Deciphering the physiological and molecular functions of phytohormones

Plants rely on a diverse set of small molecules called phytohormones for growth, development, and adaptability. Since the discovery of auxin, hormones have been at the frontier of plant biology. Classically, hormone functions and responses were studied using synthetic hormones and analogs. However, the advent of technology, multidisciplinary approaches, and the genome sequencing of the model system of Arabidopsis and rice has dramatically increased our understanding of physiological and molecular mechanisms driving plant hormone actions. In this chapter, we talk about how independent or combined molecular action of phytohormones such as with their signaling components and regulators leads to changes in plant physiology to regulate multiple aspects of plant development, defense, and adaptation. We envisage that such detailed knowledge will allow a far greater understanding of the complex dynamics underlying plant hormone action.