Salt-Induced Metabolic Changes in Dunaliella salina

Abstract

An increase of medium NaCl concentration induces Dunaliella cells to evolve O2 photosynthetically even in the absence of CO2. This NaCl-induced O2 evolution may reflect the induced conversion of reserve carbohydrate to glycerol. The quantum yield for the NaCl-induced O2 evolution, in the absence of CO2, is 1.5-fold higher than that obtained for CO2 fixation. Since the synthesis of glycerol from reserve carbohydrate in the absence of CO2 requires only 0.5 ATP/NADPH, whereas photosynthesis requires at least 1.3 ATP/NADPH, it is concluded that the ATP/2e- ratio coupled to NADP reduction in Dunaliella is lower than required for CO2 fixation.