Pollen brush of Astragalus L. subgenus Pogonophace Bunge (Leguminosae) and its systematic significance

The style morphologies of Astragalus subgenus Pogonophace (Leguminosae) were examined using the scanning electron microscope. The results showed that in most species, there are erect and upwardly pointed trichomes on the style. This kind of structure is exactly a pollen brush. The style of A. craibianus Simps. is glabrous, and there are finger-like projections formed by the epidermal cells only on the stigma. A. hoantchy Franch. has a penicillate stigma. The three types of styles are not homologous. These supported the exclusion of sect. Sesbanella and A. craibianus from Pogonophace. In molecular studies, some Pogonophace species are nested within the Coluteinae clade. This study found that those species rightly have the structure of pollen brush. Therefore, the pollen brush is likely to be a synapomorphy of Pogonophace and Coluteinae. The close relationship between Pogonophace and subtribe Coluteinae (tribe Galegeae) can be supported by the pollen brush.