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Translocation of amino acids from stem nodules of Sesbania rostrata demonstrated by GC‐MS in planta 15 N isotope dilution
Author(s) -
Godber I. M.,
Parsons R.
Publication year - 1998
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1046/j.1365-3040.1998.00346.x
Subject(s) - xylem , nitrogen fixation , legume , amino acid , root nodule , sesbania , chemistry , fabaceae , ammonia , isotope dilution , bradyrhizobium , ammonium , botany , biology , nitrogen , biochemistry , mass spectrometry , chromatography , organic chemistry
We report a novel use of the 15 N dilution technique to detail the translocation of amino compounds in the legume Sesbania rostrata . The conventional 15 N dilution technique follows the dilution of 15 N within a labelled plant, as 14 N 2 is fixed by symbiotic bacteria. In our experiments, stem‐nodulated Sesbania rostrata were enriched by feeding with 15 N ammonium nitrate for 2 weeks, followed by a 1 week period where the only N available to the plants was via nitrogen fixation of atmospheric N 2 . We measured the composition, concentration and 15 N enrichment of amino compounds in various plant tissues, both above and below the stem nodules, using GC‐MS and isotopic abundance mass spectrometry techniques. Approximately 28% of the total N in the stem nodules was derived from internal plant sources. The ureides allantoic acid and allantoin were not abundant in xylem, leaf or nodule tissues. The amides asparagine and glutamine were the major export products from stem nodules although a wide range of other amino compounds are also synthesized. Amino acids within the nodules had a low level of enrichment, demonstrating that a small fraction (≈ 11%) was derived from outside the nodules, and significant cycling of N (28% of xylem N) through the root system was revealed by measurements of 15 N distribution and amino acid concentrations.