METABOLISM AND BIOLOGICAL-ACTIVITY OF GIBBERELLIN A4 IN VEGETATIVE SHOOTS OF ZEA-MAYS, ORYZA-SATIVA, AND ARABIDOPSIS-THALIANA

[17-C-13,H-3]Gibberellin A4 (GA4) was injected into the shoots of tall (W23/L317), dwarf-1 (d1), and dwarf-5 (d5) Zea mays L. (maize); tall (cv Nipponbare), dwarf-x (dx), and dwarf-y (dy) Oryza sativa L. (rice) ; and tall (ecotype Landsberg erecta), ga4, and ga5 Arabidopsis thalia na (L.) Heynh. [C-13]GA4 and its metabolites were identified from the shoots by full-scan gas chromatography-mass spectrometry and Kovats re tention indices. GA4 was metabolized to GA1 in all nine genotypes. GA4 was also metabolized in some of the genotypes to 3-epi-GA1, GA2, 2bet a-OH-GA2, 3-epi-GA2, endo-GA4, 16alpha,17-H-2-16,17-(OH)2-GA4, GA34, e ndo-GA34, GA-58, 15-epi-GA63, GA71, and 16-epi-GA82. No evidence was f ound for the metabolism of GA4 to GA7 or of GA4 to GA3. The bioactivit ies of GA4 and GA1 were determined using the six dwarf mutants for ass ay. GA4 and GA1 had similar activities for the maize and rice mutants. For the Arabidopsis mutants, GA4 Was more active than GA1 at low dosa ges; GA4 was less active than GA1 at higher dosages.