摘要:
细胞器结构是生物细胞功能的基础，而重金属会对细胞器结构产生毒害效应，进而破坏生物的组织器官完整性及生理代谢功能，汞对生物结皮细胞器超微结构的影响尚未见报道。为探究汞胁迫对齿肋赤藓生物结皮叶肉细胞超微结构的影响，将叶肉细胞暴露于不同浓度的汞溶液中(0、10、20、30、40、50和60 mmol·L-1)，连续培养7 d，采用透射电镜技术观察叶肉细胞的变化。与对照组相比，汞浓度在20～60 mmol·L-1时，齿肋赤藓生物结皮的细胞器超微结构随汞浓度增加逐渐发生变化，细胞壁逐渐模糊，出现质壁分离现象，液泡出现一定的空泡化，叶绿体膜破损，类囊体、基粒及基质片层消失，细胞核解体及核仁消失。综上所述，齿肋赤藓生物结皮在低汞浓度时可维持有机体免受毒害，表明齿肋赤藓生物结皮有一定的重金属胁迫耐性，但超过阈值(20 mmol·L-1)时，出现汞胁迫伤害，且随汞浓度增加，胁迫毒害效应加剧。本研究结果可为干旱区非维管植物(齿肋赤藓)适应重金属胁迫环境理论及抗性物种培养提供参考。
Abstract:
Organelle structures are the basis of cell function, playing an essential role in the integrity of tissues and organs as well as the physiological and biochemical functions of the organism. Transmission electron microscopy was used to observe the toxic effects of mercury on the ultrastructure of mesophyll cells of Syntrichia caninervis. The results are as follows: (1) As the concentration of mercury reaching 20 mmol·L-1, the ultrastructure of the organelles of Syntrichia caninervis changed slightly, regarded as the critical concentration of the stress; (2) When the concentration of mercury was between 30～40 mmol·L-1, the color of the cell wall deepened, and its structure blurred partially, showing signs of plasmolysis; vacuoles appeared to be vacuolated; chloroplast was obviously swollen, and its membrane was wrinkled and deformed; while the basal granules and the matrix lamella were blurred, the nucleus was blurred severely; (3) While the concentration of mercury arrived at 50～60 mmol·L-1, the cell wall plasmolyed significantly; chloroplast swelled severly, with its membrane destructed; its thylakoids, basal granules and matrix sheets disappeared completely; nucleus disintegrated and nucleoli vanished. It is indicated that Syntrichia caninervis can protect the organism from damage at low concentrations of mercury (less than 20 mmol·L-1), suggesting that Syntrichia caninervis has the ability to resist metal stress to some degree. However, if the concentration of mercury exceeds the threshold of 20 mmol·L-1, mercury stress damage will occur, and with the increase of mercury concentration, the stress poisoning effect is intensified.
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