Low nitrate uptake white clover genotype - Nitrogen relations of a low nitrate uptake inbred line of white clover (Trifolium repens L.)

Neil Raistrick, Terry P. T. Michaelson-Yeates, Michael T. Abberton, James H. Macduff

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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.
Original languageEnglish
Pages (from-to)191-204
Number of pages14
JournalPlant and Soil
Volume238
Issue number2
DOIs
Publication statusPublished - 2002

Keywords

  • genetic variation
  • inbred lines
  • nitrate uptake
  • nitrogen fixation
  • white clover

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