Onset of ATP synthesis in spinach chloroplasts after single‐turnover flashes in relation to adenylate kinase activity

Flash‐induced ATP synthesis was investigated in chloroplasts isolated from spinach varieties with a pronounced difference in their adenylate kinase activity. In chloroplasts with high adenylate kinase activity the first 4 flashes induced ATP hydrolysis which persisted for an extended dark period at which the membrane remained energized. In chloroplasts showing low adenylate kinase activity, ATP hydrolysis could only be induced by a successive flash train of at least 60 flashes or by a 30–60 s period of continuous pre‐illumination. The activity of the adenylate kinase must be considered when the kinetics of initial ATP synthesis and of P515 in light flashes are studied.