Influences of environmental factors on water use efficiency(WUE)of winter wheat grown in field under different water treatment were studied. Results indicated that:(1)Environmental factors influenced WUE synthetically and complexly.(2) The increase of rs(stomatal resistance)cahsed by water deficit could increase WUE,but the increase of Dla (vapor pressure difference between leaf and air)also caused by water deficit could decrease WUE.(3)The influences of canopy boundary layer resistance(ra)and CO2 concentra...