Abstract
The relationship between dry matter production of bearing shoots and physiological fruit drop of Japanese persimmon cv. Fuyu was investigated under non-shading and 50% shading treatments.
Both non-shaded and shaded trees had only 1 peak of fruit abscission at 4 weeks after pollination, and the rate of fruit abscission was higher in shaded trees than in non-shaded trees. However, fruit abscission was not related to the light transmission rate of the bearing shoots.
The abscised fruit increased less in dry weight increment from 1 week before fruit abscission in both non-shading and shading treatments. And the growth of abscised fruit ceased completely at 3 or 4 days before fruit abscission. This indicated that fruit drop had already been induced at 1 week before fruit abscission and that the period of the last 3 or 4 days represented the process of detaching fruit from tree.
As to dry matter accumulation, the main sink organ in the bearing shoots was the vegetative part until 3 weeks after pollination, but thereafter, it changed to the reproductive part.
In bearing shoots whose fruit abscised at 3 or 4 weeks after pollination, dry weight increment of leaf and shoot was significantly higher at 1 week before fruit abscission than in the other bearing shoots. Therefore, it was considered that fruit drop of this type was induced by great sink strength of leaf and shoot.
