Abstract
Changes in ethylene evolution of intact fruits on persimmon trees were measured in order to investigate the relationship between ethylene evolution and physiological fruit drop at the stage of three to four weeks after full bloom.
1. Ethylene evolution of intact fruits on trees without irrigation (pot culture, cv. Matsumotowase Fuyu) and on shaded trees in the orchard (cv. Hiratanenashi) increased rapidly in a half or one day before fruit abscission. The amount of ethylene evolution was 150-300nl/fruit/0.5h just before abscission.
2. When fruits on ‘Matsumotowase Fuyu’ tree were treated with ACC, ethylene evolution significantly increased in proportion to the concentration of ACC. Especially, ethylene evolution of fruits treated with 5, 000ppm ACC increased 50-150 times more than in control fruits. But fruit abscission was not observed.
3. The application of 500ppm AVG to intact fruits on the ‘Hiratanenashi’ tree reduced ethylene evolution. However, the rate of fruit drop was not different from that of the control, indicating that the abscission layer may have developed despite the inhibition of ethylene synthesis.
4. It was recognized by continuously measuring the fruit diameter, that abscising fruit had stopped growth five or six days before abscission.
5. These results may indicate that internal ethylene is not associated with physiological drop of fruits at the stage of three to four weeks after full bloom.
