橫山梨果實採收後生理及低溫障礙

Postharvest Physiology and Chilling Injury of Harvested 'Hang Shan' Pear Fruits

0～20°C，橫山梨果實的乙烯釋放量隨溫度的上升而升高，於20°C時至少達80μl/kg•hr；20°C以上則隨溫度的升高反而有減低的趨勢。不同成熟度果實在10°C及10°C以上皆具乙烯高峰，其上升時間隨溫度或成熟度降低而延緩。橫山梨果實的呼吸率則呈現和緩上升現象，其開始上升與上升之趨勢與急速增加的乙烯釋放率不盡相同。每隔20天採收之更年前期橫山梨果實分置於0、5和10°C中，每4或8天移出至20°C或不移出，其低成熟度者於升溫後均能正常後熟，但置於0°C中16天者，果肉已呈現褐化現象；中、高成熟度者在0或5°C中經8天移出後，其乙烯釋放率則不再出現高峰，而呼吸率於達到平穩時略高於20°C對照組者；凡無乙烯高峰出現的試驗組，其果肉均已嚴重褐化，此症狀顯然為低溫傷害的結果。與果肉業已軟化的乙烯高峰期或後期果實相較，更年前期階段的橫山梨果實對低溫較為敏感，且以愈接近乙烯上升始點（onset）者尤甚。

Ethylene production of the harvested 'Heng Shan' pear fruits increased with raising temperature between 0 and 20°C. Its maximum rate in 20°C was over 80µl/kg•hr. However, ethylene evolution decreased when the temp was higher than 20°C. 'Heng Shan' pear fruits picked at 3 different developmental stages all showed rise in CzH4 evolution during storage at the temp of 10°C or above. The lag period before sudden rise in C2H4 evolution shortened with more advancing maturity or higher storage temperature. Respiration rate increased gradually and did not appear to be well correlated with the sharp rise of CzH4 evolution during ripening even this commodity was suggested as climacteric fruits. Pre-climacteric 'Heng Shan' pear fruits were harvested at 20-day intervals and stored at 0,5 and 10°C for 16 days or for 4 or 8 days then transferred to 20°C. The low-maturity fuits following storage at 0 or 5°C for 4 or 8days ripened normally after their transfer to 20°C, but those stored at 0°C for 16 days did not ripen and their flesh became brown and water-soaked. Those middle- and high-maturity fruits following storage at 0 or 5°C for 8 days failed to show the typical C2H4 peak althongh they had somewhat higher respiration rates than those kept continuously at 20°C. These stored fruits without a rise in C2H4 concentration developed water-soaked and browning symptoms. These symptoms were apparently caused by chilling temperature. The low-maturity fruits were the most resistant to the chilling temperature. Furthermore, fruits at the climacteric peak or post-climacteric stage were less susceptible to low temperature than those at pre-climacteric period.