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The contents of reducing sugar, sucrose, starch and fructose-2,6-bisphosphate (F-2,6-P_2) in relation to the activities of amylase, invertase and fructose-1,6-bisphosphatase (FBPase) were investigated from the leaves of rice (Oryza sativa L. cv. Samjin) seedlings grown at 4℃ for 3 days. In the seedlings, the contents of reducing sugar and sucrose were increased, but soluble and insoluble starch were declined. Under this condition, amylase activity was increased, but acid invertase activity was declined and alkaline invertase activity was not changed. Cytosolic and stromal FBPase activities were increased. But F-2,6-P_2 content was declined. It seemed that the increase of reducing sugar content might be due to the increased activity of amylase and the increase of sucrose content might be related to the increased activity of cytosolic FBPase, reduced content of F-2,6-P_2 and reduced rate of hydrolysis of sucrose during the cold treatment. These results suggested that the changes in carbohydrate metabolim of rice seedlings under low temperature reflect one of the protection mechanism to the low temperature during the cold treatment.
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