Carbon Dioxide Suppression of Ethylene-Induced Sleepiness of Carnation Blooms1

The threshold concentration of ethylene causing sleepiness of freshly cut carnations was 125 ppb when the blooms were exposed for 24 hr at 20°C. The threshold decreased to 30 to 60 ppb when the blooms were held for 2 days at 5° prior to exposure. High partial pressures of CO 2 in the atmosphere prevented ethylene-induced sleepiness. With 10% CO 2 , the blooms were not damaged by 250 ppb ethylene, and 20% CO 2 provided protection against 500 ppb ethylene. Blooms with stems previously placed in water were as susceptible to ethylene damage as those held dry before exposure to ethylene.