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Physiology and Biochemistry

The Synergistic Role of Oxalic Acid and Endopolygalacturonase in Bean Leaves Infected by Cristulariella pyramidalis. P. Kurian, Graduate student, Plant Sciences Division, West Virginia University, Morgantown, 26506; D. A. Stelzig, professor, Plant Sciences Division, West Virginia University, Morgantown, 26506. Phytopathology 69:1301-1304. Accepted for publication 6 July 1979. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-1301.

Amounts of oxalic acid were elevated in lesions of bean leaves that were infected for 3 days with Cristulariella pyramidalis. Amounts in the green tissue adjacent to these lesions were considerably higher than those in healthy leaves. Endopolygalacturonase was not detectable in extracts of healthy bean leaves but was present in leaves infected with C. pyramidalis and in pectin-containing medium supporting growth of this fungus. This enzyme was inhibited by CaCl2 and the inhibition was reversed by oxalic acid. Oxalic acid depolarized cell potentials at a concentration as low as 104 M but only if the solution was approximately pH 4 or lower. This depolarization was not rapidly reversed when the bathing solution was changed to one free of oxalic acid. The data presented are consistent with synergistic roles for oxalic acid and endopolygalacturonase during invasion of bean leaves by C. pyramidalis.