The amino acid composition of several protein fractions of developing wheat endosperm (cv. Gabo, grown in 1960 in Adelaide) was determined by ion-exchange chromatography. There were considerable differences in the compositions of the fractions extracted by pyrophosphate, acetic acid, and by sodium hydroxide. The composition of the fraction extracted by acetic acid remained relatively constant during development whereas there were changes in the compositions of the fractions extracted by pyrophosphate buffer, and by sodium hydroxide. The amino acid composition of the total protein body fraction, at day 18 and at day 46 after flowering, showed little change during development. However, there was considerable difference in composition between the total protein body fraction and a fraction of small protein bodies obtained by gradient centrifugation. The results suggest that the amino acid composition of the protein bodies may change during growth and development of the protein body. The number of protein bodies increase during development of the endosperm; the increase in the amount of residues of amino acids in the protein body fraction during endosperm development confirms that the protein bodies are the sites of accumulation of storage proteins in endosperm.

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