| The objective of this study is to investigate the effect of high oxygen on storage life, physiology and biochemistry of posthharvest fruit. The results are as follows.1. Effects of high oxygen on color, firmness, respiratory rate, ethylene production and relative permeability of banana fruit. Exposure of banana fruit to high oxygen concentrations accelerated changes in skin color, resulted in pulp softening, increased permeability of cell membrane and shortened peaks of respiration rate and ethylene production. Furthermore, the effects were more obvious as oxygen concentrations increased.2. Effect of high oxygen on active oxygen metabolism. Application of high 02 concentrations accelerated O2 production and H2O2 accumulation, stimulated activities of SOD, POD and CAT at the early stage of storage. Due to unbalance between accumulation of superoxide anion and hydrogen peroxide and the capacity of antioxidant systems, there were enhanced lipid oxidation and a high MDA level resulting in the senescence of the fruit. Moreover, the senencence became more obvious with increased O2 concentration.3. Effect of high oxygen on energy charge. 100% O2 and 60% O2 significantly accelerated decrease in contents of ATP and ADP, and level of energy charge of fruit peel and flesh. Whereas the contents of ATP and ADP, and the level of energy charge of banana fruit exposed to 21% O2 were relatively high, with slight reduction at the late stage of storage. The change in AMP content of banana fruit exposed to four oxygen concentrations was contrary to that of ATP content.The preliminary study suggested the senescence of banana fruit caused by high O2 treatments may relate to accelerated ethylene produtction, enhanced respiration, decrease in the capacity of antioxidant systems and increased damage of membrane structure; the possible mechanism of high oxygen which caused the senescence ofbanana fruit, involving in the loss of energy charge, was discussed.
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