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作 者 ：王振南,陆姣云,赵玉信,罗崇亮,张 曦,杨惠敏*

期 刊 ：西北植物学报 2013年 12期 页码：2492~2498

关键词：物质积累；茬次；环境适应性；生长阶段；陇东苜蓿；光合特性；

Keywords:biomass accumulation, cut, environmental adaptability, growth stage, Medicago sativa L.cv.Longdong, photosynthesis,

摘 要 ：气体交换和荧光特性是植物环境适应的重要表征,会随植物生长而变化,但其变化规律尚不明确。以多年生豆科牧草陇东苜蓿为材料,测定了其3茬不同生育时期气体交换和叶绿素荧光、叶绿素组分含量、蔗糖合成酶和蔗糖磷酸合成酶活性等参数,从时间变异性角度探讨紫花苜蓿环境适应的光合作用机制。结果表明:（1）随陇东苜蓿的生长,其地上部分和叶干重在各茬内都呈增加趋势,而平均日増干重在前两茬内呈增加趋势,在第3茬内呈先上升后下降的趋势,符合“S”型生长规律。（2）叶片净光合速率、气孔导度和羧化效率在各茬内呈降低的趋势,而叶片胞间CO₂浓度则相反,水分利用效率和气孔限制值在第一茬内呈下降的趋势而在第二茬和第三茬内则呈增加的趋势。（3）叶片蔗糖合成酶和蔗糖磷酸合成酶活性均不随陇东苜蓿生长而发生明显变化,蔗糖含量则呈增加的趋势。（4）同一茬内,叶片叶绿素含量随陇东苜蓿的生长而呈增加趋势,叶绿素荧光参数只在第一茬初期有较明显的变化,后两茬内变化不明显。研究发现,为适应不同生育时期的环境条件,紫花苜蓿叶片气体交换和叶绿素荧光特性表现出时间变异性,且二者间存在差异。

Abstract:Photosynthetical gas exchange and chlorophyll fluorescence are important measures of plant adaptation to environments.However,their temporal variation during plant growth is still not clear.Our objective is to elucidate how they change as the plant grows.A local lucerne (Medicago sativa L.cv.Longdong) was chosen and gas exchange,chlorophyll fluorescence,chlorophyll content,sucrose content and related synthase activities,and biomass were measured at different growth stages of each cut in a glass house experiment.(1)Dry matter of the aboveground part and leaf increased as lucerne grew in each cut,while the average dry matter increment per day increased in the anterior two cuts and first increased and then decreased in the third cut,appearing some “S” type of growth.(2)Net photosynthetic rate (P_n),stomatal conductance and carboxylation efficiency decreased as lucerne grew in each cut,while intercellular CO₂ concentration did oppositely,and water use efficiency and stomata limitation to P_n decreased in the first cut but increased in the latter two cuts.(3)Sucrose content increased,while the activities of sucrose synthase and sucrose phosphate synthase did not change significantly.(4)Chlorophyll contents,including chlorophyll a,b and both,increased as lucerne grew in each cut.Chlorophyll fluorescence changed obviously only at the beginning in the first cut,and maintained stable in the rest cuts.Conclusively,lucerne showed obvious but different temporal variations in gas exchange and chlorophyll fluorescence in response to the environmental factors during stand growth.

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