Abstract: Based on the measurement in the field, this paper gives the difference of stomatal resistance of different layers of leaves in the canopy and different parts of the leaf.The influnce of environmental factors, especially soil moisture, on the difference is discussed. The result shows that the difference of stomatal resistance in different parts of leaf of the canopy is very pronounced. The largest stomatal resistence was found near the tip of the leaf. And then, it decreased gradually from the tip to the base of the leaf. The abaxial stomatal resistance was smaller than the adaxial. Seventy percent of total water and CO₂ was transported by two leaves of the upper part of the canopy. The resistance was increased from the top to the bottom of the canopy. And the resistance was also influenced by leaf area index and environmental factors. For example, when soil water supply was limited, the sensitivity of the stomatal resistance to it was different in different parts of canopy.The stomatals in the lower part were more sensitive than those in the upper part. Finally, this paper gives a model which can be used to calculate the stomatal resistance with conventional meteorogical data and leaf area index.

Key words: Wheat canopy, Soil water, Stomatal resistance