The light-induced changes in the kinetics of the oxidation of photosystem I reaction center P700 in leaves of C3 and C4 plants, depending on the time of leaf adaptation to dark before the illumination were studied. The EPR 1 signal from oxidized centers P+700 was used to monitor the kinetics of P700 redox transients. Similar dependences of the light-induced changes in the kinetics of P700 versus the adaptation time were observed in leaves of three kinds of plants: bean, orange and maize. These data suggest that the deactivation of the Calvin cycle enzymes, which occurs 1-3 min after ceasing the illumination, is the main factor that causes the retardation of the light-induced oxidation of P700.