Sugars play indispensable roles in many metabolic processes in plants. In broccoli, the level of sugars, particularly sucrose, rapidly decline few days after harvest. This study investigated the in uence of exogenous application of 10% (w/v) sucrose to broccoli heads during storage at 20 o C. Hydration of the head was slowed down by sucrose treatment compared with the non-treated heads which gained weight by about 5% of the initial value at the end of the experimental period. Furthermore, sucrose application enhanced ethylene production as well as respiration rate. Glutamine synthetase (GS; EC 6.3.1.2) activity was higher in the orets of sucrose-treated heads but, like the non-treated heads, the activity continuously declined until the end of the storage period. The relatively higher GS activity during the early period of storage caused the delay of the onset of ammonia accumulation by about a day. In the branchlet portion, GS activity was higher in the sucrose-treated heads until day 2 but declined thereafter. The decline in GS activity in this portion, however, did not result to ammonia accumulation. induced. However, in this study, sucrose was considered since sugars are transported to the sink tissues as sucrose; other forms of sugars could be hardly transported into the cells (Nishikawa et al., 2005). As mentioned earlier, sugar application improves the shelf life of perishable produce. However, the in uence of sucrose on glutamine synthetase activity and ammonia accumulation, which are believed to have important roles in the shelf life of broccoli, have not been investigated which formed the basis of this study. This report also presents the changes of some important physiological processes occurring in broccoli during storage.