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Functional Plant Biology Functional Plant Biology Society
Plant function and evolutionary biology
RESEARCH ARTICLE

Nitrogen fertilisation influences low CO2 effects on plant performance

André G. Duarte https://orcid.org/0000-0001-5172-7240 A E , Fred J. Longstaffe A B and Danielle A. Way A C D
+ Author Affiliations
- Author Affiliations

A Department of Biology, The University of Western Ontario, 1151 Richmond St., N6A 3K7, London, Canada.

B Department of Earth Sciences, The University of Western Ontario, 1151 Richmond St., N6A 3K7, London, Canada.

C Nicholas School of the Environment, Duke University, 9 Circuit Dr., 27710, Durham, USA.

D Present address: Division of Plant Sciences, Research School of Biology, The Australian National University, 134 Linnaeus Way, ACT 2601, Canberra, Australia.

E Corresponding author. Email: aduarte4@uwo.ca.

Functional Plant Biology 47(2) 134-144 https://doi.org/10.1071/FP19151
Submitted: 26 May 2019  Accepted: 27 September 2019   Published: 6 January 2020

Abstract

Low atmospheric CO2 conditions prevailed for most of the recent evolutionary history of plants. Such concentrations reduce plant growth compared with modern levels, but low-CO2 effects on plant performance may also be affected by nitrogen availability, since low leaf nitrogen decreases photosynthesis, and CO2 concentrations influence nitrogen assimilation. To investigate the influence of N availability on plant performance at low CO2, we grew Elymus canadensis at ambient (~400 μmol mol–1) and subambient (~180 μmol mol–1) CO2 levels, under four N-treatments: nitrate only; ammonium only; a full and a half mix of nitrate and ammonium. Growth at low CO2 decreased biomass in the full and nitrate treatments, but not in ammonium and half plants. Low CO2 effects on photosynthetic and maximum electron transport rates were influenced by fertilisation, with photosynthesis being most strongly impacted by low CO2 in full plants. Low CO2 reduced stomatal index in half plants, suggesting that the use of this indicator in paleo-inferences can be influenced by N availability. Under low CO2 concentrations, nitrate plants discriminated more against 15N whereas half plants discriminated less against 15N compared with the full treatment, suggesting that N availability should be considered when using N isotopes as paleo-indicators.

Additional keywords: Paleoecology, subambient CO2, δ15N, stomatal index, nitrogen assimilation.


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