Gamma-aminobutyric acid (GABA) is a four-carbon non-protein amino acid produced by plants that play an important role in metabolic homeostasis and energy balance. In this study, we evaluated the effects of exogenous application of GABA on antioxidant enzymes, photosynthetic pigments, total protein content, and growth of maize and soybean in four different regions of Brazil under field conditions. GABA was applied with fertilizers during basal fertilization (BF treatment), during supplementary fertilization (SF treatment), and during both fertilizations (BF+SF treatment). We observed that GABA treatments promoted a higher plant investment in leaf chlorophyll and protein content in some experiments, whilst a smaller activity in antioxidant enzymes such as ascorbate peroxidase, superoxide dismutase and catalase was observed, especially in soybean plants. Biochemical parameters of maize plants were less sensitive to GABA, but increases in chlorophyll content were also observed in this species. We observed that productivity increased in some regions, but not in others, whilst no clear pattern of response was observed regarding the application time of GABA during fertilizations. We concluded that the additional GABA supply can be used as a potential biofertilizer depending on species and region, resulting in higher productivity.

Keywords: carotenoid, chlorophyll, enzymes, growth, maize, soybean.