Influence of Light and Temperature on Photosynthesis and Transpiration in Some C₃ and C₄ Vegetable Plants from Kenya

Abstract

Abstract Potted vegetable plants of Amaranthus lividus, Gynandropsis gynandra and Crotalaria brevidens were grown outside under normal tropical conditions and rate of photosynthesis and transpiration were determined simultaneously in attached leaves under a range of leaf temperatures and irradiances. Photosynthetic rates were consistently higher in G. gynandra than in A. lividus and C. brevidens . However, in C. brevidens and G. gynandra the leaf resistances were lower and transpiration rates were higher than those in A. lividus . The results on optimum temperature requirements for maximum rates of CO 2 fixation, coupled with data on CO 2 compensation points and leaf anatomy provided clear evidence that G. gynandra and A. lividus are C 4 species, while C. brevidens is a C 3 species. The differential effects of light intensity and temperature on stomata and mesophyll resistances in C 3 and C 4 species are discussed in relation to rates of photosynthesis and transpiration.