Abstract: Under deficient-N condition, the yield and nitrogen use efficiency were all the highest in the wheat varieties with high-N efficiency (H), then in the varieties with mid-N efficiency (M), and the lowest in the varieties with low-N efficiency among all tested varieties (L). H also had the highest spike number per planting area and correlated with the grain yield and N efficiency significantly, indicating the spike number per planting area has important effects on yield and N efficiency of wheat varieties under deficient-N condition. There were no obvious differences in total nitrogen concentration of plant among the tested varieties. At spiking stage and maturity stage, the accumulative nitrogen amount of plant was the highest in H, then in M, and the lowest in L, showing that the nitrogen absorption capability of plant at mid- growth to late- growth stage has important influence on the grain yield and N efficiency under deficient-N condition. The plant height, stem number of population, leaf area index (LAI), dry weight of population (PDW), NO3- content and nitrate reductase (NR) activity of leaf at each growth spring stage were all the highest in H, then in M and the lowest in L. So was the canopy growth rate (CGR), net assimilation rate (NAR) and photosynthetic potential (Pp) at each spring growth phase. There were little differences on nitrite reductase (NIR) activity and glutamine synthetase (GS) activity among tested varieties. The study indicated that it is the important physiological factor for the high-N efficiency variety to have a higher absorption capability of nitrogen and better growth and development traits of plant. Under sufficient-N condition, it was not always the same on yield, nitrogen use efficiency, nitrogen uptake and day matter production as those under deficient-N condition.

Key words: Wheat（Triticum aestivum）, Nitrogen use efficiency, Uptake of nitrogen, Dry matter production