Oscillations in plants
 
Sergey Shabala
School of Agricultural Science, University of Tasmania, Private Bag 54, Hobart, Tas 7001, Australia
*email: Sergey.Shabala@utas.edu.au
 

Rhythmical behaviour is a quintessential pattern of life itself. Biological oscillations kept many generations of scientists fascinated, from such diverse areas of knowledge as physiology, biochemistry, biophysics, mathematics, and biological cybernetics. An avalanche-like increase in publication number led to foundation of several specialised journals on biological rhythms. However, plants have always been treated as “Cinderellas” in studies on biological rhythms. In contrast to quite obvious circadian rhythms (with 24 h period), ultradian oscillations (with periods of minutes) are not as widespread in plants as they are in animal organisms, at least at first glance. With a possible exception of plant movements (such as leaves or plant axial organs) and oscillations in stomatal aperture, many plant physiologists treat oscillations as some unwanted “noise”. More recently, a breakthrough in understanding of the signalling role of Ca2+ in cell metabolism caused a vivid interest in calcium oscillations in stomatal guard cells, as reflected by a large number of excellent reviews [1-3]. The physiological role of ultradian oscillations in other plant tissues and organs is still underestimated. In this review, an attempt is made to summarise the recent progress in this area and highlight the paramount role of oscillatory processes in plant life. First, advantages and principles of oscillatory control are considered in the context of plant physiology, with a major emphasis on feedback control and self-sustained oscillations, as well as on determenistic chaos and “strange” behaviour in plants. Next, a possible role for ultradian rhythms in timekeeping and the link between ultradian and circadian oscillators is discussed. Several models of circadian oscillators are analysed, and various pros - and contras - for each of them are discussed. The major emphasis is made on possible role of cellular membranes as an important component of the feedback loop in circadian clock mechanism. The importance of membrane- related oscillations is further illustrated by their crucial role as a part of the encoding mechanism, mediating plant-environmental interaction. Practical examples include cell differentiation and morphogenesis, growth, development and adaptive responses to various abiotic and biotic stresses.

  1. Trewavas A (1999) Plant Physiology 120: 1-6
  2. Blatt MR (2000) Current Opinion in Plant Biology3: 196-204
  3. Webb AAR (2003) New Phytologist160: 281-303
 
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