Photosynthesis, photosynthetic enzymes and leaf area development in relation to hybrid vigour in Sorghum vulgare L.

Heterotic hybrids of sorghum produced more dry matter than their respective parents. Therefore, an analysis of leaf are development, rate of photosynthesis and activities of RuBP carboxylase and PEP carboxylase was made to determine whether the superior dry matter production in the hybrids could be attributed to any of these characteristics. Heterosis in leaf area was maintained at all stages in plant growth. Heterosis in photosynthesis was observed only during grain development in certain hybrids. At all other stages, the photosynthesis rate in hybrids were either intermediate or similar to one of the parents. No heterotic effect was observed in enzyme activity at any stage of growth. It is suggested that a multiplicative interaction between the heterotic leaf area and photosynthesis rate could possibly explain heterosis in dry matter production in heterotic hybrids.