Cytotaxonomy of species of Vernonia, section Lepidaploa, group Axilliflorae (Asteraceae, Vernonieae) |
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Authors: | VANESSA MANCUSO DE OLIVEIRA ELIANA R FORNI-MARTINS JOÃO SEMIR |
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Institution: | Laboratório de Biossistemática e Evolução de Plantas do Departamento de Botânica, Instituto de Biologia, CP6109, Universidade Estadual de Campinas, 13083-970, Campinas, SP, Brazil |
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Abstract: | Mitotic chromosomes of eight populations of six species of Vernonia sensu Baker (Asteraceae, Vernonieae, section Lepidaploa , group Axilliflorae ) were studied to assess the validity of maintaining the genus as proposed currently ( sensu Baker) or of splitting it into several smaller genera ( sensu Robinson). The species were collected in areas of 'cerrado' and 'campo rupestre' in southern and central-western Brazil. The chromosome numbers were 2 n = 20–40 and karyotypic analysis showed a predominance of metacentric chromosomes, with some submetacentrics. B chromosomes were seen in one population of V. geminata . The chromosomes varied in length from 0.9 to 4.6 µm, with a total chromatin length of 29.7–45.0 µm and a symmetry index of 41.2–46.9%. The intrachromosomal asymmetry index varied from 0.13 to 0.29, and the interchromosomal asymmetry index varied from 0.15 to 0.21. The dispersion diagram showed that population 1 of V. geminata had the most asymmetrical karyotype. These results do not provide sufficient evidence for a conclusive cytotaxonomic discussion of Vernonia , mainly because of the impossibility of associating any infrageneric group with specific karyotypic characters, and also because of the small number of species analysed so far. © 2007 The Linnean Society of London. Botanical Journal of the Linnean Society , 2007, 154 , 99–108. |
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Keywords: | B chromosomes chromosomes karyotype mitosis |
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