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  • 1
    Electronic Resource
    Electronic Resource
    Gas Exchange of Legume Nodules and the Regulation of Nitrogenase Activity (1993)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Plant Physiology and Plant Molecular Biology 44 (1993), S. 483-511 
    Details
    ISSN: 1040-2519
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.pp.44.060193.002411
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  • 2
    Electronic Resource
    Electronic Resource
    Hydrogen fertilization of soils – is this a benefit of legumes in rotation? (2003)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 26 (2003), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Hydrogen gas (H2) is an obligate byproduct of the N2-fixing enzyme, nitrogenase, claiming about 5–6% of the crops’ net photosynthesis but most, if not all of the H2 lost from nodules is oxidized by the soil surrounding the root system of the plant. When soils not recently used to support the growth of legumes were exposed to H2 gas at a rate and duration similar to that of soil adjacent to legume nodules, the fertility of the soil was enhanced in comparison with soil treated with air. Under growth-chamber and field conditions, H2-treated soils improved the growth performance of spring wheat, canola, barley and soybean (non-symbiotic) when compared with untreated soils or with soils pretreated with air. The dry weights of 4- to 7-week-old plants were 15–48% greater in the H2-treated soil, and in barley and spring wheat, tiller number of 7-week-old plants were 36 and 48% greater in the H2-treated soils. These findings may contribute to an explanation for the persistence of H2 evolving associations in agricultural legume symbioses selected for high yields (Uratsu et al., Crop Science 22, 600–602, 1982) and suggest that it may be possible to isolate, identify and culture the micro-organisms that are responsible for at least some of the benefits of legumes in crop rotation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2003.01103.x
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  • 3
    Electronic Resource
    Electronic Resource
    Diffusion and reaction of oxygen in the central tissue of ureide-producing legume nodules (1999)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 22 (1999), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Previous simulation models for the diffusion and reaction of oxygen in legume nodules were based on infected cells and neglected adjacent uninfected cells. This study uses a three-dimensional model of the central zone of legume nodules made up of the two cell types represented by a geometrically defined, space-filling, binary combination of polyhedra, each with bevelled edges to allow for a network of intercellular gas spaces. The model predicted a distinctively compartmentalized distribution of [O2] between uninfected and infected cells; with high O2 concentrations for an uninfected cell being consistent with, and necessary for, efficient operation of uricase and ureide synthesis and low O2 concentrations across most of the infected cell providing a suitable environment for N2-fixation. Compartmentalization of O2 also predicted significant O2 fluxes between cell types, compromising maintenance of low [O2] in infected cells, as well as high [O2] in uninfected cells. The results predict that there might be significant resistance to O2 diffusion across the cell : cell interface due to the plasmalemma and cell walls.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1999.00498.x
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  • 4
    Electronic Resource
    Electronic Resource
    The use of positron emission tomography for studies of long-distance transport in plants: uptake and transport of 18F (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 11 (1988), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Positron emission tomography (PET) has been utilized to obtain dynamic images of long distance nutrient translocation in plants. Positron emitting 18F, produced by a Van de Graaff accelerator using the reaction 18O(p,n)18F, was fed in solution to excised stems of Glycine max positioned vertically in a large-aperture PET detector system. Images of tracer activity were recorded with a time resolution of 0.5 min and a spatial resolution of 4 mm. Maximum tracer activities at stem sites were obtained within 3 min of the pulse feed. A model is presented enabling evaluation of regional values for tracer flow, tracer binding, flow speed and flow volume. Analysis of data for one stem position yielded a flow volume of 2.1mm3 min−1 and a flow speed of 36cm min−1. Comparison with the distribution of 14C-inulin, which was simultaneously fed to the cut stems, indicates the 18F is suitable for use as an apoplastic tracer; 92% of the tracer activity accumulated in the leaves. The fraction of 18F that remained bound was most concentrated at stem nodal regions, an observation consistent with the existence of transfer cells at these sites. Advantages and limitations of PET applied to plant physiological investigations are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1988.tb01911.x
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  • 5
    Electronic Resource
    Electronic Resource
    Vascular transport and soybean nodule function: II. A role for phloem supply in product export (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 12 (1989), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The ureide content of soybean (Glycine max (L.) Merr.) nodules was unaffected by variations in the transpirational rate, while whole plant manipulations designed to decrease phloem supply to nodules resulted in lower rates of nitrogenase activity and an increase in the ureide content of the nodules. The rate of ureide export from the nodule was estimated from the exponential rate of decrease in the pool size of ureides in nodules, following exposure to an N2-free atmosphere (Ar:O2). Export was greatly reduced under treatments which reduced phloem supply to the nodule. A water budget for nodules suggested that the delivery of water to the nodule via mass flow in the phloem was comparable to that required for export of ureides from the nodule in the xylem from the nodule. Therefore, we suggest that xylem export from nodules is related to the phloem supply to the nodule rather than to the transpirational flux in the parent root. This suggestion is related to the reported decreases in nodule permeability to gases under conditions of phloem deprivation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1989.tb01631.x
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  • 6
    Electronic Resource
    Electronic Resource
    Does oxygen limit nitrogenase activity in soybean exposed to elevated CO2? (2004)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 27 (2004), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Soybean (Glycine max L. Merr) plants grown under control (360 µmol mol−1) or elevated CO2 concentration (800 µmol mol−1) from 33 to 42 d after sowing were assayed for various components of in vivo nitrogenase activity to test the hypothesis that increasing carbohydrate supply to nodules would increase the potential (i.e. O2 saturated) nitrogenase activity and impose a more severe O2 limitation on both nodule metabolism and total nitrogenase activity. Within 51 h of elevated CO2 treatment, significant increases relative to control plants were seen in total nitrogenase activity expressed per plant. After 6 d of elevated CO2, the total nitrogenase activity per plant was 18% higher than that in control. This was attributed to an initial increase in nodule size, and a subsequent increase in nodule number following plant exposure to elevated CO2. However, after 9 d of elevated CO2, the potential and total nitrogenase activities per gram nodule dry weight were lower, not higher than corresponding values in plants in the control treatment. These results did not support the hypothesis. It was concluded that the metabolic capacity of the control nodules were not limited by carbohydrate supply, at least at the assay temperatures employed here.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.2004.01229.x
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  • 7
    Electronic Resource
    Electronic Resource
    The effect of bacterial strain and temperature changes on the nitrogenase activity of Lotus pedunculatus root nodules (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 62 (1984), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: After 40 days of growth at 25°C, Lotus pedunculatus cav., cv. Maku plants infected with Rhizobium loti strain NZP2037 displayed similar relative growth rates but had twice the nodule mass and only one third the whole plant dry weight of plants infected with Bradyrhizobium sp. (Lotus) strain CC814s. In the NZP2037 symbiosis, the rate of CO2 evolution (per g dry weight of nodulated root) was 1.6 times as high as that in the CC814s symbiosis while the rate of C2H2 reduction (per g dry weight of nodule) was only 48% of that in the CC814s symbiosis. Studies of the effect of short term temperature changes on the gas exchange characteristics (CO2 and H2 evolution, C2H2 reduction) of these symbioses revealed wide differences in the optima for C2H2 reduction. Nodules infected with NZP2037 displayed maximal C2H2 reduction rates [157 μmol (g dry weight nodule)−1 h−1] at 12°C, whereas nodules infected with CC814s were optimal at 30°C [208 μmol (g dry weight nodule)−1 h−1]. These short term studies suggested that differences in temperature optima for N2 may have partially accounted for the poorer effectivity, at 25°C, of strain NZP2037 when compared with strain CC-814s.The relative efficiency [RE = 1 – (H2 evolution/C2H2 reduction)] of N2 fixation varied widely with temperature in the two symbioses, but there was a general trend toward higher RE with lower temperatures. The ratio of CO2 evolution: C2H2 reduction (mol/mol) in nodulated roots infected with CC814s was constant (ca 10 CO2/C2H2) between 5°C and 30°C, whereas in plants infected with NZP2037 it reached a minimal value of 3.3 CO2/C2H2 at 10°C and was 19 CO2/C2H2 at the growing temperature (25°C).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1984.tb04593.x
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  • 8
    Electronic Resource
    Electronic Resource
    The effect of excision on O2 diffusion and metabolism in soybean nodules (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 83 (1991), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Nitrogen-fixing nodules of soybean [Glycine max (L.) Merr. cv. Maple Arrow inoculated with Bradyrhizobium japonicum USDA 16] were studied before and after excision from the root to determine the role the O2 regulation plays in the inhibition of nodule activity and the potential for using excised nodules nodules in studies of nodule metabolism. Relative nitrogenase (EC 1.7.99.2) activity (H2 evolution in N2:O2) and nodule respiration (CO2 evolution) were monitored first in intact nodulated roots and then in freshly excised nodules of the same plant to determine the time course of the decline in nodule metabolism. Folowing excision, nitrogenase activity and respiration declined rapidly in the first minute and then more gradually. After 40 min the rate of H2 evolution was only 14–28% of that in the intact plant. In some nodules activity declined steadily, and in others there was a partial recovery in activity ca 10 min after detachment. Infected cell O2 concentration (Oi), measured by a spectro-photometric technique, also declined after nodule detachment with a time course similar to the declines in nitrogenase activity and respiration. Following excision, Oi levels declined rapidly from ca 21 nM in attached nodules to 8–12 nM at 4–10 min after excision and then more gradually to 2–3 nM O2 at 30–40 min after excision. These results show that the nodules' permeability to gas diffusion continued to be regulated for up to 40 min after detachement. At 40 min after detachment, when excised nodules displayed steady-state rates of gas exchange, linear increases in pO2 from 20 to 100% at 4% min−1 resulted in recoveries of H2 and CO2 evolution, indicating that Oi limited nitrogenase activity durig this period, and that energy reserves were greatly in excess of the O2 available for respiration. When detached nodules were equilibrated for 12 h at 20, 30 and 50% O2, Oi values measured at supra-ambient pO2 were greater than those at 20% O2 and were linked with a more rapid decline in nitrogenase activity. Also, increases in external pO2 (Oc) failed to stimulate nodule metabolism, suggesting that the nodules' energy reserves were no longer greatly in excess of their respiratory demands. It was concluded that soybean nodules could provide useful material for steady-state studies of nodule metabolism between 40 and 240 min after detachment, but to attain metabolic rates equivalent to in vivo rates the nodules must be exposed to above-ambient pO2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1991.tb01283.x
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  • 9
    Electronic Resource
    Electronic Resource
    Characterization ofR. fredii QB1130, a strain effective on commercial soybean cultivars (1987)
    Springer
    Plant and soil 99 (1987), S. 441-446 
    Details
    ISSN: 1573-5036
    Keywords: Bradyrhizobium japonicum ; C3A fast-growing rhizobia ; Glycine max ; Rhizobium fredii ; B1130 ; USDA191
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Two rhizobial strains (QB1130 and C3A) from northeast China were identified asRhizobium fredii on the basis of growth rate, media acidification and growth on a wide range of carbon substrates. The strains were shown to be distinct from USDA 191 on the basis of plasmid number and size. Bothnif and commonnod genes were located on the 295 kb plasmid of strains QB1130 and USDA 191, while onlynif genes were identified on this plasmid in C3A. When used to inoculate four commercial soybean (Glycine max) cultivars, one of the strains (C3A) was found to be ineffective, while the other (QB1130) was at least as effective as USDA 191, a strain ofR. fredii reported to be widely effective on North American cultivars of soybean. Further, QB1130 was capable of more effective nodulation of cowpea or the uncultivated soybean line, Peking, than either USDA 191 or the slow-growingBradyrhizobium japonicum USDA 16. Strain QB1130 should be useful for studies directed at improving symbiotic performance in soybean, or for studies of the comparative physiology and genetics of FG and SG strains on a single host.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02370889
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