Plant Performance and Defensive Role of β-Amino Butyric Acid Under Environmental Stress

γ-Aminobutyric acid (GABA), a four-carbon nonprotein amino acid, is abundant in both eukaryotic and prokaryotic organisms. In very recent years, the flexible roles of GABA have emerged in order to mitigate abiotic stress conditions (hypoxia, heat, chilling stress, and salinity) by mediating the physiological, biochemical, and molecular pathways. It indirectly affects plant growth phases and increases the concentration of stress tolerance-related accumulates in response to stresses. The exogenous applications of GABA are used to improve plant stress responses in terms of elevating the efficiency of photosynthetic system’s and regulation of stress-related genes encoding for osmotin, dehydrins, heat-shock protein, and leaf embryogenesis protein associated with conditions. In a response, it triggers a similar effect of intrinsic signaling molecules and initiates transcriptional factors that offer the chances to mediate the overall vigor of plants. Various recent studies have gained much attention on the effective involvement of GABA treatment on stomatal conductance, photosynthetic rate, osmolyte metabolism, antioxidant enzymes, and protection of chloroplastic structure during the prolonged period of drought and heat stress. Therefore, this current chapter aims to summarize the information on the multifunctional contribution of GABA and share its metabolic and biological function in variable conditions. Moreover, the information on flexibility in stress adaptation and its role in maintaining stress-associated biological pathways are also explained.