Alleviation of cadmium toxicity by improving antioxidant defense mechanism and nutrient uptake in wheat (Triticum aestivum L.) through foliar application of 24-epibrassinolide under elevated CO2.

Heavy metals like cadmium (Cd) contamination occur in conjunction with the rising CO₂ threatening food security and safety. Foliar application of 24-Epibrassinolide (EBR) was found to ameliorate Cd stress and improve nutrient availability in crops. However, its role under elevated CO₂ is currently unknown. Accordingly, a pot experiment was conducted in open-top chambers (CO₂ at 400 and 600 μmol mol⁻¹) to determine the protective effect of EBR on wheat plants under different Cd concentrations (0, 2, and 4 mg kg^-1) in soil. The foliar application of EBR significantly improved growth, biomass, photosynthesis, proline, total phenol, and total soluble protein in Cd stress treatments under elevated CO₂. Simultaneously, it significantly (p≤ 0.05) increased catalase (42.89%), superoxide dismutase (26.53%), peroxidase (28.10%), and ascorbate peroxidase (61.70%) while reduced malondialdehyde (35.53%), hydrogen peroxide (19.94%), and electrolyte leakage (23.55%) under elevated CO₂ compared to ambient CO₂ conditions. Furthermore, EBR and elevated CO₂ interactively showed a maximum reduction in Cd concentrations and accumulation in the wheat roots (39.74,41.63%), shoots (46.83,44.87%), and grains (27.52,29.06%) respectively. Elevated CO₂ and Cd stress interactively showed a significant reduction in nutrient content. Conversely, the EBR application recovered and significantly increased calcium, magnesium, iron, zinc, and copper content in wheat roots, shoots, and grains. Our findings inferred that EBR foliar application reduced Cd toxicity and improved plant growth and nutritional quality under elevated CO₂.