Selectivity and Kinetics of Ion Uptake by Barley Plants Following Nutrient Deficiency

Abstract

Barley plants grown without an external supply of phosphorus, sulphur, chlorine or nitrogen subsequently absorbed these nutrients, as phosphate, sulphate, chloride and nitrate, more rapidly than did nutrient, sufficient control plants under similar conditions. With phosphorus, sulphur and chlorine, increased absorption was restricted to the nutrient which had been deficient, or to close chemical analogues of it, the uptake of other anions being unaffected or decreased. The selectivity of enhanced nitrate uptake by nitrogen-deficient plants was not examined. The differences in the rates of phosphate, sulphate and chloride absorption by plants of differing nutrient status were due principally to changes in the maximum transport capacity for these anions per unit weight of root, although in plants grown without external chloride there was some evidence that the roots also developed an increased affinity for that ion.