Studies On Population Genetic Differentiation And Flavonoids Variation Of The Endangered Plant Myricaria Laxiflora (Franch.) P. Y. Zhang Et Y. J. Zhang

Myricaria laxiflora (Franch.) P. Y. Zhang et Y. J. Zhang, an endemic plant species to the three gorge region and belongs to Myricaria Desv of Tamaricaceae, will be submerged completely after the construction of Three-Gorge Dam. It's listed as an endangered species in China. A total of six populations of Myricaria laxiflora were sampled from the Three-Gorge reservoir area. With data from morphology, allozyme, flavonoids, and SDS-PAGE electeophoresis, we analyzed the morphological differentiation among populations, genetic diversity within and among populations, and relationship between habitat and the secondary metabolize products, i.e., flavonoids. The results indicate as followings:Based on the study of morphological differentiation in different populations with numerical analysis, the results indicate as follow: Among 20 morphological parameters of 92 individuals in 6 populations, 8 parameters have the obvious differentiation. In addition,the morphological differentiation of 3 parameters reached the extremely notable level. ;The result of cluster analysis at the individual level shows that most of the individuals from different populations cluster together and the individuals from one or twopopulations doesn't emerge in some phenons,which means that certain degree of morphological and genetic differentiations occurred among popuIations.At the population level, there is remarkable morphological differentiation between Tiaoshi population and other 5 populations because of the geographical isolation. Furthermore,it isn't obvious in morphological differentiation between Peishi population and Wuxiakou population which means it is similar in genetic diversity because it is frequent in gene intercourse.Among the 7 tested allonzyme systems,5 allozyme systems,34 allonzyme bands,loci 16 of which include 9 polymorphisms and 7monomorphisms.The percentage of polymorphism loci (P) is 60.67 and mean number of allelesper locus (A) is observed 1.64, the effective number of it is 1.60.The expected heterozygosity per locus degree is 48% and the mean observed heterozygosity per locus is 82%.The higher level of the genetic diversity has been shown, which explains that the endangering species facing danger doesn't mean the decrease of the level of the genetic diversity.From studying the different amounts of flavonoids content in 8 population of M. laxiflora, the results indicate that the amounts of total flavonoids contents are different among populations. Among the differentiation there is remarkable genetic differentiation in some population, for example , the differences between Peishi population and Quchi population are the biggest. The factors that affect the amount of flavonoids content are illumination and temperature etc. Habitat can also affect the total amount of flavonoid contents .Observing the illumination and temperature in 5 different sampling sites, the amount of flavonoid content is higher in Tiaoshi population and Peishi population, especially higher in the Peishi population which inhabit the sunshine side of the mountain and the intensity of illumination is bigger and the temperature is higher. Most of Wangxia population, Quchi population and Wuxiakou population populated near Wuxiakou where the mountain is high and the species growing in the shade place with less illumination and lower temperature, which caused the less active of secondary metabolize production synthesizing and lower flavonoid accumulation.