Pollen morphology of Wissadula Medik. (Malvaceae: Malvoideae) in Brazil

Malvaceae is divided into nine subfamilies, one of which is Malvoideae. Wissadula Medik., a genus within the Malvoideae, is divided into two sections according to mericarp morphology and the number of ovules per locule. Species belonging to the section Wissadula have three or rarely two ovules, whereas species belonging to the section Wissada have a single ovule. In Brazil, 19 species are recorded under the two sections, including a single species (Wissadula stipulata Bovini) in section Wissada and 18 in section Wissadula. This study analyzed pollen grains from both sections of Wissadula with the aim of confirming or not the existence of these sections based on pollen morphology. All 19 taxa occurring in Brazil were analyzed. The botanical material was collected from exsiccatae deposited in national herbaria and subjected to acetolysis. Subsequently, slides were prepared, examined under light microscopy, and photomicrographed. Pollen grains are monads, isopolar, large, suboblate, and triporate. The polar area is small in most species and large in a few others. The exine is thick, with echinate ornamentation, granules, and perforations. It was possible to distinguish the analyzed species based on of pollen diameters and spine characteristics (dimensions and distance). The findings showed that the pollen grains of species belonging to the two sections of Wissadula are similar in size, shape, aperture type, aperture number, and sexine ornamentation.