| Thesium chinense Turcz.(Santalaceae)is an obligate root hemiparasite and the whole weed resource is a traditional Chinese medicine with heat-clearing,toxin-resolving,cough-stopping,phlegm-resolving,kidney-nourishing,essence-astringing,summer heat-clearing and damp-draining effect.It is used for the treatment of acute mastitis,pneumonia,tonsillitis,upper respiratory infection and acute cystitis,etc.Modern studies have indicated that T.chinense has significant anti-inflammatory,summer heat-resolving,analgesic and broad-spectrum antibacterial function.It has be known as "plant antibiotics",which has important medical value.At present,its preparations that be taken as the single ingredient formula are tablets and capsules.T.chinense has been under seriously threat due to the special lifestyle,overexploita-tion and habitat disruption,its wild resources has been decreasing sharply.In order to better protect the resource of T.chinense,achieve its natural cultivation,domestication and provide theoretical support for the research of parasitic mechanism,this paper conducted researches about the population ecology,structural biology,host preference and dormancy of T.chinense.Details are as follows:Methods such as field survey,experimental analysis and statistics were used to study the environmental adaptation characteristic of wild T.chinense in the lower regions of Yangtze River.Results were as follows:1.The common habitat type of T.chinense in the lower regions of Yangtze River was community coverage and low-height with good drainage.Its plant community characters showed that the community coverage had a certain seasonal fluctuation with lower coverage in early spring and higher coverage in summer.The more species compositions of plants,the more distinct synusias of the community height.T.chinense relied highly on the soil environment and had high soil organic matter and root density.2.There was different between functional traits and habitat conditions of T.chinense.Its variability was as follows:the trait variation degree of 1 age-class T.chinense was higher than that of 2 age-class T.chinense.The characteristics of T.chinense was largely effected by the plant community dynamics and soil environment condition.The growing season of 1 age-class T.chinense was much longer,thus the environmental factor had more obvious influences on characteristics of 1 age-class T.chinense.The biomass accumulation characteristics of single stub T.chinense indicated significant differences in each age-class biomass.The weight of stem and seed of single stub biomass was in the advance,while there were some connections among several characteristics of 1 age-class and 2age-class T.chinense.The observation of T.chinense’s phenological period showed that T.chinense in the lower regions of Yangtze River was the biennial plant.The result of T.chinense’s age structure in different habitats proved that the age structure of T.chinense was composed by 2 age-class plants in early spring.The difference between the quantity of 1 age-class and 2 age-class T.chinense became larger when the seedlings emergence date was started.The community was replaced by the dominant 1 age-class T.chinense in the end.The population of T.chinense was mixed-age population during March-June period,while it was the simple population that consisted by single age class in other periods.The analysis of the life table and survival curve showed that the soil seed of T.chinense was fairly rich under natural conditions.The critical period of T.chinense in growth process was seedling.The soil seed bank was relatively abundant under natural condition.Its bionomic strategy was typical r-strategy.T.chinense’s population in the test area had a certain inter-annual stability.It could keep striving on the earth under normal conditions,such as an area without the presence of human activity.At present,the lack of its resource might have connection with social demand and habitat fragmentation.Thus,the exploration of the domestication and cultivation of T.chinense was feasible.The key of cultivation was how to increase the survival rate of seedlings.The leaf,stem and root of T.chinense had distinct characteristics,thus its adaptation to water condition was obvious.The T.chinense leaves were in ring-palisade type with the sunken stomata on the leaf epidermis.The mesophyll cell of T.chinense was small and arranged compactly.The conducting tissue in the axis of was developed.The stem cortex contained chlorophyll with developed mechanical tissue.Its main root was developed with a lot of starch were accumulated in the cortex and pith rays and was classed as the storage root.1 age-class T.chinense mainly accumulated nutrients and carbohydrate synthesized was stored in parenchyma cells of the developed main root.Starch,stored in main roots,might support crown buds grow fast the following year and be the energy basis to its propagation process according to the amylum content and changing process of T.chinense in each age class.The origin of T.chinense’s haustoria and its early developmental stage shared the same process with the lateral root,the difference was differentiation of the hyaline body.The haustorium might be formed by chemical substances,released by roots of the host and changed the development model of the root cap when contact with or close to the host root.The host root could resist or reduce negative factors caused by parasitism.The statistical test about the parasitical rate of T.chinense that parasitized specific hosts showed that T.chinense chose to parasitize the species which widely distribute with larger occurrence probability in communities and it had an obvious preference to the host.Hosts with different structures of host roots had different adaptive strategies,such as increase the quantity of the haustorium when parasitize thinner roots or increase the size of the haustorium when parasitize thicker roots.Methods such as physiology and differential expression were conducted to uncover the physiological difference between the root and crown bud of T.chinense during dormancy condition.Results were as follows:The starch content in the main root reached the highest when 1 age-class T.chinense enter dormancy.The soluble sugar content of each organ during dormancy was higher than that in other periods.There was no significant difference of a amylase activity in the root and crown buds during dormancy,but the significant difference did exist in the lateral root and crown bud.T.chinense RNA was extracted from crown buds and roots of wild T.chinense and SSH library of forward and reverse was established.410 ESTs were obtained after sequencing the product of SSH library and 241 ESTs were annotated by comparison and GO analysis.The result of EST identification showed that hormone synthesis and the hormonal response gene expression of T.chinense were obvious during dormancy period.There was also gene EST expression about environmental stress response.The root differential expressed SSH library had a lot metabolism-related ESTs.Winter temperature or drought characters might have a certain stressing effect.After executing twice classification on annotated ESTs,it revealed that these ESTs might have various molecular functions,such as catalytic activity,binding,molecular sensing activity,transport activity,structure molecule activity,molecular function regulator,nucleic acid-binding transcription factor activity,antioxidant activity,transcription factor activity and protein binding,etc.After the analysis of metabolic pathway,49 ESTs were annotated to KNGG that belonged to 78 KNGG metabolic pathways separately,including kinase,ATPase,related enzymes in fat metabolism,EST ascorbic acid metabolism,purine metabolism,antibiotic biosynthesis.Flavonoid-biosynthetic enzymes in metabolic pathway were mapped which reflected that specific metabolic activities were still take place during dormancy. 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