Selective Thylakoid Protein Damage and Repair during Photoinhibition

When photosynthetic organisms are exposed to photon flux densities which are considerably higher than those at which the organism developed, the excessive light load results in damage to the photosynthetic membrane, and hence in a reduction in the carbon assimilation rate (reviewed by Bjorkman, 1981; Osmond, 1981). This phenomenon has been referred to as photoinhibition (Kok, 1956). The biochemical mechanism of light-induced damage is unknown. This manuscript presents evidence indicating that the primary lesion affects the secondary plastoquinone electron acceptor for photosystem II (PS II) — a protein-bound quinone designated as “B”.