Different toxicities of nanoscale titanium dioxide particles in the roots and leaves of wheat seedlings.

Despite previous studies on exploring the environmental effects of titanium dioxide nanoparticles particle (nTiO 2 ) on plants, the detailed impacts of nTiO 2 on the antioxidant system and photosynthesis of plants is still not well understood. This study was aimed at investigating the physiological and biochemical responses to nTiO 2 by oxidative damage, Ti bioaccumulation, cell death, and photosynthesis in wheat. The results showed that 5.0 g nTiO 2 L -1 resulted in a significant decrease in plant growth, chlorophyll contents, and photosynthetic activity. However, the obvious accumulation of reactive oxygen species (ROS) and cell death were observed under nTiO 2 treatments in wheat roots and leaves. In addition, the concentrations of Ti in the roots were significantly higher than that in leaves with increased nTiO 2 concentrations. Significant increase in enzyme activities and the levels of ascorbate were found in leaves exposed to 1.0 and 5.0 g nTiO 2 L -1 . Furthermore, the level of D1 and PsbS remarkably decreased in wheat leaves at 5.0 g nTiO 2 L -1 . However, the strong phosphorylation of photosystem II (PSII) reaction center protein D1 and D2 was observed at 5.0 g nTiO 2 L -1 . Altogether, these findings demonstrated that the roots suffered from more severe toxic damage from nTiO 2 than the leaves and wheat plants respond to nTiO 2 through the different physiological and biochemical mechanisms in the roots and leaves.