| Alfalfa(Medicago Sativd) plays an important role in ecological construction and adjustment of agricultural structure, which is a major forage crop with well-behaving characteristics in the world. In order to enhance production of grasses by cutting down farming land areas, to enlarge areas of forage crops to satisfy requirements of agricultural structure adjustment, and to speed up development of animal husbandry, this paper, aiming at backward situation of alfalfa production in China, carried out systematically research on the characteristics of 31 alfalfa varieties from home and abroad by field observation, physiological measurement, mathematical simulation and comprehensive analysis, which included resistances, productive characteristics and quality. The research results provided background and basis for application of introduced varieties in China. Major conclusions are as follows:1. The research results of drought resistance of alfalfa varieties indicated that the percent of cell injured, water holding capability of in vitro leaves, and spread obstruction and transpiration of stomata in leaves were significantly different among alfalfa varieties under drought stress. Cluster analysis of 21 alfalfa varieties showed that the varieties with strong drought resistance included Abilene+z, Amerigraze40I+z, Apollosupreme, Meiguo-zajiao, Aggressor, Affinity+z, Ameristand201+z, the varieties with weak drought resistance included Abrriba, ,I3R supreme, Baofeng, Deguo-daye, Zhonglan No.l, the other were varieties with medium drought resistance.2. The cluster analysis on salt tolerance of 19 alfalfa varieties in germinating period showed that the varieties with strong salt tolerance included Archer,Ameriguard302+z,Lobo and Ameristand201+z, the varieties with medium salt tolerance included Zhongmu No.l.Alfagraze , Abilene+z , Abrriba and 13R supreme, the varieties with weak salt tolerance included Amerigraze40]+z,Meiguo-zajiao,Avalanche, Zhonglan No.l, Baofeng, Total+z, Aggressor, Apollosupreme,Innovator+z and Affinity+z.3. The drought, cold, heat and salt resistances of 17 alfalfa varieties were evaluated comprehensively, the results showed that varieties with strong drought and cold resistance included Ameristand20l+z, Aggressor, Abilene+z, Meiguo-zajiao, Apollosupreme, Alfagraze, Avalanche, Ameriguard302 and Total+z, which had better adaptability, and should be introduced and extended.4. Stepwise analysis on 10 biological characters of 31 alfalfa varieties indicated that the number of nodes, the number of branches, the width of leaves, and the weight per stem werethe major factors affecting alfalfa' yield, based on which, the optimal regression equation between yield and biological characters had been established. The biological characters of 31 alfalfa varieties were evaluated comprehensively, the results of cluster analysis showed that 31 alfalfa varieties were divided into five types, the varieties with best biological characters were Alfagraze, Ameriguard302,Dll, Ameristand201+z , Amerigraze401+z , Deguo-daye , Total+z and Vector.the varieties with poor biological characters were Abilene+z, Gs-88, Runner and Columbo.5. Study on the dynamic growing process of 31 alfalfa varieties showed that the biomass and the development of plant height fitted Logistic curve in whole developing stage. The results also indicated that the stage of quick accumulation of biomass and rapid growing of plant height was from late of ramification stage to budding stage, the maximal AGR and RGR also occurred in this stage, this stage should be that of crucial period of water. The potentiality of biomass was different among alfalfa varieties, the bigger varieties were Zhonglan No.l,Dll, Columbo , Amerigraze401 +z and Aggressor ,and yield of them might be improved by culture measures.6. Analysis on community structure of different varieties of alfalfa showed that distribution shape of total biomass in different layers was like rhomb, the upper of plant grown well. Archer, Haygraze...
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