Osmotic sensitivity of Ca2+ and H+ transporters in corn roots: effect on fluxes and their oscillations in the elongation region

J Membr Biol. 1998 Jan 1;161(1):45-54. doi: 10.1007/s002329900313.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biological Transport / drug effects
  • Calcium / metabolism*
  • Hydrogen-Ion Concentration
  • Ion Channels / physiology
  • Kinetics
  • Mannitol / pharmacology
  • Oscillometry
  • Osmolar Concentration
  • Plant Roots / physiology
  • Zea mays / physiology*

Substances

  • Ion Channels
  • Mannitol
  • Calcium