HISTOCHEMICAL STUDIES ON THE ALTERATION OF LIGNIN AND PECTIC SUBSTANCES IN WHITE ELM INFECTED BY CERATOCYSTIS ULMI

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Abstract
Histochemical tests were performed on sections from 3- and 4-year-old seedlings of white elm (Ulmus americana) artificially inoculated with Ceratocystis ulmi in studies on alteration of lignin and of pectic substances following infection. Results showed more intense reactions to tests for lignin and pectins in sections from diseased elms than in sections from healthy elms. Lignin and pectin positive materials were found in vessel plugs. It is suggested that these alterations of lignin and pectins result from the action on cell walls of pectolytic enzymes produced by the pathogen.