利用组织培养技术培养水花生愈伤组织并以此为实验材料, 研究不同浓度(0, 0.2, 0.4, 0.8和1.6mmol/L)的Pb<sup>2+</sup>对水花生愈伤组织光合色素和可溶性蛋白含量、活性氧水平、抗氧化酶活性(CAT、SOD和POD)以及细胞亚显微结构产生的胁迫影响.结果表明, 随着Pb<sup>2+</sup>浓度的增加, 水花牛愈伤组织光合色素和可溶性蛋r1含最逐渐下降;超氧阴离子和过氧化氧含量呈上升趋势, 丙二醛含量表现为先升后降;超氧化物歧化酶、过氧化物酶活性同样呈现先升后降趋势, 过氧化氢酶活性则为逐渐下降的趋势;电镜观察发现, Pb<sup>2+</sup>胁迫对愈伤组织细胞的叶绿体、线粒体和细胞核造成不同程度的损伤, 0.8-1.6mmoL/L浓度对超微结构产生致命性的毒害.Pb<sup>2+</sup>破坏了水花生愈伤组织进行正常生长代谢所必需的生理和结构基础, 且打乱了代谢平衡, 最终导致愈伤组织的死亡。;Callus of Alternanthera philoxeroides was cultured by tissue culture technique, which was used as experimental material.This paper studied the toxic effects of Pb<sup>2+</sup> gradient concentrations (0, 0.2, 0.4, 0.8 and 1.6 mmol/L) on the contents of photosynthetic pigments and soluble protein, the level of active oxygen, activities of antioxidase(GAT, SOD and POD) and changes of ultrastructure in callus of Alternanthera philoxeroides.Tlie results indicated that, with the increasing of Pb<sup>2+</sup> concentration, the contents of photosynthetic pigments and soluble protein decreased gradually.The contents of O<sub>2</sub><sup>-</sup> and H<sub>2</sub>O<sub>2</sub> increased gradually, while the content of MDA increased at first and then decreased.TTie changes of SOD and POD activities were the same as MDA, but CAT activity decreased gradually.Transmission electron microscopy observation showed that the chloroplast, mitochondria and nucleus suffered serious damages under Pb<sup>2+</sup> stress, and the concentration of 0.8-1.6mmol/L generated the fateful poisons to ultrastructure.It was concluded that Pb<sup>2+</sup> stress induced not only destruction of physiological function and structural foundation of Alternanthera philoxeroides callus, but also the disorder of physiological metabolism, which led to the death of the callus at last.