RESOLUTION OF DUAL MECHANISMS OF POTASSIUM ABSORPTION BY BARLEY ROOTS

Abstract
The relationship between the rates of absorption of K and Rb by barley roots and the concentration of these ions in the external solution, over the range 0.002-50 m[image], is predictable on the assumption that 2 carrier sites bind and transport the ions. One of these operates at half-maximal velocity at a concentration of about 0. 018 m[image], with very low affinity for Na; the 2nd , at about 16 m[image], with severe competition by Na. The latter but not the former mechanism is inhibited when SO4 is the anion instead of Cl.