Gamma-Aminobutyric Acid Application Methods for Sustainable Improvement of Plant Performance Under Abiotic Stress: A Review

Drought, high temperature, salinity, waterlogging, and nutrient deficiency, along with metal toxicity, are among the environmental factors that have resulted in much alteration of many ecosystems by climate change. Such stresses have dramatically lowered the global average human harvest of core crops, which, in turn, has driven an overall decrease in worldwide agricultural productivity. Plants have developed a variety of defense strategies against biotic and abiotic stress. Evidence of the successful roles of phytohormone-like neurotransmitters in ameliorating the response to stress has already been established. One neurotransmitter accumulated by the plants is gamma-aminobutyric acid (GABA), a non-protein amino acid that is essential for signaling in plant growth regulation and development via the control of physiological and biochemical processes. Plant tissues demonstrate rapid accumulation of GABA when exposed to various abiotic stresses. Consequently, it is imperative to understand how this accumulation affects the resistance and productivity of crops in challenging environmental conditions. Previously, different application methods and doses of GABA on different plant species were used under various abiotic stress conditions. The research findings exhibited that the method and concentration of GABA depend on the type of crop. Furthermore, the GABA dose depends on the methods of GABA application. The present review summarizes the potential doses and methods of applications of GABA under different abiotic stress conditions to ameliorate deficiencies in plant growth, yield, and stress tolerance through the avoidance of oxidative damage and maintenance of cell organelle structures. This review will also describe the complex mechanism by which GABA contributes to the attenuation of the effects of abiotic stresses by regulating some important physiological, molecular, and biochemical processes in crops.