Abstract
Quantitative analyses of total phenol, o-diphenol, chlorogenic acid, caffeic acid, tyrosine and Klarson lignin in potato-tuber tissues neighbouring cells infected by an incompatible race of Phytophthora infestans were done. Distribution of phenolic compounds as a function of distance from the infected cut surface showed that the tissue zone where the metabolism of phenolic compounds is markedly accelerated by infection by an incompatible race was about 10∼15 cells in thickness. During the first 24hrs, after inoculation, the content of total phenol and other phenol (total phenol minus o-diphenol and tyrosine) increased more rapidly in this zone than in the corresponding uninfected control. However, later (48hrs, after inoculation), the higher the concentration of inoculum, the lower the content of total phenolie, o-diphenol, chlorogenic and caffeic acid in this zone as compared with the uninfected one. Neverthless, the incorporation rate of radioactivity of D-glucose-14C (U.L.) into chlorogenic and caffeic acid was not reduced by the inoculation with dense inoculum, although total radioactivity of the disk fed with D-glucose-14C (U.L.) was distinctly lower in the tissue underlying the infected zone than in the corresponding control. These results indicate that there is an increase in the turnover rate of phenolic compounds in tissue adjacent to the infection regardless of density of inoculum. An increase in the infection of the so called “Klarson lignin fraction”, which may involve browning substances, suggests that there is an intimate relation between the phenol metabolism in this tissue zone and repairing in the infection.
