Compensatory Growth Responses During Reproductive Phase of Cowpea after Relief of Water Stress

Abstract

AbstractUnpredictable drought affects growth and yield of dryland cowpea (Vigna unguiculata [L.] Walp.) during rainy season. With the objective of identifying compensatory growth responses after relief of water stress, pot‐grown plants (cv. C‐752) were water‐stressed at flowering, and physiological responses, short term dry matter partitioning upon relief of water stress, and productivity at maturity were studied. Water stress decreased, to varying degrees, leaf water potential, stomatal conductance, photosynthesis rate and transpiration rate. Recovery in assimilation lagged behind that in water relations. Assimilate supply seemed to be limiting early pod growth upon relief of water stress due to low photosynthesis rate, reduced leaf area per pod, and increased partitioning to leaf expansion. However, later pod growth was not limited by assimilate supply and final dry matter per pod was similar in both non‐stressed and stress‐affected plant. Cowpea exhibited the following growth responses during pod‐fill stage upon relief of water stress: 1. increase in leaf area, 2. shift in dry matter partitioning in favour of leaf expansion, 3. extended green leaf duration, and 4. increase in pod number. These partially compensating physiological responses probably ensure reasonable productivity of dryland cowpea during rainy season.