Promotion of Flower Bud Formation and Increase of Pollen Yield Applied of Ethephon and BA in ′Chojuro′ Pear (Pyrus serotina Rehd.)

The effects on flower bud formation and pollen yield of several growth regulators applied to the Japanese pear (Pyrus serotina Rehd.) cultivar ′Chojuro′ were investigated.1. The effects on flower bud formation and pollen yield of CCC (2000ppm), SADH (3000ppm), ethephon (300ppm), BA (300ppm) and GA3 (200ppm) applied to ′Chojuro′pear trees every fifteen days from June 1 to July 15 were investigated. From the results it was found that ethephon and BA applied after June 30 markedly promoted flower bud formation and increased pollen yield.2. Further investigation of the effects of concentration and time of application showed that ethephon at a concentration of 50-100ppm and BA at 100-200ppm applied from July 20 to August 20 markedly promoted flower bud formation and increased pollen yield. Moreover double applications of ethephon at a concentration of 50ppm from July 20 to August 20 greatly promoted flower bud formation and increased pollen yield two and a half times.From these results the best time to apply growth regulators in order to promote flower bud formation and increase the pollen yield of ′Chojuro′ pear was found to be from July 20 to August 20, after shoot growth was stopped and while the dormancy of axillary buds is relatively light so that the terminal bud does not grow again.A double application of ethephon at a concentration of 50ppm is most effective andd is recommended for practical use.