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ARS Home » Southeast Area » Stoneville, Mississippi » Crop Production Systems Research » Research » Publications at this Location » Publication #187837
Title: A CORTICAL BAND OF GELATINOUS FIBERS CAUSES THE COILING OF REDVINE TENDRILS: A MODEL BASED UPON STRUCTURAL AND IMMUNOCYTOCHEMICAL STUDIES

Author
item Meloche, Christopher
item KNOX, J - UNIV LEEDS, LEEDS, UK
item Vaughn, Kevin

Submitted to: Planta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/18/2006
Publication Date: 1/8/2007
Citation: Meloche, C.G., Knox, J.P., Vaughn, K.C. 2007. A cortical band of gelatinous fibers causes the coiling of redvine tendrils: a model based upon structural and immunocytochemical studies. Planta 225:485-498.

Interpretive Summary: Redvine is one of the most troublesome of the weedy vines but little is known about the way this plant grows in order to control it. In this study, we investigated a mechanism by which the redvine tendrils are able to coil. We found a type of fiber cell previously found only in tree limbs that are weighted down and return to their position after mechanical damage. We propose that these fibers cause the tendrils coil. Further, we have found that these fibers are unique in composition and, as such, might be potential sites for chemical control measures.

Technical Abstract: A cortical band of fiber cells originate de novo in tendrils of redvine when these convert from straight, supple young filaments to stiffened coiled structures in response to touch stimulation. We have analyzed the cell walls of these fibers by in situ localization technioques to determine their composition and possible role(s) in the coiling process. The fiber cell wall consists of a primary cell wall and two lignified secondary wall layers (S1 and S2) and a less lignified gelatinous (G) layer proximal to the plasmalemma. In mature, coiled tendrils the orientation of cellulose microfibrils in the S layers is different from each other but also varies between adjoining fiber cells within the fiber band. However, this orientation difference is not observed prior to coiling. Compositionally, the fibers are sharply distinct from surrounding parenchyma as determined by antibody and affinity probes. The fiber cell walls are highly enriched in cellulose, callose and xylan but contain no homogalacturonan (HG), either esterified or de-esterified. Rhamnogalacturonan-I (RG-I) epitopes are found only in the inner, presumably gelatinous layer, indicating a further restriction of RG-I in the fiber cells as well. The distribution of both callose and extensin in these cells is patchy and diffuse. Lignin is concentrated in the secondary wall layers of the fiber and the compound middle lamellae/ primary cell wall but is absent from the gelatinous layer. The cortical fibers in redvine are the first documented example of gelatinous extraxylary fibers. Our observations indicate that these fibers play a central role in tendril function, not only in stabilizing its final shape after coiling but also generating the tensile strength responsible fore the coiling. We propose a mechanism based upon differential shrinkage/ expansion of the G layer to the other secondary wall layers (more G layer, more potential twist) and control of the degree, timing and placement of lignification (more lignification, less potential for twisting) of the fiber cells to allow a broad range of tendril curvatures so that virtually any structure may be encircled with a tendril.