Nitrate, Potassium and Phosphate in Plants


The kinetics of the uptake of nitrate, ammonium, potassium and phosphate by plant roots are described. The uptake mechanisms are equated to the very recent isolation and characterization of genes encoding specific membrane‐bound transporter proteins.

Keywords: genes; high affinity; ion channels; low affinity; transporters

Figure 1.

Comparative concentration dependence of influx (blue symbols) and influx (red symbols) in roots of intact white spruce seedlings at a range of environmentally relevant nitrogen concentrations. (Reproduced from Kronzucker et al., .)

Figure 2.

(a) The uptake of phosphate by yeast mutant NS219 complemented with vector containing the gene (GvPT) encoding the membrane phosphate transporter of Glomus versiforme. Direct linear plot shows intersection points (lines omitted for clarity); arrows from the median point give estimations of Km (18 μmol L−1) and Vmax (1.96 nmol min−1). (b) Phosphate uptake rate as a function of phosphate concentration. (Reproduced from Harrison and van Buuren, .)


Further Reading

Bei Q and Luan S (1998) Functional expression and characterization of a K+ channel gene in a plant cell model. The Plant Journal 13: 857–865.

Harrison MJ and van Buuren ML (1995) A phosphate transporter from the mycorrhizal fungus Glomus versiforme. Nature 378: 626–629.

Huang N‐C, Chiang C‐S, Crawford NM and Tsay YF (1996) CHL1 encodes a component of the low affinity nitrate uptake system in Arabidopsis and shows cell type‐specific expression in roots. The Plant Cell 8: 2183–2191.

Kim EJ, Kwak JM, Uozumi N and Schroeder JI (1998) AtKUP1: An Arabidopsis gene encoding high‐affinity potassium transport activity. The Plant Cell 10: 51–62.

Kronzucker HJ, Siddiqi MY and Glass ADM (1997) Conifer root discrimination against soil nitrate and the ecology of forest succession. Nature 385: 59–61.

Maathius FJM and Sanders D (1996) Mechanisms of potassium absorption by higher plant roots. Physiologia Plantarum 96: 158–168.

Marshner H (1995) Mineral Nutrition of Higher Plants. London: Academic Press.

Mitsukawa N, Okumura S, Shirano Y et al. (1997) Overexpression of an Arabidopsis thaliana high‐affinity phosphate transporter gene in tobacco cultured cells, enhances cell growth under phosphate‐limited conditions. Proceedings of the National Academy of Sciences of the USA 94: 7098–7102.

Schachtman DP, Reid RJ and Ayling SM (1998) Phosphorus uptake by plants: from soil to cell. Plant Physiology 116: 447–453.

Trueman LJ, Richardson A and Forde BG (1996) Molecular cloning of higher plant homologs of the high affinity nitrate transporters of Chlamydomonas reinhardtii and Aspergillus nidulans. Gene 175: 223.

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Lea, Peter J(Apr 2001) Nitrate, Potassium and Phosphate in Plants. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0001308]