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Abstract Detail

Systematics Section/ASPT

Bachelier, Julien B. [1], Matthews, Merran L. [2].

Flower structure and morphology in Dipentodon sinensis and their implication for the systematics of Dipentodontaceae (Huerteales).

The monotypic genus Dipentodon was originally described and named after the characteristic saw-toothed perianth of its flowers, but its affinities and systematic position were uncertain. Initially, it was placed in Celastraceae because it shared some floral and fruit features with a few genera, such as Perrottetia. However, it fitted poorly with most other members of the family and later, Dipentodon was treated as a distinct family in Rosales or as a member of the catch-all Flacourtiaceae. Recently, molecular phylogenetic studies revealed that Dipentodon is indeed related to Perrottetia, and that together as Dipentodontaceae, they form a robust pair nested in the newly erected order, Huertaeales. A previous comparative study of the flowers in Celastrales already found that Perrottetia fitted poorly in this group, but no alternative placement was given. Its previous relationship with Dipentodon and their entirely new affinities within the Huerteales have thus to be re-considered and tested from a comparative structural and developmental point of view. Preliminary results from serial microtome sections and SEM studies confirm that the flowers of Dipentodon share a number of features with Perrottetia. They are (relatively) small, morphologically bisexual, haplostemonous, and nectariferous. Moreover, their perianth and androecium are mostly pentamerous, and even when they are not, there are usually as many sepals as petals and stamens. Also, in both genera, sepals and petals are poorly differentiated from each other and appear very similar in shape and size. Sepal bases are typically united to form a short floral cup, and their free tips form the teeth that originally gave the name to Dipentodon. Stamens are antesepalous and alternate with five antepetalous hairy nectary lobes. The gynoecium is trimerous in Dipentodon and dimerous in Perrottetia, but in both genera, it is mostly syncarpous with free carpel tips. The ovary is also slightly inferior and almost entirely symplicate, and only at its base is it shortly synascidiate. In each genus, the locule has a dorsal apical septum, and a basal placenta with two crassinucellate and bitegmic syntropous ovules. Together, the flowers of Dipentodon and Perottetia fit well in Huerteales, although a number of features that they share with the other members of the order are typical of many generalist insect-pollinated flowers (i.e., small nectariferous flowers with radial symmetry). However, the presence of antepetalous nectariferous lobes and a basal placentation are unique to Dipentodon and Perrottetia, and provide good support for their closer relationships within Huertaeales.

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1 - SUNY Oswego, Department of Biological Sciences, 7060 Route 104, Oswego, NY, 13126-3599, USA
2 - Phytax GmbH, Wagistrasse 23, Schlieren , 8952 , Switzerland

comparative morphology
floral nectaries
floral symmetry
syncarpous gynoecium

Presentation Type: Oral Paper:Papers for Sections
Session: 14
Location: Cottonwoods North/Boise Centre
Date: Monday, July 28th, 2014
Time: 4:15 PM
Number: 14011
Abstract ID:164
Candidate for Awards:None

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