Studies on Leaf Epidermal and Pollen Micro-morphology and Geographical Distribution of the Genus Euonymus of Henan
|School||Henan Agricultural University|
|Course||Conservation and Utilization of Wild Fauna and Flora|
|Keywords||Henan Euonymus leaf epidermal pollen micro-morphology eographical distribution|
Euonymus, a genus of the family Celastraceae, are mostly distributed in subtropical and temperate zones of the eastern and western hemisphere, with East Asia at the centre. And only a few species stretch north in cold temperate zone. China, where there are approximately half of species distributed, is concentrated district of the genus Euonymus. In China, they are distributed in nerely every province and autonomous region, for most in south of the Yangtse River. So China is the key area for studies on the systematics and phytogeography of the genus Euonymus.Micro-morphological characteristics of the leaf epidermis of 28 taxa of the genus Euonymus distributed in Henan were observed by SEM. The results show that the most corneous layer are so thick that the structure of epidermal cells can’t be distinguished. There are only 3 taxa with the stomas being found both on the leaf upper epidermis and the lower epidermis,and the left taxa are all with stomas on the lower epidermis. All of the stomas are irregularlyon the surface of leaves. Sculpture can be devided as 3 types, smooth, striate, and reticulate. The smooth character occurs in most species, and the striate character occurs in a few species, and the reticulate character only occurs in one specie. The differences of stomatal size and density are not significant between the species. On the basis of experimental results, the author supports that E. bungeanus and E. maackii are both as independent specie respectively and E. macropteru and E. ussuriensis should be belonging to the same specie.Pollen of 9 taxa of the genus Euonymus was observed by SEM. The results show that most of the pollen grains are oblong-globose and a few are nearly globose in equatorial view. Most are 3-lobed to circular in polar view, and a few are suborbicular. All the pollen grains provide 3 aperture channels, extine reticulate, and the bud aperture is visible or invisible, prominent or not prominent. The pollen grains show not significant differences between species.It is knowed that there are 31 species of the genus Euonymus distributed in Henan based on extensive literature survey and field observations. Among the 31 species, there are 2 species newly record in Henan named E. hederaceus and E. euscaphis and 1 new variety record in Henan named E. bungeanus Maxim.var. multiflora S.X.Yan.This paper deals with the studies on eographical distribution of the genus Euonymus in Henan and comparations between Henan and the other provinces of China. Henan is a richer region the genus Euonymus distributed in, and distributing in each of the 4 mountains. The genus Euonymus are distributed most richly in Funiu Mountain , less richly in the other mountains. The results show that the species richness center is mostly in Yunnan and Sichuan, and the species richness is lowest in Inner Mongolia, Xinjiang and Jilin, which only 3 species are distributed in. Otherwise their endemic center is in Yunnan, secondly in Hainan, Taiwan and Xizang, which is obviously different of the species richness. Their similarity coefficient is mostly affected by the geographic localities. Their vertical distribution center occurs between 500-2500 m above sea level.