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Physiology and Biochemistry

Increase with Age in Sensitivity of Oat Leaves to Victorin. Harry Wheeler, Department of Plant Pathology, University of Kentucky, Lexington, KY 40506; Phytopathology 67:859-861. Accepted for publication 11 January 1977. Copyright © 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-859.

The chlorophyll content of first leaves from both 8-day - old and 15-day-old oat seedlings susceptible to Helminthosporium victoriae was reduced by treatment with 10 milliunits/ml of victorin. The reduction, however, was greater with the older leaves; when the concentration of victorin was lowered to 1 milliunit/ml, only older leaves showed a significant reduction in chlorophyll content. These results confirmed previous undocumented reports of an increase with age in sensitivity to victorin. A time-course study indicated that the increase in sensitivity to victorin occurred abruptly when the oat seedlings reached 12 days of age. During the preceding two days, the chlorophyll content of both treated and control leaves showed a marked decline. These results suggest that a change in the balance or distribution of endogenous growth regulating substances plays a role in the age-related increase in sensitivity to victorin.