CO2 enrichment inhibits shoot nitrate assimilation in C3 but not C4 plants and slows growth under nitrate in C3 plants

Arnold J. Bloom, Jose Salvador Rubio Asensio, Lesley Randall, Shimon Rachmilevitch, Asaph B. Cousins, Eli A. Carlisle

Research output: Contribution to journalArticlepeer-review

98 Scopus citations

Abstract

The CO 2 concentration in Earth's atmosphere may double during this century. Plant responses to such an increase depend strongly on their nitrogen status, but the reasons have been uncertain. Here, we assessed shoot nitrate assimilation into amino acids via the shift in shoot CO 2 and O 2 fluxes when plants received nitrate instead of ammonium as a nitrogen source (ΔAQ). Shoot nitrate assimilation became negligible with increasing CO 2 in a taxonomically diverse group of eight C 3 plant species, was relatively insensitive to CO 2 in three C 4 species, and showed an intermediate sensitivity in two C 3-C 4 intermediate species. We then examined the influence of CO 2 level and ammonium vs. nitrate nutrition on growth, assessed in terms of changes in fresh mass, of several C 3 species and a Crassulacean acid metabolism (CAM) species. Elevated CO 2 (720 μmol CO 2/mol of all gases present) stimulated growth or had no effect in the five C 3 species tested when they received ammonium as a nitrogen source but inhibited growth or had no effect if they received nitrate. Under nitrate, two C 3 species grew faster at sub-ambient (∼310 μmol/mol) than elevated CO 2. A CAM species grew faster at ambient than elevated or sub-ambient CO 2 under either ammonium or nitrate nutrition. This study establishes that CO 2 enrichment inhibits shoot nitrate assimilation in a wide variety of C 3 plants and that this phenomenon can have a profound effect on their growth. This indicates that shoot nitrate assimilation provides an important contribution to the nitrate assimilation of an entire C 3 plant. Thus, rising CO 2 and its effects on shoot nitrate assimilation may influence the distribution of C 3 plant species.

Original languageEnglish
Pages (from-to)355-367
Number of pages13
JournalEcology
Volume93
Issue number2
DOIs
StatePublished - 1 Feb 2012

Keywords

  • C
  • CO acclimation
  • Climate change
  • Crassulacean acid metabolism (CAM)
  • Nitrogen
  • Plant distributions

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