Physiological behavior of peroxidase isozymes in sweet potato root tissue injured by cutting or with black rot<xref ref-type="fn" rid="fn1"><sup>1</sup></xref>

Abstract

We found that the increase in total activity of peroxidase isozymes in diseased tissue of sweet potato roots was mainly caused by the 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, but not in diseased tissue. We assumed that its absence in the latter was 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 component H formation in cut-injured tissue. Also, ethylene treatment rather effectively maintained the increased activity, which otherwise would have decreased at a later stage. Induction of component H formation was accompanied by the formation of a lignin-like substance on the cut surface. We suggest that component H contributes to the formation of this substance.