VIEW ARTICLE

Physiology and Biochemistry

Simultaneous Changes in the Rate and Pathways of Glucose Oxidation in Victorin-Treated Oat Leaves. Carroll D. Rawn, Department of Plant Pathology, University of Kentucky, Lexington, KY 40506, Present address: Department of Plant Pathology, University of Nebraska, Lincoln, NB 68583; Phytopathology 67:338-343. Accepted for publication 22 September 1976. Copyright © 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-338.

In time-course tests, victorin (the selectively toxic product of Helminthosporium victoriae) induced in susceptible oat (Avena sativa) leaves simultaneous changes in oxygen uptake rate and the C6/C1 ratio (ratio of ¹⁴CO₂ derived from glucose-6-¹⁴C to that from glucose-1-¹⁴C). The former increased gradually; the latter dropped abruptly. Although decarboxylations of both C1 and C6 increased, C1 more so than C6, the ratio did not change significantly after the initial drop. In dosage-response tests based on a fixed treatment period and varying toxin concentration, victorin stimulated oxygen uptake only if it reduced the C6/C1 ratio. Victorin treatment increased anaerobic CO₂ production but decreased the anaerobic CO₂/aerobic CO₂ ratio. The respiratory uncoupler 2, 4-dinitrophenol increased both oxygen consumption and the C6/C1 ratio of healthy leaves. The results indicate that victorin simultaneously increases respiration rate and the activities of both the pentose phosphate pathway and the glycolysis-Krebs cycle pathway and that the pentose phosphate pathway is not primarily responsible for increased respiration.