INCREASED ENDOGENOUS GIBBERELLIN LEVEL INDUCES EARLY EMBRYO SAC DEGENERATION OF 'SATOHNISHIKI' SWEET CHERRY IN A WARM REGION
Effects of temperature and gibberellin (GA) on embryo sac development of Satohnishiki sweet cherry were studied. Trees were grown in sunlit growth chambers controlled at 15ºC, 20ºC and 25ºC during the day and grown under field conditions at night, from one month before anthesis to petal fall. The high temperature hastened blooming but reduced flower size. Fruit set decreased with the increase in temperature. Temperatures hardly affected the growth of pollen tubes in pistils. At 25ºC, the nucelli and embryo sacs degenerated more rapidly than at 15ºC. Flowers that developed at 25ºC had a higher endogenous GA level than had those at 15ºC. In another experiment, a solution of 10 or 100 ppm GA3 was sprayed on bursting buds. At anthesis, the GA level of flowers from the buds with 10 ppm GA3 application was nearly double that of the control. GA3 treatments considerably increased the percentage of ovules with a degenerated embryo sac or nucellus by 2 days after anthesis. On the other hand, the application of 500 ppm paclobutrazol (PBZ), a GA-biosynthesis inhibitor, in mid-September prolonged embryo sac longevity the following spring. The endogenous GA level of PBZ-treated flowers was considerably lower than that of the control. These results confirmed that rapid degeneration of the embryo sac and nucellus is a major reason for the reduction in fruit set when the developing flower buds are exposed to high temperatures. Furthermore, it is indicated that GA levels are involved in the regulation of embryo sac and nucellus development, and that early embryo sac degeneration at high temperature may be induced by increased endogenous GA levels.
Beppu, K., Aida, K. and Kataoka, I. (2005). INCREASED ENDOGENOUS GIBBERELLIN LEVEL INDUCES EARLY EMBRYO SAC DEGENERATION OF 'SATOHNISHIKI' SWEET CHERRY IN A WARM REGION. Acta Hortic. 667, 423-432
Prunus avium, pollination, fertilization, phytohormone, GA3, ovule development, paclobutrazol, high temperature