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

摘要

Inorganic carbon transport during photosynthesis of cyanobacterium Anabaena variabilis grown under ordinary air was investigated by supplying14CO2or H14CO3−solution to three different strains. Both CO2and HCO3−were accumulated within the algal cells. In the cell suspension from which dissolved inorganic carbon had been depleted by pre-illumination, CO2was transported and accumulated faster than HCO3−. When the concentration of HCO3−injected into the cell suspension of A.variabilisM3 was 25 times as high as that of CO2 (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, when14CO2or H14CO3−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 forChl