| The world citrus industry has been influenced seriously by the injury of periodically low temperature. Much effort has been made to improve the cold tolerance of citrus crop through various breeding methods, however, up to date little progress has been made since the mechanism of citrus cold tolerance has been remaining unknown. In the present study, some biochemical changes and functional proteins induced by cold stress in growth season were investigated in two-year-old potted plants of trifoliate orange (Poncirus trifoliata Raf.), which was the most cold-tolerant among citrus species, and Miyamoto satsuma mandarin (Citrus reticulata Blanco cv. Miyamoto), less cold-tolerant than the former. The results were as follows:(1) The soil temperature in the pots wrapped with cotton was 6°C to 9.5°C higher than that in bald pots.(2) No injury symptom appeared when the potted plants were treated with -6°C 10 min to 50 min for trifoliate orange and -6°C 10 min to 30 min for Miyamoto satsuma mandarin, respectively, with the electrolyte leakage less than 25%, activities of POD and CAT declining and contents of Pro and MDA stable changing. However, obvious injury symptom was observed when the potted plants were treated with -6°C 60 min for trifoliate orange and -6°C 40 min for Miyamoto satsuma mandarin, respectively, with the electrolyte leakage more than 50%, POD and CAT activities and MDA content reaching their maximums, Pro content reaching maximum in trifoliate orange but minimum in Miyamoto satsuma mandarin.(3) The lethal temperatures of trifoliate orange and Miyamoto satsuma mandarin were -6°C for 60min and -6°C for 40min, respectively.(4) A high quality 2-DE profile was obtained. The proteins were separated very well in both dimensions.(5) Employing PDQuest 7.2 software to analyze 2-DE gels, up to 378 protein spots were...
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