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  • 1
    Electronic Resource
    Electronic Resource
    Mechanism of nitrate uptake into Chara corallina cells: lack of evidence for obligatory coupling to proton pump and a new NO3−/NO3− exchange model (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 7 (1984), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Nitrate uptake into Chara corallina cells at different external pH (pHo) after different NO3− pretreatment conditions has been investigated. Following NO3− pretreatment (0.2 mol m−3 NO3−) there was little effect of pHo on subsequent net NO3− uptake into Chara cells. After N deprivation (2 mmol m−3 NO3−) there was a pronounced effect of pHo on nitrate uptake, the maximum rate occurring at pHo 4.7. There was no consistent relationship between OH− efflux and NO3− uptake in short term experiments (〈 1 h). NO3− efflux was also sensitive to pHo, the maximum rate occurring at ∼ pHo 5.0. An inhibitor of the proton pump, DES, immediately stimulated NO3− uptake into cells pretreated with NO3− and prevented the time-dependent decrease in NO3−, uptake into Chara cells that had been previously treated with low N (2 mmol m−3 NO3−). NO3− efflux was found to be very sensitive to DES with Ki= 0.7 mmol m−3. At the optimum pHo for NO3− uptake the effect of DES on membrane potential (ψm) were slight, and only apparent after 30 min. The results are interpreted in context of current models relating NO3− uptake and H+ pump activity. A new model for NO3− uptake is proposed which involves NO3−/NO3− exchange at steady state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11589779
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  • 2
    Electronic Resource
    Electronic Resource
    A multichannel microcomputer-based system for continuously measuring and recording ion activities of uptake solutions during ion absorption by roots of intact plants (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 6 (1983), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. A microcomputer-based system for the measurement of changes of ion activity (H+, NO3−, K+) in the uptake solutions during ion absorption by roots of intact plants is described. Ion activities are measured by means of ion-specific electrodes in a multichannel programmable voltmeter (data acquisition/control unit) which is activated by means of a microcomputer. Incoming data are stored digitally on tape cassettes or floppy discs via the microcomputer. The speed of sampling and large numbers of samples which can be simultaneously measured and recorded make this an extremely versatile system which might be employed for measuring and recording any number of analogue voltage signals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11587647
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  • 3
    Electronic Resource
    Electronic Resource
    Characteristics of nitrate uptake into seedlings of pea (Pisum sativum L. cv. Feltham First). Changes in net NO−3 uptake following inoculation with Rhizobium and growth in low nitrate concentrations (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 Nitrate uptake into intact pea seedlings (Pisum sativum L. cv. Feltham First) grown in hydroponic culture has been investigated. Following inoculation with Rhizobium leguminosarum a twofold increase in net nitrate uptake was observed. Changes in morphological characteristics following inoculation were found to decrease the effective area available for absorption.There was a two-fold decrease in net nitrate uptake into intact seedlings grown in the presence of N compared with N free media. In the former case net nitrate uptake appeared to stall at regular intervals. In both cases only the initial rates of nitrate uptake were found to be responsive to the external nitrate concentration. The results are discussed in terms of current models for the regulation of NO−3 uptake by higher plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1985.tb01687.x
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  • 4
    Electronic Resource
    Electronic Resource
    A novel technique for identification of sites of anion transport in intact cells and tissues using a fluorescent probe (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 10 (1987), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract The purported blocker of anion transport 4, 4′ di-isothiocyano-2-2′ stilbene disulfonate (DIDS) has been shown to partially inhibit 36Cl− influx, 36CIO−3 influx and 35SO2−4 influx into Pisum salivum L. cv. Feltham First seedlings. This inhibitory effect could be prevented by pretreatment with the respective unlabelled medium. There was no effect of DIDS on 14C methylamine influx. The results are consistent with the hypothesis that the binding of DIDS to the site of anion-carrier interaction is responsible for its observed inhibitory effects on anion fluxes. The fluorescent properties of DIDS upon binding to membrane proteins was exploited in an attempt to examine the major sites of anion pumping in whole roots. The results show clearly that in the presence of DIDS the epidermal layers became brightly fluorescent, while cortical layers did not fiuoresce. Lycopersicum esculentum cells taken from locular fluid were plasmolysed using sucrose solution, and the patterns of fluorescence in the presence of DIDS showed in an unambiguous way that the fluorescence is associated with cell membranes. The potential usefulness of this technique to probe sites of anion transport in whole plants and tissues is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11602249
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  • 5
    Electronic Resource
    Electronic Resource
    A comparison of regulatory effects of chloride on nitrate uptake, and of nitrate on chloride uptake into Pisum sativum seedlings (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 66 (1986), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Net nitrate uptake, 36ClO−3/NO−3 influx and 36Cl− influx into Pisum sativum L. cv. Feltham First seedlings have been examined following growth in culture medium containing different combinations of chloride and nitrate. When young (6 days old) seedlings, that had been grown in the absence of N were used, nitrate accumulation stimulated net nitrate uptake and 36ClO−3/NO−3 influx (r2= 0.99) while chloride accumulation inhibited nitrate uptake and 36ClO−3/NO−3 influx (r2= 0.65). When nitrate was provided during growth there was no effect of chloride pretreatment on net nitrate uptake and there was little effect of total [NO−3+ Cl−]i on 36ClO−3/NO−3 influx (r2= 0.26). A direct effect of Cl− on 36ClO−3/NO−3 influx was only found when seedlings had been starved of N for more prolonged periods (14 days).When moderate chloride was supplied during growth, 36Cl− influx was insensitive to nitrate or chloride accumulated, but significantly correlated with loge [NO−3+ Cl−]i (r2= 0.75). When trace amounts of Cl− were supplied during growth 36Cl− influx was inhibited by (a) NO−3 in the external medium and (b) Cl− pretreatment, but was insensitive to NO−3 pretreatment. The sensitivity of 36Cl− influx to external nitrate was not found following Cl− pretreatment in the absence of nitrate. The possibility that there are two populations of chloride carriers which differ in their sensitivity to external nitrate is discussed. Tentative schematic models to account for the regulation of nitrate and chloride uptake are proposed in the context of current hypotheses for regulation of ion transport and control systems theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1986.tb01242.x
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  • 6
    Electronic Resource
    Electronic Resource
    The effect of differential root and shoot temperature on the nitrate reductase activity, assayed in vivo and in vitro in roots ofHordeum vulgare (barley) (1980)
    Springer
    Planta 148 (1980), S. 455-461 
    Details
    ISSN: 1432-2048
    Keywords: Carbohydrates (in roots) ; Hordeum ; Malate ; Nitrate reductase activity ; Temperature (and nitrate reductase activity)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract There was a large increase in nitrate reductase activity (NAR) assayed both in vivo and in vitro in roots of barley plants (cv. Midas_ grown with roots at 10°C and shoots at 20°C, compared with whole plants grown at 20°C. There were diurnal fluctuations in NRA in roots from both treatments, but they were much greater in roots grown at 20°C, where NRA fell to a very low value in the dark period. The diurnal fluctuations in the malate content of the roots were also related to the root growth temperature. Plants with roots grown at the lower temperature had a higher malate content, especially in the dark period where it was 20 times greater than in plants with roots at 20°C. At all times there was a three-fold increase in soluble carbohydrate in cooled roots and diurnal fluctuations were much less pronounced than those of malate. Growth at low temperatures increased the total flux of amino N into the xylem sap and increased the proportion of reduced N in the total N flux. At certain times of day both 10°C- and 20°C-grown roots responded to exogeneous malate by increasing the flux of amino acid into the xylem sap, although this effect was always more pronounced in 20°C-grown roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02395315
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  • 7
    Electronic Resource
    Electronic Resource
    The effect of differential root and shoot temperature on the nitrate reductase activity, assayed in vivo and in vitro in roots ofHordeum vulgare (barley) (1980)
    Springer
    Planta 148 (1980), S. 455-461 
    Details
    ISSN: 1432-2048
    Keywords: Carbohydrates (in roots) ; Hordeum ; Malate ; Nitrate reductase activity ; Temperature (and nitrate reductase activity)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract There was a large increase in nitrate reductase activity (NAR) assayed both in vivo and in vitro in roots of barley plants (cv. Midas_ grown with roots at 10°C and shoots at 20°C, compared with whole plants grown at 20°C. There were diurnal fluctuations in NRA in roots from both treatments, but they were much greater in roots grown at 20°C, where NRA fell to a very low value in the dark period. The diurnal fluctuations in the malate content of the roots were also related to the root growth temperature. Plants with roots grown at the lower temperature had a higher malate content, especially in the dark period where it was 20 times greater than in plants with roots at 20°C. At all times there was a three-fold increase in soluble carbohydrate in cooled roots and diurnal fluctuations were much less pronounced than those of malate. Growth at low temperatures increased the total flux of amino N into the xylem sap and increased the proportion of reduced N in the total N flux. At certain times of day both 10°C- and 20°C-grown roots responded to exogeneous malate by increasing the flux of amino acid into the xylem sap, although this effect was always more pronounced in 20°C-grown roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00552660
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  • 8
    Electronic Resource
    Electronic Resource
    A substrate cycling model for nitrate uptake byPisum sativum seedlings: A key to sensitivity of response of net flux to substrate and effectors? (1986)
    Springer
    Plant and soil 91 (1986), S. 307-311 
    Details
    ISSN: 1573-5036
    Keywords: Nitrate-efflux ; Nitrate-influx ; Pisum sativum L ; Substrate-cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Net nitrate uptake (J) intoPisum sativum L. seedlings has been investigated. J was high initially, but declined with time as NO 3 − efflux (E) approached that of NO 3 − influx (I). Both I and E were higher in plants which had been grown without N. J could be reversibly and immediately inhibited by 5 mmol m−3 NH 4 + , although plants grown in the presence of nitrate were less sensitive. A theoretical model which involves substrate cycling across the plasmalemma is shown to increase the sensitivity to substrate and effectors. It predicts that during growth of Pisum in N free media the cycling rate (E/I) is increased and the sensitivity of net flux of inhibition by NH 4 + is highest. The model also provides a means for control of cytoplasmic nitrate pool size [NO 3 − ] c.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02198113
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  • 9
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    The effect of differential root and shoot temperature on the nitrate reductase activity, assayed in vivo and in vitro in roots ofHordeum vulgare (barley) (1980)
    Springer
    Details
    Publication Date: 1980-06-01
    Print ISSN: 0032-0935
    Electronic ISSN: 1432-2048
    Topics: Biology
    Published by Springer
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  • 10
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    A substrate cycling model for nitrate uptake byPisum sativum seedlings: A key to sensitivity of response of net flux to substrate and effectors? (1986)
    Springer
    Details
    Publication Date: 1986-10-01
    Print ISSN: 0032-079X
    Electronic ISSN: 1573-5036
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Springer
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