Drought Tolerance of Cowpea

1. Studies on water absorption ability of cowpea (Vigna unguiculata (L.) WALP. var. unguiculata)

Abstract

The water absorption ability of cowpea (Vigna unguiculata (L.) WALP. var. unguiculata) was examined by comparing the values of the respiration rate in roots and the dry weight of roots per leaf area with the corresponding values in other leguminous crops. None of these values were higher in cowpea than in other legume species. This suggests that the osmotic and passive water absorption abilities of cowpea are lower than those of the other crops. However, it was found that cowpea had deeper root system than other legumes, and the root further developed vertically when the plants were exposed gradually to water stress. It was suggested by the subsurface irrigation treatment that such deep roots play an important role in the vegetative and reproductive growth in cowpea. The taproots that penetrate into deep soil layers appear to absorb and transport water to the upper parts of plant under drought conditions.