Anatomia floral de Hevea brasiliensis e Manihot tripartita (Euphorbiaceae, Malpighiales) com ênfase na homologia do nectário e perianto

Abstract

The pistillate and staminate flowers of Manihot tripartita and Hevea brasiliensis were studied to elucidate similarities and differences on the origin and development of floral characteristics. The applied methods ensure the assembly of histological lamina and image analysis through light microscopy. The results showed that the filamentous structures are similar anatomically, however do not share the same origin. In H. brasiliensis, only the pistillate flower has nectaries, which are vascularized by alternating and opposite traces to the sepals, suggesting a stem origin for these. In M. tripartita, pistillate and staminate flowers have nectaries of receptacular origin. However, in this specie, only the pistillate flower has vascularized staminodes by one bunch each that emerges directly from the eustelo. The position and amount of staminodes traces is the same as the two whorls occupy the staminate flowers. Therefore, nectaries and staminodes in pistillate flowers of both species share the same origin, that is, they are probably the result of the modification of the whorls of stamens present in perfect flowers in the ancestors. The formation of pseudanthias in some subfamilies of Euphorbiaceae was related to the loss of petals and the vestigial presence of this floral organ, but the combination of these characteristics does not seem to be obligatory for this type of inflorescence, because H. brasiliensis e M. tripartita presents paniculate inflorescences.