Understanding the physiological and biochemical responses of Beta vulgaris to cadmium toxicity and iron supplementation is crucial for optimizing plant performance under heavy metal contamination scenarios. However, knowledge about how varying iron concentrations mediate cadmium-induced stress responses in sugar beet remains limited. We investigated morphological, physiological, and biochemical responses of B. vulgaris exposed to different cadmium concentrations (0, 1, and 2 mg L⁻¹) and iron levels (2.5, 5, and 7.5 mg L⁻¹) under hydroponic conditions through a factorial experiment using completely randomized design with three replications. Cadmium concentration and iron supplementation significantly influenced all measured parameters (p ≤ 0.01). Plants receiving 7.5 mg L⁻¹ Fe consistently demonstrated superior stress tolerance, maintaining higher growth performance, better mineral nutrition, stronger antioxidant defenses, and more effective metabolic regulation under 2 mg L⁻¹ Cd stress compared to control iron levels (2.5 mg L⁻¹). Specifically, higher iron supplementation restored leaf number, leaf area, chlorophyll content, and yield to near-control levels, while also reducing cadmium accumulation in both roots and shoots. Oxidative stress mitigation was also more pronounced with 7.5 mg L⁻¹ Fe treatment, with better restoration of H₂O₂ and malondialdehyde levels to control ranges, suggesting more efficient antioxidant defense mechanisms. Mineral nutrition patterns also differed markedly, with higher iron levels improving Fe, Zn, Cu, and Mn concentrations while simultaneously reducing cadmium uptake and translocation. We conclude that iron supplementation significantly influences B. vulgaris resilience to cadmium toxicity, with 7.5 mg L⁻¹ Fe emerging as the optimal concentration for cadmium stress mitigation. Relative differences in stress response mechanisms between iron treatments provide insights for phytoremediation strategies, while the quantitative stress response patterns identified offer valuable parameters for optimizing sugar beet cultivation in cadmium-contaminated environments.
