Caracterização da morfologia floral e da embriologia de espécies de Dyckia Schult. F. (pitcairnioideae - bromeliaceae)

Abstract

Bromeliaceae is a Neotropical family that presents enormous richness and adaptability in diverse environments; currently has about 3539 species grouped in eight subfamilies, among them Pitcairnioideae, which includes the genus Dyckia with more than 170 species. The present study had as main objectives to present a morphological analysis of the stamens in Dyckia ibicuiensis, D. polyclada LB Sm. and D. racinae LB Sm., and to describe and analyze aspects of the ginosporogenesis and the ginogametogenesis of D. ibicuiensis Strehl, including details cytological and histological findings of the ginosporângio. Considering that D. ibicuiensis is critically endangered and D. polyclada and D. racinae are in the category of insufficient data, since they do not present sufficient information to evaluate the extinction risk, the present work becomes fundamental both for better description conservation of the species. The botanical material was analyzed and processed in the Laboratório de Botânica Estrutural (LABOTE) of the Departamento de Biologia, Centro de Ciências Naturais e Exatas at the universidade federal de Santa Maria CCNE / UFSM. Flower collections and buds were carried out in the municipalities of Santa Maria and São Pedro do Sul, RS, Brazil. Morphometric analyzes of stamens were performed in random individuals, for the analysis of fibrous thickenings, the maceration of the anthers was made using a 3: 1 solution of hydrogen peroxide and glacial acetic acid. For analysis in optical microscopy the botanical material was processed according to the usual techniques for the same, it was also made analysis in fluorescence microscopy and differential and interferential contrast. To perform the histochemical tests were used: Ruthenium Red for acidic and acidic mucopolysaccharides, Aniline Blue, for cucumber, under fluorescence and Calcofluor White, in aqueous solution 0.01% for cellulose. Morphologically, the androecium of these species is differentiated by the arrangement of the stamens around the gynoecium and by the general characteristics of the anther. Stamens included, with anastomosis filaments different from the forefoot, anthers with a radial disposition around the gynoecium with curved sporangia always facing the same characterize D. ibicuiensis and D. racinae. This configuration results from fillet coning as well as special anatomical features of the anthers, such as the connective thickenings. In addition, these species are differentiated by U-shaped thickening in endothecium. Dyckia polyclada is characterized by its small, free and exserted stamens, with a very short common tube, its anthers, which are not curved or organized around the gynoecium. With the results of the gynoecium studies, it was observed that D. ibicuiensis has a superior ovary, tricarpelatte, trilocular, plurispermic with axial placentation; the stigma is triplicate of the conduplicated type spiral; the ovules are anatropous, bitegmic and crassinucellate; the integuments are of dermal origin; outer tegument is vascularized; the micropillar canal is formed by the inner integument; the gametophyte is of monosporic origin and Polygonum-type; the fibrillar apparatus is from pectic composition; septal nectaries are infralocular, labyrinthic; the chalazal appendix presents elongated cells with intracellular spaces and the obturator presents dome-shaped elongate cells and dense and vacuolated cytoplasm, covering the entire placental region. The presence of secondary metabolites in the nucelo cells was observed during meiosis, persisting during development of the gynophyte. Another striking feature in meiosis was the absence of callose around the spores during meiosis, a characteristic that has never been observed in family species. The data presented are unpublished for the species and contribute to the understanding of the taxonomic and phylogenetic relationships within the family, and for a better understanding of the reproductive process of the species as well as the delimitation of Dyckia be equally important for other species and infrageneric groupings.