title: Predicting effects of cations on copper toxicity to lettuce (Lactuca sativa) by the biotic ligand model.
abstract: A biotic ligand model (BLM) was developed to estimate Cu toxicity to lettuce (Lactuca sativa) in terms of root elongation after 4 d of exposure. Effects of Na(+), K(+), Ca(2+), and Mg(2+) on Cu toxicity were examined. The addition of these cations resulted in a 50-fold difference in the copper median effective activity (EC50 cu2+). However, these variations could not be interpreted entirely as a function of the concentrations of these cations alone. In particular, only the relationship between EC50 cu2+ and the activity of protons was found to be significant in the whole range of pH examined from 5.0 to 7.0. The addition of K(+), Na(+), Ca(2+), and Mg(2+) at concentrations up to 20 mM resulted in a 16-fold difference in EC50 cu2+ values. This difference was significant, as indicated by non-overlapping standard deviations of the negative logarithm of EC50 cu2+ pEC50 cu2+) obtained with (7.37 ± 0.22) and without (6.76 ± 0.22) additions of K(+), Na(+), Ca(2+), and Mg(2+). The variations were not statistically significantly related to concentrations of these cations; therefore, only protons can be integrated in the BLM predicting Cu toxicity to lettuce L. sativa with the important parameters: log K(HBL) =6.27, log K(CuBL) =7.40, and [formula in text]. The lack of significant relationships between EC50 cu2+ and concentrations of the cations was not in line with the main assumption of the BLM about the competition between cations for binding sites.
authors: Department of Environmental Sciences, Radboud University Nijmegen, Nijmegen, The Netherlands.
authors: T T Yen
authors: TT
authors: Le
authors: Willie J G M
authors: WJ
authors: Peijnenburg
authors: A Jan
authors: AJ
authors: Hendriks
authors: Martina G
authors: MG
authors: Vijver
mesh_terms: D001665:Binding Sites; D002118:Calcium / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity; D002412:Cations / Q000633:toxicity; D003300:Copper / Q000378:metabolism / Q000633:toxicity*; D018545:Lactuca / Q000187:drug effects* / Q000378:metabolism; D008024:Ligands; D008274:Magnesium / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity; D008954:Models, Biological; D008956:Models, Chemical; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D011188:Potassium / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity; D012964:Sodium / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity; D012989:Soil Pollutants / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity*
chemical_list: D002412:Cations; D008024:Ligands; D012989:Soil Pollutants; D003300:Copper; D012964:Sodium; D008274:Magnesium; D011188:Potassium; D002118:Calcium