Volume 37 (1968) Issue 3 Pages 199-204
1. The effect of day and night temperature combination on the fruit growth was observed with Delaware grapes and Satsuma oranges at the stage of fruit enlargement. Day and night temperatures of 15°, 20°, 25°and 30°C were combined with one another, by keeping plants in the growth chambers (so-called Koitotron).
2. The fruit growths of both species in diameter or weight were always superior in the combinations of 20°C day-20°C night, 25°C-25°C and 25°C-20°C. This fact suggests that the optimum temperature for the fruit growth ranges from 20°to 25°C and that no difference of temperature between day and night is needed for the best growth of fruits. However, from the practical point of view the daily change of temperature at the stage of fruit enlargement will be desirable to be 25°C day -20°C night.
3. When the two kinds of day and night temperature combinations of the same daily mean temperature were compared as to the fruit growth, the combination of low day temperature with high night temperature was generally inferior to the combination of high day temperature with low night temperature. Particularly in Delaware grapes, the trend was marked when the day temperature 15°C was combined with a higher night temperature 30°, 25°or 20°C.