Plant growth responses to elevated atmospheric CO2 are increased by phosphorus sufficiency but not by arbuscular mycorrhizas.
Capturing the full growth potential in crops under future elevated CO2(eCO2) concentrations would be facilitated by improved understanding of eCO2effects on uptake and use of mineral nutrients. This study investigates interactions of eCO2, soil phosphorus (P), and arbuscular mycorrhizal (AM) symbiosis in Medicago truncatula and Brachypodium distachyon grown under the same conditions. The focus was on eCO2effects on vegetative growth, efficiency in acquisition and use of P, and expression of phosphate transporter (PT) genes. Growth responses to eCO2were positive at P sufficiency, but under low-P conditions they ranged from non-significant in M. truncatula to highly significant in B. distachyon Growth of M. truncatula was increased by AM at low P conditions at both CO2levels and eCO2×AM interactions were sparse. Elevated CO2had small effects on P acquisition, but enhanced conversion of tissue P into biomass. Expression of PT genes was influenced by eCO2, but effects were inconsistent across genes and species. The ability of eCO2to partly mitigate P limitation-induced growth reductions in B. distachyon was associated with enhanced P use efficiency, and requirements for P fertilizers may not increase in such species in future CO2-rich climates.
Department of Chemical and Biochemical Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark ivja@plen.ku.dk.|Present address: Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, DK-1871, Thorvaldsensvej 40, Frederiksberg C, Denmark.
Iver
I
Jakobsen
Department of Chemical and Biochemical Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.|Present address: Soils Group, School of Agriculture, Food and Wine, Waite Campus, The University of Adelaide, SA 5005, Australia.
Sally E
SE
Smith
Department of Chemical and Biochemical Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.|Present address: Soils Group, School of Agriculture, Food and Wine, Waite Campus, The University of Adelaide, SA 5005, Australia.
F Andrew
FA
Smith
Department of Chemical and Biochemical Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.|Present address: Boyce Thompson Institute, Tower Rd, Ithaca, NY 14853, USA.
Stephanie J
SJ
Watts-Williams
Department of Chemical and Biochemical Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.|Present address: Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, DK-1871, Thorvaldsensvej 40, Frederiksberg C, Denmark.
Signe S
SS
Clausen
Department of Chemical and Biochemical Engineering, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.|Present address: Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, DK-1871, Thorvaldsensvej 40, Frederiksberg C, Denmark.
Mette
M
Grønlund
D058431:Brachypodium / Q000502:physiology*; D002245:Carbon Dioxide / Q000378:metabolism*; D046913:Medicago truncatula / Q000254:growth & development* / Q000378:metabolism / Q000382:microbiology; D038821:Mycorrhizae / Q000502:physiology*; D028061:Phosphate Transport Proteins / Q000378:metabolism; D010758:Phosphorus / Q000378:metabolism*; D018517:Plant Roots / Q000382:microbiology; D060888:Real-Time Polymerase Chain Reaction; D013559:Symbiosis
D028061:Phosphate Transport Proteins; D002245:Carbon Dioxide; D010758:Phosphorus

Brachypodium distachyon
; 
Medicago truncatula
; Arbuscular mycorrhizal symbiosis; elevated atmospheric CO2
; gene expression; phosphate transporters; plant growth; plant phosphorus uptake; soil phosphorus.