Abstract

Treatments with gibberellin A1(GA1), GA3 and GA20 promoted stem elongation in rosetted seedlings of Eustoma grandiflorum in the following order : GA1=GA3>GA20, whereas ent-kaurene (K), ent-kaurenoic acid (KA) and GA19 did not. GA1, GA3, GA19 and GA20 treatments promoted leaf elongation in the order of GA1=GA3=GA20 > GA19, although K and KA did not. Quantitative analysis of endogenous GAs suggested that GA-biosynthesis pathway prior to GA53 might be blocked in the rosetted plants. Furthermore, the results of stem and leaf elongation by the GA treatment indicate that there was a difference in 20-oxidase activity between stem and leaves of rosetted plants. Quantitative analyses also provided evidence that there were tissue-specific 20-oxidase activities not only in the rosetted plants but also in the non-rosetted plants of E. grandiflorum. GA3-induced stem elongation, but not floral initiation in rosetted plants under 35°/30°C. Uniconazole (UCZ) inhibited leaf expansion, stem elongation 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.

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