Elastic models of the fast traps of carnivorous Dionaea and Aldrovanda

Abstract

The carnivorous aquatic Waterwheel Plant (Aldrovanda vesiculosa L.) and the closely related terrestrial Venus Flytrap (Dionaea muscipula SOL. EX J. ELLIS) both feature elaborate snap-traps, which shut after reception of an external mechanical stimulus by prey animals. Although Aldrovanda is usually considered as a miniature aquatic Dionaea, the shutting mechanisms of the two plants are actually quite different. The fast shutting of Aldrovanda is indeed based on a simple swelling/shrinking mechanism, while the movement of Dionaea's traps is accelerated by the snap-buckling of the lobes. The purpose of this Report is to describe several key improvements to the elastic models that have recently been introduced to elucidate these movements [Poppinga and Joyeux, Phys. Rev. E 84, 041928 (2011)]. In particular, a precise mechanism for the action of the motor cells of Aldrovanda is proposed, the facts that the opening of the leaves of Dionaea is an irreversible mechanism based on growth and that the strain field is anisotropic and much smaller on the inner than on the outer surface of the leaves during shutting are taken properly into account, and a more accurate formula for calculating mean curvatures is used. The improvements brought to the model are described in detail and the physical consequences of these improvements are discussed.