EFFECTS OF TIMING OF DROUGHT STRESS ON ABSCISSION AND DRY-MATTER PARTITIONING OF SHORT-DURATION PIGEONPEA

Shoot dry mass partitioning cumulative abscission of leaf, flowers and pods were determined for time short-duration pigeonpea genotypes grow n with adequate soil moisture throughout growth (control), or subjecte d 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 ex tent under stress than that of indeterminate genotypes, with stress 2 having the greatest and stress 3 the least effects. The dry mass contr ibution of pods to total abscision was <5%, and not significantly affe cted by water stress, while the contribution of leaves increased and t hat of flowers decreased. Stress 3 had no significant effects on absci ssion dry mass totals or components. Reduction in shoot dry mass under water was most pronounced for genotypes in the early pod development stage, and the dry mass contribution levels, the shoot dry mass of gen otype ICPL 151, was similar to, or greater than, that of hybrid ICPH9, under stress 1 and stress 2, and the contribution of pods to shoot dr y mass was lower for hybrid ICPH9 under both stress treatment. Genotyp e 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.