Effects of exogenous abscisic acid on carbohydrate metabolism and the expression levels of correlative key enzymes in winter wheat under low temperature.

Two wheat (Triticum aestivum) cultivars, freeze-tolerant Dongnongdongmai 1 and freeze-sensitive Jimai 22, were used in this study. They were grown under field conditions, the leaves were sprayed with 1 × 10(-5) mol/L ABA and distilled water as control respectively at the three-true-leaf stage. Application of exogenous ABA increased the accumulation of carbohydrates in both cultivars, mainly in sucrose and fructose, except that the fructose content decreased in the leaves of Jimai 22. Exogenous ABA also enhanced the expression of key enzyme genes, especially in Dongnongdongmai 1 above 0 °C and in Jimai 22 below 0 °C. The carbohydrate contents and expression levels of the genes encoding key enzymes showed co-regulation in some, but not all of the pathways examined. Taken together, the higher sugar accumulation and the upregulation in expression of key enzymes in freeze-tolerant Dongnongdongmai 1 due to exogenous ABA suggest that active carbohydrate metabolism is mainly associated with the freeze tolerance of Dongnongdongmai 1.