Photosynthetic activity of ripening tomato fruit

Gas exchanges, chlorophyll (Chl) a fluorescence and carboxylation activitie s of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) and phosphoen olpyruvate carboxylase (PEPC) were determined in tomato (Lycopersicon escul entum Mill.) fruits picked at different developmental stages (immature, red -turning, mature, and over-ripe). The fruits did not show signs Of CO2 fixa tion. However, photochemical activity was detectable and an effective elect ron transport was observed, the values of Chl fluorescence parameters in gr een fruits being similar to those determined in the leaves. The RuBPCO acti vity, which was similar to those recorded in the leaves at the immature sta ge of the fruit, decreased as the fruit ripened. PEPC activity was always h igher than RuBPCO activity.