Unwinding the mechanics of cucumber tendrils

Pomona Colloquium by Prof. Sharon Gerbode:Plant tendrils are specialized climbing organs that have fascinatedbiologists and physicists alike for centuries. Initially straight tendrilsattach at the tip to an elevated rigid support and then winch the plantupward by coiling into a helical morphology characterized by two helices ofopposite handedness connected by a so-called helical perversion”. Charles Darwin surmised thatcoiled tendrils serve as soft, springy attachments for the climbing plant.Yet, the tmechanical effect of the perverted helical shape of a coiled planttendril has not been fully revealed. Using a combination of experiments onCucurbitaceae tendrils, physical models constructed from stretched rubbersheets, and numerical models of helical perversions, we have uncovered thattendril coiling occurs via anisotropic shrinkage of a strip of specializedcells in the interior of the tendril. Furthermore, variations in themechanical behavior of tendrils as they become drier and “woodier” adds anew twist to the story of tendril coiling. “