互花米草（Spartina alterniflora L.）对重金属Cd胁迫的生理响应

以盐生植物互花米草幼苗为试材,研究了其抗氧化酶体系活性（超氧化物歧化酶,SOD;过氧化物酶,POX;过氧化氢酶,CAT）对不同浓度Cd胁迫的响应变化,并利用非变性聚丙烯酰胺凝胶电泳对SOD及CAT进行了同工酶分析.结果表明,抗氧化酶活性与Cd处理浓度关系密切,0.1-2.0 mmol/L Cd浓度范围内SOD活性显著增加;POX活性在Cd浓度较低时相对稳定,高浓度下降低显著;而CAT酶活性在Cd浓度较高时被诱导升高.SOD同工酶谱受到Cd胁迫的显著影响,4.0 mmol/L处理下酶活性明显降低.CAT同工酶活性呈现先降后升的变化趋势,与酶总活性的检测结果基本一致.表明互花米草对重金属Cd具有一定程度的耐受性,可以通过提高酶促过氧化体系活性来应答Cd导致的氧化胁迫;而Cd浓度超过一定阈值后（4.0 mmol/L）,互花米草即遭受较严重的不可逆损伤.

Physiological Response of Spartina alterniflora L. to Heavy Metal Cd Stress

The response of the antioxidant defense system in Spartina alterniflora L.seedlings subjected to different concentration of Cd is investigated,superoxide dimutase（SOD） and catalase（CAT） isoenzymes are analyzed with polyacrylamide gel electrophoresis.The results show that the activity of the antioxidant enzyme system is closely related to the concentration of Cd.The activity of SOD in seedlings increases significantly at concentrations of 0.1~2 mmol/L.The activity of peroxidase（POX） is stable under stress of lower Cd concentration, but decreases obviously at higher Cd concentration. The activity of CAT inductively increases when the plants are exposed to higher concentration of Cd. SOD isoenzyme spectrum is apparently influenced by Cd stress and the activities of some enzymes decrease significantly. The activity of CAT increases after an initial drop, which is generally consistent with the total enzyme activity. These data suggest that S. alterniflora shows tolerance to Cd stress to some extent and can positively respond to Cd induced oxidative stress by enhancing the activity of antioxidant defense system. However, when Cd concentration exceeds a certain limit, S. alterniflora suffers from serious and irreversible damage.