| Ceratoides arborescens belongs to Chenopodiaceae, Ceratoides genera, monoecism subshrub. It is endemic to China and mainly distributed in Mid-Eastern Inner Mongolia and North China. It has rich nutrition and strong resistance and is an important plant that is used for constructing ecology and improving grassland. Up to date, wild C. arborescens population degraded seriously, some population degraded up to 70%.However, the study on the reproduction peculiarity and degraded mechanism of this species is still unknown.Therefore,the paper focuses on reproductive ecology of C.arborescens population in population dynamics, pollination ecology, embryonic development and physiology, seed characteristics,reproductive allocation and genetic diversity,the main results were as follows:1. The analysis on the age structure of C.arborescens populations showed that there were fewer young individuals, but middle-aged and old individuals were relatively rich. The analysis on the life tables and survival curves showed that the survival curve of C.arborescens populations belonged to DeeveyⅢ, and the death peak of different populations was in the period ofⅧandⅨ.The number difference among populations reflected the population habitat. Time sequence prediction indicated the numbers of old individuals would be increased at the beginning, and decreased finally in some years later. It was difficult to maintain the population stability.2. The study of pollination ecology showed that C.arborescens adapted to anemophily. The duration of flowering in a population lasted 45～52 days; male flower male flower 18～21 and female flower lasted 20～26d at individual plant level; flower male flower 1～2d and female flower 6～8d at individual flower level, and there were no significant differences among populations. The pollen viability and stigmatic receptivity could last 6d and 6 to 7d respectively. The effective pollination way was wind and the efficiency of pollination had significant effect on seed setting rate.3. The embryo development speed of the cultivate C.arborescens is faster than the feral C.arborescens and the embryo development modes are both chenopodiad; There are abortion phenomenons in feral C.arborescens embryo development. The peroxidase and acpase activity in C. arborescens had a tendency of ascent with the embryo development. The nitrate reductase activity during early period of embryo development increased significantly and then decreased, and that in cultivate C.arborescens seeds was lower significantly than feral C.arborescens seeds. The contents of IAA,GA3 and ZR in cultivate C.arborescens seeds were higher than two types of feral C.arborescens seeds; The ratio of (IAA+GA3+ZR)/ABA in two types of C. arborescens seeds was high during the early period of embryo development, and then had a tendency of descent with the development of embryo, and the ratio in cultivate C.arborescens seeds was higher significantly than two types of feral C.arborescens seeds. During the embryo development, the nutrient(N,P,Soluble sugar) contents of the cultivate C.arborescens is higher than the feral C.arborescens.4. The seed characteristics showed that there were significant differences among population and among individual plants within populations.The variance factors analysis indicated that the variation within a population was the main part of the phenotypic variation. The morphological traits of seed had significant positive correlation with each other (P<0.01). The pappus length and latitude and rainfall, as well as, between seed width and temperature and rainfall had significant correlations(r>0.801, P<0.01). The three germination-related indices had significant positive correlations with each other (r > 0.836, P<0.01) and with percentage of seed fill(r>0.896, P<0.01), however, possessing weak correlations with morphological traits.5. The characteristics of reproductive allocation showed that reproductive allocation of biomass, total nitrogen, total phosphorus,total potassium in C.arborescens increased gradually from the flower bud phase to the flower and fruit phase.Allocation of stem and leaf took advantage ratio in the flower bud and the flower phase, and reproductive organs took advantage ratio in fruit phase. The reproductive age of C. arborescens can be divided into four stages in terms of the relationship between the reproductive allocation of biomass and the age of the reproductive individuals. These are the junior, non-stable, stable and declining phases. The most important components to affect pattern and development of C.arborescens population were altitude, slope face, vegetation cover, C. arborescens cover, thickness of soil, annual mean precipitation, annual evaporation and intensity of human disturbance. Three hypotheses were evaluated with regard to the observed patterns of reproductive allocation.One hypothesis, that reproductive allocation patterns were a function of differences in resource availability, did not provide an explanation for our results. A second hypothesis, that reproductive allocation was negatively correlated with successional maturity of the habitat could explain the observed patterns of reproductive allocation. The third, life history hypothesis which assumed the existence of a trade off between current reproduction and vegetative growth and/or survival rate, could explain patterns of reproductive allocation in part.6. The research of genetic diversity showed that at species level, percentage of polymorphic loci PPB is 98.05%, Nei′s gene diversity is 0.298, and Shannon′s information index is 0.456.At population level, PPB is 80.62%, Nei′s gene diversity is 0.268 and Shannon′s information index is 0.403. C.arborescens population had an extraordinarily high level of genetic diversity. The analysis of molecular variance (AMOVA) showed that 86.79% of genetic variance was found within populations, and 13.21% of it was resided within populations. The coefficient of gene differentiation (Gst) was 0.1035.The level of genetic differentiation between populations is lower than that among populations. According to cluster analysis and the law of geographic variation, the populations were classified into two large groups: desert grassland group and typical grassland group.
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