ETHYLENE PRODUCTION AND 1-AMINOCYCLOPROPANE-1-CARBOXYLIC ACID TURNOVER IN PICEA-ABIES HYPOCOTYLS AFTER WOUNDING

Cuttings were taken from 6-week-old seedlings of Norway spruce (Picea abies [L.] Karst.) and placed in a nutrient solution. The immediate re sponse of the hypocotyls to cutting was a decrease in ethylene product ion. Later, more than bh after cutting, ethylene production increased and reached values 5 times the initial 96 h after cutting. The capacit y of the tissue to convert applied ACC into ethylene decreased during the first Gh but increased later, showing a close correlation to ethyl ene production during the whole experimental period. The contents of A CC and ACC-conjugate were determined with a method based on synthesis of a benzoyl-derivative of ACC, which was purified on HPLC and analyse d by GC-MS. Most of the available ACC was rapidly conjugated and both the rate of synthesis and conjugation of ACC increased as a result of wounding. Wound and stress ethylene production is considered important in triggering defense responses, like induction of pathogen-related p roteins, resin production and lignification. The lack of an early burs t of ethylene after wounding in spruce indicates that ethylene is not involved in rapid defense responses in this species.