Abstract
The abaxial epidermis of the primary leaf of one cultivar of barley was stripped off and exchanged with that of another cultivar. A comparison was made of the 48-hr infection frequency of powdery mildew on the various combinations of composite leaf sections in an attempt to determine the respective roles of the epidermis and mesophyll in the resistance of barley to powdery mildew. In the case in which resistance was clearly defined, the results suggested that the resistance reaction occurs mainly in the epidermis. While the mesophyll appears to play a supportive role in the resistance mechanism, it is also possible that the mesophyll contains a factor which can act to promote powdery mildew infection.
