Effects of temperature on the fruit growth and quality of Satsuma oranges

Abstract

1. The effect of temperature on the fruit growth was studied with Satsuma oranges in each stage of fruit enlargement and maturity, by keeping 3-year-old trees at the various controlled temperatures of the growth chambers (so-called Koitotron). In 1967, 16 experimental plots were made by combining day and night temperature of 15°, 20°, 25°, and 30°C with one another. In 1968, 4 experimental plots by constant temperature of 15°, 20°, 25°, and 30°C were made.2. The growth of Satsuma orange fruits between 20°and 25°C was consistently superior in diameter (transverse) and weight at the both stages, regardless of day and night temperature. Thus, this fact suggests that no difference of temperature between day and night is necessary for most favorable growth of fruits in the range from 20°to 25°C. However, a higher temperature was generally superior to a lower temperature for the fruit growth in diameter (longitudinal), and the flesh % per fruit was greatest at 25°C.3. Sugar contents in the fruit juice of around 20°C were always superior at the both stages. However, the content of reducing sugars and their rate in total sugars generally increased with increasing temperature in the range of 15°to 30°C.4. Titratable acid contents in the fruit juice decreased earlier at 25°C in the stage of fruit enlargement and between 20°and 25°C in maturity. At 30°C or 15°C, however, they did not decrease so easily.5. Chlorophyll contents in the fruit rind clearly decreased at lower temperatures in the both stages. Paticularly, those contents at 15°and 20°C were much less than at 25°and 30°C.6. Carotenoids contents in the fruit rind rapidly increased as ripening advanced. As a result, carotenoids contents greatly increased at 20°C over this period. Though carotene contents decreased, xanthophyll contents apparently increased in the stage of fruit maturity. The inverse relationship between xanthophyll and carotene contents was observed especially in lower temperatures. Carotenoids contents in the flesh were mostly consisted of xanthophyll.