Studies on the inhibition of ethylene action by 1-methylcyclopropene (1-MCP)

Individual carnation (Dianthus caryophyllus L. 'White Sim') petals respond to the presence of low concentrations of ethylene (1 muL(.)L(-1)) by a predictable inrolling. Pretreatment of the petals with 50 nL(.)L(-1) 1-MCP prevented the ethylene-induced inrolling, even when the ethylene treatment concentration was 1000 muL(.)L(-1). At temperatures below 20degreesC, the effectiveness of 1-MCP was sigmoidally reduced. The normal inhibition of ethylene action achieved by exposing petals to 100 nL.L-1 1-MCP for 1 h was eliminated by the presence of 1 muL(.)L(-1) ethylene in the treatment atmosphere. As the treatment time increased, 1-MCP overcame the effect of contaminating ethylene, so that by 6 h the petals were no longer affected by subsequent exposure to ethylene. 1-MCP has been suggested to inhibit ethylene action by competitively (and irreversibly) attaching to the ethylene-binding domain in the binding site protein. Our data are more consistent with an alternative model in which 1-MCP binds to a site that is exposed during the allosteric changes that accompany the normal activities of the binding site in the absence of ethylene.