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. 1990 Dec;94(4):1505–1511. doi: 10.1104/pp.94.4.1505

Distribution and Metabolism of Xylem-Borne Ureido and Amino Compounds in Developing Soybean Shoots 1

Barry J Shelp 1,2, Maria C Da Silva 1,2
PMCID: PMC1077413  PMID: 16667883

Abstract

Pulse-chase feeding (30-120 minutes) of 14C-labeled nitrogenous compounds to cut transpiring shoots was used to investigate the early fate of the major xylem-borne solutes in N2-fixing soybean (Glycine max) plants at the V4 growth stage. By comparison with the foliar distribution of [14C]inulin (a xylem marker), it was determined that the phloem supply of allantoin, allantoic acid, asparagine, glutamine, aspartate, and arginine, respectively, provided about 20, 10, three, two, five, and 20 times the 14C delivered to the developing trifoliolate in the xylem stream. Recovery of unmetabolized asparagine, aspartate, and arginine in this indicator trifoliolate, and significant declines in the percentage of 14C from allantoic acid and allantoin recovered in the first trifoliolate, provided some support for the direct xylem-to-phloem transfer of these compounds, but did not preclude the involvement of indirect transfer. Data on stem retention and foliar distribution, expressed as a function of the relative xylem sap composition, indicated that ureides provide the major sources of nitrogen to all plant parts. There was no consistent distinction in distribution patterns between pairs of similar anionic and neutral compounds. The extent of xylem-to-phloem transfer among the ureido or the amino compounds was inversely related to its prominence in xylem sap.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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