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Physiology and Biochemistry

Water Relations in Cotton Plants Infected with Phymatotrichum. M. W. Olsen, Department of Plant Pathology, University of Arizona, Tucson 85721; I. J. Misaghi(2), D. Goldstein(3), and R. B. Hine(4). (2)(3)(4)Department of Plant Pathology, University of Arizona, Tucson 85721. Phytopathology 73:213-216. Accepted for publication 4 August 1982. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-213.

Water relations in cotton plants infected with Phymatotrichum omnivorum were studied to determine the mechanism of wilt development. Relationships between leaf water and osmotic potentials, relative water contents, and diffusive resistances of leaves from diseased and water-stressed healthy plants were similar. Rates of recovery from wilting, measured as increases in relative water content with time in both diseased and water-stressed healthy plants, also were identical. No significant differences were found in root dry weights of healthy and diseased plants, indicating that wilting is not a consequence of reduced root area. As upper leaves of diseased plants began to wilt, resistances to water flow in roots and lower stems of diseased plants increased significantly over those of healthy plants. However, resistance to water flow in petioles of diseased plants was unchanged. These results show that wilting in Phymatotrichum- infected cotton plants is probably the consequence of increased resistance to water flow in roots.