中文摘要：

【目的】探讨山定子根系线粒体功能对变温胁迫的响应机制及钙在此过程中的调节效应,为深入研究山定子根系适应温度逆境的生理机制奠定基础。【方法】以山定子幼苗为试材,进行变温处理（5℃→20℃→0℃）和CaCl2浇灌处理,测定根系线粒体膜通透性（MPT）、膜电位（？ψm）、超氧阴离子（）产生速率、线粒体细胞色素途径（CP）和交替途径（AP）、钙调素（CaM）含量、钙调磷酸酶（CaN）含量等指标的变化。【结果】大幅度变温导致山定子根系MPT不断增大,？ψm明显下降,产生速率持续升高,引起根系MDA含量不断增加。CaCl2处理使根系MPT处于较稳定的水平;明显提高降温阶段？ψm的水平;逐渐降低降温阶段的产生速率,使根系MDA含量始终稳定在较低水平。变温过程中根系CP活性和贡献率先下降后升高,AP活性则持续升高。CaCl2处理显著提高了20℃时CP和AP的活性,且AP活性和贡献率的变化趋势与CP互补。变温过程中根系CaM含量逐渐升高,CaN含量先下降后升高;而CaCl2处理后CaM含量先降低后升高,CaN含量则持续降低。【结论】大幅度变温抑制了山定子根系线粒体的功能,导致电子漏增加,膜脂过氧化程度加剧。外源钙通过稳定MPT,调节CP和AP活性等方式,有效降低了膜脂过氧化程度。在升温阶段,钙处理通过下调CaM和上调CaN来缓解温度胁迫;在降温阶段,钙处理则通过大幅度上调CaM和下调CaN来缓解温度胁迫。

英文摘要：

【Objective】 The responding mechanisms of mitochondrial function in Malus baccata Borkh. roots and the regulating role of calcium under changing temperature stress were studied, and the results would be a theoretical foundation for further study of the physiological mechanism of M. baccata Borkh. roots under such kind of temperature stress. 【Method】 The seedlings of M. baccata Borkh. were used as materials and treated with or without 2% CaCl2 solution, to investigate the characteristics of mitochondrial function, such as mitochondrial membrane permeability transition（MPT）, mitochondrial membrane potential（？ψm）, super oxygen anion（） generation rate, electron transfer pathway activity and contribution rate（cytochrome pathway, CP; alternative pathway, AP）, CaM content, and CaN content under violently changing temperature（5℃→20℃→0℃）. 【Result】 In control, MPT, generation rate and MDA content in M. baccata Borkh. roots obviously increased under violently changing temperature, ？ψm decreased at the same time. Compared with the control, CaCl2 treatment maintained the MPT at a relatively stable level during temperature changing. At the cooling stage, ？ψm significantly rose in CaCl2 treatment, meanwhile,the generation rate of gradually dropped. CaCl2 treatment kept MDA content at a relatively lower level. The activity and contribution rate of CP in control descended as temperature going up, and then increased with temperature going down, while AP activity kept in ascending under temperature treatment. Comparing with the control, CaCl2 remarkably increased the activities of CP and AP at 20℃. Moreover, the varying trends of AP activity and contribution rate were opposite to that of CP. In control, CaM content consistently increased, while CaN content decreased firstly and then increased. The content of CaM in CaCl2 treatment declined with temperature going up, and then increased as temperature going down, while CaN content steadily decreased.【Conclusion】Violently changin