Ion Exchange and Diffusion in Roots of Hordeum Vulgare

Abstract

Measurements were made of the rapid, free space exchange of sodium, potassium, and iodide in barley roots (Hordeum vulgare cv. Bolivia). Part of this free space exchange was due to a cation-exchange system as in other plant cell walls (beet, Ohara). From these measurements the diffusivity of both potassium and sodium was estimated to be 3-4 X 10-7cm2sec-1 in barley root cell walls. The exchange sites were distributed between the cortex and the stele, but exchange with sites in the stele was not detectably slower than with those in the cortex, so it is considered that the endodermis does not act as an effective barrier to potassium and sodium diffu.sion in barley roots.