Relationship between Dry Matter Production of Bearing Shoots and Physiological Fruit Drop of Japanese Persimmon, by Shading Treatments

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.