Abstract: [Objective]This experiment was done to analyze the changes of endogenous hormones in lateral buds of olive trees(Olea europaea) during floral induction and flower-bud differentiation, and to investigate the regulation of endogenous hormones on olive flower bud differentiation and alternate fruit bearing. [Method]On the base of dividing period of floral induction and flower-bud differentiation, we analyzed dynamics of endogenous hormones in lateral buds of 16-year-old 'Ezhi 8' and 'Leccino' olive trees during their flower buds formation.[Result]The time of floral induction of 'Ezhi 8' olive was from September 23 to February 18 in the following year, lasting about 150 days, and the 'Leccino' olive was from August 21 to February 18 in the following year, lasting about 180 days. Though the starting date for floral induction of 'Ezhi 8' and 'Leccino' olive trees was somehow different, the critical period and the ending date of floral induction were closely coincided. During the floral induction and flower-bud differentiation, the free abscisic acid (ABA) content in lateral buds was kept stable for the'on'-year trees and peaked for the 'off'-year trees, and the ABA content in the 'off'-year trees was significantly higher than that in the'on'-year trees during the critical period. During the floral induction, the Zeatin Riboside (ZR) content in lateral buds displayed a downward trend for both varieties. During the flower-bud differentiation, the 'on'-year trees showed a slight increase and the 'off'-year trees showed a gradual increase in the variety 'Ezhi 8' and a slight declining after reaching a higher level in the variety 'Leccino'. The ZR content was significantly higher in the 'off'-year trees than in the'on'-year trees during the initial period of floral induction and the whole period of flower-bud differentiation. Gibberllins (GA₃) content in lateral buds displayed a downward trend during the floral induction, and a trend of rapid increase followed by a slight decrease in the 'on'-year trees and a slight increase in the 'off'-year trees during the flower-bud differentiation. GA₃ content was significantly higher in the 'off'-year than in the 'on'-year trees during the initial period of floral induction and whole period of flower-bud differentiation. The content of indole-3-acetic acid (IAA) in lateral buds displayed a general stable trend in 'Ezhi 8', and a rise-decline trend in 'Leccino' during the floral induction with a peak appearing during the critical period. During flower-bud differentiation the IAA content showed an increase trend in the'on'-year trees for both varieties, and in the 'off'-year trees a stable trend for 'Ezhi 8' and a slight increase for 'Leccino'. The IAA content was significantly higher in the 'off'-year trees than in the'on'-year trees during the floral induction, but significantly lower than in the flower-bud differentiation. During the critical period of the floral induction, the ratios of ABA/GA₃, IAA/GA₃ and (ABA+IAA)/GA₃ in the lateral buds were significantly higher in the 'off'-year than in the'on'-year trees for both varieties. During the flower-bud differentiation, the ratios of ZR/GA₃, ZR/ABA and ZR/IAA in lateral buds were significantly higher in the 'off'-year than in the'on'-year trees for both varieties.[Conclusion]Higher levels of ABA, IAA, ABA/GA₃, IAA/GA₃ and(ABA+IAA)/GA₃ benefit the floral induction of olive trees, and higher levels of ZR, ZR/GA₃, ZR/ABA and ZR/IAA benefit the flower-bud differentiation.

Key words: Olea europaea, floral induction, endogenous hormones, ZR, GA₃, IAA, ABA