Anatomia dos órgãos vegetativos (ráquis, pecíolo foliar e raiz) da espécie Bactris major Jaqc. que ocorre na ilha do Combu-PA

Abstract

Bactris major jaqc. (Arecaceae), commonly known as marajá grande, is a palm tree of clump habit with stipes 2-8m high and 2-6cm in diameter, with infructescence in bunches and dark brown fruits when ripe. Occurring in flooded areas, B. major jaqc. is present in the vegetation of the island of Combu (floodplain ecosystem), Belém-PA. The present work aims to continue the study of the plant anatomy of B. major jaqc. by describing its vegetative organs (rachis, leaf petiole and root). The botanical material collected in the field was fixed in FAA (solution 1:1:1, formaldehyde, acetic acid and alcohol) for 24 hours, to later perform transversal and paradhermal cuts following the usual techniques in plant anatomy. As a result, we found that the petiole and the rachis had the same structural configuration where: in the paradermal section the epidermal cells are lined up, irregular and between them there are stomas (paracitic and tetracitic) and pluricellular trichomes; in the transversal section we observed that the lining tissue is covered by a thin cuticular layer, internally there is a grouping of lignified fibers forming a ring. As for the arrangement of the vascular elements in the above organs, we can see that there are two types: one aggregated to the fibrous ring and the other dispersed in the medullary region. In this same region, clusters of non-lignified fibers are common. The root has three very distinct layers: a lining tissue consisting of well-developed epidermal cells and a tenuous hypodermis; a sheath of lignified exodermal fibers surrounding the cortex and pith with alternating vascular elements, common in palms. The species studied presents a structural configuration common to the family, but with characteristics peculiar to B. major jaqc. and adapted to the flooded environment.