Anatomia foliar de Chamaecrista Moench. (Leguminosae-Caesalpinioideae) como subdídio à taxonomia e à filogenia

• Autor(a) principal: Francino, Dayana Maria Teodoro
• Data de Publicação: 2010
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/379
• topic: Folhas - Anatomia; Leguminosae - Caesalpinioideae - Classificação; Botânica; Histoquímica; Biologia - Classificação; Secreção; Leaves - Anatomy; Leguminosae - Caesalpinioideae - Classification; Botany; Histochemistry; Biology - Classification; Secretion; CNPQ::CIENCIAS BIOLOGICAS::BOTANICA

Chamaecrista Moench., one of the largest genera of Leguminosae- Caesalpinioideae (circa 330 spp.), has the East and Midwest areas of Brazil as the area core of diversity. The genus is traditionally divided into six sections: Apoucouita, Absus, Grimaldia, Chamaecrista, Caliciopsis and Xerocalyx, being the sect. Absus with ca. 170 species the biggest one). Absus is subdivided into four subsections: Adenophyllum, Baseophyllum, Otophyllum and Absus. Subsect. Absus has around 160 species which are sorted out into 31 series, a classification poorly supported by morphological characters. Molecular studies support the genus Chamaecrista as a monophyletic group; however, at the infrageneric level of section, the genus is paraphyletic. Nowadays, additional tools to the molecular phylogeny have been sought, and anatomical studies have been shown to be promising as a source of additional characters aiming to aid on the taxonomy and phylogeny. The present study aims to anatomically characterize the leaves of 55 species of Chamaecrista as well as to evaluate the importance of the anatomical characters as subsides to the taxonomy and phylogeny of this genus. This study also aims to characterize the extrafloral nectaries (EFNs) of Chamaecrista desvauxii var. langsdorfii and Ch. debilis as well as to detect the presence of glucose in the exudates. Samples from voucher material and plants collected in the field were processed according to ordinary plant anatomy techniques for the structural characterization. For the development stages of the extrafloral nectaries, samples from the petiole at different development stages were used. Multivariate statistical methods such as Principal components analysis (PCA) and cluster analysis were applied on the interpretation of the anatomical characters. Analyses of maximum parsimony compared with molecular phylogeny were carried out for the species that had already been included in the molecular phylogeny. The following xeromorphic characters were common among the Chamaecrista species studied: isobilateral leaves, compact mesophyll, pubescence, high vein density, abundance of mechanical tissue, and epidermal cells with thick outer periclinal walls. All these characters represent adaptation of the species to rock outcrops (rocky fields) environments. The phenetic analysis partially corroborates with the classification of the genus Chamaecrista, especially at the sectional and sub-sectional levels. The anatomical characters that stand out on the outlining of the subgroups are: presence of secretory trichomes on reproductive, diameter of the secretory head of the trichomes, morphology of the midvein, mucilage cells, distribution of non-glandular trichomes, stomata distribution, presence and type of secretory structures, and pattern of venation. The results achieved corroborate with the molecular phylogeny which suggests the elevation of subsect. Baseophyllum to a section status, and the relocation of the single species in the sect. Grimaldia to the section Absus. The anatomical data also showed that the serial classification within sect. Absus is artificial, and additional studies combining taxonomic and phylogenetic researches, morphological or molecular, for a better outlining and understanding of the relationships at the infrageneric level are needed. The petiolar secretory structures of Chamaecrista desvauxii var. langsdorfii and Ch. debilis are extrafloral nectaries as showed by the anatomical structure, presence of glucose in the secretion, and histochemical results confirming the presence of carbohydrates in se secretory cells. The extrafloral nectaries of both species show a single-layered epidermis, and three internal areas: secretory subepidermal area, vascularization formed by phloem and xylem, and the parenchymatic area around the vascularization. The EFNs arise from the protoderm, ground meristem, andprocambium, starting the secretory activity in the early stages, before the full leaf expansion. The beginning of the development is characterized by the increase in the volume of the protodermal cells and intense mitotic activity of the protoderm and subjacent ground meristem. The EFNs of both species are similar to what is described in the literature for other Caesalpinioideae species. The description of nectary development for the genus Chamaecrista is a novelty, and the results achieved are meaningful for taxonomic studies in Chamaecrista.