Effects Of TiO₂ Nanoparticles On Photosystem And Antioxidant Systems In Wheat Seedlings

With the rapid development of nanotechnology,the application fields of nanomaterials have become more and more extensive.At the same time,biosafety issues of nanomaterials are increasingly attracting the attention of scientists from all over the world.The unique physicochemical properties of nTiO₂determine the characteristics of its toxicological research.During the application and recycling process of nTiO₂,it can enter the soil,air,and water environment through various ways,and finally enter the organism,normal to the object.Physiological and biochemical functions are affected to a certain extent.Therefore,the safety evaluation and risk rating of nTiO₂has become a new topic for toxicology in the 21st century.This paper mainly studied the toxic effects of five different concentrations of nano-titania suspension on wheat.The paper explored the antioxidant system and photosynthetic system of wheat to evaluate the safety of nTiO₂to higher plants,providing a theoretical basis for the potential impact of nTiO₂on higher plants.In this study,we investigated the single treatment of wheat with nTiO₂suspension containing 0 g·L^-1,0.1 g·L^-1,0.5 g·L^-1,1 g·L^-1and 5 g·L^-1of concentration.After 14 days of treatment,the relevant parameters in the wheat antioxidant system and photosynthetic system were determined.The results showed that with the increase of nTiO₂suspension concentration,the content of Ti in wheat roots and leaves increased significantly,while the root length,seedling length,germination rate,chlorophyll content,and total protein content were significantly reduced.In the aspect of antioxidant system,the content of active oxygen,malondialdehyde and electrical conductivity in roots and leaves increased significantly with the increase of nTiO₂suspension concentration.The cumulative amount of superoxide anion and hydrogen peroxide in roots and leaves gradually increased.The content of superoxide dismutase(SOD),catalase(CAT),peroxidase(POD),ascorbate peroxidase(APX),glutathione peroxidase(GPX)increased in wheat roots and leaves.In terms of photosynthetic systems,high-concentration nTiO₂suspension can significantly reduce transpiration rate,stomatal conductance,and net photosynthetic rate in wheat leaves.In Photosystem ?,the actual quantum yields(?PS?),photochemical quenching(q P)and non-photochemical quenching(NPQ)values of photosystem ? are significantly reduced with the increase of nTiO₂concentration,and the amount of non-adjusted energy dissipated.Quantum yield Y(NO)increased significantly.Immunoblot analysis showed that the content of thylakoid protein D2 and Psb S decreased significantly under high concentration of nTiO₂stress.In addition,the D1 protein undergoes significant phosphorylation as the nTiO₂concentration increases.The results show that nTiO₂can be absorbed into the wheat roots and transported to the leaves,and to a certain extent,increased the activity of antioxidant enzymes.High-concentration nTiO₂inhibits the growth of wheat,impairs the cellular membrane of wheat,and reduces the photosynthetic capacity of wheat,resulting in degradation of the core protein in photosystem ?.