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 language | English |
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Pages (from-to) | 191-204 |
Number of pages | 14 |
Journal | Plant and Soil |
Volume | 238 |
Issue number | 2 |
DOIs | |
Publication status | Published - 2002 |
Keywords
- genetic variation
- inbred lines
- nitrate uptake
- nitrogen fixation
- white clover