Abstract: Plants of marrow (Cucurbita pepo L.) were grown in a controlled environmental chamber and were submitted to different concentrations of cadmium (Cd) applied to NO3¯ the nutrient solution at 0, 10, 20, 30, 40 and 50 μM. The activities of primary nitrogen enzymes as well as ammonium ion contents were investigated in both roots and shoots of marrow seedlings. Toxic cadmium ion accumulation in seedlings significantly modified activity of primary nitrogen assimilating enzymes. There were significant decreases in glutamine synthetase (GS; EC 6.3.1.2), glutamate synthase (GOGAT; EC 1.4.1.13), nitrate reductase (NR; EC 1.6.6.1) and nitrite reductase (NiR; EC 1.6.6.4) activities in both root and shoot of the seedlings. In contrast, the same previous Cd concentrations expressed significant increase in glutamate dehydrogenase (GDH; EC 1.4.1.2) activity in both shoot and root of the same seedlings. Corresponding with the increase in glutamate dehydrogenase activity, ammonium ion contents in shoots of cadmium treated seedlings, showed significant increase with the increase in cadmium concentration. However, ammonium ion contents of roots of the same seedlings, exhibited significant increase up to 30 μM Cd only. These results suggest that, in general, treatment with Cd2+ affect nitrogen assimilation and metabolism to a great extent in both roots and shoots of marrow seedlings.