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  • 11
    Electronic Resource
    Electronic Resource
    Uptake of CO2 by aquatic vegetation (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 8 (1985), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Photosynthesis by aquatic plants based on the supply of CO2 from air-equilibrated solutions may be limited by the low diffusion coefficient of CO2 in water. For plants in which the transport of CO2 from the bulk medium is by diffusion, and the initial carboxylation uses RUBISCO, CO2 supply can be increased by growth in habitats with fast water flow over the surface (reducing unstirred layer thickness), or with heterotrophically-augmented CO2 levels, including the direct use of sediment CO2. Many aquatic plants using RUBISCO as their initial carboxylase counter the limitations on CO2 supply via the operation of biophysical CO2 concentrating mechanisms which are based on active transport of HCO−3, CO2 or H+ at the plasmalemma, and use bulk-phase HCO−3 or CO2 as the C source. A final group of aquatic plants use biochemical CO2 concentrating mechanisms based on auxiliary carboxylation by PEPc: C4-like and Crassulacean Acid Metabolism–like processes are involved. These various mechanisms for increasing CO2 supply to RUBISCO also help to offset the low specific reaction rate of aquatic plant RUBISCOs at low [CO2] and low [CO2]: [CO2]. In addition to overcoming restrictions on CO2 supply, the various methods of increasing inorganic C availability may also be important in alleviating shortages of nitrogen or photons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1985.tb01677.x
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  • 12
    Electronic Resource
    Electronic Resource
    Accumulation and subcellular distribution of cations in relation to the growth of potassium-deficient barley (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 9 (1986), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Growth of barley (Hordeum vulgare L., cv. Georgie) was insensitive to soil K content above about 150 mg kg−1, but at lower levels it declined. The reduction in yield was greater in soils containing approximately 10 mg Na kg−1 than in soils with about 90 mg kg−1 of Na. Growth was unaffected by changes in shoot K concentration above 75 mol m−3, but declined at lower concentrations, and the decrease was less in plants grown in soils with high Na. Growth responses were not simply related to tissue K concentrations because plants grown in soils with extra Na had higher yields but lower K concentrations.When soil Na was low, plants accumulated Ca as tissue K declined, but when Na was provided this ion was accumulated. Plant Mg concentrations were generally low but increased as K decreased. The Ca and Mg were osmotically active. There were highly significant inverse linear relationships between yield and either the Ca or Mg concentrations in the shoots.X-ray microanalysis was used to examine the compartmentation of cations in leaves from barley plants (cv. Clipper) grown in nutrient solutions with high and low K concentrations. In plants grown with 2.5 mol m−3 K, this was the major cation in both the cytoplasm and vacuole of mesophyll cells. However, in plants grown with 0.02 mol m−3 K it declined to undetectable levels in the vacuole, although it was still detectable in the cytoplasm. In all plants, Ca was mainly located in epidermal cells. The implication of the results for explaining responses to K. in terms of compartmentation of solutes is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11616346
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  • 13
    Electronic Resource
    Electronic Resource
    The utilization of bicarbonate ions by the macroalga Ascophyllum nodosum (L.) Le Jolis (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 9 (1986), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract A comparison of some of the methods used to determine whether aquatic plants have the ability to utilize bicarbonate ions as a source of inorganic carbon for photosynthesis has been applied to the intertidal macroalga Ascophyllum nodosum. These include: observing photosynthesis at a high pH (below the alga's CO2 compensation point), pH compensation point determinations, comparing the photosynthetic characteristics at low pH (5.20) and at high pH (7.95), estimating the maximal rates at which CO2 can diffuse through the unstirred layer and the rate at which CO2 can be produced from bicarbonate dehydration in the unstirred layer. All indicated that Ascophyllum nodosum can use bicarbonate ions for photosynthesis, though some were not always consistent. Calculating the total inorganic carbon concentration from pH measurements and acidification CO2 determinations revealed that the assumption that the alkalinity remains constant during pH drift experiments is not always valid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11611615
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  • 14
    Electronic Resource
    Electronic Resource
    Transcription of rhiA, a gene on a Rhizobium leguminosarum bv. viciae Sym plasmid, requires rhiR and is repressed by flavanoids that induce nod genes (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 3 (1989), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Strains of Rhizobium leguminosarum biovar viciae specifically make an abundant protein (Rhi) in free-living culture but not in bacteroids. Genes needed for Rhi synthesis are on a Sym plasmid and here we show that one of these genes, rhiA, is the structural gene that specifies this polypeptide. Transcription of rhiA requires a regulatory gene, rhiR, located close to rhiA and to nod genes involved in nodulation. Mutations in rhiA or rhiR do not appear to affect symbiotic nitrogen fixation. Transcription of rhiA is repressed in cells grown in the presence of the flavanone hesperetin or the flavone apigenin, both of which are potent inducers of transcription of nod genes. This was deduced from the use of rhiA-lacZ fusions; however, when the Rhi polypeptide was detected in SDS gels, there was no apparent difference in the intensity of its staining in extracts obtained from cells grown with or without these flavanoid nod gene inducer molecules. However, a mutation in a nodulation gene, nolR, also closely linked to the nod and rhi genes, caused a severe depression in the amount of Rhi (as seen on gels) that was made in cells grown in the presence of inducer flavanoids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1989.tb00107.x
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  • 15
    Electronic Resource
    Electronic Resource
    Transcription of a Rhizobium ieguminosarum biovar phaseoli gene needed for melanin synthesis is activated by nifA of Rhizobium and Klebsiella pneumoniae (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 2 (1988), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The Rhizobium leguminosarum biovar phaseoli symbiotic plasmid pRP2JI carries a gene, melA, specifying the enzyme tyrosinase, which is responsible for the production of the pigment melanin in these bacteria. Transcription of melA is activated by the nifA gene of Rhizobium and, when the cloned melA gene is transferred to Escherichia coli, melA is expressed if the recipients contain nifA gene of Klebsiella pneumoniae. This nifA-dependent activation was temperature sensitive and required the ntrA gene. The cloned nifA gene of K. pneumoniae, when transferred to a nifA mutant of Rhizobium phaseoli biovar phaseoli, corrected the Mer− but not the Fix− phenotype. nifA of R. leguminosarum biovar phaseoli activated melA at higher levels in cells grown in low concentrations of oxygen. Also, nifA of fl. leguminosarum biovar phaseoli activated nifH of K. pneumoniae in Escherichia coli cells grown In low-oxygen concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1988.tb00036.x
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  • 16
    Electronic Resource
    Electronic Resource
    Single and multiple mutations affecting properties of the regulatory gene nodD of Rhizobium (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 3 (1989), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: nodD of Rhizobium leguminosarum has two regulatory properties: it autoregulates and, in cells grown with specific flavonoids, activates other nod genes. We isolated mutations in nodD affecting one or both properties. Those abolishing autoregulation and nod gene induction were at the 5′ end of nodD, as were those which only affected autoregulation. Mutations affecting nod gene activation are at the 3’end of nodD. Eleven mutations in this region of nodD were isolated: some had little effect on the regulatory properties; others reduced activation of other nod genes. 265 bps were removed from the 3’end of nodD: this abolished nodD function. Doubly mutant derivatives of nodD were constructed by making nodD genes with a mutation that conferred the ability to activate transcription of nod genes in the absence of inducers (class IV) plus another that abolished autoregulation and/or flavonoid-dependent nod gene activation. The behaviour of such double mutants was complex; e.g. in one case, a doubly mutant nodD gene containing the class IV mutation, coupled to one of those that (alone) abolished autoregulation and nod gene induction, was similar in behaviour to the wild type. In other cases, double mutants were similar to one of the parentals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1989.tb00142.x
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  • 17
    Electronic Resource
    Electronic Resource
    Comparison of the chemotactic behaviour of Rhizobium leguminosarum with and without the nodulation plasmid (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 2 (1988), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The chemotactic behaviour of a strain of Rhizobium leguminosarum biovar viciae was investigated. The flavanoids apigenin and naringenin, inducers of transcription of the nodulation (nod) genes, were both potent attractants but hesperitin, another flavone nod gene inducer, was not. The response of strains containing the Sym plasmid pRL1JI to apigenin and naringenin was significantly greater than the response of a strain cured of the plasmid, although both strains gave a positive response. Addition of the flavanol kaempferol, an antagonist of nod gene induction, had no detectable effect on the chemotactic response to naringenin or aplgenin, but was itself found to be an attractant. The attractant response to a variety of amino acids and sugars was not affected by the presence of the Sym plasmid. Homoserine, the most abundant nitrogenous compound in legume exudates, was also found to be an attractant. However, although the Sym plasmid is required for the biovar to metabolize homoserine as a carbon source, it was not required for the chemotactic response. A group of membrane proteins showed increased methylation in response to stimulation with serine. There was no measurable change in methylation after stimulation with apigenin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1988.tb00085.x
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  • 18
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    Unknown
    Daily Decreases in the Body Total and Stem Lengths of Normal Children (1943)
    Baltimore : Periodicals Archive Online (PAO)
    Human Biology. 15:1 (1943:Feb.) 65 
    Details
    ISSN: 0018-7143
    Topics: Biology
    URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:5243-1943-015-01-000005
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  • 19
    Electronic Resource
    Electronic Resource
    Geochemical aspects of some accumulation models for primary magmas (1986)
    Springer
    Contributions to mineralogy and petrology 93 (1986), S. 449-458 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The compositions of primary magmas depend to some degree on the dynamic processes occurring in the partially molten region of the mantle. The compositional dependence is estimated for three models which assume either accumulation from a migmatized source region or accumulation entirely by the interstitial flow of magma. Accumulation from a migmatised region results in magmas with higher concentrations of incompatible elements than does batch melting, whereas accumulation by interstitial flow results in magmas with lower concentrations of these elements. The concentrations of refractory elements are almost independent of both the accumulation process and the degree of partial melting and are therefore usefull for the identification of primary magmas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371715
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  • 20
    Electronic Resource
    Electronic Resource
    Interaction of granitic and basic magmas: experimental observations on contamination processes at 10 kbar with H2O (1988)
    Springer
    Contributions to mineralogy and petrology 98 (1988), S. 352-362 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Experiments designed to simulate the interaction of juxtaposed rhyolitic and basic magmas were conducted at 10 kbar with H2O, using reaction-couples consisting of Westerly granite (WG) against basalt (DW-1) and WG against a synthetic mafic glass (SMG, enriched in MgO and Na2O relative to DW-1). Each couple was run with ∼5 and ∼10 wt% H2O corresponding respectively to H2O-undersaturated and H2O-oversaturated conditions. Experiments were run for 42–44 h at 920° C, above the liquidus of WG and within the melting intervals of DW-1 and SMG. WG was run above the basic material in all but one experiment. The composition of the granitic melt was altered only through material exchange with the adjacent basic melts, whereas that of the basic melts also changed (relative to the bulk basic composition) due to partial crystallization. Some crystallization also occurred within the zone of interaction. For control, the basic compositions were also run alone under the same conditions as the reaction-couple experiments. The crystalline phase assemblages in the basic ends of the coupled experiments differed from those produced from the basic materials alone, demonstrating interaction with the granite melt. Moreover, compositional gradients within the basic ends of coupled experiments are indicated by changes in phase assemblage and compositions with distance from the interface with WG. Microprobe analyses of glass collected along the length of the capsules confirm published observations that alkali diffusion is very fast: K2O and Na2O homogenized throughout the capsules in less than the two-day run times. This, coupled with the fact that introduction of K2O into SMG stabilized biotite, produced the result that after interaction the bulk basic material (melt+crystals) contained more K2O than the coexisting felsic melt. Only very gentle gradients for CaO, FeO, and MgO are preserved in our experiments, in contrast with published anhydrous results, suggesting that the difference in activity coefficients for these components between basic and felsic melts is reduced by the introduction of H2O. Gradients for SiO2 and Al2O3 are of comparable length to those of the divalent cations, confirming earlier results that the diffusivities of the network-formers limit the rate of diffusion of Ca, Fe, and Mg.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00375185
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