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 .
C0007447
cations
C0022023
ions