S-CARVONE INHIBITS PHENYLALANINE AMMONIA-LYASE (PAL) ACTIVITY AND SUBERIZATION DURING WOUND-HEALING OF POTATO-TUBERS

The periderm formation of wound tissue of potato tuber was inhibited t emporarily after exposure to S-carvone. In wound tissue of control tub ers a suberized cell layer was visible after 4 days whereas in S-carvo ne treated tissue this was observed only after 14 days in most of the tubers. At day 21 all the S-carvone treated tubers had formed suberin but only 10 % of the tubers had developed a (begin of a) cambium layer . The appearance of suberin was related to the activity of phenylalani ne ammonia lyase (PAL); in control and S-carvone treated tissue, maxim um PAL activity preceded the appareance of the first suberized cell la yers by 2 and 5 days, respectively. The specific activity reached the same level in both control and S-carvone treated wound tissue. A short term treatment (2, 4 and 7 days) of tuber wound tissue with S-carvone delayed suberin formation. All the treated tubers showed suberization about 4 days after removal of S-carvone and this was closely related to the increase in PAL-activity. After the S-carvone treatment, the gl utathione metabolism increased: after an initial decrease, as observed in the control, the total glutathione content increased fourfold afte r 9 days and remained high during the treatment. However, the length o f the wound healing period before the start of a S-carvone treatment w as of great influence on the increase of the glutathione metabolism an d on the induction of glutathione reductase.