Developmental and Structural Section
Dulin, Max , Kirchoff, Bruce K. .
Paedomorphic Secondary Xylem and Secondary Woodiness in Xanthorhiza simplicissima, Coreopsis gigantea, and Mahonia bealei.
We tested Carlquist’s theory of paedomorphosis in the secondary xylem with reference to the wood of three plants that have been hypothesized to be secondarily woody. Quantitative measurements and observations from sections and macerations were done using light and confocal microscopy. The secondary xylem of all three species has a degree of paedomorphosis, with Coreopsis gigantea possessing the greatest degree. Coreopsis gigantea possesses vessel elements whose length either decreases or remains the same across the xylem, vessels with pseudoscalariform lateral wall pitting and simple perforation plates, libriform fibers, and abundant xylary parenchyma. Xanthorhiza simplicissima shows an intermediate degree of paedomorphosis, possesses decreasing vessel element lengths across the xylem, libriform fibers, and upright ray cells. Mahonia bealei has only the paedomorphic characteristics of stable vessel element lengths across the xylem, and libriform fibers. Phylogenetic analysis of literature data indicate that all three species are secondarily woody. The degree of paedomorphosis seems to reflect each species release from mechanical constraints on wood structure.
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1 - University of North Carolina at Greensboro, Department of Biology, PO Box 26170, Greensboro, NC, 27402-6170, USA
xylem structure and function
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Ballroom 3/Cliff Lodge - Level B
Date: Monday, July 27th, 2009
Time: 1:45 PM