Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
J Exp Bot. 2012 Jan;63(2):659-68. doi: 10.1093/jxb/err254. Epub 2011 Oct 20.
The focus of the present study was to investigate the mechanisms for the alleviation of Cu toxicity in plants by coexistent cations (e.g. Al(3+), Mn(2+), Ca(2+), Mg(2+), H(+), Na(+), and K(+)) and the development of an electrostatic model to predict 50% effect activities (EA50s) accurately. The alleviation of Cu(2+) toxicity was evaluated in several plants in terms of (i) the electrical potential at the outer surface of the plasma membrane (PM) (Ψ(0)(°)) and (ii) competition between cations for sites at the PM involved in the uptake or toxicity of Cu(2+), the latter of which is invoked by the Biotic Ligand Model (BLM) as the sole explanation for the alleviation of toxicity. The addition of coexistent cations into the bulk-phase medium reduces the negativity of Ψ(0)(°) and hence decreases the activity of Cu(2+) at the PM surface. Our analyses suggest that the alleviation of toxicity results primarily from electrostatic effects (i.e. changes in both the Cu(2+) activity at the PM surface and the electrical driving force across the PM), and that BLM-type competitive effects may be of lesser importance in plants. Although this does not exclude the possibility of competition, the data highlight the importance of electrostatic effects. An electrostatic model was developed to predict Cu(2+) toxicity thresholds (EA50s), and the quality of its predictive capacity suggests its potential utility in risk assessment of copper in natural waters and soils.
本研究的重点是研究共存阳离子（如 Al(3+)、Mn(2+)、Ca(2+)、Mg(2+)、H(+)、Na(+)和 K(+)）缓解植物铜毒性的机制，并开发静电模型来准确预测 50%效应活性 (EA50s)。通过以下两种方法评估几种植物中 Cu(2+)毒性的缓解情况：(i) 质膜（PM）外表面的电势能（Ψ(0)(°)）和 (ii) 阳离子与 PM 上参与 Cu(2+)摄取或毒性的位点之间的竞争，后者被生物配体模型（BLM）作为缓解毒性的唯一解释。共存阳离子添加到体相介质中会降低 Ψ(0)(°)的负电性，从而降低 PM 表面 Cu(2+)的活性。我们的分析表明，毒性的缓解主要源自静电效应（即 PM 表面 Cu(2+)的活性和跨 PM 的电驱动力的变化），而 BLM 型竞争效应在植物中可能不太重要。尽管这不能排除竞争的可能性，但数据强调了静电效应的重要性。开发了一种静电模型来预测 Cu(2+)毒性阈值 (EA50s)，其预测能力的质量表明它在评估天然水和土壤中铜的风险方面具有潜在的用途。
