Na + -Stimulation of Photosynthesis in the Cyanobacterium Synechococcus UTEX 625 Grown on High Levels of Inorganic Carbon

Abstract

Photosynthesis of washed cells of Synechococcus UTEX 625 grown on 5% CO(2) was markedly stimulated (647 +/- 50%) at pH 8.0 by the addition of low concentrations of NaCl (concentration required for half-maximal response, K((1/2),) = 18 micromolar). Studies with KCl and Na(2)SO(4) showed that the stimulation was due to Na(+). Photosynthesis at pH 6.1 was only slightly stimulated by Na(+). The response of photosynthesis at pH 8.0 to [Na(+)] was strongly sigmoidal for dissolved inorganic carbon ([DIC]