低温对两种沙冬青幼苗光合生理指标的影响

以濒危植物新疆沙冬青和蒙古沙冬青幼苗为材料，研究了低温对叶片叶绿素荧光参数、叶绿体色素含量、叶绿体中丙二醛（MDA）含量及超氰化物歧化酶（SOD）、过氧化物酶（POD）、抗坏血酸过氧化物酶（APX）活性等光合生理指标的影响．结果表明：0℃、-5℃和-15℃低温处理后，两种沙冬青的初始荧光（Fo）、Chla／Chlb比值和Car含量随温度降低呈上升趋势，最大光化学效率（Fv／Fm）、Chla和Chlb含量随温度降低呈下降趋势；MDA含量、SOD和POD活性均随温度降低旱上升趋势，0℃、-5℃处理48h后，两者的APX活性升高，-15℃处理48h后，两者的APX活性与-5℃时相比活性下降．这说明低温对两种沙冬青的光化学效率都有一定的影响，其光合机构通过增加过剩光能的热耗散来抵御低温对比合系统的破坏，另外较高的抗氧化酶活性保证了两种沙冬青在低温下能够维持一定的光合作用，保护光合系统免遭活性氧的损伤．比较分析两种沙冬青幼苗光合生理受低温的影响，初步说明蒙古沙冬青比新疆沙冬青对低温的适应能力更强．

Impacts of Low Temperature on Photosynthesis Physiology of Ammopiptanthus manus (Leguminosae)and Ammopiptanthus mongolicus Seedlings

By simultaneously analyzing chlorophyll fluorescence parameters, chloroplast plgment contents and detecting contents of malondialdehyde（MDA）,activities of superoxide dismutase （SOD） , peroxidase（POD）and ascorbate peroxidase（APX） in chloroplast,the effects of low temperature on Photosynthesis Physiology in leaves of Ammopiptanthus nanus and Ammopiptanthus mongolicus Seedlings was investigated. The results showed that the F0, Chla/Chlb value and carotenoids contents increased, Fv/Fm, Chlorophyll a, Chlorophyll b contents declined after exposed to 0℃,-5℃ and -15℃ for 48h, and MDA content, SOD, POD activity rised, APX activity increased after 0℃, -5℃ treatment, and APX activity droped after exposed to -15~C for 48h.It showed that low temperature have a certain impacts on the photosynthetic efficiency of the two Ammopiptanthus, and Their photosynthetic apparatus by increasing the thermal dissipation of excess light energy to resist the low-temperature damage to the photosynthetic system, and higher activity of antioxidant enzymes to ensure that the two Ammopiptanthus could be able to maintain a certain de- gree of photosynthesis, protect the photosynthetic apparatus to avoid oxidative damage at low temperature. Ammopiptanthus mongolicus had stronger adaptability to low temperature than Ammopiptanthus nanus.