Title
An electronic device for continuous, in vivo measurement of forces exerted by twining vines
Document Type
Article
Publication Date
1997
Volume Number
84
Source Publication
American Journal of Botany
Abstract
Contact forces are important in maintaining the twining habit of viny stems. A stem twining around a supporting pole puts itself into tension and uses a helical geometry to generate normal loads that are large relative to stem mass per unit length (Silk and Hubbard, Journal of Biomechanics 24(7):599-606, 1991). An electronic pressure-sensing device has been constructed to provide continuous, in vivo measurements of the forces exerted by twining stems. The pressure-sensing element is based on a thin beam load cell that is sheared by a twining stem ascending a split pole. Preliminary results show that after morning glory stems begin to coil around a supporting pole, the twining force increases in an oscillatory fashion over 3 or 4 d, corresponding to positions at least 200 mm from the apex. The force-measuring device should reveal relationships between twining forces and developmental attributes or environmental factors.