Developmental and Structural Section
Christianson, Michael L. , Jernstedt, Judy .
Ginkgo: 70 years after Foster's description of its apex.
One recurring dilemma in evolutionary biology is reconciling apparently discontinuous phenomena with the small, incremental, changes central to traditional Darwinian explanations. The transition between the single-apical-cell apical meristems in the early-divergent vascular plants and the tunica-corpus structure of the shoot apex in angiosperms is in many ways as an abominable a mystery as Darwin’s classic example. The gymnosperms (non-angiosperm seed plants), of course, sample this transition in apical structure. Description of gymnosperm “zonate apices” is based on anatomical/histological observation and inference of how one population of cells replenishes cells in other locations in the meristem. It was 70 years between Hanstein’s proposal of layered histogens in the angiosperm apex and Satina’s use of colchicine to show that the layers actually acted like layers. It is now 70 years after Foster’s 1938 description of Ginkgo, and high time to recover polyploid sectors in colchicine-treated apices of Ginkgo to document the cellular dynamics in this classic example of a zonate meristem. We are particularly interested in what clues clonal analyses of the Ginkgo SAM provide for understanding meristem organization and dynamics relative to organogenesis. The immediate question is whether Ginkgo leaves and leaf homologues arise within or across clonal boundaries. (Supported in part by the Grady L. Webster Memorial Fund.)
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1 - University of California, Davis, Plant Sciences, Mail Stop 1, One Shields Avenue, Davis, CA, 95616
2 - University of California, Davis, Plant Sciences, One Shields Avenue, Davis, California, 95616-8780, USA
shoot apical meristem
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, July 29th, 2008
Time: 4:45 PM