Abstract: Sugar content in grape berry could be significantly improved under root restriction. To
unravel the mechanism of improved sugar content，we studied the effects of root restriction on diurnal
changes of sugar phloem unloading in grape berry by using with“berry-cup”technique in 5-year-old
‘Fenghou’grapevine during ripening period. The results showed that sugar phloem unloading in berry
exhibited three peaks in both the control and root restriction treatment，which appeared at about 9：00，
17：00 and 21：00. In the root restriction，the peak value at 9：00 was about 2.1 and 1.4 fold of those
at 17：00 and 21：00，respectively. Compared with the control，the amount of sugar phloem unloading in
berries under root restriction were about 1.5 fold higher through the experiment. In addition，the abundant
sugar unloading in the morning was 3 hours earlier and the peak was 2.0-fold of the control. Furthermore，
the addition of ABA and EGTA to buffer solution in“berry-cup”promoted sugar phloem unloading，while
EB had adverse effects. The above evidences demonstrated that the process of sugar unloading in berry
consumed energy and it might be related to the enhanced ABA content in grape berry under root
restriction.

Key words: grapevine, root restriction, fruit quality, sugar phloem unloading