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Acta Botanica Brasilica

Print version ISSN 0102-3306On-line version ISSN 1677-941X


FIGUEIREDO, Rogério da Costa et al. Development of carpels and ovules in Dialypetalanthus fuscescens Kuhlm. (Rubiaceae): an enigmatic taxon. Acta Bot. Bras. [online]. 2017, vol.31, n.1, pp.128-133. ISSN 0102-3306.

Dialypetalanthus is a monospecific genus that occurs in the Amazon Basin of Brazil, Bolivia and Peru and occupies a controversial position among the Rubiaceae. We continue this taxonomic discussion with the overall aim of clarifying the systematic position of D. fuscescens within the Rubiaceae. To accomplish this, we analyzed the ontogeny of its gynoecium, in particular the floral meristem, as well as the development of the carpels and cauline placentation. Gynosporogenesis and the differentiation of the carpellary septa and ovules were also described. Dialypetalanthus fuscescens was classified according to evolutionary diagrams found in the literature. The following characteristics were observed in D. fuscescens: 1) permanence of the floral meristem in the central basal part of the early flower bud; 2) dual origin of carpellary septum; 3) trizonate ovular primordia with only one fertile gynospore per ovule; and 4) cellular proliferation in the chalazal region. Embryological results confirm the classification of D. fuscescens in the subfamily Ixoroideae. These results are distinct from any others previously proposed in the evolutionary diagram. Therefore, we conclude that this study has presented evidence strongly suggesting that Dialypetalanthus possesses new morphological-type of ovule we refer to as the Dialypetalanthus-type.

Keywords : carpel development; carpellary septum; cauline placentation; floral meristem, ovule.

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