Internode length in Zea mays L. : The dwarf-1 mutation controls the 3β-hydroxylation of gibberellin A20 to gibberellin A 1.

[(13)C, (3)H]Gibberellin A20 (GA20) has been fed to seedlings of normal (tall) and dwarf-5 and dwarf-1 mutants of maize (Zea mays L.). The metabolites from these feeds were identified by combined gas chromatography-mass spectrometry. [(13)C, (3)H]Gibberellin A20 was metabolized to [(13)C, (3)H]GA29-catabolite and [(13)C, (3)H]GA1 by the normal, and to [(13)C, (3)H]GA29 and [(13)C, (3)H]GA1 by the dwarf-5 mutant. In the dwarf-1 mutant, [(13)C, (3)H]GA20 was metabolized to [(13)C, (3)H]GA29 and [(13)C, (3)H]GA29-catabolite; no evidence was found for the metabolism of [(13)C, (3)H]GA20 to [(13)C, (3)H]GA1. [(13)C, (3)H]Gibberellin A8 was not found in any of the feeds. In all feeds no dilution of (13)C in recovered [(13)C, (3)H]GA20 was observed. Also in the dwarf-5 mutant, the [(13)C]label in the metabolites was apparently undiluted by endogenous [(13)C]GAs. However, dilution of the [(13)C]label in metabolites from [(13)C, (3)H]GA20 was observed in normal and dwarf-1 seedlings. The results from the feeding studies provide evidence that the dwarf-1 mutation of maize blocks the conversion of GA20 to GA1.