Time of initiation of the barley endosperm response to gibberellin A3, gibberellin A 14 and kaurene.

Gibberellin A14 and kaurene, precursors of gibberellin A3, are active in the barley endosperm reducing-sugar assay, but require longer incubation periods for activity to be observed than does GA3. This finding shows that the incubation period must be considered when determining whether a compound is active in this assay. The longer incubation periods required by GA14 and kaurene may reflect reduced rates of penetration, or reduced activity within the cell, or the time required for conversion to a physiologically active form.