Abstract: The purpose of this work is to examine the relation between NR and NRSF in the leaves of the wheat plants under the different environmental conditions. The leaves of wheat plants which were grown in the nutritional solution containing NO3-, present 15 times higher of NR activity than that grown in the nutritional solution containing NH4+, but NRSF, which activated NO3-NR of the former increased only 20% as compared with that of the latter, indicating that NR is independent of NRSF. In addition, in the yellowing leaves dark grown in NO3-N solution and those in the same solution containing W with no nitrogen and Mo, the NRSF is quite stable, and keep higher activity, but no NR activity can be determined. So the NRSF is not considered as a major factor to regulate activity of NR in the leaves.

Key words: Environmental conditions, Nitrate reductase-stabilizing factor (NRSF), Nitrate redutase (NR)