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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 51 (1979), S. 437-440 
    ISSN: 1573-5036
    Keywords: Acetylene reduction ; Anthocyanin ; Haemin ; Lupin ; N fixation ; Nodulation ; Nodules ; Rhizobium ; Sand
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A Rhizobium specific anthocyanin-like pigment has been isolated from nodules ofLupinus arboreus. The pigment is located in the nodule cortex. Comparison of normal nodules and nodules containing this ‘red’ pigment showed that the latter had a lower proportion of bacteroid tissue and a lower nitrogenase activity.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5036
    Keywords: diffusion ; diffusion-resistance ; Frankia ; oxygen ; periderm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract When excised root nodules ofCoriaria arborea are assayed for nitrogenase activity at various pO2 they show a broad optimum between 20 and 40 kPa O2, with some evidence for adaptation. Continuous flow assays of nodulated root systems of intact plants indicate that Coriaria shows an acetylene induced decline in nitrogenase activity. When root systems were subject to step changes in pO2 nitrogenase activity responded with a steep decline followed by a slower rise in activity both at lower and higher than ambient pO2. Thus Coriaria nodules are able to adapt rapidly to oxygen levels well above and well below ambient. Measurement of nodule diffusion resistance showed that the adaptation is accompanied by rapid increase in resistance at above ambient pO2 and decrease in resistance at below ambient pO2. Plants grown with root systems at pO2 from 5–40 kPa O2 did not differ in growth or nodulation. The anatomy of Coriaria nodules shows they have a dense periderm which encircles the nodule and also closely invests the infected zone. The periderm is both thicker and more heavily suberised in nodules grown at high pO2 than at low pO2. Vacuum infiltration of India ink indicates that oxygen diffusion is entirely through the lenticel and via a small gap adjacent to the stele.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 35 (1971), S. 647-650 
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Coprosma robusta Raoul plants grown in plus- and minus-nitrogen sand culture showed no significant response to removal of stipules. Acetylene reduction assays for nitrogenase on leaves and stipules gave negative results for six Coprosma species. Two unwashed root samples showed slight acetylene reduction and this was ascribed to casual aerobic rhizosphere organisms.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 35 (1971), S. 647-650 
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Coprosma robusta Raoul plants grown in plus- and minus-nitrogen sand culture showed no significant response to removal of stipules. Acetylene reduction assays for nitrogenase on leaves and stipules gave negative results for six Coprosma species. Two unwashed root samples showed slight acetylene reduction and this was ascribed to casual aerobic rhizosphere organisms.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 224 (1969), S. 1231-1231 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Blue-green algae enter into symbiosis with a variety of plant groups7,8 and for some of these, the phycobiont has been shown to fix nitrogen making it available to the host. It has been assumed8 that the same holds true for Gunnera-Nostoc, although Scott9 speculates that any contribution of fixed ...
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  • 6
    ISSN: 1432-072X
    Keywords: Key words: Hydrogen – Hydrogenase – Nitrogenase –Gunnera– Nostoc – Symbiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Nitrogenase activity in the Gunnera Nostoc symbiosis is shown to respond dramatically to the addition of glucose. H2 can replace glucose in stimulating nitrogenase activity, but there is no H2 stimulation in the presence of excess glucose. Net hydrogen evolution is strongly stimulated by addition of glucose. We postulate that carbohydrate supply and uptake hydrogenase can moderate the apparent activity of nitrogenase by supplying reductant and/or ATP. The recycling of a large proportion of the electron flux in nitrogenase through uptake hydrogenase maintains a high level of potential nitrogenase ready to take advantage of an influx of carbohydrate.
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  • 7
    ISSN: 1432-072X
    Keywords: Nitrogenase ; Anabaena ; Pyruvate: Ferredoxin Oxidoreductase ; Blue-Green Alga
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Exogenous pyruvate added to cultures of the bluegreen alga, Anabaena cylindrica stimulated nitrogenase activity (measured by acetylene reduction) only in the dark under low pO2 (0.05 atmospheres). Under aerobic conditions or in the light, stimulation was absent and replaced by an inhibition of activity above 5 mM added pyruvate. The curve of nitrogenase activity versus oxygen concentration had a similar maximal value of ethylene production with or without added pyruvate, but in the presence of pyruvate this maximum occurred at 0.05 atmospheres O2, whilst in the absence of pyruvate the maximum occurred at 0.10 atmospheres O2. Malate, citrate, α-ketoglutarate, glucose and fructose were tested also, but none gave a similar effect to pyruvate. Addition of 14C-pyruvate and autoradiography indicated that exogenous pyruvate is metabolized through the interrupted Krebs cycle. These results are explained in terms of the activity of pyruvate: ferredoxin oxidoreductase and the ATP-induced oxygen sensitivity of nitrogenase.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Single pugging events, which involve remoulding of the soil around the hooves of livestock during treading, of moderate or severe pugging intensity were imposed in plots in a long-term white clover-ryegrass pasture during spring, by using dairy cows at varying stocking rates (4·5 cows 100 m−2 for 1·5 or 2·5 h respectively). Changes in the growth and morphology of white clover were investigated over the following 12 months. Defoliation at approximately 3-week intervals was carried out by mowing. Annual herbage production was reduced following moderate and severe pugging proportionately by 0·16 and 0·34 compared with the non-pugged control treatment. The corresponding decreases in white clover production were 0·09 and 0·52 respectively. Annual perennial ryegrass production was reduced by 0·37 under severe pugging. Pugging had an immediate adverse effect on growth of white clover which persisted for up to 156 d, and coincided with a large decrease in the proportion of white clover in herbage over the same period (e.g. 0·40 vs. 0·12, in control and severely pugged treatments, respectively, on day 112). In comparison, recovery in ryegrass growth was apparent after 50 d in severely pugged treatments, indicating that white clover is more vulnerable to severe pugging than perennial ryegrass. Analysis of individual white clover plants extracted from turves (300 mm × 300 mm) showed that direct hoof damage, fragmentation and burial of stolons were the major factors which reduced white clover production, rather than the changes in soil physical properties measured. Morphological characteristics associated with plant size (e.g. stolon length, growing points, and leaf numbers) all decreased under pugging. The situation had reversed by late summer, with larger plants dominating pugged plots, and coincided with the recovery of the proportion of white clover in herbage. Strategic pasture management practices, such as restricted grazing and the use of stand-off pads when soils are overly wet, are suggested as means of minimizing treading damage to pasture and reducing negative impacts on the growth and productivity of white clover.
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  • 9
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Responses of photosynthesis (A) to intercellular CO2 concentration (ci) in 2-year-old Pinus radiata D. Don seedlings were measured at a range of temperatures in order to parametrize a biophysical model of leaf photosynthesis. Increasing leaf temperature from 8 to 30°C caused a 4-fold increase in Vcmax, the maximum rate of carboxylation (10.7–43.3 μol m−2 s−1 and a 3-fold increase in Jmax, the maximum electron transport rate (20.5–60.2 μmol m −2 s−1). The temperature optimum for Jmax was lower than that for Vcmax, causing a decline in the ratio Jmax:Vcmax from 2.0 to 1.4 as leaf temperature increased from 8 to 30°C. To determine the response of photosynthesis to leaf nitrogen concentration, additional measurements were made on seedlings grown under four nitrogen treatments. Foliar N concentrations varied between 0.36 and 1.27 mol kg−1, and there were linear relationships between N concentration and both Vcmax and Jmax. Measurements made throughout the crown of a plantation forest tree, where foliar N concentrations varied from 0.83 mol kg−1 near the base to 1.54 mol kg−1 near the leader, yielded similar relationships. These results will be useful in scaling carbon assimilation models from leaves to canopies.
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  • 10
    Publication Date: 1969-12-01
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Springer Nature
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