Chapter 8 - Nitric oxide: a key player in reinforcement of photosynthetic efficiency under abiotic stress

Abstract

Nitric oxide (NO), a potent plant stress regulator, was previously considered to be a mere air pollutant. It is a free radical present in living organisms and mirrored its roles as a phytohormone due to its unparalleled array of mechanisms in alleviating various stress toxicities. Nitric oxide is majorly known for providing stress resistance in plants under salinity, drought, extreme temperature fringes, and heavy metal stress. Subjected to its concentration and its site of location in plant cells or tissues, NO might function as an antioxidant and reactive oxygen species scavenging molecule. The objective of this chapter is to describe the protective roles of NO in revitalizing the process of photosynthesis under abiotic stress. Photosynthesis is a vital process and is vulnerable to many stresses. Reduction in the rate of chlorophyll synthesis, increased photochemical quenching coefficients, reduced quantum efficiency of photosystem II, and disorganization in the stacking of grana in thylakoids under the influence of abiotic stresses are common damages in photosynthesis. Supplementation of NO has shown its astounding behavior in prominently influencing photosynthetic and stomatal regulation of plants exclusively on its amalgamation with a broad range of molecules, its mode of action mainly occurs through post-translational modifications (nitration and S-nitrosylation). NO has conquered a new place in plant science directed to stress physiology owing to its direct or subsidiary involvement in biotic and abiotic stresses.