Journal of the Japanese Society for Horticultural Science
Online ISSN : 1880-358X
Print ISSN : 0013-7626
ISSN-L : 0013-7626
Metabolism of 14C-L-Arginine and 14C-L-Proline in Excised Burst Buds and Stem Sections of Citrus Trees (Citrus unshiu Marc.)
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1985 Volume 53 Issue 4 Pages 412-418


Arginine and proline, which are the major forms of soluble reserve N, were fed singly in uniformly labelled 14C-form to excised 2-year-old stem sections with a new shoot, to wood sections, and to burst buds from a 21-year-old satsuma mandarin tree. Metabolism was studied by radioassay and autoradiography.
In stem sections with a new shoot, both 14C-compounds were metabolized to acidic and neutral components, insoluble components, and 14CO2. This conversion occurred to a greater extent in sections fed with arginine than with proline. When 14C-arginine was fed, the highest 14C-activity in the cationic fraction of stem sections, bark, wood and new shoots was found in γ-guanidinobutyric acid, followed by γ- aminobutyric acid and proline; low levels of 14C was also found in ornithine and trace amounts in citrulline. These findings demonstrate that arginine is metabolized by at least two routes: via ornithine and via γ-guanidinobutyric acid. In every organ, the major metabolic products of 14C-proline were pyrrolidone-5-carboxlic acid, glutamic acid, aspartic acid, asparagine, an unidentified compound(U5 in Fig. 4), γ-aminobutyric acid and arginine. The basic metabolic pathways in the conversion of both 14C-compounds were the same in burst buds, new shoot, bark and wood, although there was a slight difference autoradiographically.

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