3 Ultradian Growth Oscillations in Organs: Physiological Signal or Noise?

This review examines ultradian oscillatory growth in the multicellular organs of higher plants. My objective is to derive insight about the underlying physiological processes powering expansion. If the process of diffuse growth is inherently oscillatory, then it is reasonable to expect entrainment of these cellular oscillators across a tissue and the emergence of coherent macroscopic growth oscillations. After reviewing studies of circumnutation and linear growth, it appears that such entrainment is rare or weak. I argue that rather than reflecting the existence of an inherent oscillation in the process of diffuse growth, ultradian movements of plant organs reflect successive responses to mechanical perturbation.