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  • 1990-1994  (3)
  • 1975-1979  (6)
Materialart
Erscheinungszeitraum
Jahr
  • 1
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 15 (1992), S. 0 
    ISSN: 1365-3040
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Lolium perenne L. cv. 23 (perennial ryegrass) plants were grown in flowing solution culture and acclimatized over 49 d to low root temperature (5°C) prior to treatment at root temperatures of 3, 5, 7 and 9°C for 41 d with common air temperature of 20/15°C day/night and solution pH 5·0. The effects of root temperature on growth, uptake and assimilation of N were compared with N supplied as either NH4 or NO3 at 10 mmol m−3. At any given temperature, the relative growth rate (RGR) of roots exceeded that of shoots, thus the root fraction (Rf) increased with time. These effects were found in plants grown with the two N sources. Plants grown at 3 and 5°C had very high dry matter contents as reflected by the fresh weight: freeze-dried weight ratio. This ratio increased sharply, especially in roots at 7 and 9°C. Expressed on a fresh weight basis, there was no major effect of root temperature on the [N] of plants receiving NHJ but at any given temperature, the [N] in plants grown with NHJ was significantly greater than in those grown with NO3. The specific absorption rate (SAR) of NH+4 was greater at all temperatures than SAR-NO3. In plants grown with NH+, 3–5% of the total N was recovered as NH+4, whereas in those grown with NO−3 the unassimilated NO−3 rose sharply between 7 and 9°C to become 14 and 28% of the total N in shoots and roots, respectively. The greater assimilation of NH+4 lead to concentrations of insoluble reduced N (= protein) which were 125 and 20% greater, in roots and shoots, respectively, than in NO−3-grown plants. Plants grown with NH+4 had very much greater glutamine and asparagine concentrations in both roots and shoots, although other amino acids were more similar in Concentration to those in NO−3 grown plants. It is concluded that slow growth at low root temperature is not caused by restriction of the absorption or assimilation of either NH+4 or NO−3. The additional residual N (protein) in NH+4 grown plants may serve as a labile store of N which could support growth when external N supply becomes deficient.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1399-3054
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: 15N-Nitrate and 35S-sulphate labelling experiments were performed with spring wheat (Triticum aestivum L. cv. Timmo) 44. 64, 79, 95 and 115 days after sowing (growth stages arbitrarily denoted I to V). Label was fed to the plants via a fraction of the root system, termed “donor root”, whereas the rest of the root (“receiver root”) was fed non-labelled nutrient solution. Net uptake rates for both nitrate and sulphate per unit root weight changed little from growth stage I to IV, but were considerably lower at stage V. On a whole-plant weight basis, uptake declined from stage I to IV, because root contribution to total plant weight declined. Between 80 and 95% of absorbed label was translocated to the shoot at all growth stages. At stage V, up to 30% of absorbed label was recovered in the ears. Labelling of the receiver root indicated that, at all growth stages, 10 to 17% of N and 12 to 32% of S translocated to the shoot was retranslocated to the root. This corresponds to between 35 and 85% of the label actually recovered in the roots. Analysis of 15N-labelling of xylem sap collected from receiver roots at growth stages I to IV indicated that about half of the reduced N in the sap is derived from cycling through roots of recently assimilated N. Evidence of cycling was also obtained at stage V. Labelled sulphate was the only form of S cycled in the plant, but it accounted for only 1 to 7% of the sulphate in the xylem sap.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Planta 128 (1976), S. 267-269 
    ISSN: 1432-2048
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The patterns of uptake and translocation of magnesium in different regions of the root are very similar to those of calcium. Once the endodermis has become suberized translocation of either ion to the shoot is greatly reduced and it is concluded that magnesium, like calcium, appears to move across the root cortex largely in the free space.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    ISSN: 1432-2048
    Schlagwort(e): Hordeum ; Phosphate ; Root transport
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Plants of Hordeum vulgare (barley) were grown initially in a solution containing 150 μM phosphate and then transferred on day 6 to solutions with (+P) and without (-P) phosphate supplied. After various times plants from these treatments were supplied with labelled phosphate. Analysis of plant growth and rates of labelled phosphate uptake showed that a general enhancement of uptake and translocation was found, in plants which had been in the-P solution, several days before the rate of dry matter accumulation was affected. Subsequently a detailed analysis of phosphate uptake by segments of intact root axes showed that the enhancement of phosphate uptake by P-stress occurred first in the old and mature parts of the seminal root axis and last in the young zones 1 cm from the root apex. During this transition period there were profound changes in the pattern of P absorption along the length of the root. Most of the additional P absorbed in response to P-stress was translocated to the shoot, particularly in older zones of the axis. Enhancement of phosphate uptake in young zones of nodal axes occurred at an earlier stage than in seminal axes. The results are related to the P-status of shoots and root zones and discussed in relation to the general control by the shoot of phosphate transport in the root.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    ISSN: 1432-2048
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Roots of intact plants of rye and barley which had been growing at 20° were cooled for 12–72 h at 8–14° C while the shoots were kept at 20°. The roots were then excised and placed in solutions at temperatures ranging from 2.5–22.5° C. The rate of exudation of xylem sap and the chemical composition and osmotic potential of the sap were measured and compared with controls which had been kept at 20° C during the pretreatment period. Pre-cooling increased the fluxes of K+, Ca2+ and H2PO 4 - into the xylem sap of both species by factors of two to three; the total volume of exudate rose by larger factors. Thus the concentrations of these ions were lower in the sap exuding from cooled roots than in that from controls. Measurements of the osmotic potential of the sap from barley roots indicated that the osmotic driving force in cooled and control roots was similar even though flow in the former was much greater. The enhancement of exudation was shown to be dependent on the duration and the temperature experienced by the roots during pretreatment, and was lost rapidly when roots of intact plants were returned to 20°. Analysis of the temperature coefficients for exudation and Arrhenius plots revealed very distinct changes in the activation energy for exudation above and below a transition temperature. In control plants of barley and rye this temperature was around 10° C, but in cooled roots of rye there was a significant shift in the transition temperature to 5° C. Activation energies for exudation of control and cooled roots above or below the transition temperature were broadly similar, thus pre-cooling roots did not alter the temperature sensitivity of exudation but merely its rate at a given temperature. The results are discussed in relation to active ion transport, membrane fluidity and the resistance of the root to water flow.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 155-156 (1993), S. 139-142 
    ISSN: 1573-5036
    Schlagwort(e): nutrient transport ; ion transport ; permeases ; ion channels ; heterologous expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract A number of strategies for identifying and cloning genes involved in nutrient transport and assimilation processes are discussed. Particular attention is paid to phenotypic screening by heterologous complementation of mutations which affect transport processes in other organisms and use of insertion elements in plant genomes. A program in which complementation of yeast mutants is being used to clone genes involved in the uptake and assimilation of sulphate by plants is outlined. Information is provided on the isolation of yeast mutants and their characterization, choice of appropriate shuttle vectors, the construction of cDNA and genomic libraries, and screening of libraries for complementation.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 50 (1978), S. 723-725 
    ISSN: 1573-5036
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Incidence in the field of crop disorders known to be due to localised calcium deficiency bears little relation to soil calcium status, and is more often associated with particular types of weather. We are suggesting that brief periods of soil partial anaerobiosis following wet weather, and other unfavourable soil physical conditions such as compaction, lead to a temporary reduction in the distal, undifferentiated region of roots from which the majority of the calcium taken up is transported to the shoot. This might lead to a transient calcium deficiency in rapidly growing shoot tissues, and thence to necrosis.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 50 (1978), S. 723-725 
    ISSN: 1573-5036
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Incidence in the field of crop disorders known to be due to localised calcium deficiency bears little relation to soil calcium status, and is more often associated with particular types of weather. We are suggesting that brief periods of soil partial anaerobiosis following wet weather, and other unfavourable soil physical conditions such as compaction, lead to a temporary reduction in the distal, undifferentiated region of roots from which the majority of the calcium taken up is transported to the shoot. This might lead to a transient calcium deficiency in rapidly growing shoot tissues, and thence to necrosis.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Protoplasma 101 (1979), S. 331-347 
    ISSN: 1615-6102
    Schlagwort(e): Carex arenaria ; Epidermis ; Hypodermis ; Permeability ; Roots
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary During the normal course of development in the root of sand sedge (Carex arenaria), many of the cells in the central cortex degenerate to form an extensive aerenchyma. The epidermis and multi-layered hypodermis become heavily suberized and only remain attached to the stele by a few, thin, radial files of cortical cells that have not autolyzed. These changes make it possible for epidermal/hypodermal sleeves to be isolated so that their permeability can be determined. The coefficient of diffusive permeability for tritiated water is of the order of 20 nm s−1, while the permeability coefficient for self diffusion of labelled phosphate and calcium is approximately 5.0 and 4.0 nm s−1 respectively. These values are approximately 200 (water) and 500 (phosphate and calcium) times lower than similar determinations made on isolated sleeves of onion roots. The outer layers of the mature root ofC. arenaria are thus extremely impermeable: any significant absorptive function has been lost at the expense of a protective role provided by the modified cortex for the vascular stele.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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