Palynotaxonomy of species of Dendrophorbium (Asteraceae: Senecioneae) occurring in Brazil

Abstract

This article presents a pollen study of 13 species of Dendrophorbium (Asteraceae: Senecioneae) occurring in Brazil. Dendrophorbium has species distributed in the South and Southeast regions of the Brazilian territory that were previously grouped in Senecio Myriocephalus sect. and later Dendrophorbium was elevated to the rank of genus, considering the section Myriocephalus as a synonym of Dendrophorbium. The aim of this study is to advance knowledge of the pollen characteristics of the genus and thus contribute to the taxonomy of the group. The botanical material was collected from specimens deposited in national herbaria. Floral buds were acetolysed for light microscopic analysis. Pollen sediments were mounted on slides with glycerinated gelatin and analyzed under a light microscope. Measurements were taken of the diameters and thickness of exine layers of pollen grains. Examination showed pollen grains to be monadic, isopolar, medium-sized, oblate-spheroidal to prolate-spheroidal, and 3-colporate. The endoaperture has median constriction in most species, except in D. pellucidinerve. The sexine is thicker than the nexine and echinate, with large perforations at the base of echinae. The exine is caveate. Based on the results, it can be concluded that the pollen grains of the 13 Dendrophorbium species are homogeneous and can be differentiated by aperture shape and dimensions and echinus characteristics.