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In order to achieve high yielding cultivars with appropriate quality in wheat, it is important to understand the physiological bases of nitrogen nutrition. In this experiment six cultivars of bread wheat (Triticum aestivum) including high and low grain protein content were studied. Two nitrogen fertilizer levels were applied using a split plot design with 4 replitations. Plant shoots were harvested in 5 stages, including : 3 leaves unfolded, beginning of stem elongation, booting, anthesis and full maturity during the plant development. Dry weight and shoot nitrogen percent were measured using the kjeldahl method. Results indicated that nitrogen concentration at the first stage of growth was maximum, and reduced gradually with relative decreases in nitrogen uptake. However, nitrogen uptake continued during the post-anthesis stages. Significant differences between cultivars for dry weight and nitrogen concentration were found at the most growth stages. After ear emergence, nitrogen concentration was higher in the aerial parts of the high protein cultivars than the low protein cultivars and had a positiye correlation with grain protein concentration. Therefor, nitrogen remobilization efficiency from vegetative parts to the grain was significantly higher than the low protein cultivars. While, the post anthesis nitrogen uptake difference was nonsignificant among cultivars.It appeared that the higher nitrogen remobilization efficiency was the main reason for the higher protein percent in the higher protein cultivars.