Interaction of Sulfur and Nitrogen Nutrition in Tobacco (Nicotiana tabacum) Plants: Significance of Nitrogen Source and Root Nitrate Reductase

Authors

  • J. Kruse,

    1. Institute of Forest Botany and Tree Physiology, Chair of Tree Physiology, Georges-Köhler-Allee 053/054, 79110 Freiburg, Germany
    Search for more papers by this author
    • 2

      Forest Science Centre, Water St. 1, 3363 Creswick, Victoria, Australia

  • S. Kopriva,

    1. Institute of Forest Botany and Tree Physiology, Chair of Tree Physiology, Georges-Köhler-Allee 053/054, 79110 Freiburg, Germany
    Search for more papers by this author
    • 3

      John Innes Centre, Norwich Research Park, Norwich, NR4 7 UH, UK

  • R. Hänsch,

    1. Institute of Plant Biology, Technical University of Braunschweig, Humboldtstraße 1, 38106 Braunschweig, Germany
    Search for more papers by this author
  • G.-J. Krauss,

    1. Institute of Biochemistry, Div. Ecological and Plant Biochemistry, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Straße 3, 06120 Halle, Germany
    Search for more papers by this author
  • R.-R. Mendel,

    1. Institute of Plant Biology, Technical University of Braunschweig, Humboldtstraße 1, 38106 Braunschweig, Germany
    Search for more papers by this author
  • H. Rennenberg

    Corresponding author
    1. Institute of Forest Botany and Tree Physiology, Chair of Tree Physiology, Georges-Köhler-Allee 053/054, 79110 Freiburg, Germany
    Search for more papers by this author

Institut für Forstbotanik und Baumphysiologie Professur für Baumphysiologie Universität Freiburg Georges-Köhler-Allee 053/054 79110 Freiburg Germany E-mail: heinz.rennenberg@ctp.uni-freiburg.de

Abstract

Abstract: The significance of root nitrate reductase for sulfur assimilation was studied in tobacco (Nicotiana tabacum) plants. For this purpose, uptake, assimilation, and long-distance transport of sulfur were compared between wild-type tobacco and transformants lacking root nitrate reductase, cultivated either with nitrate or with ammonium nitrate. A recently developed empirical model of plant internal nitrogen cycling was adapted to sulfur and applied to characterise whole plant sulfur relations in wild-type tobacco and the transformant. Both transformation and nitrogen nutrition strongly affected sulfur pools and sulfur fluxes. Transformation decreased the rate of sulfate uptake in nitrate-grown plants and root sulfate and total sulfur contents in root biomass, irrespective of N nutrition. Nevertheless, glutathione levels were enhanced in the roots of transformed plants. This may be a consequence of enhanced APR activity in the leaves that also resulted in enhanced organic sulfur content in the leaves of the tranformants. The lack of nitrate reductase in the roots in the transformants caused regulatory changes in sulfur metabolism that resembled those observed under nitrogen deficiency. Nitrate nutrition reduced total sulfur content and all the major fractions analysed in the leaves, but not in the roots, compared to ammonium nitrate supply. The enhanced organic sulfur and glutathione levels in ammonium nitrate-fed plants corresponded well to elevated APR activity. But foliar sulfate contents also increased due to decreased re-allocation of sulfate into the phloem of ammonium nitrate-fed plants. Further studies will elucidate whether this decrease is achieved by downregulation of a specific sulfate transporter in vascular tissues.

Ancillary