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

Continual exposure to 1.5 ml l 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 ml l 1-MCP, ethylene-induced petal abscission was completely inhibited. However, the effect was transient, since percent abscission increased with time after 1-MCP treatment. Based on percent abscission from detached flowers after a 2-h ethylene exposure, the half-life of 1-MCP activity was about 2, 3 and 6 days after 1-MCP treatment at 25, 20.7, and 12°C, respectively, and there was no evidence for a residual effect after 4 or 5 days at 25 and 20.7°C, respectively. A second application of 1-MCP renewed the inhibitory effect. Following 1-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. :1 day at 25°C versus 3–4 days at 12°C. 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. © 2001 Elsevier Science B.V. All rights reserved.