scholarly journals Nitrogenase Activity in Alnus incana Root Nodules. Responses to O2 and Short-Term N2Deprivation

2000 ◽  
Vol 122 (2) ◽  
pp. 553-562 ◽  
Author(s):  
Per-Olof Lundquist
Keyword(s):  
Nitrogenase Activity ◽  
Root Nodules ◽  
Alnus Incana ◽  
Short Term

Effect of Oxygen Supply on Nitrogenase Activity of Nitrate- and Dark-Stressed Soybean (Glycine max (L.) Merr.) Plants

1987 ◽  
Vol 14 (6) ◽  
pp. 679 ◽  
Author(s):  
BJ Carroll ◽  
AP Hansen ◽  
DL Mcneil ◽  
PM Gresshoff
Keyword(s):  
Glycine Max ◽  
Nitrogenase Activity ◽  
Root Nodules ◽  
Short Term ◽  
Glycine Max L ◽  
Autonomous Activity ◽  
Effect Of Oxygen ◽  
Substrate Deprivation ◽  
Dark Stress ◽  
Oxygen Concentrations

Nitrate and dark stress were used to induce decline in nitrogenase activity of root nodules of soybeans (Glycine max (L.) Merr. cv. Bragg). Response to this treatment and to various oxygen concentrations was assessed by short-term acetylene reduction assays. Decreases in oxygen partial pressure reduced nitrogenase activity substantially in unstressed soybean nodules and even further in nodules of nitrate- or dark-stressed plants. Increasing oxygen concentrations from 21 to 60% severely restricted nitrogenase activity in control plants, but stimulated activity in soybeans exposed to 10 mol m-3 nitrate or darkness for 2 days. Less stressed plants (treated with 7.5 mol m-3 nitrate) were stimulated less by high oxygen tension. Soybeans deprived of light for 4 days were symbiotically inactive and did not respond to raised O2 concentrations. Bacteroids isolated from these plants had lost their autonomous activity but recovered in the presence of succinate, indicating substrate deprivation. The data presented suggest that suboptimal oxygen concentration near the bacteroids is an important factor limiting nitrogenase activity in nitrate-or dark-stressed soybeans.

Nitrogenase activity in response to restricted shoot growth in Alnus incana

1983 ◽  
Vol 61 (11) ◽  
pp. 2949-2955 ◽  
Author(s):  
Kerstin Huss-Danell ◽  
Anita Sellstedt
Keyword(s):  
Root Biomass ◽  
Shoot Growth ◽  
Nitrogenase Activity ◽  
Root Nodules ◽  
Alnus Incana ◽  
Nitrogen Fixing ◽  
Combined Nitrogen ◽  
Carbon Compounds ◽  
Source Sink ◽  
Nitrogen Percentage

In the Alnus–Frankia symbiosis the nitrogen-fixing root nodules are one of the sinks for carbon compounds newly formed in photosynthesis and exported from the leaves (source). The competition for assimilates between shoot tips and root nodules was studied by reducing shoot growth. Cloned plants of Alnus incana (L.) Moench were grown without combined nitrogen in a growth chamber. Shoot growth was inhibited by excision of all buds or by induced dormancy. The experiments showed an increased root biomass in the treated plants, indicating a changed source–sink balance. The treatments never caused an increased nitrogenase activity (C2H2-dependent C2H4 production); rather it was decreased. The nitrogenase activity was always correlated with leaf areas. It was also correlated with growth, which is shown by the similar nitrogen percentage in intact and treated plants.

Adaptation of nitrogenase to varying oxygen tension and the role of the vesicle in root nodules of Alnus incana ssp. rugosa

1988 ◽  
Vol 66 (9) ◽  
pp. 1772-1779 ◽  
Author(s):  
Warwick B. Silvester ◽  
Janet K. Silvester ◽  
John G. Torrey
Keyword(s):  
Flow System ◽  
Nitrogenase Activity ◽  
Root Nodules ◽  
Major Change ◽  
Dark Field ◽  
Alnus Incana ◽  
Major Barrier ◽  
Dark Field Microscopy ◽  
Nodule Morphology

Growth of Alnus incana ssp. rugosa plants with root systems at Po2 levels of 5, 21, and 40 kPa showed no significant differences among treatments over a 6-week period. Nitrogenase activity of attached nodulated foot systems run in an opencuvette continuous-flow system generally was responsive to Po2 over a broad range around the optimum. Plants expressed acetylene-induced and oxygen-induced transient declines in nitrogenase activity, from which they spontaneously recovered. Nitrogenase activity was seldom stable at any one Po2 during assay with apparent adaptation to both above- and below-ambient Po2 Nodule morphology showed quantitative decreases in aeration pathways as ambient Po2 was increased, with air spaces in the cortex and infected tissue being significantly affected. The major change in response to Po2 was the change in vesicle structure. Vesicles from nodules at low Po2 showed a vanishingly thin vesicle envelope under dark-field microscopy, while at high Po2 vesicles appeared very bright and apparently thickened. The results suggest that the major barrier to O2 diffusion in Alnus nodules is the vesicle envelope of the bacterium.

scholarly journals Paraburkholderia phymatum Homocitrate Synthase NifV Plays a Key Role for Nitrogenase Activity during Symbiosis with Papilionoids and in Free-Living Growth Conditions

Cells ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 952
Author(s):  
Paula Bellés-Sancho ◽  
Martina Lardi ◽  
Yilei Liu ◽  
Sebastian Hug ◽  
Marta Adriana Pinto-Carbó ◽  
...  
Keyword(s):  
Nitrogenase Activity ◽  
Root Nodules ◽  
Growth Conditions ◽  
Lysine Biosynthesis ◽  
Metabolome Analysis ◽  
Plant Host ◽  
Free Living ◽  
Bacterial Enzyme ◽  
Homocitrate Synthase ◽  
Iron Molybdenum Cofactor

Homocitrate is an essential component of the iron-molybdenum cofactor of nitrogenase, the bacterial enzyme that catalyzes the reduction of dinitrogen (N2) to ammonia. In nitrogen-fixing and nodulating alpha-rhizobia, homocitrate is usually provided to bacteroids in root nodules by their plant host. In contrast, non-nodulating free-living diazotrophs encode the homocitrate synthase (NifV) and reduce N2 in nitrogen-limiting free-living conditions. Paraburkholderia phymatum STM815 is a beta-rhizobial strain, which can enter symbiosis with a broad range of legumes, including papilionoids and mimosoids. In contrast to most alpha-rhizobia, which lack nifV, P. phymatum harbors a copy of nifV on its symbiotic plasmid. We show here that P. phymatum nifV is essential for nitrogenase activity both in root nodules of papilionoid plants and in free-living growth conditions. Notably, nifV was dispensable in nodules of Mimosa pudica despite the fact that the gene was highly expressed during symbiosis with all tested papilionoid and mimosoid plants. A metabolome analysis of papilionoid and mimosoid root nodules infected with the P. phymatum wild-type strain revealed that among the approximately 400 measured metabolites, homocitrate and other metabolites involved in lysine biosynthesis and degradation have accumulated in all plant nodules compared to uninfected roots, suggesting an important role of these metabolites during symbiosis.

Carbon Costs of Nitrogenase Activity in Legume Root Nodules determined using Acetylene and Oxygen

1983 ◽  
Vol 34 (8) ◽  
pp. 951-963 ◽  
Author(s):  
J. F. WITTY ◽  
F. R. MINCHIN ◽  
J. E. SHEEHY
Keyword(s):  
Nitrogenase Activity ◽  
Root Nodules ◽  
Carbon Costs

Seasonal pattern of energy use, respiration, and nitrogenase activity in root nodules of Myrica gale

1983 ◽  
Vol 61 (11) ◽  
pp. 2937-2942 ◽  
Author(s):  
Christa R. Schwintzer ◽  
John D. Tjepkema
Keyword(s):  
Energy Cost ◽  
Energy Use ◽  
Nitrogenase Activity ◽  
Root Nodules ◽  
Seasonal Pattern ◽  
Uptake Ratio ◽  
Experimental Conditions ◽  
Myrica Gale ◽  
Net Production ◽  
N Requirement

Annual CO2 evolution, H2 evolution, and C2H2 reduction were measured in root nodules from a vigorous Myrica gale stand in a Massachusetts peatland at 3-week intervals in 1980. Nodule activity was approximately the same under the experimental conditions (excised nodules reducing C2H2) as in nature (attached nodules reducing N2) and the CO2 evolution to O2 uptake ratio averaged 1.07. Nitrogenase activity was first detectable in late May, reached its maximum [Formula: see text] in mid-July, and disappeared in late October. The seasonal pattern of CO2 evolution was similar except that it continued at low rates when nitrogenase activity was absent. Hydrogen evolution was barely detectable. The energy cost of nitrogen fixation, expressed as the molar CO2:C2H4 ratio, was relatively low [Formula: see text] throughout the period of substantial nitrogenase activity and had a mean annual value of 4.9. Annual N2 fixation was estimated to be 2.8 g N m−2year−1, contributing about 33% of the annual N requirement measured in 1979. Annual C use by nodules was about 21.0 g C m−2 year−1. If this C were available for additional net production, it would increase it by about 5.5%.

Dinitrogen fixation and nodulation by Frankia in Alnus incana as affected by inorganic nitrogen in pot experiments with peat

1983 ◽  
Vol 61 (11) ◽  
pp. 2956-2963 ◽  
Author(s):  
U. Granhall ◽  
T. Ericsson ◽  
M. Clarholm
Keyword(s):  
Acetylene Reduction ◽  
Nitrogenase Activity ◽  
Inorganic Nitrogen ◽  
Experimental Period ◽  
Alnus Incana ◽  
Nitrogen Application ◽  
Noticeable Effect ◽  
Essential Nutrients ◽  
Pot Experiments ◽  
Ph Level

The effects of single large or repeated, exponentially increasing applications of nutrients, with or without inorganic nitrogen and at two pH levels, on the growth, nodulation, acetylene reduction, and nutrient uptake in Alnus incana (L.) Moench were investigated in pot experiments with peat under controlled laboratory conditions. The repeated application of inorganic nitrogen did not suppress nitrogenase activity until the last 2 weeks, whereas an initial, large, nitrogen application effectively inhibited nodulation and activity throughout the 40-day experimental period. The mode of nitrogen application was thus found to be more important than the total amounts applied. Shoot length, leaf area, shoot–root relations, dry-matter production, and nitrogen contents of plants were determined at the end of the experiment, as well as the effect of Frankia inoculations. Nitrogenase activity was determined three times, at 0, 3, and 5 weeks. N2 fixation (balance/acetylene reduction) was found to be maximal, 55% of total nitrogen uptake, in minus-N pots with single applications of essential nutrients. The fastest growth was, however, noted in pots with single applications of all nutrients, including N. Among the latter, pots inoculated with Frankia showed the best growth, in spite of low nitrogenase activity. The only noticeable effect of a raised pH level was a reduced endophyte activity in minus-N pots with single applications of essential nutrients, due to increased N mineralization in the peat.

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