The influence of phosphorus deficiency on growth and nitrogen fixation of white clover plants

Henning Høgh Jensen, Jan K. Schjoerring, Jean-Francois Soussana

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The effects of P deficiency on growth, N2-fixation and photosynthesis in white clover (Trifolium repens L.) plants were investigated using three contrasting relative addition rates of P, or following abrupt withdrawal of the P supply. Responses to a constant below-optimum P supply rate consisted of a decline in N2-fixation per unit root weight and a small reduction in the efficiency with which electrons were allocated to the reduction of N2 in nodules. Abrupt removal of P arrested nodule growth and caused a substantial decline in nitrogenase activity per unit root weight, but not per unit nodule mass. Similarly, the rate of photosynthesis per unit leaf area was unaffected by abrupt P removal, whereas CO2 acquisition for the plant as a whole decreased due to a decline in total leaf area, leaf area per unit leaf weight and utilization of incoming radiation. These changes followed the decline in tissue P concentrations. The ratio between CO2-fixation and N2-fixation was maintained under short-term P deprivation but increased under long-term low P supply, indicating a regulatory inhibition of nodule activity following morphological and growth adjustments. It is concluded that N2-fixation did not limit the growth of clover plants experiencing P deficiency. A low P status induced changes in the relative growth of roots, nodules and shoots rather than changes in N and/or C uptake rates per unit mass or area of these organs. (C) 2002 Annals of Botany Company.

Original languageEnglish
JournalAnnals of Botany
Volume90
Issue number6
Pages (from-to)745-753
ISSN0305-7364
DOIs
Publication statusPublished - 2002
Externally publishedYes

Keywords

  • Fodder legumes
  • Grassland
  • Phosphorus
  • Phosphorus deficiency
  • Photosynthetic efficiency
  • N-2-fixation
  • Nitrogenase activity
  • Relative addition rate
  • Specific shoot area
  • Trifolium repens L.
  • White clover

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