柳属植物叶表特征的研究

STUDIES ON LEAF EPIDERMAL FEATURES OF THE GENUS Salix L.

About 52 species and 6 vareities among 17 setions of the genus Salix L. have been observed and studied in this paper, based upon their leaf epidermal features such as cuticle striations, covering trichomes, crystal in epidermis, stomatal types and their distribution, frequency, index and size. The presence or absence of cuticle Striations is relatively constant within sections and whether the presence of adaxial as well as abaxial stomata or the presence of stomata only on abaxial epidermis is extremely restricted within Sections. Amphistomatic leaves occur in Sect. Salix L, Sect. Subviminales (Seemen) Schneid., sect. Variegatae Hao, Sect. Cheilophilae Hao and Sect. Helix Dum. , the others have hypostomatic leaves. Stomata randomly orientate over most of the Surface except for areas over veins, and predominantly paracytic in most species of the genus, some species have two kinds of stomatal types, one smaller in size, usually paracytic, and another one larger, abnormal stomata, it is staurocytic or cyclocytic. On the point of view of evolution, in the genus Salix L., leaf epidermal features represent as, primitive species have larger epidermal cells, smaller stomatal index, and without or with very little crystal in epidermis, advanced species smaller on size of epidermal cells, larger stomatal index and with strong or very strong crystal in epidermis. In addition, epidermal features of leaves of Chosenia arbutifolia have shown that, it more relate to primitive sections (such as Sect. Pentandrae) of the genus Salix.