Oscillations in Plants - Communication in Plants: Neuronal Aspects of Plant Life - page 261

18 Oscillations in Plants

Sergey Shabala

Abstract Despite the fact that the rhythmical behaviour is a quintessential pattern of life
itself, most researchers still treat oscillations in plants as some unwanted “physiological
noise”. In this review, an attempt is made to summarise recent progress in this area and
highlight the paramount role of oscillatory processes in plant life. First, diversity and hierar-
chy of oscillations in plants are examined, then a general overview of oscillatory phenomena
is given, with the main emphasis on the physiological role of oscillatory processes in plants.
The areas covered include leaf and stomata movement, nutations, nutrient acquisition,
growth and differentiation, photosynthesis and osmotic adjustment. A possible role for
ultradian rhythms in timekeeping is also briefly discussed. The importance of ultradian os-
cillations is further illustrated by discussing their involvement in the encoding mechanism,
mediating plant-environment interaction. Finally, advantages and principles of oscillatory
control are considered in the context of plant physiology, with a major emphasis on feed-
back control and self-sustained oscillations, as well as on deterministic chaos and “strange”
behaviour in plants.

18.1
Introduction

With a possible exception of plant movements (such as those for leaves or
plant axial organs) and oscillations in the stomatal aperture, many plant
physiologists still treat oscillations as some unwanted or physiologically
unrelated “noise” (Giersch 1994). More recently, a breakthrough in under-
standing of the signalling role of Ca 2+ in cell metabolism caused a vivid
interest in calcium oscillations in stomatal guard cells, as reflected by a large
number of excellent reviews (McAinsh and Hetherington 1998; Blatt 2000).
The physiological role of other oscillations found in plant tissues and organs
is yet to be fully revealed. In this review, an attempt is made to summarise
the recent progress in this area and highlight the paramount importance
of oscillatory processes in plant life. The major focus is on ultradian (fast)
oscillations, in the minute range of time periods. This is largely due to
the fact that, despite a significant interest and breakthrough in our under-
standing of mechanisms of circadian oscillations in plants (Webb 2003),
“astonishingly little research effort is currently devoted to ultradian high
frequency oscillations in plant biology” (Lüttge and Hütt 2004).