Cd2+、Cr6+单一及其复合污染对少根紫萍生理生化特性的影响

为进一步了解重金属复合污染对水生植物产生毒害作用的机制，以少根紫萍叶片叶绿素含量、过氧化物酶活性（POD）、超氧化物歧化酶活性（SOD）、丙二醛（MDA）含量为指标，通过水培试验研究了少根紫萍在Cd2+、Cr6+污染胁迫4 d后的生理生化响应，并探讨了Cd2+、Cr6+单一与复合污染对少根紫萍叶片的毒性效应及其致毒机制。结果表明，单一Cd2+污染时，Cd2+处理对少根紫萍叶绿素含量有显著影响；随Cd2+处理浓度的增加，少根紫萍叶片SOD、POD酶活性表现为先增加后降低的趋势，而MDA含量都显著增加。Cr6+单一处理对少根紫萍各项指标的影响与Cd2+相似，但均小于Cd2+对少根紫萍的影响。Cd2+- Cr6+复合污染时，叶绿素含量变化趋势与单一处理相同，并低于相应的单一Cd2+、Cr6+处理，Cd2+- Cr6+复合污染处理时SOD、POD活性仍表现为先增加后下降趋势，但SOD、POD活性与镉单一处理时比较有降低现象， MDA含量仍随浓度的增加而增加，且高于单一处理，Cd2+- Cr6+复合污染的毒性效应高于单一污染的毒性，表现为协同作用。

Individual and Complex Effects of Cd2+;Cr6+ on the Physiological Characteristics of Spirodela oligorrhiza

To understand the toxicity mechanisms of mixed heavy metals on aquatic plant, ndicators of the content of chlorophyll, the activity of SOD, POD and the content of MDA in leaves of Spirodela oligorrhiza, hydroponic experiments were conducted in this study for exploring the biological responses of Spirodela oligorrhiza leaves to single and joint stress of Cadmium (Cd) and chromium (Cr⁶⁺ ). The results showed that single- Cd treatment had significant influences on the content of chlorophyll. With the increase of Cd concentrations, the content of chlorophyll decreased evidently, the stress content of chlorophyll is a sensitive index in response to the Cd-pollution. With the increase of Cd concentrations, the Spirodela oligorrhiza leaf SOD and POD activities appeared as an increasing- decreasing trend, and POD activities higher than CK. While the content of MDA increased persistently. Chromium (Cr⁶⁺) single treatment on Spirodela oligorrhiza indicators influence were similar to Cd, but were less than Cd. Under the Cd-Cr⁶⁺ combined stress, the content of chlorophyll decreased with increasing contentration, and less than the single-Cd stress. But there was no striking concentration difference of chlorophyll between groups of different Cr⁶⁺ concentrations in the same cadmium concentration, which showed that Cd²⁺ was dominant in the destruction of chlorophyll, the Spirodela oligorrhiza leaf SOD and POD activities appeared as an increasing- decreasing trend, but these enzyme activities decreased when compared with the single-Cd stress, and POD activities lesser than CK; the content of MDA increased with increasing concentration, and higher than the single-Cd stress, which suggested that the combined toxicity of Cd and Cr⁶⁺ was stronger than the single-Cd stress. The interaction of Cadmium and Chromium showed synergism action.