Low-affinity transporter for external inorganic phosphate (Pi) (By similarity). Involved in phosphorus (P) remobilization from dying to developing tissues during corolla senescence in an ethylene-dependent manner (PubMed:19380421). NH4(+)(in) = NH4(+)(out) By ethylene during corolla senescence. Although related to the sugar transporter family, it does not transport sugars. Belongs to the major facilitator superfamily. phosphate:H(+) symporter (TC 2.A.1.9) family.