Abstract:In order to clarify interactions between parasitic weed dodder (Cuscuta chinensis) and soybean (Glycine max L.), the degrade of damage caused by dodder parasitizing and related ecovphysiological response of soybean were evaluated in the fields. The growth of 14 soybean cultivars was investigated before and after being parasitized by dodder to estimate the damage degree, and one cultivar in each degree was selected for further determining the eco-physiological response to dodder in comparison with non-parasitized (CK). The result demonstrated that like the non-parasitized soybean, both growth and damage degree of soybean under parasitized with dodder were varied with the cultivars. Plants with high concentration of photosynthetic pigments, flavones, total N, and the higher net photosynthetic rate, were more easily parasitized and damaged with dodder, whereas the contents of soluble sugar were lowered. After soybean was parasitized with dodder, the trends of these index was adverse. These eco-physiological indexes were significantly varied with degree of soybean parasitized with dodder. The biomass of dodder parasitized in the severe damaged soybean cultivars were higher than that parasitized in weak damaged ones while the biomass of severe damaged soybean cultivars decreased more than that of weak damaged ones, therefore, the percentage of dodder biomass to the decreased biomass of soybean were higher in the weak damaged soybean cultivars. Both differences in growth differences of soybean cultivars parasitized by dodder and the damage degree of dodder on soybean, were related to photosynthesis, secondary metabolite, the transfer of assimilated products, and the total N content of soybean plants, and these differences became enlarged after being parasitized with dodder.