Hydrolysis of terminal, non-reducing (1->4)-linked alpha-D-glucose residues with release of alpha-D-glucose. High levels seen in the aleurone and scutellum after germination, while low levels are found in developing seeds. Levels increase steadily throughout imbibition reaching maximum levels at day 7. During germination, levels increase from day 2, reach maximum levels at day 3 and decline after day 5. By gibberellin A3 (GA). Belongs to the glycosyl hydrolase 31 family.