Inhibition of photosynthesis by ̄owering in mango (mangifera indica L.). A study by gas exchange methods

A regular (cv. Thothapuri) and an irregular (cv. Langra) bearing cultivar of mango were selected to study the gas exchange parameters such as photosynthesis, stomatal conductance and internal carbon dioxide concentrations in ̄owering and non̄owering branches. Photosynthetic rates at different carbon dioxide concentrations were also recorded in both the branches to calculate the carboxylation ef®ciency by generating CO2 response curves. Photosynthetic rate and stomatal conductance were higher in non̄owering branches as compared to the ̄owering ones, in both cultivars. The reduction in photosynthetic rate was not due to variation in the water status of the leaves, since relative water content (RWC) of the leaves in both types of branches was not signi®cantly different. Hence, the reduction in photosynthetic rate could be mainly due to the reduction in carboxylation ef®ciency. Such a reduction in carboxylation ef®ciency could be due to the presence of inhibitors in the leaves of ̄owering branches. # 2000 Elsevier Science B.V. All