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  • 1
    Electronic Resource
    Electronic Resource
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 103 (1998), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Variable internal plant nutrient content may confound plant response to environmental stress. Plant nutrient content may be controlled with relative addition rate techniques in solution culture. However, because raising large numbers of plants in flowing solution culture is difficult, we investigated the feasibility of raising plants in soil mix using relative fertilizer additions. Aspen (Populus tremuloides Michx.) clones (216, 259 and 271) planted in pots containing a peat, sand and vermiculite (2:1:1, v/v/v) soil mix were grown with exponentially increasing fertilizer concentrations and harvested periodically to assess growth. Addition rate treatments ranged from 0.01 to 0.05 day−1. The lag phase of growth, in which plants adjusted to the fertilizer regime, lasted 40 days after which plants entered the experimental period characterized by constant relative growth rates equivalent to applied fertilizer addition rates. Total plant nutrient concentration was (1) unique for each addition rate, (2) linearly related to addition rate and growth rate, and (3) tended to increase at the highest, and decrease at the lowest addition rates. Regardless, the plants appeared to have attained steady-state conditions. Allocation of carbon to roots increased with lower addition rate treatments and was not dependent upon ontogeny. There were no treatment differences in growth response among aspen clones. Yet there were treatment differences in leaf chlorophyll and photosynthesis within the clones. For the 0.05 day−1 addition rate treatment, chlorophyll, leaf N concentration and photosynthetic rate were strongly correlated with one another, were at a maximum in recently mature leaves, and rapidly declined with leaf age. The rate of decline in these leaf characteristics was slowest in clone 271, consistent with the leaf longevity stress response reported elsewhere. Plant responses from these relative fertilizer addition trials in soil mix agree closely with those run in hydroponics, indicating that steady-state nutrition can be achieved with a technically simple experimental assemblage.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract: Tn phoA has been introduced with high efficiency into the chromosome of the phytopathogenic bacterium Erwinia amylovora. Transposition occurred with apparent randomness and single insertions were predominant. Fusion proteins were detected in cell envelope fractions from PhoA+ mutants and a range of alkaline phosphatase activities was onserved. The results provide the first evidence that sequences encoding signal peptides are present in E. amylovora and that Tn phoA may be a valuable tool for the study of the translocation, regulation and function of E. amylovora extracytoplasmic proteins. In particular, Tn phoA mutagenesis should be applicable to the identification of cell envelope proteins involved in the virulence of this organism.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 550 (July 2007), p. 35-44 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Iterative processing, involving sequential deformation and annealing, has been carried out oncopper specimens with the aim of grain boundary engineering (GBE) them. The data have providedsome interesting insights into the mechanisms of GBE. The results have demonstrated that developmentof a high proportion of Σ3s is beneficial to properties, as shown by improved strain-to-failure for thesame strength. The proportion of Σ3s saturates at approximately 60% length fraction. Analysis of thedata indicates that iterative processing is not always necessary for the development of beneficialproperties, and it is further suggested that the condition of the starting specimen has a large influence onthe subsequent microstructural development. The present, new data are also compared with previousresearch on copper where all five parameters of the grain boundary network population have beenmeasured
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-5117
    Keywords: saline lakes ; benthic invertebrate ; salt tolerance ; bioassay ; microcosm ; Pyramid Lake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Salinity of Pyramid Lake increased from 3.7 to 5.5‰ between 1933 and 1980. Concern over future reductions in overall species richness prompted experiments to assess responses of dominant lake organisms to elevated salinity. Salinity tolerances of three important benthic invertebrates, Hyalella aztecta, Chironomus utahensis, and Heterocypris sp., were tested in controlled laboratory bioassays and also in a semi-natural environment consisting of large (47 m3) mesocosms. Densities of H. azteca in mesocosms were significantly lower at salinities of 8.0 and 11.0‰ compared with 5.6‰ controls in year one, but not in 8.5‰ salinity mesocosms in year two. The 96-h LC50 for H. azteca was high at 19.5‰. Short-term mortalities of C. utahensis were 100% at salinities of 13.3‰ and greater. Fifty-seven percent fewer larvae matured from third to fourth instar at 8.9 than at 5.5‰ salinity in 17 day subacute bioassays. Furthermore, larval chironomid densities and emergence of adults from mesocosms were significantly reduced at salinities of 8.0‰ and higher compared with controls. Mortality of Heterocypris sp. was 50% at a salinity of 18.6‰ in laboratory bioassays and populations in mesocosms ranged between 40 and 100% lower at salinities of 8.0 and 11.0‰ than in controls. Multiple generation mesocosm experiments indicated all three invertebrates were more sensitive to elevated salinity than results of short-term bioassays. Our studies suggest populations of these invertebrates may be reduced from present levels if Pyramid Lake's salinity were to double, although none are expected to be extirpated. Food habit shifts and reduced production of lake fishes are likely consequences of salinity-induced disruption in the benthic invertebrate forage base.
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  • 5
    Publication Date: 2008-06-01
    Description: Increased forest productivity has been obtained by improving resource availability through water and nutrient amendments. However, more stress-tolerant species that have robust site requirements do not respond consistently to irrigation. An important factor contributing to robust site requirements may be the distribution of biomass belowground, yet available information is limited. We examined the accumulation and distribution of above- and below-ground biomass in sweetgum ( Liquidambar styraciflua L.) and loblolly pine ( Pinus taeda L.) stands receiving irrigation and fertilization. Mean annual aboveground production after 4 years ranged from 2.4 to 5.1 Mg·ha–1·year–1 for sweetgum and from 5.0 to 6.9 Mg·ha–1·year–1 for pine. Sweetgum responded positively to irrigation and fertilization with an additive response to irrigation + fertilization. Pine only responded to fertilization. Sweetgum root mass fraction (RMF) increased with fertilization at 2 years and decreased with fertilization at 4 years. There were no detectable treatment differences in loblolly pine RMF. Development explained from 67% to 98% of variation in shoot versus root allometry for ephemeral and perennial tissues, fertilization explained no more than 5% of the variation in for either species, and irrigation did not explain any. We conclude that shifts in allocation from roots to shoots do not explain nutrient-induced growth stimulations.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 6
    Publication Date: 2012-05-01
    Description: Soil properties and forest productivity can be affected during ground-based harvest operations and site preparation. The degree of impact varies widely depending on topographic features and soil properties. Forest managers who understand site-specific limits to ground-based harvesting can alter harvest method or season to limit soil disturbance. To determine the potential areal extent of detrimental (potentially plant growth limiting) soil disturbance based on site characteristics and season of harvest, we developed a predictive model based on soil monitoring data collected from 167 ground-based harvest units. Data collected included dominant site parameters (e.g., slope, aspect, soil texture, and landtype), harvest season, harvest type (intermediate or regeneration), and the machine(s) used during ground-based harvest operations. Aspect (p = 0.0217), slope (p = 0.0738), landtype (p = 0.0002), and the interaction of harvest season × landtype (p = 0.0002) were the key variables controlling the areal extent and magnitude of detrimental soil disturbance. For example, harvesting during non-winter months on gently rolling topography resulted in greater soil disturbance than similar harvest operations on landscapes that are highly dissected. This is likely due to the ease with which equipment can move off designated trails. A geospatially explicit predictive model was developed using general linear model variables found to significantly influence the areal extent of detrimental soil disturbance on nine defined landtypes. This tool provides a framework that, with local calibration, can be used on other forest lands as a decision support tool to geospatially depict landtypes susceptible to detrimental soil disturbance during ground-based harvest operations.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 7
    Publication Date: 1992-07-01
    Description: Root and needle cold hardiness were compared in seedlings of subalpine conifers to determine if differences existed among species originating from either cold continental climates or mild maritime climates. Abiesamabilis (Dougl.) Carr. and Tsugamertensiana (Bong.) Carr. are exclusively distributed in maritime environments, while Abieslasiocarpa (Hook.) Nutt. and Pinuscontorta Dougl. are more generally distributed in both continental and maritime environments. Because of the differing winter soil conditions of these two climatic types, special emphasis was placed on root cold hardiness. Cold hardiness for root samples, as measured by a decrease in the electrolyte leakage, was much greater for A. amabilis and A. lasiocarpa than for P. contorta and T. mertensiana (−11.4, −11.5, −7.5, and −7.5 °C, respectively). Thus, subalpine conifer species distribution was not found to be influenced by root cold hardiness. Root cold hardiness of field-grown seedlings paralleled changes in soil temperature through February. Under constant temperature conditions (3 °C) the maximum cold hardiness achieved in 6 weeks was not subsequently maintained in A. amabilis and A. lasiocarpa. Injury in unhardened roots was coincident with bulk freezing, whereas hardened roots were able to tolerate bulk freezing. Needles had more than three times the level of cold hardiness of roots when measured in December, All species except P. contorta reached needle cold hardiness levels below −40 °C.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 8
    Publication Date: 2018-05-01
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 9
    Publication Date: 2014-01-01
    Print ISSN: 0361-5995
    Electronic ISSN: 1435-0661
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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  • 10
    Publication Date: 2015-07-01
    Print ISSN: 0047-2425
    Electronic ISSN: 1537-2537
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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