The rhizotoxicity of metal cations is related to their strength of binding to hard ligands

Kopittke, Peter M., Menzies, Neal W., Wang, Peng, McKenna, Brigid A., Wehr, J. Bernhard, Lombi, Enzo, Kinraide, Thomas B. and Blamey, F. Pax C. (2014) The rhizotoxicity of metal cations is related to their strength of binding to hard ligands. Environmental Toxicology and Chemistry, 33 2: 268-277. doi:10.1002/etc.2435

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Author Kopittke, Peter M.
Menzies, Neal W.
Wang, Peng
McKenna, Brigid A.
Wehr, J. Bernhard
Lombi, Enzo
Kinraide, Thomas B.
Blamey, F. Pax C.
Title The rhizotoxicity of metal cations is related to their strength of binding to hard ligands
Journal name Environmental Toxicology and Chemistry   Check publisher's open access policy
ISSN 0730-7268
Publication date 2014
Sub-type Article (original research)
DOI 10.1002/etc.2435
Open Access Status File (Author Post-print)
Volume 33
Issue 2
Start page 268
End page 277
Total pages 10
Place of publication Hoboken, NJ, United States
Publisher John Wiley & Sons
Collection year 2015
Language eng
Subject 2307 Health, Toxicology and Mutagenesis
2304 Environmental Chemistry
Abstract Mechanisms whereby metal cations are toxic to plant roots remain largely unknown. Aluminum, for example, has been recognized as rhizotoxic for approximately 100 yr, but there is no consensus on its mode of action. The authors contend that the primary mechanism of rhizotoxicity of many metal cations is nonspecific and that the magnitude of toxic effects is positively related to the strength with which they bind to hard ligands, especially carboxylate ligands of the cell-wall pectic matrix. Specifically, the authors propose that metal cations have a common toxic mechanism through inhibiting the controlled relaxation of the cell wall as required for elongation. Metal cations such as Al3+ and Hg2+, which bind strongly to hard ligands, are toxic at relatively low concentrations because they bind strongly to the walls of cells in the rhizodermis and outer cortex of the root elongation zone with little movement into the inner tissues. In contrast, metal cations such as Ca2+, Na+, Mn2+, and Zn2+, which bind weakly to hard ligands, bind only weakly to the cell wall and move farther into the root cylinder. Only at high concentrations is their weak binding sufficient to inhibit the relaxation of the cell wall. Finally, different mechanisms would explain why certain metal cations (for example, Tl+, Ag+, Cs+, and Cu2+) are sometimes more toxic than expected through binding to hard ligands. The data presented in the present study demonstrate the importance of strength of binding to hard ligands in influencing a range of important physiological processes within roots through nonspecific mechanisms.
Keyword Binding
Mechanism of toxicity
Root growth
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Agriculture and Food Sciences
Official 2015 Collection
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Citation counts: TR Web of Science Citation Count  Cited 9 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 10 times in Scopus Article | Citations
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