Study On Taxonomy And Characters Of Leaf Epidermis Of Astragalus L. And Oxytropis Dc. In Altay Region Of Xinjiang

The genera Astragalus and Oxytropis, belong to the tribe Galegeae of subfamily Papilionoideae in Leguminosae. These two genera almost distribute in all continent except for Oceania. They mainly distribute in northen temperate zone, with its most diversity in Midd1e Asia, West Asia and western North America.In this study, we investigated the distribution of the genera Astragalus and Oxytropis in Altay region. The characters of leaf epidermis of 28 species of Astragalus and 14 species of Oxytropis were examined under the optical microscope. The main results are as follows:1. According to specimen examination, field investigation and referring to literature, we conclude that there are 63 species of the Astragalus group and 24 species of the Oxytropis group in Altay area, of which Astragalus chinensis Linnaeus was newly recorded species in Xinjiang.2. By observation the leaf epidermis micro-morphological of species, we found that Astragalus scoparius Schrenk was a special species. Abaxial epidermal cells were rectangle, different from other species.3. The leaf epidermis characters of 42 species were examined by light microscope in China. The results showed that all species were amphistomatic, but the adaxial epidermis or the abaxial epidermis of some species almost had no stomata. In the specimen having been studied, A.mongholicus Bunge of Sect.Cenantrum and O. deflexa (Pallas) Candolle of sect.Mesogaea had few stomata. Therefor, the distribution of stomata on the epidermis could be regarded as the important character in division of section.4. The stomatal types are:isotricytic, tetracytic and anomocytic. The quantity of anomocytic in genus Oxytropis was more than that in genus Astragalus. Based on the theory that proposed by Stsbbin and Khush in 1961, it is that the species with anomocytic stomata was the most evolutional species, so some species of Oxytropis was more evolutional than Astragalus. 5. By the leaf epidermis character observation, we found that the stomatal densities of Sect. Alopecuroidei, Sect. Trachycercis, Sect.Laguropsis, Sect.Erioceras, ect.Ammotrophus and sect.Eumorpha were larger than that of other sections, in which most of the species were xerophil. So the density of plant stomatal directly correlated to the drought degree of the habitat condition.6. Except for few species, the abaxial epidermal cells of plant of Oxytropis were anomocytic, and the anticlinal walls were sinuate.