Skip to main content
PMC home page
Plant Physiology logoLink to Plant Physiology
. 1997 Jan;113(1):259–267. doi: 10.1104/pp.113.1.259

Phloem Glutamine and the Regulation of O2 Diffusion in Legume Nodules.

H H Neo 1, D B Layzell 1
PMCID: PMC158138  PMID: 12223605

Abstract

The aim of the present study was to test the hypothesis that the N content or the composition of the phloem sap that supplies nodulated roots may play a role in the feedback regulation of nitrogenase activity by increasing nodule resistance to O2 diffusion. Treating shoots of lupin (Lupinus albus cv Manitoba) or soybean (Glycine max L. Merr. cv Maple Arrow) with 100 [mu]L L-1 NH3 caused a 1.3-fold (lupin) and 2.6-fold (soybean) increase in the total N content of phloem sap without altering its C content. The increase in phloem N was due primarily to a 4.8-fold (lupin) and 10.5-fold (soybean) increase in the concentration of glutamine N. In addition, there was a decline in both the apparent nitrogenase activity and total nitrogenase activity that began within 4 h and reached about 54% of its initial activity within 6 h of the start of the NH3 treatment. However, the potential nitrogenase activity values in the treated plants were not significantly different from those of the control plants. These results provide evidence that changes in the N composition of the phloem sap, particularly the glutamine content, may increase nodule resistance to O2 diffusion and, thereby, down-regulate nodule metabolism and nitrogenase activity by controlling the supply of O2 to the bacteria-infected cells.

Full Text

The Full Text of this article is available as a PDF (981.6 KB).

Selected References

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

  1. Atkins C. A., Sanford P. J., Storer P. J., Pate J. S. Inhibition of nodule functioning in cowpea by a xanthine oxidoreductase inhibitor, allopurinol. Plant Physiol. 1988 Dec;88(4):1229–1234. doi: 10.1104/pp.88.4.1229. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Denison R. F., Harter B. L. Nitrate Effects on Nodule Oxygen Permeability and Leghemoglobin (Nodule Oximetry and Computer Modeling). Plant Physiol. 1995 Apr;107(4):1355–1364. doi: 10.1104/pp.107.4.1355. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Escuredo P. R., Minchin F. R., Gogorcena Y., Iturbe-Ormaetxe I., Klucas R. V., Becana M. Involvement of Activated Oxygen in Nitrate-Induced Senescence of Pea Root Nodules. Plant Physiol. 1996 Apr;110(4):1187–1195. doi: 10.1104/pp.110.4.1187. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Farquhar G. D., Firth P. M., Wetselaar R., Weir B. On the Gaseous Exchange of Ammonia between Leaves and the Environment: Determination of the Ammonia Compensation Point. Plant Physiol. 1980 Oct;66(4):710–714. doi: 10.1104/pp.66.4.710. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Graham D., Smydzuk J. Use of anthrone in the quantitative determination of hexose phosphates. Anal Biochem. 1965 May;11(2):246–255. doi: 10.1016/0003-2697(65)90012-6. [DOI] [PubMed] [Google Scholar]
  6. Hunt S., King B. J., Canvin D. T., Layzell D. B. Steady and nonsteady state gas exchange characteristics of soybean nodules in relation to the oxygen diffusion barrier. Plant Physiol. 1987 May;84(1):164–172. doi: 10.1104/pp.84.1.164. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Layzell D. B., Hunt S., Palmer G. R. Mechanism of Nitrogenase Inhibition in Soybean Nodules : Pulse-Modulated Spectroscopy Indicates that Nitrogenase Activity Is Limited by O(2). Plant Physiol. 1990 Apr;92(4):1101–1107. doi: 10.1104/pp.92.4.1101. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Layzell D. B., Larue T. A. Modeling C and N transport to developing soybean fruits. Plant Physiol. 1982 Nov;70(5):1290–1298. doi: 10.1104/pp.70.5.1290. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Layzell D. B., Pate J. S., Atkins C. A., Canvin D. T. Partitioning of carbon and nitrogen and the nutrition of root and shoot apex in a nodulated legume. Plant Physiol. 1981 Jan;67(1):30–36. doi: 10.1104/pp.67.1.30. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Pate J. S., Atkins C. A., Layzell D. B., Shelp B. J. Effects of n(2) deficiency on transport and partitioning of C and N in a nodulated legume. Plant Physiol. 1984 Sep;76(1):59–64. doi: 10.1104/pp.76.1.59. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Vogels G. D., Van der Drift C. Differential analyses of glyoxylate derivatives. Anal Biochem. 1970 Jan;33(1):143–157. doi: 10.1016/0003-2697(70)90448-3. [DOI] [PubMed] [Google Scholar]
  12. Walsh K. B., Vessey J. K., Layzell D. B. Carbohydrate supply and n(2) fixation in soybean : the effect of varied daylength and stem girdling. Plant Physiol. 1987 Sep;85(1):137–144. doi: 10.1104/pp.85.1.137. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from Plant Physiology are provided here courtesy of Oxford University Press

RESOURCES