Anatomia foliar de espécies de Flacourtiaceae (Sleumer 1980) / Foliar anatomy from species of Flacourtiaceae (Sleumer 1980)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

There is no agreement regarding the taxonomic organization of the Flacourtiaceae and the theme is not emphasized in the literature, since there is a lack of taxonomic studies on this family. Several authors point out the close relationship between the families Flacourtiaceae and Salicaceae. Numerous families of plants have members with medicinal uses, standing out among them the Flacourtiaceae, mainly the genera Casearia and Carpotroche. Extensive investigations have emphasized the therapeutic properties of Casearia species related with compounds secreted by specialized structures in the leaves. The study of the chemical composition of secretory products together with anatomic studies of secretory structures can contribute to understand the role and function of these products in the plant, besides being an important component for taxonomic evaluations. Considering the importance of anatomy as subsidy for taxonomy, family data are fundamental to elucidate taxonomic problems. The objectives of this work were to characterize anatomically leaves of Abatia, Banara, Carpotroche, Casearia, Prockia and Xylosma species occurring in forest fragments of Zona da Mata - Minas Gerais and to evaluate the importance of anatomical characters for species identification; to characterize anatomical and histochemically secretory structures present in leaves of Prockia crucis and Casearia decandra, correlating with the chemical composition of the product secreted by the former; to describe the micromorphology and anatomy of Prockia crucis secretory glands. Leaves of members of the genera Abatia, Banara, Carpotroche, Casearia, Prockia and Xylosma were collected from three forest fragments in the municipality of Viçosa (MG) and from an altitude field in the Serra do Brigadeiro State Park (MG) and subjected to usual techniques used in plant anatomy. Casearia decandra and Prockia crucis were also histochemically tested. Eleven species were anatomically described, giving emphasis on their differences and similarities. In this work, it was possible to confirm some unifying characters for the families Flacourtiaceae and Salicaceae such as the presence of salicoid leaf teeth, simple unbranched unicellular trichomes, branched multicellular trichomes, brachyparacitic stomata, secondary growth of the petiole, crystal abundance, collateral and arch-shaped vascular system at the midrib, dorsiventral mesophyll and sclerenchyma accompanying the bundles. The anatomic studies carried out on Flacourtiaceae species demonstrated that leaf anatomy can provide data to assist in the family taxonomy, at both generic and specific levels. The secretory system of C. decandra consists of ducts and cavities dispersed on the leaf lamina and petiole and idioblasts present in the vascular tissues, cortical parenchyma of the midrib and in the palisade parenchyma. The ducts are distributed in the cortical parenchyma of the rib and continue in this same region of the petiole. In the mesophyll there are numerous cavities in the subepidermic layer or distributed in the interface between the palisade and spongy parenchyma. Lipophilic and hydrophilic substances were detected, confirming oil-resin lipids within ducts and cavities, and phenolic compounds, of the tannin type, within idioblasts and parenchyma. Alkaloids, polysaccharides and proteins were not detected. This work reported the presence of ducts and cavities for the genus Casearia. Histochemical tests confirm the secretory product complexity, besides indicating fundamental tissues such as sites of synthesis and/or accumulation of phenolic compounds. Fructose, glucose and sucrose were detected in the product of secretory structures of Prockia cruces, with sugar concentration being 49.6% of the total secretory product. Glands were identified as extrafloral nectaries (EFNs), which is the first report of their presence in the genus. The produced nectar has a high energy value. EFNs occur in the basal and marginal regions of the leaf, they are sessile, circular and have a central concavity. The epidermis covering the concavity is secretory, unistratified, forming a palisade layer of cells that reacted strongly positively after staining with Schiffs reagent and Xylidine Ponceau, confirming neutral polysaccharides and proteins, respectively. The nectary parenchyma presented cells with granular cytoplasm that reacted to the test for phenolic compounds. This parenchyma is interrupted by vascular extensions which ramify. The development of nectaries begins very early, in the leaf primordiums of the apical meristem, being totally differentiated in the expanding leaves. Due to their similarity with the salicoid leaf teeth present in Populus and Salix, it is suggested that such clades are phylogenetically close.

ASSUNTO(S)

casearia anatomia vegetal abatia xylosma prockia banara carpotroche banara prockia xylosma casearia abatia carpotroche

ACESSO AO ARTIGO

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