Effects Of Nitrogen Application Levels On Carbon-Nitrogen Metabolism, Functional Composition Content And Medicinal Material Yield Of Desmodium Styracifolium

Desmodium styracifolium is a commonly used in traditional Chinese medicine,and the wild germplasm resources of it have been rare and endangered in recently years by the reason of over exploitation.At present, most of the commercial medicinal material of D.styracifolium is artificial cultispecies.However,there is little report on the cultivation techniques of D. styracifolium,especially on the fertilizion techniques.Therefore,a field experiment according to randomized block design was carried out to study the effects of 5 nitrogen application levels(0,37.5,75.0,112.5 and 150.0 kg·ha^-1) on the carbon-nitrogen metabolism,functional composition content and medicinal material yield of D.styracifolium,and to find out the optimal nitrogen application level of it.The results were summarized as follows:1.Nitrogen application could increase the contents of chlorophyll(CHL) and soluble protein(SP)of the leaves of D.styracifolium and retard the leaves aging,and thus,the content of reducing sugar(RS),sucrose(SC)and starch (ST)of the leaves were increased,and the carbon metabolism was improved. And nitrogen application could improve the nitrogen metabolism though increasing the activities of nitrate reductase(NR)and glutamate-pyruvate transaminase(GPT)as well as the contents of ureides(UR)and total nitrogen (TN)of the leaves.Moreover,nitrogen application affected the regulation of carbon and nitrogen metabolism of the leaves,and the sugar-nitrogen ratio (S/N)of the leaves was increased.However,it was not always significant that the physiological parameters of carbon-nitrogen metabolism of the leaves were improved by nitrogen application with the increasing of nitrogen level, of which the contents of RS,SC and TN as well as the activity of GPT of the leaves under of 150.0 kg·ha^-1were no significant difference compared with those under the nitrogen level of 112.5 kg·ha(-1)(P＞0.05),and the content of UR of the leaves under nitrogen application levels of 112.5 and 150.0 kg·ha(-1) were significantly lower than that of 0 kg·ha^-1(P＜0.01).2.Nitrogen application could increase the contents of polysaccharide, total flavonoides and total saponins of D.styracifolium.However,with the increase of nitrogen level,the enhancing extent of the functional composition content was not always significant,of which the contents of the polysaccharide were no significantly difference among the nitrogen application levels of 75.0,112.5 and 150.0 kg·ha^-1(P＞0.05),and the content of the total flavonoides under the nitrogen level of 150.0 kg·ha^-1was significantly lower than that of 0 kg·ha^-1(P＜0.01),and the content of the total saponins under the nitrogen level of 150.0 kg·ha^-1was no significant difference compared with that of 112.5 kg·ha^-1(P＞0.05).3.Nitrogen application could increase the medicinal material yield of D. styracifolium.However,the medicinal material yield were not significantly different among the nitrogen application levels of 75.0,112.5 and 150.0 kg·ha^-1(P＞0.05).According to the above results,it was concluded that the carbon-nitrogen metabolism,functional composition content and medicinal material yield of D. styracifolium showed good performance under the nitrogen application levels of 75.0 to 112.5 kg·ha^-1,and suggesting that it was the optimal nitrogen application levels of D.styracifolium under the condition of this experiment.