Role of Gallic Acid Pre-treatment in Inducing the Antioxidant Response of Two Wheat Cultivars Differing in Drought Tolerance

The aim of present study was to identify the optimum concentration of GA in promoting the antioxidant response so that it can be used to lessen the deleterious effects of drought in two differentially drought responsive wheat cultivars, PBW 175 (tolerant) and PBW 621 (sensitive). In comparison to hydroprimed seedlings, 20–140 ppm of GA stimulated seedling growth and unlike other phenolic acids, even at 1000 ppm, it did not show much inhibitory effects. At 6th day after germination (DAG), pre-treatment with 140 ppm of GA led to upregulation of catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX) and glutathione reductase (GR) accompanied by an increase in ascorbate and proline and decline in hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) contents in the growing tissues of wheat seedlings. Higher phenolic content in the roots and shoots of PBW 175 seedlings was well correlated with lower polyphenol oxidase (PPO) activity and reverse trend was obtained in PBW 621. However, GA pre-treatment resulted in significant increase in total phenolic content of sensitive cultivar. Therefore, pre-treatment with 140 ppm of GA showed the potential of stimulating the activities of H₂O₂-scavenging enzymes and reducing the lipid peroxidation and cell damage as revealed by lower MDA and H₂O₂ content. Under water deficit conditions, pre-treatment with 140 ppm of GA led to significant increase in seedling growth of both the cultivars. GA pre-treatment at 80–140 ppm showed maximum potential of augmenting the antioxidant response which can be exploited further to observe its stress mitigating effects in wheat seedlings.