Plant nitrogen (N) nutrition is a topic that challenges the re- searcher with a number of problems not encountered in other areas of plant mineral nutrition research.The diversity of N forms present in the soil, their interconversions, their different chemical and physical characteristics and not the least the multi- tude of adaptations and acclimatisations that plants display to optimize acquisition of various N forms all contribute to the complexity of plant N nutrition.
Thus, plants can use a wide array of chemical N forms, ranging from the simple inorganic N compounds such as NH4+ and NO3- as well as polymeric N forms such as proteins. My research deals with plant N physio- logy, particularly N acquisition and metabolism of forest plants. This research spans from detailed studies of uptake processes to forest fertilization and environmental effects of N.
|Tests with arginine based fertilizer in a seedling nursery Rotorua, New Zeeland.||Selection on D-amino acids.|
We have studied uptake of various N forms and demonstrated how field-grown plants acquire different organic N compounds. These studies have stimulated us to characterize the molecular mechanisms underpinning plant organic N nutrition, specifically the specific transporters mediating uptake of various amino acids as well as metabolism of absorbed organic compounds.
We have discovered that plants have a well-developed capacity for using the common L-enantiomers of amino acids but a very restricted capacity to metabolise their D-counterparts.We have also shown how transgenic plants expressing genes encoding D-amino acid metabolising enzymes can detoxify and grow on D-amino acids.This finding has formed the basis for the deve- lopment of a new selectable marker in plant biotechnology, now commercialized under the tradename SELDA. Basic L-amino acids, and in particular L-arginine, are absorbed at high rates by many plants and we have shown that such N forms have spe- cific advantages for cultivation of woody plants such as conifer seedlings.
This finding forms the basis for the development of a new fertilizer – arGrow®, which is now commercialized by the company SweTree Technologies.
- Näsholm, T., Kielland, K. & Ganeteg, U. (2009). Uptake of organic nitrogen by plants. Tansley Review New Phytologist, 182: 31- 48.
- Svennerstam, H., Ganeteg, U., Bellini, C. & Näsholm, T. (2007). Comprehensive screening of Arabidopsis mutants suggests the Lysine Histidine Tranporter 1 to be involved in root uptake of amino acids. Plant Physiology 143: 1-8
- Erikson, O., Hertzberg, M. & Näsholm, T. (2004). A conditional marker gene allowing both positive and negative selection in plants. Nature Biotechnology, 22: 455-458.
- Lipson, D. and Näsholm, T. (2001). The unexpected versatility of plants: Organic Nitrogen Use and Availability in Terrestrial Ecosystems. Commissioned review. Oecologia 128: 305-316
- Näsholm, T., Ekblad, A., Nordin, A., Giesler, R., Högberg, M. and Högberg, P. (1998). Boreal forest plants take up organic nitrogen. Nature 392, 914-916, 1998.