Background and aims

Chelates like ethylenediaminetetraacetic acid (EDTA) have frequently been applied for facilitating lead (Pb) phytoextraction and cleaning contaminated soils but without detailed report regarding the internal mechanisms happening in plants in response to EDTA addition. This study examined the effect of EDTA on Pb accumulation in Bidens pilosa L., focusing on how EDTA modulates Pb uptake and transport in plants.

Methods

B. pilosa L. was cultured in the environment of ionic Pb and Pb-EDTA complexes. The localization of Pb in the tissues and subcellular fractions of B. pilosa L. was investigated by micro X-ray fluorescence (micro-XRF) and subcellular extraction experiment, respectively. The speciation of Pb in B. pilosa L. was identified by X-ray absorption near-edge structure spectroscopy (XANES).

Results

The application 2.5 mM EDTA greatly enhanced Pb translocation from roots to leaves, with a translocation factor up to 2.43. Micro-XRF imaging revealed that EDTA decreased Pb retention in the meristem zone of root apex and the junction of lateral root zone. Subcellular extraction found that EDTA increased the water-soluble Pb fraction in plant cells by 4–39%, thereby enhancing Pb translocation in plant vascular bundles. XANES analysis further demonstrated that Pb was largely present as stable Pb-phosphate and Pb-cellulose complexes in Pb-only treatment, whereas Pb was mainly present as soluble Pb-EDTA (48.9–74.2%) in Pb and EDTA co-treatment.

Conclusions

The results indicate that the EDTA-enhanced apoplastic flow pathway and internal mobility of Pb together provide a twofold mechanism for facilitating Pb phytoextraction in B. pilosa L. under EDTA addition.

中文翻译：

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评估 EDTA 对黑山病菌 Pb 摄取和转运内部机制的影响

背景和目标

诸如乙二胺四乙酸 (EDTA) 之类的螯合物经常被用于促进植物提取铅 (Pb) 和清洁受污染的土壤，但没有关于植物响应 EDTA 添加的内部机制的详细报告。本研究考察了 EDTA 对白茅根中 Pb 积累的影响，重点关注 EDTA 如何调节植物对 Pb 的吸收和转运。

方法

B. pilosa L. 在离子 Pb 和 Pb-EDTA 复合物的环境中培养。分别通过微 X 射线荧光 (micro-XRF) 和亚细胞提取实验研究了 Pb 在B. pilosa L. 的组织和亚细胞部分中的定位。通过 X 射线吸收近边结构光谱 (XANES) 鉴定了B. pilosa L.中 Pb 的形态。

结果

应用 2.5 mM EDTA 大大增强了 Pb 从根到叶的转运，转运因子高达 2.43。Micro-XRF 成像显示，EDTA 降低了根尖分生组织区和侧根区交界处的铅滞留。亚细胞提取发现 EDTA 使植物细胞中的水溶性 Pb 含量增加了 4-39%，从而增强了植物维管束中 Pb 的易位。XANES 分析进一步表明 Pb 在仅 Pb 处理中主要以稳定的 Pb-磷酸盐和 Pb-纤维素复合物存在，而在 Pb 和 EDTA 共处理中 Pb 主要以可溶性 Pb-EDTA (48.9-74.2%) 的形式存在。

结论

结果表明，EDTA 增强的质外体流动途径和 Pb 的内部流动性共同为在 EDTA 添加下促进B. pilosa L. 中 Pb 的植物提取提供了双重机制。