The activity of gibberellin A24 (GA24) has been tested in 10 plant bioassay systems. Relatively high activity was recorded in the cucumber, dwarf rice, and d-2 and d-3 dwarf maize bioassays; d-5 dwarf maize seedlings were only moderately sensitive. In amounts of less than 1 μg, GA24 was inactive in the lettuce hypocotyl, lettuce root, dwarf pea, d-1 dwarf maize, barley half-seed, and cypress flower induction bioassays.