Effects of alumina nanoparticles on morphological properties and antioxidant system of Triticum aestivum . Ali Riahi-Madvar*, Fatemeh Rezaee and Vahidreza Jalali 2

The negative and positive effects of alumina nanoparticles have been reported for various plant species, while the mechanism that brings about these effects has not yet been clearly understood. Here, the effects of different concentrations of nano-scale alumina on growth and enzymatic antioxidant system of wheat seedlings are investigated. The results show while root growth is affected by the nanoparticles (NPs), other morphological properties including seed germination, shoot length, and dry biomass were the same as the control plants’ properties. This can be attributed to selective permeability of seed coats which confronts roots with excess in the NPs and low rate in transportation of this material to the shoot. Interestingly, while root elongation was significantly improved in both treatments of 50 and 1000 mg/L nano-scale alumina, length of the roots were measured slightly lower than control in cases of 200 and 500 mg/L treatments. Additionally, the activity of superoxidase dismutase and catalase were elevated for treatments of 200 and 500 mg/L while growth of the roots was apparently decreased and the uptake of aluminum by the roots was more than the uptake for other concentrations. However, due to the potential retarding of alumina nanoparticles on root growth for some plant species, it seems that the activity of antioxidant enzymes which reduces the level of free radicals (O˙-, H2O2) is responsible for reducing phytotoxicity effects of these particles on seedlings. In conclusion, it is proposed that oxidative damage can be introduced as a way of inducing toxicity in plants through the uptake of nanoparticles.