Effects of Timing of Drought Stress on Abscission and Dry Matter Partitioning of Short‐duration Pigeonpea

Abstract

Shoot dry mass partitioning and cumulative abscission of leaf, flowers and pods were determined for nine short‐duration pigeonpea genotypes grown with adequate soil moisture throughout growth (control), or subjected to water stress during the late vegetative and flowering (stress 1), flowering and early pod development (stress 2), or pod fill (stress 3) growth stages. The total cumulative dry mass of abscised plant parts was lower for determinate genotypes, but it increased to a greater extent under water stress than that for indeterminate genotypes, with stress 2 having the greatest and stress 3 die least effects. The dry mass contribution of pods to total abscission was ≤ 5%, and not signiflcantiy affected by water stress, while the contribution of leaves increased and mat of flowers decreased. Stress 3 had no significant effects on abscission dry mass totals or components. Reduction in shoot dry mass under water stress was most pronounced for genotypes in die early pod development stage, and the dry mass contribution of leaves generally decreased and that of pods increased under stress 1 and stress 2. With similar abscission levels, the shoot dry mass of genotype ICPL 151, was similar to, or greater than, that of hybrid ICPH 9, under stress 1 and stress 2, and the contribution of pods to shoot dry mass was lower for hybrid ICPH 9 under both stress treatments. Genotypic differences in drought resistance were likely due to differences in the leaf area maintenance during, and in the recovery of dry mass and pod production following, water stress periods.

Effects of Timing of Drought Stress on Leaf Area Development and Canopy Light Interception of Short‐duration Pigeonpea

“…The reduction in LAI of the control treatment betweeti 88 and 102 DAS was primarily due to leaf abscission (Lopez et al, 1996b), and was as large as the reduction due to water stress at the end of stress 1. Abscising leaves might contribute to yield by meeting the mineral N requiretnents ofthe developing seeds through remobilizalion (Kumar Rao and Dart, 1987).…”

“…By contrast, in tbe stress treatments remaining leaf area index may have declined below the critical LAI. The low incidenee of pod abscission (Lopez et al, 1996b), and higb stability of seeds pod"' and 100-seed mass (Lopez et al, 1996a) suggest that sulficient leaf area is retained to complete the maturation of expanded pods under both stressed and control conditions. The speeifie leaf area (SLA) declined from the end of stress 1 to the time of final harvest, but was not significantly affeeted by tbe water stress treatments.…”

“…Seed yield is most alTecled by drought occurring in the late flowering and early pod development stages. Genotypic differences in drought resistance are associated with the maintenance of dry mass partitioning into leaves during, and dry mass production followingdrought periods (Lopez et al, 1996b). Dry matter production depends on canopy light interception and the efficiency of its con\ersion into dr\ matter.…”

Physiological Responses of Grain Legumes to Stress Environments

“…Two related mechanisms contributing to strong tolerance of tissue water deficit are high levels of osmotic adjustment and a low critical or lethal relative water content (RWC) of leaves (Flower and Ludlow, 1986;Sinclair and Ludlow, 1986). Lopez et al (1996) reported that genotypic differences in drought resistance were probably due to differences in leaf area maintenance during and in the recovery of dry weight and pod production following water stress periods.…”

Influence of Water Deficit on Uptake and Distribution of Nitrogen in Soybeans Monitored by Soil Injected 15N

“…2000, Deblonde and Ledent 2001, De Costa and Shanmugathasan 2002). Increased soil water deficit (wd) is correlated with reduced dry matter (DM) development (Lopez et al. 1996a,b, Lazcano‐Ferrat and Lovatt 1999, Grieu et al.…”