Impact of iron oxide nanoparticles on cadmium toxicity mitigation in Brassica napus.

Cadmium (Cd) contamination greatly hinders plant productivity. Nanotechnology offers a promising solution for Cd phytotoxicity. The novelty of this study lies in the limited research on the effects of nanoiron (Fe₃O₄NPs) in regulating Cd toxicity in oilseed crops. This study examined how Fe₃O₄NPs regulated the Cd-exposure in B. napus. Foliar spray of 10 mg L^-1 Fe₃O₄NPs was applied to 50 μM Cd-stressed B. napus seedlings via leaf exposure in hydroponic system. Under Cd stress, Fe₃O₄NPs decreased the Cd-accumulation (25-37%) due to adsorption followed by more root Cd-immobilization, and increased the plant height (23-31%) and biomass (17-24%). These findings were directly correlated with better photosynthetic activity (chlorophylls, gas exchanges and photosynthetic efficiency), leaf stomata opening and nutrients accumulation (20-29%). Subcellular localization revealed that Fe₃O₄NPs enhanced the binding capacity of cell wall for Cd to hinder its entry into cell organalles and facilitated vacoular sequestration. Additionally, Fe₃O₄NPs decreased the oxidative stress (21-33%) and peroxidation of lipids (24-31%) by regulating the genes-associated to superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, glutathione reductase, reduced glutathione, phytochelation, chlorophyll synthesis and Cd-transporters. Fe₃O₄NPs protected plant roots from Cd-induced cell structural damages and cell death. Among studied parameters, ZD 635 exhibited greater tolerance to Cd stress when compared to ZD 622 cultivar. Findings revealed that Fe₃O₄NPs effectively mitigate Cd toxicity by improving the photosynthesis, antioxidant defense mechanisms, cellular protection, nutrients accumulation and limiting Cd accumulation. This research offers a benchmark for the practical applicability of Fe₃O₄NPs to enhance the quality of canola production in Cd-contaminated soils.