Ontogenia dos estratos parietais da antera de Tabebuia Pulcherrima Sandw. (Bignoniaceae)

Abstract

The ontogeny of the tapetum and parietal layers, as well as the stomium development and the dehiscence of the anther of Tabebuia pulcherima was studied. The anther wall formation follows the Dicotyledoneous type. The primary parietal layer, the sporogenous tissue, and the inner tapetum are differentiated directly from the ground meristem. The sporogenous tissue, as seeing in a transverse section, is organized in one cellular strip with a horseshoe outline. The tapetum is secretory and shows a distinct dual origino The inner tapetal layer differentiates earlier than the outher. The two tapetallayers are moderately dimorphic. However, even such a dimorphism is lost at the end of the sporangium meiosis. The tapetal dimorphism and the precocious differentiation ofthe inner tapetum was interpreted as expression of a developmental gap between the two layers. At the four comers of the anther, a multilayered endothecium with annular or spiral fibrous thickenings in their cell walls is formed. The deiscence is preceded by the placentoid tissues degeneration and the rupture of the interesporangial septa. Only the epidermal cell rows, at the two sides of the stomial dehiscing place, are involved in the stomium rupturing.