria,
buds from A the side and B the ventral surface. (From Buxbaum, 1951)
8
second axillary bud
old aerial shoot
second scale leaf
aerial
ehnnt
old aerial shoot
first axi
second scale leaf
root
_g lateral
rhizome
Figure 1.5: Stages in the development of a lateral rhizome from the second
axillary bud of an aerial shoot. A shows an early stage with the bud enlarging
and Ba later stage with the lateral rhizome supporting its own root and
(From
Buxbaum, 1951)
shoot.
9
hybrid
cific
sterility
the parents
was an unknown
had an unreduced
sterile triploid
the diploid
with
(Broertjes
The latter
number.
and Verboom,
by differences in radiosensitivity
confirmed
(Broertjes
gories
and Verboom,
et al., 1987; Tsuchiya
Due to the sterility
of many
netic variation
and producing
Consequently,
the
through
majority
breeding
mutation
many commercially
(Broertjes
young plants are generally
between diploid
growth
van Harten,
hybrid
seems to be
and triploid
cate-
by cytological
(Hang and Tsuchiya,
1988;
improvements
and Verboom,
Actively
rhizomes
growing
used and all of the mutants
is responsible
1974) and
have now been produced
of Alstroerneria
1978,1988).
have been
to these hybrids
(Broertjes
ge-
are limited.
in these cultivars
of improvements
using X-rays
for inducing
methods
cultivars,
of very
so far, have
produced,
It has been suggested that a
for this phenomenon
1988) rather than a unicellular
and Verboom,
1.2.4
pattern
lead to
and Hang, 1987).
been found to be `solid' ones, i. e. not chimeral.
sympodial
two mechanisms
1974) and has been confirmed
viable mutants
and van Harten,
or one of the gametes
1974). Triploidy
analysis for a large number of the modern hybrids
Tsuchiya
because one of
number,
tetraploid
spontaneous
chromosome
plants
chromosome
(Broertjes
origin of the meristem
and
(Broertjes
1974).
Propagation
Due to the high incidence
duced, seed propagation
are propagated
are lifted
traditionally
in summer
of sterility
and the variability
is uncommon
in Alstroemeria.
by splitting
and carefully
divided
if present,
Consequently,
of the rhizomes.
The plant
into single rhizomes.
rhizomes the apex and up to 10 cm of healthy
and tubers,
of the plants
they
clumps
From these
rhizome is removed with roots
and the aerial shoots are reduced to approximately
cni. These `splits' are grown in small pots until they become established
then they are planted
1981,1986a;
Molnar,
pro-
out into their flowering
1975; Salinger,
positions
1985; Verboom,
(Healy
2
and
and Wilkins,
1979).
10
With
the introduction
tures in controlled
environment
Gabryszewska
Horticultural
and a longer daylength
The in vitro propagation
Co., personal
Pierik
communication;
et at., 1988).
personal
humidity,
Co., personal
crops,
communication;
transferred
environments
of
Horticultural
Co.,
they are ready for planting
out in
has the potential
including
meristems
the growth
to grow into a lateral
rhizome
The adoption
As dis-
buds on each aerial
and a second which
(Buxbaum,
1951; Heins and
of these lateral
or multiplication
and application
rates due to
et al., 1980).
of the rhizome
et al., 1935). As outgrowth
slow then the throughput,
niques to Alstroemeria
(Hussey
a large
and quite
propagation
has in fact only two axillary
continues
1979; Priestly
Alstroemeria
have low natural
of axillary
Alstroemeria
one which
in vivo is low.
(Parigo
are established
plants,
flower
development
cussed earlier
they
up
positions.
of other
is generally
(NAA),
acid
are moved to a glasshouse,
plants
At this point
communication).
restricted
Wilkins,
until
monocotyledonous
number
shoot,
Rooted
Horticultural
(1962).
Co., personal
Horticultural
in small pots and weaned, by passage through
their flowering
Many
(Parigo
are grown
for
l-1
is
2-4
added
mg
at
(BAP)
et al., 1979; Parigo
of ax-
(MS)
Skoog
and
et al., 1988) and a-naphthaleneacetic
for rooting
to 1 mgl-1,
decreasing
temperatures
(George
and
apex
growing
of Murashige
6-benzylaminopurine
(Hussey
shoot proliferation
to compost
communication).
is the proliferation
system used commercially
based on that
medium
To this MS medium
Pierik
6W m-2 be-
1984; Hussey et al., 1979). In this system the explants
on semi-solid
of cul-
of 16 hours.
buds from rhizome explants with an actively
Sherrington,
growth
(1984) suggest the use of higher
and Hempel
of Al-
of 15°C and a 12 hour daylength.
conditions
(Parigo
ing used commercially
(22-24°C)
with subsequent
depends on the light source used, approximately
The irradiance
illary
aseptic techniques,
using standard
stroemeria,
Alstroemeria
much
This involves the manipulation
in vitro.
is now performed
propagation
techniques,
of micro propagation
rhizomes
rate, of the rhizome
of in vitro propagation
does not increase the number
of axillary
tech-
buds present
11
but allows growth and production of lateral rhizomes throughout
the year.
These techniques may also be used to induce higher proportions of these axillary buds to grow out. Therefore, with these techniques, many more plants
may be produced in vitro in one year than may be produced in vivo.
Culture
General
1.2.5
In South America
the species of Alstroemeria
tats
and consequently
and climates
Due to the varied
quirements.
these cultivars
(Keil,
and Òrchid'.
experiment
with
The general
(1980), Healy and Wilkins
Verboom
(1979), Wilkins
(1979).
son
the new hybrid
is grown as a summer
of, for example,
Co., personal
ground
Planting
(1976),
Heins
and
carefully
and Healy
are not frost resistant.
However,
crop without
mushroom
the protection
The plants
out in the autumn,
and Wil-
and Lang
culture.
glass, as many
an increasing
of
area
of glass, in both the U. K.
system is protected
compost
by Anon
and spacing requirements
out under
beds and the plants are lifted
is carried
growers
(1975), Salinger (1985),
is carried
communication).
while
is a brief account of Alstroemeria
The rhizome
and the Netherlands.
mulch
Molnar
(1980),
Wilkins
et al.
of Alstroemeria
cultivars
that
has been described
cultivars
(1981,1985,1986),
The following
culture
principally
information.
cultural
can be found in Bik and Berg (1981)
(1985) respectively.
Commercial
most of the cultural
own setting,
More specific details on the nutritional
of Alstroemeria
environments
it has been suggested
in their
of Alstroemeria
culture
hybrids,
of the new commercial
from studies on a few cultivars,
Alstroemeria
re-
environmental
are now available,
Consequently,
the available
considering
ancestry
many cultivars
have resulted
recommendations
should
have very different
do not respond equally in the same greenhouse
1986). Although
`Regina'
habiin
range
of
a wide
grow
or straw
in the winter
(Parigo
are usually
grown
by a
Horticultural
in prepared
and replaced every two or three years.
preferably
bed.
In some instances,
plants per square meter of
densities
at
planting
five
to six
of
may take place in
12
April
in the U. K. autumn
May,
though
or
Great care should
damage
be taken at lifting
be open, slightly
should
or death.
poor growth
rotting
(Robinson,
acid and well drained,
The plants
(Parigo
are required
nutrients
as the fleshy roots are very brittle
in subsequent
easily, resulting
is still the more common.
planting
make vigorous
Horticultural
can cause
and high levels of
growth
Co., personal
communication).
for the stems is essential as they may reach a height
Support
The soil
1963).
as waterlogging
and
of two meters
or more.
Temperature
is thought
With
ering.
important
the rhizome
and should
be maintained
With
prevent
flower
curring
in spring
induction,
In winter,
Shading
them
seem to be relatively
lighting
15°C in the
and long days in summer
to be seasonal,
appears
ocof
levels tend to in-
and temperature
may be used to bring forward
spring
the daylength.
stems helps prevent growth
Cropping
at the junction
with
Botrytis
have
been
isolated
viruses
now
several
and
becoming
too dense
is
achieved
any stems
or removing
the rhizome.
free of pests with occasional
aphids and caterpillars.
Alstroerneria
would
outbreaks
of spider mites,
can be a problem
in dull weather
(Versluijs
and Hakkaart,
1985).
Importance
Economic
has been grown in the United
plant
for at least 200 years, with
Royal
Botanical
cultivation
should
night
be
may
used to avoid extremes
low light
by increasing
of weak vegetative
Alstroemeria
temperature
flowering
such that
and autumn.
generally
by separating
1.2.6
is very
high temperatures
flower
production.
and enhances
whitefly,
soil temperature
Winter
18°C.
not exceed
Supplementary
flowering.
Thinning
flowof
as the site of perception,
many cultivars
high temperature.
production,
factor in the induction
at 10°C or above and raised to approximately
spring.
hibit
to be an important
Gardens
Kingdom
as an herbaceous
garden
the introduction
of A. pelegrina
to the
Kew
in
A.
1753,
and
at
(Robinson,
1831
since
1963).
aurantiaca
has been in
Over the last two decades, with
13
hybrid
the
new
of
the introduction
deal
of popularity
a
great
gained
to some extent
and Lang, 1989), and the large range of flower colours available.
colour
range, which
shades and intensities
varying
is a product
pink, yellow and white,
of the diverse colour
species. The inner whorl of tepals is generally
dots and it is often
inner whorl
tinted
yellow
in comparison
crops (Healy
1981), which
and Wilkins,
the introduction
meria is now moving
types'
(Eggington,
the world's
over 166 million
(Anon,
other
in considerable
can result
with
production
area of Alstroemeria
et al., 1988).
to the United
Currently
cultivars,
`winter
energy
Alstroeflowering
frone every
worldwide
the Netherlands
had risen to 275
and Colombia
Colombia's
94
cent
of
with
per
States of America.
stems were produced
In the period
in the Netherlands,
year, and almost 88 million
per cent on the previous
Colombia
with
require-
(Deen, 1986).
two largest producers,
being exported
of the
flower
glasshouse cut
1986) and up to 200 stems can be produced
By 1986 the production
(Pierik
These elaborations
improved
of new and
into àll year round'
square meter in production
hectares
base found in the
to the grower is the low temperature
of Alstroemeria
Also, with
of red, orange,
marked with dark streaks and
or white.
ment for flower production,
savings.
1.3.1
with
The
between cultivars.
vary markedly
The attraction
1.3
by the grower
(Healy
includes
has
the long vase life of the flowers
appreciates
is manipulated
of up to three weeks, which
Alstroemeria
has become an important
and consequently
The consumer
cut flower crop.
from Europe,
cultivars
are
production
1988-1989
an increase of 13
stems were produced
in
1989,1990).
IN VIVO AND
IN VITRO
RESEARCH
In Vivo
Several papers have been published during the last 15 years, on the effects
of light and temperature
However,
Alstroemeria
in
the
of
growth
vivo.
on
direct
few
reference to the effects of these parameters on the
only a
make any
14
rhizome. Most of the papers deal with the time to flowering, the length of the
flowering period and the percentage of shoots that are generative. Some refer
to the total number of shoots produced, which is an index of the rhizome
growth.
Powell and Bunt (1984,1986),
the date of propagation
months,
March
the following
until
May remained
vegetative
initiation
occurred
of shoot
inhibition,
until
January,
at which
daylength
factor
vernalization
had been demonstrated
of four weeks at low irradiance
(Healy
work
and Wilkins,
can be fulfilled
either
previously
1982a, 1982b) showed that
weeks, or at 13°C over an extended
production
treatment
during
the flowering
increased,
but
date than
period
period
no difference
period
interactions
of
requirement.
by Healy
a 5°C treatment
levels to promote
at 5°C for a short
of
This suggested
by complex
a vernalization
Sims
in
conditions
seen
were affected less by propagation
being controlled
in May
on the cultivar.
(1979), when they found that plants required
minimum
A period
to commence
was also reported
and possibly
in
time flower
shoots.
vegetative
and short days to be a period of dormancy.
patterns
remained
half of the plants propagated
the decline in shoot production
by season, the effect of the latter
Wilkins
November
or
two to eight weeks, depending
that flower production
temperature,
Often,
the following
or dormancy,
(1985) also considered
low temperature
spring.
Plants
two to four
flowers within
in July, September
in both new and previously
and last for between
This
or May initiated
whereas those propagated
vegetative
have shown that
on several cultivars,
can have a marked effect on flower production.
in January,
propagated
working
flowering.
for a
Further
this cold requirement
of time,
i. e.
of up to 16 weeks.
decreased as the duration
in the total
and
time
six to eight
Total
shoot
of the 5°C
to flowering
was
observed between plants under the two regimes.
Noordegraaf
(1972,1975)
showed that
9°C, the lowest of the temperatures
flower initiation
occurred
earliest
at
tested, and that there was virtually
no flowering at 25°C, the highest temperature tested. However, subsequent
15
was faster at the higher temperatures.
flower development
of shoots increased over the temperature
of generative
percentage
proportion
a higher
stant
of vegetative
percentage
shoots
1990) produced
irrespective
of cultivar,
than
A constant
from
(Blom
16°C
of
soil temperature
the spring
at the con-
grown
plants
Annual
of 15 per cent,
production
In the autumn
and summer.
production
was not affected
tween the spring/summer
and constant
Ke; '-Gunderson
et al. (1989) investigated
temperatures
occurred
and concluded
a 20°C mean daytime
with
temperature
soil temperatures,
that
day temperatures
gave improved
air temperatures
produced
the greatest
air temperature,
at 5 to 25°C, the highest
number
the soil temperature
temperature
year round
with
production.
shoots.
a root
Warmer
whereas cooler
When
plants
of 13°C with the rhizome and roots
shoots, 33 per cent, was pro-
of generative
(Healy
10°C
of
was 13°C, no differences
and Wilkins,
1986c). When
in the percentage
of generative
shoots were seen, regardless of the air temperature
high
in
percentage
resulted
a
which
ments
of flowers
combined
higher yields of generative
air temperature
air and sub-
production
flower grade and stem length,
were grown in a constant
duced at a rhizome
respectively.
the effect of different
of 12 to 14°C which favoured
be-
decreased from 3.1 to 2.2
and the autumn/winter
for uncontrolled
and
dependent.
flower
production
of
but the ratio
in a
15°C. However,
at a constant
a decrease in flower
during
at a soil tem-
increases and decreases were observed which were cultivar
winter,
strate
Alstroemeria
at 21°C for 21 days resulted
flowered
of the shoots
15°C soil temperature.
Piott,
and
have been reported
results
growing
of 15°C for 40 days and then
perature
higher
Similar
(1988).
(1979) showed that
Heins and Wilkins
number
range of 13°C to 25°C, however, the
shoots declined.
Waithaka
and
by Chepkairor
The total
or the daylength.
of generative
Treat-
shoots also produced
high dry weights for roots and rhizomes.
The effect of soil cooling and supplementary lighting has also been considered
by Lin (1984,1985),
who showed that an air temperature
of 15 to 18°C and
16
of between
a soil temperature
of flowering
shoots in spring/summer
high pressure sodium
mentary
spring
and summer
the autumn
flowering
with
11 and 14°C resulted
produced
and winter,
and also in autumn/winter.
lighting
plants with fewer flowering
in October
lighting.
strated
that
greatly
increase yields and advance flowering
planting
(Healy
of flowering
lighting.
et al., 1982; Healy
1983) have reported
similar
interruption
by incandescent
produces
creased the number
night
(1983),
Lin and Molnar
the upper limit
et al.,
incandescent
daylength,
lighting
and quality
1982;
at
was absent.
Healy
and
for up to five hours, which
produced
Similar
1985; Lin
and therefore
was short
(Healy
earlier flowering
results with
by Noordegraaf
a 16 hour daylength
flower production.
can
due to supplementary
Extending
was used as an extension
inand
long day/short
(1972,1975)
was suggested
and
as
this time caused
to occur even earlier but fewer shoots were produced.
periments
natural
stems.
from which
for maximum
of flowering
1976,1979)
have also been reported
treatments
flowering
increases in the number
light
a long day treatment,
of flowering
Krogt,
for shoot and flower initiation
effectively
1986b;
daylength
when natural
or January
by at least three weeks. Other
and Wilkins,
shoots and the advancement
This occurred
Wilkins,
of
and quality
(1973) demon-
Leliveld
in December
than
rather
times of the year when the stimulus
Night
shoots, whereas in
increased the number
this treatment
Supple-
for 16 hours a day in the
provided
the use of supplementary
or without
and Molnar,
number
However, soil cooling also decreased total shoot production,
shoots.
workers
in an increased
In these ex-
hours
of eight
of
not as a night interruption.
As may be expected, under conditions of short days i. e. eight to ten hours,
the flowering of Alstroemeria cultivars is severely inhibited, irrespective of soil
or air temperatures (Healy et al., 1982; Healy and Wilkins,
Wilkins,
1979; Heins and
1979; Lin and Molnar, 1983; Noordegraaf, 1975). However, shoot
production
is not inhibited.
Dambre (1988) used a short day treatment
of
dormancy
hours
in
Alstroemeria
in
the
to
onset
of
nine
prevent
an attempt
cultivars which, as already stated, often occurs in summer. In the first few
17
weeks of the short
the rhizome,
partly
in this season which,
encountered
press flower formation.
Rhizome
by short day treatments.
the daylength
with
After
as previously
formation
are thought
to sup-
were also suppressed
and growth
the number
was stopped
plants increased and there was an increase in rhizome
flowering
which was
and high temperatures
stated,
the treatment
on
daylength
90 per cent of these shoots were vegetative,
to be associated
thought
of shoots were formed
i. e. up to five times the number formed under natural
However,
conditions.
large numbers
day treatment,
numbers
of
and
weight.
In an early publication,
flower
initiation
and
formation
remain
flowering
are not promoted
has an inhibitory
unresolved.
while
by two primary
Healy
or thermophase,
is biphasic.
as a prerequisite
a flush once the thermophase
or photophase,
flush
dormancy
a
and
after
1.3.2
factors,
(1986c)
and Wilkins
flower
These interactions
Alstroemeria
temperature
rhizome
state that
but a continuous
of this interaction
the control of flowering
temperatures,
and that
flower
and
induction
process for each shoot
elongates.
The latest summary
photoperiod,
by the same factors
et al. (1989) suggest that
is not a single event on the rhizome
as the rhizome
development
shoot
that
effect on shoot development.
Keil-Gunderson
is influenced
photoperiod,
(1975) stated
Noordegraaf
(Blom
and Piott,
Plants require a cold induction
to flowering.
has been fulfilled
is strongly
The mechanism
is still
implicated.
of the rhizome
lack of plant growth
1990) suggests that
is believed
substances
unclear.
Cessation
treatment,
that triggers
However,
a
flowering
of
to be due to high soil
and long photoperiods.
In Vitro
Although the commercial propagation of Alstroerneria is carried out in vitro,
very few publications
have been produced
or methods of culture.
4i
ht,
temperature
the
effect
of
on
Qo.
It would appear that only ZivJ(1973) has tried a
White's
Alstroemeria.
MS
for
the
than
medium
propagation of
medium other
18
(1963) was compared
the growth
Recently,
of cultures.
on different
MS medium
with
but no differences
Smith
were observed
(1987) referred to tests
and Bridgen
but few results are presented
media components,
in
in the abstract
published.
sources have also been assessed, for example flower pedicels,
Different
explant
subapical
segments of inflorescence
(Hussey
et al., 1979; King
1973). For good explant
zome segments with
Lin and Monette,
and Bridgen,
growth
stems and rhizome segments
and ease of production,
Cultures
and Monette,
from
initiated
culturing
(1988) demonstrated
the larger the explant,
in relation
sliced
give a
Pierik
rhizome.
of aerial shoots it bears, the lower the rate of axillary
an explant
et al., 1979;
segments
rhizome
those from the intact
with
suggested that
from rhi-
halves or quarters,
1987), or into
poorer response compared
that
1987; Ziý,,
1987; Lin and Monette,
(Hussey
has
been
apex
suggested
an intact
1987).
(Lin
longitudinally
or vegetative
et al.
to the number
bud outgrowth,
and
a single shoot was the most efficient
comprising
Alstroemeria.
way of multiplying
el' 01.
Ziv/(1973)
Although
cytokinins,
respectively,
(1984,1985)
on rhizome
meria in vitro.
shoot growth
growth
branching,
Gabryszewska
and Hempel
BAP
Cytokinins
but inhibited
were reported
and 6-(y, ry-dimeth-
and indole-3-butyric
and rooting,
that the auxins stimulated
rooting,
with
by Pierik
as above, with
branching,
rhizome
stimulated
and the cytokinins
(PBA),
purine
NAA
aerial shoot production
but had no effect on rhizome
regulators
(IAA)
acid
comparisons
of compounds.
and the auxins
They concluded
most effective.
ilar results
(2iP)
BAP
et al.
(kinetin).
of Alstroeand aerial
NAA
being the
with
branching
acid
rooting
and aerial
shoot
being the most effective.
Sim-
(1988) after screening
the addition
of the auxin
the same
indole-3-acetic
6-(benzylamino)-9-(2-tetrahydropyranyl)-9H(zeatin)
6-(4-hydroxy-3-methyl-2-butenylamino)purine
furfurylaininopurine
and
auxins
made any direct
screened the effects of the cytokinins
ylallylamino)-purine
production
(1987) used different
in their work, neither
these groups
of effects within
(IBA)
and Lin and Monette
Bridgen
and Winski
(1989),
and 6-
however,
re-
19
ported
few differences
growth
of Alstroemeria
With
with
irradiance
and light
Pierik
in vitro.
rhizome
explants
between
1.5 and 9.7 W m-2
for rapid propagation.
affected by daylength,
at daylengths
1988). When
multiplication
of 8 hours with
ing a decrease in the rhizome
The in vitro culture
of Alstroemeria
genesis and embryogenesis
gen, 1986; Gonzalez
hybrid
embryos,
reported
(Winski
elimination
sluijs,
from
that
difference
Benito
would
can be cultured
of 6-8 W m-2,
Different
elicit a different
not reach maturity
without
causwould,
cultivars
to achieve organo-
of somaclonal
1990).
at 15°C
range of responses.
is also being studied
and Alderson,
rate at
rates at 10,
multiplication
Alstroemeria
for the production
15
of 15°C was established
temperature
rate.
et at.,
between
was seen
decrease in multiplication
an irradiance
pattern,
cultured
between
at temperatures
no significant
multiplication
and
irradiance
(Pierik
6
8W
to
of
m-2
(1989) after comparing
a similar
Bridgen
rate was not significantly
rate was compared
et al., 1988). An optimum
following
of the rhi-
was made between explants
when comparison
of 8 or 16 hours, at an irradiance
daylength
and a
irradiances
that
reported
multiplication
15 and 20°C. These results show that
although
(1988)
120 AE m 2s-1 was the optimum
that
In addition,
and Winski
of Alstroemeria
lower
irradiances.
the
at
increased
15 and 21°C but there was a significant
by Bridgen
present data on
on the multiplication
et al.
and 24°C, rising by 3'C intervals,
24°C (Pierik
Alstroemeria
had no effect on the multiplication
shoot length
(1989) concluded
Winski
of 8°C for initiating
at 22°C, only two publications
multiplication
the
and Lin and Mon-
Alstroerneria,
when rooting
the effects of temperature
zome, though
and 2iP, on the
(1984), who reported
and Hempel
(1987),
who suggested a temperature
ette
cultures
BAP, kinetin
in culture.
of Gabryszewska
the exceptions
higher
for
need
a
between the cytokinins
The
variants
in vitro
(Brid-
rescue of
in the seed, has also been
and Bridgen,
1988). Likewise,
Alstroemeria
have also been studied
culture
and virus
(Hakkaart
and Ver-
meristem
1985).
20
1.4
1.4.1
DOMINANCE
APICAL
The Mechanism
Recent
of Apical
of this
reviews
(1988).
and Hooley
Dominance
can be found
topic
The growing
shoot apex is known
over a range of developmental
influence
laterals
of
the orientation
events including
and the development
which a plant adopts but they also have the ability
bud meristems,
loses its capacity
on the form
the development
them in a quiescent state until the apex
shoot
apex.
bud.
apex of the axillary
(Tamar,
A small group
directly
1987).
further
After
The ability
apices is not only
of major
development
and develops into the
This phenomenon
to sustain
a supply
ecological
advantage
but
industries,
as axillary
the latter
numbers,
has commercial
via techniques
of vegetative
This suggests that,
al., 1988).
growth
is also required
It has been postulated
of lateral
that
(Hertel
mays
and Leopold,
evidence that the majority
signal.
bud growth
1963; Sheldrake
of auxin transport
polarity
However,
in
bud growth
is
(Richards
et
by the auxin
of transport
from the
tabacum and coleoptiles
and Northcote,
it is
other than those
this signal is provided
segments of Nicotiana
and plant
meristems,
before lateral
lateral
which has been shown to have a basipetal
shoot apex in internodal
and horticultural
in these species, hormones
bud may control
by the apical
integrated.
are
propagation.
the apex is the source of some correlative
stimulated.
produced
and development
can be used to increase yields
outgrowth
defoliation
some grass species
of replacement
is also an excellent
value in the agricultural
Since removal of the shoot apex stimulates
that
bud is formed
a visible
of a plant
of the way in which plant growth
example
of cells in the axil of a leaf
becomes isolated from the apical meristem
primordium
IAA,
influence
to restrict
Not
and stolons.
from
is
the plant.
or
removed
to dominate
the growing
evident
bud growth,
axillary
buds in several plant species have been shown to originate
Axillary
from
maintaining
and Roberts
to exert correlative
of rhizomes
have
do
the
tissues
of
a
plant
apical
a profound
only
of lateral
(1987)
in Tamas
of Zea
1968). There is
takes place in cells associated
21
with
the internal
(1983)
Gilbert
have shown that
bundles is the location
with
down
moving
growth
decreasing
the plant
distance
from
the apex.
buds was proposed,
(1972) and Hillman
and Usciati
often
This
is considered
less central
and direct
reviewed
This
tance.
than previously
to a greater
flows and distribution
of transport
As these would include
directed
movement
stituents,
thereby
McIntyre,
consequently
limiting
(PGRs)
regulators
the growth
McIntyre
bud outgrowth
of lateral
hormonal
as being closely controlled
control
and plant nutrients,
for these growth
and Damson,
con-
et al., 1978;
The stimula-
1988).
inhibitors
auxin
as polar
to interpret,
accep-
ions and water.
buds (Leakey
by such compounds
has become more difficult
a greater
of metabolites,
to the apex would bias competition
was regarded
activity
patterns
plant growth
1969,1972,1977;
tion of lateral
molecules towards
on possible
emphasis
and
envisaged.
for many years and is now gaining
is leading
by Guern
to be more complex
The concept that auxin acts at the shoot apex by diverting
it, has been considered
inhi-
of auxin
has shown the role of auxin in
and release of apical dominance
the maintenance
as an effect of
theory
more recent work,
(1984,1986),
effect on the
less pronounced
becoming
Since the direct
or supply.
concentration
of lateral
probably
dominance
carrier.
to have a direct
was thought
the plasma
the vascular
cells sheathing
auxin transport
with
Jacobs and
stem tissue,
sativum
of the presumptive
buds,
of axillary
increasing
bition
in Pisum
of the basal ends of parenchyma
membranes
Auxin
and in cells close to the cambium.
phloem
bud
than when axillary
by auxin
(Rubery,
supply
1987b).
It has also been reported
IAA
auxin
and that
This suggests that
transport
likely
ion extrusion,
and that
the absence of calcium
the calcium
status
to alter both the internal
by inhibitors
inhibited
directly
is
the
of
cell
a change in the direction
concentration
stimulated
normally
and Fuente, 1984), can be prevented
(De Guzman
transport,
that calcium
IAA
of polar
transport.
linked
IAA
and rate of
by
to auxin
movement
distribution
and polar
is
of cal-
22
cium within the cell. These changes could then set off different developmental
effects in the cell (Hepler and Wayne, 1985).
The basic mechanism of apical dominance, therefore, remains unresolved
even though extensive information
is available on specific hormonal effects.
All the classes of major growth substances are known to have at least some
effect on axillary bud growth but their interaction
is still largely undefined.
In general, a hormone regime that enhances vigour of the apical bud enhances
apical dominance, whereas when the apical bud is less vigorous, lateral bud
growth may continue under the influence of growth promotive hormones in
the axillary bud (Tamas, 1987).
Growth
1.4.2
1.4.2.1
Regulator
Triiodobenzoic
in plants
(TIBA)
acid
to be due mainly
to decrease plant
the effects of TIBA
Morris
of polar
sativum)
coleoptile
inhibited
of specific
known
Inhibition
cv.
branching
as TIBA
is
However,
1988).
different
under
the basipetal
of TIBA
of TIBA
and Leopold,
`Paul Richter')
to intact
to the basal cut ends (Saltveit
(Okubo
and Uemoto,
1987a).
as it did in the
auxin transport
auxin
in-
pea seedlings
In Dracaena
1963).
first
the
at
node of tulip
potent
(Rubery,
of IAA,
transport
of the increase in diffusible
treatment
and highly
as phytotropins
decrease
60
in basipetal
per
cent
a
after the application
riana
of a group
transport,
auxin
(Hertel
Zea
of
mays
stem segments,
after TIBA
and Hooley,
to be unpredictable
(1973)
showed that application
et al.
(Pisum
1983).
(Roberts
which
were also reported
in crop lodging,
to a reduction
height
regulator
trees and stimulates
in soybean yields
have been found
is classed as a member
hibitors
plant growth
conditions.
environmental
TIBA
in fruit
Increases
such as soybean.
also known
is a synthetic
branch development
but are thought
Dominance
of Apical
acid
2,3,5-Triiodobenzoic
increases lateral
Control
marginata
occurred
and Fonteno,
has also been reported
flower stalks
1985).
TIBA
(Tulipa
gesne-
also inhibits
23
of hypocotyl
the growth
(2,4-D)
acetic acid
sections of soybean induced by 2,4-dichlorophenoxy-
by as much as 60 per cent (Widholm
Auxin
uptake into tobacco stem segments is stimulated
action
of TIBA,
probably
(Rubery,
from
the
cells
efflux
inhibit
polar
auxin
in this
recognised
of polar
auxin
auxin anion efflux'
(Goldsmith,
at the level of the auxin
and Rubery,
(Depta
different
site
It therefore
within
fashion
polar
a
Consequently,
contradiction
(Thomson
of TIBA
auxins and TIBA
(Davies
work
This
has shown TIBA
for polar
that
transport
auxin
reside on a separate
with the catalytic
associated
to be
it binds to a regulatory
site could
with it, if the proteins
being a non-competitive
system.
subunit
are mobile
in
any transport
that the biological
to resolve this apparent
inhibitor
and also a substrate
This suggests that for the auxin efflux carrier,
have separate specific
and Hooley,
downhill
et al., 1973).
properties
binding
sites and that
translocations,
(Depta
role for auxins in such developmental
(Roberts
mechanism
itself has also been found to be transported
tion of one of the sites allows ligand
both sites prevents
The
the plasma membrane
has
been
two
model
a
site
proposed
of the polar transport
apparent
1956).
acting
carrier
of the efflux carrier or capable of interacting
TIBA
was the first chemical
inhibition
seems likely
site.
of auxin
secretion
1980), with
Further
either permanently
the membrane.
of auxin
to be an ènergetically
within
of the efflux
from the substrate
subunit,
regulatory
1987b).
inhibitor
et al., 1983).
and Skoog,
1977; Rubery,
efflux carrier
1978; Rubery,
a non-competitive
by blocking
is now thought
transport
by the
of a component
1987a) and TIBA
(Niedergang
group
up to threefold
1978).
transport
from the basal ends of cells (Rubery,
1970).
results have also been recorded
1979). Similar
(Davies and Rubery,
for Pisurn sativum
Phytotropins
of inhibition
as a result
and Shaffer,
and Rubery,
of TIBA
whereas occupation
of
1984). It is therefore
are consistent
events as growth
the occupa-
with a critical
dominance
and apical
1988).
24
1.4.2.2
Cytokinins
There
is strong
evidence that
(Tamas,
growth
from
and thidiazuron
are key factors
cytokinins
1987). Application
of cytokinins
to quiescent
a range of species has been shown to stimulate
in soybean
ample
monocotyledonous
(Ali
and Fletcher,
plants
(Hussey,
in vitro (Dalton
polar
auxin
thought
transport
to play an important
Apical
dominance
within
the plant
root-produced
cytokinin,
thereby depriving
Wareing
applied
by regulating
which accumulates
cuttings
Therefore,
growth,
if the apical bud is highly
dominant
It has also been shown (Wang
mainly
to enable axillary
Thidiazuron,
distribution
shoot growth
of IAA
requires
in the shoot apex,
Woolley
and
to the apical stump
of BAP,
buds may be under apical
then the root-derived
to the apical bud, thereby
shoots are able to synthesize cytokinin,
seem that
cytokinin
from the roots can enhance axillary
while cytokinins
dominance.
supply,
previously,
buds. This suggests that cytokinin
transported
in auxin
mul-
to inhibit
leads to a decrease in the amount
are probably
it would
as stated
preferentially
in, the axillary
to, and accumulation
control.
sequently
is known
buds of their supply of cytokinin.
at the base, reaching the axillary
transport
BAP
This assumes that
1975).
the axillary
Solanum
and cormous,
role in apical dominance.
(1972) have shown that the application
of decapitated
for ex-
growth,
of BAP to ryegrass (Lolium
1982), a mechanism,
may be maintained
(Phillips,
buds
Increases in the rate of tillering
1976).
and Dale, 1981,1985).
(Harrison,
their
bud
axillary
1971) and in bulbous
have also been found from the application
tiflorum)
in promoting
and Wareing,
repressed axillary
a redirection
of cytokinin
may be necessary to either
buds to synthesize
cytokinin,
N-phenyl-N'-(1,2,3-thiadiazol-5-yl)
initiate
bud
cytokinins
enhancing
apical
1979) that
while
buds are not. Consupply
axillary
or a decline
bud growth
or
respectively.
urea, was first developed as
a defoliant for cotton Gossipium hirsuturn (Arndt et al., 1976). It is absorbed
by the leaves and causes premature formation of the natural abscission layer
between the stem and petiole (Anon, 1986) and it also provides superior
25
control
of regrowth
The biochemical
fully
not yet
Cytokinin
vegetation
principles
has been detected
of thidiazuron
activity
stimulation
(van
Nieuwkerk
trees
and
oleracea Ìtalica'
group)
Increases in cytokinin
on shoot formation
have been determined
for woody
induce an increase in the activity
of this enzyme suggests that it plays an important
tissues (Chatfield
levels in plant
response from the enzyme.
role in the regulation
and Armstrong,
being virtually
the biological
as a cytokinin-active
inactive,
activity
of BAP
(Takahashi
of thidiazuron
of the most active adenine-type
The biosynthesis
Thidi-
1986).
in inducing
along with
this
other
derivative
(Mok
is very variable,
few
having
a
activities
et
many
equal to
et al., 1978). In all reports
to date
was higher than or comparable
to that
cytokinins.
is promoted
by the synergistic
action
of auxin
(Lau and Yang, 1973) and it has been shown that thidiazuron
and cytokinin
can substitute
that
of ethylene
phenylurea
with
of
oxidase.
of such derivatives
activity
or completely
or greater than that
production
for cytokinin
oxidase
and the specificity
This suggests that thidiazuron
may serve as a substrate
al., 1987). The cytokinin
species
of cytokinin
azuron was found to be as effective as any adenine derivative
is classified
and
(Brassica
brocccli
Wang
1986),
1986;
et al.,
et al. ,
(Mok et al., 1987) and several other test systems.
in callus tissues of Phaseolus vulgaris cv. `Great Northern'
Thidiazuron
of
being less active
1985), analogues
The effects of thidiazuron
bud growth
of axillary
in callus bioassays
where it was found to be more active than
et al., 1982; Mok and Mok,
than the parent compound.
cytokinins
are
understood.
(Mok
cytokinin
1987).
the mode of action of thidiazuron
underlining
Phaseolus lunatus cv. `Kingston'
zeatin
(Gianfanga,
the leaf abscission
after
effectively
(Yip
application
for adenine-type
cytokinins
resulted
tion in mung bean ( Vigna radiata)
findings
in an increase in ethylene
produc-
and cotton
1984a, 1984b, 1985). This is thought
ethylene
earlier
Yang,
1986). This activity
and
of thidiazuron
in enhancing
agrees with
(Gossipium
to play an important
hirsutum)
(Suttle,
role in the abscis-
26
leaves (Anon,
sion of cotton
From these observations
the biological
eral, to the properties
phenomenon
in vitro is the change in cytokinin
azuron
Cytokinin-dependent
on medium
endogenous cytokinin
and Katterman,
by combined
ual buds treated
treatment
and Hooley,
with kinetin
followed
in the lengths of their internodes.
by the cytokinin
induces ethylene
fect on auxin-induced
cv.
on Phaseolus
a phenomenon
that individ-
by the auxin.
of elongation
production
in some plant species (Kang
When
production
ef-
(Lau and Yang, 1973; Yoshii
and
and Burg,
1968) suggested
led to inhibition
bud
of
growth.
(Yeang and Hillman,
et al., 1971;
has a synergistic
of cytokinin
it enhances its production.
vulgaris
axillary
buds
to be due to release from
Work
that
on Pisum
IAA
However,
1981,1982)
stimulated
buds and that inhibitors
sativum
ethy-
more recent work
has shown that
creasing the ethylene level in the apical shoot can lead to development
inhibited
also
of this reaction
(1967) demonstrated
This was thought
and promotion
ethylene
1981), i. e.
lene production
auxin,
by auxin, resembled uninhibited
1971) and the addition
(Burg
with
PGR, could achieve this result.
alone, neither
Sakai and Imaseki,
in vivo, however bud outgrowth
1988). The mechanism
Sachs and Thimann
still remains unclear.
Àlaska'
(Thomas
known to be caused by thidiazuron
are often transitory
in vitro (Roberts
Imaseki,
to an increase in
synergism
can be prolonged
applied
in subse-
1986).
The effects of cytokinins
inhibition
to it.
maintained
autonomy
et al., 1983). This may be linked
synthesis,
Auxin-cytokinin
evident
cytokinin
et
the use of thidi-
after exposure
requirement
displayed
thidiazuron,
containing
(Mok
cytokinins
with
associated
in gen-
conform,
callus of some Phaseolus lunatus genotypes,
(Capelle
quent passages
Auxin
effects of thidiazuron
for the adenine-type
established
An interesting
al., 1987).
of
leading to a loss or decrease in apical dominance.
polar auxin transport,
1.4.2.3
1986) and may play a role in the inhibition
of ethylene production
in-
of the
reverse this
27
(1988)
et al.
also concluded
Dijck
Van
process.
production,
by the synergistic
stimulated
to the culture
medium
of the bromeliad
cultivar
auxin
medium.
In cultures
of Plantago
produced,
in a ratio
and cytokinin
(Barna
ovata
did not significantly
it enhanced
with the outgrowth
genus Vriesea, where axillary
by adding
of auxin
correlated
their quality
and auxin added
(1987) found similar
Pierik
enhanced
addition
effect of cytokinin
in vitro, is positively
buds in some bromeliads.
lateral
that the increase in ethylene
results with
shoot formation
a
was
of 1: 10 to the culture
and Wakhlu,
affect the number
1988), though
shoots
of axillary
increased
and significantly
of
their length.
It is known that ethylene inhibits polar-auxin transport (Morgan et al., 1968)
which, as stated previously, is thought to be a key factor in the maintenance
be
dominance.
Therefore,
the
a means
of
ethylene
could
of apical
production
by which the synergistic interaction of auxin and cytokinin
1.4.2.4
Gibberellins
There are few reports
Studies with
(Furutani
as a result
Gibberellic
of the more efficient
Case, 1965; Palmer and Halsall,
the external
buds
of some plants,
of
Hordeum
(GA3)
enhances apical dominance
acid
sativum
and Zingiber
officinale
1986; Jacobs and Case, 1965; Torrey,
GA3 has been found to stimulate
In contrast,
a possible role in the regula-
indicate
gibberellins
such as Pisum
and Nagao,
bud development
levels and the data that exists is often contradic-
applied
tion of bud development.
in many plants,
between axillary
on the relationship
and endogenous gibberellin
tory.
operates.
release of IAA
the basipetal
1969; Pilet,
application
1973), probably
by the dominant
transport
of IAA
apex,
as
(Jacobs and
1965; Stowe and Yatnaki,
1957).
of GA3 may also enhance the outgrowth
such as Nelumbo
(Kane
Avena
and
cv. `Chinese'
lutea, Hedera helix cv.
et al., 1988; Galston
and Davies,
`Baltica',
1969; Lewnes
and Moser, 1976; Scott et al., 1967).
Kinetin strongly promotes the releaseof axillary buds from apical dominance
ThiSachs
(Catalano
GA3
Hill,
1969;
together
and
when applied
with
and
28
1964). It has, however, been suggested that this may be the action of
mann,
GA3 on the buds after their release from inhibition
apical dominance
As stated previously,
from the apex the bud is situated
decreasing
that
which this effect is increased.
(Liu
1984) and intercalary
Cellular
elongation
is a complex
force
the
of
of turgor
and Jones,
meristems
in newly formed
(Kaufman,
The latter
effect on the irreversible,
or plastic,
1987).
1987;
of the cell wall
but a profound
effect on elasticity
component
process
(Metraux,
the yielding
affects
cells
1965,1967).
the physical
and a change in cell wall metabolism
1977).
from
GA3 can increase
that
involving
mechanism
and GA3 has been shown to have little
al., 1975; Stoddart,
to result
by
be
a
means
of shoots could
and Loy, 1976) and elongation
and Kende,
the further
it can be postulated
Therefore,
It has been established
(Raskin
Stuart
this is thought
and that
of GA3 to cause elongation
the capacity
cell proliferation
becomes less pronounced
or supply of auxin.
concentration
by kinetin.
(Adams
of extensibility
There seems to be no information
linking
et
these
two phenomena.
1.4.2.5
Paclobutrazol
field testing
Extensive
has shown paclobutrazol,
pentan-3-oll,
nyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl)
trum
growth
with
(Lever
to
the
plants
no adverse effects
pounds
retardant
to which
active growth
producing
paclobutrazol
retardants
[(2RS, 3RS)-1-(chlorophe-
reductions
belongs,
demonstrated
to be a broad spec-
in vegetative
growth,
generally
et al., 1982). The group of com-
the triazoles,
(Hedden
far
so
highly
the
most
are
Graebe,
and
1985).
Studies with apple cultivars (Quinlan and Richardson, 1984; Stinchcombe et
have
Tromp,
1987)
1984;
shown that paclobutrazol
al.,
decreases
can cause
in shoot length and leaf size and promote flowering, though the time of flowbeen
has
delayed.
fruit
Enhancement
recorded
of
set
ering was sometimes
but without any effect on yield. Similar results were reported for strawberry
(McArthur
berries
larger
fewer
Eaton,
1987)
were
of
numbers
and
where
29
and yield was unaffected.
produced
al., 1987) and cultivars
1984), plant
growth
(Prunus
of plum
was inhibited
Changes in ear and grain number
ceous crops and turf
and yields
mental plants,
often with enhanced flowering.
and poinsettia
(Euphorbia
ium
longiflorum)
(Jiao
paclobutrazol
(Hebbleth-
and Batch,
to produce
1982).
more compact
These include
1983), Easter lily (Lil-
Rees
1986;
et al.,
et al., 1982),
had been proven for over 60 species (Anon,
Paclobutrazol
is readily
foliage
and it is transported
Consequently
little
and
paclobutrazol
almost
acropetally,
and Shearing,
stem tissue and
roots,
exclusively
the site of action of paclobutrazol.
through
division
areas of cell
by
1984).
in the xylem.
in the leaves
sprayed onto foliage accumulates
reaches the meristematic
PP333
is required
of
through
and
of plant growth
paclobutrazol
up passively
(Hanks
tulip
1985; Lever et al., 1982; Shanks, 1980). By 1984, control
taken
orna-
chrysanthemum
1983; Rees et al., 1982) and many others (Galston
Menhenett,
as-
in gramina-
(Menhenett,
pulcherrima)
reduced.
of canopy structure,
with
has also been used effectively
and Quinlan,
severely
were often
et
have been produced
grasses, after treatment
Paclobutrazol
(Huang
watermelon
(Webster
and modification
et al., 1982; Lever et al. 1982; Shearing
waite
with
domestica)
changes in plant morphology,
with
sociated
In studies
and cell elongation,
To reach these meristeinatic
areas uptake
the roots or exposed stems (Anon,
1984; Lever
et al., 1982).
The primary
role of paclobutrazol
also possess fungicidal
that
the compound
endogenous
interferes
(Lever
directly
increased
with
a variety
chlorophyll
the plants,
The latter
concentration,
may result
as has been recorded
with
the regulation
physiological
altered
it does
of
These are thought
and cytokinins.
of secondary
though
It is also assumed
et al., 1982).
delayed senescence and increased stress tolerance
man et al., 1987).
retardant,
or indirectly
levels of abscisic acid (ABA)
to be closely connected
including
properties
is as a growth
responses
carbohydrate
(Gehlot
status,
Gross1989;
et al.,
from a change in the water use of
in apples following
the application
of pa-
30
(Atkinson,
clobutrazol
1986; Atkinson
and Chauhan,
levels
by
decreased
of water uptake,
caused
conductivity
area, stomatal
duced by the action of paclobutrazol
increased
(Smith
to the explants,
prowith
in in vitro material
of
which leads to better
ex vitro
establishment
et al., 1990).
Commercial
paclobutrazol
form which
is known
has fungicidal
Lurssen,
1987).
sterol
but
impact
of the gibberellin
and Lawrence,
respectively
the action
of paclobutrazol
elongation
and other growth
of gibberellins.
demethylation
of sterol
of ergosterol,
branes, thereby
some fundamental
affecting
associated
Therefore,
cell division
with
on sterol metabolism
and Wiggins,
a vital component
(Dalziel
acid
1987).
prevents
in fungi (Baldwin
prevents the biosynthesis
biosynthesis
oxidase in the oxi-
1985; Graebe,
responses normally
The action of paclobutrazol
1984; Hedden
to ent-kaurenoic
as an anti-gibberellin
of the
or interference
of gibberellin
of ent-kaurene
ent-kaurene
and Graebe,
action
and Lawrence,
1987). The inhibition
1984; Hedden
et al., 1987;
biosynthesis
of gibberellin
precursor
(Lenton
on growth
(Dalziel
the 2S, 3S
form
3R
2R,
the
which
and
are caused by the selective
to be caused by the inhibition
is thought
hibition
little
on the inhibition
1985; Lurssen,
of two enantiomers,
stem elongation
These phenomena
metabolism,
and Graebe,
dation
is a racemic mixture
to inhibit
activity
two enantiomers
with
are often
It has also been shown that these changes confer resistance
chrysanthemum.
to desiccation
that
These changes together
on plants.
wax, have been demonstrated
epicuticular
with decreases in leaf
associated
size and density,
and root
may be
This
1987).
and
the action
involves in1984) which
fungal
cell memof
of these membranes.
property
The biosynthetic pathways of sterol and gibberellin have features in common
has
been
levels
to
the
reported
of plant tissues
reduce
sterol
and paclobutrazol
(Baldwin
Wiggins,
and
1984). However, the enantiomers are not specific
inhibitors of the two pathways. Consequently, a third mode of action, namely
changes in endogenous ABA levels, is implicated
to explain the observed
effect on water consumption and stomatal movement.
31
1.4.2.6
Ethylene and abscisic acid
Although
they
these growth
regulators
have been implicated
in the mechanisms
interaction
their
sequently,
have not been used in the present study,
with
discussed
dominance
apical
will
previously.
Con-
be considered
here
briefly.
Ethylene
There is considerable
dominance,
(Roberts
though
ethylene
et al., 1968).
Pretreatment
in their individual
of whole
after the removal of the ethylene
level
the
may reduce
of auxin carriers
regulating
Abscisic
gene expression
the ABA
treated
(Morgan
(Burg
hours
and
1968) appears to be
with
recovery
occurring
1973). This suggests that ethylene
in the plasma membrane,
or intra-cellular
protein
that axillary
bud growth
possibly
by
movement.
content
is correlated
buds.
If the shoot is decapitated,
the
of
or otherwise
to release the buds from
the ABA
plants (Tucker,
content
from inhibition
inhibition,
(Tamas,
(Tucker,
1987).
of the axillary
1976). ABA treatment
whereas the application
inhibition
polar
inhibition
is seen to decrease rapidly
tomato,
signal
acid
Some workers have reported
with
and Mullins,
to be inhibited,
(Beyer,
sensitivity
for several
plants
1967) or excised segments (Osborne
auxin transport
as a correlative
can severely inhibit
pretreatment
with species differing
necessary for polar
in
also
play
a
role
may
apical
its gaseous nature makes it unlikely
and Hooley, 1988). Ethylene
auxin transport,
Burg,
evidence that
of ABA
the ABA
In non-branching
of axillary
to the shoot
with
of the buds
mutants
of
buds is much higher than in normal
buds inhibits
their growth,
apex releases axillary
1977). This response is thought
bud
growth,
of apical
content
the consequent
buds
to be caused by the
loss of its dominance
effect.
There are no indications that ABA functions as the correlative signal released
by shoot apices. The available evidence suggests that ABA acts within the
32
buds as a secondary
axillary
inant
plants
apex.
Decapitation
factor,
lowered
but this was prevented
(Tucker,
1978).
maintain
a high level of ABA
the effect of ABA
It therefore
whose level can be regulated
ABA
levels in axillary
by the application
appears,
that
in the axillary
may be modified
of IAA
the polar
buds.
by the dom-
buds of Phaseolus
to the cut stump
transport
of IAA
It is also thought,
by other plant growth
can
that
(Tamar,
substances
1987).
33
Chapter
MATERIALS
2:
AND
GENERAL
METHODS
2.1
SOURCE
OF PLANT
Plants of four hybrid
and a 'Butterfly
type',
cultivars
MATERIAL
of Alstroemeria,
were supplied
Alstroemeria
growth characteristics.
groups and, therefore,
for Alstroerneria
2.2
GROUP
The four cultivars
together
(Spal-
to as `Butter-
into groups on the basis of their
chosen originate
they exhibit
Èleanor',
Company
type' will be referred
are often divided
cultivars
`Parade',
by Parigo Horticultural
ding, U. K. ). In this thesis the `Butterfly
fly'.
`Valiant',
from four different
a range of growth
characteristics
in vivo and in vitro.
cultivars
BACKGROUNDS
AND
GENERAL
CHARACTERISTICS
In this thesis, aerial shoots are referred to as shoots.
the rights of the breeder the species used in the following
To protect
programmes
supplied
will
be referred
to as a, 3, y and b.
This
breeding
information
was
Co..
" Species a, a native of cool plains and mountain foothills, including pine
forest
frost-free.
is
Nothofagus
the
where
climate
generally
and
" Species ý, a native of frost-free areas of the Pacific coast, where a cool
dry.
it
is
to
summers
and
often
warm
spring usually gives way
" Species -y, a native
a shade loving
of the northern
South
America
most regions of
and
plant.
34
" Species b, a native of the Pacific coastal regions.
All of these parent species were collected from Chile, though they are not all
restricted to this country.
Group
A (sterile
triploids)
Species a9x
Species Qd
Hybrid
19x
Species a cj
cv. Èleanor'
This group performs
cultivars
with
hybrid
when established
Generally
Group
well in vitro but shows poor establishment
1 as the female parent
the rhizome
grow well in vitro.
is large and the shoots
no flowers are produced
are tall
in vivo. All
However,
and strong.
in the winter.
B (sterile triploids)
Species ß9x
Species ry c
Hybrid
29x
Species ad
cv. `Carmen'
Radiation
Mutation
cv. `Valiant'
35
This group multiplies
in vitro but possesses good growth in vivo.
poorly
However, the rhizome is small and weak and the shoots, though reasonably
tall, are also weak. There is some flower production through the winter.
Group
C (sterile triploids)
These are products of the same programme as that for group B. The cultivar
chosen from this group was `Parade'.
Growth
in vitro is relatively
poor,
whereas in vivo it is good. However, the rhizome, though slow to extend,
is not as small and weak as that in group B and shoot growth is tall and
strong. The stems remain vegetative in winter.
Group
D (fertile diploids)
Species S9x
Species ry
cv. `Butterfly
The growth
of these cultivars
they are easy to establish
is quite dissimilar
different
it shorter
texture
types'
in vitro is generally
and grow vigorously.
very poor, whereas in vivo
Morphologically
to the others as the stems are shorter,
and the close positioning
and more compact.
Flowering
this group
the leaves have a
of the shoots on the rhizome makes
is generally
confined
to late summer
and autumn.
The number
markedly
and distribution
between
the four cultivars
Èleanor'
the groups.
of the roots and tubers on the rhizome
Figure
chosen. It can be seen, therefore,
shows poor establishment,
good establishment,
2.1 shows the rhizome
whereas the cultivar
the converse being true in vitro.
and `Parade' are intermediates
that
rootstocks
of
in vivo the cultivar
`Butterfly'
The cultivars
between the two cultivars
varies
Èleanor'
shows
`Valiant'
`Butand
terfly'.
36
Figure 2.1: The rhizome rootstocks of the four cultivars chosen. Each rhiB=
basal
`Valiant',
internodes.
A=
ten
zome segment consists of
enlarged
`Parade', C= 'Butterfly' and D= Èleanor'. Bar =5 cm
37
2.3
2.3.1
GENERAL
CULTURAL
CONDITIONS
In Vivo
At the beginning
of each experiment
lifted plant clumps for splitting
had been produced
to three litre
material
pots were transferred
is produced
nitrogen,
phosphorus
M2 compost.
This compost
they were supported
tall and
with split canes and string.
to their experimental
feed of Maxicrop
with
(Maxicrop
The
and after approximately
positions
from a seaweed extract
and potassium
level,
nutrient
1987). As the plants grew fairly
12 weeks the plants were given a liquid
fertilizer
and small plants were transferred
Fisons Levington
with a pH range of 5.3 to 6.0 (Anon,
of ap-
consisting
grade of peat and has a medium
consists of a medium-coarse
the stems were fragile,
These `splits',
basal internodes,
pots containing
was supplied
as freshly
by hand, or as small plants in 9 cm pots that
from micro propagation.
10 enlarged
proximately
plant
Triple
(1: 1000). This
small quantities
International
of added
Limited,
per-
sonal communication).
These were the standard cultural conditions for all in vivo experiments, conditions specific to each experiment are described in the relevant sections.
2.3.2
In Vitro
Rhizome
cultures
were maintained
of the four cultivars,
as a multiplying
for use in experiments.
on the plant,
which
stock cultures
were subcultured
15°C, a 12/12 hour (day/night)
difficult
daylength
underground
when initiating.
Color
cycle (Parigo
Horticultural
of approximately
29,65-80
provided
cent tubes.
Any changes to these conditions
All cultures,
was removed
The
every four or five weeks and maintained
µE m-2s-1),
sections.
are all situated
to disinfect
and an irradiance
by Philips
material
was necessary as the meristems
of Alstroemneria
makes them
Co.,
from which
stock,
A stock of material
used in the micropropagation
personal communication)
supplied
stock and experimental,
W, warm
described
are
at
Co.,
20 W M-2 (120
white
fluores-
in the relevant
Alstroemeria
on
were grown
38
production
(Parigo
medium
Horticultural
however,
some experiments,
different
Co., personal
In
communication).
of PGRs were added to
combinations
this medium.
Unless otherwise
This included
stated,
rhizomes
internodes,
node.
the roots
with
At subculturing
before continuing
subculturing
explant'
removed
the explants
through
occurred
2.4
Horticultural
first
the
the
shoots excised above
and
were returned
MEDIA
were carried
if no change had
to do so.
MS
based
revised medium
on
was
medium
production
B). It also contained
(Appendix
agar
Stock solutions
of the medium
were stored frozen.
stock solutions
To prepare
were mixed
4 mg 1-1 BAP, unless stated otherwise.
(Appendices
of the vitamins
culture
media,
Distilled
and the medium
was then adjusted
water
and hydrochloric
was added to obtain
regulators
(Sigma)
agar
of
volumes
(Appendix
the required
to a pH of 5.8 using solutions
volume
of potas-
production
dissolved
being
l-1
8g
at
)
(5
for
i.
ten
104°C
minutes.
p.
s.
at
into
and amino acids which
acid. In this study Alstroemeria
was always used semi-solid,
pensed in 25 ml aliquots
A and B) were stored
the appropriate
and sucrose and growth
C) were added.
(Ap-
and sucrose and reduced
of vitamins
constituents
in the dark at 5°C, with the exception
by autoclaving
that
communication)
A),
with elevated concentrations
pendix
medium
after which
PREPARATION
The Alstroemeria
sium hydroxide
condition
been
had
it
reported
cycles, as
this time, then it was unlikely
within
to this initial
All of the in vitro experiments
Co., personal
basal
of three enlarged
consisted
out for 12 weeks only, i. e. three subculture
(Parigo
For
them to fresh medium.
the next four weeks of the experiment,
again occur.
would
some of the
removing
,
culturing
and transferring
a `standard
work,
was subcultured
for subsequent
older part of the rhizome explant
experimental
four
weeks.
every
first
the
the
the
node,
roots and
shoots above
all of
removing
lateral
separating
in vitro material
The medium
diswas
140 ml screw top glass jars and sterilized
by
39
j5
4This
r
(15
121°C
at
p. s.i.
autoclaving
jar type and medium
volume were used
in all of the in vitro experiments.
Due to the thermolabile
had been sterilized.
sterilized
nature of GA3i it had to be added after the medium
Consequently,
Sartorius
with
Minisart
and added to the cooling
previously
sterilized
DATA
2.5
All
pH adjusted
NML
AND
designs were randomised
root
blocks,
and the complete
system
were repeated
to produce
the details
with
The in vivo experiments
(ii)
and
and tubers
rhizomes
into
ANALYSIS
of either four or eight weeks by recording
intervals
aseptically
filters,
jars.
culture
designs being given in each section.
lateral
0.2 µm pore size disposable
This was then dispensed
medium.
RECORDING
experimental
of GA3 were filter
solutions
with
through
replication
were assessed at
(i) the numbers of shoots,
the dry weights
rhizome
of the
laterals.
time.
of the shoots,
whole
These experiments
The repetitions
were
performed
over the same period one year later, to prevent any seasonal effects
occurring.
The two data sets were then combined
each parameter
per plant.
at subculturing
recorded.
eighth
The numbers
and twelfth
of shoots,
lateral
that
media or environments
sets were combined
of the experiment,
the explants
during
were becoming
the initial
weeks from
producing
material.
the start
of
and roots were
rhizomes
was not used, as
accustomed
to the new
four weeks. The second and third
to be repeats
as one data set, as they were considered
a mean value for each parameter
The means of the numbers produced
using all non-infected
were assessed
cultures
However, the first set of data for each experiment
it was considered
jar.
In the in vitro experiments
fourth,
the
on
the experiments.
to give a mean value for
for each treatment
Data presented
per culture
were calculated
in figures and tables are the
means per explant.
When the data consisted of scores or counts, it was considered to be discontinuous and was analysed by fitting
binomial
linear
or
a
model with
a
40
Poisson distribution
deviance.
From
These are both considered
of the errors.
these analyses,
(p) could be worked
probability
data, for example
of samples, were subjected
weights
Genstat
the
using
performed
cultural
probability
Trust,
considered
significant
for p=0.05
computing
Experimental
Continuous
to an analysis
(p) were produced.
5 statistical
1988, Rothamsted
out.
error of the difference
for
from
the standard
which
values
ance,
(sed) and the statistical
(x2) were produced,
values for chi-square
from which the statistical
as analyses of
All
of vari-
of the means
analyses were
(Lawes
Agripackage
Station).
Differences
or less.
As this study was principally
concerned with the effects of the treatments
the cultivars
differences
and substantial
been demonstrated
(Section
sponse between cultivars
the experiment
were
between the cultivars
2.2), no analyses of the variation
in experiments
designed to quantify
have already
in growth
be
An
exception
made.
will
the differences apparent
on
re-
to this is
in vitro (Section
5.3).
41
Chapter
THE
3:
EFFECT
TEMPERATURE,
DAYLENGTH
OF
IRRADIANCE
AND
ON RHIZOME
GROWTH
IN
VIVO
3.1
INTRODUCTION
Of the limited
number
of papers published
factors on the growth
vironmental
of Alstroemeria
specific reference to how these factors
Consequently,
rhizomes
experiments
influence
were carried
the environmental
in vivo, only a few make
the growth
of the rhizome.
out to study the growth
irradiance
across ranges of temperature,
In each experiment,
on the effects of changes in en-
response of
and daylength,
in vivo.
factors were constant with the ex-
ception of the single variable being studied.
All of the experiments were
carried out in the period between autumn to spring in order to avoid extremes of temperature in the glasshouses. Suitable plant material was also
more available in the autumn.
3.2
3.2.1
THE
EFFECT
Materials
OF TEMPERATURE
and Methods
Potted `split' plant material
(Section 2.3.1) of the cultivars
and `Butterfly'
were grown in three controlled
set at constant
temperatures
of 8,13
were set on a 12/12 hour (day/night)
u. kcm
`Valiant',
environment
`Parade'
Saxcil cabinets,
and 18°C, for 24 weeks. The cabinets
daylength
cycle, lighting
being supplied
by Philips Color 21(white fluorescent tubes 65-80 W, that gave approximately
42
28 W M-2 (180 µE m-2s-1)
screen.
Growth
analysis
the 24 week period,
treatment
repeated
tion 2.5), with
from behind
was carried
at which
were removed
subsequently
of light,
times
a white translucent
out at intervals
four plants
of eight weeks, over
from
each
experiment
was
and the data analysed
(Sec-
of each cultivar
and assessed (Section
This
2.5).
using new plant material
design of 3 temperatures
an experimental
perspex
with
x8 replicates,
4 assessments for each cultivar.
3.2.2
Results
had a greater
Temperature
effect on the dry weight
numbers of lateral
rhizomes,
These differences
were generally
cultivars
weights
performed
poorly,
producing
13 and 18°C tended to be small.
a lesser extent
This trend
creasing
by week 24.
apparent
Differences
the temperature
new growth
from `splits'
nificant
for the cultivar
initially
but within
generally
made during
in more plants
and subsequently
`Valiant'
(Figure
but suddenly
base. Closer examination
the tubers
in the cultivar
at
at 18°C
`Parade'
dying.
3.2).
this experiment
failing
and to
collapsed
that
to establish
Often,
in-
viable
This was particularly
a few weeks they had collapsed
did not wilt
had not produced
results
between growth
3.1).
the observation
supports
and lower dry
There was often a decline in growth
at 13°C, especially
(Figure
`Valiant'
At 8°C all of the
fewer parts
generally
on the
than
(Tables 3.1 and 3.2).
than at the other two temperatures.
to levels lower than that
of plants
sig-
some shoots emerged
and died.
The shoots
due to deterioration
at their
revealed that the rhizome segments of these plants
any new roots and had completely
on these dead plants
were still
intact
degenerated.
Some of
and were unchanged
from
when they were planted.
Time to flowering, although not quantified, was retarded for all cultivars at
8°C, with a similar time to flowering for the plants in the 13 and 18°C teinperature
regimes.
Some material
of all the cultivars
at all the temperatures
43
Table 3.1: The effect of temperature
on the numbers of lateral rhizomes, tubers and shoots produced by the cultivars `Valiant', `Parade' and `Butterfly'
Cultivar
Temperature
(°C)
8
`Valiant'
`Parade'
`Butterfly'
Period of growth (weeks)
24
08
16
Number of lateral rhizomes
1.0
0.0
0.0
0.4
13
0.0
0.3
1.3
3.1
18
0.0
0.0
4.0
5.0
8
13
18
8
13
18
0.0
0.0
0.0
not significant
0.8
0.6
0.2
1.5
0.0
2.3
1.6
5.9
2.0
0.0
0.0
0.0
not significant
2.6
2.1
2.0
4.1
5.0
3.4
4.8
7.3
6.2
not significant
`Valiant'
'Parade'
`Butterfly'
8
13
18
Number of tubers
8.1
4.9
4.8
4.4
8.9
31.0
5.6
4.5
8.5
33.0
4.3
4.1
8
13
18
0.8
1.5
0.7
not significant
0.4
2.9
2.7
6.0
3.8
2.7
4.3
21.0
13.1
3.3
3.7
3.7
not significant
2.9
5.3
4.6
10.0
2.8
19.1
7.8
38.0
40.0
8
13
18
p=0.05
Number of shoots
`Valiant'
`Parade'
`Butterfly'
8
13
0.0
0.0
2.0
2.6
2.8
5.0
18
0.0
2.3
9.8
8
13
18
8
13
18
5.9
16.3
19.0
0.0
0.0
0.0
not significant
3.1
2.1
2.5
4.1
2.8
6.2
7.3
15.0
9.5
0.0
0.0
0.0
not significant
7.8
3.6
6.5
13.8
8.3
19.5
15.9
29.5
28.1
not significant
44
Table 3.2: The effect of temperature on the dry weights of rhizome, roots
`Butterfly'
`Parade'
by
`Valiant',
the
and
cultivars
and shoots produced
Cultivar
Temperature
(°C)
'Valiant'
8
13
18
`Parade'
8
13
18
24
16
08
Rhizome dry weight (g)
0.62
0.44
0.29
1.04
1.11
0.59
0.34
1.04
0.91
1.33
0.31
1.04
d.
f.
sed=0.12,
=63
p=0.05,
0.70
1.34
0.56
0.92
2.20
1.14
0.42
0.92
1.30
1.06
0.90
0.92
not significant
`Butterfly'
8
0.33
0.38
0.56
0.99
13
0.33
0.42
1.01
2.21
18
0.33
0.40
1.13
3.38
d.
f.
sed=0.15,
=63
p=0.001,
8
1.76
dry weight (g)
3.24
4.82
2.05
13
18
1.76
1.76
3.15
2.28
Root
`Valiant'
`Parade'
`Butterfly'
4.85
6.07
16.91
11.32
not significant
4.14
1.47
6.33
8.07
24.99
8
2.61
13
2.61
18
2.61
4.31
8
13
4.50
15.26
p=0.01, sed=2.17, d. f. =63
3.02
4.15
1.68
2.45
9.23
30.77
3.08
2.45
18
2.45
2.19
P=0.001.
'Valiant'
8
13
18
`Parade'
8
13
18
`Butterfly'
8
13
18
1.75
8.32
sed=2.76,
38.33
d. f. =63
Shoot dry weight (g)
0.80
0.19
0.07
0.00
7.03
0.10
1.89
0.00
20.23
0.07
4.74
0.00
p=0.001, sed=1.60, d. f. =63
0.75
5.38
0.13
0.00
0.24
4.85
40.27
0.00
18.33
11.30
0.00
0.56
p=0.01, sed=3.65, d. f. =63
5.34
0.00
0.25
1.66
20.89
0.00
1.36
4.60
19.89
0.00
2.27
13.80
p=0.001, sed=2.46, d. f. =63
45
{
1
{
ý
".
ý'
(A) and `Valiant' (B) after 24
Figure 3.1: Growth of the cultivars `Butterfly'
Left to right: 8,13 and 18°C. Scale
weeks at three different temperatures.
= 1m
46
50
40
30
20
10
0
'Valiant'
8 °C 0
`Valiant'
`Parade'
`Butterfly'
'Parade'
Cultivar
13 °C ®18
`Butterfly
°C
P=0.01
not significant
p=0.05
Figure 3.2: The effect of temperature
`Valiant', `Parade' and `Butterfly'
on plant deaths in the cultivars
47
had
buds
developing
flower
in
or
was
`Butterfly'
the cultivar
3.3
3.3.1
OF IRRADIANCE
and Methods
Materials
Small
(Section
plants
2.3.1)
`Valiant'
of the cultivars
and Èleanor'
grown for 20 weeks in a glasshouse, set at a mean daily temperature
(day/night)
hour
12/12
and a
produced
daylength
by high pressure sodium
lamps (G. E. C. RC HPS/U
ments of 60 and 50 per cent irradiance
graded shade netting,
protection
were produced
were
of 15°C
extension
was
2 Solarcolour,
of light.
Environ-
by covering the plants
(Rokolene
40 and 50 per cent shade respectively
S. and E. Strauss Ltd. ), supported
Roko Containers,
netting,
cycle. The daylength
28 W m-2 (88 µE m-2s-1)
400 W), that gave approximately
with
of
seemed to be least affected by temperature.
EFFECT
THE
by week 16. The time to flowering
on
a metal frame.
Two plants
analysis
of each cultivar
(Section
2.5) at intervals
in the different
was monitored
no significant
change in the temperature
Irradiance
was also monitored
alterations
in the properties
data analysed
4 replicates,
(Section
with
irradiance
repeated
treatments.
due to
no changes occurred
during
of the netting
2.5), with
for growth
regimes to ensure that
in the different
occurred
to ensure that
was subsequently
were removed
of four weeks, over the 20 week period.
Temperature
The experiment
3.3.2
from each treatment,
the experimental
using new plant material
an experimental
period.
and the
design of 3 irradiances
x
6 assessments for each cultivar.
Results
There were no losses of plants following
Overall,
of lateral
irradiance
rhizomes,
had a greater
transfer
effect on dry weight
tubers and shoots produced
trends of decrease in number
to the three litre containers.
than on the number
(Tables 3.3 and 3.4). Some
and dry weight with decreasing irradiance
evident but they were generally
only apparent
by weeks 16 or 20. Growth
were
was
48
always best at 100 per cent irradiance,
differences
depending
Of the cultivars
studied.
studied,
to changes in irradiance
visible difference
little
Time to flowering,
on the cultivar
and the growth
Èleanor'
received.
across the range of irradiances
were evident
at all irradiances
were present in the 100 per cent irradiance
3.4
3.4.1
THE
EFFECT
Materials
(Section
grown
for 20 weeks in a glasshouse
2.3.1)
blackout
automated
supplementary
The supplementary
Two
analysis
(Section
not producing
vironments.
lighting
were
and Èleanor'
were
x4
from
were taken
for
set
a maximum
extension
daylength
to 12 and
of 8 hours,
16 hours.
7.5 W m-2 (5 µE m-2s-1)
each treatment
was
were removed
for growth
of four weeks, over the 20 week period.
to ensure that
heating
experiment
replicates,
tempera-
bulbs.
any significant
This
at a mean daily
hours
8,12
16
were achieved
and
of
of approximately
2.5) at intervals
readings
`Valiant'
maintained
the tungsten
effects in the extended
was subsequently
(Section
data
the
analysed
and
3 daylengths
Both cultivars
by week 12.
for daylength
lighting
of each cultivar
Temperature
material
curtains,
by 100 W tungsten
plants
by week 8, whereas
but
time,
this
more
at
treatment.
of the cultivars
15°C. Daylengths
ture of approximately
provided
`Valiant'
and Methods
plants
with
for both of
OF DAYLENGTH
Small
with
3.3).
Buds and some flowers
studied.
for the cultivar
treatments
(Figure
a cultivar
within
only buds were developing
in flower in all the irradiance
being
there was
appeared to be similar
not quantified,
Èleanor',
parameter
At the end of the experiment
the cultivars
for the cultivar
levels were
be
to
the more sensitive
seemed
between the treatments
although
However,
of the cultivar.
between the 60 and 50 per cent irradiance
perceived
not consistent,
regardless
repeated
lights
daylength
were
en-
using new plant
2.5), with an experimental
design of
with 6 assessments for each cultivar.
49
Table 3.3: The effect of irradiance on the numbers of lateral rhizomes,
and shoots produced by the cultivars `Valiant' and Èleanor'
Cultivar
`Valiant'
Èleanor'
Irradiance
(%)
0
16
48
12
tubers
20
100
0.0
0.0
4.8
5.0
5.3
5.0
60
0.0
0.3
2.3
1.8
3.5
4.5
50
0.0
0.8
0.5
2.3
1.8
2.3
2.0
6.3
100
0.1
1.3
p=0.001
2.0
1.5
60
0.1
0.0
0.0
0.3
0.8
1.3
50
0.1
0.5
0.0
0.5
1.0
1.8
not significant
Number of tubers
`Valiant'
Èleanor'
100
15.7
14.0
15.0
19.5
49.5
67.3
60
50
15.7
15.5
18.0
25.8
28.3
39.8
15.7
18.3
14.0
26.3
23.5
33.8
15.8
27.0
100
5.5
not significant
8.7
8.8
12.3
60
5.5
8.5
10.5
11.5
10.3
21.3
50
5.5
6.8
8.5
9.0
12.0
18.5
Number of shoots
8.8 13.0 18.8
3.8
6.5 10.5 12.0
3.5
9.0
9.5 13.8
5.0
29.0
18.0
12.5
not significant
`Valiant'
100
60
50
3.3
3.3
3.3
not significant
Èleanor'
100
3.5
5.3
8.5
10.8
11.8
60
50
3.5
3.5
5.5
6.3
6.0
7.5
10.5
8.5
10.3
11.8
14.0
11.8
11.5
not significant
50
Table 3.4: The effect of irradiance on the dry weights of lateral rhizomes,
roots and shoots produced by the cultivars `Valiant' and Èleanor'
Cultivar
`Valiant'
Èleanor'
0.66
0.66
0.66
48
12
16
0.57
1.38
2.25
1.05
0.76
0.81
1.37
1.49
0.67
1.01
1.02
1.18
3.69
2.29
1.82
100
0.27
p=0.001, sed=0.16, d. f. =45
0.45
0.59
1.14
1.29
1.91
60
0.27
0.36
0.46
0.80
1.36
2.04
50
0.27
0.36
0.41
0.45
0.91
1.01
Irradiance
(%)
100
60
50
0
p=0.001,
`Valiant'
100
60
50
3.98
3.98
3.98
20
d. f. =45
sed=0.15,
Root dry weight (g)
7.99 19.65
4.82
4.45
9.31 12.31
5.02
4.54
8.00
6.33
8.84
4.05
25.26
15.90
17.51
not significant
Èleanor'
100
60
50
1.53
1.53
1.53
2.90
2.50
2.51
p=0.05,
3.21
2.92
2.62
6.71
4.29
2.88
sed=1.43,
`Valiant'
Èleanor'
0.86
0.86
0.86
2.64
1.79
2.02
100
1.09
2.96
60
50
1.09
1.09
2.76
3.56
5.80
5.82
6.45
22.54
17.44
15.30
not significant
40.00
10.11
23.29
6.72
6.37
15.67
15.19
7.66
d. f. =45
Shoot dry weight
100
60
50
10.57
11.96
5.06
17.61
(g)
37.65
32.70
25.97
54.95
53.18
43.96
62.94
88.72
47.89
44.04
61.82
56.75
p=0.001, sed=2.69, d. f. =45
51
ýý
3.3: Growth of the cultivars
weeks at three different irradiances.
= 1m
Figure
(B)
'Eleanor'
after 20
and
Left to right: 50,60 and 100 %. Scale
'Valiant'
(A)
52
3.4.2
Results
The daylength
treatments
the two cultivars,
Increasing
of lateral
rhizomes
daylength
tem for the cultivar
parameters
of tubers produced
Èleanor'.
differences
for
(Table
3.5
studied
decrease in the number
caused a significant
by the cultivar
produced
increase in the number
Time
a few significant
only
across the range of growth
and 3.6).
evident
produced
`Valiant'
and also a significant
and the dry weight of the root sys-
Some other differences were possibly
becoming
by weeks 16 or 20.
to flowering
daylength.
All
plants
For the cultivar
the daylength
daylength.
`Valiant'
was not
in all of the treatments
Èleanor',
flowering
markedly
affected
by
buds
by
week 4.
possessed
was delayed by four to eight weeks in
of 12 hours and by eight
to twelve
weeks in the eight hour
By week 16 there were buds or flowers in all of the treatments.
In the eight
noticeably
in the cultivar
hours daylength
thicker
with
smaller
regime,
shoots
of the cultivar
Èleanor'
leaves and they were approximately
height of shoots in the other two treatments
It was not possible to produce photographs
(Figure
were
half the
3.4).
of the rhizome rootstocks to
(Figures
those
the
the
the
complement
of
whole plants at
end of
experiments
3.1,3.3 and 3.4), due to the congested nature of the roots and rhizome and
the damage that they consequently suffered when being removed and cleaned
of compost.
3.5
DISCUSSION
As expected, plants of the three cultivars grown at 8°C exhibited the slowest
growth rates. It is well established that the metabolism and growth rate of
plants are positively correlated with temperature.
It has also been considered
that the decline in shoot production at low temperatures is a change towards
a period of dormancy for Alstroerneria,
(Healy and Wilkins,
1985; Sims,
1985). Commercially, it is known that the growth of Alstroemeria is inhibited
if temperatures
are allowed to fall too low and many of the new hybrid
53
Table 3.5: The effect of daylength on the numbers of lateral rhizomes,
and shoots produced by the cultivars `Valiant' and Èleanor'
Cultivar
`Valiant'
Èleanor'
Daylength
(hours)
0
16
12
48
tubers
20
8
0.0
0.0
2.0
3.8
4.0
5.30
12
0.0
0.0
1.0
1.0
2.0
2.50
16
0.0
0.8
1.0
1.3
1.0
0.60
0.8
1.3
8
0.1
0.0
p=0.05
0.8
0.0
12
0.1
0.3
0.5
1.5
1.8
1.5
16
0.1
0.0
1.3
0.8
0.8
3.5
of tubers
21.3
23.0
31.0
not significant
Number
`Valiant'
8
10.7
15.0
17.0
12
10.7
14.8
17.5
16.3
20.5
29.3
16
10.7
17.8
19.3
24.0
28.5
27.0
not significant
Èleanor'
8
5.5
7.0
6.5
10.3
10.0
13.8
12
5.5
9.3
9.5
10.8
13.5
13.8
16
5.5
10.5
11.3
20.5
18.8
36.3
p=0.05
Number of shoots
4.8
3.5
6.0
5.0
11.3
7.0
13.5
9.5
19.3
12
3.3
3.3
16
3.3
5.0
5.5
7.0
9.8
10.5
8
3.5
not significant
8.3
5.3
4.3
10.5
14.5
12
3.5
5.5
6.3
16
3.5
5.0
5.3
11.3
8.0
11.3
12.8
8
`Valiant'
Èleanor'
9.5
6.3
12.3
not significant
54
3.6: The effect of daylength on the dry weights of lateral rhizomes,
roots and shoots produced by the cultivars `Valiant' and Èleanor'
Table
Cultivar
`Valiant'
Èleanor'
0.66
0.66
0.66
48
12
16
0.97
1.39
0.63
0.86
0.91
0.79
0.56
0.74
0.95
0.93
0.67
0.95
2.03
1.12
1.28
8
12
0.27
0.27
not significant
0.58
0.31
0.34
0.41
0.33
0.34
1.28
0.71
1.22
0.83
16
0.27
0.33
0.63
0.75
1.36
Daylength
(hours)
8
12
16
0
0.39
20
not significant
Root
`Valiant'
Èleanor'
`Valiant'
8
12
16
8
12
16
8
12
16
dry weight
(g)
3.98
3.98
3.98
3.48
3.87
4.46
7.57
6.51
9.37
9.06
8.18
10.31
1.53
1.53
1.53
not significant
5.03
3.05
1.80
1.96
4.58
3.14
2.15
2.64
9.31
2.12
2.77
5.68
p=0.05, sed=1.60, d. f. =45
5.94
5.47
19.86
0.86
0.86
0.86
4.81
4.57
4.34
5.01
5.13
8.58
Shoot dry weight (g)
3.98 10.55 17.64
1.46
7.69 17.02
3.97
1.47
3.18
1.25
4.64 14.23
34.52
23.77
23.44
not significant
Èleanor'
8
1.09
1.99
2.48
10.47
19.67
40.01
12
1.09
2.55
5.06
11.34
19.48
34.30
16
1.09
2.96
5.83
10.17
16.23
24.16
not significant
55
Figure
3.4: Growth of the cultivars
weeks at three different daylengths.
lm
=
`Valiant' (A) and 'Eleanor' (B) after 20
Left to right: 8,12 and 16 hours. Scale
56
(Parigo
known
be
frost
Horticultural
to
to
sensitive
cultivars are
Co., personal
communication).
can also occur in Alstroemeria
Dormancy
(Dambre,
1987; Powell and Bunt,
20°C in northern
temperate
between
for example
1984,1986),
(Parigo
zones of the world
for the cultivars
(Fortanier
of Nerine flexuosa
flowering
20°C are known
growth
(Kim
30°C
exceeding
of lateral
maximize
)
(Mitchell,
spp.
lateral
1953a, 1953b).
(Section
The
at temperatures
production
has
is an important
for the growth
in rye-
is generally
As Alstroemeria
1.2.4), a temperature
production
rhizome
which
temperature
to decline
decrease
in
the rate of tillering
a
to produce
vegetatively
production,
spears is also known
above
(Rees,
1972).
state
et al., 1989). For two of the three cultivars,
also been demonstrated
propagated
to be too high for good
High
lower
13°C.
temperature
°C
18
than
was
at
at
rhizomes
(Lolium
grass
Similar
et al., 1979), and temperatures
to keep Iris bulbs in a vegetative
rate of Asparagus
indi-
is raised
and `Parade'.
`Valiant'
i. e. 17 to 21°C, are also considered
temperatures,
Co.,
experiment
cates that the increase in growth rate slows down as the temperature
from 13 to 18°C, especially
18 and
Horticultural
The data from the temperature
communication).
personal
high
too
are
when temperatures
does
that
not
regime
will lead to a lower level of new plant
commercial
Alstroemeria
of
An optimum
consideration.
be
between
to
would appear
13
and 18°C.
Many
of the results
obtained
herent in Alstroemeria,
which
high or low temperature
the cultivars
stroemeria,
supports
may be linked
with
help the plant
to overcome
stress.
this theory.
The increase in tuber
Dambre
storage organs are produced
above ground
parts
survival
periods
number
(1987) has reported
as temperatures
die down and the plant
mechanisms
in-
of either
in two of
that
in Al-
rise, i. e. before the
becomes dormant,
in order to
survive hot dry summers.
A possible reason for the rapid decline in plant growth at 18°C may have
been the use of constant temperature regimes, consequently the plants were
57
not subjected
to cooler
tive habitats.
Therefore,
temperature
in the early growth
constant
yet, if the temperature
number
to extremes
type of effect has been indicated
best
growth
where
officinale)
fluctuating
at 27.5°C, whereas
at a
temper-
et al., 1978). The perception
is also related
roots in Gladiolus
(1986) demonstrated
Gladiolus
when grown
few contractile
corms produced
to fluctuate
that
roots,
increases in the
significant
for many types of bulbs, the pattern
of environment
With
and a short growing
Alstroemeria,
seen in bulbs.
although
has been shown by the year round
1986) and the work on temperature
(Blom
cultivars
manipulation
and Piott,
cultivars
and constant
1990; Keil-Gunderson
native
of
periods
to the distinct
by some of the new Alstroemeria
exhibited
Alstroemeria
for surviving
mechanisms
i. e.
are related
season in the plant's
these are not equivalent
This
of growth
for subsequent growth,
and a cold requirement
stress seem to be present,
flowering
This
of these roots were produced.
summer dormancy
growth
Halevy
was allowed
Rees (1972) states that
habitat.
much faster un-
of contractile
temperatures,
at constant
this could be achieved
of 29°C (Evenson
fluctuation.
na-
by day degrees
was produced
an optimum
be in their
would
is controlled
(Zingiber
and the production
to temperature
as they
dormancy
regime.
of ginger
temperature
atures produced
of depth
if summer
temperature,
at or above a critical
der a constant
temperatures
night
phases of
pattern
of
(Eggington,
flowering
of
et al., 1989;
Lin, 1984,1985).
The failure
perature.
to establish
It would
seem that
is exhausted
higher temperature,
greater
the `splits'
can initially
dies.
This
the
whole
plant
effect is accelerated
and
by
demanding
faster,
it
the
to
thereby
causes
shoots
grow
as
and causing
it to dry out more quickly.
It is not clear why the roots and tubers on the `split',
it.
from
shoots
the
but if new roots are not produced
resources from the rhizome
fail to support
produce
to tem-
fast enough,
reserves in the rhizome,
rhizome
was shown to be related
some of the `splits'
In replanted
Alstroerneria,
at the newly formed apex of the rhizome
present when planted,
new roots are formed
mainly
and also from the roots and tubers
58
that already exist (Stinson,
(Robinson,
moved
1952). However,
1963). In some way the normal
may have been disrupted
glasshouse bed.
Frequently,
root system.
by the treatment
function
of these organs
received during
may have prevented
This
to being
the plants are sensitive
lifting
from the
on the pre-existing
new growth
many of the roots and tubers on lifted
plant clumps
are damaged or broken off. It is also possible that the tubers did not receive
the stimuli
for the mobilization
required
due to the inappropriate
of their
and translocation
environmental
reserves,
the
at the time of potting
conditions
`splits'.
Overall, the results obtained from this experiment
15°C temperature
do seem to confirm the
considered as the maximum for efficient plant and flower
production by commercial growers of Alstroemeria.
Reducing
studied
irradiance
for both
produced
an overall decrease in each of the parameters
the cultivars
`Valiant'
to which the decrease occurred
from
ably resulted
Similar
with
results
Easter
Lily
(Miller
(Skuterud,
gigantea
The cultivar
which
of reduction
and this is supported
in overall
and Langhans,
Èleanor'.
Higher
irradiance
caused by the
growth
to poorer
and quality
1989), Elymus
growth.
were found
repens and Agrostis
1953a, 1953b).
by the fact that in winter this cultivar
`Valiant'
Horticultural
low in the winter
cultivar
These effects prob-
lead consequently
plant
the degree
appeared to be more sensitive to changes in irradiance,
ers, whereas the cultivar
are generally
would
1984) and ryegrass (Mitchell,
Èleanor'
this period (Parigo
dependent.
was cultivar
in the rate of photosynthesis
reductions
decreases in irradiance,
however,
and Èleanor',
would
continues
flowno
produces
flowers throughout
to produce
Co., personal communication).
and may cause flower
seem to favour
this was not tested in the present
Alstroerneria
experiment.
Light
bud abortion
production,
The interaction
levels
in the
however,
of temper-
daylength
and irradiance
can cause buds to dry up and plants
become dormant
in the summer
(Section
ature,
1.3.1. ) (Parigo
Horticultural
to
Co.,
59
communication),
personal
consequently
(1988)
have
Gomez
shown that
and
the dominant
than
rather
est environment
understorey
is often provided.
shading
Alstroerneria
a for-
In forests it is often
whereas in low scrubland
plant,
favours
aurantiaca
an open site for growth.
Puntieri
it co-exists
with
several species of shrubs and herbs.
The levels of supplementary lighting used in the daylength experiment were
not high enough to allow the plants under the 12 and 16 hour daylengths
to produce greater amounts of photosynthates
than those at the 8 hour
daylength.
was approximately
As a consequence, plant production
equal.
As daylength is usually considered as a stimulus for change in the developlighting was only intended to
mental stage of a plant, the supplementary
initiate such changes and not to influence photosynthesis.
The increase in shoot
nificant,
number
with
of Dambre
the observation
supports
that
does not corroborate
short days suppressed
crease rhizome swelling
rhizome
root dry weight,
number
probably
resulting
hence an increase
organ production
a period
formed
hibition
increased
However, the
made by Dambre,
In ginger (Zin-
and growth.
(Adaniya
growth
Èleanor'
et al., 1989).
and the increase in
from the increase in the tuber
natural
strategy
for overcoming
number,
of
periods
stress.
Increases in daylength
statement
not sig-
10 to 16 hours was seen to de-
from
of the cultivar
may again be part of the plant's
environmental
formation
and enhance vegetative
The increase in tuber
found
who
the other conclusion
increases in daylength
giber officinale)
(1987)
though
at a short day of nine hours.
numbers of shoots were produced
present study
decrease in daylength,
are often
accompanied
be
may
a signal
in photoperiod
prior
by Dambre
of generally
and plants
of flowering
by increases in temperature,
to a period
(1987) that
of summer
or stimulus
dormancy.
This confirms
at the end of the spring flowering
long days and rising temperatures,
form few new shoots
by shorter
for storage
daylengths
period,
storage organs are
and few, if any, flowers.
further
the
supports
The in-
the findings
of
60
other workers on this aspect of the control
et al., 1982; Healy
Molnar,
and Wilkins,
1983; Noordegraaf,
ilar effects on plant
`Croft'),
and Langhans,
of Easter
increasing
cause a decrease in the cold treatment
tivars
Nerine
(Weiler
and Langhans,
flexuosa
(Lilium
Lily
longiflorum
daylength
alba was found to be unaffected
simvar.
was found (Smith
has been shown
Growth
1973).
and
Thunb.
Lilium
of
for flowering
required
1972; Weiler,
1979; Lin
has produced
change in the time to flowering
However,
1962).
the daylength
(Healy
flowering
1975). Varying
height
but no significant
of Alstroemeria
to
cul-
flowering
and
of
(Fortanier
et
by daylength
al., 1979).
The data means and the results
ments in this chapter
ber of replicates
then
result,
should
with
Means with
differences
between
because the num-
caution
high standard
if one or two extreme
especially
Consequently,
be interpreted
used was low.
analyses for the experi-
of the statistical
deviations
data
pieces of
may
are recorded.
may be ex-
the means in the treatments
aggerated.
In the temperature
experiment
there were eight replicates
however, due to the death of plants caused by the treatments,
each treatment,
there were usually less than this number.
were four replicates
for each cultivar
why fairly
could explain
were not significant
3.6
in
for each cultivar
In the other two experiments,
in each treatment.
there
The low replication
strong trends seem to have been established,
which
when analysed.
CONCLUSION
For maximum
rhizome
high irradiance
and a short daylength
is a cut flower crop and flowering
daylengths,
which
of some shading
employed
for efficient
are required.
is inhibited
do not normally
in the summer
of between
a temperature
production
However,
13 and 18°C, a
as Alstroemeria
by high irradiance
occur together,
and a daylength
a compromise
least
of at
and short
position
12 hours are
flower production.
61
The experiments
which
performed
lasted for periods of either 20 or 24 weeks, after
the size of the pot would
have restricted
the growth
of the plants.
Many of the trends only began to show after the plants had been growing
at least 16 weeks.
Any repeat experiments
should
therefore
use larger pots
and longer periods of time to enable the trends to develop further.
provide a better understanding
for
of the effects of the environmental
This could
parameters
studied.
62
Chapter
FACTORS
4:
ESTABLISHMENT
MATERIAL
4.1
AFFECTING
OF `SPLIT'
THE
PLANT
OF ALSTROEMERIA
INTRODUCTION
High
from
plants
(Section
died.
were found
temperatures
(Section
`splits'
to be detrimental
3.2.2).
In contrast,
2.3.1) were used in experiments
It was further
in advance of new roots
those cultivars
that
observed
that
normally
have poorer rates of `split'
produce
of these observations,
investigate
influencing
3.2.1) with
investigated
planting
for their
roots that theyrt
determine
different
whether
whether
new shoots well
did were more likely
to die.
were generally
Also,
seen to
three experiments
were set up to
of `splits'.
The first exam-
the establishment
ined the effect of the range of temperatures
(Section
plants
3, none of the plants
often produced
fewer tubers,
potted
of
establishment.
As a consequence
factors
when small
in Chapter
`splits'
and those that
to the establishment
durations
the `splits'
establishment,
produce.
relied
used in the earlier
at these temperatures.
on the roots
or whether
they could establish
The last experiment
the establishment
and tubers
experiment
The second
present
at
using new
used an in vitro system to
of `splits' could be enhanced by extracts
from the tubers of Alstroemeria.
63
EFFECT
THE
4.2
and Methods
Materials
4.2.1
Three
controlled
of 8,13
environment
and irradiance
vided by Philips
hours
10 W m-2 (60 tLEm-2s-1)
pro-
`Valiant'
of the cultivar
and Èleanor'
were used.
The
and Èleanor'
were derived
from `splits'
that
five months earlier.
The
`Butterfly',
at least five months
had been raised from
however,
before the experiment
were removed from their pots and then treated
plants lifted
from ground
any root or tuber
in three litre pots containing
were replanted
Sixty pots of each cultivar
were transferred
of one week, five plants
At intervals
a glasshouse
and grown
dead within
12 weeks.
that
4.2.2
damage.
of dead and established
x5
(Section
replicates,
with
to that of
1.2.4).
The `splits'
Great
obtained
N12 compost.
to each of the three temperatures.
each cultivar
were transferred
to
twelve weeks.
From previous
ob-
which
did not establish
of 15°C. After
with
12 durations
and
twelve weeks in
by
the
recording
of
plants was assessed,
plants,
be
would
lighting
The glasshouse had no supplementary
the glasshouse the establishment
temperatures
in a manner similar
at a mean daily temperature
was maintained
numbers
plants
seed, ger-
All of the plants
Fisons Levington
from
on for a further
it was concluded
servations,
began.
beds, i. e. split for replanting
care was taken to prevent
Pot grown
tubes.
`Butterfly'
into three litre pots, approximately
had been potted
minated
cycle of 12/12
a daylength
W, warm white fluorescent
`Valiant',
of the cultivars
temperatures
rooms set at constant
of approximately
Color 29,65-80
plants of the cultivars
plants
growth
and 18°C were used, each with
(day/night)
plants
OF TEMPERATURE
an experimental
the
design of 3
for each cultivar.
Results
No significant differences in plant establishment were found for any of the cultivars in any of the temperature treatments.
The plant deaths that occurred
did not exceed five per cent for any cultivar in any treatment
(Table 4.1).
64
Table 4.1: The effect of establishment temperature
cultivars `Valiant', Èleanor' and `Butterfly'
Cultivar
Temperature
`Valiant'
Èleanor'
`Butterfly'
deaths
in
the
on plant
Plant deaths (%)
(°C)
8
0.0
13
18
0.0
0.0
8
1.7
13
18
1.7
0.0
8
13
4.2
4.2
18
2.1
No differences significant
4.3
THE
EFFECT
OF REMOVAL
OF THE
ROOTSYSTEM
4.3.1
Materials
`Splits'
and Methods
produced
from the division
into three litre pots containing
of two year old plant clumps were planted
Fisons Levington
ing all of the roots and tubers were removed
M2 compost.
as close to the rhizome
sible. The pots were placed in a glasshouse without
and set at a mean daily
temperature
vars `Valiant',
`Butterfly'
`Parade',
plants were produced
During
with
a 10 week period
that initially
produced
and Èleanor'
one year later,
the cultivars
or not they subsequently
material
set of
as a control.
were assessed by recording
This experiment
when more plant
lighting
supplementary
were used. A similar
their root systems intact
shoots, whether
plants.
as pos-
of 15°C. Ten pots of each of the culti-
scoring pots at the end of the 10 weeks, according
dead or established
Prior to plant-
to whether
died and by
they contained
was repeated at a similar
was available.
the pots
period
This increased
the
65
total replicate number for each cultivar to 20 plants in each treatment.
4.3.2
Results
Between
60 and 80 per cent of the `splits'
`Valiant',
`Parade'
tivar
Èleanor'
and `Butterfly'
any living
system contained
of the cultivars
roots
40 per cent of the cul-
and approximately
shoots initially.
produced
without
None of the splits
without
a root
by the end of the 10 week period.
material
of the rhizome segments had dried up and it was apparent
All
that very few new
had
been
roots
produced.
When the root system was intact,
`Valiant',
the cultivars
`Parade' and `Butterfly'
Èleanor'
of the cultivar
between 70 and 90 per cent of the splits of
By the end of the 10 week
shoots initially.
produced
period between 55 and 75 per cent of the pots of the cultivars
rade' and `Butterfly'
contained
up, as happened
4.4
4.4.1
THE
to the `splits'
EFFECT
Materials
D). These extracts
medium,
The extracts
had dried
without
roots.
OF TUBER
`Valiant',
EXTRACTS
were filter sterilized
without
IN VITRO
onto media containing
extract
was performed
specific interaction
a similar
from
and then added to Alstroemeria
pro-
for GA3 (Section
2.4).
to provide
`Valiant'
extract
the tubers
action
`Parade'
and Èleanor'
from the same cultivar
of the cultivar
and the compounds
was occurring
of 10 per
a concentration
to see, if any effect was produced,
between a cultivar
(Appendix
and Èleanor'
BAP, in the way described
of the cultivars
explants
media containing
or whether
The plants that failed to establish
were added to the medium
cent. Rhizome
latter
Èleanor'
were prepared from fresh tubers removed from pot grown
plants of the cultivars
transferred
`Pa-
and Methods
Total tuber extracts
duction
`Valiant',
25 per cent of the cultivar
and approximately
viable plant material.
55 per cent
and approximately
within
and onto
`Butterfly'.
whether
within
all cultivars
were
The
it was a
its tubers
and tubers.
66
Some explants
tion medium
were also cultured
The cultures
daylength
W, fluorescent
cycle, with
tubes giving
by Thorn
Pluslux
3500,70
5W m-2 (28 pE m-2s-1)
of light.
provided
approximately
period and the data analysed
4.4.2
light
x 20 replicates
(Section
10 jars
5.2) with
hour
12/12
15°C
at
and a
were incubated
(Section
2.5) at intervals
were assessed
treatments
(Section
were placed in each jar
explants'
for each treatment.
Cultures
produc-
as a control.
Five `standard
(day/night)
Alstroerneria
on unsupplemented
of four weeks, over a 12 week
2.5) with
an experimental
design of 3
of the rhizome
and roots of
for each cultivar.
Results
The tuber extracts
severely inhibited
(Figures
all cultivars
4.1 and 4.2 and Table 4.2).
between the response of the explants
the same cultivar
A marked
or medium
difference
of the shoots
the growth
on the medium
containing
extract
was seen in the length
by explants
difference
containing
from the cultivar
was seen
extract
from
`Butterfly'.
of the shoots produced.
Many
containing
extracts
between
two and four times longer than those on the control
were
medium,
with
produced
Little
growing
on media
a few being up to six times as long. This effect of the extracts
was not
quantified.
4.5
DISCUSSION
The results from the temperature
experiment did not confirm the earlier
observations that an increase in temperature
in `split' establishment.
decrease
caused a significant
This second experiment indicated that, within the
range studied, temperature had no effect on the establishment of Alstroemeria
`splits'.
Since the methods and the cultural conditions employed were vir-
tually identical in the two experiments, the discrepancy in the results would
differences
in the `splits' used. Two main
that
there
were
strongly suggest
differences were recognised. The first was the age of the plants from which
67
6
5
0
0
03
a)
ý. 2
i
0
`Valiant'
M
Control
`Parade'
Cultivar
0
`Valiant'
`Parade'
Èleanor'
'Own'
Èleanor'
®
`Butterfly
p=0.05
P=0.01
P=0.001
Figure 4.1: The effect of extracts from their own tubers and those of the
cultivar `Butterfly', on shoot production by rhizome cultures of the cultivars
`Valiant', `Parade' and Èleanor'
68
1.50
M
1.25
0
1 1.00
s.
Z 0.75
w
0
0.50
z 0.25
0.00
`Valiant'
M
Control
'Parade'
Cultivar
0
'Own'
Èleanor'
®'Butterfly'
`Valiant'
not significant
`Parade'
P=0.001
Èleanor'
p=0.01
Figure 4.2: The effect of extracts from their own tubers and those of the
by
lateral
the
`Butterfly',
of
rhizome
cultures
production
rhizome
on
cultivar
Èleanor'
`Valiant',
`Parade'
and
cultivars
69
Table 4.2: The effect of extracts from their own tubers and those of the
by
'Butterfly',
on
production
root
rhizome cultures of the cultivars
cultivar
`Valiant', `Parade' and Èleanor'
Cultivar
`Valiant'
Tuber extract
Control
'Own'
`Butterfly'
`Parade'
Èleanor'
0.89
0.66
0.54
0.62
0.38
0.45
0.85
0.64
0.60
the 'splits'
had been derived.
were produced
of the cultivars
Those of the cultivar
from seed raised plants,
in production
had been cropped for flowers. Consequently,
`Butterfly'
for ap-
were produced
none of
beds for at least two years or
this plant material
could be con-
in
the earlier experiment
that
than
used
younger
sidered as physiologically
and had not experienced
associated with
and Èleanor'
five months old. Therefore,
approximately
these plants had been growing
`Valiant'
been
had
established
which
from pot grown `splits',
five months.
proximately
`Splits'
flower production
the second experiment
in
the rhizome rootstock
of resources
the reduction
and cropping.
Hence, the `splits'
used in
were probably
in
the
those
than
used
more vigorous
and probably
the more important
earlier experiment.
The second difference,
the treatment
received by the plants during
'splits'
prior to preparing
of Alstroemeria
are lifted
soil being removed
fairly
was removed carefully
minimising
from the rhizomes.
mechanically
roughly.
lifting
of the two, was
the
soil
of
and removal
In commercial
practice,
clumps
from the glasshouse soil, with
In the second experiment,
the
the compost
from the rhizome and roots of pot grown plants, thus
damage to the root system. The reduced incidence of plant deaths
in the second experiment
may, therefore,
have resulted from the `splits' being
70
less damaged and, as a consequence, in a better physiological state to sustain
the growth of the `split' and subsequent plant establishment.
higher
The slightly
incidence
of the plants,
i. e. they were only about five months
the `splits' of the cultivar
the seed. Consequently,
than those normally
The removal
inal root
of the roots
system
failed
ficient
reserves within
not sufficient
on splits
plant
from
being
exhausted
zome
Consequently,
Comparisons
on a `split'
for the growth
to be that
behind
that
are damaged
way to one that
by the cultivars
such as the morphology
tubers they produce.
cultivars
(Figure
there
of their
but
shoot production,
the reserves of the rhiThe major
production,
of shoots.
formed.
made in Chapter
3. If the roots
then such a propagule
It may, therefore,
of exhaustion
produce
followed
of reserves
by
be related to the number of roots
properly.
studied,
were suf-
into the rhizome does not match
is rootless.
could, therefore,
and not functioning
exhibited
Rootless
of the production
functional,
hence
not
and
Failure to establish
establish,
that
of the shoots already
shoots and suffer the same problems
death.
that
the rate of new root
can be made with observations
will act in a similar
initial
or to prevent
uptake of water and nutrients
are damaged,
of the orig-
before the plant becomes established.
lags considerably
the requirements
of
were sometimes
establishment.
also indicated
to sustain
growth
at this stage appears
at least initially,
old from germination
`Butterfly'
for subsequent
the rhizome
to sustain
in
to the small size
the importance
confirmed
The results
to establish.
`Butterfly',
used commercially.
to the propagule
`splits'
problem
may be attributed
to the other two cultivars,
comparison
smaller
deaths for the cultivar
of plant
The different
may be associated
root systems and the numbers
capacities
with
to
factors
of roots and
These factors have been shown to vary greatly
between
2.1).
The reliance on a pre-existing, undamaged root system and the observation
that shoot production
is generally in advance of root production,
may be a
function of the shoots being a greater sink for nutrients than the root system.
71
Such a mechanism
these greater
rhizome.
nutrients,
thought
(Chapter
could be analogous
to be involved
7).
events genetically
in the maintenance
It is also possible
The profound
in
explant
changes
growth
transport
preferential
moic resources for shoot growth,
increasing
The timing
intact
the present
rhizome
growth
in Alstroemeria
appear that
shoots, possibly
with
an active inhibition
tuber
of growth
would leave
transport
of resources
rhizome
by
growth
that
(Chapter
on dead rhizomes
shoot growth
contain
was promoted
than previously
compounds
such stress may have caused the plants
growth.
There may, therefore,
be a requirement
are mobilized
with
at the expense of
that
the tuber
thought.
It would
which encourage rapid
for use after periods of environmental
of the tubers
3), together
indicates
extract,
may be more important
that
and the observation
production
habitats
the contents
these points.
inhibit
could
promoter
in the presence of tuber
the tubers
times on the rhizome.
of resources to the shoots or a specific
for tuber
be
present
can
observation
are
production
for resources in favour of the shoots.
and conditions
tubers
in
whereas preferential
of a specific growth
competition
of apical dominance
The presence of a growth inhibitor
of shoot growth.
or the action
of
on media supplemented
by either
may have been mediated
parts of the
movement
shoot and root
be necessary to clarify
studies would
enhancement
that
to occur at different
programmed
More detailed
of the rhizome,
to that of the directed
is
that
to the shoots
movement
to
of compounds
by the shoots, at least in respect to the younger
The latter
extracts,
a passive movement
a directed
sinks, or possibly
also controlled
plants
be purely
could
growth
of
stress. In their natural
to lose their
aboveground
for specific conditions
for subsequent
utilization
before
elsewhere
in the plant.
The distribution
ure 2.1).
(Fig-
of tubers on the root systems varies between cultivars
For example,
the cultivar
with the other three cultivars.
than shown, it would
Èleanor'
has very few tubers
If the rhizome of Èleanor'
possess few or no tubers.
However,
compared
is shortened
further
the experiment
on
72
on `split'
the effect of temperature
difference
in the levels of establishment
studies
growth
at a biochemical
a carbohydrate
regulator,
level
caused by the tuber
the change in growth
Èleanor'
the cultivar
the tubers
there was no
and
for
are not a prerequisite
of `splits'.
successful establishment
More detailed
between
This suggests that
the other cultivars.
showed that
establishment
to determine
are required
extracts
was produced
by a plant
or inorganic
or some other organic
if
com-
pound.
4.6
CONCLUSION
It would
`splits'
stroerneria
plant
to be essential
appear
to the absolute
The tubers
establishment.
However,
establishment.
to keep damage of the root
they
nature
for plant
growth
of the active
on the mechanism
remembered
although
that
parallels
been concerned
probably
initial
return.
the tuber
have only a small
shoot growth,
interaction
extract
extracts
exercised in drawing
for overcoming
peri-
when conditions
more
can be made.
experiment
It should
was performed
reported
plant responses in vivo. Consequently,
conclusions
the
before any conclusions
be
drawn,
the other experiments
may
with
role in `split'
More work is needed to elucidate
in tuber
component(s)
of the tuber
to achieve successful
may be of importance
ods of stress and for maximizing
favourable
in order
minimum
of Al-
system
also be
in vitro
and
have
far
so
caution
must be
from this in vitro experiment.
73
Chapter
PRELIMINARY
5:
INVESTIGATIONS
5.1
IN VITRO
INTRODUCTION
between plants in a crop situation
The competition
information
also available
1985).
However,
density
on the competition
evidence suggests that
reducing
the number
of Hemerocallis
number
An experiment
of explants
before growth
of explants
could
experiments
of explant
is important,
designed
be incubated
was significantly
volume
to determine
in a specified
decreased.
would be optimised,
as
vessels significantly
has also
ratio
This
the optimum
culture
vessel,
it
information,
and overall explant
by preventing
and
Van,
et at., 1989; Tran Thanh
was hoped, would ensure that rhizome production
in subsequent
and Lang,
et al., 1990). Morphogenesis
(Cousson
was, therefore,
that
factor
in culture
explants
with
This
limited
vessels.
by changes in medium-explant
also by the shape of the container
1981).
in culture
of a nutrient
(Lumsden
rates
been shown to be affected
on the effect
reports
between explants
the availability
increased multiplication
(Healy
in this area for Alstroemeria
are few published
there
is well documented,
growth
any interactive
effects between the explants.
A second experiment
was designed to determine
seen in vitro was correlated
with the multiplication
It had been suggested that the smaller the explant,
whether
the size difference
rates of different
cultivars.
the lower its propagation
rate.
74
OF EXPLANT
EFFECT
5.2
DENSITY
ON GROWTH
IN VI TR O
Materials
5.2.1
The cultivar
the largest
was selected for this experiment
Èleanor'
of the four cultivars.
rhizome
would
actions
Methods
and
be greatest
meria production
The cultures
cycle, with
vided
were incubated
by Philips
weeks.
medium,
an irradiance
Color
The cultures
5.2.2
explants'
were cultured
20 Win-
of approximately
29,65-80
W, warm
white
(Section
were assessed
was recorded
affect the size of the explants.
an experimental
fluorescent
rhizomes
profor 12
tubes,
of four weeks,
for each treatment,
size. Any lateral
daylength
2 (120 pE m-2s-1),
2.5) at intervals
not be large enough after a maximum
2.5), giving
One, two,
of this cultivar.
at 15°C and a 12/12 hour (day/night)
overall measure of the explant
significantly
any inter-
that
on 25 ml of .4lstroeusing ten jars for each of the explant densities.
when only the shoot number
would
It was considered
between the explants
three, four, five or six `standard
because it possessed
to provide
or roots produced,
of only four weeks1 growth,
The data wee analysed
design of 6 treatments
an
to
(Section
x 20 replicates.
Results
There
was little
difference
in shoot production
ties of one to five in a culture
jar (Table
shoot production
with increasing
density
was apparent
of six per jar did, however, result
between
densi-
in
decrease
a small
5.1), although
explant
the explant
number.
in a significant
The explant
decrease in shoot
production.
5.2.3
Discussion
The interaction
between the explants at a density of six per culture jar,
(Section
5.1).
the
the
earlier
mentioned
studies
results of
supports
inhibition
of shoot production
due
by-products
have
been
to
may
This
of the
for
the
to
of
explants
and/or
a
nutrients within
metabolism
competitive effect
75
Table 5.1: The effect of explant density in vitro on shoot production
cultivar Èleanor'
Explant density
Number of shoots
1
2
4.6
4.5
3
4
4.2
4.2
5
6
4.1
3.4
in the
P=0.01
the medium.
On the basis of this result five `standard
as the explant
density
tion in this number
5.3
is detailed
COMPARISON
THE
5.3.1
for subsequent
FOUR
Materials
OF THE
`Parade',
Alstroemeria
production
medium
jars of each cultivar
`Butterfly'
OF
IN VITRO
CULTIVARS
were incubated
by Philips
(Section
of approximately
explants'
per jar.
Ten
20 W m-2 (120 µE in-2
W, warm white
were assessed at intervals
2.5), giving
on
were cultured
(day/night)
hour
15°C
12/12
at
and a
Color 29,65-80
for 12 weeks. The cultures
and Èleanor'
using five 'standard
cycle, with an irradiance
data analysed
sections.
and Methods
`Valiant',
s-1), provided
of the appropriate
GROWTH
ALSTROEMERIA
Any varia-
in this study.
experiments
at the beginning
The cultivars
daylength
explants'
jar
was selected
culture
per
an experimental
fluorescent
tubes,
of four weeks and the
design of 4 cultivars
x
20 replicates.
76
5.3.2
Results
There were no significant
differences
between the four cultivars
(Table 5.2). However, there were significant
ences in shoot production,
of the cultivars
cultivar
`Butterfly'
`Valiant'
5.1), with
appeared
The morphology
to be more like that
the levels of shoot
(Table 5.2). In addition
`Butterfly'
differences
there was also a considerable
variability
within
the cultivars,
(Figure
the cultivars
of the
tending
production
to be closer to that of the cultivar
between
differ-
the highest
producing
the lowest numbers.
and `Parade'
(Figure
Èleanor'
and root production
rhizome
Èleanor'
with the cultivar
and the cultivar
numbers
in lateral
to the
amount
of
5.1).
Table 5.2: Comparison of the growth in vitro, of the Alstroerneria
cultivars
`Valiant',
Mean numbers of lateral rhiand Èleanor'.
zomes, shoots and roots
5.3.3
Cultivar
`Valiant'
`Parade'
Lateral branches
0.5
0.6
Shoots
4.2
4.4
Roots
0.06
0.09
`Butterfly'
Èleanor'
0.3
0.5
4.0
4.9
0.00
0.00
not significant
p=0.01
not significant
Discussion
The results from this experiment
supplied
by Parigo
the best growth
growth,
However,
Horticultural
in vitro
the cultivars
confirm the information
with
`Valiant'
these differences
Co. Ltd.,
the cultivar
on the four cultivars
i. e. the cultivar
`Butterfly'
shoots produced
and not in root
being of primary
importance
shows
the poorest
showing
and `Parade' being intermediate
in growth
Èleanor'
(Section
2.2).
were only expressed in the number
lateral
or
rhizome
in the micropropagation
production,
of
the latter
of Alstroemeria
hybrid
cultivars.
77
k
{i
'f
ýi Qý
ýr
ýt
A
.
'- ,
t"4q,
ý-
B
ýý
4
%*
)W.W,
C
Figure 5.1: Cultures of the cultivars 'Valiant' (A), `Parade' (B), `Butterfly'
(C) and Èleanor' (D), after four weeks growth in vitro. Bar =2 cm
78
The suggestion
tivars,
that variation
in multiplication
may have arisen due to differences
of the more vigorous
that of less vigorous
cultivars,
cultivars.
zomes being produced
(Section
1.2.2) would
Confirmation
rate existed between the cul-
in growth
being maintained
rates leading to explants
in vitro at sizes larger than
This could lead to a higher rate of lateral
from the former,
as more of the second axillary
rhibuds
be present per explant.
of differences in the in vitro growth of the cultivars `Valiant',
and Èleanor', justifies the selection of these four culti-
vars for this study. The variability
make future experimental
seen within the cultivars may, however,
assessment within this study somewhat problem-
atic, especially when replicate number is low.
79
Chapter
THE
6:
EFFECT
TEMPERATURE,
OF
IRRADIANCE
AND
ON RHIZOME
DAYLENGTH
GROWTH
IN
VITRO
6.1
INTRODUCTION
few published
Of the relatively
of Alstroemeria
on the growth
ronment
changes in temperature
Pierik
on the effects of the culture
reports
and light,
(1988)
et at.
considering
with
envi-
in vitro, only four of these mention
only Bridgen
these physical
and Winski
(1989) and
factors of the culture
environ-
ment in any detail.
Experiments
daylength
were designed to assess the effect of temperature,
on the growth
with
The broad ranges of irradiance
and daylength
were used in
Bridgen
factors
upper
present study
were identical
lower
limits
and
and Winski
the upper temperature
an optimum
In each experiment,
in vitro.
of the factor
order to establish
in vitro.
explants
and
the exception
the environmental
being studied.
of rhizome
irradiance
limit
(1989) and Pierik
for Alstroerneria
of 15°C. Therefore,
tolerance
was approximately
in order to provide
of Alstroemeria
for Alstroerneria
et al. (1988) reported
the range of temperatures
below
that limit
was
the lower temperature
of these factors
that
20°C with
chosen for the
more information
on
in vitro.
80
6.2
6.2.1
EFFECT
THE
OF TEMPERATURE
and Methods
Materials
Five `standard
`Butterfly
three of the cultivar
production
stroemeria
irradiance
Color
32,15
W, Delux
assessed (Section
and
jars containing
Al-
were incubated
daylength
fluorescent
white
provided
by Philips
The cultures
tubes.
of the explants
at
cycle and an
of four weeks, over a 12 week period
of the quality
were also recorded.
were
and
The ex-
(Section
2.5) with
data
the
analysed
repeated and
was subsequently
design of 3 temperatures
an experimental
6.2.2
(day/night)
(26 i, E m-2S-1),
m-2
2.5) at intervals
visual observations
periment
6W
warm
and Èleanor'
Ten jars of each cultivar
a 12/12 hour
of approximately
`Parade'
were placed into culture
medium.
and 18°C, with
9,12,15
`Valiant',
of the cultivars
explants'
x 40 replicates
for each cultivar.
Results
Temperature
affected
the growth
significantly
greatest effect was on the number of lateral
vars `Valiant'.
of lateral
rhizomes
duced between
terfly'
All of the cultivars
in temperature.
Èleanor'
between
However,
number
12°C. Èleanor'
in shoot number
`Valiant'
6.1). The culti-
between
production
`But-
the cultivar
12 and 15°C
15 and 18°C.
shoot number
only the increases for the cultivars
(Figure
A slight
6.2).
and `Parade'
for the cultivar
decline
was observed
`Butterfly'
was the only cultivar
with
The
the increase pro-
However,
In contrast,
showed a trend of increasing
were significant
in the cultivars
rhizome
cultures.
in
increase
the number
an
all exhibited
15 and 18°C was only small.
difference
(Figure
rhizomes
increase in temperature.
with
showed a decline in lateral
and little
Shoot
and Èleanor'
`Parade'
of the rhizome
remained
which
exhibited
`Valiant'
in shoot
between
fairly
with increase
and
number
15 and 18°C.
above
constant
a continuous
increase
increase in temperature.
Very few roots were produced
by the four cultivars
differences
and any
were
not significant (Table 6.1). A slight increase in shoot height was observed
81
1.0
0.9
2
°
0.8
0.7
0.6
0.5
ö 0.4
M^`
W
0.3
o.2
0.1
0.0
'Valiant'
M
'Parade' `Butterfly
Cultivar
9°C []12°CEM
'Eleanor'
15°CEE]] 18°C
`Valiant'
`Parade'
`Butterfly'
P=0.001
P=0.01
not significant
Èleanor'
p=0.001
Figure 6.1: The effect of temperature on the number of lateral rhizomes produced in vitro by the cultivars `Valiant', `Parade', `Butterfly' and Èleanor'
82
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
'valiant'
ý9°C
Parade'
`Butterfly
Cultivar
'Eleanor'
012°C®15°C®18°C
`Valiant'
`Parade'
`Butterfly'
Èleanor'
P=0.05
not significant
not significant
p=0.001
Figure 6.2: The effect of temperature on the
number of shoots produced in
vitro by the cultivars `Valiant', `Parade', `Butterfly' and Èleanor'
83
Table 6.1: The effect of temperature
on the number of roots produced
by
`Valiant',
the
cultivars
vitro
and Èleanor'
Temperature
(°C)
9
12
15
Cultivar
`Parade' `Butterfly'
0.06
0.00
0.06
0.00
0.06
0.00
`Valiant'
0.15
0.15
0.05
0.07
18
0.05
in
Èleanor'
0.04
0.04
0.00
0.00
0.00
with
increasing
This
temperature.
the more vigorous
increase
in vitro showing
cultivars
dependent,
was cultivar
the greatest
with
increases in shoot
length.
6.3
6.3.1
THE
EFFECT
and Methods
Materials
Five `standard
terfly'
OF IRRADIANCE
explants'
of each of the four cultivars
`Valiant',
`Parade',
`But-
and Èleanor'
were placed into culture
jars containing
Alstroemeria
medium.
Ten jars of each cultivar
were incubated
at three irra-
production
diances of approximately
respectively),
provided
20,10
by Philips
and 5W
m-2
Color 29,65-80
tubes with
a 12/12 hour (day/night)
maintained
(Section
15°C
at
daylength
(120,60
and 30 µE m-2s-1,
cycle. The temperature
was
6.5).
The two lower irradiances were achieved by placing the culture jars under
by
75
50
light
density
filters
transmission
per cent.
and
which reduced
neutral
This filter type is designed to reduce the levels of all the wavelengths of light
To
N3).
Roscosun
(Rosco
Correction
Filters,
Colour
3402,
Cinegel,
equally
produce the light reduction of 50 per cent, one layer of the filter was used
84
and for the reduction of 75 per cent, two layers of the filter were used. Light
readings were taken under one and two layers of the filter.
were assessed (Section
The cultures
of 12 weeks and visual
period
observations
The experiment
were also recorded.
explant
2.5) at intervals
design of 3 irradiances
of the quality
was subsequently
data
the
analysed
and
material
of four weeks, over a
x 40 replicates
(Section
of the explants
repeated
2.5), with
with
new
an experimental
for each cultivar.
Results
6.3.2
had
used
no significant
The range of irradiances
the rhizome
`Butterfly',
(Table
cultures
6.2).
decreased.
as irradiance
vigorous
6.4
THE
EFFECT
numbers of lateral
Again,
this was cultivar
the greatest
dependent,
with
the more
`Valiant',
`Parade'
differences.
of each of the three
and three `standard
explants'
cultivars
`Butterfly'
of the cultivar
culture
jars containing
Alstroemeria
jars of each cultivar
were incubated
in each of four daylengths,
and 20 hours of light per 24 hour period.
15°C (Section
6.5) and an irradiance
was provided
The cultures
also recorded.
and visual
production
The temperature
of approximately
2.5) at intervals
observations
The experiment
on the quality
was subsequently
x 40 replicates
Ten
i. e. 8,12,16
was maintained
at
6W m-2 (26 uE m-2tubes.
of four weeks, over a
of the explants
repeated
with
were
new explant
(Section
2.5), with an experimental
data
the
and
analysed
3 daylengths
were
medium.
Color 32, Delux warm white fluorescent
by Philips
(Section
were assessed
12 week period
material
rhizomes
OF DAYLENGTH
explants'
and Èleanor'
s-')
and
and Methods
Five 'standard
placed into
`Parade'
`Valiant',
of
A slight increase in shoot length was also evident
in vitro exhibiting
cultivars
Materials
6.4.1
For the cultivars
there was a slight trend of decreasing
with decrease in irradiance.
effect on the growth
design of
for each cultivar.
85
Table 6.2: The effect of irradiance on the numbers of lateral rhizomes,
shoots
and roots produced in vitro by the cultivars `Valiant', `Parade', `Butterfly'
and Èleanor'
Cultivar
Irradiance
Lateral rhizomes
Shoots
Roots
100
0.61
4.37
0.07
50
0.55
4.42
0.06
25
0.53
4.35
0.07
100
50
0.39
0.30
4.26
4.18
0.03
0.03
25
0.31
4.20
0.02
100
50
25
0.34
0.31
0.31
4.07
4.08
4.06
0.00
0.00
0.00
100
0.64
5.20
0.00
50
25
0.67
0.63
5.31
5.24
0.00
0.00
No differences
significant
(%)
`Valiant'
`Parade'
`Butterfly'
Èleanor'
86
6.4.2
Results
Daylength
produced
A slight trend of increasing
in the cultivars
occurred
changes in growth of the rhizome cultures.
no significant
lateral
daylength,
rhizome number with increasing
`Valiant',
`Butterfly'
and Èleanor',
whereas
the
`Parade' showed no response at all (Table 6.3). The number of shoots
cultivar
and roots
produced
exception
to this was the number
were unaffected
which decreased as daylength
by the range of daylengths
of roots produced
used.
by the cultivar
An
`Valiant',
increased.
A decrease in shoot length was observed with increase in daylength,
however,
(Section
irradiance
the
6.4.2) the decrease was slight and
as with
effects of
dependent.
cultivar
6.5
DISCUSSION
have their
All plants
Alstroemeria
own temperature
in vitro it would
production
appear
the medium
and/or
the optimal
of nutrients
uptake
of the explant
metabolism
12 and 15°C,
increases in tem-
upon by further
of maximal
For
for rhizome
there is a tendency
that
improved
This may be a consequence
perature.
in vivo and in vitro.
rate to reach a level between
and multiplication
can not be significantly
which
tolerances
from
at these higher
temperatures.
These results agree with
Winski
(1989).
found
between
that
Pierik
the findings
(1988)
et al.
noted that
15 and 21°C,
15°C was the optimum
comparing
the present
multiplication
experiment,
and daylength
(1988)
et al.
and Bridgen
of Pierik
and Bridgen
no significant
and Winski
for the growth
differences
(1989)
of Alstroemeria
and
were
established
in vitro,
after
from
Based
20°C.
10,15
the
result
and
on
rates at
the experiments
were conducted
assessing the effects of irradiance
at 15°C.
Irradiance and daylength both influence the total light energy received by
plant
cultures.
In the present study
these two factors had no significant
ef-
87
Table 6.3: The effect of daylength on the numbers of lateral rhizomes, shoots
and roots produced in vitro by the cultivars `Valiant', `Parade', `Butterfly'
and Èleanor'
Cultivar
Daylength
Lateral
rhizomes
Shoots
Roots
(hours)
`Valiant'
`Parade'
`Butterfly'
Èleanor'
8
12
0.58
0.61
4.39
4.37
0.22
0.18
16
0.61
4.39
0.11
20
0.66
4.33
0.13
8
12
16
20
0.42
0.39
0.39
0.44
4.20
4.26
4.18
4.19
0.03
0.03
0.05
0.06
8
0.29
4.02
0.00
12
0.34
4.07
0.00
16
0.44
4.06
0.00
20
0.37
4.10
0.00
8
0.59
5.20
0.00
12
0.64
5.20
0.03
16
0.71
5.21
0.06
20
0.73
5.23
0.02
88
fects on any of the growth
less,
rhizome
or
Pierik
et al.
to 9.7 Win-2
(1988)
Horticultural
also found
and using daylengths
that
(1989) in an abstract
s-1 for the rapid
of 8 and 16 hours,
absence of photosynthetic
growth
be
may
attributed
activity
of the tissues,
within
1.5
for the culturing
of
However,
irradiance
and
of 120 µE in-`
no
(Yamada
sugar
light
(Grout
and Aston,
x ananassa)
demonstrated
that
low
photosynthetic
content and
1978) and further
the explants
role in their
plays an important
Studies on cauliflower
(Grout
Furthermore,
and Millam,
(Brassica
investigations
1985) cultured
showed no net carbon
photosynthetic
ability
(1985), following
However,
oleracea var.
on strawberry
in eitro,
have
uptake
and
Their
growth
was
nutrient
in vitro, failed to
when transferred
the leaves which developed
from the work of Wardle
1983b), also proposed that the major function
is dependent
of
dioxide
and degenerated
in vivo, gained full photosynthetic
is as a transitory
growth,
upon exogenous supplies of sugar added to the medium.
to an in vivo environment.
to transplanting
in cul-
supply
an exogenous
it was noted that the leaves which developed
develop significant
activity
some photosynthetic
that they also possessed very low levels of photosynthesis.
seen to be dependent
in the culture
and active photosynthesis.
of chloroplasts
tissues can not grow without
et al., 1978).
A lack of autotrophic
to be caused by deficiencies
thought
yet although
most chlorophyllous
Millam
Bridgen
Unfortunately,
in vitro.
the explants.
to low chlorophyll
can develop and maintain
tissues,
(Fragaria
ability
for good development
Chloroplasts
botrytis)
from
tested could have been due to an
The lack of response to the light treatments
tured
the irradiance
varying
of Alstroemeria
communica-
details were provided.
experimental
conditions
Co., personal
quote an optimum
propagation
of 2.5 W in-2
however, the shoots began to
had no effect on rhizome multiplication.
Alstroemeria,
Winski
At irradiances
studied.
was unaffected,
multiplication
(Parigo
light
levels
these
at
etiolate
tion).
parameters
subsequent
competence.
and mineral
and
(1979,1981,1983a,
et at.
of the leaves produced
source, upon which the newly transplanted
for its carbon
Grout
sources, until
in nitro
plantlet
it has produced
new
89
leaves in vivo.
6.6
CONCLUSION
The present results indicate
of Alstroemeria
zome explants
lower than this, significant
rhizome
it is suggested that
decreases in explant
in order to prevent
be kept at an irradiance
8 hours of light
growth
in a 24 hour day/night
of the explants.
Shorter
been
not
assessed. However,
irradiance
of the light
should be cultured
may be required,
period
that
in vitro.
growth
rate, will begin to occur.
multiplication
levels should
that 15°C is the lowest temperature
etiolation
With
at which rhi-
At temperatures
and in particular
respect to irradiance,
of the explants,
of at least 5W
in-'.
the light
For daylength,
cycle seems to be sufficient
daylengths
the
for good
may be feasible but as yet have
if a shorter period of light is used, then a higher
if it is the total
is most important
light integral
and not the length
for the growth
and development
of the explants.
90
Chapter
7:
THE
DOMINANCE
RATE
7.1
INFLUENCE
ON THE
OF THE
OF APICAL
MULTIPLICATION
RHIZOME
IN VITRO
INTRODUCTION
The shoot apex has a very important
inance (Section
1.4.1). It has been suggested that
apex of a plant
produce
are established.
interactions
of lateral
which the suppression
of apical dominance,
of compounds
thereby
which interfere
is preventing
keeping down the multiplication
com-
with the mechanisms
buds from their inhibited
set up to determine
the outgrowth
by
of the apex
there are several different
describes experiments
extent apical dominance
the plant,
within
dominance
the
and
thereby releasing axillary
This chapter
of growth.
bud growth
signals from the
chemical
at other locations
It has also been shown that
pounds and combinations
of apical dom-
role in the phenomenon
state
to what
of ancillary rhizomes
rate of rhizomes
of Alstroemeria
and
in
vitro.
Removal
of the shoot
apex may affect
(Richards
et al., 1988; Pierik,
expanded
basal internodal
1987). Subdivision
axillary
the fragment
for Agropyron
remove the sites which produce
manipulation
An experiment
of rhizome
of the rhizomes
into single
of adjacent
repens (Chancellor,
used, the greater
1974),
of
In these ways it may be possible
to
the dominance
of
the signal for maintaining
was set up to examine
explants
rhizomes
the number
of rhizome
buds released from inhibition.
the apex.
of lateral
segments should remove any influence
shoots, as has been demonstrated
where the smaller
the outgrowth
the effect of the physical
on apical dominance.
91
It is well documented that certain PGRs play a role in the control of apical
dominance (Section 1.4.2). The following PGRs were tested.
TIBA was selected for its action as an anti-auxin.
i
auxin
IAA,
is considered
The naturally produced
to be important
in the establishment
and maintenance of apical dominance.
ii
Thidiazuron
tion.
was selected for its very active cytokinin-like
It is more active at lower concentrations
is known to decrease apical dominance.
mode of ac-
than BAP and the latter
Thidiazuron
may therefore
exhibit a greater effect on apical dominance.
iii NAA/BAP
combinations were selected because of the known synergistic
effect of auxins on some of the actions of cytokinins, the latter decreasing apical dominance,
with
auxin concentrations
lower than that of the
cytokinin.
iv
GA3 was selected
for its capacity
to increase
the elongation
of shoots.
If the shoots and rhizome of Alstroemeria could be made to elongate,
then the increased spatial separation of the axillary buds from the apex
may reduce their inhibition
v
Paclobutrazol
reduction
by the apex.
for
its
anti-gibberellin
was selected
in shoot growth,
it may be possible
effects.
By causing
a
to achieve a relocation
of any unused resources into the growth of the axillary buds.
BAP was also added to the media containing
because it was considered
sponse, then the addition
TIBA,
GA3 and paclobutrazol,
that if any of these PGRs produced
of BAP may produce an additive
a positive
re-
or even synergistic
effect.
92
7.2
MECHANICAL
CONTROL
OF APICAL
DOMINANCE
7.2.1
Materials
Rhizome
and Methods
'Valiant',
of the cultivars
cultures
`Parade'
and Èleanor'
were used
to provide the following six types of explant for subculturing.
" S1
Three enlarged basal internodes + rhizome apex + shoots.
S2
"
Three enlarged basal internodes + rhizome apex - shoots.
" S3
Three enlarged basal internodes - rhizome apex + shoots.
" S4
Three enlarged basal internodes - rhizome apex - shoots.
" S5
Three single enlarged basal internodes + shoots.
" S6
Three single enlarged basal internodes - shoots.
Five rhizome
Alstroerneria
taining
of a single type were placed in each culture
explants
types for each cultivar
hour (day/night)
were incubated
daylength
W in-2 (120 pE m-2s-1),
fluorescent
After
medium.
production
of 15°C and a 12/12
an irradiance
by Philips
provided
20
of approximately
Color 29,65-80
W, warm white
tubes.
four weeks, the number
sidered as the control
in any way.
ment was subsequently
an experimental
which
repeated
Alstroemeria production
the explant
type
to a percentage
Si was conmanipulated
of the total
been
have
produced.
could
data
the
analysed
and
design of 6 treatments
apices removed
had been produced
that
as it had not been physically
converted
rhizomes
rhizomes
of the data,
treatment,
The data
of lateral
The rhizome
of lateral
For the analysis
was recorded.
number
Five jars of each of the six explant
at a temperature
cycle, with
jar con-
x 10 replicates
in some of the treatments
(Section
potential
The experi2.5), with
for each cultivar.
were recultured
medium and returned to the stock cultures.
on
The
93
`Butterfly'
cultivar
its
of
rhizome
size
explants
have been impossible
bud,
second axillary
the rhizome
removing
made it impractical
to carry
out the physical
of the range of explant
the enlarged
basal internodes
It
types.
had
damage
occurred
no
to ensure that
when dividing
because the small
this experiment,
for
the preparation
necessary
manipulations
would
from
was excluded
to the
or when
apex.
Results
7.2.2
The three cultivars
used. Treatments
plant treatments
production,
duced significantly
Removal
more lateral
in lateral
apices. Subdivision
than
ducing
the highest
manipulations
lateral
affected
CHEMICAL
7.3
significant
and 7.3).
a significant
both
of
removal
However,
types of
effect of the removal
the additive
further
of the rhizome
basal
internodes
enlarged
with single
7.1,7.2
rhizome
S4, S5 and S6 pro-
apices did not produce
production.
an effect greater
apex produced
individual
rhizome
treatments
(Figure
rhizomes
of only the shoot or rhizome
difference
in low lateral
S2 and S3 resulted
By contrast,
as in the control.
respect to the six ex-
trends with
very similar
exhibited
increased these effects,
that had had their shoots removed,
differences.
rhizome
of
pro-
The level to which these different
production
was cultivar
dependent.
OF APICAL
CONTROL
DOMINANCE
Materials
7.3.1
Five `standard
and Methods
explants'
of each of the cultivars
nor' and three for the cultivar
taining
Alstroemeria
combinations
i
propagation
`Butterfly'
medium,
`Valiant',
`Parade'
into
culture
were placed
supplemented
with
and Èleajars con-
the following
of PGRs.
0,0.01,0.10,1.00
l-'
10.00
mg
or
TIBA
+0 or 4 mg l-1 BAP.
94
100
90
0
80
ro
10
0
60
w
0
50
fJý
rý
40
C
N
30
20
10
0
Si
S2
S3
S4
S5
S6
Si
S2
S3
S4
Explant type
So,
S6
3 enlarged basal internodes + rhizome apex + shoots (control)
3 enlarged basal internodes + rhizome apex - shoots (not significant)
3 enlarged basal internodes - rhizome apex + shoots (not significant)
3 enlarged basal internodes - rhizome apex - shoots (p=0.01)
3- single enlarged basal internodes + shoots (p=0.001)
3 single enlarged basal internodes - shoots (p=0.001)
7.1: The effect of six explant
cultivar `Valiant'
Figure
rate of the
95
100
90
80
"r0
C
60
C
0
50
40
y
30
?0
10
0
Si
Si
S2
S3
S4
S5
S6
S2
S4
S3
Explant type
S5
S6
3 enlarged basal
3 enlarged basal
3 enlarged basal
3 single enlarged
3 single enlarged
Figure
internodes + rhizome apex - shoots (not significant)
internodes - rhizome apex + shoots (not significant)
internodes - rhizome apex - shoots (p=0.001)
basal internodes + shoots (p=0.01)
basal internodes - shoots (p=0.001)
cultivar `Parade'
rate of the
96
100
90
80
a)
%0
0
60
0
N
50
40
30
20
10
0
Si
Si
S2
S3
S4
S5
S6
S?
S3
S4
Explant type
S5
S6
3 enlarged basal
3 enlarged basal
3 enlarged basal
3 single enlarged
3 single enlarged
Figure
internodes + rhizome apex
(not
significant)
- shoots
internodes - rhizome apex + shoots (not significant)
internodes - rhizome apex
(p=0.001)
shoots
basal internodes + shoots (p=0.05)
basal internodes
(p=0.001)
- shoots
cultivar Èleanor'
rate of the
97
ii
or 0.440 mg l'
0,0.011,0.022,0.110,0.220
thidiazuron
mg 1-1 BAP.
+4
iii
0,0.04,0.10,0.20,0.40
iv
0,0.10,1.00,10.00
or 100.00 mg 1-1 GA3 +0
v
0,0.15,0.30,1.50
or 3.00 mg 1-1 paclobutrazol
or 1.00 mg 1-' NAA
irradiance
Color 29,65-85
(Section
2.5) and visual observations
recorded at intervals
(Section
ysed
either 6,7
x6
looking
the standard
produced,
because it was considered
were assessed
of the explants
were also
The data was analon the PGRS, of
for each cultivar.
Although
for changes in the number
methods
an
by Philips
provided
design, depending
or 12 replicates
were essentially
They were
cycle with
tubes. The cultures
of the quality
an experimental
or 10 treatments
eral rhizomes
daylength
of four weeks, over a 12 week period.
2.5), with
these experiments
1-'
BAP.
4
mg
or
+0
(120 µE m-2s-1),
20 Win-'
of approximately
or 4 mg 1-1 BAP.
(day/night)
hour
at 15°C and a 12/12
BAP.
+4I-'
were used for each cultivar.
Three jars of each PGR combination
incubated
and 0 mg l-1
thidiazuron
of lat-
of assessment were continued
that the PGRs could manifest
additional
changes
in the explants.
Results
7.3.2
7.3.2.1
General
None of the PGRs
lateral
rhizomes,
explant
quality
Root production
produced
shoots
any significant
or roots
were consistently
produced.
differences
In all instances,
growth
of
and
better when BAP was present in the media.
was severely or completely
inhibited
The degree to which these effects were exhibited
7.3.2.2
in the number
by the presence of BAP.
was cultivar
dependent.
TIBA
The presence of TIBA
out BAP, resulted
in the Alstroemeria
in only a slight
production
medium,
increase in the production
with or withof lateral
rhi-
98
This
zomes and shoots.
to be dependent
appear
between
ation
inhibition
of TIBA.
Root
both TIBA
containing
Rhizome
of TIBA.
vitrification
of the explants,
7.3.2.3
there
concen-
all treatments
`Valiant'
increasing
in growth
concenand some
This was especially
and `Butterfly'.
deterioration
the
and
no-
Due to
in the size and
was not repeated.
Thidiazuron
BAP
did not produce
always declined
with
as with
increasing
Thidiazuron
tions used, and for the cultivar
greater extent
(Table
the number
to inhibit
axillary
'Eleanor'
but
these differences
of lateral
of roots
rhi-
produced
At the high-
of thidiazuron.
was frequently
completely
less than BAP
root production
bud growth
without
at the higher
concentratested,
at all concentrations
produced
were not statistically
to a
in the pressignificant
7.2).
incidence
thidiazuron.
cultivar
TIBA,
than BAP. Fewer shoots were generally
ence of thidiazuron
medium
changes in the number
root production
appeared
it stimulated
conversely,
propagation
concentrations
of thidiazuron,
est concentrations
inhibited.
in Alstroemeria
any significant
However,
zomes and shoots.
The
with
and weaker
cultivars
this experiment
The presence of thidiazuron
but,
in virtually
concentrations.
the lack of response to the treatments
quality
treatment,
at the highest
production
became thinner
in the weaker growing
ticeable
was that,
observed
in the control
to deteriorate
appeared
at the highest
occurred
not
(Table 7.1).
and BAP
They
trend
was inhibited
production
and shoot quality
trations
of root
It did
and there was much vari-
The only consistent
the cultivars.
was always complete
inconsistent.
on the presence of BAP
of how many roots were produced
regardless
tration
response was, however,
of vitrification
increased
The lowest concentration
dependent.
ence of 0.1 mg l'
All of the cultivars
thidiazuron
with
inducing
increasing
concentrations
vitrification
exhibited
vitrification
and all were severely vitrified
appeared
of
to be
in the presat the highest
99
Table 7.1: The effect of TIBA and BAP on the numbers of lateral
rhizomes ,
shoots and roots prod uced in vitro by the cultivars `Valiant', `Parade', 'Butterfly' and Èleanor'
Cultivar
BAP
(mg1-i)
TIBA
Lateral
Shoots
Roots
(mg1-'-)
rhizomes
0.2
4.1
0.2
0.00
Valiant'
0.0
Valiant'
4.0
'Parade'
0.0
`Parade'
4.0
'Butterfly'
0.0
'Butterfly'
4.0
Eleanor'
0.0
'Eleanor'
4.0
0.01
0.10
1.00
10.00
0.00
0.01
0.10
1.00
10.00
0.1
0.3
0.5
0.4
0.6
0.6
0.7
0.8
0.9
4.1
4.1
4.1
4.3
4.3
4.6
4.4
4.6
4.9
0.4
0.4
0.0
0.0
0.0
0.0
0.1
0.0
0.0
0.00
0.01
0.10
1.00
10.00
0.00
0.01
0.10
1.00
10.00
0.1
0.3
0.2
0.1
0.1
0.6
0.7
0.9
0.9
1.0
3.8
4.0
4.1
3.9
4.3
4.7
4.5
4.5
4.4
4.5
0.2
0.3
0.3
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.00
0.01
0.10
1.00
10.00
0.00
0.01
0.10
1.00
10.00
0.0
0.1
0.1
0.1
0.2
0.3
0.2
0.1
0.1
0.2
4.2
4.4
4.0
4.3
4.3
4.5
4.4
4.0
4.3
4.3
0.1
0.1
0.0
0.0
0.0
0.0
0.0
0.1
0.0
0.0
0.00
0.01
0.10
1.00
10.00
0.00
0.01
0.2
0.4
0.6
0.4
0.5
0.2
0.5
4.4
4.3
4.4
4.1
4.4
5.1
4.9
0.8
0.5
0.6
0.2
0.0
0.0
0.0
0.10
0.6
4.7
0.0
1.00
0.4
5.1
0.0
10.00
0.7
5.3
0.0
No differences
significant
100
Table 7.2: The effect of thidiazuron on the numbers of lateral rhizomes,
shoots and roots produced in vitro by the cultivars `Valiant', `Parade', `Butterfly' and Èleanor'
Cultivar
`Valiant'
BAP
(mgt-1)
Lateral
Shoots
Roots
0.000
0.011
0.022
0.110
0.220
0.440
0.000
rhizomes
0.6
0.4
0.5
0.6
0.9
0.8
0.6
4.3
4.0
4.0
4.5
4.6
4.3
4.5
0.4
0.2
0.3
0.1
0.1
0.0
0.1
0.000
0.6
4.3
0.5
0.011
0.6
4.1
0.3
0.022
0.7
4.3
0.3
0.110
0.220
0.7
0.7
4.1
4.3
0.6
0.2
0.440
0.9
4.2
0.1
0.000
0.6
4.4
0.1
0.000
0.011
0.022
0.110
0.220
0.440
0.3
0.3
0.2
0.3
0.3
0.2
4.4
4.4
4.0
4.1
4.0
4.4
0.6
0.3
0.1
0.1
0.0
0.0
4.0
0.000
0.4
4.3
0.0
0.0
0.000
0.011
0.022
0.110
0.220
0.440
0.000
0.9
0.9
1.1
1.2
1.1
0.9
0.7
4.7
4.6
4.0
4.3
4.5
4.7
5.1
0.9
0.7
0.2
0.0
0.0
0.0
0.0
0.0
4.0
`Parade'
0.0
4.0
`Butterfly'
Èleanor'
0.0
4.0
Thidiazuron
(mgl-i)
No differences
significant
101
Again, due to the poor response to the treatments
concentration.
and the
deterioration in the quality of the explants, this experiment was not repeated.
7.3.2.4
NAA/BAP
The addition of NAA to Alstroemeria production
medium containing
did not affect lateral rhizome or shoot production.
However, there appeared
BAP
to be more roots at the highest concentration of NAA in the cultivars `Valiant'
(Table
`Parade'
7.3). There were no differences in the appearance of the
and
explants, for any of the cultivars in any of the treatments.
This experiment
was not repeated.
7.3.2.5
GA3
The presence of GA3 in Alstroerneria
BAP,
often
to reduce
appeared
shoots and roots produced
Vitrification
As the concentration
to become longer
at the highest
occurred
of GA3 was increased,
of the explants
experiment
of lateral
rhizomes,
of GA3 was increased,
and for the
and thinner
in the presence of 0.1 mg l-1 GA3
malformed
dependent
at the highest
but independent
7.4).
there was a tendency
and for the rhizome
and thinner
concentration
(Figure
or without
of the
in the medium.
tested,
most of the lower concentrations
extended
with
(Table 7.4). None of these re-
appearing
These effects were cultivar
of BAP
concentration
numbers
As the concentration
some of the explants
concentrations.
medium,
for shoots to become longer
there was a tendency
and above, with
the
slightly
in all of the cultivars
sults were, however, significant.
rhizome to elongate.
production
to elongate.
the shoots were shorter
and the rhizome
also appeared
Once again, due to the deterioration
and the apparent
lack of response
than
for shoots
However,
those at
to be less
in the quality
to the treatments,
this
was not repeated.
102
Table 7.3: The effect of NAA and BAP on the numbers of lateral rhizomes,
shoots and roots produced in vitro by the cultivars `Valiant', `Parade', 'Butterfly' and Èleanor'
Cultivar
`Valiant'
`Parade'
`Butterfly'
Èleanor'
BAP
NAA
Lateral
(mg 1-1)
(mg l-1)
4.0
0.00
0.04
0.10
0.20
0.40
rhizomes
1.1
0.7
0.6
0.7
0.9
4.7
4.3
4.5
4.3
4.3
0.0
0.0
0.1
0.1
0.1
1.00
0.6
4.3
0.3
0.00
0.5
4.3
0.0
0.04
0.9
4.5
0.1
0.10
0.7
4.3
0.0
0.20
0.6
4.4
0.2
0.40
1.00
0.6
0.6
4.4
4.2
0.1
0.2
0.00
0.04
0.10
0.20
0.7
0.5
0.5
0.7
4.3
4.0
4.2
4.2
0.0
0.0
0.0
0.0
0.40
0.7
3.9
0.0
1.00
0.3
4.1
0.0
0.00
0.4
4.8
0.0
0.04
0.5
5.2
0.0
0.10
0.20
0.40
0.8
0.4
0.7
4.8
4.9
4.9
0.0
0.0
0.0
1.00
0.6
4.9
0.0
4.0
4.0
4.0
No differences
Shoots
Roots
significant
103
Table 7.4: The effect of GA3 and BAP on the numbers of lateral rhizomes,
shoots and roots produced in vitro by the cultivars `Valiant', `Parade', `Butterfly' and Èleanor'
Cultivar
BAP
(mg l-')
`Valiant'
0.0
`Valiant'
4.0
`Parade'
0.0
`Parade'
4.0
`Butterfly'
0.0
`Butterfly'
4.0
Èleanor'
Èleanor'
0.0
4.0
GA3
(mg 1-i)
0.0
0.1
1.0
10.0
100.0
0.0
0.1
1.0
10.0
100.0
Lateral
Shoots
Roots
rhizomes
0.4
0.2
0.3
0.5
0.3
0.5
0.5
0.4
0.4
0.5
4.3
4.2
4.1
4.1
4.1
4.6
4.4
4.4
4.5
4.5
0.6
0.5
0.2
0.1
0.1
0.2
0.1
0.1
0.0
0.0
0.0
0.1
1.0
10.0
100.0
0.0
0.1
1.0
10.0
100.0
0.2
0.1
0.1
0.1
0.1
0.6
0.3
0.5
0.2
0.4
4.1
4.0
4.1
4.1
4.3
4.4
4.4
4.2
4.1
4.4
0.6
0.3
0.1
0.1
0.1
0.2
0.0
0.0
0.0
0.0
0.0
0.1
1.0
10.0
100.0
0.0
0.1
1.0
10.0
100.0
0.3
0.0
0.1
0.2
0.1
0.6
0.4
0.3
0.3
0.1
4.1
3.9
3.6
3.8
3.5
4.2
4.1
4.0
4.0
3.7
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.1
0.6
0.1
4.3
4.2
0.9
0.7
1.0
0.5
4.3
10.0
0.7
4.2
0.0
0.1
100.0
0.0
0.1
0.4
0.7
0.8
4.3
5.3
5.2
0.0
0.1
0.0
1.0
0.8
5.1
0.0
10.0
100.0
0.9
0.9
5.1
5.0
0.0
0.0
No differences
significant
104
Figure 7.4: The effect of GA3 on the morphology
of rhizome explants of the
1-'
1-1
GA3,
BAP
A-C=0.0
0.0,1
100
Èleanor'.
+
and
mg
mg
cultivar
.0
Bar
D-F=4.0
mg 1-1 BAP + 0.0,1.0 and 100 mg 1-1 GA3, respectively.
=1cm
105
Paclobutrazol
7.3.2.6
Although
treatments
The number of shoots produced
increased as the concentration
for the cultivars
zol was increased
BAP, and the number
also showed similar
some slight trends were apparent.
were not significant,
of lateral
`Valiant'
rhizomes
The number
trends.
the presence of BAP. The cultivars
and `Parade',
of roots produced
and `Parade'
decreases in root number with increase in paclobutrazol
absence of BAP
Paclobutrazol
out BAP
in the medium
(Figure
length
concentrations
those produced
was accompanied
zome the appearance
the morphology
on the control
the number
in rhizome
length.
and leaf size decreased
expansion
media.
The reduction
This
of the explants,
in shoot
treatments
in the media also
as the concentration
any significant
com-
gave the rhi-
was considerable
shoots and roots produced,
marked changes in the morphology
concentra-
or elongation,
Paclobutrazol
There
of the roots.
rhizomes,
with or with-
however, the paclobutrazol
did not produce
paclobutrazol
of lateral
in the
concentration
by an increase in its diameter.
the roots and a decrease in root length
Although
also showed slight
At the highest
of paclobutrazol.
of being shorter,
had caused no difference
affected
`Valiant'
was always less in
morphology,
Shoot length
7.5).
tion, the leaves and shoots showed very little
pared with
and without
7.5).
had a very marked effect on explant
increasing
with
(Table
with
in the cultivar
produced
`Valiant'
of paclobutra-
swelling
of
was increased.
results
as regards
due to the very
this experiment
was re-
peated.
7.4
7.4.1
DISCUSSION
Mechanical
Control
of Apical
Dominance
Pierik (1987) states that it has been known for many years that removal of the
apical meristem releases axillary buds from the effects of apical dominance.
However, in the case of Alstroemeria there are only two axillary buds on an
106
Table 7.5: The effect of paclobutrazol and BAP on the numbers
of lateral rhizomes, shoots and roots produced in vitro by the cultivars `Valiant', `Parade',
`Butterfly' and Èleanor'
Cultivar
`Valiant'
`Valiant'
BAP
(mg 1-1)
0.0
4.0
`Parade'
0.0
`Parade'
4.0
`Butterfly'
`Butterfly'
Èleanor'
Èleanor'
0.0
4.0
0.0
4.0
Paclobutrazol
(mg 1-1)
0.00
0.15
0.30
1.50
3.00
Lateral
Shoots
Roots
0.00
0.15
0.30
1.50
3.00
rhizomes
0.2
0.2
0.2
0.4
0.4
0.4
0.5
0.6
0.8
0.7
4.1
4.5
4.3
4.7
4.6
4.6
4.8
4.9
4.9
5.0
1.1
1.3
1.5
0.9
0.8
0.2
0.5
0.7
0.5
0.5
0.00
0.15
0.30
1.50
3.00
0.00
0.15
0.30
1.50
3.00
0.1
0.1
0.1
0.1
0.1
0.5
0.5
0.4
0.8
0.4
4.3
4.3
4.4
4.4
4.5
4.6
4.7
4.7
5.2
5.1
0.8
0.7
0.4
0.5
0.5
0.1
0.5
0.4
0.4
0.4
0.00
0.15
0.30
1.50
0.2
0.1
0.1
0.1
4.2
4.4
4.3
4.4
0.3
0.4
0.5
0.1
3.00
0.2
4.2
0.3
0.00
0.15
0.30
1.50
3.00
0.1
0.6
0.6
0.4
0.3
4.1
4.4
4.4
4.5
4.5
0.0
0.0
0.0
0.0
0.1
0.00
0.15
0.30
0.3
0.2
0.1
4.4
4.2
4.2
1.0
1.2
1.2
1.50
0.2
4.1
1.2
3.00
0.00
0.15
0.30
1.50
3.00
0.2
0.4
0.3
0.2
0.4
0.3
4.2
4.1
4.2
4.2
4.1
4.0
1.1
0.0
0.1
0.1
0.1
0.2
107
Figure 7.5: The effect of paclobutrazol
on the morphology of rhizome explants
A-C=0.0
of the cultivar Èleanor'.
mg 1-1 BAP + 0.0,0.3
and 3.0
D-F=4.0
mg 1-1 paclobutrazol,
mg l-1 BAP + 0.0,0.3
and 3.0 mg l-1
paclobutrazol,
respectively. Bar =1 cm
108
aerial shoot, one that continues
has the potential
which
There
system.
the growth
of the main rhizome
to grow out and produce
are also only two types of apices present,
of the aerial shoots and those at the distal
Therefore,
in common
1980), Alstroerneria
for axillary
potential
branching
with
of the rhizome
those at the tips
ends of rhizomes
most monocotyledonous
has a low number
of axillary
bud proliferation
is limited.
and another
plants
(Section
1.2.2).
(Hussey
et al.,
buds and consequently
From the results presented it would appear that these axillary
the
buds are influ-
enced by both the rhizome and shoot apices. Removal of either of these apices
a low increase in axillary
produced
apices significantly
far greater
increased
lateral
than the additive
This suggests that
bud outgrowth.
rhizome
if one apex source is removed,
bud growth
(Roberts
and Hooley,
mechanism
has been proposed
al., 1975).
However,
likely
considered
and Damson,
inhibition
of Agropyrori
by directing
buds towards
over ax-
repers (Leakey
signal is probably
et
the least
Apices are also
the movement
themselves
effect.
1987) and a similar
which may be occurring.
to effect apical dominance
1977; McIntyre
the other may be able to
correlative
an increase in a chemical
lites away from the axillary
of the apices separately.
1988; Tamas,
in rhizomes
of the changes in mechanism
and the effect was
the level of its own dominance
The shoot apex has been shown to maintain
illary
production,
effects of the removal
for this loss, by increasing
compensate
However, removal of both
(McIntyre,
of metabo1969,1972,
1988).
Therefore, for Alstroemeria in vitro there would appear to be a two part system composed of shoot and rhizome apices, both competing for the nutrients,
of which most are supplied by the media. Hence, when one is removed, the
other may be able to direct more of the resources towards itself, with only
a proportion
axillary
of what could have been made available being directed into
bud growth.
This would account for the small increases in lateral
rhizome production observed when only one type of apex was removed.
The further increases reported after subdivision of the rhizome explants into
109
single enlarged basal internodes, suggests another complexity
anism of inhibition
in the mech-
bud growth in Alstroemeria.
of axillary
considered to be a competitive
or inhibitory
This may be
effect, produced between the
expanded basal internodes themselves. It has already been established, that
each shoot will be competing for nutrients
and thereby inhibiting
axillary
bud growth, yet even when the shoots have been removed, the level of latis still not as high as when the shoots are removed
eral rhizome production
and the expanded basal internodes are separated. Therefore, any effect of the
shoot apices can essentially be disregarded. It is possible that, as the axillary
buds are released from inhibition
of growth, they begin to interact with one
another, as each tries to establish dominance over the others. Consequently,
explants that consist of several enlarged basal internodes, are seen to produce
fewer lateral rhizomes compared with single enlarged basal internodes.
Chancellor
similar
(1974),
It was demonstrated
results.
creasingly
fragments
smaller
of Agropyron
on the rhizome
working
that
more axillary
repens, reported
buds grew from in-
when released from the dominance
of rhizome,
effect of the apex. This, it was suggested, was due to the lack of competition
from or dominance
multi-node
the apex.
by, any nearby axillary
fragments
However,
many axillary
of dominance
that remained
buds may start to grow after removal
of
This effect was attributed
growing.
over the majority
in active growth.
the fewer the number
the greater
the multiplication
of the axillary
However,
in that
study,
of one single shoot were used, this was a mixture
consisting
rhizome
clear whether
some with
buds and sometimes
explants
with
and some without
buds by those
of shoots present on a rhizome
rate.
to the es-
(1988)
found
al.
also
with
et
Pierik
meria that
axillary
on
a few days only one, or very few, ancillary buds
within
were still seen to be actively
tablishment
buds. It was also shown, that
a rhizome
fragment,
when explants
of explants
with
It
was also not made
apex.
more than one shoot were similar
a rhizome
Alstroe-
mixtures
of
apex.
Between the cultivars used in the present study, differences could be seen
in the overall trends when the shoots remained on the explant.
This was
110
true of the cultivar
especially
are known
`Valiant'
to produce
lateral
expected number
of lateral
at subculture
by the directed
multiplication
`Valiant'
inherent
are caus-
weak growth,
than would have been expected,
This
them.
in vitro,
are reflected
may influence
this
due to their
be
produced
may
and `Parade'
those of the cultivar
if the shoots of the cultivar
of metabolites
are reaching
the explants
If these characters
to the apices,
Consequently,
rhizomes
nutrients
in vivo, whereas
Èleanor'
seems to be caused, to an extent,
of metabolites
ing less redirection
shoots
weaker.
then as apical dominance
rates in vitro.
The cultivars
strong
are somewhat
movement
`Valiant'.
more
as more
could be the reason for the higher
than
by the cultivar
`Valiant',
with
of single enhirged basal internodes
with
rhizomes
produced
consisting
shoots.
between the cultivars
difference
Another
orous in vitro
higher
produced
the treatments
was that those which are more vig-
numbers
of lateral
It is possible that
provided.
the weaker cultivars
lateral
levels
the
achieved
same
of
rhizome
sessed over longer periods of time.
Hence, this observation
different
the
of
be a reflection
This
strong
apical
dominance
especially
if the low amount
purposes,
is considered
rhizome
production
of apical
this experiment
apical dominance
each system
within
if they had been as-
production,
dominance
rhizome
the high number
material
Co., personal
in vivo,
for propagation
of potential
after the two year period
in vivo.
can not necessarily
in Alstroemeria
differ.
may
However,
sites for lateral
a plant
spends
in vivo, as movement
In vivo translocation
of metabolites
Therefore,
it may be that
is from the medium
in vitro, nutrients
to a consideration
of metabolites
the
from
produced
of metabolites
in a
The
communication).
the results
be extrapolated
the shoots and down into the rhizome
movement
to
was considered
does seem to be reflected
of suitable
Horticultural
could have
between these numbers can then be regarded as reflecting
large disparity
strength
present
to
rates of the cultivars.
in vitro
against
bed (Parigo
production
growth
in response
rhizomes
of
within
is essentially
and roots, whereas in vitro the
to the shoots via the rhizome.
reach the axillary
buds on the
111
being
directed
to
way
towards
the shoots rather
taken place. If this is so, then it may influence
than
after redirection
has
the degree of apical dominance
occurring within the two systems.
Chemical
7.4.2
7.4.2.1
Control
of Apical
Dominance
TIBA
The absence of any effect of TIBA
duced in Alstroemeria
is supported
of lateral
by work on Hippeastrum
rhizomes
hybridum
1983), where it was found that soaking bulbs in solutions
tacharjee,
had no effect on the number
(Woodward
distichum)
caused the number
total
on the number
(Lolium
grass
in tillering
tillers
The addition
multiflorum)
(Marks
Acer
1988)
son,
and
species
following
shoots
more
shoots produced
of TIBA
application
to the culture
for rye-
medium
and Dale, 1981) also produced
that were not significant.
significantly
of TIBA
to increase but did not increase the
of TIBA
(Dalton
increases
By contrast,
Senecio x hybridus
and Wiltshire,
1984) in vitro,
the application
of TIBA.
were of inferior
in the Acer cultures
(Bhat-
(Hordeum
For spring barley
1988), a foliar
and Marshall,
of elongating
of tillers.
number
of bulbs produced.
pro-
quality
(Gerts-
produced
However,
the
for subsequent
culture.
Van Aartrijk
formation
Flint
and Blom-Barnhoorn
of Lilium
and Alderson
(1986) found that fewer bulblets
when TIBA
It appears therefore,
rates of plants vary greatly,
tem employed,
reported
increases in bulblet
speciosum in vitro, in the presence of TIBA.
cissus chip propagules
system.
(1983,1984)
as differences
was applied
from
in a conventional
that the effects of TIBA
depending
were formed
Conversely,
Nar-
chipping
on the multiplication
on the plant being used and the sys-
may be seen between results produced
in vivo
and in vitro.
112
7.4.2.2
Thidiazuron
Phenylurea
derivatives
with
been used successfully
cytokinin
activity,
systems,
mainly
has been used with several ornamental
Sorbus aucuparia
(Kerns
x freemanii
1986), azaleas (Rhododendron
flora (Einset
1982). Higher
Thidiazuron
(Chalupa,
and Kerns,
et al., 1988), Syringa x hyacinthi-
1984) and apple (Malus
has also been used with
(Nieuwkerk
domestica)
N-(2-chloro-4-pyrimidyl)-N'(Ohyama
alba
Morus
have been achieved compared
rates of proliferation
Tilia
1987), Acer
(Meyer
1986), Celtis occidentalis
et al., 1986; Wang et al., 1986). The compound
(4PU)
plants.
in
within
tree species, including
pseudoacacia
)
sp. (Briggs
and Alexander,
phenylurea
woody
and fruit
and Robinia
and Meyer,
with
have
thidiazuron,
in the last few years to increase proliferation
vitro shoot multiplication
cordata,
including
and Oka,
those
with
for most cytokinins.
Application
Stefani,
of thidiazuron
(Cucumis
1989) and to muskmelon
to produce
comparatively
few reports
donous plants-. When
duced the formation
less vigorous
than
and van Staden,
thidiazuron,
of work
applied
applied
thidiazuron
adventitious
those produced
1988).
did not increase the number
with
Recently,
as a solution
on BAP
and
et al., 1989) failed
cultivars.
on other
to the corms of Ixia flexuosa,
of multiple
(Banko
Simi-
of shoots produced.
by the Alstroemeria
shoots or roots produced
arboreum
melo) (Niedz
increase in the number
any significant
larly, in the present study, thidiazuron
rhizomes,
Oxydendrum
to the tree
of lateral
There are
monocotyle-
thidiazuron
in-
buds. However, these buds were
supplemented
medium
(Meyer
Henny and Fooshee (1990) reported
to the base of Alocasia plants,
that
significantly
increased the number of basal buds. However, most of these buds were formed
beneath the substrate
penetrated
surface and after 12 weeks only a small proportion
had
the surface.
Read et al. (1987) found that dipping plant material in thidiazuron was
more effective than having it present continuously in the medium. This was
attributed
to the high activity
of the compound, which they found to be
113
deleterious
7.4.2.3
The
to plant
growth
with
prolonged
exposure.
BAP/NAA
absence of any effect of auxin
contrasts
been enhanced
for Plarctago
ium species (McComb,
1985) following
in the culture
and auxin
(Barna
ovata
and Wakhlu,
results
al., 1984) and several species in the bromeliad
ads in vitro is often very variable,
homogenous
(Pierik,
even if the starting
.
does, however, support
(1985)
Dale
who found that
and
(Lolium
grass
multilorum)
medium
cytokinin.
7.4.2.4
material
et
et al.,
rate for the
of bromeli-
appears to be
personal communication).
The present result with Alstroemeria
with
with
the synergis-
Vriesea. However, it should be noted that the reaction
bromeliad
of Dalton
genus Aechmea (Dijck
and auxin on the increase in multiplication
tic effect of cytokinin
cytokinin
have been achieved
(1987) also reported
1974). Pierik
1988; Jones and Murashige,
of both
Costus speciosus (Chaturvedi
species, including
some monocotyledonous
has
1988) and Stylid-
the incorporation
Similar
medium.
rhizomes
Shoot multiplication
the results of several other reports.
with
lateral
of
on the production
the rate of tiller
by
the addition
affected
was not
the observations
induction
in rye
to the
of auxin
GA3
Catalano
and Hill
GA3 may promote
cal dominance.
Alstroemeria
(1969)
the action of kinetin
However,
cultivars
rate of the rhizome
and Sachs and Thimann
on releasing axillary
when GA3 was applied
in vitro,
explants
(1964)
no significant
with
suggested
that
buds from api-
or without
BAP
to
in
the multiplication
changes
were observed.
The application of GA3 onto plants of English ivy (Hedera helix) (Lewnes and
Moser, 1976; Frydman and Wareing, 1973) produced significant increases in
axillary bud growth and subsequent branching of the plants. The addition of
GA3 to the culture medium for embryos of American lotus (Nelurnbo lutea)
114
(Kane et al., 1988) has been shown to produce significant
growth
The
and node number.
GA3
also stimulated
which was not seen to occur in the control
GA3 has now been applied
tempts
to hasten their
(Furutani
g2ber offccinale)
hibited
longa) (Randhawa
(Curcuma
icant differences
height
in plant
(Hordeum
barley
on spring
1986), following
and Mahey,
or tiller
distichum)
(Woodward
of elongating
bud growth.
of the bulbous
A similar
treatment
in bulb
caused a reduction
sults have been reported
both bulblet
(Pierik
7.4.2.5
yield
(Halevy
for Easter
ex-
addition
orientalis,
and Marshall,
tillers
of GA3
1988) has
and to restrict
Iris cultivar
and Shoub,
(Lilium
no signif-
application
tiller
`Wedgewood',
Similar
1964).
(Zieslin
longiflorum)
of GA3 to the culture
and bulblet
regeneration
lily
1984) exhibited
reand
of GA3 caused no change in stem length.
1988), where application
In Hyacinthus
GA3 application,
Foliar
number.
been seen to reduce the number
Tsujita,
Field grown ginger (Zin-
decreases
in rhizome yield, whereas
emergence
and
of shoot
inhibition
tumeric
crops in at-
monocotyledonous
and increase yields.
Nagao,
and
branching,
rhizome
treatment.
to field grown,
growth
increases in rhizome
inhibited
medium
weight on excised bulb scale segments
1975).
and Steegmans,
Paclobutrazol
The ability
of paclobutrazol
grown tulips
and lilies, producing
been well established
1982,1982/3).
as potted
(Hanks
Application
cause more reduction
placing
and other compounds
more compact
to retard the growth
and manageable
1983; Menhenett
and Menhenett,
make no mention
the treated plants.
et al., 1982,1986),
plants,
and Hanks,
leaf
length,
length
flower
the
than
the
of
of
stem
(Berghoef
them
1990). However,
and Zevenbergen,
of any effect on the growth
has
to freesias has been shown to
of paclobutrazol
the flowers too close to the leaves and making
plants
of pot
and development
thereby
unmarketable
these reports
bulbs
the
of
of
When applied to the grass Lolium perenne (Hebblethwaite
paclobutrazol
effect was very variable.
This
changed
the amount
was considered
of tillering
but the
to be due to effects of the
115
environment, as these trials were conducted in the field.
by
been
have
in
the stimrates of shoot systems
enhanced
vitro
Multiplication
bud development
of axillary
ulation
(Ziv
in Aechrnea fasciata
(McKinless
similar
This
de novo.
plant
to that
by decreasing
Enhanced
in vitro.
production
In contrast
1989,1990).
of a short rhizome,
has been used as part
has also been achieved in liquid
(Ziv,
oicinalis
1982) by
cultures
cormlet
from which
pro-
roots were
for increasing
of gladiolus
production
paclobutrazol
with
supplemented
Khunachak
of Asparagus
rosea
shoot elongation,
of a protocol
to these results,
observed no changes in shoot growth
and
In Lapageria
et al., 1986) by paclobutrazol.
et al., 1988) paclobutrazol,
duced a structure
rooted
(Chin,
(a-cyclopropyl-a(4-methoxyphenyl)-5-pyrimidine-methanol)
ancymidol
initiated
in Asparagus
(1987)
et al.
following
officinalis
appli-
cation of paclobutrazol.
With
Alstroerraeria,
had no effect on the rhizome multiplication
paclobutrazol
in
however,
the
shoot and root morphology
changes
rate,
be of benefit prior to the planting
material.
out of propagated
has also been shown to increase root size in Asparagus
1987) and to promote
1985). If paclobutrazol
mani and Poovaiah,
medium
tuber growth in the potato
of Alstroemeria,
leaf morphology,
ing transpiration,
then
during
Other effects of paclobutrazol
in stomatal
conductivity
in increasing
the weaning
(Solarrum
Paclobutrazol
(Khunachak,
(Bala-
tuberosum)
changes in root,
water uptake
and establishment
on the water use of plants,
(Atkinson,
1990), could have important
officinalis
may
be
to
added to the rooting
were
the subsequent
be
important
could
which occurred
1986) and epicuticular
roles to play in the weaning
shoot
and
and decreas-
of plants
ex vitro.
including
changes
wax (Smith
et al.,
and establishment
of plants.
7.5
CONCLUSION
It would appear that the shoot apices and the root apex exert a very strong
dominance
effect in vitro on the second axillary
bud of the shoots of Alstroe-
116
bud
This
is the one which can grow into a lateral rhizome and
meria.
axillary
is the only other axillary bud on a shoot, apart from the one which carries
on the growth of the main rhizome.
inhibit
These axillary
buds may interact and
the growth of each other.
These conclusions are supported by the
fact that the highest multiplication
rate was achieved only when both types
of apex were excised and the expanded basal internodes subdivided.
With
the rhizome apex being recultured, essentially one more plant was produced
in each of the treatments where it was removed.
Attempts
to control
BAP, produced
especially
the rhizome explants
bud growth,
present
controlled
Further
work
working
in Alstroemeria
Investigation
no significant
is therefore
effects of cytokinins,
effects on the multiplication
and maintained
by the
rate of
a high degree of inhibition
of
by the apices, the mechanism
understood.
the dominance
needed to elucidate
and to assess the effects of a wider
of the vitrification
methods
in Alstroemeria
reported
in vitro. This may indicate
of which is not yet fully
to establish
dominance
from
PGRs,
the previously
of
apart
application
axillary
the apical
which occurred
to circumvent
mechanisms
range of PGRs.
in the present study, in order
this problem,
would also be useful.
117
Chapter
SUMMARY
8:
AND
CONCLUSIONS
8.1
GENERAL
Two main areas of interest were considered in this thesis.
The first was
factors on the growth of the
the assessment of the effects of environmental
rhizome of Alstroemeria in vivo and in vitro.
Clear differences
morphology
vitro.
were seen between the cultivars
and in their
These differences
responses to environmental
have been considered
possessed by the various parental
adaptations
programmes
of the cultivars.
Temperature
and irradiance
plant parts produced
had little
but little
by (i) changes in reaction
temperatures
in the breeding
effects on the dry weight of
Changes in daylength
The changes in dry weight
in the rate of photosynthesis
rates within
and
the plants
produced
caused by the different
and (ii) changes in the total light energy received by the plants,
due to the variation
profound
studied.
in vivo and in
the characters
species included
effect on their number.
to be due to alterations
factors
to reflect
in vivo had significant
effect on any of the parameters
were thought
used in this study, in their
in irradiance
and daylength.
However,
daylength
had a
effect on the time of flowering.
The results from the work in vivo indicated that for maximum rhizome production a temperature of between 13 and 18°C, a high irradiance and a short
daylength are required. However, as the latter two tend to be inhibitory
to
flowering, high summer irradiances are usually reduced by shading the plants
daylength
is often maintained at about 12 hours.
the
and
118
temperature
the parameters
daylength
in vitro produced significant
apart from that
studied,
to the change from
was attributed
Very low irradiances,
of nutrition.
It was considered
factor
more important
light
the
of
rate of the rhizome
for the culture
requirements
irradiance
Initially
the important
rhizome
and tubers,
if no tubers
the plants
failed
Con-
of a good
the
shoots,
of 15°C, an
of no more than 8 hours in a
This
growth.
habitats,
any physical
`splits'
the
when
that
Further
nature
This phenomenon
that
may
all of
contained
a
work in vitro, showed that
could cause dramatic
factor
of this
is still,
however,
could be linked to the plant's
for phases of fast, active
of the
It was also
were planted,
the tubers
when added to the medium,
The
damage
for planting.
of `splits'
suggested
showed that
to be the condition
appeared
regarding
the establishment
however,
work,
growth,
a
need
in order to become
after periods of dormancy.
Overall, the study on the effect of temperature,
Alstroemeria
a similar
may be the
of healthy
was influencing
for plant establishment.
of speculation.
re-established
process
were present
from the tubers,
in its native
to assess which
were a temperature
Later
the preparation
to establish.
increases in shoot
matter
of the shoots.
by the explant.
received
and for production
material.
particularly
during
factor important
mode
environment.
environment
plant
in this
noted that
extracts
integral
that temperature
potted
factor
have occurred
to a heterotrophic
cycle.
it was thought
in vivo of newly
This
have
produced
may also
of at least 5W m-2 and a daylength
24 hour day/night
in vitro.
it is suggested that for maintenance
From the in vitro investigations,
multiplication
and
caused etiolation
it is difficult
due to this interaction,
sequently,
however,
light
the total
Irradiance
in any parameter
an autotrophic
daylength
that a shorter
effect, as it influences
of root production.
differences
no significant
produced
responses for all of
showed that
the optimum
temperature
in vivo and in vitro, on
for growth
is approxi-
mately the same in both systems. However, when comparing the effects of
119
irradiance
between the in vivo and in vitro systems,
and daylength
differences can be seen in the requirements
for growth.
of lateral rhizome growth
The second area of interest was the inhibition
It has been clearly demonstrated
by apical dominance.
inhibitory
very
strong
and shoot apices exert
lateral rhizomes. An interaction,
marked
that the rhizome
controls on the growth of the
also occurs between
probably competitive,
buds, with a tendency for one or a few to become dominant
the axillary
and inhibit the growth of the others. The greatest multiplication
rate of the
rhizome was achieved when the rhizome and shoot apices were removed and
the enlarged basal internodes were subdivided.
Attempts
to control
apical
dominance
with
PGR. s produced
responses. This suggests, that either the method
for Alstroemeria
was not appropriate
dominance
mentioned
of the operator,
plants subcultured
by causing
per unit of working
by an increase in multiplication,
If a chemical method
system
the PGR was not too expensive,
8.2
required
should
to that
may decrease
in the number
of ex-
if this is not offset
Consequently,
such a change would
were able to produce
of the micropropagation
rate of Alstroemeria
a reduction
time.
previously.
in the multiplica-
improvements
substantial
of apical
for Alstroemeria
practices
However, the extra manipulations
tion rates achieved.
the efficiency
of application
than has been considered
a change in subculturing
above, could produce
of the PGRs
in vitro or that the mechanism
in the plant is more complex
Commercially,
no significant
not be cost effective.
the same effect then the efficiency
not be affected
a profitable
and providing
that
increase in the multiplication
could be achieved.
SUGGESTIONS
FOR FUTURE
WORK
Commercially, there may be some value in establishing the minimum amount
of light required to give a good multiplication
cost of the lighting.
rate, in order to minimise the
As this would be considering the total light energy
received, determining the minimum time necessary for its accumulation
may
12
be
also
of value.
The effect of light quality
studied and there appear to be no reports
As the quality
Alstroemeria
the growth
of the explant
ing', is worth
of PGRs to the explants
generating
problems
to result from prolonged
ing PGRs to influence
a plant
may initiate
and
trials,
buds, rhizome
the lateral
buds themselves,
teractions
would lead to a better
the required
it will
of us-
be necessary to carry
characters,
e. g.
have been modified.
appears to have complex
interac-
between
the
and
shoots,
and
apices
a more fundamental
appreciation
of the rhizome
effect,
As a consequence
to see if any of the plant's
which
i. e. `puls-
medium,
which are often considered
to some PGRs.
of explants,
such as Alstroemeria,
with the multiplication
in this area for
rate of the rhizome
production
such as vitrification,
the growth
tions between the lateral
to many morphogenetic
information
flower colour or time to flowering,
morphology,
With
Alstroemeria
exposure
and flowering
on this interaction.
for short periods of time and then re-
Such an approach
studying.
was not
in general.
placing them on unsupplemented
out growth
development,
aspects of plant
may help to enhance the multiplication
The application
without
in the literature
to be fundamental
of light is thought
and physiological
of Alstroemeria
multiplication
on rhizome
understanding
of the limitations
of these inassociated
and how they may be overcome.
t2 t
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Appendix
A:
Skoog (MS)
Formulation
Revised
Stock
concentration
(g1-1)
44.0000
CaCl2.21l O
KNO3
and
Medium
Stock
solution
Murashige
of
Volume of stock
solution for 11
(ml)
of medium
10
Final
concentration
(mg1-')
440.000
76.0000
25
1900.000
165.0000
17.0000
37.0000
2.2300
0.6200
0.8600
0.0250
0.0025
0.0830
0.0025
-9.7850
3.7250
10.0000
10
10
10
10
10
10
10
10
10
10
10
10
10
1650.000
170.000
370.000
22.300
6.200
8.600
0.250
0.025
0.830
0.025
27.850
37.250
100.000
Glycine
0.2000
10
2.000
Nicotinic acid
Pyridoxine-HCl
Thiamine-1ICI
0.0500
0.0500
0.0100
10
10
10
0.500
0.500
0.100
NH4ti O3
KH"2PO4
MgSO4. HO
MnSO IH
4. 10
H3BO3
ZnSO4. H
1O
Na2Mo04.2HzO
CoC12.614,0
KI
CuSO4.511
10
FeSO4.711,O
Na-0EDTA
Inositol
Na2EDTA
- ethylenediaminotetraacetic
Other components:
From Murashige
sucrose 30gl-1
acid, disodium salt.
(Difco
and agar
Bacto)
10gl-1
and Skoog, 1962.
142
Appendix
Production
B:
Formulation
Alstroemeria
of
Medium
All the components, methods of formulation
and storage, are the same as in
MS, except for the concentrations of the vitamins, sucrose and agar.
Stock
Stock
Volume of stock
Final
concentration
for
11
solution
concentration
(0-1-')
of medium (ml)
acid
0.1
10
1
Pyridoxine-[ICI
0.1
10
1
Thiamine-HCI
0.1
10
1
solution
Nicotinic
(mgl')
Other components: sucrose 40 gl-1 and agar 8 g1-'
From Parigo Horticultural
Co., (personal communication).
143
Appendix
C:
Stock
Solutions
Growth
of
Regulators
" 6-Benzylaminopurine
100 mg 1-1: initially
(BAP).
dissolved in 0.1 M hydrochloric
acid solution, then
made up to final volume with distilled water.
" a-Naphthaleneacetic
100 mg l-1: initially
(NAA),
acid
and gibberellic
(GA3).
acid
dissolved in 0.1 M potassium hydroxide solution,
then made up to final volume with distilled water.
" 2,3,5-Triiodobenzoic
(TIBA).
acid
100 mg l-1: dissolved and made up to final volume in distilled water.
9 Thidiazuron
10 mg I-':
(Schering Agrochemicals Ltd).
dissolved and made up to final volume in distilled water.
9 Paclobutrazol
(ICI Ltd).
100 ing 1-': mixed with and made up to final volume in distilled water.
Stock solutions
dark.
in
5°C
the
were stored at
144
Appendix
D:
Alstroemeria
Preparation
from
Extracts
of
`limbers
Soil was removed from the tubers by washing under cold running
clean tubers were then homogenized
in a blender with distilled
tuber being added to every 200 ml of distilled
was strained
through
liquid produced
was centrifuged
(r. p. m. ) to remove remaining
was decanted
for 15 minutes
small amounts
water,
The resulting
water.
cloth to remove the majority
water.
of the plant
of plant debris.
from the pellet and stored frozen until
100 g of
mixture
debris.
at 3500 revolutions
The
The
per minute
The supernatant
required.
This procedure was performed as rapidly as possible on ice, using distilled
degradative
water chilled to 2 to 4°C, to minimize the natural
brought
homogenization
the
to
about as a response
This method
was adapted
from Chuang
of the plant
reactions
tissues.
(1978).
et al.
145

Bond, Steven (1991) Control of rhizome growth in Alstroemeria. PhD

Transcription

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