Ethylene Formation during Ripening of Kiwifruit

Kiwifruits (Actinidia chinensis Planch. cv. Hayward) began to produce ethylene at an increasing rate (exponentially) at 21°C after reaching the threshold level of 0.1μlkg-1h-1. The high rate of ethylene production is associated with fruit ripening. The time required for the fruits to reach the threshold level became much shorter and the wide range of variation in the time became less after fruits were stored for 4 months and longer at 2°C. Both 1-aminocyclopropane-1-carboxylic acid (ACC) and N-malonyl-ACC (MACC) levels increased in proportion to the rate of ethylene production in the range higher than 0.2nmolg-1h-1, below which both ACC and MACC levels remained almost constant. Ethylene-forming enzyme (EFE) activity increased in parallel with the rate of ethylene production, which may indicate that EFE activity regulates ethylene production in the fruit tissue as well as the step of ACC formation.