EXCHANGE DIFFUSION OF ALKALI IONS THROUGH THE APOPLAST OF THE POTATO (SOLANUM-TUBEROSUM L) STORAGE PARENCHYMA

Interdiffusion coefficients of K and Na for tangential transport throu gh cell walls were found to be independent of ion strength and only mo derately (c, 50%) lower than values known for diffusion in water, Alth ough at low salt concentrations alkali ion exchange diffusion on the c ell wall pathway is facilitated by accumulation of diffusing species i n the Donnan space, at all concentrations the resistance of the whole tissue for apoplastic cation exchange diffusion remained significantly higher than that of unstirred liquid of equal thickness, as the area fraction of the cell wall pathway in the parenchyma is small.