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Título de Acceso Abierto
Estudios morfo-anatómicos, cromosómicos y palinológicos en especies de Stemodia (Scrophulariaceae)
María de las Mercedes Sosa Aveliano Fernández Gabriel Bernardello
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Resumen/Descripción – provisto por el repositorio digital
Stemodia L. is a genus with 49 species, belonging to the Scrophulariaceae family. In South America this genus is very well represented whit a total of 20 species. In some South American species its great morphologic variability makes difficult its identification and the limits with related species are not always clearly defined. In the present study the taxonomic and systematic significance of morphological, anatomical, chromosomal, and palynological characters is evaluated. The exomorphologic analysis permitted the selection of valid characters to elaborate a key for the identification of the species. The anatomical study revealed the existence of characters that can be useful for their differentiation both in leaf and in stem. The useful anatomical characters of the leaves to differentiate the species are: the anticlinal walls of the epidermical cells, types of trichomes, types of stomata and the mesophyll structure. The fundamental difference was observed in the stem, in characters such as the contour of the stem, the presence or absence of aerenchyma, collenchyma and medullar lagoon. On the basis of these differences a key for the identification was elaborated to differentiate the species studied. All the studied species showed basic chromosome number x = 11, with three ploidy levels in Stemodia hyptoides. A high percentage of pollen fertility was observed. The karyotypes of the species of Stemodia presented in this thesis constitute the first report for the genus. The similarity of the karyotypic formula between the diploids and the polyploids taxa suggests that they probably would not have experience greated structural changes during the diversification of the species. Morpho-anatomical studies were carried out in Stemodia hyptoides because of three different levels of ploidy were registered. The results obtained here indicate that most morphologic variation should be produced by the “gigas” effect; which communly occurrs in polyploids. Because of the diploid populations of S. hyptoides resemble morphologically to S. stricta, morpho-anatomical characters of both species were analyzed comparatively. The statistical analysis demonstrated that an important number of features allow to differentiate both species. The palynological studies performed in Stemodia species shows a high homogeneity in the characters evaluated. They suggest that the genus is stenopalynous, although small differences in some species as in shape and size are observed. The obtained results reveal that polyploidy would have been one of the mechanisms that have contributed to the evolution of Stemodia. This has produced a great variability in some species making difficult its taxonomic identification, since the species with the different ploidy levels are morphologically more variable than the species with 2n=22.Palabras clave – provistas por el repositorio digital
Estudios morfo-anatómicos; Estudios cromosómicos; Estudios palinológicos
Disponibilidad
| Institución detectada | Año de publicación | Navegá | Descargá | Solicitá |
|---|---|---|---|---|
| No requiere | 2009 | Repositorio Institucional de la Universidad Nacional del Nordeste (SNRD) |
|
Información
Tipo de recurso:
tesis
Idiomas de la publicación
- español castellano
País de edición
Argentina
Fecha de publicación
2009
Información sobre licencias CC
