The Toxicity And Metabolic Effects Of TiO₂ Nano Particles On Rice ?Oryza Sativa L.?

Nano-TiO₂ is one of the most widely used nanoparticles in the world recently.And it can be inevitably released into the soil during production, transportation,storage, and industrial use, and may cause risk to crop yield and quality.In this study, we studies the toxic effects of nano-TiO₂ on rice, and employed a GC-MS-based metabolomic approach to investigate the potential toxicity of nano-TiO₂ on hydroponically-cultured rice ?Oryza sativa L.? after exposed to 0, 100,250 or 500 mg/L of nano-Ti02 for fourteen days. The main findings of this thesis are summarized below:?1? Nano-TiO₂ was absorbed by the rice roots,and induced oxidative stress in rice, inhibited the iron plaque on rice roots, and influenced the absorption of Fe, Mn and Zn, and finally inhibited the growth of rice.The biomass of rice was decreased under the exposure of nano-TiO₂, and the inhibitory effect on root was stronger than leaf. The activities of antioxidant enzyme and the concentration of histone phosphorylation and ROS all showed the variation tendency of falling after rising, expect peroxidase. The concentration of Fe in roots of experiment group was far below the control, while the concentrations of Fe, Mn and Zn in leaves were increased.?2? Most of the identified metabolites in experimental groups showed significant difference compared to the control. The concentrations of glucose-6-phosphate,glucose-1-phosphate, succinic and isocitric acid were increased most, and were over the 300% of the control, while the concentrations of sucrose, isomaltulose, and glyoxylic acid were decreased most, and the concentrations of glyoxylic acid was 51.7%of the control. Basic energy-generating ways including tricarboxylic acid cycle and the pentose phosphate pathway, were elevated significantly while the carbohydrate synthesis metabolism including starch and sucrose metabolism, and glyoxylate and dicarboxylate metabolism were inhibited. However, the biosynthetic formation of most of the identified fatty acids, amino acids and secondary metabolites which correlated to crop quality, were increased. The results suggest that the metabolism of rice plants is distinctly disturbed after exposure to nano-TiO₂, and nano-TiO₂ would have a mixed effect on the yield and quality of rice.