Developmental and Structural Section
Zacharias, Elizabeth H. , Tomlinson, P. Barry .
Propellers and pendulums--internodal torsion producing dorsiventrality in plagiotropic axes.
We examined the twisting of internodes in some tropical trees that produces axes with leaves that become inserted in one plane, despite an inherent decussate phyllotaxis. Many woody plants in the tropics with decussate phyllotaxis and typified by Massartís and Roux's models produce orthotropic (erect or trunk) axes with radial symmetry and contrasted plagiotropic (branch) axes with dorsiventral symmetry. Trunk axes simply retain the inherent four-ranked disposition of the leaves which just become horizontal. In plagiotropic axes, however, in order for leaves to become horizontal considerable secondary adjustment of both internode and petiole is necessary. The necessary direction of rotation of the internode could either be constant (a propeller) or alternate from left to right (a pendulum), or be random. We describe a number of examples from unrelated plant families* and have recognized a possible principle that could be adaptive. (* e.g., Araucariaceae, Gnetaceae, Lythraceae, Myrtaceae, Podocarpaceae, Thymeleaceae)
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1 - Harvard University, Department of Organismal and Evoloutionary Biology, 22 Divinity Ave., Cambridge, MA, 02138
2 - National Tropical Botanical Garden, The Kampong, 4013 Douglas Rd., Miami, Florida, 33133, USA
Presentation Type: Poster:Posters for BSA Sections
Location: Event Tent/Cliff Lodge
Date: Tuesday, July 28th, 2009
Time: 5:30 PM