SIMILARIDADE ESTRUTURAL VERSUS DIFERENTES COMPOSIÇÕES DO SECRETADO EM COLÉTERES DE ESPÉCIES CONGENÉRICAS: O CASO PREPUSA SSP. (GENTIANACEAE)

Abstract

Colleters produce a hydrolific and/or lipophilic secretion associated with the protection of meristems and developing organs. Due to the restricted endemism of Prepusa species (Gentianaceae) to mountainous areas of Brazil and the common occurrence of colleters in the family, we aimed to characterize the structure and composition of the secretion of P. connata and P. hookeriana leaf colleters, occurring in the Parque Nacional da Serra dos Órgãos (PARNASO), and P. viridiflora collected in Parque Estadual Pedra Azul (PEPAZ), both areas of rocky outcrops associated with the Atlantic Forest. Leaves at different stages of development were collected, fixed and processed following usual light microscopy techniques, including histochemical tests, and scanning electron microscopy. The colleters, in all three species, occur at the base of the leaves and have asynchronous development. They have a short peduncle and a secretory portion composed of homogeneous cells covered by a thin cuticle, a structure similar to that reported for other Gentianaceae species. Variations in the size of colleters can be observed. The secretion is predominantly composed of polysaccharides and proteins. However, lipids are present in P. hookeriana and P. connata, which may be associated with the fact that species in PARNASO occupy higher altitudes. Alkaloids were evidenced in adult and/or senescent leaves of P. hookeriana and P. viridiflora e; phenolic compounds related to structure senescence were observed for the three species. The abundance of polysaccharide secretion provides protection against dehydration since rocky outcrops at altitude have xeric characteristics at the expense of strong winds, high radiation and shallow or non-existent soils. Our studies show changes in secretion composition according to the altitudinal gradient reached by the species.