ABSTRACT
Being sessile organisms, plants have to encounter harsh environmental conditions which significantly affect their growth and development. To overcome such harmful effects, plants synthesize various protective metabolites. Melatonin, being one such protective metabolite, was discovered in plants in the late ‘90s, but its role, signaling and crosstalk with other phytohormones remains unclear till date. N-acetyl-5-methoxytryptamine, or most commonly melatonin, is an indole compound and is synthesized from tryptophan. Research on melatonin has been significantly increased in the recent decade, and its role as a universal stress hormone in plants is quite evident from these studies. Melatonin is a multifunctional metabolite in plants that controls the redox status of the cells and also controls various metabolic pathways by interacting with other phytohormones. In addition, melatonin also helps in regulating the survival capability of the plants by scavenging the reactive oxygen species and enhancing the activity of enzymatic and non-enzymatic antioxidants. In this chapter, we tried to emphasize the role of melatonin in maintaining the growth and development of the plants under various abiotic stresses (drought, salinity, heavy metal toxicity and extreme temperature). Moreover, we also tried to decipher the crosstalk that occurs between melatonin and other phytohormones, that is, auxin, jasmonic acid, gibberellic acid, abscisic acid, cytokinin, ethylene and salicylic acid in stressed plants. All these aspects of melatonin suggest that melatonin is a key player in crop improvement and abiotic stress regulation.
