EFFECT OF APPLYING INCREASING LEVELS OF NITROGEN TO RYEGRASS .2. AMINO ACID COMPOSITION OF PEPTIDE AND PROTEIN FRACTIONS

Amino acid concentrations in the peptide fraction of S22 ryegrass increased with total N content but when amino acid N was expressed as percentage of peptide N little variation was noted with increasing maturity or with increasing level of N application. Also under these conditions true protein increased but when expressed as a percentage of total protein N there was little change in the amino acid make‐up of this fraction. Total dicarboxylic amino acid N and amide N maintained a 1 : 1 ratio in the peptide fractions under these conditions. Glycine and phenylalanine contents were relatively higher in the peptide fractions, and leucine and valine contents were relatively higher in the protein fractions. Proline content was unusually high in the free state, intermediate in the peptide fraction and lowest in the proteins. The amino acid make‐up of the peptide fraction was more closely related to the protein fraction than to the free amino acid fraction and the free amino acids and their amides had some influence in determining the composition of the peptide fraction. Copyright © 1969 John Wiley & Sons, Ltd