Zn对大麦Cd、Cu毒性的影响及其联合毒性效应

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。

Toxicity of Cadmium and Copper to Barley in Presence and Absence of Zinc

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.