1-MCP blocks ethylene-induced petal abscission of Pelargonium peltatum but the effect is transient

Continual exposure to 1.5 mul l(-1) ethylene caused 100% petal abscission within 2 h from detached flowers of Pelargonium peltatum (L.) 'Pink Blizzard' (ivy geranium) harvested just after the stigmatic lobes had separated. When flowering plants were first pretreated for 2 h with 1 mul l(-1) 1-MCP, ethylene-induced petal abscission was completely inhibited. However, the effect was transient, since percent abscission increased with time after I-MCP treatment. Based on percent abscission from detached flowers after a 2-h ethylene exposure, the half-life of I-MCP activity was about 2, 3 and 6 days after I-MCP treatment at 25, 20.7, and 12 degreesC, respectively, and there was no evidence for a residual effect after 4 or 5 days at 25 and 20.7 degreesC, respectively. A second application of I-MCP renewed the inhibitory effect. Following I-MCP treatment, the force required to separate petals from the flower declined linearly with time. The time until complete loss of the inhibitory effect was strongly temperature dependent, e.g. approximate to 1 day at 25 degreesC versus 3-4 days at 12 degreesC. The usefulness of 1-MCP as a commercial treatment to prevent petal abscission from Pelargoniums will depend on shipping and storage temperature and application frequency. (C) 2001 Elsevier Science B.V. All rights reserved.