Abstract: The purpose of the paper was to study the effect of N, P, K fertilizer on the activeness of key enzymes involved in C and N metabolism during leaf development and the economic benefit of flue-cured tobacco. Four dif- ferent treatments （i. e. nitrogen,phosphorus,potassium deficiency and CK） were designed in a field experiment to study the enzyme activeness of nitrate reductase （NR）, Glutamina synthetase （GS）, sucrose phosphate syhthase （SPS）,sucrose synthase （SS） and invertase （Inv）. The results showed that NR was majored at the early growth stage of flue-cured tobacco. Compared with CK, the NR activity of N, P and K lack treatments decreased by 35.9%, 13.4% and 19.5%, respectively,but no significant difference was detected after 85 d of transplanting. In the process of carbon metabolism,the key enzymes SPS,SS and INV played a major role at the middle growth stage. N deficiency could decrease significantly the activeness of key enzyme,while P and K deficiencies had no obvious af- fect,probably because of the higher levels of phosphorus and potassium in the experiment plots. The effect of N lack on leaf yield and output value of flue-cured tobacco was the greatest compared to CK, decreased by 19.7% and 13.2% respectively,and the lack of P and K elements had no significant difference with CK. This indicated that N fertilizer should be sufficient,and P and K elements should be controlled properly in order to obtain flue-cured to- bacco with high yield and good quality.

Key words: Nitrogen phosphorus potassium , Flue-cured tobacco, Carbon and nitrogen metabolism, Yield Out- put value

CLC Number: 

• S572