Regulation of ethylene biosynthesis after short-term heat treatment in etiolated pea stems

Incubation of plant tissues at a constant elevated temperature greatly inhibits both basal and wound ethylene production. However, recovery from heat treatment is relatively rapid and is followed by stimulated ethylene production. The present investigation examines the kinetics of ethylene production after short-term heal treatment and the regulation of heat-altered ethylene production. Subapical stem segments of 7-day-old etiolated pea L. cv. Alaska) seedlings were analyzed for ethylene production, 1-aminocyclopropane-l-carboxylic acid (ACC) oxidation, and ACC and l-(malonylamino)cyclopropane-l-carboxylic acid (MACC) content after a 2-min 40°C heat pulse. The short-term heat pulse transiently inhibited ethylene production and ACC oxidation accompanied by a slight ACC accumulation within a 30-min time period. Conjugation to MACC did not appear to play an integral role in heat-regulated ethylene production. It was concluded that the major factor affecting ethylene production after heat treatment is the temporary inactivation of ACC oxidation. The possible roles of ACC synthase, ACC oxidase and lipoxygenase in regulating ethylene production after heat treatment are discussed.