Abstract:

In this paper, both leaf photosynthetic parameters and chloroplast ultrastructure were measured for two types of alfalfa (ordinary alfalfa(Medicago sativa) and multifoliate alfalfa) using li-6400 portable photosynthesis system and transmission electron microscopy in order to provide the theory basis for discussing the photosynthetic characteristics of multifoliate alfalfa and the application of breeding practice in ordinary alfalfa and multifoliate alfalfa. The values of P_n, G_s, C_i, T_r were higher in Multifoliate alfalfa than in ordinary alfalfa, whereas the values of L_s and WUE were lower in Multifoliate Alfalfa than in ordinary alfalfa. The average value of Multifoliate alfalfa was 25.79 μmol·m^-2·s^-1, and the Photosynthetic efficiency was higher in Multifoliate Alfalfa than in ordinary alfalfa. The net photosynthetic efficiencies of different dicotyledon types were ordered as 5 leaflets > 4 leaflets >3 leaflets> 6 leaflets>7 leaflets> 8 leaflets> 9 leaflets. These results of transmission electron microscope indicated that the mesophyll of 5 leaflets had the most number of chloroplast in each cell and the most number of granulum basale in chloroplast, large starch grain, and thick grana lamella accumulation. But both number and size of osmiophilic body were small. At the base of 5 leaflets, the numbers of chloroplast and grana decreased, he number and volume of starch granule decreased when the number of leaflets increased. Photosynthetic efficiency of multifoliate alfalfa was significantly larger than the ordinary alfalfa; the 5 leaflets had the maximum net photosynthetic efficiency.

Key words: Mutlifoliate alfalfa, Ordinary alfalfa, Photosynthetic Characteristics, Chloroplast ultrastructure

摘要：

以多叶苜蓿、普通三叶型苜蓿(Medicago sativa)为研究对象,利用LI-6400 便携式光合作用测定仪和透射电镜考察2类苜蓿叶片光合参数及叶绿体超微结构,比较分析苜蓿不同复叶类型的光合特性差异,探讨多叶型苜蓿的光合特性和在育种实践上的应用提供理论依据.结果表明:多叶型苜蓿的净光合速率(P_n)、气孔导度(G_s)、胞间CO₂浓度(C_i)、蒸腾速率(T_r)平均高于三叶型苜蓿,而气孔限制值(L_s)和叶片瞬时水分利用效率(WUE)平均低于三叶型苜蓿,多叶苜蓿的P_n 平均在25.79 μ mol·m^-2·s^-1左右,光合效率显著大于普通三叶型苜蓿.不同复叶叶型的苜蓿净光合效率的排列顺序是5叶型 >4叶型 >3叶型 >6叶型 >7叶型 >8叶型 >9叶型.5叶型复叶叶肉中每细胞的叶绿体数目最多,叶绿体中基粒多,基质浓厚,基粒片层堆积致密,嗜锇体数目较少、体积小,每叶绿体中的淀粉粒数目多而饱满.以5为基数叶片数目再增加时,叶绿体个数减少,基粒数目减少、基粒片层结构排列松散,嗜锇体的数目增加、体积变大,淀粉粒数目减小,体积变小.多叶苜蓿的光合效率显著大于普通三叶型苜蓿,多叶型复叶小叶数为5时,净光合效率最大.

关键词: 多叶苜蓿, 普通三叶型苜蓿, 光合特性, 叶绿体超微结构