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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    Plant, cell & environment 24 (2001), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The flavonol content of Arabidopsis thaliana and tomato seedlings was assessed in conditions of reduced nitrogen or phosphorus availability. In both systems, a significant inverse relationship was observed between nutrient availability and flavonol accumulation, with nitrogen limitation promoting the greatest increase in flavonols. A trial was established to determine the effects of decreased nitrogen and phosphorus availability on the flavonol content of leaf and fruit tissues of tomato plants (Lycopersicon esculentum cv. Chaser) in a commercial situation. Nutrients were supplied by a hydroponic system with nutrient regimes designed to provide the highest and lowest nitrogen and phosphorus levels with which it is possible to support plant growth and fruit set. Fruiting was abundant and tomato fruits were harvested at mature green, breaker and red stages of ripening; leaves were also harvested from the tops of the plants. All tissues were analysed for flavonol content using reversed-phase high-performance liquid chromatography. Flavonol accumulation in the leaves of mature tomato plants was found to increase significantly in response to nitrogen stress, whereas phosphorus deficiency did not elicit this response. Reduced nitrogen availability had no consistent effect on the flavonol content of tomato fruits. Phosphorus deficiency elicited an increase in flavonol content in early stages of ripening. Effects of nutrient stress on the flavonol content of tomato fruits were lost as ripening progressed. The findings suggest that nutrient status may be employed to manipulate the flavonol content of vegetative tissues but cannot be used to elevate the flavonol content of tomato fruit.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 72 (1987), S. 1-7 
    ISSN: 1432-1939
    Keywords: Aufwuchs algae ; Campostoma ; Fertilizer ; Nutrients ; Grazing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Previous studies have shown that an algivorous grazing minnow (Campostoma anomalum) is the major herbivore in Brier Creek, a hardwater stream in south central Oklahoma. In summer and autumn schools of Campostoma virtually eliminate algae from substrate surfaces in deeper areas of some pools. The pool-to-pool distributions of algae and Campostoma reported for this stream could occur if nutrient limitation permits grazing by Campostoma to “outrun” algal growth. To test this hypothesis, mesh pens were built to exclude Campostoma from substrates in each of four typical Campostoma pools. N+P+K lawn fertilizer was added daily to two of the four pools; the other two, which received no fertilizer additions and which were not visibly affected by fertilizer transported downstream from the pools enriched with nutrients, served as controls. Algae accumulated rapidly on natural substrates and on unglazed ceramic tiles in grazer-exclusion pens in pools receiving N+P+K additions and more slowly in pens in both control pools. Periphyton biomass on grazed substrates in all four pools remained low throughout the experiment. Hence, Campostoma at normal densities were able to outrun algal growth even when nutrients were added. Eleven days after the experiment started, I determined biomass, biomass-specific net primary productivity, and areal net primary productivity of periphyton on substrates exposed to all combinations of grazer (+,0) and nutrient (+,0) treatments. Grazing increased biomass-specific primary productivity, prevented accumulation of biomass, and decreased areal primary productivity of periphyton. Additions of N+P+K increased biomass-specific net primary productivity of grazed and ungrazed periphyton and markedly increased biomass of periphyton on substrates protected from Campostoma. Although food supply for Campostoma appeared to be greater with nutrient additions, condition of Campostoma in pools receiving N+P+K was not significantly different from Campostoma collected from control pools 35 days after the experiment started. I conclude that although nutrient supply limits biomass-specific primary productivity of periphyton in Brier Creek, nutrient limitation in this stream exacerbates, rather than causes, the visually conspicuous pool-to-pool complimentary distribution of algae and Campostoma: in this stream, grazing by Campostoma at natural densities can outrun periphyton growth even when nutrients are added.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 52 (1982), S. 269-272 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Dry weight allocation to vegetative and reproductive structures in six perennial herbs was studied at three successional sites (quarry, grassland and scrub) on the magnesian limestone in County Durham, England, during the summer of 1978. Two species showed little difference between sites but the other four all displayed the same pattern. Population reproductive effort was highest in the quarry and lowest in the grassland. Reproductive effort of flowering individuals however was the same at all three sites, so that between-site differences in population reproductive effort were entirely a consequence of variation in the proportion of plants which flowered. Indirect evidence suggests that initiation of flowering may be triggered by the attainment of a critical leaf weight. It is suggested that the between-site differences can be explained in terms of the levels of competition at each site and that reproductive effort does not necessarily decline uniformly during succession.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 75 (1988), S. 320-320 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 87 (1991), S. 336-342 
    ISSN: 1432-1939
    Keywords: Fish ; Fish community structure ; Habitat selection ; Headwater streams ; Predation risk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Surveys of 262 pools in 3 small streams in eastern Tennessee demonstrated a strong positive relationship between pool depth and the size of the largest fish within a pool (P〈0.001). Similarly, the largest colonizers of newly-created deep pools were larger than the colonizers of shallow pools. We explored the role of predation risk in contributing to the “bigger fish — deeper habitat” pattern, which has been noted by others, by conducting five manipulative field experiments in two streams. Three experiments used stoneroller minnows (Campostoma anomalum); one used creek chubs (Semotilus atromaculatus); and one used striped shiners (Notropis chrysocephalus). The stoneroller experiments showed that survival of fish approximately 100 mm in total length (TL) was much lower in shallow pools (10 cm deep) than in deep (40 cm maximum) pools (19% versus 80% survival over 12 d in one experiment) and added cover markedly increased stoneroller survival in shallow pools (from 49% to 96% in an 11-d experiment). The creek chub experiment showed that, as for stonerollers, pool depth markedly influenced survival: the chubs survived an average of 4.9 d in shallow pools and 〉10.8 d in deep pools. In the striped shiner experiment in shallow artificial streamside troughs, no individuals 75–100 mm TL survived as long as 13 d, where-as smaller (20–25 mm) fish had 100% survival over 13 d. The results of the experiments show that predation risk from wading/diving animals (e.g., herons and raccoons) is much higher for larger fishes in shallow water than for these fishes in deeper water or for smaller fish in shallow water. We discuss the role of predation risk from two sources (piscivorous fish, which are more effective in deeper habitats, and diving/wading predators, which are more effective in shallow habitats) in contributing to the bigger fish — deeper habitat pattern in streams.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Ecotoxicology 8 (1999), S. 311-320 
    ISSN: 1573-3017
    Keywords: phytoremediation ; VOCs ; volatile organic pollutants ; air cleansing by plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract We conducted laboratory tests with six species of plants to determine their ability to remove benzene, trichloroethylene (TCE) and toluene from air. The objective of this proof-of-principal study was to evaluate the idea that phytoremediation techniques might be used to lower the concentrations of indoor air pollutants, such as volatile or semi-volatile organic compounds. Plants were exposed to the pollutants singly or in mixtures in an airtight chamber, and concentrations of the pollutants in the chamber were monitored through time to assess plant effects on the pollutants. In several experiments, we measured air temperature and CO2, as well. Lower surfaces of leaves of several of the species we tested were also examined by scanning electron microscopy to determine stomate abundance and size, and to provide information about leaf-surface elemental composition (by X-ray emission spectroscopy). Several of the species demonstrated an extensive ability to remove benzene from air. Gas chromatography methods allowed a reasonably direct, continuous monitoring of the kinetics and overall efficiency of the pollutant-removal process. We found that pollutant removal efficiency varied in response to plant species and the pollutant. Of the pollutants tested, benzene was most efficiently removed from air by Pelargonium domesticum, Ficus elastica and Chlorophytum comosum. Kalanchoe blossfeldiana, a common ornamental plant, appeared to take up benzene selectively over toluene, and TCE was removed efficiently from the air by C. comosum. Pentane, sometimes used as an internal standard in GC/MS, was removed from air by at least four of the species. For C. comosum, TCE appeared to lower the removal rates of benzene and pentane. Low-vacuum scanning electron microscopy provided information on stomate size and density and permitted rapid initial elemental analysis of the plant-leaf surface by X-ray emission spectroscopy. Our results indicate that simple tests for pollutant uptake, morphological and chemical features of plants, and plant detoxification enzyme activity might be used in multivariate fashion to identify plant species capable of removing volatile or semi-volatile pollutants from air.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Ecotoxicology 5 (1996), S. 377-393 
    ISSN: 1573-3017
    Keywords: ambient toxicity testing ; Ceriodaphnia ; fathead minnow larvae ; biological monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The purpose of this paper is to show how short-term laboratory tests, conducted according to US Environmental Protection Agency (EPA) procedures, can be used effectively to assess water-quality conditions in streams or rivers that receive pollutants from industry or municipal or agricultural areas. Standardized, short-term tests with fish, aquatic invertebrates or algae are commonly used to estimate the acute or chronic toxicity of wastewaters; this is referred to as effuent testing. The methods used for testing effluents also can be used to assess water quality in receiving streams: in this application, the procedures are referred to as ambient testing. Despite similarity in methods, the major objective of effluent testing differs importantly from that of ambient testing. In effluent testing, the key objective is to determine how toxic an effluent is; in ambient testing, the main objective usually is that of determining if the water at a site is toxic. This difference is subtle but very important: it shapes the strategy for cost-effective ambient testing, and determines the framework for effective statistical analysis and interpretation of ambient toxicity test results. Specific case-study examples are provided demonstrating the kinds of information that can be extracted from ambient toxicity testing by use of different statistical methods, including analysis of variance, contingency-table analysis, and two types of multivariate procedures (principal components analysis and logistic regression). Examples also are given supporting the idea that an effective ambient testing programme should be long-term, and contain a diagnostic-testing component analogous to the toxicity identification procedures used to supplement effluent-testing programmes. Recommendations derived as ‘lessons learned’ from largescale ambient toxicity testing programmes for receiving streams at Department of Energy facilities include: (1) testing more frequently with one species (preferably Ceriodaphnia) generally is more effective, in terms of information gained per dollar spent, than testing less frequently with two or more species; (2) use five or more sites per test period, plus two or more reference sites, whenever possible; (3) use four to six test periods per year; and (4) use diagnostic testing to supplement the ambient-testing programme. Various laboratory and in situ methods for environmental assessment are now under development, but these methods probably will not gain acceptance for use in regulatory situations for many years. Rapid growth in need for ecological risk assessments outstrips the rate at which new test procedures are approved for regulatory purposes. Thus, laboratory tests for estimating possible environmental impacts of toxic or disruptive pollutants are likely to be used more frequently during the next decade.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 25 (1892), S. 2555-2563 
    ISSN: 0365-9496
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    Publication Date: 2003-11-21
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 10
    Publication Date: 2012-06-18
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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