Molecular Mechanisms of Photoinhibition in Plants: A Review

Abstract

P hotoinhibition is the term used to describe the decrease in photosynthetic activity brought on by light. The thylakoid membrane-encased PSII complex catalyses, generating one O 2 molecule and four protons for every two H 2 O molecules oxidized. There are around 20 unique protein subunits, approximately 36 molecules of chlorophyll, and plastoquinone that is bounded to protein, and light-driven electron transfer make up PSII. The reaction center of PSII comprises of D1 and D2 proteins. These proteins contain redox cofactors that are used in electron transport chain. The charge separation that occurs between the pheophytin (Phe) electron acceptor molecule and the excited reaction centre chlorophyll assembly (P680) is the fundamental factor that drives the light-driven PSII electron shift. The fundamental separated charge Abstract | Through the process of electron transport along a series of redox processes, sunlight energy is transformed into chemical energy that is then stored during photosynthesis. Photoinhibition is a significant and extremely complex phenomenon, which is basically light-induced damage to the photosynthetic machinery that principally affects the Photosystem II complex and leads to less photosynthetic productivity. A light-independent photosynthetic activity restricts the consumption of electrons produced in the early photoreactions, which appears to be the principal cause of photoinhibition by visible light. There is a chance that excessive photosynthetic electron transport could lead to an overabundance of reactive oxygen species (ROS). Reactive oxygen species such as H 2 O 2 and O 2 , that develops in photosystem II as a result of exposure to intense light, start to damage electron transfer system components and protein structure. Plants have adapted several protective mechanisms like production of antioxidants, enzymes and carotenoids to face reactive oxygen species and avoid photoinhibition.

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