| The accumulation of carbohydrates was an important way for plant against cold stress, and soluble carbohydrates were the most important osmotic regulation substances, which had been proved that this osmotic was positively correlated with the cold hardiness in many plants. Salicylic Acid(SA) can be used as a signaling molecule involved in mediation plants cope with adversity stress reaction, and also can raise the resistance of plants in a variety of environmental stresses. In the present study, 0, 0.5, and 1 mmol·L-1 SA was applied to deal with the elite freeze-tolerant wheat cultivar ‘Dongnongdongmai1’ and the general freeze-tolerant individual ‘Jimai22’, under condition of differential temperature such as 4, 0,-10, and-25 ℃ in the field. We measured the carbohydrates content, activities of key enzymes and gene expression levels to explore the effects of SA on sucrose metabolism in low temperature. The research not only can help to improve the understanding the effect of exogenous SA treatment on the mechanism of plant’s cold resistance, but also can explain the reason for the strong cold resistance of winter wheat, provide the theory basis for the application of exogenous SA increasing winter wheat cold resistance in field and the certain theory and practice foundation for explored new ways to high cold resistance crop.(1) Exogenous SA treatment reduced the relative conductivity in leaves and tillering nodes of the two winter wheats, which was beneficial to the improvement of the cold hardiness.(2) SA treatment increased soluble carbohydrates, it accumulated more soluble carbohydrates in Dongnongdongmai 1, which may be one of the reason of Dongnongdongmai 1 was elite freeze-tolerant but Jimai 22 was general freeze-tolerant.(3) SA treatment had increased the activities of enzymes associated with sucrose synthesis metabolize- sucrose phosphate synthase(SPS) and sucrose synthase(Su S) activity, and inhibition of the enzymes involved in sucrose catabolism- soluble acid invertase(SAInv) and alkaline / neutral invertase(A/N-Inv) activity. On the one hand, SA promoted the process sucrose synthesis, on the other hand, it inhibited the decomposition of sucrose, which had lead to the accumulation of sucrose.(4) SA treatment increased the relative expression levels of Ta SPS and Ta Su S, while reduced the relative expression levels of TaSAInv and Ta A/N-Inv, so that remained relatively sucrose accumulation in winter wheat in the molecular level.(5) Correlation analysis showed that exogenous SA treatment improved the correlation of sucrose content with the relative expression levels of Ta SPS and the correlation of SPS activity with the relative expression levels of Ta SPS; SA treatment also improved the correlation of sucrose content with the activity of SPS and Su S in leaves and tillering nodes. Sucrose metabolism not only involve in physiological adjustment such as enzyme activity, but also involved in molecular regulation of related enzyme gene expression, which can make the Dongnongdongmai 1 won a strong ability of cold resistance. |
