The HAK1 and HAK2 Genes of Barley Encodehigh-Affinity K+ Transporters That are also Presentin Arabidopsis

Potassium is an essential macronutrientrequired for plant growth and development (Flowers and LSuchli, 1983).The K+ concentration in the soil may be very low, at least in certain conditions,and plants accumulate the cation via high-affinity K+transporters located in the plasma membrane of root cells. In barley,K+ absorption exhibits a biphasic response to the increase of K+ concentration in the external medium (Epstein etal., 1963) showing a first saturable component in the micromolar range and asecond saturable component in the millimolar range.