Abstract: With the measurements of leaf stomatal conductances (gs1, i=l, 2, 3, or 4) in different layers of the winter wheat canopy and the other related variables, the diurnal changes of different layer leaf stomatal conductance and canopy stonatal conductance (ge) have been analysed in grain filling and milk stages in several aspects: There are most positive correlations between the adaxial and abaxial stomatal conductances of all different layers in both of the two growing stages; During the day, in addition to its parallel changes of all layers with time, gs1 shows the tendency of decrease from the top to the botom of the canopy. This is mainly because the light intensity exposing to leaves should decrease in the same direction. But in some cases this change tendency disappears or reverses when the extent to which the leaf water potential increase from the upper layer to the lower one of canopy becomes greater. This may show the effect that leaf water potential is favorable to the open of stomata. The gc also shows the evident change in the day and the value of it in' grain filling stage, is larger, than that of milk stage.

Key words: Leaf stomatal conductance, Canopy stomatal conductance, Leaf water potential