Development and Characteristics of Sodium-selective Transport in Red Beet

Slices of storage tissue of red beet (Beta vulgaris L.) washed for only 1 day in distilled water readily absorb K(+) but lack a mechanism for rapid Na(+) uptake. A Na(+) transport mechanism develops if the tissue is washed for several days, and the tissue then excludes K(+) during Na(+) uptake.Both the high affinity and low affinity absorption mechanisms show a development of Na(+) transport with washing, and, in contrast to barley roots, cation selectivity in beet is not affected by the presence of calcium ions.K(+) and Na(+) do not appear to compete for binding sites at the surface of the cells, but, as in barley roots, the cations compete in some way for electrically balancing transported ions. Nevertheless, the development of Na(+) transport and the interaction of Na(+) with K(+) occur in the same way whether cation transport is balanced by Cl(-) uptake or by H(+) or HCO(3) (-) transport.