The dynamic and steady state aspects of the pH and electric potential (Ψ) profiles, that develop in the experimental medium in association with the photosynthetic assimilation of exogenous HCO−3 by internodal cells of Chara corallina, were investigated. A theoretical treatment is presented which explains the origin of the Ψ phenomenon. This theory was tested by comparing the pH and Ψ values generated by a numerical analysis model (which simulated the experimental system) against experimental data. Verification of our model indicates that the steady state ionic fluxes, associated with HCO−3 assimilation (HCO−3, OH−, and CO23−, are not significantly influenced by the electric potential gradients. The main driving force causing the observed fluxes is the diffusion gradient associated with the respective ion. By simultaneous measurement of Ψ and pH, at the centre of an alkaline band, a direct correlation was established between light-activation and dark-deactivation of the OH− transport system and the light-mediated changes in Ψ at the cell surface. In addition, under steady state conditions, an almost perfect correlation was observed between alkaline band pH centres and the negative electric potential maxima. These data offer strong support for the hypothesis that OH−efflux, in this system, is an electrogenic process. Based on our present analysis, the Ψ profile along the cell indicates that, in terms of the spatial aspect of HCO3− transport, the rate of HCO−3 influx varies quite dramatically along the length of an internodal cell. This aspect is discussed in terms of the cellular integration of OH− and HCO−3 transport in this species.
No takes yet. Share an insight, caveat, or question.
FERRIE et al. (1979) studied this question.