Studies of Rapidly Induced Wound Ethylene Synthesis by Excised Sections of Etiolated Pisum sativum L., cv. Alaska

Abstract

The rate of wound ethylene synthesis was reduced by more than 85% when 9 mm subapical sections of etiolated 7 day old P. sativum L., cv. Alaska seedlings were incubated in water during the 26 min induction period prior to wound ethylene synthesis, but the rate of synthesis was unaffected if sections were incubated in water during the actual synthesis of wound ethylene. The characteristic timing of the wound response was unaffected by either treatment. The ability of various chemical solutions and aqueous plant extracts to alter the rate of wound ethylene synthesis was studied by 1st incubating subapical pea stem sections in solutions under anaerobic conditions (anaerobiosis delays the induction and synthesis of wound ethylene), and then measuring wound ethylene synthesis after the tissue was transferred to air. Solutions of reported precursors of ethylene synthesis, methionine, homoserine, or propanol, did not reverse the water-caused reduction of wound ethylene synthesis. A water-soluble, heat-stable factor in extracts from pea seedlings, and solutions of 23 nM triacontanol, 10 .mu.M kinetin, or 10 .mu.M benzyladenine prevented the reduction of wound ethylene synthesis, but were ineffective if administered after an initial 15 min anaerobic water incubation. Perhaps the active solutions may have only prevented the loss of some ephemeral, though necessary factor, rather than actually containing the substrate or inducer of wound ethylene synthesis. Attempts to isolate and characterize the active fraction from aqueous tissue extracts were unsuccessful. Free radical quenchers, inhibitors of protein synthesis and rhizobitoxine, an inhibitor of ethylene synthesis from methionine, all reduced wound ethylene synthesis when administered in solutions which previously had maintained wound ethylene synthesis.