AMINO‐ACID METABOLISM IN GERMINATING SEEDS OF VICIA FABA L. IN RELATION TO THEIR BIOLOGY

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SummarySeeds of Vicia faba L. were grown without an external nitrogen supply and the amount of nitrogen in free amino acids, protein amino acids and other soluble nitrogenous compounds determined in the various tissues of ungerminated, 6‐ and 14‐day‐old material.It was found that, on germination, the reserve proteins of the beans were hydrolysed to give at least some free amino acids which were then interconverted and used in the synthesis of new compounds. Glutamine was not formed extensively until after 6 days of growth and the synthesis of this amino acid may be related to the prior onset of photosynthesis which might supply necessary carbon precursors.The proteins of the ungerminated beans were shown to contain a high proportion of nitrogen in basic and dicarboxylic amino acids and during germination major changes occurred during which all these amino acids decreased in amount. Arginine played an important part in the metabolism of the seedlings and the results of preliminary 14C feeding experiments indicate that it may be degraded by a reversal of the ornithine cycle. The decrease in the amount of arginine, other basic amino acids and the dicarboxylic amino acids are discussed in terms of their metabolism and utilization as intermediates in the synthesis of proteins and other nitrogen constituents necessary for the establishment of autotrophic nutrition.