GELATINOUS FIBERS ARE WIDESPREAD IN COILING TENDRILS AND TWINING VINES

Although the coiling of tendrils and the twining of vines has been investigated since Darwin's time, a full understanding of the mechanism(s) of this coiling and twining ability has not yet been obtained. In a previous study (Planta 225: 485-498), gelatinous (G) fibers in tendrils of redvine occurred concomitantly with the ability to coil, strongly indicating their role in the coiling process. In this Study, tendrils and twining vines of a number of species were examined using microscopic and immunocytochemical techniques to determine if a similar presence and distribution of these fibers exists in other plant species. Tendrils that coiled in many different directions had a cylinder of cortical G fibers, similar to redvine. However, tendrils that coiled only in a single direction had gelatinous fibers only along the inner Surface of the coil. In tendrils with adhesive tips, the gelatinous fibers occurred in the central/core region of the tendril. Coiling occurred later in development in these tendrils, after the adhesive pad had attached. In twining stems, G fibers were not observed during the rapid circumnutation stage, but were found at later stages when the vine's position was fixed, generally one or two nodes below the node still circumnutating. The number and extent of fiber development correlated roughly with the amount of torsion required for the vine to ascend a support. In contrast, species that use adventitious roots for climbing or were trailing/scrambling-type vines did not have G fibers. These data strongly support the concept that coiling and twining in vines is caused by the presence of G fibers.