纳米银对水生植物紫萍光合作用的毒性效应及其作用机制

The widespread use of silver nanoparticles (AgNPs) makes it inevitably released into the aquatic environment and has toxicity to aquatic plants. Previous studies have shown that AgNPs can affect the photosynthesis of aquatic plants. However, how AgNPs affect plant photosynthesis that it is still not clear. In this project, an aquatic ecotoxicology model plant, Spirodela polyrhiza, was chosen as the experimental material. Cloud point extraction, X-ray fluorescence, X-ray absorption near edge structure, and ultramicroscopy techniques were used to investigate the absorption and internalization of AgNPs in the aquatic plant, and their effects on chloroplast morphology and structure; Measurement of ability of light absorption and transformation, oxygen evolution rate, electron transfer rate, photosynthetic phosphorylation, and the activity of the enzymes of Calvin cycle were used to clarify the effects of silver nanoparticles on the photosynthesis process of the aquatic plant; The interactions between proteins and AgNPs will be investigated, the changes of morphology of silver nanoparticles, protein particles, bioactivity and secondary structure of proteins, as well as the determination of specific interactive sites between AgNPs and proteins, were used to demonstrate mechanisms of AgNPs toxicity to photosynthesis. This project will lay the foundation for comprehensive analysis of phytotoxic mechanisms of silver nanoparticles.

纳米银广泛的应用使其不可避免地释放到水环境中对水生植物产生毒害作用。研究表明纳米银可以影响水生植物的光合作用，然而纳米银通过怎样的方式影响植物光合作用尚不明确。本项目拟以生态毒理学的模式水生植物紫萍（Spirodela polyrhiza）为材料，运用浊点萃取、X射线荧光、X射线近边吸收、超微切片和电子显微镜技术研究纳米银在水生植物中的吸收和内化及其对水生植物叶绿体形态与结构的影响；通过研究纳米银对光能吸收与转化能力、放氧速率、电子传递速率、光合磷酸化和卡尔文循环中相关酶活性的影响，阐明纳米银对水生植物光合作用过程的影响；通过研究纳米银和蛋白质相互作用后纳米银的形态结构变化、蛋白质颗粒的变化、蛋白质活性与二级结构的变化以及纳米银和蛋白质相互作用的具体位点的确定，从蛋白质水平揭示纳米银对水生植物光合作用影响的作用机制。本研究将为全方位解析纳米银的植物毒性机制奠定基础。

纳米银广泛的应用使其不可避免地释放到水环境中对水生植物产生毒害作用。研究表明纳米银可以影响水生植物的光合作用，然而纳米银通过怎样的方式影响植物光合作用尚不明确。本项目以生态毒理学的模式水生植物紫萍（Spirodela polyrhiza）为材料，开展纳了米银在紫萍细胞中的吸收和内化研究，发现紫萍对纳米银具有强烈的生物富集作用，且吸收内化的纳米银组要富集在叶绿体中与含S的化合物结合；以此为根据，利用透射电子显微镜观察发现纳米银改变了紫萍叶绿体的形态和结构；进一步通过叶绿素荧光技术，探究了纳米银对紫萍光合作用过程中光反应的影响，发现纳米银显著减少光合系统II反应中心、光能转化效率和电子传递效率；通过对光合作用过程中暗反应关键酶活测定发现Rubisco和NADP-GAPDH活性被纳米银显著抑制，抑制卡尔文循环过程，降低光合速率；最后通过对不同指标半抑制浓度计算，发现NADP-GAPDH可能是纳米银对紫萍光合作用影响的关键酶。本研究将为全方位解析纳米银的植物毒性机制奠定基础。