Mediates an active uptake of hexoses, probably by sugar/hydrogen symport. Mostly transports glucose, and barely galactose, xylose and mannose. Inhibited by uncouplers such as 2,4-dinitrophenol and carbonyl cyanide-m-chlorophenyl-hydrazone. Optimum pH is 5.5. Pollen specific (at protein level). Transcripts accumulate in mature pollen before and during germination, but translation starts only when pollen germination initiates, and continues in pollen tubes. Belongs to the major facilitator superfamily. Sugar transporter (TC 2.A.1.1) family.