Effect of Fruit Temperature on the Growth of Cucumber Fruits

Abstract

The effect of fruit temperature on the growth of cucumber fruit at the early stage of development was investigated. Cucumber fruits attached on the vine were put in chambers controlled at temperatures ranging from 5° to 30°C.Relative growth rate (RGR) increased as the fruit temperature was raised to 30°C, and was estimated to be 0 at about 5°C. The multiple regressions of RGR on fruit temperature and fruit volume gave high multiple correlation coefficients for different seasons and cultivars. Partial correlation was positive between RGR and fruit temperature and negative between RGR and fruit volume. This indicated that the RGR of fruits at the same volume is almost linearly related to fruit temperature. However, an Arrhenius plot of RGR gave a line with a break point near 12°C, at which point a qualitative change in fruit growth was suggested to occur.Q10 of RGR was about 2 between 15° and 30°C regardless of the growing season, but for fruits at the same temperature, RGR was higher in spring than in winter. From this result it was suggested that a seasonal difference in RGR could be brought about by a difference in carbon concentration of phloem sap, while the influx rate of the phloem sap was determined by fruit temperature.There was no difference in temperature response of RGR between cultivars.