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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 101 (1997), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A new model of root circumnutation is proposed, based on the correlation between nutation and ion flux oscillations in the elongation zone. The model considers that, in a small region on one side of the root and within the elongation zone, the growth rate is different from the average. This local disturbance to growth may have been caused by mechanical, chemical or other stimuli, or it may be merely an effect of existing nutation, tropisms or other asymmetric growth. If this disturbance is a reduction in the local growth rate, the root will be bending towards that side. The model provides that the region of growth reduction enlarges and spreads as a wave along and around the root. As the wave of growth reduction moves away, the initially disturbed region recovers. Viewing the root in the cross section containing the original region, the growth reduction moves from that region with different speeds in the two opposite directions around the circumference of the root. The mathematical formulation for the movement of the growth disturbance is given. The resulting bending of the root can be quite complex. The proposed model allows us to describe typical features of nutating roots reported in the literature and observed in our experiments. Results of simulation show a high correspondence with experimental observations. Some components of a possible physiological mechanism for the model are discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 100 (1997), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The involvement of Ca2+ and H+ flux oscillations in root nutation was studied for decapped roots of corn (Zea mays L. cv. Aussie Gold) placed horizontally. Net ion fluxes were measured around the elongation and meristematic regions using a microelectrode ion flux measuring system. High correlation between H+ flux oscillations and root nutations was found in the elongation region. Two oscillatory components of H+ flux, with periods of about 90 min and 7 min, correlated with root circumnutations and micronutations, respectively. The periods of H+ flux oscillations and rhythmical root movements in this region could be modified similarly by external factors including pH. In the meristematic region no association between ion flux behaviour and nutation was apparent. Ion flux oscillations and nutations both decreased in amplitude as the growth rate at the measured location decreased. Possible involvement of ion flux oscillations in root circumnutation is discussed. It is concluded that a model involving an internal oscillator must be developed to explain the H+ flux involvement in root nutations.
    Type of Medium: Electronic Resource
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