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.

Torgny Nasholm 1150Thus, 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.

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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.
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Publications list

  1. Interplay between N-form and N-dose influences ecosystem effects of N addition to boreal forest
    PLANT AND SOIL 2018, 423 (1-2):385-395
  2. Improving in situ recovery of soil nitrogen using the microdialysis technique
    SOIL BIOLOGY & BIOCHEMISTRY 2017, 114:93-103
  3. Incorporating mass flow strongly promotes N flux rates in boreal forest soils
    SOIL BIOLOGY & BIOCHEMISTRY 2017, 114:263-269
  4. Amino acid transporter mutants of Arabidopsis provides evidence that a non-mycorrhizal plant acquires organic nitrogen from agricultural soil
    Plant Cell Environ. 2017, 40(3):413-423
  5. Direct acquisition of organic N by white clover even in the presence of inorganic N
    PLANT AND SOIL 2016, 407 (1-2):91-107
  6. Informing climate models with rapid chamber measurements of forest carbon uptake
    Glob Chang Biol. 2017, 23(5):2130-2139
  7. The carbon bonus of organic nitrogen enhances nitrogen use efficiency of plants
    Plant Cell Environ. 2017, 40(1):25-35
  8. Greater carbon allocation to mycorrhizal fungi reduces tree nitrogen uptake in a boreal forest
    ECOLOGY, 97 (4):1012-1022
  9. Soil diffusive fluxes constitute the bottleneck to tree nitrogen nutrition in a Scots pine forest
    PLANT AND SOIL, 2016, 399 (1-2):109-120
  10. Nitrogen dynamics in managed boreal forests: Recent advances and future research directions
    Ambio. 2016;45 Suppl 2:175-87
  11. Stem compression reversibly reduces phloem transport in Pinus sylvestris trees
    TREE PHYSIOLOGY, 2015,  35(10):1075-1085
  12. Nitrogen fluxes at the root-soil interface show a mismatch of nitrogen fertilizer supply and sugarcane root uptake capacity
    Sci. Rep. 2015, 5;15727
  13. Genomics in a changing arctic: critical questions await the molecular ecologist
    MOLECULAR ECOLOGY, 2015, 24(10):2301-2309
  14. How eco-evolutionary principles can guide tree breeding and tree biotechnology for enhanced productivity.
    Tree Physiol. 2014 Nov;34(11):1149-66
  15. Genetics of superior growth traits in trees are being mapped but will the faster-growing risk-takers make it in the wild?
    Tree Physiol. 2014, 34(11):1141-1148
  16. Early season dynamics of soil nitrogen fluxes in fertilized and unfertilized boreal forests
    SOIL BIOLOGY & BIOCHEMISTRY, 2014; 74 167-176

  17. Direct estimation of mass flow and diffusion of nitrogen compounds in solution and soil
    New Phytol. 2014; 201(3):1056-64

  18. Plant nitrogen status and co-occurrence of organic and inorganic nitrogen sources influence root uptake by Scots pine seedlings
    TREE PHYSIOLOGY 2014; 34(2):205-213
  19. Exploring the nitrogen ingestion of aphids - a new method using electrical penetration graph and (15)n labelling
    PLoS One. 2013 Dec 23;8(12):e83085
  20. Organic nitrogen uptake of Scots pine seedlings is independent of current carbohydrate supply
    TREE PHYSIOLOGY 2013; 33(6):590-600
  21. Are ectomycorrhizal fungi alleviating or aggravating nitrogen limitation of tree growth in boreal forests?
    New Phytol. 2013 Jan 29
  22. Inselsbacher E, Näsholm T
    The below-ground perspective of forest plants: soil provides mainly organic nitrogen for plants and mycorrhizal fungi
    New Phytol. 2012 May 4 [Epub ahead of print]
  23. Keel SG, Campbell CD, Högberg MN, Richter A, Wild B, Zhou X, Hurry V, Linder S, Näsholm T, Högberg P.
    Allocation of carbon to fine root compounds and their residence times in a boreal forest depend on root size class and season
    New Phytol: 2012 194(4): 972-981
  24. Svennerstam H, Jämtgård S, Ahmad I, Huss-Danell K, Näsholm T, Ganeteg U
    Transporters in Arabidopsis roots mediating uptake of amino acids at naturally occurring concentrations
    New Phytologist: 2011, 191:459-467
  25. Högberg MN, Briones MJI, Keel SG, Metcalfe DB, Campbell C, Midwood AJ, Thornton B, Hurry V, Linder S, Näsholm T, Högberg P
    Quantification of effects of season and nitrogen supply on tree below-ground carbon transfer to ectomycorrhizal fungi and other soil organisms in a boreal pine forest
    New Phytologist: 2010 187:485-493
  26. Näsholm T, Kielland K, Ganeteg U
    Uptake of organic nitrogen by plants
    New Phytologist: 2009 182:31-48
  27. Forsum O, Svennerstam H, Ganeteg U, Näsholm T
    Capacities and constraints of amino acid utilization in Arabidopsis
    New Phytologist: 2008 179:1058-1069
  28. Jämtgård S, Näsholm T, Huss-Danell K
    Characteristics of amino acid uptake in barley
    Plant and Soil: 2008 302:221-231
  29. Boberg J, Finlay RD, Stenlid J, Näsholm T, Lindahl BD
    Glucose and ammonium additions affect needle decomposition and carbon allocation by the litter degrading fungus Mycena epipterygia.
    S
    oil Biology and Biochemistry: 2008 40:995-999
  30. Högberg P, Högberg MN, Göttlicher SG, Betson NR, Keel SG, Metcalfe DB, Campbell C, Schindbacher A, Hurry V, Lundmark T, Linder S, Näsholm T
    High temporal resolution tracing of photosynthate carbon from the tree canopy to forest soil microorganisms
    New Phytologist: 2008 177:220-228
  31. Svennerstam H, Ganeteg U, Bellini C, Näsholm T
    Comprehensive screening of Arabidopsis mutants suggests the lysine histidine transporter 1 to be involved in plant uptake of amino acids
    Plant Physiology: 2007 145:1853-1860
  32. Forsum A, Dahlman L, Nasholm T, Nordin A
    Nitrogen utilization by Hylocomium splendens in a boreal forest fertilization experiment
    Functional Ecology: 2006 20:421-426
  33. Persson J, Gardestrom P, Nasholm T
    Uptake, metabolism and distribution of organic and inorganic nitrogen sources by Pinus sylvestris
    Journal of Experimental Botany: 2006 57:2651-2659
  34. Nordin A, Strengbom J, Witzell J, Nasholm T, Ericson L
    Nitrogen deposition and the biodiversity of boreal forests: Implications for the nitrogen critical load
    Ambio: 2005 34:20-24
  35. Erikson O, Hertzberg M, Nasholm T
    The dsdA gene from Escherichia coli provides a novel selectable marker for plant transformation
    Plant Mol Biol: 2005 57:425-433
  36. Erikson O, Hertzberg M, Nasholm T
    A conditional marker gene allowing both positive and negative selection in plants
    Nature Biotechnology: 2004 22:455-458
  37. Strengbom J, Nasholm T, Ericson L
    Light, not nitrogen, limits growth of the grass Deschampsia flexuosa in boreal forests
    Canadian Journal of Botany-Revue Canadienne De Botanique: 2004 82:430-435
  38. Lundquist PO, Nasholm T, Huss-Danell K
    Nitrogenase activity and root nodule metabolism in response to O-2 and short-term N-2 deprivation in dark-treated Frankia-Alnus incana plants (vol 119, pg 244, 2003)
    Physiologia Plantarum: 2004 120:171-171
  39. Dahlman L, Persson J, Palmqvist K, Nasholm T
    Organic and inorganic nitrogen uptake in lichens
    Planta: 2004 219:459-467
  40. Ohlund J, Nasholm T
    Regulation of organic and inorganic nitrogen uptake in Scots pine (Pinus sylvestris) seedlings
    Tree Physiology: 2004 24:1397-1402
  41. Dahlman L, Persson J, Nasholm T, Palmqvist K
    Carbon and nitrogen distribution in the green algal lichens Hypogymnia physodes and Platismatia glauca in relation to nutrient supply
    Planta: 2003 217:41-48
  42. Persson J, Hogberg P, Ekblad A, Hogberg MN, Nordgren A, Nasholm T
    Nitrogen acquisition from inorganic and organic sources by boreal forest plants in the field
    Oecologia: 2003 137:252-257
  43. Witzell J, Gref R, Nasholm T
    Plant-part specific and temporal variation in phenolic compounds of boreal bilberry (Vaccinium myrtillus) plants
    Biochemical Systematics and Ecology: 2003 31:115-127
  44. Strengbom J, Walheim M, Nasholm T, Ericson L
    Regional differences in the occurrence of understorey species reflect nitrogen deposition in Swedish forests
    Ambio: 2003 32:91-97
  45. Persson J, Nasholm T
    Regulation of amino acid uptake by carbon and nitrogen in Pinus sylvestris
    Planta: 2003 217:309-315
  46. Dahlman L, Nasholm T, Palmqvist K
    Growth, nitrogen uptake, and resource allocation in the two tripartite lichens Nephroma arcticum and Peltigera aphthosa during nitrogen stress
    New Phytologist: 2002 153:307-315
  47. Ohlund J, Nasholm T
    Low nitrogen losses with a new source of nitrogen for cultivation of conifer seedlings
    Environmental Science & Technology: 2002 36:4854-4859
  48. Strengbom J, Nordin A, Nasholm T, Ericson L
    Parasitic fungus mediates change in nitrogen-exposed boreal forest vegetation
    Journal of Ecology: 2002 90:61-67
  49. Persson J, Nasholm T
    Regulation of amino acid uptake in conifers by exogenous and endogenous nitrogen
    Planta: 2002 215:639-644
  50. Persson J, Nasholm T
    A GC-MS method for determination of amino acid uptake by plants
    Physiol Plant: 2001 113:352-358
  51. Persson J, Nasholm T
    Amino acid uptake: a widespread ability among boreal forest plants
    Ecology Letters: 2001 4:434-438
  52. Ohlund J, Nasholm T
    Growth of conifer seedlings on organic and inorganic nitrogen sources
    Tree Physiology: 2001 21:1319-1326
  53. Nordin A, Uggla C, Nasholm T
    Nitrogen forms in bark, wood and foliage of nitrogen-fertilized Pinus sylvestris
    Tree Physiology: 2001 21:59-64
  54. Nasholm T, Persson J
    Plant acquisition of organic nitrogen in boreal forests
    Physiologia Plantarum: 2001 111:419-426
  55. Strengbom J, Nordin A, Nasholm T, Ericson L
    Slow recovery of boreal forest ecosystem following decreased nitrogen input
    Functional Ecology: 2001 15:451-457
  56. Nordin A, Hogberg P, Nasholm T
    Soil nitrogen form and plant nitrogen uptake along a boreal forest productivity gradient
    Oecologia: 2001 129:125-132
  57. Sundberg B, Nasholm T, Palmqvist K
    The effect of nitrogen on growth and key thallus components in the two tripartite lichens, Nephroma arcticum and Peltigera aphthosa
    Plant Cell and Environment: 2001 24:517-527
  58. Lipson D, Nasholm T
    The unexpected versatility of plants: organic nitrogen use and availability in terrestrial ecosystems
    Oecologia: 2001 128:305-316
  59. Nasholm T, Huss-Danell K, Hogberg P
    Uptake of glycine by field grown wheat
    New Phytologist: 2001 150:59-63
  60. Nasholm T, Huss-Danell K, Hogberg P
    Uptake of organic nitrogen in the field by four agriculturally important plant species
    Ecology: 2000 81:1155-1161
  61. Sundberg B, Ekblad A, Nasholm T, Palmqvist K
    Lichen respiration in relation to active time, temperature, nitrogen and ergosterol concentrations
    Functional Ecology: 1999 13:119-125
  62. Hogberg P, Hogberg MN, Quist ME, Ekblad A, Nasholm T
    Nitrogen isotope fractionation during nitrogen uptake by ectomycorrhizal and non-mycorrhizal Pinus sylvestris
    New Phytologist: 1999 142:569-576
  63. Quist ME, Nasholm T, Lindeberg J, Johannisson C, Hogbom L, Hogberg P
    Responses of a nitrogen-saturated forest to a sharp decrease in nitrogen input
    Journal of Environmental Quality: 1999 28:1970-1977
  64. Nasholm T, Ekblad A, Nordin A, Giesler R, Hogberg M, Hogberg P
    Boreal forest plants take up organic nitrogen
    Nature: 1998 392:914-916
  65. Ekblad A, Wallander H, Nasholm T
    Chitin and ergosterol combined to measure total and living fungal biomass in ectomycorrhizas
    New Phytologist: 1998 138:143-149
  66. Nordin A, Nasholm T, Ericson L
    Effects of simulated N deposition on understorey vegetation of a boreal coniferous forest
    Functional Ecology: 1998 12:691-699
  67. Nasholm T
    Qualitative and quantitative changes in plant nitrogen acquisition induced by anthropogenic nitrogen deposition
    New Phytologist: 1998 139:87-90
  68. Nasholm T, Nordin A, Edfast AB, Hogberg P
    Identification of coniferous forests with incipient nitrogen saturation through analysis of arginine and nitrogen-15 abundance of trees
    Journal of Environmental Quality: 1997 26:302-309
  69. Taylor AFS, Hogbom L, Hogberg M, Lyon AJE, Nasholm T, Hogberg P
    Natural N-15 abundance in fruit bodies of ectomycorrhizal fungi from boreal forests
    New Phytologist: 1997 136:713-720
  70. Nordin A, Nasholm T
    Nitrogen storage forms in nine boreal understorey plant species
    Oecologia: 1997 110:487-492
  71. Edfast AB, Nasholm T, Aronsson A, Ericsson A
    Applications of mineral nutrients to heavily N-fertilized Scots pine trees: Effects on arginine and mineral nutrient concentrations
    Plant and Soil: 1996 184:57-65
  72. Ekblad A, Nasholm T
    Determination of chitin in fungi and mycorrhizal roots by an improved HPLC analysis of glucosamine
    Plant and Soil: 1996 178:29-35
  73. Nohrstedt HO, Sikstrom U, Ring E, Nasholm T, Hogberg P, Persson T
    Nitrate in soil water in three Norway spruce stands in southwest Sweden as related to N-deposition and soil, stand, and foliage properties
    Canadian Journal of Forest Research-Revue Canadienne De Recherche Forestiere: 1996 26:836-848
  74. Ohlson M, Nordin A, Nasholm T
    Accumulation of Amino-Acids in Forest Plants in Relation to Ecological Amplitude and Nitrogen Supply
    Functional Ecology: 1995 9:596-605
  75. Hogberg P, Johannisson C, Hog M, Nasholm T, Hallgren JE
    Measurements of Abundances of N-15 and C-13 as Tools in Retrospective Studies of N Balances and Water-Stress in Forests - a Discussion of Preliminary-Results
    Plant and Soil: 1995 169:125-133
  76. Hogberg P, Jensen P, Nasholm T, Ohlsson H
    Uptake of Mg-24 by Excised Pine Roots - a Preliminary-Study
    Plant and Soil: 1995 172:323-326
  77. Nasholm T, Edfast AB, Ericsson A, Norden LG
    Accumulation of Amino-Acids in Some Boreal Forest Plants in Response to Increased Nitrogen Availability
    New Phytologist: 1994 126:137-143
  78. Nasholm T
    Removal of Nitrogen During Needle Senescence in Scots Pine (Pinus-Sylvestris L)
    Oecologia: 1994 99:290-296
  79. Hogberg P, Nasholm T, Hogbom L, Stahl L
    Use of N-15 Labeling and N-15 Natural-Abundance to Quantify the Role of Mycorrhizas in N-Uptake by Plants - Importance of Seed-N and of Changes in the N-15 Labeling of Available-N
    New Phytologist: 1994 127:515-519
  80. Gezelius K, Nasholm T
    Free Amino-Acids and Protein in Scots Pine-Seedlings Cultivated at Different Nutrient Availabilities
    Tree Physiology: 1993 13:71-86
  81. Ericsson A, Norden LG, Nasholm T, Walheim M
    Mineral Nutrient Imbalances and Arginine Concentrations in Needles of Picea-Abies (L) Karst from 2 Areas with Different Levels of Airborne Deposition
    Trees-Structure and Function: 1993 8:67-74
  82. Sundberg B, Ericsson A, Little CHA, Nasholm T, Gref R
    The Relationship between Crown Size and Ring Width in Pinus- Sylvestris L Stems - Dependence on Indole- 3- Acetic- Acid, Carbohydrates and Nitrogen in the Cambial Region
    Tree Physiology: 1993 12:347-362
  83. Nasholm T, Hogberg P, Edfast AB
    Uptake of Nox by Mycorrhizal and Nonmycorrhizal Scots Pine-Seedlings - Quantities and Effects on Amino-Acid and Protein Concentrations
    New Phytologist: 1991 119:83-92
  84. Nasholm T, McDonald AJS
    Dependence of Amino-Acid-Composition Upon Nitrogen Availability in Birch (Betula-Pendula)
    Physiologia Plantarum: 1990 80:507-514
  85. Edfast AB, Nasholm T, Ericsson A
    Free Amino-Acid-Concentrations in Needles of Norway Spruce and Scots Pine Trees on Different Sites in Areas with 2 Levels of Nitrogen Deposition
    Canadian Journal of Forest Research-Revue Canadienne De Recherche Forestiere: 1990 20:1132-1136
  86. Nasholm T, Ericsson A
    Seasonal changes in amino acids, protein and total nitrogen in needles of fertilized Scots pine trees
    Tree Physiol: 1990 6:267-281
  87. Nasholm T, Ericsson A
    Seasonal-Changes in Amino-Acids, Protein and Total Nitrogen in Needles of Fertilized Scots Pine Trees
    Tree Physiology: 1990 6:267-281