Photoinhibition: Impairment of the primary charge separation between P-680 and pheophytin in photosystem II of chloroplasts

Abstract

The question of the primary site of photoinhibition was investigated using the light-induced absorbance change of pheophytin a (at 685 nm) in spinach chloroplasts and Chlamydomonas reinhardtii cells. Photoinhibition of spinach thylakoid membranes resulted in a parallel decrease in the amplitude of the pheophytin a (Δ A 685) and Q A (Δ A 320) photoreduction signals. In intact Chlamydomonas reinhardtii cells the pheophytin photoreduction and oxygen evolution activity exhibited a similar decrease during photoinhibition. A complete recovery of both activities was attained within 60 min incubation in normal growth conditions. It is concluded that the primary site of photoinhibition involves the components (P-680 and/or pheophytin) of the primary charge separation.