eMonocot Cyperaceae

an authoritative resource for Cyperaceae data worldwide, integrating global and regional perspectives

Cytotaxonomic studies in Brazilian Rhynchospora (Cyperaceae), a genus exhibiting holocentric chromosomes

Publication Type:Journal Article
Year of Publication:1998
Authors:Luceño, M., Vanzela, A. L. L., Guerra M.
Journal:Canadian Journal of Botany-Revue Canadienne De Botanique
Keywords:Carex, CRYPTOCARPAE, Cyperaceae, evolution, genera, holocentric chromosomes, NORTHEASTERN NORTH-AMERICA, polyploidy, Rhynchospora

The genus Rhynchospora (Cyperaceae) is a widely distributed Brazilian group, with approximately 150 species. We have studied mitosis and (or) meiosis of 16 species of four sections (Dichromena, Longirostres, Polycephalae, and Pluriflorae). The results showed high frequencies of chromosome number multiples of x = 5, which is the probable basic number. Polyploidy, in contrast to agmatoploidy and (or) symploidy, seems to be the predominant cytogenetic mechanism in the evolution of the karyotype. Primary constrictions were not visible in the chromosomes, suggesting a holocentric condition, as observed in other genera of this family. Karyotype interspecific differences were useful in the cytotaxonomic analysis in three sections. Our data propose (i) the separation of Rhynchospora ciliata (Vahl.) Kukenth, from Rhynchospora nervosa (Vahl.) Bockeler (section Dichromena), (ii) the inclusion of Rhynchospora legrandii Kukenth, ex Barros as a subspecies of Rhynchospora corymbosa (L.) Britton (section Longirostres), and (iii) a suggestion for the organization of section Pluriflorae.

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