贵州30种杜鹃属植物叶背表皮显微形态特征

杜鹃属植物的分类历来都十分重视叶片表皮特征的分类学价值,无论是在各亚属之间还是在种及种下等级的划分中都很强调此类特征的作用。贵州省位于世界现代杜鹃分布中心边缘及向东部散布的过渡地带,省内自然分布的杜鹃种类资源丰富而又独具特色,包括很多尚未深入研究的特有类群。为进一步研究贵州杜鹃属植物的属下系统分类关系,该文对自然分布于贵州的30种杜鹃进行了叶背显微形态特征研究,其中有28种的叶背表皮特征为首次报道。研究材料全部来自采于贵州西北部百里杜鹃自然保护区内的杜鹃属植物,包括杜鹃亚属4种、糙叶杜鹃亚属1种、常绿杜鹃亚属22种、马银花亚属1种及映山红亚属2种,共计30种。研究方法为取成熟叶片处理后在JSM-6490型扫描电镜下对叶背表皮进行观测。叶背鳞片类型的划分方法参照前人工作。结果表明:这30种杜鹃叶片叶背表皮形态特征在电子显微镜下表现出明显的多样性,如有鳞类杜鹃具有鳞片而其他类群则无,叶表面有或无表皮毛,表皮毛排列稀疏或密生,气孔器未见或偶见,散生于乳突状或非乳突状突起之间,或角质层增厚气孔器下陷,内、外拱盖表面粗糙或光滑,气孔器周围有或无间断的条形突起,突起呈环状或羽状等,但在同一亚属或亚组中又呈现出或多或少的一致性。研究讨论表明,叶背表皮显微形态特征在杜鹃属植物的属下系统分类中具有重要的研究价值。

Micromorphological characters of leaf abaxial epidermis for 30 species of Rhododendron (Ericaceae)from Guizhou Province

As the largest genus in the family Ericaceae,the genus Rhododendron L. is well known because of the highly appreciated values to the world horticultural and the flora of China,but the taxonomy of the genus is rather difficult and confusing. Since the genus was established by Linnaeus,its infrageneric relationships have been well studied by many taxonomists on the basis of morphological characters and molecular data. Worldwide,experts recognize nine subgenera,which include about 1 000 native species that are distributed mainly in Asia,Europe,and North America,571 species found in China with 409 endemic. The southwest to central region of China,including Guizhou province,is possibly the location of the origin of the genus. The classification of the genus Rhododendron(Ericaceae)has always attached great importance to the characters of leaf epidermis,whether among different subgenera or in the division of species. Guizhou Province is located in the modern world Rhododendron distribution center edge and spreads to the east of the transition zone. In this province,the domestic species of the genus Rhododendron are abundant and unique,which include many that have yet to be in-depth study of specific groups. For further understanding of the classification of the genus in Guihzou,the micromorphological characters of leaf abaxial epidermis for 30 species of the genus were studied,among which there were some relevant characters of 28 species being reported for the first time. All research materials,including 30 species within 5 subgenera of Rhododendron,were obtained from the specimens collected from Baili Rhododendron Nature Reserve,which contained one of the largest natural Rhododendron communities in the world. After being treated properly,the characters of leaf abaxial epidermis were observed under JSM-6490 scanning electron microscope(SEM). The division method of the scale types was based on previous work by other scientist. Results showed that the characters of leaf abaxial epidermis of these 30 species under the electron microscope display obvious diversity,for instance,the leaf abaxial epidermis with or without vestiture/scales,the vestiture/scales sparse or dense,the stomatal apparatuses not observed or observed occasionally,the stomatal apparatuses scatter among papillary protuberances or non-papillary protuberances,or sink in thickened stratum corneum,inner and outer stomatal rims rough or smooth,surrounded or not surrounded by undulate-striates,the striates ringed of pinnate,etc. However,these characters showed more or less consistency within the certain subgenus or subsection. It could be concluded that the micromorphological characters of leaf abaxial epidermis of the Rhododendron species were systematically important and meaningful to the taxonomy of the genus.