Plasmalemma transport of OH− inChara corallina

Abstract

The light-mediated, time-dependent rise in the pH value at the center of an alkaline band was analyzed using the methods of numerical analysis. From this analysis an expression of the time-dependent build-up of OH⁻ efflux was obtained for these bands. This information can now be employed to determine whether the light-activated transport of OH⁻ and HCO ₃ ⁻ influences the electrical properties of the plasmalemma. The dark-induced deactivation of OH⁻ transport was also characterized, revealing a transition from efflux to a transient influx phase during deactivation. Numerical analysis of the steady-state OH⁻ diffusion pattern, established along the surface of an alkaline band, revealed that the OH⁻ efflux width was wider than previously envisaged. It was also found that OH⁻ sink regions exist on either side of the efflux zone. These, and other characteristics revealed by the numerical analysis, enabled us to extend the OH⁻ transport model proposed by Lucas (J. Exp. Bot. 1975,26:347).