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 °C for various times, then transferred to 20 °C to ripen. In addition, fruit were first held at 20 °C for various times, then at –1 °C for various durations, followed by transfer to 20 °C for 11 days. As storage time at –1 °C increased from 0 to 70 days, the time required to induce climacteric ethylene when transferred to 20 °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 °C, then transferred to –1 °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 20 °C. These fruit required more time at –1 °C than those first stored at –1 °C. The chilling requirement mechanism of `d' Anjou' pears remains intact even during storage at nonchilling temperature and diminishes with senescence.
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