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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology 32 (1996), S. 947-957 
    ISSN: 1573-5028
    Keywords: Botrytis cinerea ; in planta gene expression ; Lycopersicon esculentum ; plant defense ; pathogenicity gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Establishment of a plant-pathogen interaction involves differential gene expression in both organisms. In order to isolate Botrytis cinerea genes whose expression is induced during its interaction with tomato, a comparative analysis of the expression pattern of the fungus in planta with its expression pattern during in vitro culture was performed by differential display of mRNA (DDRT-PCR). Discrimination of fungal genes induced in planta from plant defense genes induced in response to the pathogen was attempted by including in this comparative analysis the expression patterns of healthy tomato leaves and of tomato leaves infected with two different pathogens, either Phytophthora infestans or tobacco necrosis virus (TNV). Using a limited set of primer combinations, three B. cinerea cDNA fragments, ddB-2, ddB-5 and ddB-47, were isolated representing fungal genes whose expression is enhanced in planta. Northern blot analysis showed that the transcripts detected with the cDNA clones ddB-2 and ddB-5 accumulated at detectable levels only at late time points during the interaction. The cDNA clone ddB-47 detected two different sizes of transcripts displaying distinct, transient expression patterns during the interaction. Sequence analysis and database searches revealed no significant homology to any known sequence. These results show that the differential display procedure possesses enough sensitivity to be applied to the detection of fungal genes induced during a plant-pathogen interaction. Additionally, four cDNA fragments were isolated representing tomato genes induced in response to the infection caused by B. cinerea, but not by P. infestans.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Aquatic ecology 31 (1997), S. 349-359 
    ISSN: 1573-5125
    Keywords: suspension-feeding bivalves ; phytoplankton ; nutrient cycling ; primary production ; carrying capacity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This paper gives an overview of interactions betweenbivalve grazing and ecosystem processes, that mayaffect the carrying capacity of ecosystems for bivalvesuspension feeders. These interactions consist of anumber of positive and negative feedbacks.Bivalve grazing can result in local food depletion,which may negatively influence bivalve growth. On alarger scale, it may induce a top-down control ofphytoplankton biomasss, and structural shifts inphytoplankton composition. In the case of harmfulalgal blooms, phytoplankton may negatively affectbivalve grazing rates.The processing of large amounts of particulate mattermay change nutrient cycling on the scale of estuaries,and can result in changes in the inorganic nutrientpool available for phytoplankton, through regenerationand reduced storage of nutrients in algal biomass.This can reduce nutrient limitation of thephytoplankton and stimulate algal growth rates.Observations from mesocosm studies suggest that apositive feedback from bivalve grazing onphytoplankton growth may also change the physiologicalstate of the algae and improve food quality.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Aquatic ecology 31 (1997), S. 409-421 
    ISSN: 1573-5125
    Keywords: bivalves ; ecosystems ; carrying capacity ; turnover time ; mussels ; oysters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The carrying capacity of suspension feeding bivalvesin 11 coastal and estuarine ecosystems is examined. Bivalve carrying capacity is defined in terms of watermass residence time, primary production time andbivalve clearance time. Turnover times for the 11ecosystems are compared both two and threedimensionally. Fast systems, e.g., Sylt and NorthInlet, have turnover times of days or less, while,slow systems, e.g., Delaware Bay, have turnover timesof months and years. Some systems,Marennes-Oléron, South San Francisco Bay and NorthInlet, require a net influx of phytoplankton in orderto support their bivalve populations. Three systems,Carlingford Lough, Chesapeake Bay and Delaware Bay,have very long bivalve clearance times due to small orreduced bivalve filter feeder populations. Carlingford Lough stands out because it is a naturallyplanktonic system now being converted to bivalveculture with an adherently stronger benthic-pelagiccoupling. Existing models of bivalve carrying capacity arereviewed. The Herman model is utilized as anappropriate ecosystem level model to examine carryingcapacity because it includes the three major turnovertime elements of water mass residence time, primaryproduction time and bivalve filter feeder clearancetime. The graphical analysis suggests that massive andsuccessful bivalve filter feeder populations are foundin systems with relatively short residence times(〈40 days) and short primary production times (〈4days) in order to sustain a high bivalve biomass withits associated rapid clearance times. Outliersystems are constrained by long water mass residencetimes, extended primary production times, and longclearance times.
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  • 4
    ISSN: 1573-5125
    Keywords: eutrophication ; mesocosm ; phytoplankton ; zooplankton ; macrobenthos
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of nutrient loading on phytoplankton, zooplankton and macrozoobenthos in experimental ecosystems was studied in a 7-month experiment. The mesocosms were designed to mimic the major physical characteristics (irradiance, temperature, mixing) of the Dutch coastal zone in the river Rhine plume. Three different nutrient loading scenarios were used, representing present and future conditions. The level of the spring phytoplankton bloom was determined by phosphorus loading, whereas during summer the nitrogen loading determined phytoplankton biomass. The differences in nutrient loading did not result in shifts in phytoplankton species composition. With exception of the early phase of the spring bloom, diatoms dominated phytoplankton biomass in all nutrient treatments. This was ascribed to microzooplankton grazing on smaller algal species. Microzooplankton biomass showed a positive correlation with primary production, and also significant differences between nutrient treatments. Copepod development was limited, probably due to competition with microzooplankton and predation by benthic fauna. Macrobenthos biomass correlated with primary production, and was lower in the lowest nutrient treatment.
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