Palinologia de espécies de Convolvulaceae Juss. ocorrentes na região Sudeste, Brasil - tribos Merremieae e Cuscuteae

Abstract

The family Convolvulaceae is cosmopolitan, widely distributed in the tropics and subtropics. In Brazil, there are 18 genera and 340 species, 151 endemic rocky fields, cerrado or caatinga. This work refers to palynotaxonomic study of pollen grains of taxa of Convolvulaceae occurring in the Southeast, Brazil - and Cuscuteae Merremieae tribes. We analyzed the pollen grains of 6 taxa of Cuscuta L., 12 taxa of Merremia Dennst. and 2 taxa of Operculina S. Manso. The botanical material used was obtained from herbarium specimens deposited in the main national herbaria. The pollen grains were treated through acetolysis and subsequently measured, described, photomicrographed light microscopy. For analysis in a scanning electron microscope (SEM), anthers were ruptured and the pollen grains, not acetolysed, spread over a ribbon. The results of this study showed that: in the tribus Cuscuteae were first recorded, colporate pollen grains; in the tribus Merremieae, the pollen morphology of the Merremia species showed variations already reported in previous publications, however the absence of polarity in some taxa is an unprecedented result. The number, shape of the openings and the presence of operculum, the ornamental base, ie microreticulate, reticulum or perforation and ornamentation above (granules, spines and microspines) were also important records herein. In Operculina, the results here expressed were new, since the few previous literatures mentioned only the amount of openings for the genus. The size, shape and ornamentation of sexina features are described for the first time in this study. The results obtained here allow us to confirm that Cuscuta, Merremia and Operculina could be identified through the pollen attributes, as well as their species were separated in the key elaborated here. It is confirmed therefore that the genera studied are eurypalynous.