A Causal-Comparative Study of Physiological and Biochemical Parameters of Wheat (Triticum aestivum L.) under Salinity Stress with Reference to Gamma-Aminobutyric Acid

Abstract

Salinity stress is a major abiotic constraint limiting wheat productivity through osmotic imbalance, ionic toxicity, and oxidative damage. This causal-comparative study examined the physiological, biochemical, and growth-related responses of wheat (Triticum aestivum L.) grown under saline and non-saline conditions with reference to graded gamma-aminobutyric acid (GABA) exposure. Using an ex post facto design, naturally differentiated wheat plants of two cultivars (Lasani and Galaxy-13) were compared across salinity conditions (0 and 150 mM NaCl equivalent) and four GABA exposure levels (0, 100, 200, and 400 mg L⁻¹). Growth attributes, water relations, membrane stability, photosynthetic pigments, oxidative stress markers, antioxidant enzyme activities, and metabolic constituents were assessed. Salinity was consistently associated with reduced growth, lower relative water content, increased electrolyte leakage, elevated malondialdehyde levels, and altered antioxidant activity, confirming its strong association with physiological deterioration and oxidative stress. Reference to GABA exposure revealed a clear mitigative pattern, where higher GABA levels were associated with improved water status, enhanced membrane stability, reduced lipid peroxidation, and strengthened antioxidant responses under saline conditions. Significant interaction effects between salinity and GABA supported systematic variation in stress intensity relative to biochemical context. Varietal differences further indicated genotype-specific adaptive responses. Although causal inference is limited by the non-experimental design, the convergence of physiological, biochemical, and statistical evidence supports GABA as a key stress-modulating biochemical factor in wheat under salinity. These findings provide a comparative framework for future experimental validation and stress-management strategies in saline agriculture.