EFFECT OF NITROGEN FERTILIZER ON NITROGEN FRACTIONS AND AMINO ACID COMPOSITION OF SPRING WHEAT

Grain from hard red spring wheat (Triticum aestivum ’Neepawa’) grown with nine rates of N fertilizer (0–400 kg/ha) was analyzed for total N, non-protein N (NPN), and amino acids. In addition, the amino acid compositions of the various soluble protein fractions were determined. The percentages of total N, NPN, and protein N of the grain increased with each 50-kg increment of N up to the 150-kg rate. The proportions of glutamate, proline, and phenylalanine in the seed increased whereas threonine, serine, glycine, alanine, and valine decreased with the first three or four increments of N fertilizer. With increasing N content in the seed, the proportions of albumin, globulin, and glutenin 2 decreased while the proportions of gliadin and glutenin 1 increased. The various protein fractions differed from each other in amino acid composition but the amino acid composition of each fraction was not influenced significantly by N application.