The pathway of phloem unloading and the metabolism of translocated sucrose were determined in corn (Zea mays) There are several possible pathways for assimilate unloading in sink regions (Fig. 1). One possibility is that sucrose exits the phloem via either a passive, facilitated, or energy-dependent transfer step and enters the apoplast. Sucrose can then either be hydrolyzed by a cell wall invertase to hexoses which are then accumulated by hexose-specific carriers in adjacent consuming cells or sucrose can enter without hydrolysis via a sucrose-specific carrier. Alternatively, assimilates can be unloaded via a symplastic route through plasmadesmata. In the latter scheme, intracellular hydrolysis of sucrose could occur within the cytoplasm or vacuole depending on the intracellular location of invertase activity.