Abstract
Endogenous gibberellins (GAs) were extracted from shoots with floral buds of Eustoma grandiflorum and analyzed by full scan gas chromatography/mass spectrometry (GC/MS). Consequently, five C13-hydroxylated GAs, GA1, GA19, GA20, GA44, and GA53, were identified. The presence of these GAs suggests that one major GA biosynthetic pathway, the early C13-hydroxylation pathway, is operating in these shoots. Stem elongation of resetted plants was promoted by applications of GA1, GA4, GA9, and GA20. C13-hydroxylated GAs, GA1, and GA20, were more active in stem elongation than were the non-C13-hydroxylated GAs, GA4, and GA9. Inhibition of stem elongation on Uniconazole-P (UCZ) and Prohexadione-calcium (PCa)-treated plants was wholly reversed by application of GA1, where the inhibition by PCa was partially overcome by GA20. These results suggest that the activation steps of precursory GAs, such as 3β-hydroxylation steps from GA20 to GA1 and from GA9 to GA4, are functioning in the rosetted plants and that the endogenous GA1 is physiologically important in regulating stem elongation of E. grandiflorum.
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