Mediates both low-affinity uptake and efflux of sugar across the plasma membrane. Can transport glucose, and, to a lower extent, mannose, fructose and galactose. Optimum pH is 8.5 for uptake. Forms homooligomers and heterooligomers with SWEET9, SWEET11, SWEET13, SWEET15, SWEET16 and SWEET17. Mainly expressed in flowers. Slightly induced by the powdery mildew fungus G.cichoracearum. Impaired glucose transport activity. Belongs to the SWEET sugar transporter family.