Ion transport properties of plant cell walls: Ca/Mg selectivity

A selectivity coefficient K (Ca/Mg) ranging from 2 to 6 was found for isolated cell walls extracted from flax callus. We show that the Ca/Mg mobility ratio is close to the selectivity coefficient. The study in solution of the extracted pectins gives evidence that cation mobility, especially of calcium, is at least partly due to the structure of the pectins. In fact the primary structure of the pectins is a factor which determines the local charge density.