The relationship between endogenous gibberellins and resetting in Eustoma grandiflorum

Treatments with gibberellin A(1)(GA(1)), GA(3) and GA(20) promoted stem elo ngation in rosetted seedlings of Eustoma grandiflorum in the following orde r: GA(1) = GA(3)> GA(20), whereas entkaurene (K), ent- kaurenoic acid (KA) and GA(19) did not. GA(1), GA(3), GA(19) and GA(20) treatments promoted lea f elongation in the order of GA(1) = GA(3) = GA(20) > GA(19), although K an d KA did not. Quantitative analysis of endogenous GAs suggested that GA-bio synthesis pathway prior to GA(53) might be blocked in the rosetted plants. Furthermore, the results of stem and leaf elongation by the GA treatment in dicate that there was a difference in 20- oxidase activity between stem and leaves of rosetted plants. Quantitative analyses also provided evidence th at there were tissue- specific 20 -oxidase activities not only in the roset ted plants but also in the non-rosetted plants of E. grandiflorum. GA(3)-in duced stem elongation, but not floral initiation in rosetted plants under 3 5 degrees/30 degrees C. Uniconazole (UCZ) inhibited leaf expansion, stem el ongation and flower bud development of the non-rosetted plants, but did not inhibit flower bud initiation. These results indicate that leaf expansion, stem elongation and flower bud development are apparently GA-dependent but flower bud initiation is not.