Journal Article

False paracarpy in <i>Seemannaralia</i> (Araliaceae): from bilocular ovary to unilocular fruit

Alexei A. Oskolski, Dmitry D. Sokoloff and Ben-Erik Van Wyk

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 106, issue 1, pages 29-36
Published in print July 2010 | ISSN: 0305-7364
Published online May 2010 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcq084
False paracarpy in Seemannaralia (Araliaceae): from bilocular ovary to unilocular fruit

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  • Ecology and Conservation
  • Evolutionary Biology
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Background and Aims

Seemannaralia appears to be fundamentally different from all other Araliaceae in the presence of a well-developed symplicate zone in its gynoecium, as well as in the ovule insertion in the symplicate zone (rather than in the cross-zone). The present investigation re-examined the floral structure of Seemannaralia with emphasis on the morphology and evolution of its gynoecium.

Methods

Flowers and fruits of Seemannaralia gerrardii at various developmental stages were examined using light microscopy and scanning electron microscopy.

Key Results

Ovaries in the flowers of Seemannaralia are bilocular. Each ovary locule corresponds to a carpel whose ascidiate part is distinctly longer than the plicate part. Each carpel contains one fertile ovule attached to the cross-zone, and one sterile ovule as well. The fruit is unilocular: its central cavity is occupied by a single large seed. In the course of fruit development, the growth of one ovule stops while another ovule develops into the mature seed. When this ovule outgrows the available space in the locule, the septum is ruptured, forming a united cavity of two carpels.

Conclusions

Despite literature data, the synascidiate zone is well developed in the gynoecium of Seemannaralia, and the ovules are attached to the cross-zone. Its preanthetic and anthetic gynoecium has nearly the same structure as gynoecia of most other Araliaceae. The Seemannaralia fruit resembles the paracarpous gynoecium but its ground plan is very different because the central cavity is formed by mechanical rupture of the septum. The term ‘pseudoparacarpy’ (‘false paracarpy’) is proposed to describe this condition, which has not been reported to date for indehiscent fruits in any taxa other than Seemannaralia. In this genus, the pseudoparacarpy has probably resulted from a decrease in seed number in the course of the transition from zoochory to anemochory.

Keywords: Anatomy; Apiales; Araliaceae; development; flower; fruit; gynoecium; paracarpy; Seemannaralia gerrardii; syncarpy

Journal Article.  3728 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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