Paleobotany in the Post-Genomics Era
Endress, Peter K. .
Floral structure and evolution - what can palaeobotanists and neobotanists learn from each other?
NEOBOTANISTS are able to study whole living plants and their development but are restricted to the present time, in contrast palaeobotanists are not restricted in time but mostly have only fragments of plants and single developmental stages at their disposal. Both can mutually profit from complementary experience. The shape of floral fragments may allow inferences on the floral architecture. Cuneate anthers with a massive sterile apex indicate contiguity in bud and a protective function of the apex, either in dense heads of many flowers with reduced perianth (Platanaceae, Altingiaceae) or single flowers in which the many stamens are exposed in late bud (Annonaceae). Sepal flanks exposed in bud may differ from those that are covered in bud in being thicker and hairy. Proportions of the gynoecium can greatly change during development, e.g. in Fagales two developmental processes must be considered: (1) basal intercalary growth, which seemingly "lifts" the placenta to the ovary top, and (2) decay of tissue of the inner ovary wall, which isolates the seed-serving vascular bundle from the tissue of the decaying septum and thus gives the false impression of a basal placenta and unilocular ovary. Also in Fagales, sepal size reduction and loss of protective function may result in increase and lability in number and irregular formation of narrow organs. Thus it may be difficult to establish a basic merism of the perianth in such flowers. Conversely, for evolutionary interpretations of extant flowers consideration of fossil structures is likewise important. Most early fossil flowers are much smaller than extant flowers of related clades. Elaborations of extant flowers may be expressed even more in early fossils, such as the staminal appendages in calycanthaceous flowers.
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1 - Universität Zürich, Institut für Systematische Botanik, Zollikerstrasse 107, Zürich, CH-8008, Schweiz
Presentation Type: Symposium or Colloquium Presentation
Date: Wednesday, August 2nd, 2006
Time: 8:45 AM