Involved in ammonium transport (PubMed:25841038). May be involved in arbuscular mycorrhizal (AM) symbiosis with AM fungi (By similarity). Accumulates in roots, in a RAM1-dependent manner, during colonization by arbuscular mycorrhizal (AM) fungi (e.g. Glomus versiforme). Normal arbuscular mycorrhizal (AM) symbiosis with AM fungi. Belongs to the ammonia transporter channel (TC 1.A.11.2) family.