Anatomia comparativa dos órgãos vegetativos aéreos de Malvastrum coromandelianum Garcke e Malvastrum tomentosum (L.) S. R. Hill (malvaceae).

Abstract

Malvastrum A. Gray is a small genus of the family Malvaceae subfamily Malvoideae, represented in Brazil by three species. Despite the proven ocurrence in all Brazilian regions, in the country the genus is cited mainly in floristic surveys and in the taxonomic studies, being this the first anatomical treatment with the genus in the country. Considering that anatomy is an important tool of taxonomic value, it is necessary to investigate the struture of the vegetative organs that provide subsidiesfor the caracterization and distribuiction of the species. In this sense, the presente work aimed to perform anatomical and histochemical descriptions of leaves and stems of Malvastrum coromandelianum Garcke, known popularly as “guanxuma” and Malvastrum tomentosum (L.) S. R. Hill, in order to recognize userful characeters that provide subsidies for the identification of taxa. The anatomical analyzes were performed in freshband hydrated samples. For the anatomical studies, we perfomed paraderms and transverse sections, later clarified and stained with safranin and/or safrablue, observed and photographed under na optical microscope. Histochemical tests were performed to reveal diferente compounds. M. coromandelianum Garcke and M. tomentosum (L.) S. R. Hill share the following anatomical caracteres: uniestratified epiderms, stellatyes trichomes and glandular trichomes, anisocytic and anomocytic stomates with anfistomatous distribution pattern, biconvex main vein with a single central colateral budle, concave-convex to flat convex, angular collenchyma, dorsiventral mesophyll, and idioblasts containing calcium oxalate crystals. However, some leaf characters were distinctive, such as the indumento, the contour of the epidermal walls, the number of strata in the palisade parenchyma, the number of vascular bundles on the petiole, the presence/absence of a sclerenchymal sheath bypassing vascular bundles on the petiole. The stem in secondary growth, presented the same pattern referred to other species of Malvaceae-Malvoideae, with circular outline, central culinder with eustelic struture, continuous, however, the presence the sclerenchymatic pericycle is not common to all genera. The applied histochemical tests evidenced the presence of lignina, cutin, as well as demonstrated a positive reaction for starch, phenolic compounds and mucilage. The foliar anatomical characters of he species studied presente degrees of differentiaon for the diagnosis and separation of taxa, and can be used as na additional resource to taxonomic studies.