Response of Leaf and Stem Water Potential of Populus Euphratica to Osmotic Stress in Lower Reaches of Tarim River

The measurement results of water potential of Populus Euphratica in lower reaches of Tarim River in 2003 and 2004 showed that stem water potential in most plots was lower than leaf water potential and there was a great difference between them,which indicated that Populus Euphratica near lower reaches of Tarim River was still under the condition of more serious water stress.The antigradient phenomenon presented by stem and leaf water potential of Populus Euphratica in this area which was different from the daily variation of other plants explained that the temperature was not a predominant factor in a variety of factors influencing the water potential of Populus Euphratica in lower reaches of Tarim River.The relattion analysis between stem/leaf water potential and groundwater level/soil salt,making use of the SAS6.12 software,illuminated that both regression equations and partial regression coefficients in two years fell short of significance level,which revealed that the stem and leaf water potential of Populus Euphratica in lower reaches of Tarim River responded to groundwater level and soil salt less seriously.It could be inferred that soil water content had a greater effect upon the water potential of Populus Euphratica than that of groundwater level,which provided theoretical basis for the suggestion put forward by some experts currently: to turn \!alignment water inputting method to \!combining water inputting and water supplying method gradually.