Environmental stress and the biological clock in plants: Changes of rhythmic behavior of carbohydrates, antioxidant enzymes and stomatal resistance by salinity

Abstract

Summary In this report, the influence of environmental stress as effector on rhythmic phenomena in plants is discussed based on data from literature and from own studies. In our experiments, the effects of NaCl salinity (0, 50, 100 and 150 mM) on the levels of total soluble carbohydrates and on the activities of the antioxidant enzymes, superoxide dismutase and glutathione reductase, were followed as the function of time in young winter wheat ( Triticum aestivum L.) plants grown under controlled conditions. Salinity effects on stomatal movements of the halophytic Aster tripolium L. were also investigated. Periodicity was calculated by Fourier analysis. The results indicate that the fluctuations in the above functions were modulated by the stressor suggesting the connection between environmental stress and biological rhythmicity. On the basis of these observations and literature data we hypothesize that the stressor may modify and desynchronize the biochemical and physiological oscillations by acting either on the input (from receptor till oscillator) or on the output (from the oscillator till the oscillating component) pathways. In these terms, adaptation means re-setting of the new circadian and/or ultradian rhythms of biochemical/physiological processes and the restoration of their concerted action results in maximal resistance for the organism under the new environmental conditions.