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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 54 (1982), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Superoxide dismutase (SOD) is present in the fronds of Lemna gibba L. Differential centrifugation showed that ca. 90% of the enzyme is present in the 140,000 g soluble cell fraction. Lemna SOD is sensitive to cyanide and is probably a Cu-Zn metallo-protein. Gel filtration showed the SOD to have a mass of 31,000 daltons. In Zn-defizient culture media, the activity of Lemna SOD was less than in fronds grown in complete nutrient media whereas in Cu-deficient media little change was found in the enzyme activity. The SOD activity in Zn-deficient plants could be partly restored to the level of Zn-sufficient fronds by adding Zn2+ to the enzyme assay solution.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 48 (1980), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The causes of cell wall necrosis in Blossom End Rot (BER) of tomatoes have been investigated by comparing enzyme activities in healthy and affected tissues in the cultivars Grenadier and Moneymaker. Changes in the mineral contents of the tomatoes were in accordance with those of calcium deficient tissues. The phenolic contents of the affected tissues were increased as also were caffeic and chlorogenic acids. Phenolase and peroxidase activities were higher in affected fruits white catalase activities were higher in healthy fruits. 14C-labelled leucine was incorporated into the proteins of the healthy fruits to the greatest extent but cell wall proteinbound hydroxyproline was greatest in affected fruits.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 58 (1983), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The growth-promoting (benzyladenine) and growth-inhibiting (abscisic acid) plant hormones, when used at concentrations of 0.4 and 4.0 μM, affect the development of superoxide dismutase (SOD) activity of Lemna fronds in opposite ways, the former hormone decreasing the activity and the latter increasing it. The effect of both growth substances is on de novo synthesis of the enzyme. In addition abscisic acid also causes the Zn, Cu and protein contents of the fronds to increase, while benzyladenine has the opposite affect.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-5036
    Keywords: Dismutase ; Fulvic acid ; Humic acid ; Lemna ; Organic matter ; Superoxide dismutase ; Xanthine oxidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Humic acid, and the acid-extracted residue obtained from it, stimulated the production of superoxide radicals (O2 .−) generated in the xanthine-xanthine oxidase system. Several synthetic humic acids, prepared by the oxidation of simple phenolic substances, also stimulated the production of O2 .− but the degree of stimulation depended on the initial phenol. Fulvic acid and water-extractable soil organic matter were less effective in stimulating O2 .− production than was humic acid. The activity of superoxide dismutase, an enzyme which destroys O2 .−, was also enhanced by HA. In contrast, fulvic acid and water-extractable soil organic matter had little effect on the activity of the dismutase.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-5036
    Keywords: Acer ; invertase ; Picea ; rhizosphere ; roots ; statistics ; trees
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A method is described for sampling rhizosphere soil under newly establishedPicea sitchensis andAcer pseudoplatanus. The technique involves taking soil samples to a depth of 150 mm at 100 mm intervals along transects, each 45° from its neighbour, radiating from the base of the stem. Invertase activities were measured in the soil samples and compared to their activities in fallow and rhizosphere soils. When the field soil was dry, the tree root systems were carefully excavated to retain as many fine roots as possible. The distribution of the soil invertase was matched to the spatial distribution of the roots showing the precise position of the rhizosphere relative to the initial ‘blind’ soil sampling. Statistics were applied to derive equations for calculating the percentage enzyme activity relative to that found in rhizosphere soil at various locations radiating from the base of the stem. This information was subsequently applied to soil sampled under trees of the same age as those excavated to give a non-destructive method for sampling rhizosphere soil routinely from under a large number of trees.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-5036
    Keywords: Beta vulgaris ; Cell walls ; Chelating agents ; Humic acid ; Hydroxyproline ; Iron ; Proline ; Proteins ; Storage tissue
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary When discs of beetroot storage tissue are washed (aged) in water for three days, there is at least a 100 per cent increase in the content of their cell-wall bound hydroxyproline. Humic acid, prepared from an agricultural soil, enhances this increase. The effects of humic acid on the increase in the hydroxyproline content of cell walls, as well as on the formation of14C-labelled hydroxyproline from14C-proline, are compared with those effects produced by the chelating agents 2,2′-dipyridyl and 8-hydroxyquinoline. It is suggested that humic acid enhances hydroxyproline formation either by a mechanism which renders more ferrous iron available for the hydroxylation of proline to hydroxyproline within the tissue, and/or a mechanism which stimulates the enzyme required for the hydroxylation process.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 184 (1996), S. 97-104 
    ISSN: 1573-5036
    Keywords: C-budgets ; Festuca ovina ; nitrogen ; Plantago lanceolata ; root exudation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A microcosm unit is described which readily allows manipulation of experimental conditions to enable the subsequent impact on root exudation release to be monitored with time. Festuca ovina and Plantago lanceolata seedlings were grown in this microcosm unit over a 34 day experimental period under conditions of high (3.75 mol m−3 N) or low (1.25 mol m−3 N) nitrate-nitrogen treatment. At the end of the experimental period the seedlings in the microcosms were labelled with [14C]-CO2 and the fate of the label within the plant and its release by the roots monitored. Total organic carbon (TOC) content of the collected exudate material was measured throughout the experimental period as well as during the 14C-chase period and comparison of plant C budgets using these two measurements is discussed. Nitrogen treatment as found to have a greater effect on exudate release by F. ovina than by P. lanceolata seedlings as indicated by both the total organic carbon and 14C results. The use and applications of the microcosm unit are discussed.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1573-5036
    Keywords: carbon-labelling ; carbon dioxide production ; decomposition ; 14C-glucose ; Lemna ; soil organic matter ; sugars ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The duckweed Lemna gibba required light and a suitable energy source such as sucrose, glucose or fructose, for maximum growth in culture. The requirement for light was relatively unimportant and the plants grew well in a photon flux density of only 52 μmol m-2s-1 PAR. The uptake and incorporation of uniformly labelled 14C-glucose into fronds was related only to the concentration of the sugar. When incubated with soil, labelled L. gibba behaved in a manner similar to that of labelled ryegrass roots which had been produced by a more elaborate technique using a 14CO2 labelled atmosphere. During incubation with soil for 224 days the L. gibba material (specific activity 6133 Bq mg-1 d. wt) lost 64% of its radioactivity as 14CO2 and ryegrass (specific activity 6634 Bq mg-1 d. wt) lost 49%. Alkaline extracted humic and fulvic acids from soil had specific activities for the L. gibba incubation of 3409 and 407 Bq mg-1 solid and for ryegrass roots of 4609 and 546 Bq mg-1 solid respectively. The production of 13C or 14C-labelled L. gibba can be undertaken using only simple equipment producing material the specific radioactivity of which can be controlled by adjusting the activity of the sugar energy source.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 160 (1994), S. 153-155 
    ISSN: 1573-5036
    Keywords: axenic conditions ; enzymes ; phenolic acids ; root exudation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Peroxidase is exuded from roots of Festuca rubra under axenic conditions. No phenolase was detected. Peroxidase can use phenolic acids. probably differentially, as hydrogen donors for the H2O2 substrate and could thus have an effect on the qualitative and quantitative determinations of phenolic acids also exuded by plants.
    Type of Medium: Electronic Resource
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