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  • 1
    Electronic Resource
    Electronic Resource
    Nitrogenase activity and root nodule metabolism in response to O2 and short-term N2 deprivation in dark-treated Frankia-Alnus incana plants (2003)
    Oxford, UK : Munksgaard International Publishers
    Physiologia plantarum 119 (2003), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Inhibition of nitrogenase (EC 1.18.6.1) activity by O2 has been suggested to be an early response to disturbance in carbon supply to root nodules in the Frankia-Alnus incana symbiosis. Intact nodulated root systems of plants kept in prolonged darkness of 22 h were used to test responses to O2 and short-term N2 deprivation (1 h in Ar:O2). By using a Frankia lacking uptake hydrogenase it was possible to follow nitrogenase activity over time as H2 evolution in a gas exchange system. Respiration was simultaneously recorded as CO2 evolution. Dark-treated plants had lower initial nitrogenase activity in N2:O2 (68% of controls), which declined further during a 1-h period in the assay system in N2:O2 at 21 and 17% O2, but not at 13% O2. When dark-treated plants were deprived of N2 at 21 and 17% O2 nitrogenase activity declined rapidly to 61 and 74%, respectively, after 20 min, compared with control plants continuously kept in their normal light regime. In contrast, there was no decline in dark-treated plants at 13% O2, and only a smaller and temporary decline in control plants at 21% O2. When dark-treated plants were kept at 21% O2 during 45 min prior to N2 deprivation at 17% O2 the decline was abolished. This supports the idea that the decline in nitrogenase activity observed in N2:O2 at 21% O2 and during N2 deprivation was caused by O2, which affected a sensitive nodule fraction. Nodule contents of the amino acids Gln and Cit decreased during N2 deprivation, suggesting decreased assimilation of NH4+. Contents of ATP and ADP in nodules were not affected by short-term N2 deprivation. ATP/ADP ratios were about 5 indicating a highly aerobic metabolism in the root nodule. We conclude that nitrogenase activity of Alnus plants exposed to prolonged darkness becomes more sensitive to inactivation by O2. It seemed that dark-treated plants could not adjust their nodule metabolism at higher perceived pO2 and during cessation of NH4+ production.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2003.00177.x
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  • 2
    Electronic Resource
    Electronic Resource
    Immunological studies of glutamine synthetase in Frankia-Alnus incana symbioses (1992)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 91 (1992), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract We have investigated the presence and form of glutamine synthetase (GS) in Frankia vesicle cluster preparations of two actively nitrogen-fixing Frankia-Alnus incana root-nodule symbioses and in cultured Frankia sp. strain CpI1 (HFP070101). The symbioses contained Frankia CpI1 or the local source of Frankia. We used Western-blot analysis with antisera raised against three types of GS. In symbiotic Frankia GS protein was not detected at a significant level when either antisera against Rhodospirillum rubrum GS or antisera against Rhizobium meliloti GSII were used. In cultured Frankia CpI1 GSI was detected both when grown with NH4+ or N2 as nitrogen source, and GSII was detected when grown on N2. Antiserum raised against the nodule-specific GSn1 of Phaseolus vulgaris crossreacted with a 43-kDa polypeptide corresponding to plant GS in root-nodule extracts from Alnus, and with a 41-kDa polypeptide corresponding to GSII in cultured Frankia CpI1 grown on N2. We conclude that both GSI and GSII are repressed in symbiotic Frankia and that NH4+ produced through nitrogen fixation is assimilated by the plant in Frankia-Alnus incana symbioses. It thus appears that vesicle formation, synthesis of nitrogenase and synthesis of GS are separately regulated in symbiotic Frankia and that the plant has to supply symbiotic Frankia with organic nitrogen in some form in addition to the carbon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1992.tb05199.x
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  • 3
    Electronic Resource
    Electronic Resource
    Response of nitrogenase to altered carbon supply in a Frankia-Alnus incana symbiosis (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: To study the effect of altered carbon supply on nitrogenase (EC 1.7.99.2), plants of Alnus incana (L.) Moench in symbiosis with the local source of Frankia were exposed to darkness for 2 days, and then returned to normal light/dark conditions. During the dark period nitrogenase activity in vivo (intact plants) and in vitro (Frankia cells supplied with ATP and reductant), measured as acetylene reduction activity, was almost completely lost. Western blots for both the Fe-protein (dinitrogenase reductase) and the MoFe-protein (dinitrogenase) showed that, in particular, the amount of MoFe-protein was strongly reduced during darkness. Protein stained sodium dodecyl sulphate-polyacrylamide gels of Frankia protein showed that the nitrogenase proteins were the only abundant proteins that clearly decreased during darkness. During recovery, studied for 4 days, nitrogenase activity in vivo recovered to the level before dark treatment but was still only half of control activity, Nitrogenase activity in vitro and the amount of MoFe-protein, both expressed per Frankia protein, recovered and reached similar values in previously dark treated plants and in control plants. The rate of recovery was similar to the increase in activity of control plants, suggesting growth of Frankia in addition to synthesis of nitrogenase proteins during the recovery after carbon starvation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1991.tb00102.x
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  • 4
    Electronic Resource
    Electronic Resource
    Respiratory capacity, nitrogenase activity and structural changes ofFrankia, in symbiosis withAlnus incana, in response to prolonged darkness (1990)
    Springer
    Planta 182 (1990), S. 617-625 
    Details
    ISSN: 1432-2048
    Keywords: Alnus ; Darkness and nitrogenase activity ; Frankia ; Nitrogenase ; Respiration ; Root nodule structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plants ofAlnus incana (L.) Moench in symbiosis with a local source ofFrankia were exposed to prolonged darkness under controlled climate conditions.Frankia vesicle clusters were prepared from the root nodules, and the condition ofFrankia was measured as respiratory capacity by supplying the preparation with saturating amounts of four different substrates. During darkness, nitrogenase (EC 1.7.99.2) activity decreased in intact plants and in the vesicle-cluster preparations. The respiratory capacity ofFrankia also decreased. After 4 d in darkness most respiration was lost, though all nitrogenase activity was already lost after 3 d. When the dark treatment was ended after 2 d and normal light/dark conditions restored, nitrogenase activity immediately started to recover. The respiratory capacity continued to decrease and no recovery was observed until the third day after the end of the dark treatment. Whole-plant nitrogenase activity slowly increased at a rate similar to the rate of increase observed in untreated plants. Transmission electron micrographs of the root nodules showed that the cytoplasm of infected host cells and the cells ofFrankia were structurally degraded in response to dark treatment, while young vesicles were frequent during recovery. Growth and differentiation ofFrankia cells were apparently important for recovery of the enzyme activities studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02341040
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  • 5
    Electronic Resource
    Electronic Resource
    Growth and acetylene reduction activity by intact plants ofAlnus incana under field conditions (1989)
    Springer
    Plant and soil 118 (1989), S. 61-73 
    Details
    ISSN: 1573-5036
    Keywords: Alnus incana ; field ; Frankia ; growth ; intact plants ; nitrogenase activity ; nitrogen fixation ; photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The nitrogen-fixing grey alder,Alnus incana (L.) Moench, has a potential use in forest soil restoration and as part of energy forestry plantations. As a first step to estimate nitrogen fixation byA. incana under field conditions we performed studies on nitrogenase activity and its possible relation to abiotic factors and growth of the alders. Nitrogenase activity was measured as acetylene reduction activity (ARA) on eleven 1-year-old seedlings ofA. incana inoculated with a local source ofFrankia and planted in an experimental plot located in Umeå, northern Sweden. Each alder was planted into an open-ended cylinder which was closed with a gas tight lid around the stem base to serve as cuvette during ARA measurements. Propane served as tracer gas. ARA was measured in the middle of the day at 15 occasions during 26 June to 29 September 1987. Growth was recorded as leaf area and top shoot length at each ARA measurement until the end of August. Weather conditions were recorded for the whole growing season. Maximal ARA was recorded in late July or early August and ranged from 1.86 to 106μmol C2H4plant−1h−1. Final leaf area ranged from 0.022 to 0.124 m2. A relationship between ARA and the number of hours of sunshine during the same day was observed. ARA in relation to soil temperature increased during the study period, except for the last measurements. ARA in relation to leaf area was initially high but decreased later on. It is suggested that as leaves got older their contribution to photosynthesis per unit leaf area decreased and their potential to deliver nitrogen for retranslocation within plant increased. Both of these events would cause reduced ARA per unit leaf area. The data on ARA, growth, and abiotic factors taken together supported the view that sunshine and weather conditions affected photosynthesis and thereby delivery of assimilates to the nodules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02232791
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