Cui Shuang, Zhou Qi-xing, Wei Shu-he, Zhang Wei, Cao Lei, Ren Li-ping
Key Laboratory of Terrestrial Ecological Process, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China.
J Hazard Mater. 2007 Jul 19;146(1-2):341-6. doi: 10.1016/j.jhazmat.2006.12.028. Epub 2006 Dec 16.
Chelate-enhanced phytoremediation is considered as an effective method for the extraction of lead (Pb) by plants. However, more detailed studies are needed to evaluate the effect of exogenous chelators on phytoavailability and toxicity of Pb in plants, then to find out the proper applied concentration of chelators to minimize the combined toxicity to the plants and maximize phytoavailable Pb. To clarify these questions, the seed germination test of Zinnia elegans Jacq. exposed to solutions containing Pb and four types of chelators including sodium ethylenediamine tetra-acetic acid (Na2EDTA), oxalic acid, tartaric acid and citric acid was observed. The results showed that the roots and shoots treated with equimolar chelators and Pb were longer than those treated with half and two folds of the molar concentrations of Pb. The growth of seedlings was inhibited by surplus addition of chelators, and the toxicity of complexes was less than that of Pb and chelators. In particular, 2.4 mM EDTA and 1.2 mM oxalic acid significantly (P<0.05) increased Pb uptake when the seeds were treated with 2.4 mM Pb. In the 4.8 mM Pb solution, Pb accumulation in the seedlings was markedly (P<0.05) increased by 4.8 mM EDTA, 2.4 mM tartaric acid, 4.8 mM tartaric acid and 2.4 mM citric acid, and amounted to 6752.4, 6453.8, 6541.4 and 6598.3 microg g(-1), respectively. With the superfluous addition of chelators, Pb accumulation in the seedlings decreased in a concentration-dependent manner. When Pb was used at 2.4 mM, an equimolar concentration of EDTA not only increased Pb uptake but also stimulated the seedling growth. Thus, chelating agents in their appropriately concentrations could counteract Pb toxicity, but superfluous chelators resulted in less Pb uptake and growth inhibition of the seedlings.
螯合增强植物修复被认为是一种通过植物提取铅（Pb）的有效方法。然而，需要更详细的研究来评估外源螯合剂对植物中铅的植物有效性和毒性的影响，进而找出螯合剂的合适施用浓度，以将对植物的联合毒性降至最低，并使植物可利用的铅最大化。为了阐明这些问题，观察了百日草种子在含有铅和四种螯合剂（包括乙二胺四乙酸二钠（Na2EDTA）、草酸、酒石酸和柠檬酸）的溶液中的发芽试验。结果表明，用等摩尔螯合剂和铅处理的根和芽比用铅摩尔浓度一半和两倍处理的根和芽更长。过量添加螯合剂会抑制幼苗生长，且复合物的毒性小于铅和螯合剂的毒性。特别是，当种子用2.4 mM铅处理时，2.4 mM乙二胺四乙酸二钠和1.2 mM草酸显著（P<0.05）增加了铅的吸收。在4.8 mM铅溶液中，幼苗中的铅积累量因4.8 mM乙二胺四乙酸二钠、2.4 mM酒石酸、4.8 mM酒石酸和2.4 mM柠檬酸而显著（P<0.05）增加，分别达到6752.4、6453.8、6541.4和6598.3 μg g(-1)。随着螯合剂的过量添加，幼苗中铅的积累量呈浓度依赖性下降。当铅浓度为2.4 mM时，等摩尔浓度的乙二胺四乙酸二钠不仅增加了铅的吸收，还刺激了幼苗生长。因此，适当浓度的螯合剂可以抵消铅的毒性，但过量的螯合剂会导致铅吸收减少和幼苗生长受抑制。
