Fruit Development of Peach and Japanese Pear as Affected by Destruction of the Embryo and Application of Gibberellins

Abstract

The effect of gibberellins on the setting and subsequent growth of peach and Japanese pear fruits has been studied after the embryos were destroyed or the seeds were removed mechanically at different stages of fruit development.
1. In the peach, 14-year-old ′Okubo′ trees were used. Among the growth regulators tested, GA₃ was only effective on the fruit set and development following destruction of the embryos.
2. In young stages of fruit development, that is 5 and 9 weeks after bloom, the application of GA₃ to embryo-killed peach fruit resulted in 8 and 6 per cent set of the mature seedless fruit, respectively. In advanced stages, however, embryo destruction 13 weeks after bloom, with or without application of GA₃, resulted in 93 and 85 per cent set of the seedless fruit at maturity.
3. Injury to the fleshy pericarp without destruction of the embryo had little effect on the rate of fruit set when treated 5 and 9 weeks after bloom.
4. Seed removal and gibberellin application to the cut surface of the Japanese pear fruit, cv. ′Shinseiki′ were done at five different stages of fruit development. Only GA₄₊₇, applied as a lanolin paste to the cut surface of seed-removed fruit, was effective in sustaining further growth of the fruit when treated 3 and 5 weeks after bloom.
5. At the stage of 7 weeks after bloom, however, not only GA₄₊₇, but also GA₃ application began to work effectively to sustain the treated fruit. In late stages subsequent to 9 weeks after bloom, GA₃ in lanolin was more effective than G GA₄₊₇ on maintaining the seedless fruit.
6. It was also found that a large number of treated fruit were infected with rot and fruit splitting in late stages of fruit development and they abscised before ripening.