Edward C. Sisler

Effect of 1-methylcyclopropene and methylenecyclopropane on ethylene binding and ethylene action on cut carnations

Abstract1-Methylcyclopropene (1-MCP), formerly designated as Sis-X, has been shown to be an effective inhibitor of ethylene responses in carnation flowers in either the light or the dark. The binding appears to be to the receptor and to be “permanent”. A 6 h treatment at 2.5 nl l−1 is sufficient to protect against ethylene, and 0.5 nl l−1 is sufficient if exposure is for 24 h. As carnation flowers age, a little higher concentration appears to be needed. Most of the natural increase in ethylene production during senescence is prevented by treatment with 1-MCP. A closely related compound, methylenecyclopropane shows ethylene activity. A tritium labelled 1-MCP (60 mCi mmol−1) has been prepared. A higher specific activity is needed for more critical studies.

Effects of 1-MCP on the vase life and ethylene response of cut flowers

Pretreatment for 6 h with low concentrations of 1-MCP (1-Methylcyclopropene, formerly designated as SIS-X), a cyclic ethylene analog, inhibits the normal wilting response of cut carnations exposed continuously to 0.4 μl·l−1 ethylene. The response to 1-MCP was a function of treatment concentration and time. Treatment with 1-MCP was as effective in inhibiting ethylene effects as treatment with the anionic silver thiosulfate complex (STS), the standard commercial treatment. Other ethylene-sensitive cut flowers responded similarly to carnations. In the presence of 1 μl·l−1 ethylene, the vase life of 1-MCP-treated flowers was up to 4 times that of the controls.

Comparison of cyclopropene, 1-methylcyclopropene, and 3, 3-dimethylcyclopropene as ethylene antagonists in plants

A comparison has been made of cyclopropene (CP), 1-methylcyclopropene (1-MCP), and 3,3-dimethyl-cyclopropene (3,3-DMCP) in their ability to protect plants against ethylene. In bananas, both CP and 1-MCP are effective around 0.5 nL L−1, and 3,3-DMCP was effective at 1 μL L−1. Bananas treated with CP and 1-MCP again become sensitive to ethylene at 12 days and those treated with 3,3-DMCP at 7 days. Mature green tomatoes are protected by 5–7 nL L−1 of 1-MPC for 8 days at 25°C and tomatoes treated with 3,3-DMCP at 5–10 μL L−1 are protected for 5 days. Carnation flowers are protected with CP or 1-MCP after exposure to 0.5 nL L−1 for 24 hours and by 1 μL L−1 of 3,3-DMCP. The display life of Campanula flowers is increased from 3.3 to 5.4 days by 10 μL L−1 of 3,3-DMCP and to 9 days by 20 nL L−1 of 1-MCP. Ethylene inhibition of pea seedlings is reduced by treatment with 1-MCP at 10 μL L−1 of ethylene but as ethylene is increased to 3000 μL L−1 growth inhibition increases. 3,3-DMCP treatment causes very little reduction of the ethylene effect even at very low concentrations.

Control of ethylene responses in avocado fruit with 1-methylcyclopropene.

Mature avocado fruit (Persea americana Mill. cvs ‘Ettinger’, ‘Hass’, ‘Reed’ and ‘Fuerte’), harvested during the commercial harvesting season, were treated with various concentrations of 1-methylcyclopropene (1-MCP) for 24 h at 22°C and after ventilation, were exposed to 300 m ll 1 ethylene for 24 h at 22°C. The fruit were then stored at 22°C in ethylene-free air for ripening assessment. Ethylene production, firmness, cellulase (endo-1,4-b-glucanase) and polygalacturonase activity, as well as color change in ‘Hass’ fruit, were monitored during storage. 1-MCP was found to inhibit ethylene-induced ripening of avocado fruit at very low concentrations. Treatment for 24 h with 30‐70 nl l 1 1-MCP delayed ripening of avocado fruit by 10‐12 days, after which the fruit resumed normal ripening. It is suggested that 1-MCP is a potent inhibitor of avocado fruit ripening which exerts its effect via inhibition of ethylene action.

Inhibition of ethylene responses by 1-Methylcyclopropene and 3-Methylcyclopropene

Abstract3-Methylcyclopropene (3-MCP) binds to the ethylene receptor and blocks it for several days, but concentrationswise is less effective than 1-methylcyclopropene (1-MCP). In diverse ethylene-responsive systems, including ripening of mature-green bananas (Musa sapientum L.), inhibition of growth in etiolated pea (Pisum sativum L.) seedlings, abscission of orange (Citrus sinensis L.) leaf explants and mung bean (Vigna radiata L.) leaves, and wilting of campanula (Campanula carpatica) and kalanchoe (Kalanchoë blossfeldiana) florets, full inhibition of the ethylene response required higher concentrations of 3-MCP. Depending on the experimental system, the effective concentration of 3-MCP was from 5 to 10 times higher than that required for 1-MCP.

Competition of cyclooctenes and cyclooctadienes for ethylene binding and activity in plants

Abstracttrans-Cyclooctene, cis,trans-1,5-cyclooctadiene, and cis,trans-1,3-cyclooctadiene have been compared with the cis and cis,cis isomers and with 2,5-norbornadiene for competition with ethylene for binding in mung bean sprouts and tobacco and for action (induction of chlorophyll degradation) in banana. The compounds containing a trans double bond were much more effective in competition for binding and action than the cis and cis,cis compounds. trans-Cyclooctene and cis,trans-1,3-cyclooctadiene were in the general range of 50–90 times more effective than 2,5-norbornadiene.

1-Methylcyclopropene inhibits ethylene action in cut phlox flowers

Abstract Phlox (Phlox paniculata cv. Rembrandt) flowers were found to be very sensitive to ethylene. Exposure to ethylene enhanced flower abscission in a concentration-dependent manner, with 50% abscission attained after treatment with 1 μl l−1 ethylene for 12 h. As a result, ethylene also reduced the number of open flowers on the stems throughout their vase life. A 6-h pre-treatment with a volatile inhibitor of ethylene action, 1-methylcyclopropene (1-MCP), completely inhibited the ethylene-induced flower abscission and hence the reduction in the number of open flowers on the stems. 1-MCP was maximally effective in inhibiting the ethylene response at a low concentration (25 nl l−1) and had no visible toxic effects, even at 500 nl l−1. The effects of 1-MCP on flower abscission were comparable to that of a pulse treatment with silver thiosulfate (STS). We therefore suggest that it may serve as an alternative to the commercial treatment of phlox flowers with STS, the latter being an environmental hazard.

1-substituted cyclopropenes: Effective Blocking Agents for Ethylene Action in Plants

A series of 1-alkane substituted cyclopropenes has been prepared and tested as ethylene antagonists using banana fruits as an assay system. 1-Methyl-, 1-ethyl-, 1-propyl-, 1-butyl-, 1-pentyl-, 1-hexyl-, 1-heptyl-, 1-octyl-, 1-nonyl-, and 1-decylcyclopropene were all very active compounds. 1-Methylcyclopropene protected bananas from ethylene with a minimum concentration of 0.7 nl.l−1 after a 24 h exposure. As the carbon chain length was extended the minimum requirement increased some, but starting with 1-butylcyclopropene, the minimum concentration requirement declined and many cyclopropenes were required in lower concentrations than 1-methylcyclopropene. The time of protection at ambient temperature (22–23 °C) was 12 d for 1-methyl-, 1-ethyl-, 1-propyl-, and 1-butylcyclopropene. 1-Pentylcyclopropene protected bananas for 14 d, 1-hexylcyclopropene for 20 d, 1-heptylcyclopropene for 21 d, 1-octylcyclopropene for 25 d, 1-nonylcyclopropene for 35 d, and 1-decylcyclopropene for 36 d.

Effect of antagonists of ethylene action on binding of ethylene in cut carnations

Five hours after cut carnations had been treated with a pulse of 1 or 4 mM silver thiosulfate (STS), in vivo ethylene binding in petals was inhibited by 22 and 29%, respectively. When binding was measured 4 days after the 4-mM STS treatment, binding was inhibited by 81%. 2,5-Norbornadiene, which substantially delays carnation senescence, inhibited ethylene binding by 41% at a concentration of 1000 μl/l. The Kd for ethylene binding in carnations was estimated to be 0.1 μl/l in petals and 0.09 μl/l in leaves. The concentration of binding sites was estimated to be 6.0×10−9 mol/kg of petals and 2.0×10−9 mol/kg of leaves

Diazocyclopentadiene (DACP), a light sensitive reagent for the ethylene receptor in plants

Diazocyclopentadiene (DACP) has been shown to be an effective reagent for the ethylene receptor. Treatment of mung bean sprouts or tobacco leaves with DACP in the light or in the dark inactivates much of the ethylene binding. In the light, inactivation seems to be permanent, while in the dark, the site becomes active again after the DACP diffuses away. The compound is 10 times more effective in the light than in the dark. DACP inhibits banana ripening indicating the physiological receptor is involved. It also overcomes the inhibitory effect of ethylene on mung bean seedling growth (Km = 0.09 µl/1 E) at low ethylene levels. At high ethylene levels, an apparent high ethylene level site becomes apparent (Km = 50 µl/1 E) and growth is inhibited.