Abstract:Cytokinln stimulates the induction of nitrate reductase (EC 1.6.6.l, NR) ABT inhibites the induction of NR and counteractes the effect of 6-benzyladenine (6-BA) on the induction of NR. 6-BA alone could not induce NR activity and the effect of 6-BA became stranger when appropriate concentration of NO3- induced higher NR activity. In the dark a little NR activity was induced by NO3- in etiolated leaves and the effect of 6-BA was very weak at the same condition. Cycloheximide depresses the induction of NR by NO3-. These results showed that the accelerative effects of cytokinin on NR induction was a indirect action depending on NR inducing process rather than on the presence of NO3- alone.