• Journal of Bio-Environment Control
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• v.10 no.4
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• pp.244-250
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• 2001

This study was conducted to determine the change in freezing tolerance of Chinese cabbage (Brassica campestris L. ssp. penkinensis). Four-week old seedlings grown in a greenhouse at $25^{\circ}C$$\pm$0.5 were transferred to 5, 10 or 15$^{\circ}C$ condition for acclimation for one day, and then transferred to a lethal temperature of -3$^{\circ}C$ condition. Optimal acclimation temperatures were 5$^{\circ}C$ and 1$0^{\circ}C$. Freezing tolerance of leaf tissues was investigated during a week-long cold stress. Development of freezing tolerance was shown by survival ratio, and amounts of total RNA, soluble protein and soluble sugar. LT$_{50}$ value increased from -3 to -4$^{\circ}C$ after 5 days acclimation at 5 or 1$0^{\circ}C$, and this was considered to be the first indication of enhanced freezing tolerance. Plants, cold acclimated for five days, reached to a survival ratio of 60%. This increase in freezing tolerance was found to be associated with the increased levels of total RNA, soluble sugar and soluble protein. These metabolic changes imply the association of adjustment of growth and cell metabolism with low temperatures at the beginning of cold acclimation in chinese cabbage.e.