青菜幼苗体内几种保护酶的活性对Pb、Cd、Cr胁迫的反应研究

Response of some protective enzymes in Brassica chinensis seedlings to Pb^(2+), Cd^(2+) and Cr^(6+) stresses

1 引言自从McCord在1969年第一次从牛红血细胞中发现超氧化物歧化酶(SOD)并且证明其功能是清除超氧化物以后,研究者们在植物细胞中也发现了这种酶,并且证明具有同样的功能.后来又发现植物细胞通过多种途径产生活性氧自由基,同时细胞也存在清除这些自由基的多种途径[5],两者形成平衡体系.但是,许多逆境因子如寒冷、干旱、干燥、水淹、重金属Al等都能影响植物体内活性氧代谢系统的平衡,产生大量的氧自由基。

Seedlings of Brassica chinensis were cultured in 1/2 Hoagland solution for seven days before they were treated with Pb2+, Cd2+ and Cr6+. The activities of their superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) responded to the increasing concentrations of the metals, and the responsive characters varied with different metals and different durations of metal treatments. CAT activity decreased with the increase of metal concentrations, and the order of its sensitivity to the three metals was Cd2 +>Cr6+> Pb2+ . SOD activity followed a rise-fall pattern along metal concentration gradient, but its sensitivity decreased with the duration of metal treatment. There was an obvious difference in POD activity to different metals, only when the treatment was proceeded for a period of time.