Maintenance of gibberellin biosynthesis in excised sunflower apical buds by exogenous sucrose or mevalonate.

Diffusible-gibberellin yields in agar from green sunflower apical buds fell within 40 hr of excision of the buds when they were incubated on 1.5% agar. Incubation on agar containing either 2.0% sucrose or 0.1% mevalonate allowed continued gibberellin production by the buds for at least 72 hr. Mevalonate was more effective than sucrose as a stimulant of gibberellin synthesis. Gibberellins obtained from the buds did not appear to be products of wounded tissues at the cut stem surface, but represented normal gibberellin biosynthesis by bud tissues.