Methods and materials are disclosed for the inhibition and control of gibberellic acid levels. In particular, nucleic acid sequences of copalyl diphosphate synthase, 3-&bgr; hydroxylase, and 2-oxidase and additional nucleic acid sequences are disclosed. Gibberellic acid levels may be inhibited or controlled by preparation of a chimeric expression construct capable of expressing antisense RNA which suppresses the gibberellin biosynthetic pathway sequence. The antisense sequence is the complement of a copalyl diphosphate synthase sequence, a 3&bgr;-hydroxylase sequence, or a C20-oxidase sequence. Administration of a complementing agent, preferably a gibberellin or gibberellin precursor or intermediate restores bioactivity.