ABSTRACT
Melatonin (N-acetyl-5-methoxytryptamine) is a well-known auxin analog derived from tryptophan, with a wide array of biological functions in terms of improving plant growth along with plant adaptation under different environmental stresses. Application of melatonin can promote seed germination and overall crop growth and accelerates mycorrhizal development, thereby increasing net photosynthesis and water use efficiency. A biostimulant like melatonin has a multifunctional role related to minimization of oxidative stresses from drought, temperature extremities, salinity and heavy metal stress by developing internal antioxidant defense strategy. Both seed priming as well as exogenous foliar spray with melatonin have been documented to mitigate the adversities of abiotic stresses by reducing electrolyte leakage and chlorophyll degradation along with reactive oxygen species (ROS) concentrations in terms of superoxide anion (O2o?), hydrogen peroxide (H2O2) and malondialdehyde (MDA). Additionally, melatonin stimulates antioxidant response of crop plants, increasing ROS scavenging by escalating the accumulation levels of osmoprotectants like proline and antioxidant enzymes including catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX) and superoxide dismutase (SOD) under abiotic stresses. This chapter is a comprehensive insight of melatonin application through priming and foliar techniques, exploring its indispensable functional aspects in boosting crop production through activation of its antioxidative defense mechanism against unfavourable environmental conditions.
