Abstract
Heavy metal pollution poses a major threat to ecosystems and the health of living organisms. In the present study, we investigated the effects of zinc and copper by applying ZnSO₄ and CuSO₄·6H₂O solution on the physiological and biochemical processes in barley (Hordeum vulgare L.) cv. Astana-2000 seedlings, 1 mM solutions of ZnSO₄ and CuSO₄·6H₂O were used. Sulfite oxidase (SO) is an enzyme that contains molybdenum and that contributes to sulfite detoxification and the regulation of redox reactions. The present research focuses on the impact of Zn and Cu on the enzyme SO activity. Zn and Cu treatments apparently induce moderate stress by stimulating SO activity, thereby enhancing sulfite detoxification and maintaining cellular redox balance. These results suggest that Zn and Cu differently affect the SO regulatory mechanism, also showing the participation of SO in the early regulation of redox balance and defense mechanism in barley under heavy metal stress. These findings support the importance of studying heavy metal interactions to develop strategies for enhancing plant tolerance to Zn, Cu, and similar stress conditions.