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Aluminium toxicity expression on nutrient uptake, growth and root morphology of Trifolium repens L. cv. 'Grasslands Huia'

J. LEE and M. W. PRITCHARD
Plant and Soil
Vol. 82, No. 1 (1984), pp. 101-116
Published by: Springer
Stable URL: http://www.jstor.org/stable/42935547
Page Count: 16
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Aluminium toxicity expression on nutrient uptake, growth and root morphology of Trifolium repens L. cv. 'Grasslands Huia'
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Abstract

Hydroponic experiments were undertaken to examine the effect of increasing aluminium levels on the mineral nutrition and root morphology of T. repens growing in nutrient solution. Toxicity symptoms appear between 27.8 and 47.5 µM Al³⁺ activity (148 to 297 µM total aluminium). The threshold level corresponding to a 10% reduction in leaf fresh weight is estimated to be approximately 20 µM Al³⁺ activity. The concentration of aluminium in the leaves of white clover increases exponentially with aluminium activity in the nutrient solution. The uptake of divalent cations was inhibited but aluminium enhanced potassium and nitrogen concentrations in both leaves and roots. At high pH (pH 6.0) the speciation of aluminium is controlled by the formation of solid aluminium phosphate and aluminium hydroxide except at the lowest aluminium level (37 µM) where 99.9 per cent is present as the DTPA complex. As the concentration of total aluminium increases, the percentage of Al-DTPA and soluble aluminium hydroxide decreases whilst solid A1(OH)₃ increases rapidly to reach a maximum of 91.6 percent (of the total aluminium) in the 1180 µM aluminium treatment. At pH 4.5 the dominant forms of aluminium are free aluminium ion Al-DTPA,$ALSO_4^ + $and AlOH²⁺. The roots of aluminium stressed plants showed symptoms typical of alminium toxicity.

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