Style morphological diversity of some Asteraceae species from Argentina: systematic and functional implications
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Stylar micromorphological diversity of 42 Asteraceae species from Argentina was analysed considering species phylogenetic membership and some floral reproductive functions (pollen presentation and pollen reception). In particular, the morphology and organisation of pollen presenter (sweeping hairs) and pollen receptive structures (stigmatic papillae) were described. Results showed that style morphology of the studied species is far more diverse than the categories previously established for Asteraceae, and that it is problematic to relate the sweeping-hair arrangement of species to the only three modes of pollen presentation described for the family, indicating that the hypothesised relationship could be more complex than was formerly thought. For all species with di- or trimorphic florets, the styles of female florets were more slender and without or with more reduced sweeping hairs than the styles of hermaphrodite florets, and divergences of sweeping hair arrangements and morphology were higher among phylogenetically related species. These results suggest that functional aspects of floral morphology seem to be more important than phylogenetic constraints as selective forces determining stylar pollen presentation structures. In contrast, stigmatic-area organisation as well as the morphology of stigmatic papillae remain identical between female and hermaphrodite florets and among phylogenetically related species. Thus, stigmatic papilla morphology seems to be a phylogenetically constrained character in the studied species.
KeywordsAsteraceae SEM micrographs Stigmatic-area organisation Stigmatic papillae Sweeping hairs
We thank Peter Leins, Claudia Erbar and Ramiro Aguilar for useful comments on early versions of this manuscript, and Gerardo Robledo, Ana María González and Ricardo Munch for technical support in SEM micrographs. The study was supported by “Consejo Nacional de Investigaciones Científicas y Técnicas”(CONICET), “Agencia Nacional de Promoción Científica y Tecnológica”, “Secretaría de Ciencia y Tecnología de la Universidad Nacional de Córdoba”, and “Agencia Córdoba Ciencia”. Thanks are due to “Consejo de Investigaciones Científicas y Técnicas de la Provincia de Córdoba” and the “Academia Nacional de Ciencias Exactas, Físicas y Naturales” for the fellowships to the first author. C.T. and L.G. are members of CONICET.
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