Multilevel Analysis of Glutathione-Induced Responses in Pepper Seedlings Under Water-Deficit Conditions

Drought stress is a major abiotic factor that negatively affects plant growth, physiological processes, and yield in pepper cultivation. This study evaluated the ameliorative effects of exogenous glutathione (GSH) at 50 µM and 100 µM in pepper seedlings grown under water-restricted conditions (60% field capacity), using morphological, physiological, and biochemical parameters. Water restriction significantly reduced seedling height, stem diameter, leaf area, and plant and root fresh and dry weights, and decreased chlorophyll a, chlorophyll b, total chlorophyll content, and plant growth hormones. Conversely, water restriction significantly increased hydrogen peroxide (H2O2), malondialdehyde (MDA), proline, sucrose, and abscisic acid (ABA) content. Glutathione application, on the other hand, significantly reduced water-restriction-induced growth damage, increased biomass production and chlorophyll content, and supported the antioxidant defense capacity of plants by decreasing H2O2 and MDA levels, which are indicators of oxidative stress. It also improved osmotic balance by regulating proline and sucrose accumulation and increased seedling adaptation to water restriction. In conclusion, exogenous GSH acted as a potential biostimulant under water-deficit conditions, with its beneficial effects associated with improved osmotic adjustment through the regulation of proline and sucrose accumulation, enhanced antioxidant defense, and modulation of endogenous phytohormone levels.