Sorghum roots are inefficient in uptake of EDTA-chelated lead.
Sorghum roots are inefficient in uptake of EDTA-chelated lead.
复制标题
DOI：
10.1093/aob/mcm038
复制
发表时间：
2007-05
期刊：
影响因子：
4.2
通讯作者：
Yong Xu;N. Yamaji;R. Shen;J. Ma
中科院分区：
文献类型：
--
作者：
Yong Xu;N. Yamaji;R. Shen;J. Ma
背景与目的乙二胺四乙酸（EDTA）辅助植物修复技术已被开发用于铅污染土壤的修复；然而，EDTA-Pb复合物摄取的机制尚不清楚。本研究通过比较EDTA-Pb在高粱（sorghum bicolor）中的离子Pb [Pb(NO(3))(2)]，表征了EDTA-Pb对Pb的富集过程。方法将高粱幼苗暴露于含有0.1 mM CaCl(2) （pH 5.0）溶液中，其中含有0.1 mM Pb(NO(3))(2)或EDTA-Pb配合物，摩尔比分别为1:0.5、1:1、1:2和1:4 （Pb:EDTA）。测定了不同Pb:EDTA配比对高粱根系伸长的影响。在不同的断茎时间采集木质部汁液。用原子吸收分光光度法测定了铅在芽和根中的浓度。另外，用氟染料I对根进行染色，观察根的结构。结果EDTA-Pb按1:1比例处理后，植株茎部铅累积量仅为相同浓度离子Pb处理的1 / 5。当蒸腾作用受到抑制时，铅的累积量减少。经edta -Pb处理的植株木质部液中Pb的浓度约为外源液的1/ 25000。离子Pb对根伸长有明显的抑制作用，但EDTA-Pb对根伸长没有明显的抑制作用。根染色表明，离子Pb对根的生理屏障有破坏作用，EDTA-Pb对根的生理屏障没有破坏作用。结论高粱根系对edta螯合Pb的吸收效率较低，Pb离子对Pb积累的增强可能与根系结构受损有关。
BACKGROUND AND AIMS Ethylene diamine tetraacetic acid (EDTA)-assisted phytoremediation has been developed to clean up lead (Pb)-contaminated soil; however, the mechanism responsible for the uptake of EDTA-Pb complex is not well understood. In this study, the accumulation process of Pb from EDTA-Pb is characterized in comparison to ionic Pb [Pb(NO(3))(2)] in sorghum (Sorghum bicolor). METHODS Sorghum seedlings were exposed to a 0.5 mM CaCl(2) (pH 5.0) solution containing 0, 1 mM Pb(NO(3))(2) or EDTA-Pb complexes at a molar ratio of 1:0.5, 1:1, 1:2 and 1:4 (Pb:EDTA). The root elongation of sorghum at different ratios of Pb:EDTA was measured. Xylem sap was collected after the stem was severed at different times. The concentration of Pb in the shoots and roots were determined by an atomic absorption spectrometer. In addition, the roots were stained with Fluostain I for observation of the root structure. KEY RESULTS Lead accumulation in the shoots of the plants exposed to EDTA-Pb at 1:1 ratio was only one-fifth of that exposed to ionic Pb at the same concentration. Lead accumulation decreased when transpiration was suppressed. The concentration of Pb in the xylem sap from the EDTA-Pb-treated plants was about 1/25,000 of that in the external solution. Root elongation was severely inhibited by ionic Pb, but not by EDTA-Pb at a 1:1 ratio. Root staining showed that a physiological barrier was damaged in the roots exposed to ionic Pb, but not in the roots exposed to EDTA-Pb. CONCLUSIONS All these results suggest that sorghum roots are inefficient in uptake of EDTA-chelated Pb and that enhanced Pb accumulation from ionic Pb was attributed to the damaged structure of the roots.