ハッサクの果実の肥大と果汁の糖, 酸含量の変動に及ぼす摘果時期の影響

Abstract

Effects of the time of fruit thinning on the fruit growth and the variations of sugar and acid contents in the fruit juice of twelve-year-old Hassaku trees (Citrus hassaku Hort.) were examined. The numbers of leaves per fruit were 55 in the thinned tree on July 15, and 53 in the thinned tree on August 17, and 31 in the non-thinned tree. Fruit size and sugar and acid contents in the juice were measured on both December 14 and March 24.1) Fruit growth was superior in the thinned trees in both July and August, and number of L, M size fruits was greater. The ratios of larger fruits above L size were 56.7% in the thinned tree in July, and 44.2% in the thinned tree in August, and 9.7% in the non-thinned tree. The mean fruit weights were 273, 270, and 209g, respectively.2) The variation of sugar content in the juice examined in December ranged from 9.0 to 10.4% in the thinned tree in July, and from 8.8 to 10.0% in the thinned tree in August, and from 9.2 to 11.0% in the non-thinned tree, and also the variation of acid content ranged from 1.4 to 1.7% and from 1.3 to 1.8%, and from 1.4 to 2.0%, respectively. Average sugar contents were 9.6% in the thinned tree in July, and 9.4% in the thinned tree in August, and 9.9% in the non-thinned tree, and also average acid contents were 1.62, 1.58, and 1.75%, respectively.When the fruits were stored in room temperature after harvested in December, and examined in March, the variation of sugar content ranged from 9.0 to 10.8% in the thinned tree in July, and from 9.0 to 10.6% in the thinned tree in August, and from 9.0 to 11.0% in the non-thinned tree, and also the variation of acid content ranged from 1.1 to 1.5%, and from 1.0 to 1.5%, and from 1.1 to 1.7%, respectively. The acid content was lowered during storage.3) Significant negative correlations were found between fruit weight and acid content observed both in December and March. Correlation coefficients were r= -0.54 and -0.41 in the thinned tree in July, and r=-0.56 and -0.55 in the thinned tree in August, and r=-0.72 and -0.55 in the non-thinned tree.