Response of apples to diazocyclopentadiene inhibition of ethylene binding

Abstract

Diazocyclopentadiene (DACP) is a light-activated compound that is thought to inhibit ethylene binding in plants. DACP was applied as a gas in the light for 24 hours to ‘Red Delicious’ apples harvested at a mature, preclimacteric stage. Treated apples held in air at 21°C for 30 days had lower internal ethylene concentrations than untreated fruits. Higher concentrations of DACP were more effective over longer periods of time. Untreated apples had a flesh firmness of 46 newtons after 30 days, while DACP treated apples were about 73 newtons. Starch conversion initially was slowed by DACP, but by 30 days all starch was lost. Retreatment of fruit with DACP during the 30 days did somewhat renew the effect on suppression of ethylene, but did not further effect flesh firmness or starch conversion. Apples treated once with DACP at harvest, then held in 0°C cold storage, contained much lower levels of internal ethylene and were approximately 10 newtons firmer after 18 weeks than untreated fruit.