lt
Ann. Bot. 43, 459466, 1979
Gomparisonsof Earlier-and Later-formed
Pods of Pigeonpeas(Cajanuscajan (L.) Millsp.l - \
A . R . S H E L D R A K E a n dA . N A R A Y A N A N *
International Crops ResearchInstitute Jbr the Semi-arid Tropics(ICRISAT),
Hyderabad-5000
I 6, A.P., India
Accepted:8 February 1978
ABSTRACT
On branchesof indeterminatecultivarsof pigeonpea,floweringbeginsat the basalnodesand proceeds
acropetally;in morphologicallydeterminatecultivars,ffoweringbeginson the apical racemesand proceedsbasipetally.In cultivarsof both types,within the racemesfloweringproceedsacropetally.Under
normal conditions more pods are set from earlier-formedflowers than from later-formed flowers, many
ofwhich are shed.Consequentlythe earlier-formedpods are found at the more basalnodes of racemes,
and in indeterminate cultivars at the more basal nodes on the branches.The averageweight of earlierand later-formed pods, collectedfrom the basal and apical nodes of the racemesor of the branches,was
similar; so was the number of seedsper pod, the weight per seedand the nitrogencontent of the seeds.
This pattern differs from that found in most herbaceouslegumes,where later-formed pods are smaller,
and indicatesthat pigeonpeasset fewer pods than they are capableof filling. This behaviourmay be
relatedto the intrinsicallyperennialnature of pigeonpeas.
The comparisonof the weightsof earlier-and
later-formed pods could provide a simple screeningprocedurefor identifying plants with an annual
nature among existingcultivarsor in breeders'lines.
Key words: Cajanuscajan (L.) Millsp., pigeonpea,pod development,seednumber, seedweight, nitrogen
content.
INTRODUCTION
In most legume crops the earlier-formed pods are larger than the later-formed pods and
contain more and/or heavier seeds (Sinha, 1977). The simplest explanation for this
phenomenon is that the filling of the later-formed pods is limited by the supply of
photoassimilatesor other nutrients. In such a situation seedyield may be limited by the
ability of the plants to supply developingpods with nutrients, rather than by the number
of pods set. On the other hand, if fewer pods than the plants were able to supply with
nutrients were set, the earlier- and later-formed pods might be expectedto develop to
a similar extent. For these reasons,the pattern of pod-set and pod-development could
shed light on the factors limiting yield rn a given speciesor a given cultivar.
We investigatedthesepatterns in pigeonpeas(Cajanuscajan (L.) Millsp.), an important
pulse crop in India and other parts of the semi-arid tropics. The plants grow into woody
shrubs which are intrinsically perennial, but are usually cultivated as annuals. Earlymaturing cultivars are harvested 4-5 months after planting, medium cultivars after
5-7 months and late cultivars after 7-10 months. Yields are relatively low (Pathak, 1970).
Generally less than 20 per cent of the dry matter produced by the plants is partitioned
into seeds(Sheldrake and Narayanan, in press).The plants flower profusely, but the
majority of the flowers drop off without setting pods (Howard, Howard and Khan, l9l9;
Mahta and Dave, l93l).
* Presentaddress:Departmentof Plant Physiology,Andhra PradeshAgriculturalUniversity,
Rajendranagar,
Hyderabad-50030,
India.
030s-7
364/ 79/030459+ 08 $02.00/0
O 1979Annals of Botany Company
460
Sheldrske and Narayanan - Earlier- and Later-formed Pods of Pigeonpeas
MATERIALS AND METHODS
Observations were made on pigeonpeasgrown in the field in 1974, 1975 and 1976 at
ICRISAT Centre, near Hyderabad, India. The plants were grown on two soil types,
a vertisol (fine clayey, calcareous, montmorillonitic, hyperthermic, family of Typic
Chromustert) and and alfisol (fine, clayey, mixed hyperthermic, family of oudic Rhodustalf). In all cases the soils were fertilized with single superphosphate(at the rate of
50 kg PrOuha-l) before sowing. Nitrogenous fertilizer was not supplied; the roots were
well nodulated by native Rhizobia.
The plants were sown at the normal time, in early July, soon after the beginning of the
monsoon, at the usual plant-to-plantspacingsof 50x30cm for the early cultivars and
75 x 30 cm for the medium and late cultivars. The cultivars were planted in randomized
block designswith two replications in 1974and 1975,and with four replicationsin 1976.
Theplotsizeswere9x2Om,4x5mand9xl0minthe3yearsrespectively. Irrigation
was not supplied. During the growing seasonthe plants were protected againstinsect
pests by sprays of endosulfan.
For the investigationofthe pattern ofpod-set on the branchesat least30 well-developed,
undamaged primary branchesof each cultivar were collectedat the time of harvest. For
each cultivar the pods borne on the basal (most proximal) pod-bearing node (node l),
the second pod-bearing node (node 2), etc. were separatedand the pod number, pod
d. wt seed number and seed d. wt were recorded. All weights were taken after drying
in an oven at 80'C for at least 2 days.
For investigation of the pattern of pod-set within the racemes,at least 100 racemes
whose pods were undamaged by insects were collected from each cultivar. In indeterminate cultivars, unless otherwise stated, these were collected from the more basal
pod-bearing nodes of the branches. The pods from the basal (most proximal) node of the
peduncle(node l), the secondnode (node 2), etc.,were separatedand data were recorded
as describedabove.
For comparisonsof,pods at the apical and basal nodesof the branchesof indeterminate
cultivars, samplesof rit least 100 pods were taken from each replicate plot. The cultivars
were grown in randbmized complete block designswith four replications.
Seedsfrom replicate samples were pooled and ground to a powder for analysis for
nitrogen by the micro-Kjeldahl method. The results are expressedas percentages,on
a d. wt basis.
RESULTS
The sequenceof foweritig and of pod-set
In most cultivars of pigeonpeathe main stem and branchesgrow indeterminatelyduring
the reproductive phase; flowering beginson racemesborne at nodes at or near the base
of the branches and subsequently.at more apical nodes. New flowering nodes continue
to develop as the branch grows (Fig. 1). Within the racemes flowering also proceeds
acropetally. Under normal conditions more pods are set from earlier- than from laterformed flowers, and more pods are borne at the nodes towards the baseof the branches
and of the racemes
ln several representativeearly and medium cultivars, comparison of the numbers of
pods with numberg of scars on the rac€mesat the time of harvest revealed that only
5-20 per cent of the flowers developed into mature pods. There was some abscission of
young pods, but relatively little compared with the abscissionof flowers.
Some pigeonpeacultivars form racemesat the apicesof the main stem and branches.
These are usually described as'determinate'cultivars (Reddy & Rao, 1974), although
the individual racemesdevelop indeterminately. New racemescontinue to be produced
sheldrake and Narayanan - Earlier- and Later-formed pods of pigeonpeas 461
Frc. l. A primary branch of cv. ICP-I showing flowers and developingpods. x 0.5.
462
sheldrake and Narayanan- Eorrier- and Later-formed pods pigeonpeas
of
from axillaryshoots.consequently,_
the sequence
in whichflowering
-----cbeginsat the nodes
of the main stemand branchesof these.ritiuu^ is basipetar.
Somecultivarsare intermediatebetweenthe typ.r iir"iiued
above,with a condensationof nodesat the apicalendsof the branches.
in such
no*ering
- beginson
racemesat sub-apicalnodesand proceedsboth acropetaily
"urliuurt
and basipetally.
Podsat dffirent nodesof the branches
In determinate
cultivars,morepodsdeveloped
at the apicalracemes
-' of the main stem
and branches,and fewerpodsat th, -o.e bfsal axillaryiu""_.r.
In indeterminate
cultivars,morepodswereformedor.r"."*.rlowards
the baseof the
branches'The seednumberpet pod and theweightperseed
rrom trrepodsformedat the
differentnodesremainedmorebr lessconstant.Data for
cv. ICp-l grown on two soil
typesare shownin Fig' 2' Yety similarpatternswerefound
in othercultivarsof different
durationgroups;suchpatternswereobservedin threet"";;;;ir"-;;ars.
The fluctuations
in the seed^number
per pod and weightper seedat trremore ap;'ruinoa.r,
wherethere
were very few fruits, resultedfrom tlie smallsamplesize.
o
!
o
E
o
E
o
or
$+.e#-o4.-oi\-
\7
a
t23456Zegto
t3
14 t5 t6
17 t8 t9
Frc' 2' (a) Number of pods per node (b), number of
seedsper pod and (c) weight per seedat
different
nodepositionJon
piima.y*t
rcp-Gffi;ii
;$,:.i;;.
i."riX (oiunaonalfisoi
Podsat dffirent nodesof the racemes
within the racemesmost of the pods were formed at the
basalnodes,arthoughin
racemesfrom the lowerpartsof the branchesof indeterminate
cultivarstherewasa tendencyfor the maximumnumberof podsto be found
ih;;;;; froximar nodeof the
inflorescence,
"ot of
"; the flower's
but at the secondoi thlrd nodes.Most
at the more apical
nodesof the inflorescence
wereshedwithout settingfru.it.This puitrrn is illustratedby
data for cv' ICP-l (Fig. 3); similarpatternswerefoind in
otherindeterminate
cultivars.
Sheldrakeand Narayanan- Earlier- and Later-formed Pods of Pigeonpeas 463
o
(l)
o
o
o
rf)
o
o.
too
6
o
o
o
50
o
6
o
o
(D
o
E
3
z.
67I9tOil
posilion
o s i l i o n in roceme
N o dee p
from the(a) basal
Frc. 3. Numberof podsandscarsat differentnodepositionswithin racemes
ofcv. ICP-I andwithin (c) terminaland(d) axillaryracemes
and(b) apicalpartsof thebranches
of cv. Pusaageti.tr Scars;ll pods.
The determinatecultivars bore fewer racemesper plant than did indeterminatecultivars
of comparable duration, but generallyproduced similar numbers of pods becausethere
were more pods per raceme. Flowering and pod-set continued for a longer time in the
determinate cultivars; consequently the maturation of their pods was spread over
a longer period than in indeterminate cultivars of comparable duration. The greater
number of nodes and pods on the racemesof the determinatecv. Pusa ageti (Fig. 3) than
in cv. ICP-I reflect the longer period of flowering and pod development in the former
cultivar.
In the racemes,as on the branches,there was little or no tendencyfor later-formed pods
at the more apical nodes to be smaller than the earlier-formed pods at the more basal
nodes. Data for early, medium and late cultivars grown on two soil types are presented
in Table l. Only in the early cv.T-21 grown on vertisol was there a distinct decline in
pod weight at the more apical nodes.
The numbers of seedsper pod and the weights per seed, like the weights per pod,
changed very little from node to node in the different cultivars. Overall means for the
464
Sheldrake and Narayanan - Earlier- and Later-formed Pods of Pigeonpeas
Tngre L Weight per pod (mg) at dffirent node positions within racemes of diferent
cultivars grown on a vertisol (v) and an alfsol (A) in 1976, and the mean weight per pod at
the two most apical nodes expressedas a fraction of that at the two most basal nodes
Fraction:
apical
two nodes
basat
two nodes
Indeterminate
(r)
Cultivar
or
Days
determinate
to
(D)
flowering
T-2r
86
Pusa ageti
89
HY-2
105
BDN-I
rt2
AS-71-37
il5
rcP-6997
115
ICP-1
116
ICP-7065
147
NP(WR)-1s
155
ICP-7035
160
Node position within raceme
Soil
v
A
v
A
v
A
v
A
v
A
v
A
v
A
v
A
v
A
v
299
307
307
360
530
539
371
384
417
445
577
510
389
396
287
235
347
2s8
226
283 260
28r 271
311 302
342 366
525 531
505 463
37t 357
387 388
420 4t7
425 430
599 602
596 594
39',1 402
397 402
291 293
249 282
344 348
265 284
248 228
186
267
279
386
532
0.69
0.91
1.03
0.94
1.01
0.90
1.03
0.96
0.99
1.00
1.23
1.22
1'07
0.91
1.03
2t6
271
278 362
,:
t:
Aa1
381
384
382
418
633
753
441
362
304
382
356 , : _
450
4s6
't03
,2
361
296
LIJ
294
350 358
302 3 1 9
268 281
tn;
302 313
339
273 280
275 249
t'z I
r'01
1.06
1.11
Tenr.r 2. Mean weight per pod, seednumberper pod, and weight per seedat thefirst four
nodes of the rocemes of ten pigeonpea cultivars grown on tu'o soil types (cultivars and soils
qs shown in Table 1\
Node position in raceme
Weight per pod (mg)
Seedsper pod
Weight per seed(mg)
425
3.15
99
442
3.17
95
427
3.28
93
449
3.25
95
first four nodes are shown in Table 2. In cv, T-21 grown on vertisol the lighter pods at the
more apical nodes had fewer seedswhich were also smaller than those at the basal nodes.
Comparisons among cultivars
The observations described so far indicate that there is little or no tendency for the
weight of later-formed pods of pigeonpeasto decline relative to the earlier-formed pods.
However, data for cv.T-21 (Table l) suggestthat there may be cultivaral differencesin
this respect. In an attempt to detect such differences, we compared pods collected from
the basal racemes with pods collected from the apical racemes on the branches of
indeterminate cultivars. If there were a systematicdecline in the weight of later-formed
pods, the averageweight ofthe pods from the apical racemesshould have been lessthan
that of the pods from the basal racemes.
Sheldrake and Narayanan - Earlier- and Larcr-formed Pods of Pigeonpeas
465
In 1975,sampleswere collectedfrom 2l medium- and late-duration cultivars grown on
vertisol. The averageweights per pod from the apical racemesexpressedas a fraction of
those from the basal racemesranged from 0'92+0.03 to 1.2110.06. The overall mean
was l'04.
In 1976we compared the pods from apical and basal racemesof 22 cultivars (including
seven of those studied in 1975),ranging in duration from extra-early to late, most of
which were grown on both alfisol and vertisol. The weight per seed of these cultivars
ranged from 60-190 mg. The overall mean weights per seedfrom the pods at upper and
lower nodes were l0l and 102mg respectively;the mean numbers of seedsper pod were
3'30 and 3'29 respectivelyand the mean weightsper pod were 505and 506 mg respectively.
The averageweight per pod from the upper nodes expressedas a fraction ofthat from
the lower nodes ranged from 0.90 + 0.05 to l'24 t0'04. Only in four cultivars, including
cv. T-21, was the fraction less than 0'95, suggestingthat there may have been a slight
decline in the weight of the later-formed pods, but in the remaining cultivars there was
no such suggestion.In cv. T-21 the fraction was 0.92.
Nitrogen content of the seedsfrom earlier- and later-formed pods
The seedsfrom pods collectedfrom the apical and basal nodeswithin the racemes,and
from racemes at the basal and apical parts of the branches of nine medium and late
cultivars were analysedfor nitrogen. There was little or no effect of pod-position on the
percentageof nitrogen in the seeds(Table 3).
TanrE 3, Percentageof nitrogen in the seedsfrompods collectedfrom the basal and apical
nodes of racemes, and from racemes at the basal and apical nodes of the branches ol'nine
pigeonpeacultivqrs grown on vertisol and on alfsol at Hyderabad in 1976
On branches
Within racemes:
vertisol
Cultivar
Basal
Apical
ICP-I
AS-71-37
BDN-I
tcP-6997
}IY.2
HY-3A
rcP-7375
ICP-7065
NP(WR)-15
Mean
3'50
3.49
3.48
3'44
3.14
3.40
3.24
J'J I
3.60
J'J
T
3.61
3.29
3'52
3.60
3.46
3.48
3'I J
3.20
3.32
3.38
Vertisol
Basal
3.50
3.30
3.64
J.J T
3.33
3.22
3.59
3.83
3 . 6r
3.48
Apical
3.46
3.50
3.65
3.14
3.53
3.15
3.65
3'49
3.78
3.48
Alfisol
Basal
Apical
3.31
3 . 3I
3.28
3.14
3.36
3.33
3.10
3.50
3'52
3.39
3.53
3.14
3.42
3'65
3.6s
3.60
3.41
J'J
I
DISCUSSION
The similarity in the averageweights of the earlier- and later-formed pods indicates that
the developmentof the later-formed pods was not limited by nutrient supply; this in turn
indicates that the yield was primarily limited by the number of pods set.
The failure of more flowers to set pods seems to be related primarily to internal
physiological balances within the plant. If earlier-formed flowers and young pods are
removed, pods are set from later-formed flowers which would otherwise have abscinded
(Sheldrake, Narayanan and venkataratnam, in prep.). These results are most simply
explicable in terms of competition by developing pods for assimilatesor other nutrients.
In general, the overall number of pods per plant is strongly influenced by the supply of
466
Sheldrake and Narayanan - Earlier- and Later-formed Pods of Pigeonpeas
assimilates,but the constancy of the weight per pod (under a given set of environmental
conditions) suggeststhat pod-set does not take place when the nutrient supply falls
below a threshold level (Sheldrake,in press).If more pods were set than could be filled,
the later-formed pods would be smaller than the earlier-formed pods, as in herbaceous
Iegumes such as Vigna aureus (Roxb.) Hepper (Sinha, 1977) and Cicer arietinum L.
(Sheldrakeand Saxena,1979).
This difference may be related to the fact that pigeonpeasare intrinsically perennial.
The reproductive phase of annuals, and indeed of monocarpic plants in general, ends in
death. All the plants' energies and nutrient reservescan be mobilized towards the
production offruit. Sucha fatal strategycould not, by definition, be adoptedby perennials,
especially in environments in which an unfavourable seasonfollows the reproductive
phase.In India, the reproductive phaseof pigeonpeasis followed by the hot, dry summer
when the plants depend on their deep root system for survival.
Any marked improvement of pigeonpeasas an annual crop seemslikely to dependon
the development of genuinely annual cultivars which produce more andf or heavier pods.
The yield of such cultivars should be limited not by the processof pod-setting but by the
ability of the plants to fill the pods. The averageweight of their later-formed pods should
therefore be less than that of the earlier-formed pods.
The method of comparing the averageweights of pods from the apical and basal nodes
of the branchesof indeterminate cultivars (or from the terminal and axillary racemesof
determinatecultivars) is simple enough to be used for screeninglargenumbersof cultivars.
The World Collection of pigeonpeagermplasmat this Institute has more than 5000
entries; it is possiblethat among them annual types already exist. This method seems
more likely to give reliable results than looking for annuality per se, since the death of
plant after the reproductive phase is influenced by many external factors such as pests,
diseasesand soil moisture. The identification of such plants in the germplasm collection
or in breeders'lines could provide a starting point for the developmentof higher-yielding
pigeonpeas.
ACKNOWLEDGMENTS
We thank Mr N. Venkataratnam for technical assistanceand Mr G. Ravi Kumar for
carrying out the nitrogen analysis.
The International Crops Research Institute for the Semi-Arid Tropics (ICRISAT)
receives support from a variety of donors Governments, foundations, etc., including
IBRD, IDRC, UNDP, USAID, etc. The responsibilityfor all aspectsof this publication
rests with ICRISAT.
LITERATURE CITED
HowARD,A., Howano,G. L. C. and KHIN, A. R., 1919.Studiesin the pollinationof Indiancrops.
Mem. Dep.Agri. India(Bot.ser.),10, 201-7.
in Cajanus
Mrnra, D. N. andD.cvp,B. B., 1931.Studies
indicus.lbid.19,l-25.
PATHAK,
G. N., I970.Redgram.ln PulseCropsof India,ed.P. Kachroo.IndianCouncilof Agricultural
NewDelhi.
Research,
of plantand
Rroov, P. and Reo,N. G. P., 1974.Inheritance
andrelationwith someyieldcomponents
floweringhabit in Cajanus.
IndianJ. Genetics
Pl. Breeding.34,94*9.
(Cajanuscaian).(ln
SHrr-oure, A. R., 1979.A hydrodynamicalmodel of pod-setin pigeonpeas
preparation.)
J. agric. Sci.
and Nluv.lNlN, A., 1979.Growth,development
andnutrientuptakein pigeonpeas.
Carn6.(in press).
N., 1979.The effectsof flower removalon the yield of pigeonpeas
and VrNrer.lnATNAM,
(Cajanuscajan).(ln preparation.)
of the earlier-and later-formedpodsof chickpeas(Crcer
and SaxrNn,N. P., 1979.Comparisons
arietinumL.) Ann.Bot. 43,467473.
andBiologyoJ'Yield.FAO PlantProduction
SrNnr,S. K.,1977. FoodLegumes:Distribution,Adaptability
and ProtectionPaper3. Food and AgricultureOrganizationof the UnitedNations,Rome.