Role of polyamines in regulating physiological and molecular responses of plants under abiotic stress

Polyamines (PAs) play a significant role in responses to abiotic stresses. Several studies have been achieved to identify the protective role of the application of PAs exogenously under abiotic stresses. Studies observed that the ameliorating effect of PAs is not always obvious concerning the stress tolerance of plants. The PA's exogenous application regulates several aspects of growth, influences several physiologic processes, and induces changes at the molecular level. The key role of PAs-induced tolerance to drought is related to the regulation of transcription factors and expression of many drought-related genes. The effect of exogenous PA application depends on several factors, like the developmental stage and plant species, the level of drought stress, and the PA concentration, and its endogenous level in the studied plant. This chapter explores the differential role of PAs in mediating both the molecular and physiological mechanisms in plants under abiotic stress conditions.