Development of the pollen and anther wall of Tabebuia ochracea was studied. The microsporangial wall follows the Dicotyledoneous type of ontogeny. The sporogenous tissue in each microsporangium, in transverse section, is organized in a celular strip, with a horseshoe outline. The tapetum is secretory and shows a distinct dual origin. The inner tapetai layer differentiates earlier than the outher layer. The two tapetai layers exibit a distinct structural dimorphism, but before the meiotic divisions of the MMCs the tapetai layers become identical. Vacuolation in each tapetai cell, at this stage, is characteristically bipolar. The endothecium shows fibrous thickenings of the spiral type. The pollen grain development conforms with the usual way in angiosperms. The conspicuous growing of the nucleolus and nucleolar vacuolation into the generative cell sugests a high biosynthetic activity.
Bignoniaceae; Tabebuia; ontogeny; tapetum; placentoid; microspores; male gametophyte; pollen; nucleolar vacuoles