ETHYLENE PRODUCTION OF HEAT-TREATED STEM TISSUES OF RED-OSIER DOGWOODAT SEVERAL GROWTH-STAGES

Ethylene production in stem tissues of red-osier dogwood (Cornus seric ea L.) following heat treatment was determined at several growth stage s. Ethylene production of heat-stressed stem tissue depended on the st age of development and was a function of the degree of stress. During active growth and early endodormancy, heat stress of stem tissues stim ulated ethylene production, reaching a peak at 40C, followed by a stea dy decrease at higher temperatures. Highest ethylene levels from stres sed tissues occurred in May, July, September, and March. Only a trace amount of ethylene was produced during endodormancy to ecodormancy (la te October to January) from stressed and nonstressed stem tissues. App lying ACC to stem segments at late endodormancy (December) or applying methionine and IAA to stem segments at maximum endodormancy (November ) enhanced ethylene production of both nonstressed and heat-stressed s tem tissues. Chemical names used: 1H-indole-3-acetic acid (IAA); 1-ami nocyclopropane-1-carboxylic acid (ACC).