title: Effects of exogenous chelators on phytoavailability and toxicity of Pb in Zinnia elegans Jacq.
abstract: 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.
authors.affiliation: Key Laboratory of Terrestrial Ecological Process, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China.
authors.forename: Shuang
authors.initials: S
authors.lastname: Cui
authors.forename: Qi-xing
authors.initials: QX
authors.lastname: Zhou
authors.forename: Shu-he
authors.initials: SH
authors.lastname: Wei
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.forename: Lei
authors.initials: L
authors.lastname: Cao
authors.forename: Li-ping
authors.initials: LP
authors.lastname: Ren
mesh_terms: D019659:Asteraceae / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D001673:Biodegradation, Environmental / Q000187:drug effects; D002614:Chelating Agents / Q000494:pharmacology*; D019343:Citric Acid / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D004785:Environmental Pollutants / Q000378:metabolism / Q000633:toxicity*; D007854:Lead / Q000378:metabolism / Q000633:toxicity*; D019815:Oxalic Acid / Q000494:pharmacology; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development; D018520:Plant Shoots / Q000187:drug effects / Q000254:growth & development; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D013644:Tartrates / Q000494:pharmacology
chemical_list: D002614:Chelating Agents; D004785:Environmental Pollutants; D013644:Tartrates; D019343:Citric Acid; D007854:Lead; D019815:Oxalic Acid; D004492:Edetic Acid; C029768:tartaric acid