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

Abstract

The requirement of sodium for growth of Anabaena variabilis M3 was investigated under low (0.04%) and high (1.5 or 5%) CO2 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 CO2 condition, but were able to grow under a high CO2 condition. The sodium requirement for growth was dependent on pH: in the Na+-deficient condition, cells could grow at pH6.8, while no growth occurred at pH 8.2, suggesting that the requirement of Na+ for growth observed in the low CO2 condition can be substituted for by a lower pH. In the presence of 20 mm NaCl at pH 7.8, 14CO2 as well as H14CO3− 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.