Degreening Response of ‘Hamlin’ Oranges in Relation to Temperature, Ethylene Concentration, and Fruit Maturity1

Abstract

Abstract ‘Hamlin’ oranges were degreened for 1, 2, or 4 days in ethylene concn of 0 to 50 ppm and at 21, 24, 27, and 30°C. The initial rate of chlorophyll loss was more rapid at 30°C than at 21°C. Subsequent changes at 21°C were such that the fruit reached an acceptable color almost as rapidly as at 30°C. After 4 days’ degreening, fruit at both temp showed the same response pattern to the range of ethylene concn used, with the optimum response attained with ethylene concn between 5 and 10 ppm. After short degreening periods, changes continued after removal from the ethylene atmosphere. Responses at 24 and 27°C were similar to those at 21 and 30°C, respectively. No evidence of a seasonal change in the response to ethylene was shown. Stem-end decay generally was greater with increasing ethylene concn, temp, and length of the degreening period. Interactions among these variables were such that increasing the temp or length of degreening period resulted in greater increases in decay at high rather than at low ethylene levels.