ABSTRACT
Melatonin was first identified as an animal hormone, but later on it was found to be a crucial component of plant improvement and defense-related studies. Recent years have seen renewed interest in studying the role of melatonin in stress management of plants. Melatonin acts as a hormone, and it is found in every part of plants like leaves, roots, shoots, fruits and seed. Being a potential phytohormone, melatonin participates in various physiological activities. Apart from this, melatonin has a direct response on gasotransmitters, which are the key factors of various biosynthetic pathways of plants. The last two decades have seen a growing trend towards the role of gaso-transmitters in regulating physiological processes and biological pathways. Recent studies focused on the inter-relationship between melatonin and the gaseous signaling molecules like hydrogen sulfide (H2S), methane (CH4), nitric oxide (NO) and carbon monoxide (CO) to understand their function in detail. Various studies have also assessed the efficacy of melatonin as a scavenger of reactive oxygen species (ROS) and reactive nitrogen species (RNS). Phyto-melatonin also plays a significant role in regulating plant growth and development. The major challenges faced by plants during their growth are both biotic and abiotic stresses. There are reports which show significant involvement of melatonin as a plant-defense regulator for both biotic and abiotic stresses. However, this chapter will enhance the understanding of phyto-melatonin and its role in plant growth, development and defense strategy.
