High-affinity potassium transporter that does not show potassium-sodium cotransport (PubMed:20351263, PubMed:21610181). Potassium transport seems to be independent of sodium (PubMed:21610181). Mediates transport of the divalent cations magnesium and calcium in the absence of competing potassium ions (PubMed:20351263, PubMed:21610181). Selectivity for potassium is dominant over divalent cations, and magnesium and calcium transport may be small and may depend on competing potassium concentrations (PubMed:20351263, PubMed:21610181). K(+)(in) = K(+)(out) Mg(2+)(in) = Mg(2+)(out) Ca(2+)(in) = Ca(2+)(out) Localizes to the plasma membrane. Expressed in spikelets, leaf blades, leaf sheaths, internodes, nodes, the base of stems and roots. HKT transporters are proposed to contain 4 pore-forming regions enclosed by transmembrane segments with each containing a potassium channel-like selectivity filter motif. Belongs to the TrkH potassium transport family. HKT (TC 2.A.38.3) subfamily.