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  • 1
    Electronic Resource
    Electronic Resource
    Allochthonous and autochthonous particulate organic matter in floodplains of the River Danube: the importance of hydrological connectivity (2003)
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 48 (2003), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY 1. The elemental composition, the proportion of living organic carbon and the carbon stable isotope signatures of particulate organic matter (POM) were determined in a large river floodplain system in order to elucidate the major carbon sources in relation to the hydrological conditions over a 13-month period.2. Two floodplain segments and the main channel of the River Danube downstream of Vienna (Austria), were compared on the basis of discharge and water age estimations. The more dynamic floodplain was connected to the main channel for 46% of the study period and drained up to 12% of total discharge at high water.3. The mean C : N ratio and δ13C signature of the POM increased from the floodplain site that was more isolated from the river (6.6; −33‰) to the main channel (8.4; −25‰). At the dynamic floodplain site, the C : N ratio and the δ13C signature of the POM increased with hydrological connectivity (expressed as water age).4. Only during flood events (4% frequency of occurrence), a considerable input of riverine POM was observed. This input was indicated by a C : N ratio of the POM pool of more than 10, the amount of detrital carbon (〉80% of the total POM pool) and a δ13C signature of POM of more than −25‰ in the dynamic floodplain.5. Plankton derived carbon, indicated by C : N ratios less than eight and δ13C values lower than −25‰, dominated the particulate organic carbon (POC) pool at both floodplain sites, emphasising the importance of local (autochthonous) production. Phytoplankton was the major plankton compartment at the dynamic site, with highest biomasses at medium water ages.6. At the dynamic floodplain site, the Danube Restoration Project has enhanced the duration of upstream surface connection with the main channel from 4 to 46% frequency of occurrence. Therefore, the export of living POC to the main channel is now established during phases of maximum phytoplankton production and doubled the estimated total export of non-refractory POM compared with prerestoration conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2003.00981.x
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  • 2
    Electronic Resource
    Electronic Resource
    Phosphoenolpyruvate carboxylase in mistletoe leaves: Regulation of gene expression, protein content, and covalent modification (2001)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 112 (2001), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Seasonal changes in the activity of phosphoenolpyruvate carboxylase (PEPCase, EC 4.1.1.31), a key enzyme in the interaction of carbohydrate and nitrogen metabolism, were studied in leaves of the C3 semiparasitic mistletoe, Viscum album, growing on different host trees. Maximum extractable PEPCase activities were higher in leaves of mistletoes growing on Betulapendula and Alnusglutinosa hosts compared with those on the conifers, Abies alba and Larix decidua. Independent of host, maximum extractable PEPCase activities were high in spring and autumn while low in summer. Samples with higher PEPCase activities showed higher amounts of PEPCase protein and higher PEPCase mRNA levels. A curvilinear correlation between leaf total nitrogen content and the maximum extractable PEPCase activity as well as PEPCase mRNA level suggested that nitrogen might affect the activity of PEPCase of mistletoe by up-regulating gene expression. In addition to extractable activity, seasonal changes of the PEPCase activation state, the ratio of activities resulting from limited:non-limited assays, were found, which was correlated to the variation of malate content in leaves of mistletoe. ATP-dependent activation of PEPCase was characterized by an increase in I0.5(l-malate), indicating that PEPCase of leaves of mistletoes is probably regulated via phosphorylation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2001.1120307.x
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  • 3
    Electronic Resource
    Electronic Resource
    Direct dating of Early Upper Palaeolithic human remains from Mladeč (2005)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 435 (2005), S. 332-335 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The human fossil assemblage from the Mladeč Caves in Moravia (Czech Republic) has been considered to derive from a middle or later phase of the Central European Aurignacian period on the basis of archaeological remains (a few stone artefacts and organic items such as bone points, awls, ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature03585
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  • 4
    Electronic Resource
    Electronic Resource
    Biosynthesis and accumulation of D-ononitol in Vigna umbellata in response to drought stress (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 101 (1997), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Metabolic responses to water deficit that lead to an accumulation of cyclitols, have been examined in rice bean (Vigna umbellata [Thunb.] Ohwi et Ohashi). Imposition of drought stress by withholding water from the soil for 9 days led to an accumulation of D-ononitol (lD-4-O-methyl-myo-inositol) which was most pronounced in leaves (from 33 to 88 umol g−1 dry mass). However, the activity of the enzyme myo-inositol 6-O-methyltransferase (m6OMT, EC 2.1.1.X), which catalyzes the synthesis of ononitol from myo-inositol and S-adenosyl-L-methionine (AdoMet), increased in stems but not in leaves during the drought stress experiment. Detailed analysis of different plant parts revealed that the accumulation of ononitol in leaves was linearly related to stem m6OMT activity during drought stress, indicating that m6OMT may control the in vivo biosynthetic rate of this cyclitol. The availability of myo-inositol, required for enhanced rates of ononitol synthesis by m6OMT, increased during the stress experiment, while the capacity to synthezise AdoMet by S-adenosyl-L-methionine synthetase (SMS, EC 2.5.1.6) decreased. However, the high capacity for degradation of S-adenosyl-L-homocysteine (AdoHcy; a potent competitive inhibitor of m6OMT) by the enzyme S-adenosyl-L-homocysteine hydrolase (SHH, EC 3.3.1.1) provided favourable conditions for ononitol biosynthesis during the whole stress treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1997.tb01016.x
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  • 5
    Electronic Resource
    Electronic Resource
    Purification and characterization of myo-inositol 6-O-methyltransferase from Vigna umbellata Ohwi et Ohashi (1995)
    Springer
    Planta 197 (1995), S. 427-434 
    Details
    ISSN: 1432-2048
    Keywords: Cyclitol biosynthesis ; myo-Inositol 6-O-methyltransferase ; Ononitol ; Vigna
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cyclitol 1d-4-O-methyl-myo-inositol (d-ononitol) is accumulated in certain legumes in response to abiotic stresses. S-Adenosyl-l-methionine:myo-inositol 6-O-methyltransferase (m6OMT), the enzyme which catalyses the synthesis of d-ononitol, was extracted from stems of Vigna umbellata Ohwi et Ohashi and purified to apparent homogeneity by a combination of conventional chromatographic techniques and by affinity chromatography on immobilized S-adenosyl-l-homocysteine (SAH). The purified m6OMT was photoaffinity labelled with S-adenosyl-l-[14C-methyl]methionine. The native molecular weight was determined to be 106 kDa, with a subunit molecular weight of 40 kDa. Substrate-saturation kinetics of m6OMT for myo-inositol and S-adenosyl-l-methionine (SAM) were Michaelis-Menten type with K m values of 2.92 mM and 63 μM, respectively. The SAH competitively inhibited the enzyme with respect to SAM (K i of 1.63 μM). The enzyme did not require divalent cations for activity, but was strongly inhibited by Mn2+, Zn2+ and Cu2+ and sulfhydryl group inhibitors. The purified m6OMT was found to be highly specific for the 6-hydroxyl group of myo-inositol and showed no activity on other naturally occurring isomeric inositols and inositol O-methyl-ethers. Neither d-ononitol, nor d-3-O-methyl-chiro-inositol, d-1-O-methyl-muco-inositol or d-chiro-inositol (end products of the biosynthetic pathway in which m6OMT catalyses the first step), inhibited the activity of the enzyme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196663
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of rhizospheric bicarbonate on net nitrate uptake and partitioning between the main nitrate utilising processes in Populus canescens and Sambucus nigra (2000)
    Springer
    Plant and soil 221 (2000), S. 13-24 
    Details
    ISSN: 1573-5036
    Keywords: assimilation ; dissolved inorganic carbon ; nitrate ; uptake ; xylem transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Increased levels of rhizospheric dissolved inorganic carbon have repeatedly been demonstrated to enhance plant growth by up to 80%, although carbon from dark fixation accounts for only 1–3% of total plant carbon gain. This study, therefore, aimed at investigating the effects of bicarbonate on nitrate uptake, assimilation and translocation to shoots. Clonal saplings of poplar (Populus canescens(Ait.) Sm.) and elder (Sambucus nigraL.) were grown hydroponically for 35 days in a nutrient solution containing 0, 0.5 and 1 mM bicarbonate and 2 mM nitrate as the sole nitrogen source at pH 7.0. Net nitrate uptake, root nitrate accumulation and reduction, and export of nitrogenous solutes to shoots were measured after incubating plants with 15N-labelled nitrate for 24 h. Net nitrate uptake increased non-significantly in plant species (19–61% compared to control plants) in response to 1 mM bicarbonate. Root nitrate reduction and nitrogen export to shoots increased by 80 and 95% and 15 and 44% in poplar and elder, respectively. With enhanced root zone bicarbonate, both species also exhibited a marked shift between the main nitrate utilising processes. Poplar plants increasingly utilised nitrate via nitrate reduction (73–88% of net nitrate uptake), whereas the proportions of export (20–9%) and storage in roots (7–3%) declined as plants were exposed to 1 mM external bicarbonate. On the other hand, elder plants exhibited a significant increase of root nitrate reduction (44–66%) and root nitrate accumulation (6–25%). Nitrate translocation to elder shoots decreased from 50 to 8% of net nitrate uptake. The improved supply of nitrogen to shoots did not translate into a significant stimulation of growth, relative growth rates increased by only 16% in poplar saplings and by 7% in elder plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004745823911
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  • 7
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    Assimilation of Particular Organic Matter and Dissolved Organic or Inorganic Compounds by Cribroelphidium selseyense (Foraminifera) (2021)
    Frontiers
    Details
    Publication Date: 2024-02-07
    Description: Marine carbon and nitrogen processing through microorganisms’ metabolism is an important aspect of the global element cycles. For that purpose, we used foraminifera to analyze the element turnover with different algae food sources. In the Baltic Sea, benthic foraminifera are quite common and therefore it is important to understand their metabolism. Especially, Cribroelphidium selseyense, also occurring in the Baltic Sea, has often been used for laboratory feeding experiments to test their effect on carbon or nitrogen turnover. Therefore, foraminifera were collected from the Kiel Fjord and fed with six different algal species in two qualities (freeze-dried algae vs. fresh algae, all 13C- and 15N-labeled). Also, labeled dissolved inorganic C and N compounds and glucose were offered to the foraminifera to test direct assimilation of dissolved compounds (carbon and nitrogen) from the water column. Our experiments showed that after 15 days of incubation, there were highly significant differences in isotope labeling in foraminifera fed with fresh algae and dry algae, depending on algal species. Further, different algal species led to different 13C and 15N enrichment in the studied foraminifera, highlighting a feeding preference for one diatom species and an Eustigmatophyte. A significant carbon assimilation from HCO3– was observed after 7 days of incubation. The N assimilation from NH4+ was significantly higher than for NO3– as an inorganic N source. The uptake of glucose showed a lag phase, which was often observed during past experiments, where foraminifera were in a steady state and showed no food uptake at regular intervals. These results highlight the importance of food quality on the feeding behavior and metabolic pathways for further studies of foraminiferal nutrition and nutrient cycling.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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