Postharvest Response of Avocado Fruits of Different Maturity to Delayed Ethylene Treatments

The effect of 10, 100, 1000, 10,000 ppm of ethylene, applied for 3, 6, 12, and 24 hours, on the ripening rate of "Hass" avocado (Persea americana Mill.) fruits at three stages of maturity was investigated. Ethylene treatments were started either immediately after picking or 2 days later. A sharp peak of ethylene production was found to precede full softening by about 2 days and the occurrence of this peak was used to determine ripening rate. Hastening of fruit ripening was much more marked following ethylene treatment which began 2 days after harvesting than immediately after. The difference in response diminished gradually as the fruit became more mature.These results can be explained by the assumption that the factors which prevent avocado ripening on the tree, continue to exert their influence for a limited period after harvest and inhibit the ripening response in the freshly picked fruit. This inhibition decreases with advancing fruit maturity.