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 response of the hypocotyls to cutting was a decrease in ethylene production. Later, more than bh after cutting, ethylene production increased and reached values 5 times the initial 96 h after cutting. The capacity of the tissue to convert applied ACC into ethylene decreased during the first Gh but increased later, showing a close correlation to ethylene production during the whole experimental period. The contents of ACC and ACC-conjugate were determined with a method based on synthesis of a benzoyl-derivative of ACC, which was purified on HPLC and analysed 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 proteins, resin production and lignification. The lack of an early burst of ethylene after wounding in spruce indicates that ethylene is not involved in rapid defense responses in this species.