Abstract: Effects of nitrogen fertilizer rate on nitrogen metabolism and protein synthesis of the superior and inferior wheat kernel were studied. The results showed that the protein content and accumulation amount of the superior kernel were higher than that of the inferior kernel during filling, and that GS (glutamine synthetase) activities during 21 days after anthesis and free amino acids content during 28 days after anthesis in super kernel were significantly higher than that of inferior kernel, which accounted for the faster protein accumulation in the superior kernel. At maturity, with the same nitrogen fertilizer rate, the content of albumin, gliadin, glutenin and GMP (glutenin macropolyer) of superior kernel was higher than that of inferior kernel, while the globulin content in superior kernel was lower. Appropriate application of nitrogen fertilizer increased the protein content and accumulation amount in kernel, and decreased the difference in free amino acids content, soluble protein content and GS activity between superior kernel and inferior kernel, and the difference in protein content and accumulation amount. With nitrogen supply increased from 150 kg·ha-1to 240 kg·ha-1, protein content of inferior kernel increased, but no significant difference occurred in protein content of superior kernel. With the nitrogen fertilizer rate increased, the content of protein components increased by different extents, and the content of glutenin and GMP of inferior kernel improved mostly, showing that nitrogen addition effects on the content of protein and its components occurred mainly on inferior kernel.

Key words: Winter wheat, Nitrogen fertilizer rate, Superior kernel, Inferior kernel, Nitrogen metabolism, Protein synthesis