Zinc-regulated growth, chlorophyll, and antioxidant activity drive biofortification in rice varieties

Zinc (Zn) is an essential micronutrient that plays a crucial role in numerous physiological and biochemical processes in plants, including enzyme activation, protein synthesis, chlorophyll formation, carbohydrate metabolism, and auxin regulation. Zinc biofortification cahas emerged as an effective strategy to alleviate Zn deficiency by enhancing antioxidant production, improving crop productivity and increasing Zn bioaccumulation in edible tissues. This study evaluated the effects of different concentrations of ZnSO₄ (100, 200, 300, 400, and 500 mM) on growth and performance and osmolyte production (protein and soluble sugars) in two rice (Oryza sativa) varieties. The results showed that Zn concentrations up to 400 mM significantly improved biochemical parameters-protein concentration (by 17.961%), soluble sugar levels (by 13%), and chlorophyll activity (by 45%)-as well as physiological attributes such as plant height (by 9.64%), leaf length (by 163.29%), and leaf width (by 114.759%). Additionally, moderate Zn application reduced H₂O₂ accumulation in rice and enhanced the activity of antioxidant enzymes including catalase (CAT, 30.02%), malondialdehyde (MDA, 34%), and ascorbate peroxidase (APX, 40.958%). However, higher Zn concentrations exerted toxic effects, resulting in reduced growth and biochemical performance. Overall, the findings demonstrate that optimal ZnSO₄ application can increase Zn content by 5-18% and enhance the nutritional and physiological quality of rice cultivated under Zn-deficient conditions. Moderate Zn application improves growth, antioxidant activity, and nutritional quality in rice, whereas excessive Zn concentrations exert toxic effects. These findings support Zn biofortification as a sustainable strategy to enhance crop productivity and nutritional value under Zn-deficient conditions.