| Euphorbia is the largest genus in the Euphorbiaceae, there are 2000 species in the world, and about 80 species in china, and which is on the increase. The medicinal value of many species is very important and they have long been used in treatment of a variety of diseases, primarily were used for water purge, reducing swelling, heat detoxification, bleeding and wash scabies. There are about 14 Euphorbia species distributed in shaanxi province. The present study was targeted on 10 Euphorbia species, including E. helioscopia, E. humifusa, E. pekinensis, E. hylonoma, E. lunulata, E. esula, E. jolkini, E. lathylris, E. kansui and E. maculata. The paraffin sectionning and leaf epidermis isolating methods were used to compare the morphology and structure of their leaves and stems. The software Statistica6.0 was used to make the principal component analysis and cluster analysis based on structural feature values. At the same time, FTIR spectra of 10 species were compared. Then, their systematic relationships were analysed for providing experimental basis for the classification of the genus Euphorbia.1. Based on the observation of the epidermis of these 10 species, it was found that the structures of leaves were significantly different, for example, the size of the main veins and the alignment and density of palisade tissue and spongy tissue in the mesophyll were different. The upper and lower epidermis was irregular or polygonal. The anticlinal walls of epidermal cells were straight, light wave, wavy and heavy wavy. The Stoma were irregular-shaped and usually on the lower epidermis. In addition, the stoma was also distributed on the upper epidermis in some Euphorbia species, such as E. humifusa, E. helioscopia and E. esula. There were various differences in the structure of the stem. The most significant feature was that the pith parenchyma cells of some species connected each other to form a network structure with many cavities, such as E. helioscopia, E. pekinensis, E. hylonoma, E. lunulata, E. esula, E. jolkini, E. lathylris, E. kansui. 2. Multivariate statistical analysis method was applied. The principal component analysis on the morphology characteristics of 10 species were selected as three principal components, the contribution rate of the first principal component was 44.15%, and the the total contribution rate of the first three principal components was 78.08%. According to the first three principal components, three-dimensional composition diagram was obtained,10 Euphorbia species could be divided into three categories. E. kansui was divided into the first class, E. maculata was divided into the second class, and the others were divided into the third class. On the other hand, based on the cluster analysis of morphological characteristics, E. kansuiwas divided into one class and the others were divided into another big class. In the second big class, E. humifusa was most closely related to E. maculate and E. jolkini was most closely related to E. lunulata. Results of the principal component analysis and cluster analysis were generally consistent.3. Because of the differences in the chemical composition of leaves, FTIR spectra of Euphorbia have demonstrated differences in the number of peaks and waves. Based on FTIR data,10 Euphorbia species were divided into two categories by cluster analysis, Euphorbia kansui was a class; and the others was another one.10 Euphorbia species could also be divided into three categories by principal component analysis, E. kansui was a class, E. jolkini was a class, and the others were a class. It could be seen that the result of the analysis based on FTIR data was similar to that based on morphology, E. kansui is quite different with the others.The results showed that there were some differences between leaves of 10 Euphorbia species, such as the anatomical structures of stems and leaves, the epidermal morphology and the fourier transform infrared spectra. According to the analysis on fourier transform infrared spectra and morphology of stems and leaves by cluster analysis and principal component analysis, the result showed that E. humifusa was most closely related to E. maculate. E. jolkini was most closely related to the E. lunulata. On the contrary, E. kansui was not so closely related to others.
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