Composição quí­mica e morfologia das ceras cuticulares foliares de diferentes espécies de Simaba Aubl. sensu stricto e Homalolepis Turcz. (Simaroubaceae)

Abstract

Simaba sensu lato was recently splited in two distinct genera, Simaba senso strictu and Homalolepis, both with mainly South American distribution occuring in different environments and morphoclimatic areas. Although their phylogenies are almost fully understood, some species still require attention. Studies with cuticular waxes have showed the usefulness of these characters in some phylogenies. Despite the great number of data concerning the chemical analysis of species of Simaroubaceae related to quassinoid composition, for the best of our knowledge there is no study with the chemical and morphological characterization of the cuticular waxes on this family. Therefore, in the present study, the chemical composition and the morphology of the leaf cuticular waxes of 119 specimens belonging to 20 species of Homalolepis, four from Simaba s.s. and three from related genera were analyzed. The waxes were extracted with dichloromethane and analyzed by gas chromatography coupled to mass spectrometry. The morphology of the epicuticular waxes was analyzed by scanning electron microscopy. Seventy compounds were identified in the waxes, comprising fatty acids, alkanes, primary alcohols, steroids and tocopherols. The most abundant classes were the fatty acids and alkanes. While fatty acids were the major class in Homalolepis, alkanes were more abundant in Simaba s.s. This quantitative distinction allowed the differenciation of the two genere. Notwithstanding, the composition of the waxes were very similar, as well as their morphology. Consequently, these data were not helpful in distinguishing the species. Concerning the wax composition in relation to the morphoclimatic areas, the speciemens collected in the Atlantic and Amazonian domains had thiner wax loads than those collected in the Cerrado. However, almost none correlation was found between wax chemical classes and the morphoclimatic area, except for the predominance of alkanes in the specimens collected in the Amazonian domain.