The uptake, transport, and toxicity mechanisms of zinc oxide (ZnO) engineered nanomaterials (ZnO-ENMs) in aquatic plants remain obscure. We investigated ZnO-ENM uptake and phytotoxicity in Phragmites australis by combining Zn stable isotopes and microanalysis. Plants were exposed to four ZnO materials: micron-size ZnO, nanoparticles (NPs) of <100 nm or <50 nm, and nanowires of 50 nm diameter at concentrations of 0–1000 mg l⁻¹. All ZnO materials reduced growth, chlorophyll content, photosynthetic efficiency, and transpiration and led to Zn precipitation outside the plasma membranes of root cells. Nanoparticles <50 nm released more Zn²⁺ and were more toxic, thus causing greater Zn precipitation and accumulation in the roots and reducing Zn isotopic fractionation during Zn uptake. However, fractionation by the shoots was similar for all treatments and was consistent with Zn²⁺ being the main form transported to the shoots. Stable Zn isotopes are useful to trace ZnO-ENM uptake and toxicity in plants.

中文翻译：

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稳定的锌同位素揭示了芦苇中氧化锌工程纳米材料的吸收和毒性

氧化锌（ZnO）工程纳米材料（ZnO-ENMs）在水生植物中的吸收，运输和毒性机理仍然不清楚。我们通过结合锌稳定同位素和微量分析研究了芦苇中ZnO-ENM的吸收和植物毒性。植物暴露于四种ZnO材料：微米级ZnO，<100 nm或<50 nm的纳米颗粒（NP）和直径为50 nm的纳米线，浓度为0–1000 mg l ^-1。所有的ZnO材料都会降低生长，叶绿素含量，光合效率和蒸腾作用，并导致Zn沉淀在根细胞质膜外。<50 nm的纳米颗粒释放更多的Zn ²⁺且毒性更高，因此导致更大的锌沉淀和在根部积累，并减少了锌吸收过程中的锌同位素分馏。但是，在所有处理中，枝条的分馏均相似，并且与Zn ²⁺是转运至枝条的主要形式相一致。稳定的锌同位素可用于追踪植物中ZnO-ENM的吸收和毒性。