On the equilibrium between the reaction centers of the two photosystems in photosynthesis. The effect of independent electron-transport chains.

The equilibrium observed by Joliot et al. (2) between the reaction centers of photosystems I and II of photosynthesis, is explained by a kinetic model. The essential idea is that the electron transport chains are independent entities, and therefore the possibility arises that the reaction centers may exist in oxidized and reduced forms, respectively, and not react with one another because they belong to different chains. According to this idea the observed equilibrium is not a real one but a result of the kinetic effect. Facts which do not fit nicely with the equilibrium model (photophosphorylation between the two photosystems, observed oxidation potentials of the reaction centers) remain consistent with the present kinetic model.