Phytohormones as Stress Mitigators in Plants

The sessile nature of plants makes them susceptible to a wide variety of abiotic and biotic stresses. Abiotic stress conditions incorporate factors like drought, heat, cold, salinity, whereas biotic stresses emerge mainly from microorganisms, insects and from nematodes. Well-developed mechanisms have been evolved by plants to perceive abiotic and biotic stresses that affect plants. Through flaws in the genetic control of cellular pathways, abiotic stresses have a detrimental effect on the morphology and physiology of plants. Tolerating stresses that arise from changes in metabolism is a sophisticated process that plants employ to mitigate the impact of stresses. They play an important role in both stimulating plant defense mechanisms against stresses and regulating plant metabolism, making phytohormones some of the most important growth regulators. Supplementing with exogenous phytohor-mones has been used to enhance growth and metabolism in stressful environments. Recent studies have demonstrated that phytohormones made by microorganisms associated with roots may prove to be significant metabolic engineering targets for promoting host tolerance to abiotic stresses. Numerous genetic and biochemical techniques have been used to identify the biosynthesis pathways for phytohormones, here, we present the state of our understanding on how phytohormones help plants exposed to diverse stressors increase their ability to withstand abiotic stress and their defence mechanisms. The aim of this paper is to examine recent developments in understanding the mechanisms by which phytohormones increase plant stress toler-ance, especially in crop plants. This chapter does this so by highlighting significant morpho-physiological characteristics of plants that can be used to determine the beneficial impacts of phytohormones on stress tolerance.