Planta

, Volume 220, Issue 3, pp 434–446

The growth of soybean under free air [CO2] enrichment (FACE) stimulates photosynthesis while decreasing in vivo Rubisco capacity

  • Carl J. Bernacchi
  • Patrick B. Morgan
  • Donald R. Ort
  • Stephen P. Long
Original Article

DOI: 10.1007/s00425-004-1320-8

Cite this article as:
Bernacchi, C.J., Morgan, P.B., Ort, D.R. et al. Planta (2005) 220: 434. doi:10.1007/s00425-004-1320-8

Abstract

Down-regulation of light-saturated photosynthesis (Asat) at elevated atmospheric CO2 concentration, [CO2], has been demonstrated for many C3 species and is often associated with inability to utilize additional photosynthate and/or nitrogen limitation. In soybean, a nitrogen-fixing species, both limitations are less likely than in crops lacking an N-fixing symbiont. Prior studies have used controlled environment or field enclosures where the artificial environment can modify responses to [CO2]. A soybean free air [CO2] enrichment (FACE) facility has provided the first opportunity to analyze the effects of elevated [CO2] on photosynthesis under fully open-air conditions. Potential ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) carboxylation (Vc,max) and electron transport through photosystem II (Jmax) were determined from the responses of Asat to intercellular [CO2] (Ci) throughout two growing seasons. Mesophyll conductance to CO2 (gm) was determined from the responses of Asat and whole chain electron transport (J) to light. Elevated [CO2] increased Asat by 15–20% even though there was a small, statistically significant, decrease in Vc,max. This differs from previous studies in that Vc,max/Jmax decreased, inferring a shift in resource investment away from Rubisco. This raised the Ci at which the transition from Rubisco-limited to ribulose-1,5-bisphosphate regeneration-limited photosynthesis occurred. The decrease in Vc,max was not the result of a change in gm, which was unchanged by elevated [CO2]. This first analysis of limitations to soybean photosynthesis under fully open-air conditions reveals important differences to prior studies that have used enclosures to elevate [CO2], most significantly a smaller response of Asat and an apparent shift in resources away from Rubisco relative to capacity for electron transport.

Keywords

Electron transport Free air [CO2] enrichment Photosynthesis Rising atmospheric [CO2Rubisco Soybean 

Abbreviations

FACE

Free air [CO2] enrichment

Rubisco

Ribulose-1,5-bisphosphate carboxylase/oxygenase

RuBP

Ribulose-1,5-bisphosphate

SoyFACE

Soybean free air [CO2] enrichment

VPD

Vapor pressure deficit

Copyright information

© Springer-Verlag 2004

Authors and Affiliations

  • Carl J. Bernacchi
    • 1
    • 2
  • Patrick B. Morgan
    • 3
  • Donald R. Ort
    • 2
    • 3
  • Stephen P. Long
    • 3
  1. 1.Atmospheric Environment SectionIllinois State Water SurveyChampaignUSA
  2. 2.Photosynthesis Research Unit, Agricultural Research ServiceUnited States Department of AgricultureUrbanaUSA
  3. 3.Departments of Plant Biology and Crop SciencesUniversity of IllinoisUrbanaUSA