Reduced photorespiration and increased energy-use efficiency in young CO2-enriched sorghum leaves

Asaph B. Cousins, Neal R. Adam, Gerard W. Wall, Bruce A. Kimball, Paul J. Pinter, Steven W. Leavitt, Robert L. LaMorte, Allan D. Matthias, Michael J. Ottman, Thomas L. Thompson, Andrew N. Webber

Research output: Contribution to journalArticlepeer-review

46 Scopus citations


• To determine the response of C4 plants to elevated CO2 it is necessary to establish whether young leaves have a fully developed C4 photosynthetic apparatus, and whether photosynthesis in these leaves is responsive to elevated CO2. • The effect of free-air CO2 enrichment (FACE) on the photosynthetic development of the C4 crop Sorghum bicolor was monitored. Simultaneous measurements of chlorophyll a fluorescence and carbon assimilation were made to determine energy utilization, quantum yields of carbon fixation (φCO2) and photosystem II (φPSII), as well as photorespiration. • Assimilation in the second leaf of FACE plants was 37% higher than in control plants and lower apparent rates of photorespiration at growth CO2 concentrations were exhibited. In these leaves, φPSll: φCO2 was high at low atmospheric CO2 concentration (Ca) due to overcycling of the C4 pump and increased leakiness. As Ca increased, φPSII: φCO2 decreased as a greater proportion of energy derived from linear electron transfer was used by the C3 cycle. • The stimulation of C4 photosynthesis at elevated Ca in young leaves was partially due to suppressed photorespiration. Additionally, elevated Ca enhanced energy-use efficiency in young leaves, possibly by decreasing CO2 leakage from bundle sheath cells, and by decreasing overcycling of the C4 pump.

Original languageEnglish (US)
Pages (from-to)275-284
Number of pages10
JournalNew Phytologist
Issue number2
StatePublished - 2001


  • C photosynthesis
  • Elevated CO
  • Energy efficiency
  • Free-air CO enrichment (FACE)
  • Photorespiration
  • Sorghum (Sorghum bicolor)

ASJC Scopus subject areas

  • Physiology
  • Plant Science


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