Palynotaxonomy of the genus Gladiopappus (Dicomeae, Asteraceae) with special emphasis on the exine ultrastructure and mesoapertures

Abstract

The pollen morphology of Gladiopappus vernonioides was studied with transmission (TEM) and scanning (SEM) electron microscopy and with light microscopy (LM). An Anthemoid pattern of exine ultrastructure was found. The pollen morphology of Gladiopappus supports the inclusion of this genus in the tribe Dicomeae and subtribe Dicominae but not in the Mutisieae s.str. The apertural system of G. vernonioides includes a mesoaperture that intersects the foot layer and the upper layer of the endexine, a condition already pointed out for several tribes of Asteroideae (Helenieae, Gnaphaliinae, Heliantheae, Inuleae, Senecioneae) and Carduoideae (Cardueae, Dicomeae). It is suggested that the existence of an intermediate aperture could characterize the apertural system of the Asteraceae as a synapomorphy.