Anatomia e ultraestrutura de coléteres de Genipa americana L. (Rubiaceae)

Abstract

The Rubiaceae family occupies the fourth place in the whole plant kingdom, in relation to the number of species, after the families Orquidaceae, Asteraceae and Leguminosae. With about 13,143 species, it covers around 611 genera, of which 26 have more than 100 species. Its geographical distribution is concentrated in hot regions, mainly in the tropics, where 75% of the species grow. In this context, the species Genipa Americana L. (Rubiaceae) is of great importance within the group, considering its use in the recovery of lacustrine ecosystems, an accentuated study of the chemical and pharmacological characteristics of its two major genipinal and genic acids, as well as its wide use in the most diverse contexts of the food industry, leather, beverages, paints, fuels, wood, among others. This research aimed to characterize the coléter present in the Genipa americana L. (Rubiaceae), in order to describe the process of ontogenesis, determine micromorphology and anatomy, characterize the process of secretion externalization, and perform histochemistry of secretion. The methodology used included Scanning Electron Microscopy, Optical Microscopy and Histochemical Tests. The results were: Ontogenesis in three stages: initial, intermediate and final, with the coléteres formed from cells of the protoderm and the fundamental meristem, through anticlinal divisions in the protoderm and periclinais. Coléteres organized in the base of the stipe in triangular format; standard type; presence of base constriction; epidermis paliçádica, consisting of secretory cells; central axis, consisting of elongated, non-vascularized parenchyma cells. Secretory mechanism presents accumulation of secretion and formation of subcuticular space, distension of the cuticle and release of secretion via pore cuticular secretory pore. The secretion analysis allowed to characterize the mixed nature and confirm the presence of mucilage, proteins, polysaccharides, lipids and phenolic compounds. The study of secretory structures, such as coléteres, has greatly contributed to the better characterization of representatives of Rubiaceae species, and has become an important research tool.