Specific for inorganic phosphate transport across the thylakoid membrane in a sodium dependent manner. Binds glutamate but cannot transport it. May act as an ascorbate transporter at the thylakoid membrane (Probable). Optimum pH is 7.5. Expressed in flower buds, sepals of mature flowers and mature leaves, less in senescent leaves and at low levels in roots. Expressed with a circadian rhythm showing a peak during the middle of the day (under long day conditions). May be due to a competing acceptor splice site. May be due to a competing donor splice site. Belongs to the major facilitator superfamily. Sodium/anion cotransporter (TC 2.A.1.14) family.