Estudos morfoanatômicos em Campomanesia Ruiz et Pav. (Myrtaceae)

Abstract

Myrtaceae is a family of great importance to Brazilian flora, and all its Brazilian representatives are included in the Myrteae tribe, recently divided into seven informal groups, among which is the Pimenta group, to which belongs Campomanesia Ruiz & Pav. This genre is well delimited, however, with some infraspecific conflicts. The present work aimed to contribute to the taxonomy of the species of Campomanesia, comparing morphology and anatomy, fully developed leaves of C. xanthocarpa (Mart.) O.Berg and C. guaviroba (DC.) Kiaersk., in addition to comparing the morphology and anatomy of well developed leaves and apical stem of C. guazumifolia (Cambess.) O.Berg, with corresponding organs in its seedlings. For this, branches with leaves, stem and fruits were collected in Atlantic Forest, specifically in Semideciduous Seasonal Forest, and analyzed morphologically. For structural analyzes, histological slides were made, as well as samples for scanning electron microscopy and histochemical tests. The results showed a considerable phenotypic plasticity in C. xanthocarpa, being possible to subdivide into seven leaf morphotypes. They are characteristics common to the two species examined: unstrained epidermis, single unicellular trichomes, hypoestomatic leaves with anomocytic and paracytic stomata, secretory cavities on both faces, dorsiventral mesophyll, median rib and petiole with bicollateral vascular bundles. The histochemical composition is also very similar, with presence of phenolic compounds, starch, lipid compounds in secretory cavities and idioblasts containing drusen and prismatic crystals of calcium oxalate. However, C. guaviroba presents a standard format in the epidermal cells, which are isodiametric and have little sinuous walls on both faces. Its epidermal secretory cavities presented a pair of ceiling cells with medial walls of straight contour on the adaxial side. In addition, the presence of a layer of collecting cells between the palisade and spongy parenchyma, in the mesophyll. With the exception of the collecting cells, similar characteristics were observed only in the morphotypes 5, 6 and 7 of C. xanthocarpa. The other morphotypes of C. xanthocarpa presented greater sinuosity in the walls of epidermal cells. As for the secretory cavities, the cells surrounding these structures form a well-evident disk and the median contour between the ceiling cells is very sinuous on both faces. C. guazumifolia presents embryo in the form of "C" and seedlings epigeous phanerocotyledonal. The data obtained showed anatomical and histochemical similarities between adult leaves, paracotyledons and eophylls, besides anatomical similarity between the apical stem and the epicotyl. The photosynthetic structures of the seedlings present many characteristics of the adult leaves, such as paractic stomata, large crystaliferous idioblasts, few secretory cavities in the mesophyll, and collecting cells among the parenchyma. In this way, the results showed that the boundaries between the first two species are very tenuous, but epidermal characters can contribute to differentiate them. The morphological and histochemical description of the photosynthetic and stem parts of the C. guazumifolia seedlings, very much resembles that of the leaves and apical stem of adult individuals, therefore, it proved useful for the taxonomy of the species.