Accumulation of Wall-Associated Peroxidases during Wound-Induced Suberization of Flax

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Flax plants deposit ligno-suberin material around wounds. The deposition of this material is first detected histochemically at 3–4 days after wounding. Preceding this, at 2 days after wounding, the levels of ionically bound and covalently bound but Driselase-solubilized wall peroxidase activity are approximately four-fold higher than the control samples from unwounded tissue. Although this increase in wallassociated peroxidase activity is accompanied by an increase in the ability of the wall-associated enzymes to oxidize reduced nicotinamide adenine dinucleotides (NADH) to form hydrogen peroxide (H2O2), the ratio of NADH oxidase to peroxidase activities is lower than the unwounded control samples. These figures suggest that wounding does not result in the accumulation of wall-associated peroxidases that have a particular affinity for the generation of H2O2. It is intriguing, therefore, that cell wall preparations from wounded tissue at 2 days have gained the ability to oxidize peroxidase substrates in the absence of added H2O2. This suggests that these preparations can either generate their own H2O2 or contain covalently bound wall oxidases. An examination of peroxidase isozymes present in the wall-associated fractions suggests that the wound healing process is accompanied by increases in the abundance of specific cationic and anionic isozymes. Some of the cationic peroxidases isozymes can also oxidise peroxidase substrates in the absence of H2O2. The significance of the production of these oxidase/peroxidase isozymes during wound healing is discussed.