EFFECT OF PLANT NUTRITION ON THE AMINO-ACID COMPOSITION OF WHEAT PROTEINS
ARMY BIOLOGICAL LABS FREDERICK MD
Pagination or Media Count:
Conditions of nitrogen and potassium-phosphorus nutrition of plants have a substantial effect on the amino-acid composition of protein substances in wheat. With a nitrate source of nitrogen, the content of the aromatic amino acids tryptophan and tyrosine are substantially increased in wheat while given ammonia nutrition the cystine content is higher. This difference in the amino acid content is evidenced both in the vegetative and in the reserve proteins. An increase in the tryptophan and tyrosine content in the overall protein complex of the grain occurring for the nitrate nutrition of wheat is due to the sharp rise in the yield of middlings, which contain considerably more of these proteins in its protein content than gluten proteins. Nitrogen top dressing of wheat during the earing period results in a sharp increase in gluten yield. A decrease in the percentage content of amino acids occurs simultaneously in this case. However, the absolute percentage of amino acids in gluten due to its high yield is not reduced. When wheat is inadequately supplied with phosphorus a sharp rise in gluten yield and decrease in middlings content occurs. The tryptophan content in gluten protein with a phosphorus deficiency is substantially reduced. As a result, the total tryptophan content in the wheat grain drops in this case. Thus, normal phosphorus nutrition is vitally important for tryptophan synthesis in wheat.