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Physiology and Biochemistry

Influence of Dutch Elm Disease on Resistance to Water Flow Through Roots of American Elm. B. R. Roberts, Research Plant Physiologist, Nursery Crops Research Laboratory, Agricultural Research Service, U. S. Department of Agriculture, Delaware, OH 43015; L. R. Schreiber, Research Plant Pathologist, Nursery Crops Research Laboratory, Agricultural Research Service, U. S. Department of Agriculture, Delaware, OH 43015. Phytopathology 67:56-59. Accepted for publication 14 July 1976. Copyright 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-56.

Changes in root resistance to water flow in American elm seedlings inoculated with Ceratocystis ulmi were investigated. In comparison with noninoculated controls, the rate of exudation from cut stumps of inoculated plants subjected to 2 bars pressure was reduced before foliar symptoms appeared in intact plants. Specific conductance of xylem exudate from infected elm roots was also less than that from roots of healthy plants. The water potential of aboveground parts of diseased elms appeared to be more closely associated with alterations in root resistance than with the development of vascular discoloration in stems. Dutch elm disease also had a negative influence on root growth, thereby reducing the amount of new absorptive surface.

Additional keywords: Dutch elm disease, Ulmus americana, water relations, Ceratocystis ulmi.