多胺对镉胁迫下平邑甜茶根系损伤和NO生成的影响

Effects of Polyamines on Root Damage and Nitric Oxide Production in Malus hupehensis var.pingyiensis Under Cadmium Stress

以一年生平邑甜茶幼苗为试材,在水培条件下,通过根施硫酸镉、精胺、亚精胺,研究48 h后平邑甜茶根系内源游离态多胺含量、多胺氧化酶活性、过氧化氢含量、细胞损伤和线粒体特性的变化,并结合多胺合成抑制剂,测定一氧化氮生成量、一氧化氮合酶和硝酸还原酶活性的变化,以期揭示外源精胺和亚精胺缓解平邑甜茶根系镉损伤的生理机制,探讨多胺对一氧化氮生成的调控。结果表明:镉胁迫导致过氧化氢含量增加,线粒体膜透性增大、膜电位降低、细胞色素c/a降低,一氧化氮生成量增加,根系细胞损伤严重。镉胁迫下多胺代谢异常,精胺和亚精胺含量明显降低,腐胺含量显著增加,(亚精胺+精胺)/腐胺显著降低,多胺氧化酶活性显著升高。外源添加精胺和亚精胺可降低镉胁迫下多胺氧化酶活性、过氧化氢含量和一氧化氮合酶活性、硝酸还原酶活性、一氧化氮生成量,稳定线粒体膜透性、提高膜电位和细胞色素c/a,恢复(亚精胺+精胺)/腐胺比值。而外施多胺合成抑制剂明显提高了一氧化氮合酶活性、硝酸还原酶活性和一氧化氮生成量。综上所述,外源添加精胺或亚精胺通过抑制一氧化氮生成,维护根系线粒体功能稳定,明显减弱了镉胁迫下根系细胞损伤程度,提高了植株的耐镉性。

Taking one-year-old Malus hupehensis Rehd.seedlings grown in nutrient solution as test materials,the endogenous free polyamines content,polyamine oxidase(PAO)activity,hydrogen peroxide(H_(2)O_(2))content,cell damage,and mitochondria characteristics were studied after 48 hours by applying cadmium sulfate,spermine,and spermidine to the nutrient solution.In addition,seedlings were treated with polyamine synthesis inhibitors,and then the changes of nitric oxide(NO)production,nitric oxide synthase(NOS)activities,and nitrate reductase(NR)activities were measured,in order to reveal the physiological mechanism of exogenous spermine and spermidine in alleviating cadmium stress of Malus hupehensis Rehd.var.pinyiensis Jiang,and to explore the regulation of polyamines(PAs)on nitric oxide(NO)metabolism.The results showed that the H_(2)O_(2) content was increased significantly,while the mitochondrial membrane permeability was increased,the membrane potential and cytochrome c/a were decreased,the NO production was increased and eventually root cells were severely damaged under cadmium stress.The metabolism of polyamines was abnormal,the spermine(Spm)and spermidine(Spd)contents were significantly reduced,the putrescine(Put)content was significantly increased,the(Spd+Spm)/Put ratio was significantly reduced,and the PAO activity was significantly increased.The PAO activity,H_(2)O_(2) content,NOS activity,NR activity,and NO production were reduced by exogenous application of Spm and Spd under cadmium stress,which stabilized mitochondrial membrane permeability,increased membrane potential and cytochrome c/a,rescored(Spd+Spm)/Put ratio.The NOS,NR activity and NO production were increased significantly by exogenous application of polyamine synthesis inhibitors under cadmium stress.The above results showed that the exogenous addition of spermine or spermidine can maintain the stable function of root mitochondria by inhibiting the production of NO,obviously reducing the damage of root cells under cadmium stress,and improving the cadmium tolerance of plants.