Cu2+/Cd2+对玉米的急性毒性及其与重金属在根表形态分布的关系

doi:10.19741/j.issn.1673-4831.2020.0226

摘要/Abstract

摘要： 采用水培方式，结合根伸长、吸附-解吸和流动电位测定，研究Cu²⁺和Cd²⁺对玉米根系毒性的差异及其与根表重金属吸附量的关系，探讨了共存阳离子和有机酸对玉米受Cu²⁺和Cd²⁺毒害的缓解作用及其机制。结果表明，在相同浓度条件下，Cu²⁺对玉米根系的毒性强于Cd²⁺，这主要是玉米根系表面吸附的交换态、络合态和沉淀态Cu²⁺含量大于Cd²⁺所致。当Cu²⁺和Cd²⁺浓度均为1 μmol·L^-1时，玉米根系相对伸长率分别为52.40%和96.23%。当Cu²⁺和Cd²⁺浓度均为40 μmol·L^-1时，玉米根系表面吸附的交换态、络合态和沉淀态Cu²⁺含量分别为相应形态Cd²⁺的1.22、4.36和2.45倍。当pH值为4.5时，共存的Ca²⁺、Mg²⁺、K⁺和NH₄⁺等阳离子通过与2种重金属阳离子竞争玉米根系表面的吸附位可降低根系对重金属阳离子的吸附量，从而缓解玉米根系受Cu²⁺和Cd²⁺的毒害，二价阳离子（Ca²⁺和Mg²⁺）的缓解作用强于一价阳离子（K⁺和NH₄⁺）。柠檬酸、草酸、酒石酸和苹果酸通过与重金属阳离子形成稳定的络合物减少玉米根系对2种重金属阳离子的吸附，从而缓解重金属对玉米根系的毒害。4种有机酸缓解作用由大到小依次为草酸 > 柠檬酸 > 酒石酸≈苹果酸，这与上述有机酸对2种重金属阳离子的络合能力大小顺序基本一致。因此，通过减少植物根系对交换态和络合态重金属的吸附，可以有效减缓重金属对植物的毒害。

关键词: 共存阳离子, 有机酸, Cu²⁺/Cd²⁺, 玉米, 吸附-解吸, 根系相对伸长

Abstract: A solution culture experiment combined with measurements of root elongation, adsorption-desorption, and streaming potential, were used to evaluate the toxicity of Cu²⁺ and Cd²⁺ to maize roots as related with the chemical forms of the metals adsorbed on root surfaces. The alleviative effects of coexisting cations and organic acids on Cu²⁺/Cd²⁺ toxicity to maize as well as the related mechanisms were also investigated. The results show that the toxicity of Cu²⁺ to maize roots was greater than that of Cd²⁺ at the same concentration. This was attributed to the fact that more Cu²⁺ was adsorbed on the root surface as exchangeable, complexed and precipitated forms compared with Cd²⁺. When the concentration of Cu²⁺ and Cd²⁺ was 1 μmol·L^-1, the relative root elongation rates of maize were reduced by 52.40% and 96.23%, respectively, compared with those of the control. When the metal concentration was 40 μmol·L^-1, the amounts of exchangeable, complexed and precipitated Cu²⁺ on the root surface were 1.22, 4.36 and 2.45 times that of Cd²⁺, respectively. At pH 4.5, coexisting cations of Ca²⁺, Mg²⁺, K⁺ or NH₄⁺ reduced the amount of heavy metals adsorbed on the root surface through competition for adsorption sites and thereby alleviating the toxicity of Cu²⁺ and Cd²⁺. Additionally, the alleviative effects of the divalent cations of Ca²⁺ and Mg²⁺ were greater than those of the monovalent cations of K⁺ and NH₄⁺. Furthermore, citric acid, oxalic acid, tartaric acid, and malic acid alleviated Cu²⁺ and Cd²⁺ toxicity to maize by forming stable complexes with the cations and reducing the amount of the metals adsorbed onto the roots. The alleviating effects of the organic acids on Cu²⁺ and Cd²⁺ toxicity followed the order: oxalic acid > citrate > tartaric acid ≈ malic acid, which was consistent with the complexation ability of these organic acids. Therefore, the toxicity of heavy metals to plant roots can be effectively alleviated by reducing the adsorption quantity of their exchangeable and complexed forms on root surfaces.

Key words: coexisting cation, organic acid, Cu²⁺/Cd²⁺, maize, adsorption-desorption, relative root elongation

中图分类号:

董歌, 徐仁扣. Cu²⁺/Cd²⁺对玉米的急性毒性及其与重金属在根表形态分布的关系[J]. 生态与农村环境学报, 2021, 37(3): 387-393.

DONG Ge, XU Ren-kou. Acute Toxicity of Cu²⁺/Cd²⁺ to Maize as Related to Chemical Forms of the Metals on Whole Plant Roots[J]. Journal of Ecology and Rural Environment, 2021, 37(3): 387-393.

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Cu²⁺/Cd²⁺对玉米的急性毒性及其与重金属在根表形态分布的关系

Acute Toxicity of Cu²⁺/Cd²⁺ to Maize as Related to Chemical Forms of the Metals on Whole Plant Roots

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