26种杜鹃属植物花粉形态及分类学研究

Pollen Morphology and Its Taxonomy of Twenty-Six Species in Rhododendron

利用电子显微镜对中国四川西南山区的26种野生杜鹃花粉进行观察和比较研究,其中21种为首次报道。26种杜鹃分属杜鹃亚属(Subgen.Rhododendron)杜鹃组(10种),常绿杜鹃亚属(Subgen.Hymenanthes)常绿杜鹃组(14种),糙叶杜鹃亚属(Subgen.Pseudorhodorastrum)(2种)。本属花粉均为四合体花粉,呈正四面体排列,单粒花粉球形或近球形,具三孔沟,极少数为四孔沟,表面粘丝多少不等。花粉粒外壁呈现大小颗粒、裂纹等不同纹饰,沟界区和极区与其他部位的纹饰并无明显差异。外壁纹饰和萌发孔长宽不宜作为亚属划分的依据,四合体直径可作为划分亚属的参考指标。在同一亚属内,花粉形态特征可作为划分组或亚组的辅助手段。花粉形态特征不宜单独用于种的鉴定,但结合组或亚组的划分,孢粉学特征对种的确定具有一定指导意义。

Pollen grains of 26 wild Rhododendron species in southwest mountain region of Sichuan were observed by using scanning electron microscope （SEM）, among which 21 species were reported for the first time. They belonged to 3 subgenera （Subgen. Rhododendron, Subgen. Hymenanthes, Subgen. Pseudorhodorastrum）, 4 sections and 12 subsections. All of them were tetrahedron with tetrad construction. Pollen grains of Rhododendron were spherical or subspherical with tricolporate and few of them with four colporates. There were varied visein threads on the surface. The size of tetrad and the pollen exine sculpture of them were different under SEM, whereas there was no conspicuous difference in the colpus and proximal exine. The difference of pollen exine sculptur and length and width of germinal apertures was not able to be used for classifying the subgenera, while the diameter of tetrahedron could be a trait used for further taxonomy. In the same subgenera, the morphology data of pollen could be used as supplementary characteristics to identify the section and subsection. It was not suitable for species indentification in Rhododendron only by morphological characteristics of pollen, however, it might be used for identification of some species within certain section and subsection.