Transport and Fixation of Inorganic Carbon during Photosynthesis of Anabaena Grown under Ordinary Air. I. Active Species of Inorganic Carbon Utilized for Photosynthesis

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Inorganic carbon transport during photosynthesis of cyanobacterium Anabaena variabilis grown under ordinary air was investigated by supplying ^<14>CO_2 or H^<14>CO^-_3 solution to three different strains. Both CO_2 and HCO^-_3 were accumulated within the algal cells. In the cell suspension from which dissolved inorganic carbon had been depleted by pre-illumination, CO_2 was transported and accumulated faster than HCO^-_3. When the concentration of HCO^-_3 injected into the cell suspension of A. variabilis M3 was 25 times as high as that of CO_2 (the expected ratio at equilibrium at pH 7.8), the initial rates of fixation of both inorganic carbon species were practically the same. On the other hand, when ^<14>CO_2 or H^<14>CO^-_3 was added under steady state photosynthetic conditions, both carbon species were transported at similar rates. The ratio of fixed to transported carbon measured after the initial 5 s was only 23-27% regardless of the carbon species supplied. This percentage is much lower than that reported for Chlorella cells.
日本植物生理学会の論文