Abstract
Parasponia is the first non-legume genus proven to form nitrogen-fixing root nodules induced by rhizobia. Infiltration with India ink demonstrated that intercellular air spaces are lacking in the inner layers of the nodule cortex. Oxygen must diffuse through these layers to reach the cells containing the rhizobia, and it was calculated that most of the gradient in O2 partial pressure between the atmosphere and rhizobia occurs at the inner cortex. This was confirmed by O2 microelectrode measurements which showed that the O2 partial pressure was much lower in the zone of infected cells than in the cortex. Measurements of nitrogenase activity and O2 uptake as a function of temperature and partial pressure of O2 were consistent with diffusion limitation of O2 uptake by the inner cortex. In spite of the presumed absence of leghemoglobin in nodules of Parasponia rigida Merr. and Perry, energy usage for nitrogen fixation was similar to that in legume nodules. The results demonstrate that O2 regulation in legume and Parasponia nodules is very similar and differs from O2 regulation in actionorhizal nodules.
Full text
PDF
Images in this article
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Coventry D. R., Trinick M. J., Appleby C. A. A search for a leghaemoglobin-like compound in root nodules of Trema cannabina Lour. Biochim Biophys Acta. 1976 Jan 20;420(1):105–111. doi: 10.1016/0005-2795(76)90349-4. [DOI] [PubMed] [Google Scholar]
- Sinclair T. R., Goudriaan J. Physical and morphological constraints on transport in nodules. Plant Physiol. 1981 Jan;67(1):143–145. doi: 10.1104/pp.67.1.143. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Tjepkema J. D., Winship L. J. Energy requirement for nitrogen fixation in actinorhizal and legume root nodules. Science. 1980 Jul 11;209(4453):279–281. doi: 10.1126/science.7384801. [DOI] [PubMed] [Google Scholar]
- Trinick M. J. Structure of nitrogen-fixing nodules formed by Rhizobium on roots of Parasponia andersonii Planch. Can J Microbiol. 1979 May;25(5):565–578. doi: 10.1139/m79-082. [DOI] [PubMed] [Google Scholar]
- Wittenberg J. B. Myoglobin-facilitated oxygen diffusion: role of myoglobin in oxygen entry into muscle. Physiol Rev. 1970 Oct;50(4):559–636. doi: 10.1152/physrev.1970.50.4.559. [DOI] [PubMed] [Google Scholar]
- Zobel R. W., Del Tredici P., Torrey J. G. Method for growing plants aeroponically. Plant Physiol. 1976 Mar;57(3):344–346. doi: 10.1104/pp.57.3.344. [DOI] [PMC free article] [PubMed] [Google Scholar]