Abstract
Cowpea (Vigna unguiculata (L.)Walp.) is one of the most important legume in semi-arid region. In this study, we aimed to investigate the physiological response in three cowpea lines producing with low yield caused by drought stress at flowering stage. Prolonged drought stress decreased seed yield and pod number in the three lines tested. A drought susceptible line, IT95K-238-3, showed a sharp decline in the number of pods as well as in the number of flowers under drought stress. The number of flower bud formation decreased and that of flower bud abscission increased during drought stress. These effects were severe in the drought susceptible line. Leaf stomatal conductance and relative water content of peduncle apex markedly decreased in the most susceptible line exposed to drought stress. Based on these results, it was suggested that both stomatal closure in leaves and the decline of water content in peduncle apex induced by drought stress restricted flower bud formation and enhanced flower bud abscission. As a result, these factors caused a reduction of the number of flowers and seed yield.
