Comparative efficacy of gibberellic acid and melatonin seed priming on germination and biochemical responses of maize under drought stress

Drought stress severely limits maize germination and early seedling growth by reducing germination percentage, seedling vigor, water uptake, and biomass, while prolonging mean germination time. This study evaluated the ameliorative effects of seed priming with gibberellic acid (GA 3 ) and melatonin on 10 maize genotypes (CLO 2450, DHM 117, SML 1, VQL 1, SKM 1, SML 2, LM 13, SML 163, SML 165, and SML 28) under 10% PEG-induced osmotic stress. Germination traits, water relations, biomass accumulation, and biochemical parameters, including α-amylase activity, total soluble sugar, proline, total phenolic content, soluble protein, lipid peroxidation, and electrolyte leakage, were assessed at 1, 7, and 14 days. Drought stress markedly suppressed enzymatic activity, carbohydrate mobilization, osmolyte accumulation, and protein content, while increasing oxidative damage and membrane leakage. GA 3 priming (100 ppm) partially restored germination and metabolic traits, whereas higher concentrations showed diminished recovery. Melatonin priming (200 µM) consistently improved germination (>92%), seedling length (~19–20 cm), water uptake (~88%–90%), biomass, and antioxidant defenses, while limiting lipid peroxidation and electrolyte leakage. Violin plot and heatmap analyses confirmed that melatonin treatments closely resembled control performance, whereas GA 3 provided intermediate recovery.