1 Acknowledgements ............................................. 4
2 Abbreviations ................................................ 4
3 General introduction ......................................... 5
4 Nitrogen assimilation by higher plants ....................... 6
4.1 Nitrate uptake .......................................... 6
4.1.1 Location of nitrate uptake ....................... 6
4.1.2 The concept of a nitrate "carrier" ............... 7
4.1.3 Induction ........................................ 7
4.1.4 Kinetics ......................................... 7
4.1.5 Influx/efflux .................................... 8
4.1.6 Mechanism of nitrate uptake ..................... 10
4.2 Nitrate reduction ...................................... 10
4.3 Nitrite reduction ...................................... 11
4.4 Ammonium assimilation .................................. 12
4.5 Translocation of nitrogen .............................. 12
5 Nitrogen nutrition and growth ............................... 13
6 Results and Discussion. Survey of Papers I-V ................ 14
6.1 Aims of this investigation ............................. 14
6.2 Plant species and culture .............................. 15
6.3 Growth ................................................. 16
6.4 Tissue nitrogen concentrations and growth .............. 17
6.5 Nitrate uptake ......................................... 18
6.5.1 Induction and daily patterns of uptake .......... 18
6.5.2 Influx/efflux ................................... 18
6.5.3 Kinetics ........................................ 19
6.5.4 Kinetics in relation to nitrogen and growth ..... 22
6.6 Cytoplasmic nitrate concentrations ..................... 23
6.7 Nitrate reduction ...................................... 24
6.8 Ammonium assimilation .................................. 25
6.9 Translocation of nitrate and amino acids ............... 26
7 Conclusions: Regulation of nitrate acquisition .............. 26
8 References .................................................. 27
Appendices:
Paper I ..................................................... 37
Paper II .................................................... 49
Paper III ................................................... 57
Paper IV .................................................... 65
Paper V ..................................................... 79
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