Abstract: To investigate the rules of sap flow in grapevine, its inner-and intra-diurnal changes with temperature, humidity, branch length were studied and their correlations were simultaneously analyzed during the bleeding period. In addition, in order to reveal the effects of sap flow on vine growth, relationship among the flows in different vine parts were studied. The results showed that the total bleeding volume ranged from 380 to 540 mL in Rosario Bianco, and the flow lasted for 35-47 d. Flow speed increased first followed by a decrease, and the peak period maintained around 10 d. Branch length greatly affected the bleeding volumes. The sap flow was stable in the longer branch, which mainly contributed to flow; whereas the shorter branch stopped flowing at the earliest time. The flow volume of bleeding sap was stable and evenly distributed in each period. The total bleeding volume varied with bleeding period and differently distributed inner day. During early bleeding period, proportion was gradually increased in the morning and the bleeding volume was larger in the daytime than in the evening. However, the situation was the opposite in the late bleeding period. In addition, we also observed that branch length was directly correlated with flow speed. The flow speed was faster in the longer branch when compared with the shorter ones. The branch position had no significant effect on flow speed. The total flow volume was always greater in branches than trunk. To conclude, the assumed sap flow model was proposed based on the above results, which would lay foundation for the further studies on bleeding sap.

Key words: grape, bleeding sap, flow rule, flow relationship