INTERRELATIONSHIPS BETWEEN BROWNING AND PHYTOALEXIN ACCUMULATION ELICITED BY ARACHIDONIC-ACID

Hypersensitive browning and phytoalexin accumulation were induced in p otato tuber (Solanum tuberosum L.) by the elicitor arachidonic acid. P henylthiourea, an inhibitor of polyphenoloxidases, completely inhibite d browning of the tissue induced by the elicitor in old (8 months) but not in young (1-2 months) tubers. Phytoalexin accumulation was not af fected by the action of phenylthiourea both in young and old tubers, s howing that this aspect of hypersensitive response is not necessarily related to the browning of the tissue. Hydroxyl radical (HO.) induced browning of the tissue but no phytoalexin accumulation. Gas chromatogr aphic-mass spectrometric analyses showed that the rate of metabolizati on of arachidonic acid was independent of the addition of phenylthiour ea and of the age of tubers.