Embryo sac development and fruit set of 'Satohnishiki' sweet cherry as affected by temperature, GA3 and paclobutrazol

Abstract

Effects of temperature and endogenous and exogenous gibberellins (GA) on embryo sac development and fruit set of 'Satohnishiki' sweet cherry were studied. Trees were grown in sunlit growth chambers kept at 15°C and 25°C from one month before anthesis to petal fall. At 25°C, the nucelli and embryo sacs degenerated more rapidly than at 15°C. When flowers were hand-pollinated with pollens of 'Takasago', fruit set was significantly lower at 25°C than at 15°C. Flowers which developed at 25°C had a higher endogenous gibberellin level than had those at 15°C. When bursting buds were sprayed with 10 and 100 ppm GA3, the percentage of ovules with degenerated embryo sac or nucellus increased considerably by 2 days after anthesis. But an application of paclobutrazol (PBZ) to bursting buds prolonged embryo sac longevity and increased fruit set. These results indicate that the endogenous GA may: 1) regulate the development of the nucellus and embryo sac in sweet cherry flowers, and 2) induce early embryo sac degeneration, which results in the low fruit set during periods of high temperature.