Abstract: The effects of nitrogen forms on different flue-cured tobacco seedling roots, leaf soluble protein and associated enzyme activities were studied in different genotypes of flue-cured tobacco K326, Zhongyan 90 (ZY90) and Jingyehuang (JYH). The results showed that in different NO-3-N and NH4 +-N treatments, nitrate reductase (NR) activity in JYH leaves was higher than the other two genotypes, and NR activity in ZY90 roots was higher, furthermore, NR activity in NH4 +-N treatments was higher than in NO-3-N treatments. Glutamine synthetase (GS) activity in K326 leaves and roots were higher than the other two genotypes, and GS activity in root was much larger than in leaves. GS activity in leaves in NH4 +-N treatment was lower than NO3 --N treatment level,and GS activity in roots in NH4 +-N treatment was higher than NO3 --N treatment. Soluble protein content in JYH leaves and in ZY90 roots were the highest. There was no positive correlation between NR, GS activity and nitrogen levels.

Key words: flue-cured tobacco, nitrate reductase, glutamine synthetase, soluble protein