Soil and Land Systems

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https://hdl.handle.net/2440/12036
The Soil and Land Systems discipline was part of the School of Earth and Environmental Sciences until 2013. Since then Soil Science has become part of the School of Agriculture, Food and Wine.

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Browsing Soil and Land Systems by Author "Ayling, S."

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    Arbuscular mycorrhizas formed by Asphodelus fistulosus and Glomus coronatum: three-dimensional analysis of plant nuclear shift using laser scanning confocal microscopy
    (Springer Verlag, 2001) Cavagnaro, T.; Smith, F.; Kolesik, P.; Ayling, S.; Smith, S.
    Two main morphological types of arbuscular mycorrhizas (AM) are recognised, the Arum-type and the Paris-type. Most research has focused on the Arum-type, including studies of the influence of colonisation on the plant at the cellular level. Modifications in the size, position and shape of plant nuclei in colonised and uncolonised cells of the Paris-type AM formed by Asphodelus fistulosus L. inoculated with Glomus coronatum Giovannetti were investigated in this study. The plants were grown in nurse pots to achieve near synchronous colonisation. Laser scanning confocal microscopy (LSCM) was used to visualise root material and to quantify plant nuclear shift in three dimensions, which has not been achieved in the past. In each colonised cell containing arbusculate coils there was a quantifiable increase in the distance from the centre of the nucleus to the closest cell wall and in the volume of the plant nucleus. Similar effects occurred in cells with hyphal coils but were not quantifiable because of small numbers. The position and size of the nucleus did not change in uncolonised cells of either inoculated or uninoculated plants. The significance of the results is discussed with respect to the development of Paris-type AM.
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    Changes in the wall potential of Scutellospora calospora associated with colonization of Allium porrum roots are not accompanied by equivalent changes in the host
    (Canadian Science Publishing, 1998) Ayling, S.; Smith, S.; Reid, R.; Smith, F.
    Cell wall electrical potentials were recorded from external hyphae, appressoria, and associated hyphae of the vesicular-arbuscular (VA) mycorrhizal fungus Scutellospora calospora (Nicolson & Gerdemann) Walker & Sanders colonizing leek (Allium porrum L.) roots. As colonization progressed the hyphal walls became more polarized with similar values to the walls of the leek root. These changes, which may reflect changes in fungal wall composition, have important implications for nutrient uptake by the fungus. There were no differences in wall or intracellular potentials between leek roots colonized by either S. calospora orGlomus sp. ("City Beach") and non-mycorrhizal roots. These results are further evidence of the close compatibility between roots and VA mycorrhizal fungi. Key words: vesicular-arbuscular mycorrhiza, cell wall, electrical potential difference, leek, Allium porrum, Scutellospora calospora.
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    Colonisation by arbuscular mycorrhizal fungi changes the relationship between phosphorus uptake and membrane potential in leek (Allium porrum) seedlings
    (CSIRO Publishing, 2001) Ayling, S.; Smith, S.; Smith, F.
    The effect of colonisation by arbuscular mycorrhizal (AM) fungi on the relationship between phosphorus (P) uptake and root membrane electric potential difference (p.d.) was investigated in leek (Allium porrum L.). Plants were grown, with or without the AM fungus Scutellospora calospora (Nicolson and Gerdemann) Walker and Sanders, in soil. P uptake and root p.d. were correlated; plants with the highest P concentration in the shoot had the most negative p.d. This relationship was strong in non-mycorrhizal leeks (r² = 84–98%), but weaker in mycorrhizal leeks (r² = 55–64%), consistent with the idea that in mycorrhizal roots the fungal hyphae are the principal site of P uptake.
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    Transmembrane electric potential difference of germ tubes of arbuscular mycorrhizal fungi responds to external stimuli
    (Blackwell Publishing Ltd, 2000) Ayling, S.; Smith, S.; Smith, F.
    Measurements of the electric potential difference across the hyphal wall and the cell membrane were made on external hyphae of three species of arbuscular mycorrhizal fungus Gigaspora margarita, Scutellospora calospora and Glomus coronatum and on germ tubes of Gi. margarita. The values of transmembrane electric potential difference recorded (∼–40 mV) are less negative than those previously reported from hyphae of arbuscular mycorrhizal fungi closely associated with roots and from filamentous fungi. The external hyphae of arbuscular mycorrhizal fungi grown in soil had similar values of electric potential difference to those grown in soil-less culture, and to germ tubes. Thermodynamic calculations showed that despite these low values of electric potential difference, efficient high-affinity uptake of phosphate is possible. The transmembrane electric potential difference of germ tubes of Gi. margarita became more negative when plant root extract was added to the medium, showing for the first time that the early stages of interaction between plant and fungus occur via direct effects on the plasma membrane rather than via effects on gene expression. Addition of K⁺ reversibly depolarized the transmembrane electric potential difference of germ tubes of Gi. margarita, indicating that despite the low electric potential difference the fungus has control over the permeability of the plasmamembrane to K⁺.