Osmotic Sensitivity of Ca2+ and H+ Transporters in Corn Roots: Effect on Fluxes and Their Oscillations in the Elongation Region |
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Authors: | SN Shabala IA Newman |
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Institution: | (1) Department of Physics, University of Tasmania, GPO Box 252-21, Hobart, Tasmania 7001, Australia, AU |
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Abstract: | Seedling roots of corn were treated with different concentrations of mannitol-containing solution for 1 to 1.5 hr, and net
fluxes of Ca2+ and H+ were measured in the elongation region. H+ fluxes were much more sensitive to osmotic pressure than were Ca2+ fluxes. Oscillations of 7-min period in H+ flux, normally observed in the control, were almost fully suppressed at high osmotic concentrations. Net H+ flux was shifted from average efflux of 25 ± 3 nmol m−2 sec−1 to average influx of 10 ± 5 nmol m−2 sec−1 after the incubation in 100 mm mannitol. The larger the osmotic concentration, the larger was the H+ influx. This flux caused the unbuffered solution of pH 4.85 to change to pH 5.3 after mannitol application. It appears that
the osmoticum suppresses oscillatory H+ extrusion at the plasma membrane. Discrete Fourier Transforms of the H+ flux data showed that, apart from suppression of the 7-min oscillations in H+ flux, mannitol also promoted the appearance of faster 2-min oscillations. Ca2+ influx slightly increased after mannitol treatment. In addition the 7-min oscillatory component of Ca2+ flux remained apparent thereby showing independence of H+ flux.
Received: 25 April 1997/Revised: 11 August 1997 |
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Keywords: | :Zea mays— Ion transporters — Osmotic stress — Hydrogen — Calcium — Mechanosensory channels — Oscillations |
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