A B S T R A C TThe changes in the composition of free and total amino aciak in wheat grain during development are described: the experiment was performed in a growth chamber with three varieties of winter wheat (Triticum aestivum L.): Splendeur, Hobbit and Maris Huntsman. The changes in the total composition of amino acids of the grain as development progressed were consistent with an increase in the proportion of storage proteins. A t 15 days after anthesis, the relative amount of glycine increased, suggesting that at this moment the proportion of gliadins was relatively low. The relative amount of arginine increased in mature grain, showing that at times close to maturity the relative proportion of synthesis of a protein fraction rich in this amino acid increased. Free glutamate, proline and arginine decreased at 15 days to a greater extent than the other amino acids and was present in low relative amounts during the period of maximum protein synthesis in the grain; these three amino acids could be the most limiting for protein synthesis in grain. In the free fraction the following showed a similar pattern of change during grain development: aspartate, arginine and histidine on the one hand, and on the other alanine, valine, leucine, isoleucine, threonine, phenylalanine and tyrosine; moreover both groups were inversely correlated. Glycine and lysine were directly related to each other and inversely to glutamate.

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The dgerences in the amino acid composition of the developing grain between the three winter wheat (

A B S T R A C TI n an experiment with three winter wheat (Triticum aestivum L ) varieties (Splendeur, Hobbit and Maris Huntsman) cultivated after anthesis in a growth chamber, the upper part of the ear was removed on several dates after anthesis (halving). The remaining grains accumulated more nitrogen, especially between days 5 and 25 after anthesis; the increase depended on variety, the date of halving and the stage of development. The relative composition of the protein was also affected, since the amino acid composition of the grain varied. I n the remaining grains the relative amounts of glutamate and, in general afer 15 days, those of proline and phenylalanine increased; by contrast those of aspartate, lysine and arginine, among others, decreased.The response of the three varieties was similar. A t maturity, the magnitude of the response was related to the variations occurring in the nitrogen (% D W ) .The stage of development in which the grain accumulated nitrogen supplement did not affect the regressions between the relative amounts of each amino acid and the nitrogen ( % D W). However, when the ears were halved on day 25 after anthesis, the relative amounts of glycine, lysine and arginine tended to be slightly higher, especially in the case of Hobbit, than the values that would correspond to these regressions. The departure from regression increased with increasing accumulations of nitrogen in the grain between day 25 and maturity.