Unwinding the mechanics of cucumber tendrils
Sept. 18, 2012, 11:30 p.m., Millikan, Pomona College
Pomona Colloquium by Prof. Sharon Gerbode:
Plant tendrils are specialized climbing organs that have fascinated
biologists and physicists alike for centuries. Initially straight tendrils
attach at the tip to an elevated rigid support and then winch the plant
upward by coiling into a helical morphology characterized by two helices of
opposite handedness connected by a so-called "helical perversion". Charles Darwin surmised that
coiled tendrils serve as soft, springy attachments for the climbing plant.
Yet, the tmechanical effect of the perverted helical shape of a coiled plant
tendril has not been fully revealed. Using a combination of experiments on
Cucurbitaceae tendrils, physical models constructed from stretched rubber
sheets, and numerical models of helical perversions, we have uncovered that
tendril coiling occurs via anisotropic shrinkage of a strip of specialized
cells in the interior of the tendril. Furthermore, variations in the
mechanical behavior of tendrils as they become drier and "woodier" adds a
new twist to the story of tendril coiling.