HYDROGEN-PEROXIDE PRODUCTION IS A GENERAL PROPERTY OF THE LIGNIFYING XYLEM FROM VASCULAR PLANTS

Production of hydrogen peroxide (H2O2) by the lignifying xylem of seve ral vascular plants has been studied using a new histochemical method based on the H2O2-dependent oxidation of 3,5,3'5'-tetramelhylbenzidine (TMB) catalysed by cell wall peroxidases. This method allows H2O2 to be determined in the range of 5-100 mu M, where other methods, such as the KI/starch reagent, fail. With this method, it has been possible t o determine H2O2 production in the lignifying xylem of a wide range of vascular plants (gymnosperms and angiosperms). The capability of xyle m tissues of sustaining H2O2 production lends support to the hypothesi s that cinnamyl alcohol polymerization in xylem vessels is caused by a n H2O2-dependent oxidative coupling process. (C) 1998 Annals of Botany Company.