[Correlation between non-cyclic and pseudocyclic electron transport in pea chloroplasts: dependent on the concentration of ferredoxin].

The effects of ferredoxin concentrations on the correlation between pseudocyclic and non-cyclic electron transport in isolated pea chloroplasts with NADP+ as an electron acceptor was studied. The correlation of psuedocyclic and non-cyclic electron transport upon photoreduction of NADP+ in vitro can be regulated by ferredoxin concentration. At ferredoxin concentrations studied an addition of NADP+ to the system which makes possible electron transfer from ferredoxin to ferredoxin-NADP+-reductase increases the rate of overall electron transport across the chain. Unlike the pseudocyclic electron transport, photoreduction of NADP+ reaches its maximal saturation at relatively low (10-15 microM) concentrations of ferredoxin (Km = approximately 2-5 microM).