A STUDY OF POTASSIUM ABSORPTION BY BARLEY ROOTS

Abstract

The absorption of K by barley roots has been studied in the presence of H+ and other cations. An attempt has been made to explain the data on the basis of the following reaction, HR + K+ = KR + H+ where H R represents a metabolically produced binding compound. In solns. containing H+ and K+ as the only cations, a critical ratio occurs at which K+ is neither gained nor lost. In pure solns. of HC1, the rate of loss of K and other cellular constituents from the roots is dependent on the pH of the soln. and on the temp. At 26[degree]C, K is lost rapidly below a pH of 4.5; at 0[degree]C, the critical pH is 2.5. The presence of other cations, particularly Ca, inhibits the loss of K in acid solns. The absorption of K is stimulated by the presence of Ca++, but inhibited by the presence of Na+. Certain conclusions are drawn from the data concerning the nature of the binding compound H R.