When the contents of urea-nitrogen were 75%, tobacco seedlings growth was obviously restrained, photosynthesis and the NR activity reduced, the root absorbing ability dropped than CK.

• 与对照相比，当尿素态氮为75%25时，烟苗的生长受到明显抑制，叶片的光合特性和NR活性降低，根系吸收能力下降。