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Physiology and Biochemistry

Photosynthesis, Transpiration, and Water Potential of Apple Leaves Infected by Venturia inaequalis. R. A. Spotts, Assistant professor, Department of Plant Pathology, The Ohio State University, Columbus, 43210, Present address: Oregon State University, Mid-Columbia Experiment Station, 3005 Experiment Station Drive, Hood River, 97031; D. C. Ferree, associate professor, Department of Horticulture, the Ohio Agricultural Research and Development Center, Wooster, OH 44691. Phytopathology 69:717-719. Accepted for publication 22 January 1979. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-717.

Experiments were conducted with attached McIntosh and Delicious apple leaves to evaluate the effects of Venturia inaequalis infection on photosynthesis, transpiration, and water potential. Scab infection caused significant reduction of photosynthesis in Delicious leaves 14 days after inoculation and in Delicious and McIntosh leaves 28 days after. Percentage of total leaf area diseased exceeded percentage reduction of photosynthesis for both cultivars. Reduced CO2 assimilation was detected in scab-infected leaves only after visible symptoms had appeared. Scab infection did not affect transpiration of apple leaves but caused a decrease in water potential of McIntosh leaves.

Additional keywords: apple scab, Malus domestica, net CO2 assimilation.