Iron (III) oxide nanoparticles alleviate arsenic induced stunting in Vigna radiata

Iron nanoparticles (NPs) are widely used for the removal of arsenic from water. In this study, we evaluated the interaction between arsenate (AsO₄^3-) and Fe₂O₃-NPs on early seedling growth of Vigna radiata. Seedlings were raised in AsO₄^3- and Fe₂O₃-NPs, alone and in combination. While Fe₂O₃-NPs slightly promoted seedling growth, AsO₄^3- reduced seedling growth drastically. AsO₄^3--induced decline in the seedling growth was recovered by Fe₂O₃-NPs. In contrast, equivalent concentrations of FeCl₃, alone and together with AsO₄^3-, inhibited seed germination completely. Lower arsenic content in seedlings raised in the presence of Fe₂O₃-NPs indicated that Fe₂O₃-NPs restricted arsenic uptake. Ability of Fe₂O₃-NPs to restrict the arsenic uptake of the seedlings was due to adsorption of AsO₄^3-, as revealed by transmission and scanning electron microscopy. Non-toxic levels of iron in seedlings were due to restriction of Fe₂O₃-NPs to root-surface. AsO₄^3- enhanced the ferric chelate reductase activity of root which was recovered by Fe₂O₃-NPs. The AsO₄^3--induced oxidative stress, evident from high levels of proline, H₂O₂ and malondialdehyde, and lowered root oxidisability was ameliorated by Fe₂O₃-NPs. AsO₄³-induced enhancement in total antioxidant capacity, superoxide dismutase and catalase activity, and decline in guaiacol peroxidase activity were antagonized by Fe₂O₃-NPs. Our findings reveal that Fe₂O₃-NPs provide effective resistance/amelioration to arsenic toxicity by reducing arsenic availability to plants.