Prof. H. J. Kronzucker

Plant Nutrition Editor, Plant & Soil  (2004-present)
Editorial Board, Plant, Cell & Environment (2006-present)
Evaluation Group, Biological Systems & Functions, Natural Sciences
     & Engineering Research Council of Canada (NSERC)
Inaugural Director, Canadian Centre for World Hunger Research
      (CCWHR)		 Dr. Herbert J. Kronzucker
Canada Research Chair
Systems Biology of Ion Transport & Plant Nutrition

Full Professor
Associate Chair, Research & Graduate Studies
Department of Biological Sciences

 Department of Ecology & Evolutionary Biology
Department of Cell & Systems Biology
Department of Physical & Enivronmental Sciences

University of Toronto
University of Toronto
1265 Military Trail
Toronto, Ontario
Canada M1C 1A4		 U of T logo
 Office (416) 287-7436
Laboratory (416) 287-7427
Fax (416) 287-7642
herbertk@utsc.utoronto.ca
Laboratories:
SY270 (UTSC), Earth Sciences 2056 - Nitrogen Isotope Lab (St. George)



RESEARCH STATEMENT

Declining soil fertility, increasing soil salinization, and a burgeoning human population have led to severe strains on the world's agricultural systems. A key factor in the relief from such strains is the better understanding of plant responses to soil nutrients and toxicants, and the application of this understanding to the improvement of cultivars and farming practices. Our laboratory seeks to directly engage in this urgent mission, by use of a combination of physiological approaches designed to address questions of ion acquisition and stress tolerance at cellular and whole-plant levels, in the world's most important plant species.

We examine the role of nutrient ion fluxes at cellular, whole-organism, and ecosystem levels, focusing on yield potential in cereals, cellular ionic interactions, and drought and salt stresses. Our approach is multidisciplinary, ranging from mathematical modelling to radiotracing of ion fluxes and ecological analyses in the field. The techniques we use include the subcellular tracing of ion fluxes and compartmentation, the genetic manipulation of plant metabolism and nutrient acquisition, electrophysiology, gas exchange, ionic and metabolic profiling of tissues, and analyses of plant growth and yield. We strive to investigate the physiology of intact model and non-model organisms, and develop methods to tackle the complexity associated with whole systems.

Our laboratory currently receives funding from the Natural Sciences and Engineering Research Council of Canada (NSERC), the Canada Research Chair (CRC) program, the Canadian Foundation for Innovation (CFI), and Canada's national Green Crop Network (GCN), aimed at increasing greenhouse gas capture through biological means. Our collaborative partners include The International Rice Research Institute, The University of Copenhagen, The University of Bonn, The University of Montpellier, and The Chinese Academy of Sciences, as well as many partners within Canada, including the Canadian Association for Mental Health (CAMH) in Toronto, the Tri-University Meson Facility (TRIUMF) in Vancouver, and the BIOTRON facility at the Universities of Guelph and Western Ontario.


Toronto Life Dec 2009 Our research has been featured in numerous newspapers, magazines, television and radio interviews, the 2010 G20 Conference in Toronto, and recent cover articles in Toronto Life magazine and The Globe & Mail newspaper.

RESEARCH GROUP

Senior Research Fellow:

Dr. Dev T. Britto

Research Technician:

Wayne Huynh

Graduate Students:

Lasse M. Schulze, Ph.D. candidate

Devrim Coskun, Ph.D. candidate, Alexander Graham Bell NSERC Award winner

Congratulations to Alexander Becker on his recent completion of a Master's degree!

Undergraduate Students:

Mingyuan Li (2011 NSERC Summer Fellow)
Kai Jean
Daniela Fiorini
Jyoti Bakshi
Hasan Abdullah

PUBLICATIONS  Plant, Cell & Environment cover     Physiologia Plantarum cover cover articles - see Balkos et al. (2010), and Kronzucker et al. (2003, Physiologia Plantarum) below.
  1. Gattward, J.N., de Almeida, A.F., Souza Júnior, J.O., Gomes, F.P., Kronzucker, H.J. (2012). Sodium-potassium synergism in Theobroma cacao: Stimulation of photosynthesis, water-use-efficiency, and mineral nutrition. Physiologia Plantarum in press.
  2. Schulze, L.M., Britto, D.T., Li, M., Kronzucker, H.J. (2012). A pharmacological analysis of high-affinity sodium transport in barley (Hordeum vulgare L.): A 24Na+/ 42K+ study. Journal of Experimental Botany doi:10.1093/jxb/err419.
  3. Li, G.J., Dong, G.Q., Li, B.H., Li, Q., Kronzucker, H.J., Shi W.M. (2012). Isolation and characterization of a novel ammonium-overly-sensitive mutant, amos2, in Arabidopsis thaliana. Planta doi:10.1007/s00425-011-1504-y.
  4. Coskun, D., Britto, D.T., Jean, Y-K., Schulze L., Becker, A., Kronzucker, H.J. (2012). Silver ions disrupt K+ homeostasis and cellular integrity in barley (Hordeum vulgare L.) roots. Journal of Experimental Botany 63, 151-162.
  5. Li, B.H., Li, Q., Kronzucker, H.J., Shi, W.M. (2011). Roles of abscisic acid and auxin in shoot-supplied ammonium inhibition of root system  development. Plant Signaling & Behavior 6, 1451-1453.
  6. Britto, D.T. & Kronzucker, H.J. (2011). Genes do not form channels. Plant and Soil 346, 15-17.
  7. Li, B., Li, Q., Su, Y., Chen, H., Xiong, L, Mi, G., Kronzucker, H.J., Shi, W.M. (2011). Shoot-supplied ammonium targets the root auxin influx carrier AUX1 and inhibits lateral root emergence in Arabidopsis. Plant, Cell & Environment 34, 933-946.
  8. Kronzucker, H.J. & Britto, D.T. (2011). Sodium transport in plants: A critical review. New Phytologist 189, 54-81. (Tansley Review)
  9. Coskun, D., Britto, D.T., Kronzucker, H.J. (2010). Regulation and mechanism of potassium release from barley roots: an in planta 42K analysis. New Phytologist  188, 1028–1038.
  10. Li, Q., Li, B.H., Kronzucker, H.J., Shi, W.M. (2010). Root growth inhibition by NH4+ in Arabidopsis is mediated by the root tip and is linked to NH4+ efflux and GMPase activity. Plant, Cell & Environment 33, 1529-1542.
  11. Britto, D.T., Ebrahimi-Ardebili S., Hamam, A.M., Coskun, D., Kronzucker, H.J. (2010). 42K analysis of sodium-induced potassium efflux in barley: Mechanism and relevance to salt tolerance. New Phytologist 186, 373-384.
  12. Balkos, K.D., Britto, D.T., Kronzucker, H.J. (2010). Optimization of ammonium acquisition and metabolism by potassium in rice (Oryza sativa L. cv. IR-72). Plant, Cell & Environment 33, 23–34. (cover article) 
  13. Britto, D.T. & Kronzucker, H.J. (2009). Ussing's conundrum and the search for transport mechanisms in plants. New Phytologist 183, 243-246.
  14. Szczerba, M.W., Britto, D.T., Kronzucker, H.J. (2009). K+ transport in plants: physiology and molecular biology. Journal of Plant Physiology 166, 447-466.
  15. Malagoli, P., Britto, D.T., Schulze, L.M., Kronzucker, H.J. (2008). Futile Na+ cycling at the root plasma membrane in rice (Oryza sativa L.) – kinetics, energetics, and relation to salinity tolerance. Journal of Experimental Botany 59, 4109–4117.
  16. Szczerba, M.W., Britto, D.T., Ali, S.A., Balkos, K.D., Kronzucker, H.J. (2008). NH4+-stimulated and -inhibited components of K+ transport in rice (Oryza sativa L.). Journal of Experimental Botany 59, 3415-3423.
  17. Kronzucker, H.J., Szczerba, M.W., Schulze, L.M., Britto, D.T. (2008). Non-reciprocal interactions between K+ and Na+ ions in barley. Journal of Experimental Botany 59, 2793-2801. 
    18.
  18. Britto, D.T. & Kronzucker, H.J. (2008). Cellular mechanisms of potassium transport in plants. Physiologia Plantarum 133, 637-650.
  19. Szczerba, M.W., Britto, D.T., Balkos, Kronzucker, H.J. (2008). Alleviation of rapid, futile ammonium cycling at the plasma membrane by potassium reveals K+-sensitive and -insensitive components of NH4+ transport. Journal of Experimental Botany 59, 303-313.
  20. Britto, D.T. & Kronzucker, H.J. (2007).  Mechanisms of potassium transport in plants. Proceedings of the International Fertiliser Society 605, 1-24.
  21. Britto, D.T. & Kronzucker, H.J. (2006). Futile cycling at the plasma membrane: A hallmark of low-affinity nutrient transport. Trends in Plant Science 11, 529-534. 
  22. Kronzucker, H.J., Szczerba, M.W., Moazami-Goudarzi, M., Britto, D.T. (2006). The cytosolic Na+:K+ ratio does not explain salinity-induced growth impairment in barley : A dual-tracer study using 42K+ and 24Na+. Plant, Cell & Environment 29, 2228-2237.
  23. Szczerba, M.W., Britto, D.T., Kronzucker, H.J. (2006). Rapid, futile K+ cycling and pool-size dynamics define low-affinity potassium transport in barley. Plant Physiology 141, 1494-1507. 
  24. Szczerba, M.W., Britto, D.T., Kronzucker, H.J. (2006). The face value of ion fluxes: the challenge of determining influx in the low-affinity transport range. Journal of Experimental Botany 57, 3293-3300.
  25. Britto, D.T., Szczerba, M.W., Kronzucker, H.J. (2006). A new, non-perturbing sampling procedure in tracer exchange measurements. Journal of Experimental Botany 57, 1309-1314.
  26. Britto, D.T. & Kronzucker, H.J. (2005). Plant nitrogen transport and its regulation in changing soil environments. Journal of Crop Improvement 15, 1-23.
  27. Britto, D.T. & Kronzucker, H.J. (2005). Nitrogen acquisition, PEP carboxylase, and cellular pH homeostasis: New views on old paradigms. Plant, Cell & Environment 28, 1396-1409.
  28. Kirk, G.J.D & Kronzucker, H.J. (2005). The potential for nitrification and nitrate uptake in the rhizospheres of wetland plants: A modelling study. Annals of Botany 96, 639 - 646.
  29. Kronzucker, H.J. (2005). A new encyclopedic account of plant nutrition: broad, brilliant, but also flawed. American Journal of Botany 92, 1421-1424.
  30. Britto, D.T. & Kronzucker, H.J. (2005). Plant nitrogen transport and its regulation in changing soil environments. In: Enhancing the Efficiency of Nitrogen Utilization in Plants. (A.S. Basra, S.S. Goyal & R. Tischner, eds.). The Haworth Press Inc., Binghampton, NY, pp. 1-23.
  31. Britto, D.T. & Kronzucker H.J. (2004). Bioengineering N acquisition in rice: Can novel initiatives in rice genomics and physiology contribute to global food security? BioEssays 26, 683-692.
  32. Britto, D.T., Ruth, T.J., Lapi, S., Kronzucker, H.J. (2004). Cellular and whole-plant chloride dynamics in barley: Insights into chloride-nitrogen interactions and salinity responses. Planta 218, 615-622.
  33. Britto, D.T. & Kronzucker H.J. (2004). Biology and Biotechnology of Nitrogen Acquisition in Rice: Implications for Food Security. In: Plant Ecophysiology, Vol. 3: Nitrogen Acquisition and Assimilation in Higher Plants (S. Amâncio, & I.D.H. Stulen, eds.). Kluwer Academic Publishers, The Netherlands, pp. 261-281.
  34. Britto, D.T. & Kronzucker, H.J. (2003). Trans-stimulation of 13NH4+ efflux provides evidence for the cytosolic origin of tracer in the compartmental analysis of barley roots. Functional Plant Biology 30, 1233-1238.
  35. Britto, D.T. & Kronzucker, H.J. (2003). Cytosolic ion exchange dynamics: Insights into the mechanisms of component ion fluxes and their measurement. Functional Plant Biology 30, 355-363.
  36. Kronzucker, H.J., Szczerba, M.W., Britto, D.T. (2003). Cytosolic potassium homeostasis revisited: 42K-tracer analysis reveals set-point variations in [K+]. Planta 217, 540-546.
  37. Britto, D.T. & Kronzucker, H.J. (2003). Ion fluxes and cytosolic pool sizes: examining fundamental relationships in transmembrane flux regulation. Planta 217, 490-497.
  38. Kronzucker, H.J., Siddiqi, M.Y., Glass, A.D.M., Britto, D.T. (2003).Root ammonium transport efficiency as a determinant in forest colonization patterns: an hypothesis. Physiologia Plantarum 117, 164-170. (cover article) 
  39. Britto, D.T. & Kronzucker, H.J. (2003). The case for cytosolic NO3- heterostasis: a critique of a recently proposed model. Plant, Cell & Environment 26, 183-188.
  40. Britto, D.T., Siddiqi, M.Y., Glass, A.D.M., Kronzucker, H.J. (2002). Subcellular NH4+ flux analysis in leaf segments of wheat (Triticum aestivum L.). New Phytologist 155, 373-380.
  41. Britto, D.T. & Kronzucker, H.J. (2002). NH4+ toxicity in higher plants: A critical review. Journal of Plant Physiology 159, 567-584. (invited review)
  42. Glass, A.D.M., Britto, D.T., Kaiser, B.N., Kinghorn, J.R., Kronzucker, H.J., Kumar, A., Okamoto, M., Rawat, S., Siddiqi, M.Y., Unkles, S.E., Vidmar, J.J. (2002). The regulation of nitrate and ammonium transport systems in plants. Journal of Experimental Botany 53, 855-864.
  43. Kronzucker, H.J., Britto, D.T., Davenport, R., Tester, M. (2001). Ammonium toxicity and the real cost of transport. Trends in Plant Science 6, 335-337.
  44. Britto, D.T., Siddiqi, M.Y., Glass, A.D.M., Kronzucker, H.J. (2001). Futile transmembrane NH4+ cycling: A cellular hypothesis to explain ammonium toxicity in plants. Proceedings of the National Academy of Sciences, USA 98, 4255-4258.
  45. Britto, D.T. & Kronzucker, H.J. (2001).  Constancy of nitrogen turnover kinetics in the plant cell: Insights into the integration of subcellular N fluxes. Planta 213, 175-181.
  46. Britto, D.T. & Kronzucker, H.J. (2001).  Can unidirectional influx be measured in higher plants? A mathematical approach using parameters from efflux analysis. New Phytologist 150, 37-47.
  47. Britto, D.T., Glass, A.D.M., Kronzucker, H.J., Siddiqi, M.Y. (2001). Cytosolic concentrations and transmembrane fluxes of NH4+/NH3 . An examination of recent proposals. Plant Physiology 125, 523-526.
  48. Glass, A.D.M., Britto, D.T., Kaiser, B.N., Kronzucker, H.J., Kumar, A., Okamoto, M., Rawat, S.R., Siddiqi, M.Y., Silim, S.M., Vidmar, J.J., Zhou, D. (2001). Nitrogen transport in plants, with an emphasis on the regulation of fluxes to match plant demand. Journal of Plant Nutrition and Soil Science 164, 199-207.
  49. Kronzucker, H.J., Siddiqi, M.Y., Glass, A.D.M., Kirk, G.J.D. (2000). Comparative kinetic analysis of ammonium and nitrate acquisition by tropical lowland rice: Implications for rice cultivation and yield potential. New Phytologist 145, 471-476.
  50. Min, X.J., Siddiqi, M.Y., Glass, A.D.M., Guy, R.D., Kronzucker, H.J. (2000). A kinetic analysis of nitrate and ammonium influx in two early-successional tree species of temperate and boreal ecosystems. Plant, Cell & Environment 23, 321-328.
  51. Britto, D.T., Glass, A.D.M., Kronzucker, H.J. (2000). Studies of Nitrogen Absorption and Assimilation in Plants by Use of 13N. In: Isotope Production And Applications In The 21st Century: Proceedings of the 3rd International Conference on Isotopes (Nigel Stevenson, ed.). World Scientific Publ. Co., Singapore, pp. 433-435.
  52. Kirk, G.J.D. & Kronzucker, H.J. (2000). Nitrogen Uptake by Rice Roots. In: Carbon and Nitrogen Dynamics in Flooded Ecosystems (G.J.D. Kirk & D.C. Olk, eds.). International Rice Research Institute, IRRI, Makati City, Philippines, pp. 147-162.
  53. Bingham, I.J., Glass, A.D.M., Kronzucker, H.J., Robinson, D., Scrimgeour, C.M. (2000). Isotope techniques. In: Root Methods: A Handbook. pp. 365-402.
  54. Rawat, S.R., Silim, S.N., Kronzucker, H.J., Siddiqi, M.Y., Glass, A.D.M. (1999). AtAMT1 gene expression and NH4+ uptake in roots of Arabidopsis thaliana : Evidence for regulation by root glutamine levels. The Plant Journal 19, 143-152.
  55. Kronzucker, H.J., Glass, A.D.M., Siddiqi, M.Y. (1999). Inhibition of nitrate uptake by ammonium in barley: Analysis of component fluxes. Plant Physiology 120, 283-292.
  56. Min, X.J., Siddiqi, M.Y., Glass, A.D.M., Guy, R.D., Kronzucker, H.J. (1999). A comparative study of fluxes and compartmentation of nitrate and ammonium in early-successional tree species. Plant, Cell & Environment 22, 821-830.
  57. Kronzucker, H.J., Siddiqi, M.Y., Glass, A.D.M., Kirk, G.J.D. (1999). Nitrate-ammonium synergism in rice: A subcellular analysis. Plant Physiology 119, 1041-1046.
  58. Glass, A.D.M., Erner, Y., Hunt, T., Kronzucker, H.J., Okamoto, M., Rawat, S.R., Silim, S., Schjoerring, J.K., Siddiqi, M.Y., Vidmar, J.J., Wang, M.Y., Zhou, D. (1999). Inorganic Nitrogen Absorption by Plant Roots: Physiology and Molecular Biology . In: Plant Nutrition Molecular Biology and Genetics (G. Gissel-Nielsen & A. Jensen, eds.). Kluwer Academic, Wageningen, Netherlands, pp. 1-16.
  59. Kronzucker, H.J., Schjoerring, J.K., Erner, Y., Kirk, G.J.D., Siddiqi, M.Y., Glass, A.D.M. (1998). Dynamic interactions between root NH4+ influx and long-distance N translocation in rice: Insights into feedback processes. Plant & Cell Physiology 39, 1287-1293.
  60. Min, X.J., Siddiqi, M.Y., Guy, R.D., Glass, A.D.M., Kronzucker, H.J. (1998). Induction of nitrate uptake and nitrate reductase activity in trembling aspen and lodgepole pine . Plant, Cell & Environment 21, 1039-1046.
  61. Kronzucker, H.J. & Kirk, G.J.D. (1998). Importance of nitrate vs. ammonium for potential yield. In: Irrigated Rice Ecosystem. International Rice Research Institute, IRRI Research Reports, Makati City, Philippines, pp.12-13.
  62. Siddiqi, M.Y., Kronzucker, H.J., Britto, D.T., Glass, A.D.M. (1998). Growth of a tomato crop at reduced nutrient concentrations as a strategy to limit eutrophication. Journal of Plant Nutrition 21, 1879-1895.
  63. Kronzucker, H.J., Kirk, G.J.D., Siddiqi, M.Y., Glass, A.D.M. (1998). Effects of hypoxia on 13NH4+ fluxes in rice roots: Kinetics and compartmental analysis. Plant Physiology 116, 581-587.
  64. Glass, A.D.M., Erner, Y., Kronzucker, H.J., Schjoerring, J.K., Siddiqi, M.Y., Wang, M.Y. (1997). Ammonium fluxes into plant roots: Energetics, kinetics and regulation. Zeitschrift für Pflanzenernährung und Bodenkunde 160, 261-268.
  65. Johnson, R.R., Glass, A.D.M., Kronzucker, H.J., Gelbort, Z., Venczel, E., Paul, M., Berkovits, D., Cavan, A., Kashiv, Y., Ghelberg, S. (1997). Measurement of aluminum transport in wheat at the cellular level. Nuclear Instruments and Methods in Physics Research (Section B) - Beam Interactions with Materials and Atoms 123, 283-286.
  66. Kronzucker, H.J., Siddiqi, M.Y., Glass, A.D.M. (1997). Conifer root discrimination against soil nitrate and the ecology of forest succession. Nature 385, 59-61.
  67. Kronzucker, H.J., Siddiqi, M.Y., Glass, A.D.M. (1996). Kinetics of NH4+ influx in spruce. Plant Physiology 110, 773-779.
  68. Kronzucker, H.J., Siddiqi, M.Y., Glass, A.D.M. (1995). Analysis of 13NH4+ efflux in spruce roots: A test case for phase identification in compartmental analysis. Plant Physiology 109, 481-490.
  69. Kronzucker, H.J., Siddiqi, M.Y., Glass, A.D.M. (1995). Kinetics of NO3- influx in spruce. Plant Physiology 109, 319-326.
  70. Kronzucker, H.J., Siddiqi, M.Y., Glass, A.D.M. (1995). Compartmentation and flux characteristics of ammonium in spruce. Planta 196, 691-698.
  71. Kronzucker, H.J., Glass, A.D.M., Siddiqi, M.Y. (1995). Nitrate induction in spruce: An approach using compartmental analysis. Planta 196, 683-690.
  72. Kronzucker, H.J., Siddiqi, M.Y., Glass, A.D.M. (1995). Compartmentation and flux characteristics of nitrate in spruce. Planta 196, 674-682.


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