Effects of Flowering Time on the Fruit Growth and the Acid Content in the Fruit Juice of Mature Kawano-Natsudaidai Trees

Abstract

Effects of flowering time within a tree of 20-yr-old Kawano-natsudaidai on fruit growth and acid content in the juice were examined. The numbers of fruits per tree were 308 in 1976, and 451 in 1977. Fruit size and acid content in the juice were measured in the following February of each growing season.
1) Set percentage of the fruits earlier in blooming time was low, whereas that of the fruits later in blooming time was conversely high. The number of leaves per bearing shoot was greater in the fruits later in blooming time and the percentage of leafy fruit was also higher in a group of fruits later in blooming time.
2) Fruit growth was greater in the fruits earlier in blooming time and average fruit diameters on December 6, 1976 were 100, 98, 95 and 92mm in the fruits blooming on May 13, 18, 24 and 29, respectively. Percentages of larger fruits above L size were 26.6% in 1976, and 10.2% in 1977, and the average fruit weights were 323g and 301g. respectively.
Fruit weight was greater in the fruits earlier in blooming, time and the differences of average weight were 75g between the fruits blooming on May 13 and 29 in 1976, and 69g between the fruits blooming on May 6 and 23 in 1977. Fruit weight was greater in the fruits borne at the upper position of the tree, whereas it was extremely small in the fruits at the lower position, especially, inner part of the same position of the tree. Maximum differences between them were 106g in 1976 and 63 g in 1977.
3) Variation of acid content in the juice ranged from 1.6 to 2.9% in 1976, and from 1.8 to 3.2% in 1977. Their average acid contents were 2.13 and 2.39%, respectively.
Acid content in the juice decreased as the number of leaves per bearing shoot increased, and was greatly influenced by the position where the fruits were attached, but hardly influenced by blooming time.