Circumnutations without gravity: a two-oscillator model.

Abstract

Helical growth movements termed circumnutations occur in a number of different plant organs. The underlying mechanism are complicated. They consist of an endogenous as well as an erogenous component. Since circumnutations in sunflower hypocotyls occur also under gravity free conditions in Space, gravity is not necessary for them to arise. However, the changes of period and amplitude of circumnutations with the applied gravitational force indicate that gravity plays a modifying role. Models for circumnutations have to take these features into account. It seems natural to study minimum models with at least two oscillating units. Two-oscillator models for circumnutations have already been discussed. We have studied the interaction between two coupled oscillatory units. With this model we could simulate movements of hypocotyls. The results of simulations were compared with experimentally recorded movements of the Arabidopsis hypocotyl.