The Free Amino Acids in the Leaves, Roots, and Root Nodules of the Alder (Alnus).

1) Paper chromatographic analysis revealed that citrulline is the predominating free amino acid in the root nodules of A. incana and A. glutinosa throughout the year. In autumn its concentration has increased 5-10 fold, compared with the summer value. 2) The nodules of A. incana contain in addition to citrulline much γ-amino butyric acid, which evidently is formed from L-glutamic acid, since L-glutamic acid decarboxylase aclivity was found to be present in the insoluble residue of the crushed nodules. 3) The roots of A. glutinosa contain in addition to citrulline much arginine and ornithine but the nodules have only traces of them. The concentration of free amino acids in the roots near to the nodules is about 5 times that in the more remote parts if calculated per unit dry matter. 4) The completely unnodulated roots of uninoculated alders grown on combined nitrogen also contain citrulline, hence, it is not a compound specific to nitrogen fixation. 5) The stems and especially the leaves of alder contain considerably less citrulline and soluble nitrogen in general than the roots of the same plant. 6) The presence of urea and the identity of citrulline were tested paper chromatographically using p-dimelhylaminobenzaldehyde reagent. Only in unnodulated roots was urea found and then only in very small quantities (about 0.005 per cent of dry wt.), possibly as the result of a secondary splitting. The identity of citrulline in all extracts was confirmed. 7) The arginase activity of the alder nodules, roots and leaves was tested. No activity could be detected. 8) The amino acids extracted with ethanol were separated from many impurities in the extract by means of alkaline ion exchange resin Dowex 2. 9) L( + )-citrulline was also isolated from the nodules of A. incana as the Cu-salt. This was identified by means of the mixed melting point with the authentic Cu-L(+)-citrullinate. 10) In the nodule extract of A. incana two unknown compounds were found, possibly peptides, which disappear in the HCl-hydrolysis. Simultaneously alanine, glutamic acid, some glycine and possibly γ-amino butyric acid are set free. 11) Citrulline was noted to break down to a great extent to ornithine in the HCl-hydrolysis. 12) In one preparation citrulline was also determined photometrically by diacetylmonoxime reaction. 13) Hypotheses are advanced on the significance of the observations. [ABSTRACT FROM AUTHOR]