Nitrogen Mobilization in Pea Seedlings. II. Free Amino Acids

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Abstract
Peas were germinated at 18[degree]C and harvested at intervals up to 5 days. Cotyledon and root-shoot axis tissue samples were taken for the younger seedlings; and cotyledon, root and shoot shaft, and root and shoot tip samples for the later seedlings. Free amino acids of 70% ethanol extracts were determined by ion exchange column chromatography. Amino acids were also determined on hydrolysates of some of the extraction residues. Homoserine, while practically absent in the seed, became the predominant amino acid in all tissues of 3- and 5-day seedlings, amounting to about 12% of the root and shoot shaft dry weight in 5-day seedlings. Arginine, asparagine, and gamma-aminobutyric acid were high in particular tissues. [gamma]-Aminoadipic acid and [beta]-alanine appeared to be present in all tissue samples. Similarity in the composition of corresponding tissues of roots and shoots was shown. The data give evidence of extensive inter-conversions and metabolism of amino acids in seedlings.