Conversion of 1-Aminocyclopropane-1-Carboxylic AcidtoEthylene inPeelof Apple atVarious Stages ofFruit Development'

Internal ethylene concentration, ability toconvert 1-amino-cyclopropane-l-carboxylic acid(ACC)toethylene (ethylene-forming enzyme IEFEI activity) andACCcontent inthepeel ofapples (Malus domestica Borkh., cvGolden Delicious) increased only slightly during fruit maturation onthetree. Treatment ofimmature apples with100microliters ethylene perliter for24hours increased EFEactivity inthepeel tissue, butdidnotinduce anincrease inethylene production. Thisability of apple peeltissue torespond toethylene withelevated EFEactivity increased exponentially during maturation onthetree. After harvest of mature preclimacteric apples previously treated withaminoethoxyvinylglycine, 0.05microliter perliter ethylene didnotimmediately causea rapid increase ofdevelopment inEFEactivity inpeel tissue. However, 0.5microliter perliter ethylene andhigher concentrations did.The ethylene concentration forhalf-maximal promotion ofEFEdevelopment wasestimated tobeapproximately 0.9microliter perliter. CO2partially inhibited therapid increase ofethylene-promoted development ofEFE activity. Itissuggested thatethylene-promoted CO2production isinvolved intheregulation ofautocatalytic ethylene production inapples.