Abstract: Polyphenoloxidase peroxidase and phenylalanine ammonia lyase from cucumber cucumis sativus L. leaves were studied during the period of 22 days after inoculation with cucumber powder mildew. These results suggest that early rapid increase of polyphenoloxidase, peroxidase and phenylalanine ammonia lyase activities is of great significance in the disease resistance. Thus it may provide as one of the physiological indexes for the selection of cucumber resistant cultivar. The mechnism of disease resistance may be shown by toxic role of phenol oxidates and cell wall lignification.

Key words: Cucumber, cucumber powder mildew, polyphenoloxidase, peroxidase, phenylalanine ammonia lease