| Burdock (Arctium lappa L.) is a member of the composite family, and is a kind of 2-year borne giant herb. Some strains of the Burdock are of salt-resistance, which can be planted in the moderate saline soil. Burdock contains many bioactive substances and secondary metabolites, it hardly infected with pathogen. Burdock is of specific and important physiological action and pharmacological function. It is a Chinese herb, and also a kind of vegetable. At present, Burdock's economic value depends on burdock root exported to Japan and other European countries as edible vegetable. While international market rigidly control the quality of exported burdock root, so the substandard root would be discarded. Burdock root resource could not be made full use.In this paper, the extraction technique and structure analysis of Burdock oligosaccharide was studied, its growth-promoting action and influences on physiological and chemical properties of cucumber seedlings and induced effects on cucumber seedlings disease resistance were also studied. Following conclusions can be made from the study.1 The preparation technique of Burdock oligosaccharide by means of substandard burdock root was studied. The extraction conditions were optimized by the method of orthogonal design, and the optimum condition was determined. And the purification method had also been discussed. Through Sephadex G-50 chromatography separation, pure sample was obtained, its oligosaccharide content is 98% and 90% content in crude sample by phenol-sulphuric acid method assay. The physi-chemical properties and structure of Burdock oligosaccharide were measured by assay. The results show that Burdock oligosaccharide is of the basic feature of inulin or fructooligosaccharide, its degree of polymerization is only 13 and molecular weight is 2134. Its molecularcomposition includes 12 Fructose linked by glucoside bond and 1 Glucose linked byglucoside bond at the end of linear straight chain structure.2 The growth-promoting action of Burdock oligosaccharide(BOS) on Bifidobacterium was studied by in vitro assay. The results show that Burdock oligosaccharide is an effective bifidobacterium growth-promoting factor, and the strain of tested Bifidobacterium grew significantly better in BOS-containing media with 0.5%-1.0% BOS as the carbohydrate resource than in Glucose-containing media with 1.0% Glucose as the carbohydrate resource(p<0.05). Bifidobacterium is an obligate anaerobe. With this kind of germ, varieties of carbohydrate could be fermented to form acetic acid and lactic acid. As a result, the pH value of the media is decreased. Bifidobacterium is an acid-sensitive germ, its growth would be remarkably depressed.3 Effects of Burdock oligosaccharide on cucumber (Cucumis sativus L.) seed germination and seedling growth were studied by the treatments of seed soaking, solution culture and spraying. The results show that under tested concentration, Burdock oligosaccharide can promote seed germination and seedlings growth and high quality seedling forming of cucumber to a certain extent. In the tested group, growth indexes such as root length and seedling height, top-dry weight and root-dry weight, the numbers of lateral root increase significantly as compared with that in the control.Influences of Burdock oligosaccharide on physiological and biological properties of cucumber seedling were also studied. Cucumber seedlings were sprayed with different concentrations of Burdock oligosaccharide solution, the changes of chlorophyll content photochemical efficiency of PS II center and the relative permeability of cell membrane and free proline content soluble sugar and soluble protein content in cucumber seedlings were determined. The results show that under tested concentration, Burdock oligosaccharide can effectively promote chlorophyll content (especially chlorophyll a content) photochemical efficiency free proline content soluble sugar and soluble protein content in cucumber seedlings to a higher level. At...
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