Research on carbohydrate metabolism in leaves of flue-cured tobacco under precised nitrogen management by using SPAD value

In order to study the effects on the physiological carbon metabolism of flue -cured tobacco under precise nitrogen management model based on SPAD value of tobacco leaves, using K326 as experimental material, the research studied the lower, the middle and the upper leaves爷carbohydrate content and carbon metabolism enzyme activity under two different treatments: the real-time nitrogen fertilizer topdressing method based on the SPAD value (SPAD threshold is 43) of flue-cured tobacco and the traditional nitrogen fertilizer used by local peasants. The leaves of the 4th, the 10th and the 18th leaf position represent the lower, the middle and the upper leaves separately. The results show that, with the growing of tobacco plant, the content of the total sugar, reducing sugar, sucrose, and starch in different leaf position show an increasing trend in both method of N fertilizing, while the content of the sucrose and starch in the middle and the upper leaves come down in the late stage of tobacco plant growing. The content of the reducing sugar, total sugar, sucrose phosphate synthase and amylase in tobacco plant using the nitrogen fertilizing method based on SPAD value is higher than those using the traditional nitrogen fertilizing method, while the content of the starch and starch phosphorylase is lower. The content of the sucrose and sucrose invertase is higher in the early tobacco plant growing stage, but lower than those using the traditional nitrogen fertilizing method in the late tobacco growing stage. Based on the results, the precise nitrogen fertilizing method based on SPAD value is caters tobacco plant physiological changes of carbon metabolism and conducive to the conduct of tobacco plant carbon metabolism.