Oxidative Stress and Tissue-Specific Physiological Responses Induced by Salinity in Oenothera biennis Seedlings

Abstract Salinity is among the most critical abiotic stress factors restricting plant growth and development. In this study, the physiological responses of Oenothera biennis (evening primrose) seedlings to varying NaCl concentrations (0, 25, 50, and 100 mM) were investigated under controlled hydroponic conditions. Seeds were germinated in perlite within a climate chamber and subsequently transferred to vessels containing 10% nutrient solution. Following an acclimatization period, seedlings were exposed to NaCl treatments for 10 days. The results demonstrated that increasing NaCl concentrations significantly reduced root and shoot biomass. Similarly, the levels of photosynthetic pigments, total protein, and non-protein sulfhydryl groups declined under salt stress. Carbohydrates decreased in the roots, whereas they increased in the shoots. Moreover, elevated levels of total phenolics, hydrogen peroxide, and malondialdehyde were detected in both roots and shoots. These findings suggest that NaCl toxicity induces oxidative stress in O. biennis, triggering biochemical alterations associated with stress response mechanisms.