Developmental and Structural Section
Pesacreta, Thomas .
Can root ultrastructure be used to define gymnosperms?
Chauveaud (1902) discovered and named the precursory phloem in gymnosperm roots. This cell type is located in the primary phloem. Chaveaud, using the microscopes available to him, believed that it represented a transitional stage between parenchyma and sieve cells. Subsequent ultrastructural examination of Chamaecyparis obtusa indicated that was not the case and therefore the cell type name of peripheral phloem parenchyma was proposed. To broaden our understanding of this cell type several other gymnosperms, basal angiosperms, a sphenopsid, and ferns have been examined. Although only a restricted number of species have been examined thus far it has been determined that the microfilament-rich peripheral phloem is present only in gymnosperms. These observations, if found to be the general case, could indicate that peripheral phloem evolved only in gymnosperms and therefore is most likely to not a transitional cell type but rather a unique and highly specialized one.
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1 - University of Louisiana at Lafayette, Microscopy Center, P.O. Box 42451, Lafayette, LA, 70504, USA
Presentation Type: Poster:Posters for BSA Sections
Location: Event Tent/Cliff Lodge
Date: Tuesday, July 28th, 2009
Time: 5:30 PM