Gas exchange, evapotranspiration efficiency, morphophysiology and productivity of cowpeas under water deficit

The cowpea [Vigna unguiculata (L.) Walp.], a legume which originated in Africa, is now grown in the Tropics and many subtropical regions. Cowpea is of significance for food and feed and its yield is frequently severely affected by drought, resulting in its low average yield. Hence the influence of water deficit on gas exchange, growth, development and yield of cowpea was studied here, with the aim of contributing to our understanding of the response of cowpeas to water deficit and to the provision of efficient and viable information for breeding of drought resistant genotypes. To achieve this aim, several traits were examined, which included

- gas exchange [stomatal conductance (gs), net photosynthetic rate PN), transpiration rate (E) and intrinsic transpiration efficiency TEi)], evapotranspiration efficiency (ETE), water

use (WU) and yield/yield components,

- relationship among these traits and variability among the various genotypes.

From the results it was expected that it would be possible to find efficient plant types and characteristics to predict ETE and yield which could eventually be used in cowpea drought resistance breeding programmes.