Abstract: To understand the effects of different moisture stress on sap flow and leaf potential of tomato in greenhouse,authors conducted the experiments under three water treatments,including normal water supply (T1),light water stress treatment (T2) and severe water stress treatment (T3),for tomato variety “Jingfen 2”.The results showed that the daily variation of sap flow of tomato plant occurred as a bimodal curve under T1 and T2 in sunny days,and the bottom point was at 12:00 in the noon with the stoma closed.The sap flow of tomato changed slightly under T1 and T2 in cloudy days.The transpiration changed a lot under different water stresses.Transpiration became less with more serious water stress.The difference between different transpiration decreased gradually with time extension after irrigation,leaf water potential decreased was well,with T1>T2>T3.In addition,solar radiation,air temperature and relative air humidity was the main meteorological factors affecting sap flow rate of the tomato by correlative analysis.The results indicated that there was a positive correlation between the sap flow and solar radiation,air temperature and soil moisture.On the contrary,there was a negative correlation between the sap flow and leaf water potential and the relative air humidity.

Key words: Tomato, Sap flow, Water potential, Water stress