Relationship between air temperature and fruit growth of Japanese pear (Pyrus pyrifolia Nakai)

As a step to develop a model predicting fruit growth and development in Japanese pear (Pyrus pyrifolia Nakai cv. ‘Kosui’), the effects of air temperature were investigated by using temperature-controlled sun-lit growth chambers. Potted Japanese pear trees were treated with different air temperatures from 8 to 30°C in the respective three fruit stages; i.e. the young fruit stage (for 33 days after flowering), the middle fruit stage (from 47 to 81 days after flowering) and the late fruit stage (from 90 to 124 days after flowering). Fruit diameter growth during the young fruit stage was accelerated with increasing air temperatures from 8 to around 25°C. Furthermore, the number of days elapsed from flowering to harvest determined by fruit ground color was remarkably shortened by increasing the air temperature for 33 days after flowering. The effect of temperature was represented as: Y=-1.24T+147.2 (1) where Y is the number of days from flowering to harvest, and T (°C) is the mean air temperature for 33 days after flowering. The equation gave good estimates for the harvests dates of mature trees grown in orchard. Air temperatures in the middle and late fruit stages had no remarkable effects on the fruit growth and the harvest date. Eq. (1) was applicable to the estimation of the fruit growth under various temperature regimes in combination with the model of fruit growth developed before for the effect of solar radition.