Plant Development / Développement des plantes (CBA/ABC)
Gerrath, Jean , Guthrie, Theodore , Zitnak, Tim , Posluszny, U .
Development of the axillary bud complex in Echinocystis lobata (Cucurbitaceae).
Tendrils are coiling organs used for climbing and mechanical support. They are present in a number of distantly related angiosperm families and can be modified leaves, stems, inflorescences or roots. Thus they have likely arisen independently several times, and are a good example of convergent evolution. In the Cucurbitaceae, despite investigations over the past hundred years, there is still no unifying interpretation of the morphological origin of the tendrils or branching pattern of the axillary bud complex (ABC) and the tendril has been hypothesized to be homologous to a leaf, a flower, a stem, or a combination of stem and leaf. Echinocystis lobata (wild cucumber) was used as a model to study the early ontogeny of the ABC and the tendril, using epi-illumination microscopy and serial resin sectioning. The ABC produces four structures, beginning proximal to, and ending distal to the subtending leaf: (1) an inflorescence of staminate flowers, (2) a solitary pistillate flower, (3) an axillary bud, and (4) a tendril. There are two bifurcation events of the ABC that result in the above structures. The first event separates the tendril primordium from the continuation of the ABC, and the second event separates the staminate inflorescence and the ABC. The pistillate flower forms between the staminate inflorescence and the axillary bud. A subtending leaf is not involved at any time during these bifurcations. Thus we conclude that the tendril and other organs formed by the ABC are stems (axillary branches), all of the same morphological value.
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1 - University of Northern Iowa, Department of Biology, Cedar Falls, IA, 50614-0421, USA
2 - 1420 Oaklawn Avenue, Iowa City, IA, 52245-5647, USA
3 - University of Guelph, Department of Molecular and Cellular Biology, Guelph, ON, N1G 2W1, Canada
4 - University of Guelph, Molecular and Cellular Biology, Guelph, Ontario, N1G 2W1, Canada
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 28th, 2008
Time: 1:30 PM