Reevaluating the free-ion activity model of trace metal toxicity toward higher plants: experimental evidence with copper and zinc

Environmental Toxicology and Chemistry
D R ParkerM Resketo

Abstract

Across a diverse spectrum of organisms, the absorption and toxicity of trace elements are usually correlated with the activity of the free metal ion, but reported exceptions to this generalization are increasing. For the first time, we tested the validity of the free-ion activity model (FIAM) in the case of terrestrial plants and organic acids that may be abundant in the soil solution and rhizosphere. Short-term (48-h) root elongation of wheat (Triticum aestitvum L.) in a simple medium (2 mM CaCl2, pH 6.0) was used to probe the toxicity of Cu and Zn in the presence of malonate, malate, and citrate. Precautions were taken to prevent biodegradation of the organic acids, and its absence was confirmed by ion chromatography. Copper speciation was verified using a Cu-selective ion electrode, and published stability constants were modified to improve agreement between measured and calculated Cu2+ activities. With additions of both malonate and malate, Cu toxicity was alleviated but not to the extent predicted by the FIAM; the Cu-ligand complexes seemingly contributed to the toxicity. No such departures were observed with citrate and Cu nor with any of the three ligands in combination with Zn. Thus, exceptions to the FIAM occur with hi...Continue Reading

References

Jul 15, 1983·European Journal of Biochemistry·J Bergsma, W N Konings

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Citations

Jan 7, 2010·Archives of Environmental Contamination and Toxicology·Yonghong Wu, William H Hendershot
Nov 15, 2003·Waste Management·M R Teira-Esmatges, X Flotats
Sep 8, 2010·SAR and QSAR in Environmental Research·C N Legind, S Trapp
Jun 20, 2015·International Journal of Phytoremediation·Yanzhao FuChunling Luo
May 6, 2003·Environmental Toxicology and Chemistry·Edward Berkelaar, Beverley A Hale
Sep 8, 2010·Environmental Toxicology and Chemistry·Xiao-Fang LiYong-Guan Zhu

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