为讨论叶表皮毛状体特征的分类学价值和系统学意义，借助体视显微镜和扫描电镜对中国杨属（Populus）33个物种的叶表皮毛状体进行了观察和分析。结果表明：杨属物种叶片毛状体整体上是非腺状的、简单的、基底固定的；除胡杨（P. euphratica）叶表皮没有毛状体外，其余物种叶表皮均被有毛状体，但毛状体的分布、形态、长度等在物种间存在不同程度差异。毛状体外形（圆柱状至条带状）、弯曲程度（直立至曲卷）、相对于叶表皮表面的方向（伏贴或不伏贴）及毛状体长度具有一定的分类学意义。结合分子系统发育研究提供的进化框架，本研究认为杨属叶表皮毛状体特征在亚属水平难以区分，但胡杨亚属（subg. Turanga）和白杨亚属（subg. Populus）在种间水平可区分很多物种，尤其是白杨亚属内的物种毛状体差异大；脂杨亚属（subg. Tacamahaca）内叶片毛状体相似且稳定，但不同分支上的叶片毛状体在长度上有差异。毛状体特征整合后可划分为以下类型：无毛、毡毛、绢毛、短柔毛和长柔毛。

In order to clarify the taxonomic value and systematic significance of leaf epidermal trichomes characters， the leaf epidermal trichomes of 33 species of Populus in China were observed and analyzed by stereomicroscope and scanning electron microscope. The results showed that Trichomes of Populus were overall non-glandular， simple， basally fixed； and all species except P. euphratica were covered with trichome in leaf epidermis， but the distribution， appearance， and length of the trichomes varied to different degrees among species. The shape of the trichomes（cylindrical to striped）， the degree of curvature（erect to curled）， the orientation relative to the surface of the leaf epidermis（ambulatory or not）， and the length of the trichomes were of taxonomic significance. Combined with the evolutionary framework provided by molecular phylogenetic studies， this study concluded that leaf epidermal indumentum characters of Populus were difficult to distinguish at the subgeneric level， the leaf trichomes within subg. Tacamahaca were similar and stable， but the length of leaf trichomes on different branches was different， however， many species could be distinguished between subg. Turanga and subg. Populus. Leaf trichomes characters could be divided into the following types after the integration of characters： glabrous， felted， sericeous， pubescent and villous.