Tandy Susan, Schulin Rainer, Nowack Bernd
Institute of Terrestrial Ecology, Swiss Federal Institute of Technology (ETH), Universitätstrasse 16, CH-8092 Zürich, Switzerland.
Chemosphere. 2006 Mar;62(9):1454-63. doi: 10.1016/j.chemosphere.2005.06.005. Epub 2005 Aug 3.
Phytoextraction is an environmentally friendly in situ technique for cleaning up metal contaminated land. Unfortunately, efficient metal uptake by remediation plants is often limited by low phytoavailability of the targeted metals. Chelant assisted phytoextraction has been proposed to improve the efficiency of phytoextraction. Phytoremediation involves several subsequent steps: transfer of metals from the bulk soil to the root surfaces, uptake into the roots and translocation to the shoots. Nutrient solution experiments address the latter two steps. In this context we investigated the influence of the biodegradable chelating agent SS-EDDS on uptake of essential (Cu and Zn) and non-essential (Pb) metals by sunflowers from nutrient solution. EDDS was detected in shoots and xylem sap for the first time, proving that it is taken up into the above ground biomass of plants. The essential metals Cu and Zn were decreased in shoots in the presence of EDDS whereas uptake of the non-essential Pb was enhanced. We suggest that in the presence of EDDS all three metals were taken up by the non-selective apoplastic pathway as the EDDS complexes, whereas in the absence of EDDS essential metal uptake was primarily selective along the symplastic pathway. This shows that synthetic chelating agents do not necessarily increase uptake of heavy metals, when soluble concentrations are equal in the presence and absence of chelates.
植物提取是一种用于清理金属污染土地的环境友好型原位技术。不幸的是，修复植物对金属的有效吸收常常受到目标金属低植物有效性的限制。已有人提出使用螯合剂辅助植物提取来提高植物提取的效率。植物修复涉及几个后续步骤：金属从大量土壤转移到根表面、被根吸收并转运到地上部分。营养液实验针对的是后两个步骤。在此背景下，我们研究了可生物降解螯合剂SS-EDDS对向日葵从营养液中吸收必需金属（铜和锌）和非必需金属（铅）的影响。首次在地上部分和木质部汁液中检测到乙二胺二琥珀酸（EDDS），证明它被植物地上生物量吸收。在有EDDS存在的情况下，地上部分的必需金属铜和锌含量降低，而非必需金属铅的吸收增强。我们认为，在有EDDS存在时，所有三种金属都通过非选择性质外体途径以EDDS络合物的形式被吸收，而在没有EDDS时，必需金属的吸收主要沿着共质体途径进行选择性吸收。这表明，当螯合剂存在和不存在时可溶浓度相等时，合成螯合剂不一定会增加重金属的吸收。
