ON THE FLORAL STRUCTURE AND COLLETERS AND THEIR BEARING ON THE SYSTEMATICS AND EVOLUTION IN SOME SPECIES OF RUBIACEAE

Resumo

The literature reveals that the tribes Psychotrieae and Spermacoceae (Rubiaceae) have problems delimiting genera and species and suggests the need for further studies, particularly of a morphological nature. In this context, the present investigation aims to study the floral structure and morphology of colleters of nine species from both tribes. The analysis was performed on flower buds and flowers of botanical material obtained from plants collected from different vegetation and from herbarium specimens. The samples were embedded in historesin and sectioned in a rotating microtome. The sepals exhibit a homogeneous or dorsiventral mesophyll. The petals, in general, have a homogeneous mesophyll. The colleters belong to the standard type, showing differences especially in the peduncle morphology. All species have compitum and can be considered eu-syncarpous. The ovary is inferior and exhibits basal placentation in Psychotrieae and axile placentation in Spermacoceae. Characters such as the absence of inverted vascular bundles in the ovary wall and ascending vascularization of the ovules indicate the appendicular nature of the ovary. Some characters related to the perianth, colleters and vasculature of the ovary wall and septum may be useful in separating the species. The type of placentation is a reliable character to separate Psychotrieae from Spermacoceae.