A rapidly induced, transitory increase in the rate of ethylene synthesis occurred in wounded tissue excised from actively growing regions of etiolated barley, cucumber, maize, oat, pea, tomato, and wheat seedlings.Cutting intact stems or excising 9-mm segments of tissue from near the apex of 7-day-old etiolated Pisum sativum L., cv. Alaska seedlings induced a remarkably consistent pattern of ethylene production. At Ethylene production increases in a wide variety of plant tissues subjected to stress induced by noxious chemicals (2), pathogenic organisms (19), ionizing radiation (1), water imbalance (23), or mechanical injury (16). Abeles (3) has reviewed stress ethylene production. Stress-induced increases in ethylene production occur minutes (8,10,12,17,24), hours (6,9,11,14,18), or days (7, 16,21,22) after presentation of the stress. Appropriate controls are necessary to ascertain whether rapid increases in the rate of ethylene evolution result from facilitated diffusion of endogenous ethylene through the newly exposed cut surfaces, or from induced synthesis. Burg and Thimann (5) showed that in sliced apples the initial surge in ethylene and CO2 evolution was the result of endogenous levels of these gases. Increased evolution of ethylene after a lag period suggested induced synthesis. This is supported by studies with inhibitors which established that protein synthesis is required during the long lag period preceding stress ethylene synthesis (2, 6).Little work has been reported on the kinetics of rapidly induced ethylene production from stressed tissue (10,11 presents a detailed kinetic study of ethylene production from mechanically injured tissue during the first 4 hr after excision.
MATERIALS AND METHODSPreparation of Plant Material. Seeds of Pisum sativum L., cv. Alaska were imbibed in aerated tap water for 6 hr at 23 ± 2 C and planted in moist vermiculite. All subsequent manipulations were performed in the dark or under dim green light. The growth cabinet was maintained at 24 ± I C and continuously flushed with humidified ethylene-free (