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  • Al3+  (1)
  • Calcium uptake  (1)
  • Springer  (2)
  • 1990-1994  (2)
  • 1920-1924
  • 1905-1909
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  • Springer  (2)
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  • 1990-1994  (2)
  • 1920-1924
  • 1905-1909
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Planta 192 (1993), S. 98-103 
    ISSN: 1432-2048
    Keywords: Aluminum toxicity ; Calcium uptake ; Growth inhibition ; Root ; Triticum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cation Al3+ is toxic to plants at micromolar concentrations and can severely inhibit root growth in solution experiments. Trivalent aluminum hydrolyzes in solution, and, apart from the Al3+ ion, which dominates speciation below pH 5.0, various mononuclear and polynuclear hydroxy-Al species can also occur (Kinraide 1991). Accumulating evidence suggests that Al3+ is the rhizotoxic species under the experimental conditions used in the present study (Kinraide 1991; Kinraide et al. 1992). The inhibition of Ca2+ uptake in roots by Al3+ has been proposed as a possible mechanism for Al3+ toxicity, and in this study the hypothesis was tested directly. Root growth and Ca2+ uptake were measured in 5-d-old seedlings of wheat (Triticum aestivum L. Thell) during exposure to Al3+ in a low-Ca2+ basal medium, and to Al3+ in the presence of added cations. Uptake of Ca2+ in whole roots and translocation to the shoot were measured using 45Ca2+, and localized measurements of net Ca2+ flux were also made at the root apex using the technique of microelectrode ion-flux estimation. Treatment with 2.64 μM AlCl3 in 226 μM CaCl2, at pH 4.5, severely inhibited root growth without affecting Ca2+ uptake. Addition of 30 mM Na2+, 3 mM Mg2+ or 50 μM tris(ethylenediamine)cobalt(III) to this Al3+ treatment restored root growth but significantly reduced Ca2+ uptake measured over the entire root system and at the root apex. The Al3+ and Ca2+ concentrations were adjusted so that the activities of the Al3+ and Ca2+ ions were constant in all solutions (1.5 μM and 200 μM, respectively). Root growth can be severely inhibited by Al3+ concentrations that do not affect Ca2+ uptake, while the addition of ameliorating cations depresses Ca2+ uptake. These results argue against the hypothesis that Al3+ inhibits root growth by reducing Ca2+ uptake.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 134 (1991), S. 167-178 
    ISSN: 1573-5036
    Keywords: Al3+ ; aluminium ; hydroxy-aluminium ; phytotoxicity ; polynuclear aluminium ; rhizotoxicity ; roots ; toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The aluminium (III) released from soil minerals to the soil solution under acid conditions may appear as hexaaquaaluminium (Al(H2O)6 3+, or Al3+ for convenience) or may react with available ligands to form additional chemical species. That one or more of these species is rhizotoxic (inhibitory to root elongation) has been known for many decades, but the identity of the toxic species remains problematical for the following reasons. 1. Several Al species coexist in solution so individual species cannot be investigated in isolation, even in artificial culture media. 2. The activities of individual species must be calculated from equilibrium data that may be uncertain. 3. The unexpected or undetected appearance of the extremely toxic triskaidekaaluminium (AlO4Al12(OH)24(H2O)12 7+ or Al13) may cause misatribution of toxicity to other species, especially to mononuclear hydroxy-Al. 4. If H+ ameliorates Al3+ toxicity, or vice versa, then mononuclear hydroxy-Al may appear to be toxic when it is not. 5. The identity and activities of the Al species contacting the cell surfaces are uncertain because of the H+ currents through the root surface and because of surface charges. This article considers the implications of these problems for good experimental designs and critically evaluates current information regarding the relative toxicities of selected Al species. It is concluded that polycationic Al (charge 〉2) is rhizotoxic as are other polyvalent cations.
    Type of Medium: Electronic Resource
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