The relationship between endogenous gibberellins and rosetting in Eustoma grandiflorum

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.