| Abstract: | Abstract —The transient oxidation and subsequent reduction of P700+ in spinach chloroplasts has been monitored by flash photolysis-electron spin resonance spectroscopy in the presence of various donors and acceptors. In general, the results obtained correlate well with results on Photosystem I subchloroplast particles, with two major differences. For Type A and B intact chloroplasts in the presence of 3-(3, 4-dichlorophenyl)-1, 1-dimethylurea (DCMU), the electron acceptor methyl viologen has no effect on the decay kinetics. This phenomenon is interpreted in terms of a functioning cyclic electron flow path around Photosystem I. Also, the photoresponse of Signal I depends on the length of the photolyzing flash. This is interpreted in terms of the existence of a primary electron donor to P700+ with a transfer time of ? 10 μs. |
