Potamogetonaceae - Natuurtijdschriften

Aclaßol. Neerl.
Ovule
November
33(4),
1984,
ontogeny
development
in
and
seed
Potamogeton
(Potamogetonaceae),
L.
the
campylotropous
I* and F.
T.Takaso
*
p. 519-533.
with
natans
a
note
on
ovule
Bouman
Present address: Makino
Herbarium, Tokyo Metropolitan University, 2-1-1, Fukasawa,
Setagaya-ku, Tokyo 158, Japan
Hugo
de Vries
Laboratorium, Universiteit
van
Amsterdam, Plantage Middenlaan
1018 DD
2a,
Amsterdam
SUMMARY
The ovule of
uments
are
pressed layers
of the
1.
adaxial
are
in
origin
of the
campylotropous
types
wall.
The
and
crassinucellate, bitegmic
ortho-campylotropous.
Both
integ-
The seed coat consists
of the
com-
develop by intercalary growth.
of which
differs
curvature
carpel
and
integuments,
from
the outer
only
the usual
terminology,
types
and is
structure and
shows
layer
cell
brought
functional
wall
about
aspects
thickenings.
by
The
proliferation
a
of the different ovule
discussed.
INTRODUCTION
An inflorescence of
are
born almost
subtended
alternate
ing
at
Potamogeton
right angles
bracts.
by
position,
scale-like
mens are
Each
as
before,
of spirally
and
arranged
clearly by
inserted
stamens
sometimes
and uni-ovulate
Posluszny
on
flowers which
are
& Sattler
the connective of the
mostly spatially separated from,
the
carpels
in
(1974).
The
mature
sta-
correspond-
stamens.
literature
bryo
1908;
on
(1839),
its
Gupta
1934).
are
cords has been
bitegmic
tropous
or
layers.
tetrad
or
and
was
a
research object of such early plant embryologists
Schacht
embryology
development
sac
mentary data
tal
consists
the axis of the inflorescence and
flower has four
protuberances (tepals)
initiated
Schleiden
as
to
indicated
Potamogeton already
is
is
Potamogeton natans
dermal
and
and
Hofmeister
incomplete
embryology (Wiegand
Of the ovule
available. The
given by
(1850)
is still rather
Davis
orthotropous (by
camptotropous).
ontogeny and seed
most recent
(1966;
see
(1861).
and
1900;
coat
mainly
1901;
em-
Cook
development only frag-
also Lakshmanan
to
concerns
Holferty
summary of the
various others said
However, the
embryological
1970).
re-
The ovule
be anatropous, campylo-
The nucellus is crassinucellate and has up
The megaspore mother cell forms after meiosis
“triad”. The chalazal megaspore develops into
a
a
linear
or
to
7
parie-
T-shaped
Polygonum
type of
520
T. TAKASO AND
embryo
increases in size and
Both
of the
lies
ognizable and form
ovulate
is absent.
the seed
against
has been studied
into
a
shape,
and
stricto
practice
together
has
endocarp
mesocarp
germinating
are
seed. The
The
embryo
fruits
(Kirchner
shorter
a
called
are
1-18
layers
narrow
of the
part
endocarp (Roth
the fruit
bursting
al.
1908).
In
outer
longer period
mesocarp,
floating
acts as a
cells with
mesocarp
endocarp
The dorsal part of the
of
thin-walled,
the apex of the
by
hydrochory
species the fruits
of time. In other
Fruits
mostly
which
fruit,
first.
dispersed
of the
thick-
massively
and the
allow the emergence of the
to
starts at
cotyledon
and
part
morpho-
one-layered
of sclereids of different
1977).
opens
but
a
which is lifted up from the fruit is
of the lid
emerge with its
fit readily into
not
drupes,
parenchymatous
of long and
awl-shaped part
polychorous
are
et
or
to
layer
unrec-
Each of the four uni-
(1970).
approximate, longitudinal sutures, consisting
two
called the dorsal lid. The
the
layers
outer
become
is differentiatedinto
pericarp
the sclerotic
parenchymatic cells, along which
causes
Aalto
comprising
one-layered endocarp
a
ened cell walls. In
sensu
by
Histologically they
resemble achenes. The
sclerified inner
tissue,
the other
part of the species has large intercellular spaces and
a
the
integuments only
indehiscent fruit; they do
an
mostly rather thin and fleshy,
a
which in
From the
the
starch and
embryo, containing
clearly cellular,
the customary fruit classifications.
logically they
In
micropylar parts excepted.
cuticular layer around the embryo (Netolitzky 1926).
a
structure
carpels develops
exocarp,
micropylar
confirms to the caryo-
embryogeny
The curved
coat.
remains
integument
The fruit
coenocytic
nucleus of the chalazal chamber
single
their
two-layered,
are
endosperm
outer
helobial. The
The
finally degenerates.
integuments
seed
oil, directly
is
while the
cellular,
and the terminal suspensor cell becomes vesicular.
phyllad type
mature
formation
Endosperm
sac.
chamber later becomes
F. BOUMAN
cases
decay.
epizoochorous dispersal by
pass
to
float for
persist
the intestinal
birds and fishes unhurt. Also
zoochory
or
able
the fruits may
tached shoots until the latter
can
are
tract
mud sticking
on
de-
of both
to water
fowl has been recorded.
The present
tive
study
of
structures
aims
at an
amplification
Potamogeton, especially
of
as
our
knowledge
ovule
regards
of the reproduc-
ontogeny and seed
coat structure.
2.
MATERIAL AND
The material of
METHODS
Potamogeton
natans
L.
collected in the
was
Botanical
University of Amsterdam and fixed in Allen’s modified Bouin fluid
III. For standard light
dehydrated
6
or
a
mature
the PAS
material
was
at
TBA series, embedded in
seeds
glycol-methacrylate,
with
flowers
7 fan and stained with Heidenhain’s
young and
in
in
microscopy,
were
sectioned
at
5
dehydrated
in
an
ethyl
or
7
/mi
of
alcohol
safranin and fast
a
NBA
series,
with glass knives
haematoxylin.
were
microtome-sectioned
paraplast,
means
in Craf
developmental stages
haematoxylin,
dehydrated by
reaction and Eastman’s
various
Garden,
or
For SEM
at
green;
embedded
and stained
studies,
some
series, critically point-dried
and
OVULE AND SEED
Fig.
1. Median
IN
longisections
and the initiation
origin.
and
of ovules
ovule
gold;
showing
mature
the
their relative
position
integuments (D-J).
in
respect
Both
of the
integuments
carpel (A-C)
are
of dermal
gradually proceeds,
integument; nuc: nucellus;
coated with
521
NATANS
early developmentof
The curvature of the
ii: inner
3.
POTAMOGETON
oi: outer integument.
seeds
were
directly
studied after
coating.
RESULTS
The
carpel primordia
rapidly
and
are
protruding
obliquely cup-shaped,
the inner
margin.
the dorsal side
growing
more
The median part of the lower (inner)
522
T. TAKASO AND F. BOUMAN
margin
develops
margin
an
other
into
the ovule
carpel margins
The young ovule is
locule with
its
the ovule
The young ovule primordium is
layers enveloping
inner integument,
stage, and the
developmental
fan-shaped
this
at
is
edge
of
tunica
two
the
concomi-
primor-
slightly projected
are
their derivation from the
at
layer
the ovule
of this part
divisions sometimes take
the
at
occur
carpel
campylotropous.
it consists
layer, whereby
constituent cells
part of the ovule primordium
very difficult
usually
becomes
in the second
place
The adaxial
showing
cell
periclinal
part,
divisions also
is
thus
fashion,
of the basal
2A).
horizontally
A little before the initiation of the
cell divisions take
ID and
canal.
stylar
bends down into the
three-zonated, i.e.,
portion (fig. ID).
corpus
periclinal
develops (figs.
grows
inner
with the
continuously
form the
gradually
with anticlinal cell divisions in the first
tantly
in
to
directed downwards and
micropyle
a
the adaxial side of this
edge
and oriented almost
initially orthotropous
(fig. I). After megasporogenesis
dium
This
the ovule and
envelop
to
At
primordium.
edge is formed (figs. 1A-C).
dermal
in the
place
side
convex
in
layer.
dermal
layer
developmental stages and, therefore,
subsequent
a
As
These
(fig. IE).
demarcate the derivative cells from the dermal
to
this
at
arranged
it
layer
this side.
The inner
periclinally
probably
cave
dermal
as
origin,
of
which
3C), and
in
adjacent
ally divide
the
ones
in the
the dermal cells
for its
divide rather
direction,
(figs.
periclinal
the median
obliquely (fig. 3A).
thus
IH and 3B.
forming
D),
or
but
or
con-
initial cells of
two
2B and 3A,
C).
cell divisions
oblique
divides
one
most
and the
convex
periclinally
The resultant cells gener-
two or
three cell
of the
some
dividing
longisections,
growth (figs. 1G,
either
they exhibit
the
at
consists of three
primordium
of three initials,
case
same
nucellus
yound
slight swelling,
simultaneously
responsible
are
initials
two
a
From the observation of median
the inner integument arises
case
and the
the
obliquely.
sides. In sections the
In the
(fig.
integument is intiated
or
around
rows
apically
situated cells
divide bifacially (table 1). The subdermal cells underlying the integument initials
also
the
show
periclinal divisions,
integument
proper
but
(figs. IE,
do
they
F and
A little after the initiationof the inner
simultaneously
side in
convex
of the inner
table
I).
the
some
cases.
As
two
or
derived from
usually
originate
of the
the
in the
two
the
inner cell
of the
2C and 3B,
difference in
The
length
initials.
manner.
The
D).
bulk of the
the
three cell
After the first
cell
(Jigs.
rows
row
nucellus is
of the
during
the
formed
is also due
are
of much
integument
division of the
case
other derivatives is
the
that
as
may sometimes
anticlinally,
In this
at
II and 3E,
outer
rows
periclinal
cell divides
same
early growth
two
arises
integument
initial cells
integument,
However,
daughter
respect
of this
outer
initiation is
dermally originated
upper
in
the
but it appears earlier
sides,
integument primordium three-layered (fig. 3G).
tion of the
in the formation of
than three rows; in other words: the
two
following
initials,
sign
with the inner
compared
participate
integument,
concave
The first
three
more common occurrence
is
and
convex
integument (figs. IH,
divisions in
to
F\
at
not
2B).
thus
outer
rendering
the relative
posi-
for
the
and anticlinal divisions in
the
responsible
subsequent stages.
by peri-
OVULEAND SEED IN
Fig.
2,
Transversal
the later
523
POTAMOOETON NATANS
longisections
stages (E-H).
The
of ovules
growth of
at the
early stages (A-D)
the nucellus is
mainly
layer.
ii: inner
integument;
nuc:
nucellus;
oi; outer
integument.
and median
longisections
due to derivatives of the second
at
tunica
524
Position
Table
1.
I-VI1
correspond
ovules
observed
bold
dividing
of
to those
italics
type figures,
or
of
recently
figs.
1G,
divided
IH,
II.
cells
in
from the base
are
which
are
anticlinal,
of the
the
the
the
inner
and outer
2H. 4B.
IJ-2E, 2F.
brackets. The numbers indicate
in
are
ments, but those in
in
AND F.
T. TAKASO
position
integuments. Stages
The
respectively.
from the
apices
periclinal
numbers
of the
of
integu-
for the
micropylar proliferation. Except
others represent
BOUMAN
divisions in respect
cases
of the
ovular axis.
Stage1
Stage
(14)
(15)
cc
cv
1,1
CC
II
III
cv
CC
1
IV
Stage
(18)
1,1
-
Stage
CV
CV
2
1,1
1,1
1,3
1,2
3
3.4
Stage
(9)
CC
1,2
V
Stage
(7)
VI
CC
cv
CC
CV
u
3.6
I,I
3.7
5
6.7
2.6
8,10
2,2
VII
(4)
CC
10.13
CV
8,18
1.5
4
il
Stage
(21)
1.4
6.7
15
8,11
11,12
12,12
II
13.13
14.15
2
1,1
2
1,2
1,3
2,3
1
4
i,i
6.9
3,9
3.5
9.12
6,8
ol
20
17,41
-9.9
9,10
12,12
-
-
-
-
2
-
2
3
10.103,4
15
10
1,2
4,7
13,15
8
2,9
il
10,12
OI
13,20
20
-
-
4
2,3
-
8
-
6,6
ol
6,9
5,9
14
7,8
16
-
8,12
12,12
14,19
II: inner
integument;OI;
outer
integument; il:
inner
ol: outer layer;
layer;
cc: concave
side;
cv: convex
side of the ovule.
second tunica
form a
layer
cell is
archesporial
of the
cell
undergoes
cell
undergoes meiosis;
into
a
only
at
an
triads
Polygonum
were
observed in
After the
divides
thus
initiation,
only anticlinally
increasing
the
that the inner and
of three cell
outer
every
or
layers
inner
to
length
outer
our
soon
mother cell. The
parietal layer.
J
as
periclinally
The megaspore mother
fails
(in
the
the
girth
same
outer
direction
of the
derived from three initial cells,
layer (usually
to
divide,
figs. 2A-D).
as
integuments
in the
outer
one)
initials),
integuments (table I),
integuments retain their original thickness.
of the
to
primary parietal
slides. The chalazal megaspore develops
to
their surface
well
The subdermal
dyad apparently
constituent cell of the inner and
as
C).
divides
The ovule is slightly flattened during the
sac.
early stages (compare figs. ID, F, H,
a
and
cell of the
micropylar
type of embryo
IF-H and 2B,
megaspore
further divisions to form
the
(figs.
early stage
cell and the
primary parietal
because
ovular apex
distinct
In the
so
case
however, cells of either the
divide less
actively
and become
525
OVULE AND SEED IN POTAMOGETON NATANS
Fig.
by
3. Successive
the
same
surpassed
stages
the other
by
two-layered
cate
conditions
retention of the
initials)
two
The
and is scattered all
but is
a
ment
of the
little more
over
Jigs.
2H and
integuments
in
is
are indicated
a
or
the lateral sides
three-layered
ovules
of
to
obviously
the
or
from
apical part
two-layered
one
integuments,
outer
The
(cf.fig. 4D).
intercalary growth
to
young seed,
matter
inner and
J).
sections indi-
from three
with the
II,
and contribute
cross
only rarely extending
due
two- or
developing
As
at
figs.
integuments,
outer
bifacially
(originated
mingles
integuments
develop-
indicated
as
results in
three-layered
two- or
respectively (compare figs. 2E, F,
course,
by
condition of the inner and
the growth of the inner and
to
outer
in circumference results from anticlinal divisions in all constituent
outer
integuments
is
(3)
of the ovule
(in
also exhibits mitotic
the
case
of
a
Table 1
capable
middle
layer
condition
condition
found
The
mature
4B)\ (2)
off derivatives
but
mainly
cells after their initiation; and
innerand
initials
side in
concave
well. Serial longitudinal and
upwards,
frequently
in the
the
at
the circumference of the
integuments
integuments
integuments
cut
may
as
three-layered
following points: (1)
outer
same
the upper parts of the
making
integument
three-layered
from the base
(Jigs. 2E, F, H).
the
of the
situated cells of the inner and
longisections,
two-layered
a
integuments. Derivatives
thus
inner
hand, apically
when viewed in
the
of the
layers,
the
{fig. 3B;
On the other
to
of initiation
letters.
of
clearly
three-layered
figures
shows
that every
dividing throughout
as
integument part,
the
cell of the
development
every
cell of the
do the cells of the inner and
outer
layers).
At the stage when the inner
apical part of
planes (Jigs.
cell divisions
one.
layer
the
IJ and
are
About the
integument
inner integument
of
2D-F).
more
same
of the nucelius.
As
a
begin
result,
frequent
to
the
the
nucelius,
divide periclinally
endostome
divisions
are
most
place
frequent
in
The
layer than
cell divisions also take
cells of the
or
develops.
incidence in the inner
time, periclinal
Although
an
overgrows
various
periclinal
in the
outer
in the dermal
at
the nucellar
526
Fig.
T. TAKASO
4.
ovules;
seed
I:
Development
E:
coats
cross
ii: inner
of the
seed
of
fruit
longisection
indicated in
section of
E;
young
a
coat.
H: seed coats
seed coats
integument; nuc: nucellus;
A-D:
showing
the
at the
median
longisections
curvature
later
a
young
and
cross
seed; F,
developmental stage (the
cut at the level of the
oi: outer
of
integument.
arrow
in E.
AND
F.
sections
G: details
same
BOUMAN
of mature
of
portion
young
of F);
OVULE AND SEED
5. Median
Fig.
A:
the whole
wall
es:
of the
longisections
ovule
of a mature ovule.
(x 100);
B: details
of
a
of A
part
showing
the
from the
nucellus;
oi: outer integument;
proliferation
adaxial
carpel (x 250).
ii; inner
embryo sac;
ing
527
IN POTAMOGETON NATANS
integument; m; micropyle;
nuc:
pt: proliferat-
tissue.
apex,
they
mains
also
occur
responsible
at
the flanks of the nucellus. The second tunica
for the greater part of the nucellar tissue
layer
re-
IJ and 2D-F,
(Jigs.
H).
At the stage of
fills the
lar in
carpel
sections (figs.
cross
of the
itself,
ovule
divisions
the
at
resultanttissue
pyle
is formed
or
cf.
or
begins
by
to
protrude
the endostome
parietal layer
embryo
the peripheral
The ovule is
4A and
5).
the inner and
divisions
divisionsin
supplied by
xylem
course
stigmas
pollen
to
result of active
as
tube
apical
every
4B and
rim of the
as
completely
cell
always
5).
outer
cell
The
integu-
their bases become
layer.
The nucellus is
even
more
longitudinal
radially
directed
into the ovule
differentiatedinto
ring
through
-arrives
at
the
narrow
to
fan
or
out
spiral
running
rows,
where-
carpel (Jigs.
in the chalaza.
elements.
canal into the
the dorsal base of the
high,
from
(Jigs. 4B, D).
pollen germinates
stylar
two-
four-
relatively
five cells
6 cells. The corpus tissue
tube is porogamous. The
grows
degrees
become
integuments
and sometimes
three,
high
outer
(table 1),
the chalaza is oriented in
already
pollen
tube(s)
carpel (figs.
90
periclinal
the rather massive ventral bundle of the
turns
has
of the
and the
locule. A
sac
be
and the
tissue of the nucellus is
This bundle
A part of the
The
may
completely
rather far distance when viewed in longisections
anticlinal cell
by
by about
curvature
the
and
and almost circu-
into the median flank of the ovule. The micro-
alone,
The nucellar cap has become
the basis of the
as
at a
fig. 6A). Although
five-layered by periclinal
and the
the
to
is also
longisections
inside of the adaxial wall of the
three-layered
large.
Next
shape
carpelary base,
in
pear-shaped
4A-D).
the curved
ment, which is tapering, lies
(fig. 4B,
the ovule faces the
pollination,
locule. It is curved,
ovule,
on
the
carpel
from where
528
it
T. TAKASOAND F. BOUMAN
grows
in between the ovule and the
the lateral side of the
(fig.
the nucellar apex
the
beginning
After fertilization the ovule
reaches
ture
wall. Cells
to
cell
by
degrees by
kind of central
a
cf.figs. 6C,
(fig. 4E;
stretching. Especially
nucellar base become very
the chalazal end of the
aberrantly
embryo
and
stase-like
tissue is
by lysis
the nucellus and
and
of the
layer
appear
walls
partly
at
formed
of the
the
and every
(figs.
outer
formed
layers
by
nucellar
of the
another
by
by
integument develops
mature
the exotesta,
the
at
6.
with
cross
Scanning
electron
of fruits
of the seed coat
e:
embryo;
completely.
stretch
layers
concave
The
(Fig. 4G).
outer
local
grains.
F). Usually
a
one
this
become
specific
of
layers
compressed
and
from the apex
proceeds
embryo
the inner
to
Cuticles
(Fig. 6F).
integument.
The
outer
are
layer
thin cuticle and remains loose from the endo-
compressed
a
periclinal
have
into a tanniniferous layer. The nucellar
growing
and
outer
not
The inner and middle
of the inner
the
The
thin,
remnants
is rather
of the
tanniniferous tegmen and
Testa, tegmen
and nucellus
are
complex
inner and
a
and
middle
tightly packed
from
separated
one
cuticles.
penetrating pollen
sections
basal half of
shorter,
The cells do
The small chalazal-funicular part of the seed has developed
Fig.
hypo-
cell walls of the
strongly pitted.
seed coat, although
integument,
outer
are
develops
epidermis
of nucellar cell walls.
layer
layer
4H and 6E,
Accordingly, the
carp.
for parts
also the inner periclinal,
small starch
some
strongly compressed
by
in thickness. All cell
maturity (figs. 6B, E).
the base. The inner integument
tissue is
not
E) except
sections and
collaps
integument
resorbed
invades the
by
grows
Later the
(fig. 4E).
have
of the
this tissue
first
sac
the central part of the nucellus
length,
under
enlarge,
development
where the cells may remain smaller
extent
cross
except for
outer
sac
of the
expansion
embryo
nucellar cells
mainly
center
not
the further
The
embryo
the
integument become thickened (fig. 6F). The anticlinal walls
in
thin and
contents
the
outer
in
carpel
proliferated
directly lying
These cells do
the nucellus.
the
curva-
homogeneously,
tissue in
the first stages of seed
I and 6B,
lesser
a
corpus
block
to
surrounding
grow
rather
small group of cells
a
seem
consumes
micropyle,
to
x-shaped
are
campylotropous
which the ovule has become curved
excepted.
aside and
pushed
(figs. 4F,
the
at
anticlinal,
sac
half-way
gradually
integuments only
longitudinally
elongated,
of the
and radial-
of the tissue of the adaxial
enlarges
the cells of the
During
about
at
stretching
side and
proliferation
body around
embryo
downwards.
remains situated
The
The
considerably.
grows
the
cell walls and
staining
sac
large
periclinally.
The nucellus
D).
along
way
penetrating
both sides of the ventral bundle divide periclinally. The
at
tissue forms
270
and
micropyle
cells. Their cells are
integumentary
may divide
they
the
The cells around the ovular base deviate almost from
A).
from the other
and
ly stretched,
6
the shortest
carpel wall, seeking
integument, through
outer
(
x
fw: fruit
240,
micrographs
tube
(
x
showing
x
960
270);
the
of a mature ovule
and seeds. A:
B: stretched
of the exotesta
cells
campylotropous
seed
(x20); E,
resp.).
wall; pt; proliferating tissue;
sc:
seed coat.
a tenuous
micropylar
F:
(
x
part
390); C,
longi-
and
plexus
of the
D:
ovule
longi-
cross
and
sections
OVULE
AND SEED
IN
POTAMOGETON
NATANS
529
530
of
T.
and
ring
of about
of
It is
small,
shows intercellular spaces. Most cells
ma
and
formation
Endosperm
The
seed the
one
curved
(figs. 6C,
has been
270
over
D ). In
like the
degrees
sections the
cross
are
coenocytic.
with
provided
by
and
seed,
embryo
the
hypostase
hy-
or
The
embryo.
size. In
The
chalazal
the
mature
embryo
mature
embryo
sac
suborbicular in outline.
axis and
hypocotyl-root
strand. The
central provascular
a
smaller
fills the
completely
is helo-
endosperm
in
embryo.
is orbicular
plumule
con-
tissue is filled with starch and aleur-
embryonal
in the meristematic parts
grains, except
4.
a
micropyle degenerate
The
considerably
consumed
fully
tains several leaf primordia. The
on
by
peripheral parenchy-
The
embryogenesis.
becomes
takes up about half of the
cotyledon
cotyledon
the
the
constituting
which increases
nucleus,
endosperm
the
precedes
chamber
micropylar
chamber has
The
nucellus
resorbed.
are
bial.
from the
separated
tanniniferous cells with suberised walls. The
is continuous with the tanniniferous
tegmen. The
postase
is
tracheids.
spiral
eight layers
TAKASOAND F. BOUMAN
(Fig. 6E).
DISCUSSION
have many advanced characters in their reproductive
Potamogetonaceae
such
gans,
pous
the
reductions of floral
as
dermal
ovules,
seed,
mature
family
can
ton
the
to
layer.
primordium
relatively specialised
a
richardsonii has
should also be
layer
be
at
variance
a
the young ovule
Marantaceae,
responsible
primordium.
of
case
separate. The
out
(and
Posluszny
the
two
processes
divisions in the second tunica
the
crassinucellate) again
placental
Begoniaceae
are
drawings
and
are
anthers and
alternate with anthers
not
be
and
carpel
this
seen
tepals.
Since
carpels
simultaneously
in the
ovule initiation in
same
convincing,
or
in
but secondari-
now
known
appeared
photographs
because
median section.
Potamogeton
“secon-
a
region
from
(Boesewinkel & De Lange 1983).
tions illustrating carpel initiation
not
carpel
continu-
that after the
layer,
layer,
the
are
carpel primor-
phenomenon
re-established in
of the ovule
structure
Potamogeton,
of the adaxial part of the
and Sattler’s
initiation of
for the ovule initiation. These
Ovules initiated in the second
Droseraceae and
the other hand,
to
the
cell divisions in the second
periclinal
explained by
is
structure
three-zonated
ly becoming
On
may be
carpel by periclinal
three-zonated
darily”
and derived one.
with the three-zonated
directly develops
discrepancy
initiationof
to
described in this paper. In the
since the ovule
dium. This
two-layered
a
is primarily due
and ovule initiation are very difficult
ous
in
The
tunica and
to
as
endosperm
non-dehiscent fruits.
P.
This
seem
and absence of
and
the floral apex of Potamoge-
densus and
findings
coats
or-
carpels, ortho-campylotro-
Posluszny & Sattler (1973,1974)
carpel primordia
tunica
integuments, large embryos
non-differentiated seed
be considered to be
According
uni-ovulate
parts,
to
and
they
of
sec-
also show
tepals,
they
can
A re-examination of
be necessary
to
solve
problem.
The
clinal
two- or
or
three-layered integuments
oblique
divisions in
two or
three
of
Potamogeton
neighbouring,
are
initiated by
peri-
dermal initials and sub-
531
OVULE AND SEED IN POTAMOGETON NATANS
of all
sequently develop by intercalary growth
cal
in dermal integuments of many other
cells. No
participant
could be demonstrated. This type of
growth
specific api-
is also
histogenesis
angiosperms (Bouman 1984),
but
described
disagrees
with the description of Roth (1957) of Capsella bursa-pastoris, where both integsaid
uments are
to
grow
rhythm
Potamogeton the
In
is
curvature
so-called basal
the basal
a harmonious
about
brought
adaxial side of the
ton
ovule in
is
Potamogeton
Its
who
placed
the ovule in the
special
nature
best
classified
in many
as
introduced
terms
several
by
in the
as
by
authors,
and
in the
shape
tropy and
bining
in
other
Bocquet (1959)
the basic
sacs.
must
be
tion of
Indeed,
ovules. In
a
and
as
Bocquet
far
as
series of
early
1839
as
places
The record
the
a
in
many
Both
& Bersier
terms
ontogenetic origin.
raphe
or
by
two
or
It
involved
curved
in
embryo
sacs.
and
may
result of the resorbing
system.
body
be formed
amphitropous,
or
been characterized
by
other
partly amphitropous.
showed that
with
to
campylo-
anatropy. Com-
campylotropy
body
ovule.
amphitropous
the
is diverse.
em-
Amphitropy
the arch of the nucellus.
nucellus,
sac
can
the inner
structure
of
to
various
or
from
degrees.
a
processes may
Moreover,
straight
endosperm.
be of differ-
integument,
campylotropous
Many ontogenetic
develop secondarily
of embryo
and
and be characterized by the forma-
is present. However, it
by
are
These
demonstrated the diver-
They
which extends into
basal
activity
embryos,
amphitropous
as
anatropy
all in combination. Also the
also
campylotropy
have been re-defined
processes with respect
different combinations and
sac
of
nine different types of ovules with curved
body”,
can
and
(1960) clearly
embryo
campylotropous phase
a
in Schlei-
This has caused much confusion
partly campylotropous,
independent
ovules such
of the
Schleidhn,
placed
angiosperm
campylotropous
ways.
ortho-, hemi-,
so-called “basal
by
in seeds with curved
in
These authors also re-defined the
preceded by
a
curvature
been found in any other
not
needs confirmation.
literature,
of ovules with curved
are
Potamoge-
the ovule of
Potamogeton
present study
resulting
of the
part
the
share in the ovule
no
campylotropous
so
(1829) already.
ovules without a distinct basal
a
the
to
conflicting
families
amphitropy
bryo
be
has
at
with the
camptotropous type. Schacht (1850) rectified
sacs,
amphitropy, they distinguished
the
of
denominated as
Mirbel
campylotro-
compared
application of the terminology. Several families have
authors,
ent
type
and has
diverse
at
often in
campylotropous
sity
embryo
mostly
are
may be
ridge,
a
almost
of ovule
shape
of mesocarp tissue
campylotropous
ortho-campylotropous.
families and
ovules and seeds
proliferation
recognized
was
new
The
of ovule and fruit. The
proliferation
Ruppia (Ruppiaceae)
Ovules with curved
met
bifacial
carpel locule, leaving
endocarp.
of the ovule and stated that it should be
description
in the related genus
fill the
growth
The
unique
lycotropous type. According
be
can
a
the fruit wall and differentiates like the other
to
mesocarp.
seems
plant.
den’s
initials exhibiting
apical
and the
present in the form of
seed
Schleiden’s
fully
found in many other
body
body
of the endo- and
parts
rim of
the
by
wall. This
carpel
seed proper, remains attached
or
a
integument
outer
and seed is the result of
pous
of
means
ovule and seed
space between the
no
by
of cell division.
nucellus
The great
a
as
diversity
532
T.
in the distribution and
that
mental
Very
of
structure
has
campylotropy
developed
pathways during
than
the evolution of the
little attention has been
ovules renders it
campylotropous
more
in the
paid
and
once,
TAKASOAND F. BOUMAN
angiosperms (Bouman
pertaining
among
In the
gioody).
the
In
flowering plants,
that
tubes
curvature
anatropy
route.
ovuly.
It is
mostly
or even
touching
mogeton
is
as
one
longer,
so
quences
have
have better
ty
or
pyle
According
for the
way
the
brought
pollen
found in families with
stylar
tissue. As
exceptions
in this
embryos
length and,
longer
the
in
way
for
to
the
mono-
campylotropous
the funicle. Pota-
evolutionary advantage
development. Campylotro-
long
as
the
seed itself
or
without much
longer embryos
of the seeds.
and
and/or cotyledons,
seeds have
ana-
seeking
with
are
long embryos reaching
even
conse-
Long
supposed
establishment. It is evident that the
seedling
campylotropous
mostly
near
dispersal potential
hypocotyls
the
base of the ovule,
most
micropyle
as
be reached
By
ovule directed towards
erect
respect. The
twice
to
up
a
so,
roots,
possibilities
is
the
to
walls.
tube and facilitates the
regards fertilisation,
having
anatropous
near
an-
reach
micropylar droplet.
is correlated
single
a
in
ones
To
to
the present authors the
in ontogeny and
diversity
the
classify
which
required,
studies. For
majori-
from micro-
cannot
curved
embryo
different
prefixes
sacs.
it
terms
do
not
reflect
campylotropy
an
extensive
established without detailed
seems
ana-,
in
advisable
hemi-,
This may prevent
ontogenetic
campylotropy
become
reasons
existing
adequately
of the ovules and seeds with curved
shape
existing diversity
practical
with the facultative
of
the
to
can
chalaza.
to
sacs.
has been
better
pollen
and the ovules have
angiosperms orthotropy
campylotropy
all
perhaps
In
contain
can
that
to
the
affixed
stigmas
becomes manifest at later stages of
for the
embryos
micropyle
of the few
of campylotropy
pous seeds
the
shortens the
right
ovules behave
the
caught by
growing along the inside of the carpel (stylar)
of the
is
is
so common occur-
angiospermy (or
ovules of gymnosperms the
micropyle directly, mostly by becoming
tropous
the
is related with
mainly orthotropous
angiosperms pollen
by pollen
so
the
develop-
1984).
literature to the functional
aspects of the differentovule types. The anatropous ovule, of
rence
plausible
several
along
apply
ortho,
the
term
developmental
campylotropy,
for all ovules and seeds with
further confusion until
involved and the
processes
has been extended
or
to
embryo
terminology
our
insight
in
functional consequences
satisfactorily.
ACKNOWLEDGEMENTS
The
authors
and to Mr.
are
R.
indebted
van
to Professor A. D.
der Meer and Mr.
Relations Directorate of the Dutch
to work at the
Hugo de
J.
Meeuse
C. Bakker
Ministry
for the critical
for technical
reading
assistance.
of Education and Sciences
A
of the
grant of
has enabled
manuscript
the Internal
the first author
Vries-laboratorium.
REFERENCES
Aalto,
dian
M.
(1970): Potamogetonaceae
species.
Acta Bol. Fenn. 88:
fruits. I.
1-85.
Recent and subfossil
endocarps
of the Fennoscan-
533
OVULE AND SEED IN POTAMOGETON NATANS
Bocquet, G. (1959):
—
& J. D. Bersier
Sci.
The
campylotropous
(1960):
F. D. & A.
F.
M. T.
(1908):
Club
Toney Bol.
Davis,
G.
Gupta,
de l’ovule:
222-227.
développements tératologiques. Arch.
(1983); Development of ovule
The
and seed in
York
L.
Begonia squamulosa
M. Johri
(ed.), Embryology of Angiosperms. SpringerVerlag,
(in press).
development
of the
embryo
sac
and
embryo
of
Potamogeton lucens.
Bull.
35: 209-218.
L.(I966): Systematic Embryologyof the Angiosperms. Wiley,
B.
Soc.
Phytomorphology 9:
32:417-425.
The ovule. In: B.
(1984):
Berlin, Heidelberg,New
Cook,
Lange
de
Hook.f. Acta Bot. Neerl.
Bouman,
ovule.
systématique
13:475-496.
(Genève)
Boesewinkel,
La valeur
(1934):
Contribution
to the
life
of
history
New York.
Potamogeton crispus.
Journ.
Indian Bot.
13:51-65.
Hofmeister, W. (1861):
Neue
Beitrage
zur
Kenntnis
der
Embryobildung der Phanerogamen. Abh.
Kon. Sachs. Ges. Wiss. 7:629-750.
Hloferty, G.
Kirchner,
M.
pas. Band
C.
F.
végétale.
K. K.
B.
F.
Nouvelles
(1908): Lebensgeschichte
der
31: 339-346.
Bliilenp/lanzen Mitteleuro-
recherches
sur
Indian
la
Nat. Sci. Acad. 41:348-351.
et les
structure
développements
de l’ovule
17: 302-318.
Anatomie
(1926):
10. Gebriider
Posluszny,
of Potamogeton natans. Bot. Gaz.
embryo
(1970): Potamogetonaceae. Bull.
(1829);
Ann. Sci. Nat.
Netolitzky,
Band
and
1,1. Ulmer, Stuttgart.
Lakshmanan,
Mirbel,
(1901); Ovule
O, von, E. Loew & C. Schröter
Bomtrager,
V. & R. Sattler
der
Angiospermen-Samen.
Handbuch
der
Pflanzenanalomie,
Berlin.
(1973);
Floral
development of Potamogeton densus.
Can.
Jour. Bot.
51: 647-656.
—
&
—
Roth,
sche
—
(1974); Floral developmentof Potamogetonrichardsonii.
I.
Amer. Jour. Bot. 61:209-216.
(1957): Die Histogenese der Integuraente von Capsella bursa-pastoris
Deutung. Flora
(1977):
Schacht,
Fruits of
H.
Schleiden,
gamen.
Angiosperms. Encyclopedia of Plant Anatomy,
(1850): Entwicklungsgeschichle
M. J.
Wiegand, K.
Bot. Gaz.
M.
des
(1839); Überdie Bildung des
Verb. Kais.
Leop.
(1900):
30; 25-47.
und
ihremorphologi-
145:212-235.
Carol.
The
Akad.
Eichen
Naturf.
development
vol.
10.
Pflanzenembryos. Thesis,
of the
und
Borntrager,
Berlin.
Amsterdam.
Entstehungdes Embryo
bei den Phanero-
11:27-58.
embryo
sac
in
some
monocotyledonous plants.