【作者】 马广岳；

【导师】 施国新；

【作者基本信息】 南京师范大学 ， 植物学， 2004， 硕士

【摘要】 本文通过模拟不同浓度梯度的重金属Cd²⁺、Cu²⁺、Cr³⁺、Cr⁶⁺和Zn²⁺污染环境，利用生理生化测定、扫描电镜、透射电镜、气相色谱及激光共聚焦等实验手段，研究了四种金属离子对不同生态型的水生植物的毒害影响，初步探索了Ce对浮萍Cu害的缓解效应和La、Zn及其交互作用对浮萍活性氧清除系统影响。结果表明：Cd²⁺、Cu²⁺、Cr³⁺、Cr⁶⁺、Zn²⁺均对不同生态型的水生植物的光合作用、保护酶系统、物质代谢系统、细胞超微结构等有破坏作用。在重金属离子的作用下，叶绿素、可溶性蛋白含量下降，超氧阴离子产生速率加快，细胞的防御系统被启动，使得植物体内的活性氧清除系统中的保护酶系统的活性应急性提高，抗氧化物质的含量应急性增加，这些反应对植物均起到了一定的保护作用。但随着毒害的加重，当超出细胞的保护限度，将会导致保护酶活性降低，抗氧化物质含量下降，而丙二醛（MDA）等膜脂过氧化产物大量产生，膜透性增加，使植物体受害加剧。电镜观察显示，水生植物受重金属毒害后，叶绿体中的类囊体和线粒体中的脊突膨胀或呈囊泡状，直至解体；细胞核变形，核膜破裂，核质外流，染色质凝集。生理指标的变化与超微结构的破坏是一致的，且与离子浓度之间呈现出明显的剂量效应关系。 同属不同种的浮萍对Cu胁迫的反应有差异：抗氧化酶活性强的浮萍其叶绿素、可溶性蛋白含量下降幅度和超氧阴离子的产生速率要低于抗氧化活性弱的稀脉浮萍，这进一步验证了活性氧理论。而同种植物的根和叶对重金属的反应也有差异。虽然根的抗氧化酶活性较叶强，但受到的毒害却重于叶，所以同一植物不同器官的抗性不能仅以抗氧化酶的强弱为标准，还要考虑不同器官的抗性机制是否有差异。水生植物对具不同价态的同一重金属离子的反应也有差异，价态及存在形态的差异决定了对植物的毒性的不同，这也从生理指标上得到具体的反映。 稀土对重金属胁迫有明显的缓解作用，表现在：它能抑制Cu²⁺、Zn²⁺毒害下浮萍抗氧化酶活性和抗氧化物质的的降低，提高活性氧清除系统的清除能力，抑制活性氧的产生，从而减少了膜脂过氧化产物的生成。 稀土本身对植物也有一定的毒害作用，但当一定浓度的镧加入到Zn溶液里后，水生植物受到的毒害程度却比任何一种单施时弱。出现这种现象可能与La、中文摘要Zn之间具有交互缓解作用有关。 钙作为植物体内重要的第二信使，在植物体的发育以及对环境的反应和适应中起着重要的作用。运用焦锑酸钾沉淀法发现，单一Cu处理的慈姑根细胞质中的C扩+浓度要比复合处理的普遍高，而复合处理组根细胞内的c扩十分布与对照无显著的差异，只是有较少的细胞中的焦锑酸钙沉淀颗粒比对照多。Ce的加入可能通过提高c扩气ATPase的活性，使胞内c扩十的稳态平衡得以维持，进而使C扩十与CAM正常结合而行使信使作用，诱导植物通过提高抗氧化酶的活性（SOD，P OD等）和抗氧化物质（AsA、GSH、Pro）的含量等一系列的反应以提高植物的抗性。更多还原

【Abstract】 By imitating different concentration of Cd2+ Cu2+ Cr3+ Cr6+and Zn2+polluted water environment,we mainly studied their toxic effects on aquatic piants by means of measurement of physiologicai indexes and electron microscopy observation as well as the relieving to Cu2+ injury of antioxidase enzyme system in Lemna minor L. and Vallisneria asiatica Miki in this paper by throwing Ce.the experimental results showed that Cd2+ Cu2+ Cr3+ Cr6+ and Zn2+ might injure photosynthetic systems, protective enzyme system, substance metabolism systems and cell ultrastructure of the plant.The four species of ions could increase reactive oxygen species (ROS)content of the plant.At the same time,the protective systems (antioxidant enzyme system mainly)reacted on it.The activities of superoxide dismutase (SOD),peroxidase(POD)and catalase (CAT)were induced in high level to eliminate and resolve ROS in order to maintain stability of member system, With more serious damages,the defenses of cells could not protect cells,So the activities of protective enzyme decreased, malondialdehyde (MDA)content increased,and integrality of cell member was destroyed.The more injuries of the heavy metals to the plant were brought under this situation.Ultrastructural observation showed that there was a great deal of damage by Cd2+ pollution:The thylakoids of chloroplast and cristae of mitochondria became swollen or vesiculate and disintegrated finally;The nucleus were distorted and the nuclear membrance was disrupted.The chromatin was polymerized and concentrated and the nucleolus was dispersed.The changes of some biochemical and physiological indexes were in accordance with the destroy of cell ultrastructure and all indexes showed an evident correlation between the dose and effect.There was some difference between Lemna minor L. which is in the same category but different genus to stress caused by Cu . The more stronger the variety’ antioxidant enzyme action,the more lower the decreasing degree ofchlorophyll ,soluble protein content and O2- generation rate. This also validated exaction of reactive oxygen system theory. And there was difference between root and leave which is in the same category to stress caused by the same heavy metal ion.Although the antioxidant enzyme action of root was more stronger than that of leaf, the poisonous degree of root was more serious than that of leaf. So the comparison of resistance of different organ of the same plant didn’t be judged only by antioxidant enzyme action.So the difference of the resist mechanism of different organ should be considered. The aquatic plants also had some different reaction to the same heavy metal which is in different valence condition. Valence condition and existent morphology influenced the poison to plant. This was also reflected from some physiological index.Rare earth has obvious relieving effect to heavy metal stress.That was represented as follows:It could slow reduction of antioxidant enzyme action and antioxidant substance content,so improving ROS scavenging abilities and chastening production of ROS,reducing membrance lipid peroxidation substance.Although La itself had certain toxic effect to plant, the toxicity of La+Zn to plant is smaller than that of another when La was threw into Zn solution. This phenomenon may be connected with their alternate relieving action.Calcium played an important role in plant’ growth as well as response and adaptation to environment. Ca2+concentration in singular Cu treatment group was usually higher than that in composite group by using localization of Ca2+ antimonite precipitation technique,.And distributing of Ca2+ in composite group.has no obvious difference from control group. Only having high condensation in minor cells.Ce might improve the activity of Ca2+-ATPase,which sustain equilibrium of Ca2+ and combine with CAM to exert messager action and to induce plant to improve resistance by enhancing antioxidant enzyme action (SOD,POD etal) and antioxidant substance content (AsA, GSH, Pro) .更多还原