Optimal Nanocopper Enhances Cadmium Tolerance in Brassica napus by Regulating Nutritional Homeostasis, Antioxidant Defense, Chelation Capacity, and Cellular Changes

The potency of foliar-sprayed copper oxide nanoparticles (CuO NPs) in mitigating cadmium (Cd) phytotoxicity in oilseed crops are less reported. A pot experiment examined the effectiveness of foliar-sprayed CuO NPs in alleviating the toxic impacts of Cd (10 mg/kg) in B. napus (ZD 635 and ZD 622 cultivars). The study demonstrated that CuO NPs substantially promoted nutrients acquisition, photosynthetic activity, restored stomatal structure by optimizing gas exchanges, resulting in greater seedling growth and biomass accumulation. Under Cd stress, CuO NPs substantially declined the oxidative stress by minimizing the accumulation of Cd (25‒36%), MDA (25‒39%), H₂O₂ (24‒29%), O₂•^– (23‒30%) and strengthen plant immunity by improving antioxidant defense and phytochelatin-based Cd sequestration (upregulating PCs1 and ABC1). Under Cd stress, the application to CuO NPs significantly improved the soil health, as indicated by increased activity of key soil enzymes (β-glucosidase, chitinase, catalase and urease). The anatomical changes further verified that CuO NPs effectively recovered the Cd-induced cellular distortions to the leaf ultrastructure. The findings revealed that CuO NPs exerted a stronger effect on ZD 635, whereas Cd showed greater toxicity in ZD 622. Conclusively, CuO NPs act as stress-mitigating agent in Cd-contaminated areas, enabling safer cultivation of oilseed crops.