Assessment of Morpho-Physiological and Biochemical Responses of Perennial Ryegrass to Gamma-Aminobutyric Acid (GABA) Application Under Salinity Stress Using Multivariate Analyses Techniques

Salinity stress is one of the most important global problems that afflicts and limits the growth and development of turfgrass in arid and semi-arid areas. Therefore, this experiment was conducted to evaluate the effects of the interaction between gamma-aminobutyric acid (GABA) and salinity (NaCl) on perennial ryegrass (Lolium perenne L.). Perennial ryegrass plants were treated with three concentrations of GABA (0, 50, and 100 mM) and NaCl (0, 50, and 100 mM) for two months. Multivariate analysis of variance revealed that GABA, salinity, and their interaction had significant effects on the majority of measured traits. In shoots and roots, the application of salinity increased the Na+/K+ ratio, as well as proline, total soluble carbohydrates and protein (TSP), malondialdehyde (MDA), and hydrogen peroxide (H2O2) content, but reduced relative water content, membrane stability index (MSI), total chlorophyll content, and shoot and root growth. When GABA was applied in saline conditions, Na+ did not accumulate, the Na+/K+ ratio decreased, and the amount of K+ content increased significantly in shoots and roots, thereby allowing plant growth to resume. Peroxidase (POD) and superoxide dismutase (SOD) activities increased significantly (51.83% and 322%, respectively), whereas H2O2 and MDA contents decreased significantly (34.4% and 67%, respectively). In addition, the construction of a biplot, heatmap, and correlation plot fortified the positive effects of GABA on perennial ryegrass growth in saline conditions. GABA may help to alleviate salinity damage through its involvement in osmotic adjustment (proline and TSP), reducing the Na+/K+ ratio and limiting oxidative damage in cells with a dramatic increase in POD and SOD activity. Therefore, the application of GABA is an alternative technique for improving turfgrass tolerance to salinity.