中文摘要：

通过模拟土壤溶液进行水培试验，研究了锌（Zn）对大麦（Hordeum Vulgate）镉（Cd）、铜（Cu）毒性的影响，以及Zn-Cd和Zn-Cu的联合毒性效应。结果表明：Zn、Cd和Cu单独作用于大麦时，EC。分别为78．01、2．98、0．64μmol·L^-1，Zn的毒性远远小于Cd和Cu。在Zn-Cd混合体系中，当Zn浓度低于5μmol·L^-1时，随着溶液中Zn浓度的增加，EC50（Cd）呈显著的线性增加，表明低浓度Zn对大麦Cd毒性具有抑制作用；利用毒性单位（TU）模型计算了Zn-Cd混合体系的TUmix值，结果显示TUtax≥1TU，且Tu。随Zn浓度的升高而增加，表明Zn、Cd联合作用于大麦时主要表现为拮抗作用，且这种作用和混合体系中Zn的比例有关。在Zn-Cu混合体系中，随着Zn浓度的增加，大麦相对根长（RE）明显减小，EC50（Cu）逐渐降低，表明Zn增强了大麦Cu的毒性；Zn-Cu的Tumix。均小于1TU，Zn、Cu联合作用于大麦时表现为协同毒性作用。

英文摘要：

Metal toxicity to plants is different in single system from in muhiple metal system. Here toxicities of individual Zn, Cd and Cu and Zn-Cd and Zn-Cu mixtures to barley（Hordeum Vulgare ） were tested in nutrient solutions. Toxic unit（TU） model was used to evaluate the combined toxicity of mixture metals. EC50（metal concentration at which root elongation is inhibited by 50% ） were 78.01μmol· L^-1, 2.98μLmoi·L^-1 and 0.64μLmol· L^-1 for Zn, Cd and Cu, respectively, indicating that Cu toxicity was much higher than Cd or Zn in single-met- al system. In binary metal systems, Cd toxicity to barley was inhibited by Zn at 5μmol·L^-1, and the values of EC50（ Cd ） increased signifi- cantly. TUmix values of Zn-Cd were greater than I TU and increased with Zn concentrations, suggesting an antagonistic effect between Zn and Cd at low Zn concentrations. Such antagonism of Zn-Cd was correlated with Zn proportion in the mixture system. At higher concentra- tions（ 〉5μmol· L^-1 ）, Zn exerted high toxicity to barley and increased the joint toxicity of Zn-Cd. Additions of Zn showed greater Cu toxicity to barley than Cu alone. EC5o （Cu） values were higher in Zn-Cu mixture than in single-metal system and decreased dramatically with in- creasing Zn concentrations, showing synergistic toxicity of Zn-Cu. TUmix values of Zn-Cu mixture were less than 1 TU. These results suggest that Cd and Cu may have different toxicity mechanisms, and that more attention should be paid to combined heavy metal pollution.