汞、镉污染对黑藻叶细胞伤害的超微结构研究

Ultrastructural Study of Leaf Cells Damaged from Hg^(2+) and Cd^(2+) Pollution in Hydrilla verticillata

黑藻 (Hydrillaverticillata (L .f.)Royle)植株分别在Hg2 + 、Cd2 + 梯度浓度的污染水中培养 ,在培养的时间段中(Hg2 + 为 3d ,Cd2 + 为 6d) ,随着浓度的递增 ,叶片逐渐出现均匀褪绿症状。电镜观察发现 ,叶细胞遭受Hg2 + 、Cd2 + 毒害初期 ,高尔基体消失 ,内质网膨胀后解体 ,叶绿体中的类囊体和线粒体中的脊突膨胀或呈囊泡状 ,核中染色质凝集。随着叶细胞遭受毒害程度的加重 ,核糖体消失 ,染色质呈凝胶状态 ,核仁消失 ,核膜破裂 ,叶绿体和线粒体解体 ,质壁分离使胞间连丝拉断 ,细胞壁部分区域的壁物质松散游离 ,最后细胞死亡。结果表明 :Hg2 + 和Cd2 + 对细胞的膜结构和非膜结构都产生毒害作用 ,只是不同的结构对毒性的耐受性有一定的差异。Hg2 + 对黑藻的致死浓度为1～ 2mg/L ,Cd2 + 为 2～ 3mg/L。

Hydrilla verticillata (L. f.) Royle was cultivated in water medium polluted with Hg 2+ and Cd 2+ of different gradient concentrations for 3 days and 6 days respectively. Leaves of H. verticillata lost their green color gradually with the increasing pollutant concentration. Ultrastructural observation showed, at its early stage, dispersion of dictyosomes, disintegration after swelling of endoplasmic reticulum, swelling or vesiculation of thylakoids of chloroplasts and cristae of mitochondria and condensation of chromatin of nucleus. More serious damage was shown in the plant cells with heavier pollution, such as disappearance of ribosomes, agglutination of chromatin of nucleus, dispersion of nucleolus, disruption of nuclear membrane, disintegration of chloroplasts and mitochondria, collapse of plasmodesmata due to plasmolysis, focal dissociation of cell wall and eventually cells death. The results indicated that Hg 2+ and Cd 2+ might injure all the membranous and non_membranous structures of cells, though there existed different degrees of endurance of cell structures to the poison. The lethal concentration of Hg 2+ to cell of H. verticillata ranged from 1 to 2 mg/L, and that of Cd 2+ ranged from 2 to 3 mg/L.