28种柳属植物的叶表皮微形态特征及其分类学意义

对28种表型相似、种间界限模糊的柳属植物在扫描电子显微镜下的叶表皮微形态特征进行观察,结果表明:柳属中有7种角质层蜡质纹饰,分别是平滑蜡质层、壳状蜡质层、痂状蜡质层、片状晶体、膜片状晶体、锥形纤维体和鳞片状纤维体,其中锥形纤维体和鳞片状纤维体为柳属所特有,而片状晶体和膜片状晶体为首次在柳属植物中发现；扫描电子显微镜下柳属植物叶表皮毛被的微观形态特征并不似其宏观形态(疏毛、绢毛、绒毛等)那样具有显著差异,微观形态主要表现为毛被密度、长短和卷曲方式(分为直,微弯曲和深度卷曲三种)的不同.研究表明叶表皮蜡质纹饰类型、气孔器的形态等微形态特征较为稳定,对柳属植物中表型相似的种类有很好的鉴定价值,但对组、亚属水平的界定作用不大；分布于寒冷地区和高海拔地区的柳属植物的叶表皮微形态特征相对多样,这可能是植物对寒冷环境的适应进化.

Leaf Epidermal Microfeatures of 28 Salix Species under Scanning Electronic Microscope and Their Taxonomical Significances

In this paper, twenty-eight species of the genus Salix, with similar phenotypic characters, were selected to study the leaf epidermal microfeatures under Scanning Electronic Microscope （SEM）. Seven types of wax layer are totally detected in those species, including smooth layer, crust, fissured layer, non-entire platelets, membra- neous platelets, conicoids and scale-like conicoids. Among those types, conicoids and scale-like conicoids are exclu- sively found in Salix, while non-entire platelets and membraneous platelets in Salix are depicted for the first time. The microfeatures of leaf hairs of Salix plants under SEM are less diversified than their macrofeatures, with detectable mi- crofeature variations on hair length, density and degree of curve （straight, slightly curved and deeply curved）. In con- clusion, our results showed leaf epidermal microfeatures of wax layer types and stomata1 apparatus are relatively un- changeable, which are valuable in the discrimination of similar Salix species. The Salix species from colder region and/or higher elevation usually bear diverse microfeatures, which might he adaptive evolution to colder environments.