Growth Response of the d-5 and an-1 Mutants of Maize to Some Kaurene Derivatives

(-)-Kaur-16-en-19-oic acid and (-)-kaur-16-en-19-oloxygenated derivatives of (-)-kaurene, stimulated seedlingelongation for the two nonallelic dwarf mutants of maize, d-5 and an-1. Replacement of the exocyclic methylene groupattached to ring D by a keto-, methyl-, hydroxymethyl-, carboxy-, or methylcarboxy group resulted in compounds which were biologically inactive. These kaurene derivatives are structurally related to the gibberellins which produce a similar type of elongation for the d-5 and an-1 mutants.