Photosynthetic Electron Transport under Phosphorylating Conditions as Influenced by Different Concentrations of Various Salts

Osman, M. E-A. H. and El-Shentenawy, F. 1988. Photosynthetic electron transport under phosphorylating conditions as influenced by different concentrations of various salts.—J. exp. Bot. 39: 859–863. The rate of light-induced electron transport by isolated spinach thylakoids under phosphorylating conditions, as affected by different concentrations of Br−, Cl−, NO3−, HCO3−, SO42− and CO32− has been investigated. The results show that both low and high concentrations of HCO32− stimulated the oxygen evolution capacity under phosphorylating conditions, whereas only low concentrations of CO32−, SO42− and Cl− stimulated the oxygen evolution capacity. However, irrespective of concentration, both Br− and NO3− reduced this capacity. The rate of photosynthetic electron transport was generally stimulated by addition of ADP, even in cases where electron transport was inhibited by addition of bromide and nitrate. The different concentrations of these anions also caused reduction of the power generated by proton pumping and used for phosphorylation. The greatest level of reduction was observed in the presence of high concentrations of Cl− and HCO3−.