| The reseach studied the contents and distributions of carbohydrates and total nitrogen, (C/N) ratioes, and dynamic patterns of carbohydrate and nintrogen in Cynanchum komarovii and Glycyrrhiza uralensis, which grow in the boundary area of the Muus desert. The results showed that every organ had a storing capacity of carbohydrates but the main storing organ was roots in those two kinds of plants. Final storing form of carbohydrate was differenti in both Cynanchum komarovii and Glycyrrhiza uralensis. Soluble sugar was a main storing form in the roots of Cynanchum komarovii, but starch instead of soluble sugar in the roots of Glycyrriza uralensis. There was difference in dynamic change between carbohydrates accumulation and degrading during different growth periods. The change of soluble sugar in Cynanchum komarovii was very similar to the change of total sugars, but not in Glycyrrhiza uralensis. The total nitrogen was the highest in leaves, followed by stems, and then by roots. The change in C/N ratio was quite contrary compared with that of total nitrogen. Compar ison with the roots of Glycyrrhiza uralensis showed that the roots of Cynanchum komarovii needed less nitrogen during it's whole growth; But the requirement of nitrogen was much higher in Cynanchum komarovii roots than that of Glycyrrhiza uralensis roots. It indicated that the soluble sugar was not only the main photosynthate, but also the good osmatically regulating material in Cynanchum komarovii under water stress. Low requriement of nitrogen in Cynanchum komarovii reduced the susceptibility to water stress and also made Cynanchum komarovii have a higher resistance to drought and infertility. |