Understanding plant evolution: morphology to molecules
Tomlinson, P. Barry .
Rescuing Robert Brown: from gymno-ovuly to angio-ovuly.
Robert Brown (1773-1858) made the observation that the cycads and conifers, because of their gymno-ovulate condition, can be consistently distinguished from the angio-ovulate flowering plants, the distinction applying at the time of pollination. This distinction was immediately obscured by the terms “Angiosperm” and “Gymnosperm”, which implies a later event, seed protection, and which terms were NOT invented by Robert Brown. However, the terms are deeply embedded in the botanical literature and serve their purpose as labels. But we need to rescue Robert Brown’s insightful observation because if one studies conifer reproduction based upon it, one can discern “latent homology” between them and flowering plants in their reproductive behavior. The understanding begins with an appreciation that pollen structure in conifers, which ancestrally begins with saccate pollen, relates to pollen behavior in water and not air and continues with many associated features, some characteristic of flowering plants. Far from being uninteresting in their reproductive biology, conifers provide insights into the gymno-ovulate to angio-ovulate transition similar to that which must have occurred in the later evolution of seed plants. This includes loss of the pollination drop and saccate pollen, the development of a second integument, the need for extended siphonogamy, the beginnings of the “fruit”, the persistence of tectate pollen, and the possible beginnings of pollen/stigma interactions. This approach should substitute discovery for invention in the search for the origins of the flowering plants.
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1 - National Tropical Botanical Garden, The Kampong, Coconut Grove, Florida, 33133, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Room 4/Woodward
Date: Monday, July 28th, 2008
Time: 1:45 PM