Stomatal conductance of winter wheat (g,) , potential of soil matrixes (ψm) and air saturation deficit (d) were measured in the well watered (W2) and less watered (W,) plots in 1984 to 1985. Results of this experiment showed that during clear days gt in the morning was mainly affected by ψm,which could be well-characterized by a linear regression . So g; in the morning could be an indicator of crop water stress caused by soil water deficit . It is convenient to compare the field crop g, with the well-watere...