Proton and calcium flux oscillations in the elongation region correlate with root nutation

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 flax 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.