Ethylene production by 'd'Anjou' pears during storage at chilling and nonchilling temperature

To determine the ability of 'd'Anjou' pear fruit to produce climacteric ethylene postharvest, fruit were harvested at a mature green stage, chilled at -1 degrees C for various times, then transferred to 20 degrees C to ripen. In addition, fruit were first held at 20 degrees C for various times, then at -1 degrees C for various durations, followed by transfer to 20 degrees C for 11 days. As storage time at -1 degrees C increased from O to 70 days, the time required to induce climacteric ethylene when transferred to 20 degrees C progressively decreased from 90 to 0 days. The total storage time (sum of d at chilling and nonchilling temperature) needed to induce climacteric ethylene remained nearly constant (70 to 90 days). However, this was not the case with fruit held initially at 20 degrees C, then transferred to -1 degrees C. The total storage time needed before the pears produced climacteric ethylene ranged from 70 to 110 days and increased with time of storage at 2 degrees C. These fruit required more time at -1 degrees C than those first stored at -1 degrees C. The chilling requirement mechanism of 'd'Anjou' pears remains intact even during storage at nonchilling temperature and diminishes with senescence.