Lin Daohui, Xing Baoshan
Department of Environmental Science, Zhejiang University, Hangzhou 310028, China.
Environ Sci Technol. 2008 Aug 1;42(15):5580-5. doi: 10.1021/es800422x.
Increasing application of nanotechnology highlights the need to clarify nanotoxicity. However, few researches have focused on phytotoxicity of nanomaterials; it is unknown whether plants can uptake and transport nanoparticles. This study was to examine cell internalization and upward translocation of ZnO nanoparticles by Lolium perenne (ryegrass). The dissolution of ZnO nanoparticles and its contribution to the toxicity on ryegrass were also investigated. Zn2+ ions were used to compare and verify the root uptake and phytotoxicity of ZnO nanoparticles in a hydroponic culture system. The root uptake and phytotoxicity were visualized by light scanning electron, and transmission electron microscopies. In the presence of ZnO nanoparticles, ryegrass biomass significantly reduced, root tips shrank, and root epidermal and cortical cells highly vacuolated or collapsed. Zn2+ ion concentrations in bulk nutrient solutions with ZnO nanoparticles were lower than the toxicity threshold of Zn2+ to the ryegrass; shoot Zn contents under ZnO nanoparticle treatments were much lower than that under Zn2+ treatments. Therefore, the phytotoxicity of ZnO nanoparticles was not directly from their limited dissolution in the bulk nutrient solution or rhizosphere. ZnO nanoparticles greatly adhered on to the rootsurface. Individual ZnO nanoparticles were observed present in apoplast and protoplast of the root endodermis and stele. However, translocation factors of Zn from root to shoot remained very low under ZnO nanoparticle treatments, and were much lower than that under Zn2+ treatments, implying that little (if any) ZnO nanoparticles could translocate up in the ryegrass in this study.
纳米技术应用的不断增加凸显了阐明纳米毒性的必要性。然而，很少有研究关注纳米材料的植物毒性；植物是否能够吸收和转运纳米颗粒尚不清楚。本研究旨在检测多年生黑麦草对氧化锌纳米颗粒的细胞内化及向上运输情况。同时还研究了氧化锌纳米颗粒的溶解及其对黑麦草毒性的影响。在水培系统中，使用锌离子来比较和验证氧化锌纳米颗粒的根部吸收和植物毒性。通过光扫描电子显微镜和透射电子显微镜观察根部吸收和植物毒性情况。在存在氧化锌纳米颗粒的情况下，黑麦草生物量显著降低，根尖萎缩，根表皮和皮层细胞高度液泡化或塌陷。含有氧化锌纳米颗粒的大量营养液中的锌离子浓度低于锌对黑麦草的毒性阈值；氧化锌纳米颗粒处理下地上部锌含量远低于锌离子处理下的含量。因此，氧化锌纳米颗粒的植物毒性并非直接源于其在大量营养液或根际中的有限溶解。氧化锌纳米颗粒大量附着在根表面。观察到单个氧化锌纳米颗粒存在于根内皮层和中柱的质外体和原生质体中。然而，在氧化锌纳米颗粒处理下，锌从根到地上部的转运系数仍然非常低，且远低于锌离子处理下的转运系数，这意味着在本研究中，很少（如果有的话）氧化锌纳米颗粒能够在黑麦草中向上转运。
