Studies On Chilling Injury Of Honey Dew (Cucumis Melo L.)

Honey Dew is mainly varity of melon grown in Northwest China. Storage under low temperature could prolong storage periods evidently, controlled the growth of fungi.But it is sensitible to temperature and chilling injury at low temperature.Thus,it is useful to study the process of chilling injury of Honey Dow. The critical temperature and symptoms of chilling injury of Honey Dew,effects of chilling injury on cellularity and ultrastructure of Honey Dew fruit, Storage quality and diseases of Honey Dew melons and membrane lipid peroxidation, activity of SOD and POD, proline, soluble protein and sugar contents of Honey Dew fruits under chilling (2℃,4℃,7℃)and un-chilling temperature(9℃)were studied in this article. The results showed that the critical temperature of Honey Dew was between 5℃and 7 ℃. Cultivars with different skin colour or from different growing conditions differed in symptoms and storage duration before chilling injury occurred. According to apperant symptoms, chilling injury can be identified three phases: water-soaking , pitting and browning. Roughly two types can be identified among the 5 cultivars from chilling injury symptoms. Chilling injury caused cell fasciate. Cellular ultrastructure observation showed that microfibril was decreased, and the nuclear envelop and plasmalemma disintegrated. Cell deformation caused by low temperature was the direct reason that chilling injury resulted in Honey Dew fruit chilling injury symptoms and quality deterioration. But mitochondria had strong fastness of low temperature. The results also showed that with the decrease of storage temperature, the activity of SOD and POD decreased .But under chilling injury temperature POD demonstrated a peak in 7 days and MDA increased sharply in 21days. The Pro content became higher at the beginning of stressing and lowered later on. The temperature has the same effects on soluble protein and soluble sugar, the lower the temperature, the higher the cell contents of these indexes. Flesh permeability and leakage of K+, Na+ and Ca2+ of Honey Dew at different temperature were studied. The results showed that Chilling injury made cell fasciate. Cellular ultrastructure change showed that microfibril was decreased, and the nuclear envelop, plasmalemma disintegrated. Cell deformation caused by low temperature was the direct reason that chilling injury resulted in Honey Dew fruit chilling injury symptom and quality deterioration. But mitochondria had strong fastness of low temperature. Optimum storage temperature for Honey Dew fruits was 8-10℃which brought about good marketing quality and control on disease pathogen. Honey Dew fruits stored at 4-5℃suffered chilling injury and showed shortened storage life mainly due to combined infection of fungi. High storage temperature of 19-20℃promoted disease development and quality decrease of Honey Dew melons.