【作者】 许丙军；

【导师】 施国新；

【作者基本信息】 南京师范大学 ， 植物学， 2007， 硕士

【摘要】 本文以高等沉水植物黑藻(Hydrilla verticillat Linn．)和菹草(Potamogeton crispus Linn)为实验材料，借助生理生化指标检测、超微结构观察和SDS-PAGE等实验手段，着重研究了重金属镉和汞胁迫下外源抗坏血酸对植物生理生化特性(叶绿素含量、可溶性蛋白、抗氧化物质含量、保护酶活性、活性氧生成速率等)、细胞超微结构和植物体内蛋白的影响。研究结果显示：水环境中的镉和汞污染对高等水生植物的光合系统、抗氧化物质(包括抗坏血酸和谷胱甘肽)、保护酶系统(包括SOD，POD，CAT，APX)、膜系统、物质代谢系统、细胞超微结构和蛋白质等均具有明显的毒害作用，植物体内源保护系统的防御功能在受到低浓度的重金属胁迫时可被诱导加强。抗坏血酸在一定程度上能够通过络合作用有效降低环境中的重金属离子浓度，减轻重金属对叶绿素的破坏，恢复光合系统功能；解除重金属离子对酶蛋白分子空间结构的破坏，提高保护酶的活性；把细胞内的有害的活性氧还原为无害的氧气和水，降低细胞中活性氧的水平，减轻其对膜脂的过氧化作用和对细胞超微结构的破坏。但是抗坏血酸对重金属毒害的缓解作用与其浓度密切相关，只有适宜浓度的抗坏血酸才会起到较好的缓解作用。过高浓度的抗坏血酸表现出一定的氧化性，与重金属具有协同胁迫作用。重金属对水生植物的毒害及抗坏血酸对重金属的缓解作用与其作用时间有一定的正相关性，作用时间越长，结果越显著。重金属还会抑制植物蛋白的合成或加速其分解，在SDS-PAGE图上表现为一些蛋白条带的消失。更多还原

【Abstract】 The relief effects of the ascorbic acid to the damage of aquatic plants Hydrilla verticillat Linn and Potamogeton crispus Linn. produced by heavy metal Cd²⁺ and Hg²⁺ were measured by physiological and biochemical indexes, observation of electron microscopy and SDS-PAGE. The results showed obvious damage to the photosynthetic systems, protective enzyme systems （including SOD, POD, CAT and APX）, antioxidant substance （AsA and GSH） content, substance metabolism systems, protein synthesis and cell ultrastructure of the plant by the heavy metal ion of cadmium and mercury. Resistance ability from endogenous protective enzyme systems and antioxidant substance content in the plants was enhanced by the inducement of heavy metal stress in restricted range but they were diminished by exorbitant concentration of heavy metal ion. The optimum concentration exogenous ascorbic acid can reduce concentration of Cd²⁺ and Hg²⁺ in cell, weaken the damage of Cd²⁺ and Hg²⁺ to the chlorophyll, improve or reduce the activities of antioxidant enzyme, depress the levels of reactive oxygen species (O₂^-.,H₂O₂ and·OH ), slack the oxidation of reactive oxygen species to the membrane and the damage of Cd²⁺ and Hg²⁺ to cell ultrastructure of the plant. But the relief effects of ascorbic acid to the damage of high aquatic plants under the stress of heavy metals is related to its concentration and exorbitant concentration of ascorbic acid acts on the plant cooperated with heavy metal. The damage of heavy metal and the relief of ascorbic acid are related with the time they had done. Several special protein bands in SDS-PAGE will dissolve affected by certain concentration heavy metal after ten days.更多还原