Physiological behavior of peroxidase isozymes in sweet potato root tissue injured by cutting or with black rot

We found that the increase in total activity of peroxidase isozymesin diseased tissue of sweet potato roots was mainly caused bythe ethylene released from the tissue in response to infection. Component H, a peroxidase isozyme which moved toward the cathode,was formed close to the cut surface in cut-injured tissue, butnot in diseased tissue. We assumed that its absence in the latterwas due to physical and chemical damage caused by fungal invasion,of the component H formed and of the biosynthetic system. Ethylene seemed to be partly involved in inducing componentH formation in cut-injured tissue. Also, ethylene treatmentrather effectively maintained the increased activity, whichotherwise would have decreased at a later stage. Induction of component H formation was accompanied by the formationof a lignin-like substance on the cut surface. We suggest thatcomponent H contributes to the formation of this substance. ¹ This paper constitutes Part 103 of the Phytopathological Chemistryof Sweet Potato with Black Rot and Injury. ² Present address: University of Tokyo Press, 7-3-1 Hongo, Bunkyo-ku,Tokyo 113, Japan. (Received July 11, 1972; )