Source-sink relationships in cowpea under drought stress.

Abstract

In order to analyse the source-sink relationship in cowpea [Vigna unguiculata (L.) Walp.], cvs. Epace 10 and Seridó, an experiment was developed under cycles of drought stress applied in vegetative and reproductive stages. The leaf water potential, stomatal conductance and transpiration suffered reductions at 29 and 52 days after planting when water stress was applied in vegetative and reproductive stages, respectively. The plants showed high capacity of recovering after the end water stress applied in the vegetative period. The water restrictions applied did not influence the source capacity (leaf number, leaf area and specific leaf area) and the reproductive efficiency, but reduced the sink size (number of pods, and number and weight of seeds per plant). The stress inhibited the leaf abscission process and the plant sink potential (flowers per plant) when applied during the vegetative phase. The Epace 10 showed higher potential and capacity of reproductive sinks. Stress in reproductive phase induced large reduction in seed production/leaf area rate on both cultivars.