Effects of Nitrogen Fertilizer on Activities of Key Enzymes of Carbon and Nitrogen Metabolism of Different Flue-cured Tobacco Varieties

To study the effects of nitrogen fertilizer on activities of key enzymes of carbon and nitrogen metabolism of different varieties of flue-cured tobacco,this paper carried out field experiment and determined the changes in activities of nitrate reductase( NR),glutamine synthetase( GS),glutamate dehydrogenase( GDH),sucrose phosphate synthase( SPS),sucrose synthase( SS) of 2 varieties of flue-cured tobacco,Honghuadajinyuan( H) and K326( K),under circumstances of N supplied and without N supplied. The results showed that the applying nitrogen fertilizer for the same variety can increase activities of NR,GS at the early growth stage of flue-cured tobacco; and the activity of GDH at the middle growth stage. At the same time,N supplying can increase the activity of SPS activity at early stage and activity of SS at the late stage. Under the same N supplying cases,activities of NR in K326 and SPS are higher than that in Honghuadajinyuan at early stage,so as the GDH activity in K326 during carbon metabolism period. Activity of GS in Honghuadajinyuan is higher than that in K326 at late growth stage. Nitrogen fertilizer can stimulate the nitrogen metabolism of different tobacco plant varieties. K326 utilizes nitrogen more than Honghuadajinyuan at the early stage,while at the late stage K326's reuse of nitrogen is less than Honghuadajinyuan. Therefore,in the process of flue-cured tobacco growth and development,adequate supply of nitrogen fertilizer should be ensured according to nitrogen demands of different flue-cured tobacco varieties.