Skip to main content

Increased capacity for photosynthesis in wheat grown at elevated CO2: the relationship between electron transport and carbon metabolism


Spring wheat (Triticum aestivum L.) was grown under optimal nutrition for six weeks at 700 and 350 μmol·mol−1 CO2 and simultaneous measurements of photosystem-II (PSII) chlorophyll fluorescence and gas exchange were conducted on intact attached leaves. Plants grown at elevated CO2 had double the concentration of CO2 at the carboxylation site (Cc) despite a lowered stomatal (gs) and mesophyll (gm) conductance compared with ambient-grown plants. Plants grown at elevated CO2 had a higher relative quantum yield of PSII electron transport (ΦPSII) and a higher relative quantum yield of CO2 fixation (ΦCO 2). The higher ΦPSII was due to a larger proportion of open PSII centres, estimated by the coefficient of photochemical quenching of fluorescence (qp), with no change in the efficiency of light harvesting and energy transduction by open PSII centres (F′v/F′m). Analysis of the relationship between ΦPSII and ΦCO 2 conducted under various CO2 and O2 concentrations showed that the higher ΦCO 2 for a given ΦPSII in leaves developed under elevated CO2 was similar to that obtained in leaves upon a partial reduction in photorespiration. Calculation of the allocation of photosynthetic electron-transport products to CO2 and O2 showed that for leaves developed in elevated CO2, there was an increase in both total linear electron flow and electron flow to CO2 and a decrease in electron flow to O2. Plants developed under elevated CO2 showed positive acclimation manifested by a higher ΦCO 2 when measured under ambient CO2 and higher assimilation rates in A/Ci curves. Initial and total activity of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco EC measured in vitro increased by 16 and 15% respectively in leaves from plants grown in elevated CO2, which was in agreement with a 15% higher in vivo carboxylation efficiency. It is concluded that growth of spring wheat at elevated CO2 enhances photosynthesis due to a change in the balance of component processes manifested as an increased capacity for carbon fixation, total electron transport and Rubisco activity, and a concomitant partial reduction of photorespiration.

This is a preview of subscription content, access via your institution.



net CO2 assimilation

Cc :

CO2 concentration at the site of carboxylation

Ci :

intercellular CO2 concentration

Fm, F′m :

maximum fluorescence after 1 h dark adaptation, under steady-state light conditions

Fv, F′v :

variable fluorescence after 1 h dark adaptation, under steady-state light conditions

Fs :

fluorescence at steady state in the light

J1 :

total linear electron flow

JA :

linear electron flow allocated to CO2 assimilation

JL :

linear electron flow allocated to O2 reduction


photon flux density

qp, qN :

coefficients for photochemical, non-photochemical quenching of fluorescence

vc, vo :

rates of RuBP carboxylation, RuBP oxygenation


ribulose-1,5-bisphosphate carboxylase-oxygenase


relative quantum yield of PSII electron transport

ΦCO 2 :

relative quantum yield of CO2 assimilation


  • Arnon DI (1949) Copper enzymes in isolated chloroplasts. Polyphenol oxidase in Beta vulgaris. Plant Physiol 14: 1–14

    Google Scholar 

  • Bowes G (1991) Growth at elevated CO2: photosynthesis mediated through Rubisco, Plant Cell Environ 14: 795–806

    Google Scholar 

  • Brooks A, Farquhar GD (1985) Effect of temperature on the CO2/O2 specificity of Ribulose-1,5-bisphosphate carboxylase/oxygenase and the rate of respiration in the light. Planta 165: 397–406

    Google Scholar 

  • Ehleringer JR (1989) Temperature and energy budgets. In: Pearcy RW, Ehleringer JR, Mooney HA, Rundel PW (eds) Plant physiological ecology. Field methods and instrumentation. Chapman and Hall, London New York Tokyo Melbourne Madras, pp. 117–135

    Google Scholar 

  • Genty B, Briantais J-M, Baker NR (1989) The relationship between the quantum yield of photosynthetic electron transport and quenching of chlorophyll fluorescence. Biochim Biophys Acta 990: 87–92

    CAS  Google Scholar 

  • Ghashghaie J, Cornic G (1994) Effect of temperature on partitioning of photosynthetic electron flow between CO2 assimilation and O2 reduction and on the CO2/O2 specificity of Rubisco. J Plant Physiol 143: 643–650

    Google Scholar 

  • Harbinson J, Genty B, Baker, NR (1989) The relationship between CO2 assimilation and electron transport in leaves. Photosynth Res 25: 213–224

    Google Scholar 

  • Harley PC, Loreto F, Di Marco G, Sharkey TD (1992) Theoretical considerations when estimating the mesophyll conductance to CO2 flux by analysis of the response of photosynthesis to CO2. Plant Physiol 98: 149–1436

    Google Scholar 

  • Hormann H, Neubauer C, Schreiber U (1994) On the relationship between chlorophyll fluorescence quenching and the quantum yield of electron transport in isolated thylakoids. Photosynth Res 40: 93–106

    Google Scholar 

  • Laing WA, Ogren WL, Hageman RH (1974) Regulation of soybean net photosynthetic CO2 fixation by the interaction of CO2, O2, and ribulose 1,5-diphosphate carboxylase. Plant Physiol 54: 678–685

    Google Scholar 

  • Lawlor DW, Keys AJ (1993) Understanding photosynthetic adaptation to changing climate. In: Fowden L, Mansfield T, Stoddart J (eds) Plant adaptation to environmental stress Chapman and Hall, London pp 85–106.

    Google Scholar 

  • Long SP, Drake BG (1991) Effect of the long-term elevation of CO2 concentration in the field on the quantum yield of photosynthesis of the C3 sedge, Scirpus olneyi. Plant Physiol 96: 221–226

    CAS  Google Scholar 

  • Parkinson KJ (1985) A simple method for determining the boundary layer resistance in leaf cuvettes. Plant Cell Environ 8: 223–226

    Google Scholar 

  • Parry MAJ, Delgado E, Vadell J, Keys AJ, Lawlor DW, Medrano H (1993) Water stress and the diurnal activity of ribulose-1,5-bisphosphate carboxylase in field grown Nicotiana tobacum genotypes selected for survival at low CO2 concentrations. Plant Physiol Biochem 31: 113–120

    Google Scholar 

  • Rackham W, Wilson J (1968) Integrating sphere for spectral measurements on leaves. In: Wadsworth RM (ed).The measurement of environmental factors in terrestrial ecology (British Ecol. Symp., vol 8). Blackwell, pp 259–263

  • Sage RF (1994) Acclimation of photosynthesis to increasing atmospheric CO2: The gas exchange perspective. Photosynth Res 39: 351–368

    CAS  Google Scholar 

  • Seaton GGR, Walker DA (1990) Chlorophyll fluorescence as a measure of photosynthetic carbon assimilation. Proc R Soc London Ser B 242: 29–35

    Google Scholar 

  • Sharkey TD (1985) Photosynthesis in intact leaves of C3 plants: physics, physiology and rate limitations. Bot Rev 51: 53–106

    Google Scholar 

  • Stitt M (1991) Rising CO2 levels and their potential significance for carbon flow in photosynthetic cells. Plant Cell Environ 14: 741–762

    CAS  Google Scholar 

  • van Kooten O, Snel JFH (1990) The use of chlorophyll fluorescence nomenclature in plant stress physiology. Photosynth Res 25: 147–150

    Google Scholar 

  • von Caemmerer S, Farquhar GD (1981) Some relationships between the biochemistry of photosynthesis and the gas exchange of leaves. Planta 153: 376–387

    Google Scholar 

  • Walker DA, Sivak MN (1986) Photosynthesis and phosphate: a cellular affair? Trends Biochem Sci 11: 176–179

    Google Scholar 

Download references

Author information

Authors and Affiliations


Corresponding author

Correspondence to Dimah Z. Habash.

Additional information

We would like to thank Simon Driscoll and Valerie Mitchell for technical assistance, Rowan Mitchell and Tony Goodwin for help in curve-fitting and Bernard Genty (Laboratoire d'Ecologie Végétale, Universite De Paris XI, Orsay, France) for critical comments on the manuscript. This work was supported by a grant from the Biotechnology and Biological Sciences Research Council (Agricultural and Food Research Council).

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Habash, D.Z., Paul, M.J., Parry, M.A.J. et al. Increased capacity for photosynthesis in wheat grown at elevated CO2: the relationship between electron transport and carbon metabolism. Planta 197, 482–489 (1995).

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI:

Key words

  • Carbon assimilation
  • Chlorophyll fluorescence
  • Electron transport
  • Elevated CO2
  • Photosynthesis
  • Triticum (photosynthesis)