Nitrogen relations of a low nitrate uptake inbred line of white clover (Trifolium repens L.) |
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Authors: | Macduff JH Abberton MT Raistrick N Michaelson-Yeates TPT |
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Institution: | (1) Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth, Ceredigion, SY 23 3EB, UK |
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Abstract: | The nitrogen relations of an inbred line of white clover (Trifolium repens L.) thought to exhibit an abnormally low capacity for NO3
– uptake (line LNU) were compared with a line regarded as normal with respect to NO3
– uptake (line NNU). Growth, nodulation, N2 fixation and NO3
– uptake were measured over 7 weeks in flowing solution culture (Experiment 1) by plants dependent for N acquisition on either (i) NO3
– uptake, (ii) NO3
– uptake +N2 fixation, or (iii) N2 fixation only. Effects of plant N status on the short-term uptake and translocation of 15NH4
+ and 15NO3
– were also investigated (Experiment 2). Nitrate uptake per plant by –fix/+NO3
– line LNU was 50% of uptake by line NNU over 35 days, and there were significant differences in specific uptake rates of NO3
– between the lines over the first 24 days. The `low NO3
– uptake' phenotype was indistinct under +fix/+NO3
– treatment. Nitrate lowered specific rates of nitrogen fixation by line NNU but had no effect on line LNU. Only low N status line LNU plants had lower short-term rates of NH4
+ and NO3
– uptake than line NNU. It is concluded that the `low NO3
– uptake' phenotype of line LNU is inconsistently expressed. Circumstantial evidence points to increased NO3
– efflux and decreased xylem translocation of NO3
– as possible explanations for the lower NO3
– uptake by line LNU. |
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Keywords: | genetic variation inbred lines nitrate uptake nitrogen fixation white clover |
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