铅、锌及其交互作用对鱼腥草(Houttuynia cordata)叶绿素含量及抗氧化酶系统的影响

采用营养液培养方法研究铅、锌及其交互作用对鱼腥草叶绿素含量及抗氧化酶系统的影响。实验结果显示，随着Pb浓度的增加，鱼腥草叶绿素含量逐渐降低但无显著变化。Zn在一定浓度下能提高鱼腥草叶绿素含量，而在高浓度Zn胁迫下，叶绿素含量急剧下降。鱼腥草叶片中SOD、POD和CAT3种酶活性都是随着Pb浓度的增加先上升后下降。随着Zn浓度的增加，SOD和CAT也是先上升后下降，POD则是逐渐上升。Pb—Zn交互作用增加了鱼腥草叶绿素含量，对SOD和POD活性具有抑制作用，对CAT活性影响不明显。同时研究结果还表明，单一Pb、Zn对鱼腥草叶绿素含量和抗氧化酶系统的影响大于Pb、Zn二者的共同作用，其中高浓度Zn对鱼腥草的伤害作用最大，而当溶液Pb处理浓度达到400mg／L时，鱼腥草仍能正常生长，说明鱼腥草具有较强的耐Pb能力。

Effect of Pb, Zn and their interactions on the chlorophyll content and antioxidant enzyme systems of Houttuynia cordata Thunb

Combination contamination of heavy metals is one of important soil contamination types.Phytoremediation is an effective approach for remediation of heavy metal contaminated soils.Nutrient solution culture was conducted to determine the effect of Pb and Zn contamination singly or in combination on the chlorophyll content and antioxidant enzyme activities of Houttuynia cordata Thunb.In single-heavy-metal systems,as Pb concentration varied from 5 to 400 mg/L in the nutrient solution,total chlorophyll content in leaves decreased linearly by up to 40%.As Zn concentration varied from 0 to 50 mg/L in the similar single-heavy-metal systems,the total chlorophyll content in leaves increased initially and then decreased as the Zn concentration in the culture increased beyond 10 mg/L.The activities of SOD,POD and CAT in those single heavy metal systems increased with Pb concentration initially to pass a maximum and declined as the Pb concentrations exceeded 100 mg/L.For the effects of Zn concentrations on the enzyme activities in similar systems,the same trends were found for SOD and CAT,but not for POD.Instead,the activity of POD increased with the Zn concentration in the entire tested range.In the dual heavy metal systems,Pb-Zn interactions increased chlorophyll content of Houttuynia cordata Thunb,restrained the activities of SOD and POD,but has no significant effect on the activity of CAT.These results indicated that the effects of single Pb and single Zn treatment on chlorophyll content and antioxidant enzyme systems were more severe than the combination effects of Pb-Zn interactions.In addition,the The high Zn concentration resulted in obvious damage of Houttuynia cordata Thunb.In contrast,Houttuynia cordata Thunb could normally grow with high Pb concentration up to 400mg/L.Therefore,Houttuynia cordata Thunb may have a high tolerance to Pb.