Differential Changes in the Amount of Protein Complexes in the Chloroplast Membrane during Senescence of Oat and Bean Leaves.

Antibodies against the individual subunits of protein complexes in the chloroplast membranes were used to follow the amounts of these polypeptides during foliar senescence. No change was found in the amount of polypeptides of photosystem I reaction center and the chloroplast coupling factor during senescence of oat (Avena sativa L.) and bean (Phaseolus vulgaris L.) leaves. A significant decrease in the amount of the different components of the cytochrome b(6)-f complex was detected. This change may account for the decrease in the rate of electron transport, which might be the rate limiting step of photosynthesis in senescing leaves.