目的:研究艾叶纯露的抗氧化作用和艾叶挥发油的抗菌作用,为艾叶的高效利用提供理论依据.方法:采用羟自由基清除率的测定方法研究艾叶纯露的抗氧化性,滤纸片法测定艾叶挥发油的抗菌作用.结果:艾叶纯露对于羟自由基有明显的清除作用,随羞艾叶纯露浓度的升高,羟自由基清除作用增强,有较好的抗氧化作用.艾叶挥发油对五种细菌均有一定的抗菌作用,对金黄色葡萄球菌的抗菌效果最好,其次是大肠杆菌,白色葡萄球菌,浆黄色葡萄球菌,而对于副乙伤寒乙杆菌抑菌作用较弱.结论:艾叶纯露具有清除羟自由基的能力,有较好的体外抗氧化作用;艾叶挥发油具有较好的体外抗菌作用.

以小麦（Triticum aestivum）矮抗58为材料,采用0.1mmol/L的外源水杨酸（SA）处理小麦叶片,以清水为对照,通过Western blotting蛋白质印记技术和叶绿素荧光分析,研究了高温强光胁迫（38℃和1600μmol m-2s-1）对小麦叶绿体Deg5蛋白酶、D1蛋白和叶绿素荧光参数的影响及SA的调节作用。结果表明,高温强光胁迫导致小麦叶绿体Deg5蛋白酶、D1蛋白含量和PSⅡ最大光能转化效率（Fv/Fm）降低,原初荧光（Fo）升高。和对照相比,外源SA处理可维持较高的Deg5蛋白酶、D1蛋白、Fv/Fm水平和较低的Fo。说明外源水杨酸可减轻高温强光对Deg5蛋白酶和D1蛋白的损伤,维持较强的PSⅡ功能。

Wheat is one of the most important food crops in China and its production is crucial to ensure national food security.In the north of China,wheat plants often suffer from heat and high irradiation stress during grain-filling stage,leading to damage in photosynthetic apparatus and reduction of yield.Especially,the reaction center in photosystem Ⅱ(PS Ⅱ) is prone to various environmental stresses,and the extent of damage depends on the balance between injury and repair.The repair of PSⅡ needs fast turnover of D1 protein,which is the key component of PSⅡ.During the repair of PSⅡ,damaged D1 protein must be degraded and subsequently replaced by new copies quickly.It is well known that Deg1 protease plays an important role in cleavage of damaged D1 protein.However,the dynamic change in Deg1 protease under heat and high light stress is still largely unclear.In this study,we used wheat cultivar "Aikang 58" to determine the effects of heat and high light stress on Deg1 protease and D1 protein levels and PSⅡ performance and further the regulation role of salicylic acid(SA) in the repair of PSⅡ.Wheat leaves of grain-filling stage were pretreated with 0.3 mmol/L SA and distilled water(as control) respectively and then subjected to three temperature and irradiation treatments: moderate temperature and irradiation(25℃,600 μmol m-2 s-1,MTI) for 2h,high temperature and irradiation(38℃,1600 μ mol m-2 s-1,HTI) for 2h,and HTI following by 3h MTI.Fluorescence parameters were measured using a chlorophyll fluorometer.The levels of Deg1 protease and D1 protein were analyzed by western-blotting analysis.The results showed that HTI treatment resulted in degradation of Deg1 protease and D1 protein and reversible damage to PSⅡ function.Compared with control,pretreatment with SA not only retarded degradation of Deg1 protease and D1 protein,maintained higher potential photochemical efficiency(Fv/Fm),actual photochemical efficiency(ΦPSⅡ),electron transfer rate(ETR) of PSⅡ and net photosynthetic rate(Pn) of wheat leaves under HTI,but also accelerated the recovery under non stress condition.It suggests that SA could protect photosynthetic apparatus of wheat against combined stress of heat and high irradiation to some extent via maintaining the turnover of D1 protein.

The summer maize cultivars Zhengdan 958 and Xundan 20 were selected to study the effects of planting densities on the photosynthesis properties of canopy with four density treatments.The results showed that LAI of Zhengdan 958 increased with the increase of planting density.The light transmission of canopy was significantly higher in upper layer than in the lower layer.The chlorophyll content increased with the increase of planting density at first,then decreased when the density exceeded82 500 plants/ha.Fv/Fm and qP were higher in the third leaf above ear than those in the ear leaf and the third leaf below ear,but NPQ was converse.With the advancing of development stages,the stem diameter increased first and then decreased,reaching the maximum in silking stage.The stem diameter of Xundan 20 decreased with the increase of density.The highest yield was obtained under the density of 90 000 plants/ha for Zhengdan 958 and 82 500 plants/ha for Xundan 20,and the highest yield of two cultivars were 12 166.070,9 705.709 kg/ha,respectively.