Developmental and Structural Section
Meloche, Christopher G. , Vaughn, Kevin C. .
Gelatinous Fibers are Critical in Coiling of Tendrils and Twining of Vines.
THE survival of many climbing plants is dependent upon the ability of a twining stem or tendril to tightly grasp a support. In order to achieve secure attachment by twining it must assume a coiled shape with a natural diameter smaller than that of the support. In cytochemical and immuno-cytochemical studies of the tendrils of Passiflora incarnata, Echinocystis lobata, Smilax rotundifolia and Brunnicia ovata as well as twining stems of Ipomoea muricata and Ipomea hederacea fiber formation was found coincident with twining behavior. These fibers have composition and organization unlike typical fibers, and are most similar to the gelatinous fibers of tension wood. The fiber cell wall consists of a primary wall/middle lamellae complex, two thick S layers, and a gelatinous layer immediately adjacent to the plasmalemma. This gelatinous layer is enriched in cellulose and rhamnogalacturonans relative to the more typical S layers which are rich in callose, xylans and lignins and impoverished in pectins of all types. Orientation of the cellulose microfibrils in the secondary walls is similar to that reported for other gelatinous fibers. However changes in orientation occur with twining. We propose that the compositional and organizational differences between the G and S layers allow for a differential swelling, giving rise to a tension that causes a twisting in the fiber cell and consequently in the twining organ as a whole. Variations in the extent of lignification(higher towards the touched side) of the primary wall and S layers would allow for subtle changes in the extent of twisting of a given fiber cell. Taken to the organ level, this allows tendrils the structural flexibility to twine about objects of many different sizes and morphologies. Not all vines use this strategy for causing coiled stems or tendrils, but this appears to be a major and highly succesful strategy.
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1 - USDA-ARS, Southern Weed Science Research Unit, Stoneville, Mississippi, 38776, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 312/Bell Memorial Union
Date: Monday, July 31st, 2006
Time: 3:30 PM