Abstract: Ethylene production was severely inhibited in climacteric applefruits treated with either low O2(O2 :1–3%, CO2: 0%)or high CO2(O2:15–21%, CO2:10–20%) for 4, 10, and 15 days, respectively. In treatment with low O2 for 10 or 15days, 1-aminocyclopropane-1-carboxylic acid (ACC) was accumulated in large quantity,but in the fruit treated with high CO2, the content of ACC was slightly lower than thatin control fruit. When the fruit was turned to air after 4-days treatment with low O2, ethylene production and ACC content were able to recover to control level. But in the fruits withlow O2 for 10 or 15 days ethylene production was 100 times lower, and ACC contentwas much higher than those in control even 30-35 days after they were turned to air. It appears that inhibitory effect of the low O2 treatment for longer than 10 days on theconversion of ACC to ethylene was irreversible. In the case of high CO2 treatment fordifferent periods ethylene production obviously decreased at first, then followed by arapid increase. When the fruits were turned to air ethylene production in the treat-ment for 4 days was able to recover to control level, but it remained much lower in tre-atment for 10 or 15 days than that in control throughout the period of recovery. However, ACC contents in both treatments were slightly lower than those in control during a few days after the removal of treatment, but increased slightly after 2-3 weeks.Furthemore, the ability of flesh discs to convert exogenous ACC to ethylene was redu-ced remarkably by the treatment of fruits with either low O2 or high CO2 for longerthan 10 days.

Key words: Apple, High CO2, Low O2, Ethylen, 1-Aminocyclopropane-l-carboxy-lic acid, EFE