Abstract: The symptoms of the young leaves and ultrastructural changes of mesophyll cells of Brasenia schreberis winter buds when induced by poisoning of Hg^2+ pollution are reported in this paper. When winter buds were treated with a concentration of Hg 2+ in 5mg/L solution within 15 days, the leaves gradually lost their green color; glandular hairs contracted and twisted and mucilagenous material of the leaves was greatly reduced. The ultrastructural changes of the mesophyll cell showed the disappearance of Golgi apparatus and reduction of ribosomes with integration of mitochondria. Increasing of Hg2+ concentration on the same days of treatment as above, caused changes in the ultrastucture of the cells. It showed contraction of plasmalemma and snap of plasmodesmata, nucleolus broke into several parts, chloroplasts swelled and thylakoids disinte-grated. When winter buds were treated with concentration of Hg2+ increased to 15mg/L, the nucleus of cell broke down and cells died. According to our observation, the lethal concentration of Hg2+ to the winter bud of B. schreberi ranges from 2.5 to 5mg/L.

Key words: Brasenia schreberi

摘要： 报道了Hg2+污染对莼菜冬芽幼叶毒害引起的叶片 受害症状和叶肉细胞的超微结构变化。冬芽在Hg2+浓度5mg/L处理15 d时，叶片开始 褪绿，腺毛收缩扭曲，粘液减少，细胞中高尔基体消失，核糖体减少，线粒体出现解体。在 相同处理时间中，随着Hg2+浓度增加，细胞出现质膜收缩，胞间连丝断裂，核仁裂解 成多个小核仁，叶绿体膨胀，类囊体解体。在Hg2+浓度15mg/L时，细胞核解体，细胞 死亡。经观察，Hg2+对莼菜冬芽毒害的致死量在2.5～5mg/L。

关键词: 莼菜, 冬芽, Hg2+污染, 超微结构