Effect of different day and night temperatures on the diurnal growth rate of terminal and lateral fruits in Golden Delicious apple

Abstract

The diurnal growth rate of terminal and lateral fruitlets in the same cluster was studied in Golden Delicious under varying night and day temperature conditions In growth chambers as well as in the open. Terminal and lateral fruitlets had a similar growth rate. Both started to shrink approximately one hour after sunrise and to recover between 14:00 and 15:00 on clear, sunny days. Low night temperatures retarded the growth rate. Less shrinking occurred during periods of high humidity, low solar irradiation and low temperatures compared with low humidity, high solar irradiation and high temperatures. Fruitlets showed a greater overall increase in diameter under the latter conditions despite the reduction in size during the morning. Two-year-old shoots on which the fruit clusters were borne showed similar diurnal growth patterns as did the fruit. Differences in the incidence of stem end russet between terminal and lateral fruit produced on trees inside the growth chamber and trees In the open did not appear to be related to the diurnal growth rate of the fruitlets.