Non-toxicity of nano alumina: A case on mung bean seedlings.

Wide use of AlO nanoparticles (NPs) leading to their possible escape into environment and their interaction with living organisms demands immediate attention. We evaluated impact of nanoparticulate (AlO-NPs) and ionic (Al) forms of aluminium on early seedling growth of Vigna radiata. While Al inhibited growth of seedlings, AlO-NPs did not affect it negatively. Unlike enhancement in proline, malondialdehyde and HO levels in roots and shoots induced by Al, these stress markers remained unaltered by AlO-NPs. No signs of membrane damage were recorded in roots of seedlings raised in presence of AlO-NPs; this was witnessed from insignificant electrolyte leakage and Evans blue uptake. Activities of antioxidant enzymes, i.e., superoxide dismustase, catalase, guaiacol peroxidase in root and shoot were enhanced by Al. However, they were unaffected by AlO-NPs. Al enhanced levels of non-protein thiols, phenolics and ascorbate, with no alterations induced by AlO-NPs. These findings revealed that, AlO-NPs did not induce oxidative stress in seedlings. Seedlings raised in Al showed higher uptake of Al than those grown in AlO-NPs; Al content was higher in roots. Al was not detected in shoots of seedlings grown in AlO-NPs. Lower translocation of Al in seedlings raised in AlO-NPs was due to adsorption/restriction of AlO-NPs on root surface. Al caused ruptures on root epidermis of seedlings and inhibited root-hair formation, whereas no structural damage was caused by AlO-NPs. Our findings revealed that while ionic Al is highly toxic, nanoparticulate form of Al is non-toxic to growth of V. radiata.