Abstract
1. Little is known about the conditions which cause the shedding of flowers and fruits of satsuma mandarin trees.
2. Six 15-year-old satsuma mandarin trees, growing in Fujieda, one of citrus regions in Shizuoka prefecture, were selected for uniformity in size and generaln conditions. Each flower was tagged to secure detailed informations with respect to its performance.
3. Smaller flowers were found more on the horizontal framework branches than on the vertical ones.
4. The development of flowers on the leafless shoot was inferior to that on the leafy shoot in size and weight.
5. Fruits with the larger ovaries on June 8 showed less drop throughout the season, whereas most of those with smaller ovaries ceased growth and abscised earlier in the season.
6. On the vertical framework branches 21.2 per cent of fruits reached maturity, whereas, 14.4 per cent of fruits on the horizontal branches reached maturity.
7. Flowers or fruits on leafless shoots, being inferior in nutritional competition, abscised earlier in the first period of dropping.
Earlier in the season, flowers or fruits abscised at the abscission zone of the pedicel base.
8. Later in the season (the second period of dropping), fruits abscised at the abscission zone of the fruit base. Dropping of fruits on leafy shoots, being superior in nutritional competition, did not occur until the end of June.
9. The ratios of leaves/flowers or leaves/fruits decreased as the season proceeded and were larger on vertical framework branches than the horizontal ones. 14-15 leaves per fruit (on the basis of the number of leaves at full bloom) may be an appropriate criterion for reasonable fruit production of satsuma mandarin oranges.
