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Developmental and Structural Section

Soule, Jacob W. [1], Holtsford, Timothy P. [2].

Functional Changes in the Mating System of N. longiflora: Development and Timing.

We studied floral development of three size morphs descended from a natural population that contained N. longiflora, N. plumbaginifolia and a putative hybrid in order to describe the developmental changes that give rise to the self-fertilization. Long corolla plants (N. longiflora) are facultative outcrossers, while plants with short corollas (N. plumbaginifolia) are autogamous, and plants with medium corollas (hybrids) vary in their selfing rate, but it is intermediate. Mature inflorescences were collected, buds dissected, and floral measurements taken. Due to the destructive nature of sampling, growth rates and Plastichron Index had to be measured on later inflorescences. Long and medium morphs shared similar development for most floral characters, with short morphs differing from both for all characters measured. The time to anther dehiscence was the only trait that differed between long and medium, it was shorter in medium and similar to short. Anther Stigma Distance (ASD) is a good predictor of tendency to self but that correlation has little predictive power on the variation within a morph. When ASD is considered at time of anther dehiscence, it is much shorter in the medium plants which have a higher rate of selfing than long plants. The evolution of a higher selfing rate in medium plants does not appear to have come about due to changes in the growth of floral organs but instead from a change in the timing of the initiation of male phase. The differential development of N. plumbaginifolia indicates a possible independent origin of shorter corollas, suggesting medium morphs may not be hybrids, but instead shorter N. longiflora.


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1 - University of Missouri - Columbia, Division of Biological Sciences, 202 Tucker Hall, Columbia, Missouri, 65201, USA
2 - University of Missouri-Columbia, Biological Sciences, 105 Tucker Hall, Columbia, Missouri, 65211, USA

Keywords:
Nicotiana
Mating system
self-fertilization.

Presentation Type: Poster
Session: 33-17
Location: Salon C, D & E - Gov Ballroom/Hilton
Date: Tuesday, August 16th, 2005
Time: 12:30 PM
Abstract ID:455


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