J. Agronomy & Crop Science 178, 1—7 (1997)© 1997 Blackwell Wissenschufts-Verlag. BerlinISSN 0931-2250

Agronomy Division, Interuatiomil Crops Research Inslilutefor the Semi-Arid Tropics (ICRISATl. Paianclwru,Andhra Pradesh 502 324, India

Effects of Timing of Drought Stress on Leaf Area Development and CanopyLight Interception of Short-duration Pigeonpea

F. B. Lopez. Y. S. Chauhan and C. Johansen

Authors' address: Dr F. B. Lopez, Dr Y. S. Chauhan and Dr C. Johansen (corresponding author). International Crops ResearchInstitute for the Semi-Arid Tropics (ICRISAT) Asia Centre. Patancheru. Andhra Pradesh 502 324. India

U'iih line figure ami 7 loblcs

Reccircii Sepifiiihcr S. 1995: accepted July 12. 1996

AbstractLeaf area index {LAI}, fractional canopy light inter-ception (F) and plant mortality at maturity, were deter-mined for nine short-duration pigeonpea {Cajainis cajau[L.] Millsp.) genotypes in response to drought during thelate-vegetative and flowering (stress I), the flowering andearly podfill (stress 2), or podfill (stress 3) stages. LAIand F were reduced, but plant mortality did not increaseunder drought. Stress 2 reduced LAI to the greatestextent, consistent with the effects on seed yield. At theend of stress 1. seed yield was closely related to LAI forthe diflerent genotypes in stressed but not in unstressed(control) plots. Reductions in LAI due to reproductivegrowth were as great or greater than those due to waterstress. Indeterminate genotypes had smaller but moreleaves per plant compared to the determinate genotypes.The importance of these dilTerences to drought resistancewas not apparent. Production of leaves with decreasingspecific leaf area throughout plant growth may be advan-tageous, especially when drought is likely to occur duringreproductive growth. Values of F during and followingwater stress gave an indication of genotypic droughtresistance, with the most drought-sensitive genotypeshowing the largest reduction in F under water stress andthe slowest rate of recovery following rewaiering. Forshort-duration pigeonpea, where plant mortality is not afactor under water stress, the maintenance of both LAIand F appears to indicate genotypic droughl resistance.

Key words: Cojanus — pigeonpea — platit mor-tality — yield relationship

IntroductionIntermittent periods of drought can reduce growthand yield of short-duration pigeonpea (Cajanuscajan [L.] Millsp.) sown at the start of the rainyseason in India (ICRISAT. 1988, 1989). Seed yieldis most alTecled by drought occurring in the lateflowering and early pod development stages. Geno-typic differences in drought resistance are associated

with the maintenance of dry mass partitioning intoleaves during, and dry mass production following-drought periods (Lopez et al., 1996b). Dry matterproduction depends on canopy light interceptionand the efficiency of its con\ersion into dr\ matter.Both variables can be reduced when pigeonpea issubjected to water stress (Hughes and Keatinge.1983). Therefore- plant factors which favour themaintenance of canopy light interception underwater stress could tnake an important contributionto drought resistance, if photosynthetic rates areunaffected.

Canopy light interception is a function ofthe ratesof leaf production, expansion and abscission as wellas stand density and arrangement. For tnany grainlegumes, leaf area development (leaf production andexpansion) is more sensili\e to water stress than leafabscission (Muchow, 1985a). Tn faba bean (\'iciaJaha L.). the lower leaf area under water stress islargely due to reduced leaf expansion, with relativelyminor effects on leaf production and death (KaraManos. 1978; Farah. I9SI). During vegetativegrowth in soybean (Glyci/w nia.x [L.] Merr.), mildwater stress reduces leaf expansion to a greaterextent than leaf production with little apparentaffect on leaf senescence. Severe water stress,however, reduces leaf area largely by acceleratedleaf senescence (Muchow et al.. 1986).

In short-duration pigeonpea. leaf abscission istiiore sensitive to water stress in cultivars of deter-minate than in those of indeterminate growth habit(Lopez ct al., 1996a). More information is requiredon the mainlenance of leaf area and the canopylight interception under water stress in relation todrought resistance. The present study investigatedthe effects of drought stress on leaf area devel-opment, canopy light interception and plant mor-

U.SCopyriglu Clearance Center Code Stalemcm: 093 I - 2 2 5 0 / 9 7 / 7 8 0 1-0001 $14 .00 /0

Lopez, Chauhan and Johansen

tality of short-duralion pigeonpea genotypes of\arying growlli habits (determinate, indeterminate;early, late) and drought responses.

Materials and Methods

Crop establishment

The experiment was condueted in an Alfisol (Udie Rho-dustalt') licld at ICRISAT Centre. India (17 N. 78 E; 500m elevation), with shelters that closed automatically toprevent rain on an experimental area of 50 x 25 m. Thesoil had a maximum plant axailable water holdingeapacity of 60-100 mm. It was surface tilled inco-rporating 100 kg ha"' of diammonium phosphate, andridges spaced at 0.6 m were established. Prior soil analysesand plant growth tests had established that nutrientdeficiencies would be unlikely in this soil and that nativeRhizohiiuw were adequate to ensure optimum nodulationand nitrogen lixation of pigeonpea. Seeds were handsown on 7 July 1988. with two plant-rows (0.3 m apart)established on both sides of ridges and a spacing of O.Im within rows. Agronomic operations were carried outas necessary for adequate protection against pests, dis-eases and weeds. During the early growth stages, theexperimental plots depended entirely on rainfall, and nosupplemental irrigations were given. From 52 days aftersowing (DAS), the automatic rain shelters were activatedto exclude rainfall and differential irrigation treatmentscommenced.

Experimental design and treatments

The experiment was laid out as a split-plot design withfour replications. The four drought stress timing treat-ments applied in the main plots were: (a) Control—Opti-mum moisture (maintained near Held capacity) through-out the crop growth period; (b) Stress 1—Water withheldfrom 52 DAS until about 50% leaf abscission in ICPL87 {88 DAS); (c) Stress 2- Water withheld from 50%flowering of ICPL 87 (78 DAS) until about 50% leafabscission (102 DAS); (d) Stress 3—Water withheld frommid-podfill of ICPL 87 (110 DAS) until harvest (133DAS). Main plots were 10.5 x 3.6 m and were separatedfrom each other by a 1.2 m wide border strip planted toICPL 87. Water was applied by drop irrigation at inter-vals of 2-4 days depending on surface soil dryness incontrol plots. A flow meter on the main irrigation lineindicated the amount of water applied on each occasion.Drought stress treatments were applied by closing lateralirrigation lines to specified plots.

Nine short-duration pigeonpea genotypes (sub-plottreatments) with varying growth habit (I = in-determinate. D = determinate), and other (H = hybrid,E = extra-early) characteristics were used in the study:(1) ICPL 8 7 - D; (2) ICPL 151—D; (3) ICPL 85010—D;(4) ICPL 85045—1; (5) ICPL 85043 -I; (6) ICPH 8—1,H; (7) ICPH 9—D, H; (!S) ICPL 84023—D. E; (9) ICPL85037^1, E. Each sub-plot consisted of four rows (3.5 mlong) on two adjacent ridges.

Leaf area and plant mortality

Three plants were randomly selected and whole shootsremoved from control and stressed plots at terminationof stress 1 (88 days after sowing; DAS) and stress 2 (102DAS), and five plants were similarly removed from allplots at the final harvest (133 DAS). On each occasion,the total leaf area (LA) of one plant from each plotwas determined by an area meter (Delta T Devices Ltd,Cambridge, England), and the number of leaves countedfor all plants sampled. Leaf dry mass (LM) was deter-mined after drying in an oven at 80 C. The specific leafarea (SLA) was calculated as LA/LM. using all leavesfrom a single plant, and this was used to obtain LA forthe remaining plants sampled (LA - LM xSLA). Theleaf area index (LAI) was calculated as the product ofthe average leaf area plant"' and the number of plantsm~". with the latter detennined along with plant mor-tality at final harvest.

Canopy light interception

Canopy light interception (F) was determined at mid-dayby measurements using a quantum sensor (LI-COR Inc.,Nebraska, USA) above, and a line quantum sensor (1.0 mlong; LI-COR Inc.) below the eanopy. Single observationwas made in each replication. Measurements of F weremade in stressed plots during development and just beforetermination of the drought treatments, and corres-ponding measurements were made in control plots onthese occasions.

Data analysis

Data were analysed using standard analysis of varianceprocedure and regression analysis using GENSTAT soft-ware. The two earliest flowering genotypes produced asecond flush of pods by the time of final harvest and weretherefore omitted from the analysis.

Results

Leaf area index (LAI)

Water stress reduced LAI by 25-45 % at the end ofstress 1. and by 40-60 % at the end of stress 2 (Table1). Under stress 1, the LAI was affected most forICPL 151, and least for the hybrids, ICPH 9 andICPH 8. Under stress 2. the LAI was most affectedfor ICPL 87 and least affected tor ICPL 151 andICPH 8. At final harvest, which coincided with theend of stress 3, the LAI was < 1.0 for all genotypes,with very little effect of the soil moisture treatmentand high variability among replications (data notshown). There was a significant positive relationshipbetween seed yield in the stress 1 (/•" = 0.98) andstress 2 ( r = 0.63) treatments whereas no suchrelationship was apparent between yield and LAI inthe respective control treatments (Fig. 1).

Drought Stress and Leaf Area Development in Pigeonpea

Table 1: Effect of water stress on the ieaf area index (LAI) of seven shorl-dunuion pigeonpea genotypes' at the endof stress 1, and stress 2

Genotype Growth habit- Control Stress Control Stress 2

ICPL 85043ICPL 85037ICPL 151ICPH9ICPL 85045ICPL S71CPH8SE±CV%

IIDDIDI

2.72.84.04.13.14.54.9

027

.41 (0.42)-.0

1.6L83.12.92.12.93.6

L3L92.42.9L92.53.2

0.29(0.29)33.4

0.60.91.51.40.90.91.9

'Genotypes are arranged in order of increasing lime to flowering"Growth habit: I - Indeterminate. D = Determinate'SE values in parentheses are for comparing means at the same level of treatment

£.50 r

m• > .

TJ 1 OCO

tn

-

A ...." A

cl—•-

""i-6

A

,-

0''

SI-O- -

A

C2A

A• ^ ^

s2

J 1

0 1 2 3 4 5

Leaf area index

Fig. 1: Effect of water stress on the relationship betweenseed yield and leaf area index (LAI) ofseven short-durationpigeonpea genotypes at the end of stress 1 (cl, si) and stress2 (c2. s2) for control (cl, c2) and stressed (si . s2) plots.Linear regression equations are:-

y = 0.79 + 0.31 xfor cl (/" = 0.3I): y = 0.33 + 0.45 x for si( r = 0.98);y = 0.83+ 0.38 xfor c2 ( r - 0.42): y = 0.68 + 0.29 x for s2( r = 0.63).

Leaf characteristics

The specific leaf area (SLA; cm- g"') in the stresstreatments was not significantly less than the controlat comparable times and therefore means of stressand control treatments are presented (Table 2).Specific leaf area was highest for genotype ICPL 151and lowest for ICPL 87 or ICPL 85037. Specificleaf area declined from stress 1 to stress 2 for allgenotypes, with ICPH 9 showing the greatest andICPL 151 the least decline.

Water stress reduced leaf number plant"' by 15-35 % under stress 1 and by 20-45 % under stress 2,with the earliest flowering affected most under stress1 and least under stress 2 (Table 3). Leaf size (cm-

Table 2: Specific leaf area (cnr g ') for seven short-duration pigeonpea genotypes' at the end of each droughtstress treatment-

Soil moisture treatmentGenotype Stress 1 Stress 2 Stress 3-'

ICPL 85043ICPL 85037ICPL 151ICPH 9ICPL 85045ICPL 87ICPH 8SE±

230.9227.0244.1235.8238.7221.3

242.78+ 6.13

175.4172.2210.4189.2189.3170.2193.0+ 6.60

141.3132.7174.8138.3158.4134.7154.6+ 3.47

' Genotypes are arranged in order of increasing time toflowering; their growing habits are as indicated in Table1"Data for control and stressed treatments were pooledfor each genotype, since treatment effects were non-sig-nilicanl^At the end of stress 3, pooled data for all soil moisturetreatments are given

leaf ') tended to decline under water stress for mostgenotypes. The reduction was significant only forICPL 87 at the end of stress K and for ICPH 9 andICPL 87 at the end of stress 2 (Table 4).

Carjopy light interception

During the development of stress 1 (at 71 and 86DAS), water stress significantly reduced canopylight interception (F) for all genotypes, with ICPL151 most affected (Table 5). Two weeks after stress 1was relieved (101 DAS), differences in the F betweencontrol and stressed treatments remained sicnificant

Lopez, Chauhan and Johansen

Table 3: Effect of water stress on leaf number plant ' ofseven short-duration pigeonpea genotypes' at the end ofstress 2

Genotype

ICPL S5()43ICPL 85037ICPL 151ICPH9ICPL 85045ICPL 87ICPH8SE±cv%

Control

64594143764381

5.618.6

Stress 1

46442730583468

(4.7)^

Control

39483031592779

4.625.1

Stress 2

26302417411548

(4.6)

'Genotypes are arranged in order of increasing timeto flowering; their growing habits are as indicated inTable I ^-SE values in parentheses are for comparing means atthe same level of treatment

Table 4: Effect oi' water stress on average leaf size (cm-leaf"') of seven short-duralion pigeonpea genotypes' atthe end of stress I and stress 2

Genotype

ICPL 85043ICPL 85037ICPL 151ICPH 9ICPL 85045ICPL 87ICPH 8SE±CV%

Control

14.715.431.131.015.736.220.0

1.38(12.3

Stress 1

10.713.527.129.812.429.418.1

1.34)-

1 Control

9.912.730.135.010.522.814.8

Stress 2

6.89.6

25.625.99.4

26.015.5

2.06(2.06)21.8

'Genotypes arc arranged in order of increasing timeto flowering; their growing habits are as indicated inTable I-SE values in parentheses are for comparing means atthe same level of treatment

only for genotypes ICPL 85043 and ICPL 151, andone week later only for ICPL 151. During the devel-opment of stress 2. water stress reduced the F for allgenotypes, with the exception oi' ICPL 85043 andICPL 85037 at 93 DAS. and ICPL S5O37 at 101DAS (Table 6). One week after the relief of stress 2(at 110 DAS), water stress induced differences inthe F persisted for all genotypes, with ICPL 85037remaining relatively unaffected. Stress 2 affected theF of ICPL 151 to the greatest extent compared toihe other genotypes, and ICPL 151 showed the leastrecovery one week after water stress was relieved.For most genotypes, the F continued to decrease in

the stress treatments after the relief of stress 2, withIhe decline being greatest for ICPL 151.

Plant mortality

With adequate soil tnoisture throughout growth,plant tnortality was lowest for the latest floweringgenotypes, ICPL 87 and ICPH 8, and was sig-nificantly higher for the earlier flowering inde-terminate genotypes (Table 7). The water stresstreatments did not increase plant tnortality. Plantmortality was actually reduced when ICPL 85043and ICPL 85045 were subjected to stress 1 and/orstress 2. For all genotypes at the time of harvest, alldead plants had fully mature dry pods.

DiscussionThe water stress treatments did not increase planttnortality in any genotypes. Pigeonpea leaves canwithstand considerable dehydration before deathoccurs (Flower and Ludlow. 1986. 1987), with plantmortality further reduced because of dehydrationavoidance mechanisms (Lopez. 1986). In genotypesthat exhibited annual-type behaviour (ICPL 85043and ICPL 85045), water stress treatments thatreduced yields also reduced plant mortality. Moteinfonnalion is required in order to fully understandthis response.

Tbe LAI declined during reproductive devel-opment and was reduced by stress 1 and stress 2 forall genotypes. Water stress induced reductions ingrowth and yield of several grain legumes are associ-ated with reductions in LAI (Pandey et al., 1984;Muchow, 1985a; Acosta Gallegos and Shibata,1989). Genotypic differences in drought resistancewere rcHected in the ability to tnaintain LAI par-ticularly under stress 1. The decline in LAI due tot eproductivc developtnent was greater than that duelo stress 2 for all genotypes, and drought resistancecan possibly be improved by reducing this growthstage effect, perhaps as exemplified by ICPH 9.

In pigeonpea, yield is related to the length of timespent at LAIs at which F is large (Hughes et al.,1991). The reduction in LAI of the control treatmentbetweeti 88 and 102 DAS was primarily due to leafabscission (Lopez et al., 1996b), and was as large asthe reduction due to water stress at the end of stress1. Abscising leaves might contribute to yield bymeeting the mineral N requiretnents ofthe develop-ing seeds through remobilizalion (Kumar Rao andDart, 1987). A lack of correlation betweeti leaf areaand yield in the control may be because the remain-ing leaf area is still above critical LAI for these

Drought Stress and Leaf Area Developmeni in Pigeonpea

Table 5: Effect of stress 1 on the fractional canopy light interception of seven short-duration pigeonpea genotypes'at 71. 88, 101 and 110 days after sowing (DAS)

Genotype71 DAS

Control Stress86 DAS

Control StressH)l DAS

Control Stress110 DAS

Control Stress

ICPL 85043ICPL 85037ICPL 151ICPH9ICPL 85045ICPL 87ICPH8SE±CV%

89609493869197

4.11.

9(4.5)=3

69846680747175

92909695959596

2.2(2.4.8

79761185878486

1)

89859691819488

49

.2(4.0)

.9

73837790778683

76118884718383

5.0(4.7)13.3

66776881697574

^ Genotypes are arranged in order of increasing time in flowering; their growth habits are as indicated in Table 1-SE values in parentheses are for comparing means at the same level of treatment

Table 6: Effect of stress 2 on percent light interception of seven short-duration pigeonpea genotypes' at 93. 101 and110 days after sownig (DAS)

Genotype93 DAS

Control Stress 2101 DAS

Control Stress 2110 DAS

Control Stress 2

ICPL 85043ICPL 85037ICPL 1511CPH9ICPL 85045ICPL 87ICPH8SE +CV%

91869594889694

83817480758279

898596918194

3.6(3.7r9.1

64776572647167

76778884718383

56644055526364

4.2(4.0)9.9

5.0(4.7)13.3

I Genotypes are arranged in order of increasing time to flowering: their growth habits are as indicated in Table- SE values in parentheses are for comparing means at the same level of treatment

Table 7: Effect of drought stress timing on plant mortality(%) of seven short-duration pigeonpea genotypes'

Genotype

ICPL 85043ICPL 85037ICPL 151ICPH 9ICPL 85045ICPL 87ICPH 8SE

Soil moisture treatmentControl

27(30)-9(17)6(10)4(9)

31(33)1(2)1{2)

Stress 1

23(29)9(17)7(13)6(11)

17(23)2(6)1(4)

(±

Stress 2

8(16)6(12)2(5)1(5)

11(18)2(8)2(6)

3.1)

Stress 3

23(28)7(13)2(9)1(4)

28(32)1(5)2(5)

' Genotypes are arranged in order of increasing timeto flowering; their growing habits are as indicated inTable 1^Angular transformed values are given in parentheses

pigeonpea genotypes. By contrast, in tbe stress treat-ments remaining leaf area index may have declinedbelow the critical LAI. The low incidenee of podabscission (Lopez et al., 1996b), and higb stabilityof seeds pod"' and 100-seed mass (Lopez et al.,1996a) suggest that sulficient leaf area is retained tocomplete the maturation of expanded pods underboth stressed and control conditions. The speeifieleaf area (SLA) declined from the end of stress 1 tothe time of final harvest, but was not significantlyaffeeted by tbe water stress treatments. A reductionin tbe SLA is generally observed for grain legumesunder water stress (Turk and Hall, 1980; Pandeyet al., 1984; Muchow, 1985a), possibly indicatingtbieker leaves wbich aids in leaf water conservationbecause of the lower surface/volume ratio. Geno-type ICPL 151 maintained the highest SLA duringreproductive development, while the SLA for ICPH

Lopez, Chauhan and Johansen

9 showed the greatest decline. Compared to othergrain legumes, the juvenile plant growth rate ofpigeonpea is relatively slow (Brakke and Gardner.1987). and a high SLA during early growth mayallow a more rapid canopy development, since moreleaf area is produced per unit investment in leaf drymass. As crop development proceeds, production ofleaves with increasingly lower SLA may allow amore favourable response to drought at later growthstages.

Leaf size was greater and the number of leavesplant"' smaller for determinate compared to inde-terminate genotypes, and bolh parameters tended todecline during reproductive development or underwater stress. Reduction in the average leaf size dur-ing development occurs because later producedleaves are smaller while the older leaves that absciseare larger. Since leaf abscission increases underwater stress (Lopez et al.. 1996a). a more uniformleaf size during crop development will minimizereductions in LAI due to smaller average leaf size.Leaf size was significantly reduced by both stress1 and stress 2 for the late flowering, determinategenotype. ICPL 87. but not for indeterminate geno-types of comparable (lowering times. For the tra-ditionally indeterminate faba bean, reduced leafexpansion is largely responsible for LAI reductionunder water stress (Karamanos. 1978;Farah, 1981).Although leaf loss is less sensitive to water deficitscompared to leaf area development for several grainlegumes (Muchow, 1985a). reduced F under severewater stress is largely due to accelerated leaf sen-escence (Muchow et al.. 1986). For the maintenanceof LAI under water stress, the comparative advan-tage of having a large number of small leaves or asmall number of large leaves is not indicated by thepresent data.

The canopy light interception (F) declined after101 DAS and was reduced by water stress for mostgenotypes. For ICPL 151, F was reduced to thegreatest extent and recovery following rewateringwas slowest in response to both stress 1 and stress2. compared to the other genotypes. Reduction in Fcan result from leaf and fiovver drop {Lopez et al. inprep, b) as well as from leaflet paraheliotropy whichincreases under water stress (Meyer and Walker,1981; Oosterhuiset al., 1985). During recovery fromwater stress the resumption of vegetative and/orreproductive growth and leaflet diaheliotropy pos-sibly delayed the age-related decline in F observedto a larger extent in control plants. The results indi-cate a more desirable response to water stress inICPH 9 compared to ICPL 151 among the deter-

minate, and in ICPL 85037 compared to ICPL85043 among the indeterminate genotypes. Theresponse of F to water stress represents the com-bined responses of plant mortality, leaf orientation,vegetative and reproductive growth and abscission.Therefore, F may be the ideal variable which inte-grates most of the important effects of water stresson plant factors influencing seed yield, and is apotential tool in field drought tolerance screening.However, there must be effective control of otherenvironmental factors, particularly pests anddiseases, which may also affect F. For short-dur-ation pigeonpea. plant mortality appears to be lesssensitive to water stress compared to leaf area at theend of a water stress period during late vegetativeand early reproductive growth.

Acknowledgements

F. B. Lopez was a recipient of an ICRISAT PostdoctoralResearch Fellowship and acknowledges the support andadvice of Dr D. L, Oswalt of the Human ResourcesDevelopment Program. We wish to thank V. F. Lopez.N. Venkalaratnam. and field stafl'of the Agronomy Div-ision for field and laboratory assistance.

ZusammenfassungEinfllisse des Einwirkungszeitpunktes von DiirrestreBauf die Blattfiachententwicklung und dieLichtinterzeption des Bestandes bei frlihreifenTaubenerbsen

Der Blattflachenindex (LAI), die Anteile der Lichtinter-zeption des Beslandes (F) und die Absterberate derPflanzen /ur Reife wurden fiir 9 fruhrcife TaubenerbseniCiijcnuisiiijcm (L.) Millsp.) -Genotypen in ihrer Reaktionauf Diirre wilhrend der spaten vegetativen und Bluhphase(StreB I), der Blute und der fruhen Hulsenfullphase(StreB 2) und der Hulsenfullphase (StreB 3) untersucht.LAI und F wurden reduziert; die Pflan-zensterbliehkeitsrate nahm aber unter Durrebedigungennicht zu. Unter StrcBbehandlung 2 war LAI am stiirkstenzusammen mit den Einlliisscn auf den Samenertrag redu-zierl. Am Ende der StreBbchandlung I war der Samen-ertrag strafl'korreliert mit der LAI der unterschiedlichenGenotypen unter StreBbcdingungen. nicht aber in derKoiUrolIe ohne StreBbedingungen. Die Reduktionen inLAI als Folge des reproduktiven Wachstums waren sogroB Oder grofier als diejenigen der Folge von Wasser-streBbedingungen. Indeterminicrte Genolypen hattenkleinere aber dafur mehr Blatter je Pllanze im Vergleich/Li den determinierten Genotypen. Die Bcdeutung diescrUnterschiede hinsichtlich der Dlirreresistenz war nichterkennbar. Die Produktion von Bliittcrn mil einer abneh-menden spezifischen Blattllache wiihrend des Pflanzen-wachstums kann vorteilhaft sein. insbesondere wenn dieWahrscheiiilichkeit besteht, daB Dtirre wahrend der

Drought Stress and Leaf Areii Development in Pigeonpea

reproduktiven Phase auftritt. Die Werle fur F wahrendund nach WasserstreBbedingungen geben einen Hinweisauf die genotypische Durreresistenz, wobei die Genoty-pen mit der am starksten ausgepragten DCirreempfind-lichkeit die starkste Reduktion von F unter WasserstreB-bedingungen und die geringste Rate der Erholung nachdererneuten Bewasserungzeigten. Fur frtihreifeTauben-erbsen, bei denen die Pflanzenabsterberate kein Faktorunter WasserstreBbedingungen ist, scheinen das Aufrech-terhalten der LAI und F auf eine genotypisch bedingteDurreresistenz hinzuweisen.

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