Recent Topics Posters
Fowler, Tiffany B. , Rushing, Ann .
Early periderm development in the shoots of Ulmus alata Michx.
Ulmus alata produces a protective periderm that replaces a trichome-covered epidermis during the first year of stem growth. Investigations using scanning electron microscopy reveal the periderm is initiated from cortical cells located directly beneath the epidermis within only a few days of growth of a new stem segment or branch. These cells, termed phellogen, eventually form a continuous layer around the circumference of the stem and divide to produce one layer of phelloderm and 4-7 layers of phellem. At this stage, the formation of winged extensions of the periderm is initiated by uneven enlargement of cells in localized regions of these peridermal layers. It appears that radial expansion of existing cork cells initiates wing formation. Expansion of these cork cells results in a protrusion that often ruptures the original epidermis early in development. Additional layers are added to the wing by normal cell divisions in the phellogen followed by radial expansion of the newly produced cells. During formation of the winged extensions of the periderm, the phellogen does not appear to be active in the remainder of the stem. Typically, wings are oriented laterally on opposite sides of the stem, although additional wings may be produced in the same areas.
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1 - Baylor University, Department of Biology, Waco, Texas, 76798-7388, USA
Ulmus alata .
Presentation Type: Recent Topics Poster
Location: Salon C, D & E - Gov Ballroom/Hilton
Date: Tuesday, August 16th, 2005
Time: 12:30 PM