Identification of endogenous gibberellins and their role in rosetted seedlings of Eustoma grandiflorum

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, GA(1), GA(19), GA(20), GA(44), and GA(53), 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 rosetted plants was promoted by applications of GA(1), GA(4). GA(9), and GA(20). C13-hydroxylated GAs, GA(1), and GA(20), were more active in stem elongation than were the non-C13-hydroxylated GAs, GA(4), and GA(9). Inhibition of stem elongation on Uniconazole-P (UCZ) and Prohexadione-calcium (PCa)-treated plants was wholly reversed by application of GA(1), where the inhibition by PCa was partially overcome by GA(20). These results suggest that the activation steps of precursory GAs, such as 3 beta-hydroxylation steps from GA(20) to GA1 and from GA(9) to GA(4), are functioning in the rosetted plants and that the endogenous GA(1) is physiologically important in regulating stern elongation of E. grandiflorum.