外源亚精胺对槐叶苹耐镉胁迫的增强效应

研究了不同浓度（0.05～1 mmol·L^-1）亚精胺（Spd）对镉（Cd）污染下槐叶苹（Salvinia natans）光合色素、可溶性蛋白、抗氧化系统以及矿质营养的影响，以探讨外源多胺在水生植物重金属胁迫适应中的作用机制.结果表明，外源Spd对槐叶苹的Cd污染胁迫具有明显的缓解作用：Spd延缓了槐叶苹叶片失绿症状，使叶绿素a/b和总叶绿素含量平均增加了18.97%和43.96%；外施Spd后可溶性蛋白含量平均提高了27.89%，SDS-PAGE电泳显示主要是增加了202.15、77.67、52.69、41.83 和25.35 kD的蛋白多肽表达量；外源Spd提高了抗氧化酶系统（SOD、POD、CAT）的活性和小分子保护物质［抗坏血酸（AsA）、谷胱甘肽（GSH）和类胡萝卜素（Car）］的含量，前者平均分别增加了12.44%、66.90%和51.23%，后者依次增加11.21%、17.60%和24.81%；外施Spd能更好地维持槐叶苹对P、K、Fe、Na、Mg、Zn和Mn等的平衡吸收（Ca除外）.综合分析发现，0.05～0.1 mmol·L^-1Spd缓解效果最好，与其改善光合作用、刺激蛋白表达、维持抗氧化系统高活性/含量和调节矿质营养平衡等多种生理过程有关.

Roles of exogenous spermidine in improving Salvinia natans tolerance towards cadmium stress.

In this study, the effects of foliar spraying different concentration (0.05-1 mmol·L^-1) spermidine (Spd) on the photosynthetic pigments, soluble protein content, antioxidant system, and mineral nutrition of Salvinia natans leaves under cadmium (Cd) stress were investigated, aimed to approach the action mechanisms of exogenous polyamines (PAs) in improving the adaptability of aquatic plants to heavy metals stress. The results showed that exogenous Spd could markedly mitigate the Cd stress to S. natans. It retarded the chlorosis, with chlorophyll a/b and total chlorophyll content increased by 18.97% and 43.96%, respectively, and increased the soluble protein content by 27.83%, compared with the control. SDS-PAGE revealed that the increase of soluble protein content was mainly of the expression increase of 5 polypeptides with apparent molecular weights 202.15, 77.67, 52.69, 41.83, and 25.35 kD. Exogenous Spd increased the activities of antioxidant enzymes SOD, POD and CAT and the contents of low molecular weight protective compounds AsA, GSH and Car, with an average increase of 12.44%, 66.90% and 51.23%, and 11.21%, 17.60% and 24.81%, respectively, and effectively maintained the balanced absorption of P, K, Fe, Na, Mg, Zn and Mn (with exception of Ca). In general, the optimum concentration range of exogenous Spd was 0.05-0.1 mmol·L^-1, which could enhance the resistance of S. natans to Cd toxicity by improving photosynthesis, stimulating the expression of protein, promoting the activity / content of antioxidant system, and keeping the balanced absorption of nutrient elements, etc.