Question

Why polyphenol oxidase increased in diseased plants?

Answer 1

Peroxidase and polyphenoloxidase activities, their electrophoretic patterns and the effect of Ethephon (2-chloroethylphosphonic acid) were tested in resistant and susceptible tomato plants, following inoculation with Fusarium oxysporum f. sp. lycopersici (Sacc.). Peroxidase and polyphenoloxidase activities increased in the roots of the resistant type shortly after inoculation, whereas in the susceptible type, a similar increase in peroxidase activity occurred 24 h later. No significant increase in polyphenoloxidase was found in the susceptible type. A marked increase in peroxidase activity in the stems of susceptible plants occurred when disease symptoms appeared.

Ethephon treatment increased the resistance of susceptible plants to Fusarium and enhanced peroxidase and polyphenoloxidase activities.

No changes in peroxidase and polyphenoloxidase isozyme patterns were found as a result of inoculation or Ethephon treatment.