Transport and Fixation of Inorganic Carbon during Photosynthesis in the Cells of Anabaena Grown under Ordinary Air. II. Effect of Sodium Concentration during Growth on the Induction of of Active Trasport System for IC

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The requirement of sodium for growth of Anabaena variabilis M3 was investigated under low (0.04%) and high (1.5 or 5%) CO_2 conditions. The growth rates under both conditions were strongly affected by NaCl concentrations up to 0.5 mM in the medium. In the presence of 40 μM NaCl, the cells were not able to grow under a low CO_2 condition, but were able to grow under a high CO_2 condition. The sodium requirement for growth was dependent on pH: in the Na^+-deficient condition, cells could grow at pH 6.8, while no growth occurred at pH 8.2, suggesting that the requirement of Na^+ for growth observed in the low CO_2 condition can be substituted for by a lower pH. In the presence of 20 mM NaCl at pH 7.8, ^<14>CO_2 as well as H^<14>CO^-_3 were actively transported into the cells which had been grown in air. In contrast, the transport of both of these inorganic carbon (IC) species was suppressed under the Na^+-deficient condition. These results suggest that sodium is required for the stimulation of transport of IC during photosynthesis. This is one of the reasons why Na^+ is required for the growth of Anabaena under ordinary air and alkaline conditions.
日本植物生理学会の論文