Elucidating the mechanisms for plant uptake and in-planta speciation of cerium in radish (Raphanus sativus L.) treated with cerium oxide nanoparticles
Elucidating the mechanisms for plant uptake and in-planta speciation of cerium in radish (Raphanus sativus L.) treated with cerium oxide nanoparticles
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DOI：
10.1016/j.jece.2016.12.036
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发表时间：
2017-02
影响因子：
7.7
通讯作者：
Weilan Zhang;Yongbo Dan;Honglan Shi;Xingmao Ma
中科院分区：
文献类型：
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作者：
Weilan Zhang;Yongbo Dan;Honglan Shi;Xingmao Ma
尽管植物对氧化铈纳米颗粒（CeO2NPs）的吸收已有报道，但其机制仍然未知。本研究旨在通过两个目标为植物吸收 CeO2NPs 提供新的见解：（1）研究 CeO2NPs 在植物吸收之前是否溶解；（2）确定 Ce 的植物内形态。通过在含有 10 mg Ce/L 散装 CeO2 颗粒、CeO2 NP 或离子 Ce 的溶液中种植萝卜来进行小规模实验。透射电子显微镜和电感耦合等离子体质谱 (ICP-MS) 分析表明，CeO2NP 吸收的一种途径是直接吸收完整的 CeO2NP。更重要的是，我们的结果证实，部分颗粒状 CeO2 在被植物吸收之前在根表面转化为离子 Ce。离子 Ce 吸收和运输是植物芽中 Ce 积累的主要机制。本研究进一步证明根部表面CeO2溶解增强是由于萝卜根部分泌物中分子量较低的有机酸（例如琥珀酸）所致。在仅用离子 Ce 处理的萝卜根中检测到由高含量 P 和 Ce 组成的大颗粒，表明形成了 CePO4 颗粒。总之，结果表明 CeO2NPs 被萝卜吸收为完整的纳米颗粒和溶解的离子。在植物组织内，Ce 以 CeO2NP、溶解的 Ce 和 Ce 盐（例如 CePO4）的混合物形式存在，并且 Ce 种类的具体组合取决于组织。
Even though the plant uptake of cerium oxide nanoparticles (CeO2NPs) has been reported, the mechanisms remain unknown. This study aimed to provide new insights into CeO2NPs plant uptake through two objectives: (1) to investigate whether CeO2NPs dissolute before their plant uptake and (2) to determine thein-planta speciationof Ce. Bench scale experiments were conducted by growing radish in solutions containing 10 mg elemental Ce/L of bulk CeO2particles, CeO2NPs or ionic Ce. Transmission electron microscope and inductively coupled plasma-mass spectrometry (ICP-MS) analysis suggested that one pathway for CeO2NPs uptake was through direct uptake of intact CeO2NPs. More importantly, our results confirmed that part of the particulate CeO2was transformed into ionic Ce on the root surface before they were taken up by plants. Ionic Ce uptake and transport was a primary mechanism for Ce accumulation in plant shoots. This study further demonstrated that enhanced CeO2dissolution on root surface was due to the organic acids with lower molecular weight (e.g.succinic acid) in radish root exudates. Large particles composed of high contents of P and Ce were detected in radish roots treated only with ionic Ce, suggesting the formation of CePO4particles. In summary, the results indicated that CeO2NPs was taken up by radish as both intact nanoparticles and dissolved ions. Inside plant tissues, Ce is present as a cocktail of CeO2NPs, dissolved Ce and Ce salt (e.g. CePO4) and the specific combination of Ce species is tissue dependent.