Cu2+、Cd2+、Hg2+对玉米幼苗生长和抗氧化酶活性的影响

【目的】研究必需元素Cu²⁺和非必需元素Cd²⁺、Hg²⁺对玉米幼苗生长及抗氧化酶活性的影响，探讨玉米抵抗重金属毒害的机理。【方法】用自来水(CK)及高(1 mmol/L)、中(0.5 mmol/L)、低(0.25 mmol/L) 3个浓度的重金属离子Cu²⁺、Cd²⁺、Hg²⁺溶液滴灌玉米幼苗，处理3 d后测定玉米幼苗根长和叶长、可溶性蛋白和叶绿素含量及超氧化物歧化酶（SOD）、过氧化物酶（POD）的活性，并对根系和叶片中POD同工酶表达的变化进行电泳分析。【结果】与CK相比，3种重金属离子明显抑制玉米幼苗生长，提高根系和叶片中可溶性蛋白含量，对叶绿素含量的影响与其浓度有关。Cu²⁺对玉米根系中SOD活性无明显影响，Cd²⁺和Hg²⁺明显降低了根系中SOD活性。Cu²⁺使玉米幼苗根系中POD活性增强；低浓度Cd²⁺和Hg²⁺使玉米根系中POD活性增强，中、高浓度Cd²⁺和Hg²⁺则使玉米根系中POD活性减弱。重金属对根系中POD同工酶的影响表现为：Cu²⁺无明显影响，Cd²⁺减弱了Rb1和Rb2的表达，Hg²⁺则抑制了Rb1的表达，增强了Rb2的表达，且低浓度Hg²⁺诱导出了Rb3。重金属对叶片中POD同工酶的影响表现为：随着处理浓度的增大，Lb5表达增强，其中Cd²⁺的诱导效果最强；与CK 及Cu²⁺ 和Cd²⁺相比，Hg²⁺完全抑制了Lb6的表达。【结论】Cu²⁺、Cd²⁺、Hg²⁺对玉米生长及SOD和POD活性的影响，与重金属种类和浓度有关，并存在器官特异性。重金属中必需元素和非必需元素都会影响POD同工酶的表达，但作用机理不同。

Effects of Cu2+,Cd2+,Hg2+ on the antioxidant enzyme activities of maize seedlings

【Objective】The effects of Cu2+,Cd2+,Hg2+ on several physiological indexes of maize seedling were conducted in order to investigate plants resistance mechanisms to different types of heavy metal ion.【Method】The maize seedlings were treated with Cu2+,Cd2+,Hg2+ with different concentrations including 0,0.25,0.5,1.0 mmol/L for 3 days and the length,chlorophyll,protein,superoxide dismutase activities,peroxidase activities and isoperoxidases were measured.【Result】Heavy metals significantly inhibited the growth of roots and leaves,made the soluble protein content of leaves and roots rise sharply,decreased the SOD activities of leaves.Cu2+ had no significant effect on the SOD activity of root,but Cd2+ and Hg2+ significantly reduced the SOD activity of root.Cu2+ increased the POD activity of root.Low concentration of Cd2+ and Hg2+ increased the POD activity of root,but medium concentration and high concentration of Cd2+ and Hg2+ decreased the POD activity of root.The influence of heavy metal on maize was as follows:on root,Cu2+ had no obvious effect;Cd2+ weakened the Rb1 and the Rb2;Hg2+ restrained the Rb1,enhanced the Rb2,and induced the Rb3 at low concentration;on leave,the higher the concentration of heavy metal was,the more Lb5 was expressed;Cu2+ and Cd2+ didn’t affect the types of isoperoxidases,however,Hg2+ fully suppressed the expression of Lb6.【Conclusion】The effect on the activity of superoxide dismutase and peroxidase of heavy metal depends on heavy metal types,concentrations and tissue types.Both necessary element and nonessential element have obvious influence on isoperoxidases’ expressing,but the mechanism is different.Moreover,the action mechanism of different nonessential elements shows apparent differences.