The study looked at how different types and amounts of nitrogen fertilizer affect the growth and biochemical properties of tobacco seedlings. They found that NH4-N, NH4NO3, and NH2-N fertilizers helped increase protein content and soluble sugar accumulation in the seedlings. However, NO3-N fertilizer did not have the same positive effects. The best nitrogen fertilizer for tobacco seedlings was NH4NO3 at a level of 10mmol/L.