Yield, yield components and growth and distribution of roots of cowpea under water stress

Abstract

Two greenhouse experiments were carried out in order to study the effect of drought stress on yield, yield components and root distribution of cowpea (Vigna unguiculata (L) Walp). The following cultivars were used: cv. Pitiúba, prostrate/creeping type, and cvs. Setentão and Epace-10, intermediate spreading bush type. In experiment 1 the plants were harvested at 82 DAG and were subjected to three water regimes: a) control; b) stress in the vegetative stage; and c) stress in the reproductive stage. In experiment 2 the plants were harvested at 42 DAG and received two water regimes: a) control, and b) water stress. Water stress decreased leaf Ψ_w leaf area, tops and root dry matter, and root/shoot dry matter ratio. The cv. Pitiúba showed a more vigorous root system in wet regime, followed by Setentão and Epace-10. Under water stress all three cvs. had deeper roots, and the cv. Setentão showed the highest ability to develop deeper roots. Water stress when applied at the vegetative stage delayed date of flowering in all cultivars. The number of flowers, pods and weight of pods/plant were reduced by stress. Pod length and number of seeds/pod were reduced only when plants were stressed from 36 to 82 DAG. Seed yield was reduced by stress for all cvs. for both stages of growth. Pod/flower number ratio was not affected by water regime.