Figure 2.

Effects of GAor ABA on petal growth are attenuated by co-application of the hormones. Petals of inflorescences at stage 3 were detached and placed on filter paper soaked with 3% sucrose (Control) or with hormone supplementation and were cultured as described in the text. (A) Time-course dynamics of petal length under control conditions or after treatment with 10 μM GA₃, 50 μM ABA or a mixture of 10 μM GA₃ and 50 μM ABA. A total of 10 petals for each treatment were cultured for 9 days. (B) Effect on petal elongation rate of addition of ABA after pre-culture with GA alone for 2, 12, and 24 h. (C) Effect on petal elongation rate of addition of GA after pre-culture with ABA alone for 2, 12, and 24 h. Petals were cultured for a total of 72 h. Control: petals were continuously cultured with 3% sucrose; GA: petals were continuously cultured with 3% sucrose plus GAalone; ABA: petals were continuously cultured with 3% sucrose plus ABA alone; GA+ABA: petals were continuously cultured with a mixture of GA and ABA; GA2h+ABA/ABA2h+GA: petals were pre-treated with GA or ABA for 2 h followed by addition of ABA or GA. In other cases, the duration of GA or ABA pre-culture before ABA or GA supplementation was as indicated. Each value is the mean ± SE (n = 6 petals). The experiment was repeated at least three times with similar results. Representative data are presented. Letters above the bars in (B,C) indicate significant differences between the respective values (p < 0.05).