The Role of Dryas Drummondii in Vegetation Development Following Ice Recession at Glacier Bay, Alaska, with Special Reference to Its Nitrogen Fixation by Root Nodules

1967 ◽  
Vol 55 (3) ◽  
pp. 793 ◽  
Author(s):  
D. B. Lawrence ◽  
R. E. Schoenike ◽  
A. Quispel ◽  
G. Bond
Keyword(s):  
Nitrogen Fixation ◽  
Special Reference ◽  
Root Nodules ◽  
Vegetation Development ◽  
Glacier Bay

The role of oxygen diffusion from the shoots and nodule roots in nitrogen fixation by root nodules of Myrica gale

1978 ◽  
Vol 56 (11) ◽  
pp. 1365-1371 ◽  
Author(s):  
John Tjepkema
Keyword(s):  
Nitrogen Fixation ◽  
Oxygen Uptake ◽  
Aqueous Phase ◽  
Acetylene Reduction ◽  
Nitrogenase Activity ◽  
Root Nodules ◽  
Myrica Gale ◽  
Before And After ◽  
Whole Plants

Nitrogenase activity (acetylene reduction) and oxygen uptake by root nodules of Myrica gale L. were measured before and after removal of nodule roots. There was no significant effect of nodule root removal when respiration was measured in the gas phase (0.05–0.2 atm pO2 (1 atm = 101.325 kPa)) or acetylene reduction in a stirred aqueous phase at 0.2 atm pO2. However, when acetylene reduction was measured in 0.05 atm pO2 in an unstirred aqueous phase, there was a 66 to 76% reduction in activity. These results indicate that nodule roots are important for oxygen uptake when the nodules are present in an aqueous phase at low pO2, which is probably the normal environmental conditions for many of the nodules. Other measurements showed that diffusion of oxygen from the shoot to the root nodules is not important for nitrogen fixation. These measurements were done on whole plants with the shoots in air (0.20 atm pO2) and the roots in water at the desired pO2 value. With 0.0 atmpO2 in the root environment, the rate of acetylene reduction was only 4% of the rate at 0.2 atmpO2. Thus, only small amounts of oxygen are transported from the shoot to the nodules.

scholarly journals Mutation in the ntrR Gene, a Member of the vap Gene Family, Increases the Symbiotic Efficiency of Sinorhizobium meliloti

2001 ◽  
Vol 14 (7) ◽  
pp. 887-894 ◽  
Author(s):  
Boglárka Oláh ◽  
Erno Kiss ◽  
Zoltán Györgypál ◽  
Judit Borzi ◽  
Gyöngyi Cinege ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Pathogenic Bacteria ◽  
Sinorhizobium Meliloti ◽  
Root Nodules ◽  
Nifh Gene ◽  
Dry Weight ◽  
Nodule Occupancy ◽  
Gene Encoding ◽  
Symbiotic Efficiency ◽  
Host Interactions

In specific plant organs, namely the root nodules of alfalfa, fixed nitrogen (ammonia) produced by the symbiotic partner Sinorhizobium meliloti supports the growth of the host plant in nitrogen-depleted environment. Here, we report that a derivative of S. meliloti carrying a mutation in the chromosomal ntrR gene induced nodules with enhanced nitrogen fixation capacity, resulting in an increased dry weight and nitrogen content of alfalfa. The efficient nitrogen fixation is a result of the higher expression level of the nifH gene, encoding one of the subunits of the nitrogenase enzyme, and nifA, the transcriptional regulator of the nif operon. The ntrR gene, controlled negatively by its own product and positively by the symbiotic regulator syrM, is expressed in the same zone of nodules as the nif genes. As a result of the nitrogen-tolerant phenotype of the strain, the beneficial effect of the mutation on efficiency is not abolished in the presence of the exogenous nitrogen source. The ntrR mutant is highly competitive in nodule occupancy compared with the wild-type strain. Sequence analysis of the mutant region revealed a new cluster of genes, termed the “ntrPR operon,” which is highly homologous to a group of vap-related genes of various pathogenic bacteria that are presumably implicated in bacterium-host interactions. On the basis of its favorable properties, the strain is a good candidate for future agricultural utilization.

scholarly journals NITROGEN FIXATION BY EXCISED SOY BEAN ROOT NODULES

1954 ◽  
Vol 208 (1) ◽  
pp. 29-39
Author(s):  
M.H. Aprison ◽  
Wayne E. Magee ◽  
R.H. Burris
Keyword(s):  
Nitrogen Fixation ◽  
Root Nodules ◽  
Bean Root

scholarly journals Sugar enrichment provides evidence for a role of nitrogen fixation in coral bleaching

2017 ◽  
Vol 23 (9) ◽  
pp. 3838-3848 ◽  
Author(s):  
Claudia Pogoreutz ◽  
Nils Rädecker ◽  
Anny Cárdenas ◽  
Astrid Gärdes ◽  
Christian R. Voolstra ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Coral Bleaching

Anorexia Nervosa in a Black Zimbabwean

1984 ◽  
Vol 145 (3) ◽  
pp. 326-330 ◽  
Author(s):  
T. Buchan ◽  
L. D. Gregory
Keyword(s):  
Anorexia Nervosa ◽  
Special Reference ◽  
Diagnostic Criteria ◽  
Traditional Healer ◽  
Clinical Symptoms ◽  
The Social ◽  
Speculative Hypothesis ◽  
African Patients

SummaryIn spite of the comparative rarity of anorexia nervosa in African patients, the case of a young black Zimbabwean woman which fulfils Feighner's diagnostic criteria is presented. Special reference is made to several unusual features which include the social and psychological conflicts engendered by changes of culture, the clinical symptoms, and the role of a traditional healer in her recovery. A speculative hypothesis concerning aetiology is suggested.

Characterization of soluble, FSF-stabilized fibrin complexes with special reference to the role of fibrinogen

1974 ◽  
Vol 5 (1) ◽  
pp. 21-32 ◽  
Author(s):  
Bernt Ly ◽  
Peter Kierulf ◽  
Erling Jakobsen ◽  
Karl Gravem
Keyword(s):  
Special Reference ◽  
Stabilized Fibrin
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