Rapidly Induced Wound Ethylene from Excised Segments of Etiolated Pisum sativum L., cv. Alaska

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Abstract
A rapidly induced, transitory increase in the rate of ethylene synthesis occurred in wounded tissue excised from actively growing regions of etiolated barley [Hordeum vulgare], cucumber [Cucumis sativus], maize [Zea mays], oat [Avena sativa], pea [P. sativum], tomato [Lycopersicon esculentum] and wheat [Triticum aestivum] seedlings. Cutting intact stems or excising 9 mm segments of tissue from near the apex of 7 day old etiolated P. sativum L., cv. Alaska seedlings induced a remarkably consistent pattern of ethylene production. At 25.degree. C, wound-induced ethylene production by segments excised 9 mm below the apical hook increased linearly after a lag of 26 min from 2.7 nl/g per h to the first maximum of 11.3 nl/g per h at 56 min. The rate of production then decreased to a minimum at 90 min, increased to a lower second maximum at 131 min, and subsequently declined over a period of about 100 min to about 4 nl/g per h. Removal of endogenous ethylene, before the wound response commenced, had no effect on the kinetics of ethylene production. Tissue containing large amounts of dissolved ethylene released it as an exponential decay with no lag period. Rapidly induced wound ethylene is synthesized by the tissue and is not merely the result of facilitated diffusion of ethylene already present in the tissue through the newly exposed cut surfaces. Previously wounded apical sections did not exhibit a second response when rewounded. No significant correlation was found between wound-induced ethylene synthesis and either CO2 or ethane production.