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 (AsO43-) and Fe2O3-NPs on early seedling growth of Vigna radiata. Seedlings were raised in AsO43- and Fe2O3-NPs, alone and in combination. While Fe2O3-NPs slightly promoted seedling growth, AsO43- reduced seedling growth drastically. AsO43--induced decline in the seedling growth was recovered by Fe2O3-NPs. In contrast, equivalent concentrations of FeCl3, alone and together with AsO43-, 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 AsO43-, 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. AsO43- enhanced the ferric chelate reductase activity of root which was recovered by Fe2O3-NPs. The AsO43--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.