Eco-Physiological and Morphological Adaptive Mechanisms Induced by Melatonin and Hydrogen Sulphide Under Abiotic Stresses in Plants

Under the present era of changing climate, non-biotic pressures such as low or high temperature stress, constant heat waves, ultra-violet (UV) radiations, oxidizing agents, heavy metal and metalloids and salinity are continuously increasing and pose significant retardations in plants’ physiological processes to a great extent. Plants are equipped with adaptive mechanisms which enable them to withstand these induced effects. However, in today’s era, when the global temperature is increasing at an alarming rate, these mechanisms are not sufficient to protect plants from stress-induced growth and photosynthetic inhibitions. The application of plant growth regulators (PGRs) has gained an interesting insight in this regard. The melatonin (Mel) and hydrogen sulphide (H2S) are emerging plant elicitors which impart abiotic stress tolerance in diverse crop plants. The ameliorative role of these PGRs under various abiotic pressures in controlling diverse adaptive mechanisms in diverse crop plants is a topic that is still in infancy stage. Therefore, in the present chapter, the role played by Mel and H2S in regulating complex physiological and morphological adaptive mechanisms under myriads of abiotic pressures is apprehensively discussed.