The field experiment was concerned on one new plant growth regulators (PGR,the main materia was N-carboxymethylchitosan,NCMC) on key enzymes of nitrogen metabolism in spring maize. The results showed that all the tested PGRs had significantly positive effects on promotion to the activities of nitrate reductase and protease in the functional leaves. The acticity of GS synthetase and GS transferase in both of the functional leaves and gr...