Both the biochemical and functional modifications of photosynthetic apparatus were observed during whole plant ontogeny. Net photosynthetic rate (Pn)» contents of photosystem (PS) 2 reaction centres, cytochromes 6559, and/ rates of electron- transport, cyclic and noncyclic photophosphorylation increased up till generative organs formation: a gradual decline followed as a result of senescence. The drop in activity of the electron-transport chain during senescence lead to the decline in content of PS2 reaction centres and Pn