Melatonin: A Critical Regulator of Plant Growth and Development

Plant growth regulators (PGRs) utilization in the field of agriculture has been widely studied for improving crop quality and yield. Among these PGRs, melatonin (N-acetyl-5-methoxy-tryptamine) is an indole moiety, which is mostly present in animals and plants. In animals, the modulation of circadian rhythms and in plants senescence regulation indicate melatonin advantages. It is considered as a versatile moiety because it exerts a positive influence in improving crop quality by improving the morphological parameters, photosynthetic activity, plant metabolism, osmolytes, and the plant’s defense system. It can regulate both reactive oxygen and nitrogen species hence regarded as an antioxidant agent. The expression of several stress-specific genes and antioxidant enzyme genes was also upregulated by its application to endure stress resistance in plant genotypes. Melatonin also shows beneficial effects in association with other phytohormones and regulates the gene expression associated with plant hormone metabolism. This book chapter gives an overview of the biosynthesis of melatonin and its role in regulating various aspects of plant growth and development. It also emphasizes the influence of melatonin in the mitigation of various abiotic stresses and its crosstalk with other plant growth regulators in mediating plant growth and development.