Absorption of Cations by Roots. Effects of Hydrogen Ions and Essential Role of Calcium

Abstract

Of all the ioIns to which plant roots are normiially exposed, hydrogen and hydroxyl ions are the most ubiquitous, for roots can only function in aqueous media. The physiological range of H ion concentrations is from 10-4 Al or slightly more to about 10-9. One of 2 distinct mechanisms of K absorption in barley roots is effective at K concentrations of comparably low levels (5), operating virtually at maxinmal velocity at a K concentration of 2 X 10-4 .. Interactions may therefore be expected between H and K ions in the process of K absorption. It has indeed long been recognize(l that the pH of soil solutions and the activity of H ions in the soil cation exchange system influence the absorption of ions and the growth and ecology of plants.