Planta

, Volume 223, Issue 5, pp 1068–1080

How does glutamine synthetase activity determine plant tolerance to ammonium?

Authors

    • Departamento de Biologia Vegetal, Faculdade de Ciências de LisboaCentro de Ecologia e Biologia Vegetal – CEBV
  • A. F. M. Bio
    • Grupo de Ambiente do CMRPInstituto Superior Técnico
  • M. D. Domínguez-Valdivia
    • Departamento de Ciencias del Medio NaturalUniversidad Publica de Navarra
  • P. M. Aparicio-Tejo
    • Departamento de Ciencias del Medio NaturalUniversidad Publica de Navarra
  • C. Lamsfus
    • Departamento de Ciencias del Medio NaturalUniversidad Publica de Navarra
  • M. A. Martins-Loução
    • Departamento de Biologia Vegetal, Faculdade de Ciências de LisboaCentro de Ecologia e Biologia Vegetal – CEBV
Original Article

DOI: 10.1007/s00425-005-0155-2

Cite this article as:
Cruz, C., Bio, A., Domínguez-Valdivia, M. et al. Planta (2006) 223: 1068. doi:10.1007/s00425-005-0155-2

Abstract

The wide range of plant responses to ammonium nutrition can be used to study the way ammonium interferes with plant metabolism and to assess some characteristics related with ammonium tolerance by plants. In this work we investigated the hypothesis of plant tolerance to ammonium being related with the plants’ capacity to maintain high levels of inorganic nitrogen assimilation in the roots. Plants of several species (Spinacia oleracea L., Lycopersicon esculentum L., Lactuca sativa L., Pisum sativum L. and Lupinus albus L.) were grown in the presence of distinct concentrations (0.5, 1.5, 3 and 6 mM) of nitrate and ammonium. The relative contributions of the activity of the key enzymes glutamine synthetase (GS; under light and dark conditions) and glutamate dehydrogenase (GDH) were determined. The main plant organs of nitrogen assimilation (root or shoot) to plant tolerance to ammonium were assessed. The results show that only plants that are able to maintain high levels of GS activity in the dark (either in leaves or in roots) and high root GDH activities accumulate equal amounts of biomass independently of the nitrogen source available to the root medium and thus are ammonium tolerant. Plant species with high GS activities in the dark coincide with those displaying a high capacity for nitrogen metabolism in the roots. Therefore, the main location of nitrogen metabolism (shoots or roots) and the levels of GS activity in the dark are an important strategy for plant ammonium tolerance. The relative contribution of each of these parameters to species tolerance to ammonium is assessed. The efficient sequestration of ammonium in roots, presumably in the vacuoles, is considered as an additional mechanism contributing to plant tolerance to ammonium nutrition.

Keywords

Ammonium tolerance Glutamate dehydrogenase Glutamine synthetase Lactuca Lupinus Lycopersicon Pisum Spinacia

Abbreviations

GDH

Glutamate dehydrogenase

GS

Glutamine synthetase

GS/GOGAT

Glutamine synthetase/glutamate synthase

NR

Nitrate reductase

Copyright information

© Springer-Verlag 2005