In order to know the factors affecting fruit set in Saijo Japanese persimmon, effects of pollination on seed formation and fruit set were compared among 3 cultivars, Saijo, Fuyu and Hiratanenashi in relation to the morphological differences of flower organs among them.
1. Saijo had shorter style and ovary than the other 2 cultivars and its stigma was not exposed out of the cylindrical petals at anthesis. Such a flower type of Saijo may be less favorable for the pollinating activity of insects than those of the others.
2. When pollinators were excluded from the branches by bagging to examine parthenocarpic ability, the percentages of fruit set in Saijo, Fuyu and Hiratanenashi were 20, 28 and 78, respectively.
3. Under the condition of open pollination, the rate of seeded (fertilized) fruits in Saijo was 50% which was about 10% lower than those in the others, but as to the percentage of fruit set, large differences were not observed among the 3 cultivars. The number of seeds per seeded fruit was 2.3 in Saijo and 4.0 in Fuyu.
4. The rate of seeded (fertilized) fruits in each cultivar was much increased by hand pollination, i. e., it was 96.3% in Hiratanenashi, followed by 96.3% in Saijo and 93.9% in Fuyu. The rate of fruit set was also raised by hand pollination in each cultivar and Saijo showed the highest rate (91.9%) among them. The number of seeds per seeded fruit was 3.1 in Saijo and 4.7 in Fuyu. Thus, Saijo was inferior to Fuyu in the number of seeds per seeded fruit when pollinated by hand although hand pollination was more effective for preventing fruit drop in the former than in the latter.