汞、镉、铜污染对鱼草细胞膜系统的毒害作用

通过生理生化反应测定、激光共聚焦扫描显微镜及透射电镜观察等实验手段，研究了汞（Hg²⁺）、镉（Cd²⁺）、铜（Cu2⁺）对高等水生植物鱼草(Cabomba caroliniana A. Gray)细胞膜系统的毒害作用.结果表明：在3种重金属离子作用下，鱼草叶细胞活性氧（ROS）与丙二醛（MDA）含量上升，保护酶系统活性紊乱，膜脂过氧化程度加剧；质膜受损，膜透性增加，质壁分离；叶绿体膨胀至解体，类囊体膜上的光合色素光激发过程受阻，平均自发荧光强度降低；线粒体嵴突膨胀、减少，膜破损；核膜破裂.Hg²⁺、Cd²⁺、Cu²⁺对鱼草细胞膜系统的影响存在着一定的剂量效应关系.膜系统的稳定性在植物抗重金属胁迫的过程中起着关键性的作用.鱼草对Hg²⁺污染较为敏感，致死浓度为0.3～0.5 mg·L^-1，而对Cd²⁺、Cu²⁺具有较强的抗性，可用作生物防治中的抗性植物.

Toxic effects of Hg2+, Cd2+ and Cu2+ on cell membrane system of Cabomba caroliniana A. Gray

By the observation with electron- and confocal laser scanning microscopy and the determination of physiological and biochemical reactions, the toxic effects of Hg2+, Cd2+ and Cu2+ on the cell membrane system of Cabomba caroliniana A. Gray were investigated. The results showed that under the actions of the three heavy metal ions, the contents of reactive oxygen species (ROS) and malondialdehyde (MDA) in C. caroliniana leaf cells increased, activities of protective enzymes were in disorder, and lipid peroxidation happened. The cell membrane was damaged, membrane permeability increased, and plasmolysis occurred. Meanwhile, the chloroplast swelled or even disintegrated. The excitement of photosynthetic pigments on thylakoids membrane by light was inhibited, and the auto-fluoresent intensity was decreased. The cristae of mitochondria swelled and decreased, mitochondria membrane was damaged, and nuclear membrane was broken. The effects of Hg2+, Cd2+ and Cu2+ on the cell membrane system of C. caroliniana showed a definite dose-effect correlation, and the stability of membrane system played a key role in the resistance of C. caroliniana to the toxic effects of heavy metals. C. caroliniana was sensitive to Hg2+, and the lethal concentration of Hg2+ was ranged from 0.3 to 0.5 mg L(-1). C. caroliniana had relatively higher endurance to Cd2+ and Cu2+, and could be used as the resistant plant for biological control.