Melatonin (N-acetyl-5-methoxytryptamine) is a widely studied biomolecule, and its function has been investigated in bacteria, mammals, birds, amphibians, reptiles, fish and plants. Melatonin research in plants the last five years has attained an exponential growth phase and the number of publications related to phytomelatonin has significantly increased in present times. All this research is directed towards establishing multifarious roles of melatonin in plants, including the promotion of seed germination and seedling growth, influencing plant development and senescence, alteration of flowering and fruiting time and grain yield, modulating circadian rhythms, improving resistance against biotic stress as well as tolerance to abiotic stress, reducing oxidative stress, and stimulating plant immune response. However, to date, an exhaustive book, solely and exclusively dedicated to melatonin research on various aspects of plant biology, has not been published by any renowned publisher or is available in the market. Keeping all these facts in mind, this book aims to compile the most recent developments in the arena of melatonin-mediated regulation of plant physiology under optimal and sub-optimal conditions. This book will initiate and introduce the readers to the state-of-the-art developments and trends in this field of study and will largely cater to the scientific need of scientists engaged in melatonin research across the globe. The book will be unique of its kind and will draw the attention of scientific and research communities engaged in the field of melatonin research. The key features of this book: Authors will address the topics which would provide advances in the understanding of diverse functions of melatonin in plants, encompassing almost all the aspects that have been investigated so far Integrate the overall mechanistic function of melatonin, genomics and proteomics tools, and genetic engineering to manipulate endogenous melatonin levels, thus giving a holistic view of plant-level studies under normal or challenging situations Largely help the readers to design future research programs in exploiting melatonin as a protective agent to develop climate-resilient and pathogen-resistant plants Benefit the crop protection program and ensure food security Chapters will be supplemented with ample illustrations and figures This book will be beneficial to research scholars and Ph.D. students involved in melatonin research and working on stress physiology, stress proteins, genomics, proteomics and genetic engineering in different universities and research institutes all over the world. The book can also be used as an advanced reference book for the coursework of research and master’s level students. It will be of use to people involved in improving plant growth and yield, as well as the performance of plant species in the face of climate change and pathogen infection, using melatonin as the prime protective agent and signaling molecule. Although the book will directly benefit the academic and scientific community, it will also indirectly draw the attention of industries or companies that manufacture or sell chemical products, since the book will highlight in detail the antioxidative potential of melatonin. This will create impetus at the industrial level for the isolation and synthesis of melatonin as a beneficial chemical agent. Applying melatonin as an ameliorating agent against different stresses at the field level will also increase the demand for this chemical among the farmers and will promote large-scale sales and utilization of melatonin for ensuring crop protection and increasing yield.