The Development of Isolated Roots of Comptonia peregrina

The Development of Isolated Roots of Comptonia peregrina (Myricaceae) in Culture
Author(s): Patricia L. Goforth and John G. Torrey
Source: American Journal of Botany, Vol. 64, No. 4 (Apr., 1977), pp. 476-482
Published by: Botanical Society of America
Stable URL: http://www.jstor.org/stable/2441778 .
Accessed: 23/08/2011 16:13
Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at .
http://www.jstor.org/page/info/about/policies/terms.jsp
JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of
content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms
of scholarship. For more information about JSTOR, please contact [email protected].
Botanical Society of America is collaborating with JSTOR to digitize, preserve and extend access to American
Journal of Botany.
http://www.jstor.org
Amer. J. Bot. 64(4):
476-482. 1977.
THE DEVELOPMENT
COMPTONIA
PEREGRINA
OF ISOLATED ROOTS OF
(MYRICACEAE)
IN CULTURE'
PATRICIA L. GOFORTH AND JOHN G. TORREY
01366
Massachusetts
Petersham,
CabotFoundation,HarvardUniversity,
CT
AB STRA
Seedlingroots of the sweetfernComptonia peregrina (L.) Coult. were excisedaseptically
medium.Root elongationwas very
liquid nutrient
and culturedin a modifiedBonner-Devirian
trace elementsand
slow in the basic mediumwhich containedinorganicsalts, B-vitamins,
4%o sucrose. The additionof planthormonesincludinggibberellicacid, indoleaceticacid, and
had littleeffecton growth.Myoinositolat 10 or 100 ppm
zeatin,alone or in combinations,
doubled the rate of elongation.The effectof this sugar alcohol could not be replaced by
scyllitol,D-sorbitol,D-mannitolor by increasingthe sucroseconcentration.Subculturedroot
of the
less elongationin successivetransfers.Secondarythickening
tips showedprogressively
rootswithout
roots,especiallyin thebasal half,occurredin initialpassagesand in subcultured
especiallyin the basal portionsof
added hormones.Root buds also occurredspontaneously
culturedroots,both in firstand in successivepassages. An anatomicalanalysisshowedthat
thesebuds were endogenous,arisingfroma secondarycortexof pericyclicorigin.
in effortto establishisolated roots of Comptoniain
speciesgrowing
ofherbaceous
culturesolutionshave providedex- sterilenutrient
sterilenutrient
culture.
perimentalsystemsforthe studyof variousprobAND METHODS-Collectionand gerMATERIALS
lateralroot and bud
lems includingrootnutrition,
of Comptonia followedproceof
fruits
mination
formation,secondarythickeningand nodule development(Torrey, 1965). Althoughestablish- duresreportedby Del Trediciand Torrey(1976).
ing roots of woody plants in culturehas been a Root tipsused to initiateculturesweretakenfrom
difficult process, limited success has been seedlingswhichhad been startedfromseeds gerachievedwiththefollowingplants: Acacia melan- minatedon a sterileagar nutrientmediumconoxylonR. Br. (Bonner, 1942), Robinia pseudo- taining10 ppm gibberellicacid (GA3). Whenthe
acacia L. (Seeliger, 1956), Pinus spp. (Slankis, radicle of the germinatedseed had reached 2-3
of the
1947; Barnes and Naylor 1959; Ulrich, 1962), cm in length,the terminalone-centimeter
to
Acer rubrumL. (Bachelard and Stowe, 1963) radiclewas excised aseptically,and transferred
50 ml of liquid-modified Bonner-Devirian(BD)
and Picea abies L. (Momot et al., 1974).
Comptoniaperegrina(L.) Coult. (Myricaceae) medium (Torrey, 1956) in a 125-ml erlenmeyer
is a woody shrubcommonlyfoundin easternand flask. The modifiedBD medium contained the
centralNorthAmerica. The rootsystemof Comp- followingcomponents(in mg/l of glass-distilled
toniaconsistsof a taproot,numerouslateralroots water): 242 Ca(NO3)2 4H20, 42 MgSO4 7H20,
and specializedhorizontal 85 KNO3, 61 KCI, 20 KH2PO4, 2.5 FeCl3 6H20,
and a fewwide-ranging
roots from which sprouts are readily formed. 0.1 thiaminHCI, 0.5 nicotinicacid, 0.5 pyridoxine
by these HCI, 1.5 H3B03, 1.5 ZnSO4 7H20, 4.5 MnSO4
Comptoniapropagatesitselfvegetatively
root sprouts,forminglarge clonal populations. H20, 0.25 NaMoO4, 0.04 CuS04 5H20, 40,000
Infectionof the root by a soil actinomycete-likesucrose,withthe pH adjustedto 5.5 beforeautoorganismresultsin the formationof root nodules claving. Any furtheradditionswere made after
nitrogen(Zieglerand cold sterilizationof the solutionwith a Millipore
capable offixingatmospheric
Hiiser, 1963). Because of interestin the process filter. The root.cultureswere incubated in the
of nodule formationin these roots,we made an dark at 25 C. The elongationof the main axis of
each root was measured and recorded weekly.
' Received for publication25 August 1976; revision At the end of a 6-8-wk period of cultureonecentimeter
tips of the activelygrowingrootswere
accepted8 November1976.
The authorsare indebtedto Peter Del Tredici for excisedand subcultured.The bases of the actively
providingseeds and seedlingsof Comptonia,to Kathy growingroots were then transferred
to a growth
roots,to Monica MattKamo for assistancein culturing
hr
hr
12
of dark at
light
and
chamber
with
12
of
in histologicaland photographic
mullerfor instruction
lightswith a
techniques.The researchwas supportedin part by re- 25 C. Mixed whiteand fluorescent
search grantBMS 74-20563 fromthe National Science total intensity
of about 260 ft-cwere used.
Foundation and in part by the Maria Moors Cabot
for
anatomicalstudywas handled by
Material
Foundationfor BotanicalResearchof HarvardUniverstandardparaffinmethods;the roots were fixed
sity.
ISOLATED ROOTS
.
.
476
April, 1977]
GOFORTH
AND
TORREY-CULTURE
OF ROOTS
8
II
7
10_
6
9-
Z~~~~~~
A
0
8
*
53
7 -
'p3~~~~~~~~~~~~~~~~~1
5 -
A
4-.
I
2
A
6
2
oI
C
477
IN COMPTONIA
I
3
I
4
Time (weeks)
I .
5
J
~AO
6
Fig. 1. The effectof varioushormoneson the rate
of elongationof isolatedroots of Comptonia. *-BD
withno addition;A-10 ppm GA2; V-1.0 ppm IAA;
0-0.1 ppm IAA; A-1.0 ppm zeatin; 0-10.1 ppm
zeatin.
0
*
4
~~V
& o
24 L
0~~~~~
O. , 1I
V
v
I . I
3
2
I
4
I
5
G
in formalin-acetic acid alcohol, dehydrated
Time (weeks)
alcohol series,embedded
througha tertiary-butyl
in Tissueprep,and sectionedat 10 ,Am.The secof myoFig. 2. The effectof variousconcentrations
tions were stained with Delafield's hematoxylin inositolon the rate of elongationof isolated roots of
and safranin.
Comptonia. Hexagon-BD with no additions; 0-1,000
ppm myoinositol;A-500
ppm myoinositol;0-100
*-1.0 ppm
RESULTS-The effectsof plant growthsub- ppm myoinositol;A-10 ppm myoinositol;
stances on root elongation-Excised root tips of myoinositol;V-0.1 ppm myoinositol.
Comptoniagrownin BD mediumwithno added
main-axis
growthsubstancesshowed insignificant
elongation,i.e., approximately4 cm in 8 wk. that of ConvolvulusarvensisL. at 20 mm/day
Testsweremade of a numberof plantgrowthsub- (Bonnett and Torrey,1965). As the roots mastances known to be importantin root develop- tured they became thicker,and formedlaterals
ment (Torrey, 1976). The addition to the BD and root buds (Fig. 4). Differentconcentrations
mediumof 10 ppm GA3, whichwas essentialfor of myoinositolwere tested as a supplement
on root
(Del Trediciand Torrey,1976), to the BD mediumfortheireffectiveness
seed germination
effect(Fig. 1). Indole- elongationin Comptonia. Both 0.1 and 1.0 ppm
had a slightstimulatory
acetic acid (IAA) at 0.1 and 1.0 ppm inhibited myoinositolelicited a suboptimalresponse. Ten
main axis elongation,but stimulatedlateral root ppm and 100 ppm myoinositolproduced esseninitiation.Zeatin at 0.1 and 1.0 ppm also had an tiallythe same rate of elongation. Higher concentrationsof myoinositolwere probably supraeffecton root elongation.
inhibitory
in rootelongationwas optimal. Combinationsof myoinositoland other
A dramaticimprovement
shownupon the additionof 100 ppm myoinositol growthsubstances(GA3, IAA, and zeatin) were
to the medium (Fig. 2), producingan average added to the culturemedium (Table 1A). Alelongationof 20 mm/wk,a ratesimilarto thatof thoughGA3 + myoinositoland zeatin+ myoinoroots of pea (Pisum sativumL.) at 15 mm/wk sitolcaused a higherrateof elongationthaneither
(Bonner and Devirian,1939), but not as rapid as GA3 or zeatin alone, neithercombinationwas as
[Vol. 64
AMERICAN JOURNAL OF BOTANY
478
1.
Mean length in cm ? standard deviations
(S.D.) of the main axis of cultured roots of Comptonia peregrina measured after 6 wk. Each experiment included at least 10 initial root tips. A. The influence of combinations of growth substances. B.
The effectof increased sugar concentrationor other
sugar alcohols.
TABLE
I0
-
E8
s6 -
_38
Length in cm (? S.D.)
Medium
TABLE A
4.0 ? 1.4
BD alone
100 ppm myoinositol
+
5.0?3.8
+
5.2
+
5.8?4.0
0.1 ppm IAA
100 ppm myoinositol
1.0 ppm GA3
100 ppm myoinositol
0.1 ppm zeatin
100 ppm myoinositol
1.5
?
0.1 ppm zeatin
5.5 ?4.5
+
0.1 ppm IAA
100 ppm myoinositol
9.1 ? 3.6
TABLE B
8% Sucrose
100 ppm D-sorbitol
100 ppm Scyllitol
100 ppm D-mannitol
5.1?3.5
5.0 ? 3.3
4.9 ? 3.2
3.5 ? 3.2
alone. IAA was
as 100 ppm myoinositol
effective
consistentlyinhibitoryto root elongationat the
concentrations
tested.
Carbon sources and sugar alcohols otherthan
myoinositolwere also tested (Table 1B). When
the sucrose level of the basic BD medium,i.e.,
withoutadded growthsubstances,was raisedfrom
2 % or 4 % to 8 %, the rateof root elongationincreased. This growthrate was not as rapid as in
4 % BD plus 100 ppm myoinositol.Of the sugar
alcohols tested, scyllitolwas structurallymost
similarto myoinositol.However, 100 ppm scyllitol added to BD mediumwith4 % sucrose had
no effecton root growth.Roots culturedin 4 %
sucrose BD mediumplus 100 ppm mannitolor
plus 100 ppm sorbitolhad slow growthratesvery
similarto 4 % sucrose BD mediumalone.
Attemptswere made to establish continuous
cultivationof rootsof Comptoniaby repeatedsubcultureas has been done in tomato,Lycopersicon
esculentumL. (White, 1938), Convolvulus(Torrey, 1958) and otherroots. At the end of a culture period of 6-8 wk, one-centimeter
tips were
removed from activelygrowingroots and were
subculturedin BD + 100 ppm myoinositol.This
?
2
4
6
2
46
2
Time (weeks)
4
6
2
4
6
Fig. 3. The rate of elongationof isolated roots of
Comptonia culturedin BD medium+ 100 ppm myoino-
sitol throughthreesuccessivesubculturesof six weeks
each. c -BD + 100 ppm myoinositol;
E1 BD withno
additions.
process was repeated three times in succession
(Fig. 3). The subculturedroots declinedin root
lengthand in diameterand often in vigor, but
maintainedthe abilityto formroot buds and appeared to be thickened.Most of the root growth
in subculturedrootswas in lateralroot formation
and in the developmentof elaboratelybranched
roots (Fig. 5). Because only main axis elongation-was measuredand recorded,an accuraterepresentationof subculturedroot growthwas not
easily obtained fromthese experiments.It was
apparent,however,that indefinitesubcultureof
Comptoniaroots in BD mediumwith a myoinositol supplementwould not be sustained.
Secondarythickening-In the BD cultureme-
diumwithadded myoinositol,
Co!mp-tonia
roots
underwentsecondarythickening,increasing3-4
times the diameterof the original excised tip.
The thickenedarea extendedalong a large portion of the proximalhalf of the root as is seen
in Fig. 4. The initial excised tip at the time of
inoculation was approximatelythe diameter of
one of the smallerlateralsin the photograph.In
was
rapidlyelongatingroots secondarythickening
initiatedbefore 6 wk. Thickeningwas also observed in a slow-growingroot continuallyculturedin 4 % sucrosemediumfor6 months.Roots
showed
developed fromradicle tip-sof embryo-s
thickeningeven if theywere not elongating,but
the thickeningprocess took longer. Actively
growingsubculturedroots also thickened (Fig.
appeared more slowly
5), althoughthe thickening
with each successive transfer.There was often
visiblea longitudinalsplittingof the outercortex,
especiallyon the proximalend of the root. The
turnedgreenwhen the
thickenedareas frequently
white
culturedroots were placed in low-intensity
fluorescent
light.
An anatomical studywas made of the thickened roots. Figure 6 shows a cross sectionof an
unthickenedportionof a root withprimaryxylem
April, 1977]
GOFORTH AND TORREY-CULTURE
OF ROOTS IN COMPTONIA
479
froma radicletip
Fig. 4, 5. Culturesof isolatedCornptonia roots. 4. A rootculturedin 100 ppm myoinositol
excisedfroman embryo.The arrowsindicaterootbuds. X 1.5. 5. Threesubcultured
roottipsgrownin BD + 100
ppm myoinositol.The arrowsindicaterootbuds. X 1.5.
arrangedin a tetrarchpattern. The primarycorFigure9 shows a cross sectionof a Comptonia
tex is intact and contains many intercellular root withthe apical meristemand leaf primordia
spaces. A cross sectionof an older regionof the of the root bud clearlyvisiblein longitudinalsecsame root is shown in Fig. 7. Secondaryxylem tion. Comptonia root buds appear to originate
formedbetween the arms of the primaryxylem in the secondary cortex opposite a protoxylem
is evidence of cambial activity. The pericycle pole. Because the secondarycortexis formedby
has undergoneone or more divisions,formingthe the pericycleor frompericyclicderivatives,the
beginningof a secondarycortex. The primary rootbuds are endogenousin origin. The vascular
cortexhas begun to slough off. In roots which connectionof the rootbud to the main rootforms
become more thickened,a solid core of second- at a later stage than that shown in Fig. 9.
ary xylem is evident (Fig. 8). Radial rows of
DISCUSSION-The successfulcultivationof isoparenchymacells formxylemrays in this region.
A limitedamountof secondaryphloemoccurs to lated rootsof woody species would providea usethe outsideof the secondaryxylem. The second- fultool forstudyinga varietyof problemsin relaary cortex is derived from proliferationof the tion to plant formand function.It is interesting
pericycle. The suberized and corkyouter layers to considerwhyrootsof so few species of woody
suggestthe activityof a phellogenand the forma- plants have been established in culture. Relativelyfew attemptsmay have been made. Diftion of a bark-likeouter layer.
ficultiesin inducingseed germinationmay have
Root bud formation-Root buds developedon limitedthe sources of sterileroots for the initial
the proximal ends of culturedComptonia roots cultures. Isolated roots of woody species may
(Fig. 4). Only four other species of cultured have had requirementsfor special factorsessenroots,Robinia pseudoacacia L. (Seeliger, 1956), tial for growthnot discovered from studies of
ConvolvulusarvensisL. (Torrey, 1958), Linaria herbaceous roots. The requirementfor myoinovulgaris(Charlton,1965), and Isatis tinctoriaL. sitol by isolated Comptonia roots is an example
(Danckwardt-Lilliestr6m,
1957) have been re- of sucha factor.
ported to formendogenousroot buds regularly. Myoinositolappears to be an essential comThe root buds firstappeared as small primor- ponentforthe growthof isolated roots of Compdia along the proximalend of roots culturedin tonia grownin sterileculture. In the firstculture
the dark. When placed in light,the shoot elon- period the presence of myoinositoldoubles the
whicheven- growthof the roots and thereafter
gated and formedleaf-likestructures
makes possible
tually expanded into small leaves which turned the subculturingof roots over several passages.
green,thendark burgundyin color.
The effectiveconcentrations,i.e., 10-100 ppm,
480
w p
a
i
cosscino
s(
[Vol. 64
AMERICAN JOURNAL OF BOTANY
s
l
s
()
S
i
s
itat
n
a thickee areaf
x
2
xylem(sx) iseviden.Di
ct
A
t
h
s
e
sti
hdwith
d
i
o
a
he
o
ai
np
e
s
lt.
a
i
f
g
t
thepericye forin
t
r
..':200.
8..
St~~~~Is
I...
....
(sx)habeenfrmedwthraysof.parnchymaellsi
thscreio
peripheryofte
thisregion Somesecondaryphloem(sp)isevi
th secodar corThe seconarycortex(s)a s folrmed.inThc brightlysbirefringent
cellshingof
tex containcalciumoxalate crystals.X 100. 9. A cross sectionof part of a root witha longitudinalsectionof a
(lp are well formed.X 100.
rootbud in thesecondarycortex. The apical meristem(am) and leaf primordium
April, 1977]
GOFORTH AND TORREY-CULTURE
OF ROOTS IN COMPTONIA
481
between thickenafterroot decapitation. In the absence
indicatethatit servesa role intermediate
thatof a substrateand a co-factoror vitamin. In of an apical meristemthe lateral root primordia
this respect, myoinositolbehaves in a manner were foundto play an active role in determining
similarto that reportedfor the growthin vitro the differentiation
of the vascular tissues. It was
of some plantcallus tissues (Braun, 1958; Mura- assumed that naturallyproduced auxin was inshige and Skoog, 1962; Shantz,Sugii, and Stew- volvedin theprocess.
ard, 1967) and forresponsessuch as thatof secLoomis and Torrey (1964, 1967a, b) found
ondarythickening
in excisedrootsof radishgrown theycould induceisolatedradishroots (Raphanus
with basal feeding (Loomis and Torrey, 1964; sativus L.) to undergo secondarythickeningin
Torreyand Loomis, 1967a, b). Recently,Kaul cultureby addingkinetin(5 x 10-6 M) and inand Sabharwal (1975) reportedmyoinositolto doleaceticacid (10-5 M) to the sucrose and salts
be essential for the survival of callus tissue of in the mediumprovidedto the rootbase in a vial.
Haworthiagrownin sterilenutrientculture.
The furtheradditionof myoinositolat 100 ppm
The role of myoinositolin plant metabolismis to the basal feeding medium stimulatedroot
not fully understood. According to Loewus growthand greatlypromotedthickening.Myo(1971), myoinositolserves as an importantsub- inositolalone did not inducedthickening.Peterstratefor cell wall synthesis,being oxidized to son (1973) reportedan essentiallysimilarresponse
form glucuronic acid which is polymerizedto in culturedroots of turnip(Brassica rapa L.).
polysaccharidesincorporatedintothe primarycell
The initiationof a vascular cambiumand the
wall. Jung, Tanner, and Wolter (1972) have formationof secondaryvascular tissues in culpresentedevidence which demonstratesan im- turedroots of Comptoniaare unusual in thatno
portantrole for myoinositolfor the functioning exogenous hormonesupply was required. Most
of cell membranes. In eitherrole and possibly of the isolated Comptonia roots which were
others, a limitingsupply of myoinositolcould started from an embryonicroot tip thickened
limit growth. In Comptonia apparentlythe ex- whetheror not theyunderwentactive elongation.
cised root is unable to synthesizeamounts of Subculturedroots thickenedonly if root elongamyoinositoladequate to meetits needs forgrowth tion occurred,eitherin the main axis or in the
and must be provided the growthfactor exog- laterals. This thickeningwas slowerthan that in
enously.
the embryonicroot tips. This evidence suggests
However,fromthe growthdata presented(Fig. thattheremay be some carryover of substances
with fromthe embryowhich cause thickening.How3), it is clear thatBD mediumsupplemented
myoinositolis not a "complete" medium. Con- ever, thickeningin subculturedroots is caused
tinuous growthof Comptonia throughrepeated by somethingsynthesized
by the root.
subculturehas not been possible with this meAnotherinteresting
featureof isolated Compdiumand a further
searchmustbe made forother toniarootsis theirabilityto formrootbuds. Torfactorsor conditionsto make continuousculture rey (1958) and Bonnettand Torrey (1966) deofComptoniarootspossible.
scribed in detail the developmentof root buds
Growth in roots of Comptonia is difficultto in ConvolvulusarvensisL., which differconsidbecause of the complex- erably from those of Comptonia. Convolvulus
determinequantitatively
ityof the branchinghabit (Fig. 4, 5). Measure- root buds are formedon roots possessing only
mentsof lineargrowthof the main axis presented primarytissuesand are initiatedby cell divisions
in Fig. 1-3 and Table 1 do not representthe in the pericycleopposite a protoxylempole. A
growthresponse adequately. Furthermore,with meristematicdome of cells is organized at the
repeatedbranching,the lateralrootsbecome pro- outerperipheryof the primordium.The firstxygressivelyfiner,easily damaged in handling,and lem elementsare initiatedobliquelyto the xylem
difficult
to use for subculture.An improvedme- of the root. By two weeks the bud apex and its
dium may increasethe vigorof subculturedroots leaf primordiahave penetratedthe outer cortex
and theirbranchesso as to obviatetheseproblems. and epidermisoftheroot.
The formationof secondarytissuesin cultured
The root buds on Comptonia roots, although
roots is an interestingoccurrenceand provides ,notarisingfromprimarytissue,are also endoganother experimentalsystem for studyingthis enous in origin. They arise opposite a protodevelopmental process. Dormer and Street xylem pole in the secondary cortex which is
(1948) firstobservedsecondarythickeningin an derivedfromthe pericycle. At the time of bud
isolated tomatoroot grownin continuousculture initiationthe root has enlargedby the formation
for 6 months,a reportvery similar to our ob- of secondarytissuesand the outerprimarycortex
servationof a 6-month-old
Comptoniarootwhich has been split and sloughed off. The vascular
had thickenedafterculturein 4% sucrose BD connectionof the rootbud developsafterthe formedium. There have been reportsof secondary mationof the apex and leaf primordiaand conthickeningin culturedroots in response to ma- nectsto the secondaryxylemof the root.
nipulationor additionof growthregulators.TorRoot buds play an important
role in thevegetarey (1951) reportedthatculturedpea rootswould tive propagationof manyplant species. Peterson
482
AMERICAN JOURNAL OF BOTANY
[Vol. 64
(1975) has writtenan extensivereview on the MoMOT,T. S., I. A. ARMAN, S. F. SZMAYLOV,
A. M.
SMIRNOV, AND A. A. YATSENKO-KHEMLEVSKI.
1974.
initiationand developmentof root buds. Root
Amino acid biosynthesis
in isolatedroots and terbuds allow plants to form large clones and to
minalcallus tissuesof theEuropeanfir(Picea abies
cover extensiveareas. When the rootsystemsare
(L.) Karst.). Izv. Akad. Nauk. SSSR, Ser. Biol.
disrupted,the plant has the abilityto formnew
666-671.
plants,thus maintaininga strongholdin the area. MURASHIGE,
T., AND F. SKOOG. 1962. A revisedmeVegetativepropagationof Comptoniaby rootbud
dium for rapid growthand bioassayswithtobacco
formationon horizontallyspreadingrootsmay be
tissuecultures.Physiol.Plant. 15: 473-497.
the primarymeansof increasein thisspecies.
PETERSON,
R. L. 1973. Controlof cambial activityin
roots of turnip (Brassica rapa).
LITERATURE CITED
Can. J. Bot. 51:
475-480.
. 1975. The initiationand development
of root
BACHELARD,
E. P., AND B. B. STOWE. 1963. Growthin
buds,p. 125-161. In J. G. Torreyand D. T. Clarkvitroof roots of Acer rubrumL. and Eucalyptus
son [ed.], The developmentand functionof roots.
canaldulensisDehn. Physiol. Plant. 16: 20-30.
AcademicPressInc.,London.
BARNES,R. L., AND A. W. NAYLOR. 1959. In vitroculture of pine rootsand theuse of Pinusserotinaroots SEELIGER,T. 1956. tber die Kultur isolierterWurzeln die Robinie (Robinia pseudoacacia L.) Flora
in metabolicstudies. For. Sci. 5: 158-168.
144: 47-83.
BONNER, J., AND P. S. DEVIRIAN.
1939. Growthfactor
requirements
of fourspeciesof isolatedroots.Amer. SHANTZ,E. M., M. SUGII,AND F. C. STEWARD.1967.
J.Bot. 20: 661-665.
The interactionof cell divisionfactorswith myo. 1942. Culture of isolated roots of Acacia
inositoland theireffecton culturedcarrottissue.
melanoxylon.Bull. Torrey Bot. Club 69: 130Ann.N.Y. Acad. Sci. 144: 335-356.
133.
SLANKIS, V. 1947. Influenceof the sugar concentraBONNETT, H. T. JR., AND J. G. TORREY.
1965. Auxin
tion on the growthof isolatedpine roots. Nature
transportin Convolvulusroots culturedin vitro.
160: 645-646.
PlantPhysiol.40: 813-818.
TORREY, J. G. 1951. Cambial formationin isolated
. 1966. Comparativeanatomyof
- AND
pea roots followingdecapitation. Amer. J. Bot.
endogenousbud and lateralroot formation
in Con38: 596-604.
volvulusarvensisroots culturedin vitro. Amer. J.
. 1956. Chemical factorslimitinglateral root
Bot. 53: 496-507.
formation
in isolatedpea roots. Physiol.Plant. 9:
BRAUN,A. C. 1958. A physiologicalbasis for auton370-388.
omous growthof the crowngall tumorcell. Proc.
. 1958. Endogenous bud and root formation
Nat. Acad. Sci. (U.S.) 44: 344-349.
by isolated roots of Convolvulusgrownin vitro.
CHARLTON, W. A. 1965. Bud initiationin excised
PlantPhysiol.33: 258-263.
roots of Linaria vulgaris. Nature 207: 781-782.
. 1965. Physiologicalbases of organization
and
1957. Kinetin-induced
DANCKWARDT-LILLIESTR6M, C.
in theroot,p. 1256-1327. In W. Ruhdevelopment
shoot formationfromisolatedroots of Isatis tincland [ed.],Encyclopediaof plantphysiology.XV/1.
toria. Physiol.Plant. 10: 794-797.
. 1976. Root hormones and plant growth.
DEL TREDICI, P., AND J. G. TORREY. 1976. On the
Annu. Rev. Plant Physiol. 27: 435-459.
germination
of seeds of Comptoniaperegrina,the
, AND R. S. LooMIs. 1967a. Auxin-cytokinin
sweet fern. Bot. Gaz. 137: 262-268.
controlof secondaryvascular tissue formationin
DORMER, K. J., AND H. E. STREET.
1948. Secondary
isolated roots of Raphanus. Amer. J. Bot. 54:
thickeningin excised tomato roots. Nature 161:
1098-1106.
483.
.
, AND
1967b. Ontogeneticstudies of
JUNG,P., W. TANNER, AND K. WOLTER. 1972. The
vascular cambium formationin excised roots of
fate of myo-inositol in Fraxinus tissue cultures.
Raphanus sativus L. Phytomorphology
17: 401Phytochemistry11: 1655-1659.
409.
KAUL, K., AND P. S. SABHARWAL. 1975. Morphoforgrowth
genetic studies of Haworthia: effectsof inositol on ULRICH, J. M. 1962. Culturalrequirements
of excisedponderosapine roots. Physiol.Plant. 15:
growthand differentiation.Amer. J. Bot. 62: 65559-71.
659.
LOEWUS, F. 1971. Carbohydrate conversions. Annu. WHITE, P. R. 1938. Cultivationof excised roots of
Rev. Plant Physiol. 22: 337-364.
dicotyledonousplants. Amer. J. Bot. 25: 348356.
LooMIs, R. S., AND J. G. TORREY. 1964. Chemical
control of vascular cambium initiation in isolated ZIEGLER, H., AND R. HUSER. 1963. Fixationof atmoradish roots. Proc. Nat. Acad. Sci.
3-11.
(U.S.)
52:
spheric nitrogen by root nodules of Comptonia
peregrina.Nature199: 508.