In order to study the influence of nitrogen applied rate and remained leaf numbers on tobacco root activity and N, P, K content in tobacco plant organs, we used tobacco variety HY -9 -7 as experiment material. The results showed that the root activity increased with nitrogen applied rate increased at the early growth stage of tobacco. At the late growth stage, root activity increased with the nitrogen applied rate increased under the same remained leaf numbers, and it showed increase - decrease trend with the remained leaf numbers increased under the same nitrogen applied rate. With the nitrog...