Complexing of calcium and magnesium by the organic constituents of Yorkshire fog (Holcus lanatus): II.—Complexing of Ca²⁺ and Mg²⁺ by cell wall fractions and organic acids

The complexing of Ca 2+ and Afg 2+ , in a salt solution of cationic composition similar to that of the duodenal fluid of a ruminant, by polysaccharides, lignin and organic acids from the grass Yorkshire Fog is investigated using an ion‐exchange resin method. Regression expressions relating solution cation concentration to the equilibrium resin cation concentrations are derived and used as calibration equations to determine the amounts of bound and ionic Ca 2+ and Mg 2+ in solutions in equilibrium with the plant fractions. Pectin, lignin and the organic adds are effective in complexing a large proportion of the Ca 2+ in a non‐ionic form but only lignin and the acids display significant complexing of Mg 2+ . The hemicelluloses and cellulose have little ability to complex either Ca 2+ or Mg 2+ . The results are discussed in terms of the digestion of these plant fractions in vivo.