Estrutura e histoquímica de Cephalostemon gracilis (Rapateaceae): uma espécie endêmica da Amazônia brasileira.

Abstract

Cephalostemon gracilis (Poepp. &Endl.) R.H.Schomb. is an endemic species from Amazon region, usually found in restinga, herbaceous swamp areas and open shrubland formation. The species is morphologically featured by long and broad leaves, long bracts, glaborous scape, capituliform inflorescences, spikelets, bracteoles with hair inside and lanceolate sepals. In addition to these features, it is also visible abundant hyaline secretion in its inflorescences and leaf axils. In order to understand the structure and dynamics of the species, it was performed an anatomical and histochemical study. For structural analysis, it was studied vegetative (root, leaf sheath and leaf blade) and reproductive parts (escape, bracts and bracteoles), using the usual techniques of plant anatomy and photomicrographs with micrometric scales designed in the same optical conditions. Anatomically, the species has uniseriate epidermis with presence of silica bodies in the leaf sheath and leaf blade, tetracytical stomata in the leaf sheath, leaf blade, escape, bract and bracteole, mucilage secretory trichomes in the leaf sheath, bract and bracteole, aerenchyma and idioblasts in the parenchyma of all parts, subepidermal fibers, and collateral bundles. It was possible to diagnose specific characters and unprecedented occurrence of mucilaginous trichomes on the faces of the bract (adaxial) and bracteole (on both sides), producing mucilage in abundance, no hypodermis, and the midrib V-shaped. This diagnosis helps to understand the relationship between plant and environment, and features the species comparing it to other genera of Rapateoideae (Rapateaceae).