photoinhibition

thumb|right|280px|Photoinhibition of Photosystem II (PSII) leads to loss of PSII electron transfer activity. PSII is continuously repaired via degradation and synthesis of the D1 protein. [[Lincomycin can be used to block protein synthesis]]

Photoinhibition is light-induced reduction in the photosynthetic capacity of a plant, alga, or cyanobacterium. Photosystem II (PSII) is more sensitive to light than the rest of the photosynthetic machinery, and most researchers define the term as light-induced damage to PSII. In living organisms, photoinhibited PSII centres are continuously repaired via degradation and synthesis of the D1 protein of the photosynthetic reaction center of PSII. Photoinhibition is also used in a wider sense, as dynamic photoinhibition, to describe all reactions that decrease the efficiency of photosynthesis when plants are exposed to light.