毛冠菊属舌片的微形态特征及其系统学意义

在扫描电镜下观察了毛冠菊属Nannoglottis 8种植物舌片的微形态特征,以探讨其颇有争议的系统位置。所有种类舌片近轴面的细胞为板状,长圆形;径向、切向壁直;外壁特征性突起,外壁中央为纵向皱纹,相邻细胞之间的纹饰无系统连接。这些特征表明毛冠菊属和紫菀族Astereae关系密切,但它在紫菀族内的系统位置可能比较特殊。这些结果和依据ITS序列推测的紫菀族系统发育的结果相吻合。文中还讨论了一些微形态性状的演化趋势以及微形态性状在毛冠菊属部分种类分类中的应用。

Microcharacters in the ligules of Nannoglottis (Compositae) and their systematic significance

The systematic position of the taxonomically controversial Nannoglottis is investigated based on SEM observation on microcharacters of the ligules in eight species of the genus. All the species are characterized by having an adaxial epidermis of the ligules consisting of oblong, tabular cells, with the radical and tangential walls being straight; the outer wall with a characteristic thickening along the median plane of the cell; the median plane of the cuticle of outer wall with a pattern of longitudinal rugose stripes; and no systematic connection between the patterns of adjacent cells. This supports a close affinity between the genus Nannoglottis and Astereae, and also indicates the unique systematic position of this genus in the tribe. These results agree with those of the study of the phylogeny of Astereae using ITS sequences. The evolutionary trends of some microcharacters and the utility of microcharacters in the taxonomy of some species of Nannoglottis are also discussed.