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Transient Changes in Hydraulic Resistance Caused in Corn Roots by Fusarium moniliforme. R. W. Schneider, Department of Plant Pathology and Crop Physiology, Louisiana State University, Baton Rouge 70803, Formerly, Department of Plant Pathology, University of California, Berkeley 94720; Phytopathology 74:1230-1233. Accepted for publication 30 May 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-1230.

Analysis with a water transport model of the diurnal cycles of diffusive resistance and water potential of field-grown corn plants indicated that plants infected nonsystemically with Fusarium moniliforme following predisposition by an early-season water stress had transient increases in whole-plant hydraulic resistance. Similarly infected plants grown under steady-state conditions in growth chambers at relatively low vapor pressure deficits (VPD) (low transpirational flux) had significantly higher and constant resistance compared to noninfected and infected plants that had not been predisposed by a water stress. However, infected predisposed plants grown under conditions of higher VPDs (higher transpirational flux) showed the same cycling of resistance as was observed in the field. These results indicate that the source of increased resistance dissipated as a function of water flow through the plant. The site of increased resistance was in the roots rather than the stem. Diurnal vascular gel deposition in response to infection is implicated as the source of variable resistance.

Additional keywords: stalk rot, water relations.