Abstract In plants high affinity transport proteins mediate the essential of ammonium across membranes. Arabidopsis thaliana six these AMmonium Transporters (AMTs) are encoded by genome. All them show a unique expression pattern. While most AMTs highly expressed in root, AtAMT1;4 is limited to pollen grains and tube. Here, we addressed characteristics heterologous Xenopus laevis oocytes system....