Does leaf position within a canopy affect acclimation of photosynthesis to elevated CO{sub 2}? Analysis of a wheat crop under free-air CO{sub 2} enrichment
- Univ. of Essex, Colchester (United Kingdom)
- Brookhaven National Lab., Upton, NY (United States). Environmental Biology and Instrumentation Div.
- Dept. of Agriculture, Phoenix, AZ (United States)
Previous studies of photosynthetic acclimation to elevated CO{sub 2} have focused on the most recently expanded, sunlit leaves in the canopy. The authors examined acclimation in a vertical profile of leaves through a canopy of wheat (Triticum aestivum L.). The crop was grown at an elevated CO{sub 2} partial pressure of 55 Pa within a replicated field experiment using free-air CO{sub 2} enrichment. Gas exchange was used to estimate in vivo carboxylation capacity and the maximum rate of ribulose-1,5-bisphosphate-limited photosynthesis. Net photosynthetic CO{sub 2} uptake was measured for leaves in situ within the canopy. Leaf contents of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), light-harvesting-complex (LHC) proteins, and total N were determined. Elevated CO{sub 2} did not affect carboxylation capacity in the most recently expanded leaves but led to a decrease in lower, shaded leaves during grain development. Despite this acclimation, in situ photosynthetic CO{sub 2} uptake remained higher under elevated CO{sub 2}. Acclimation at elevated CO{sub 2} was accompanied by decreases in both Rubisco and total leaf N contents and an increase in LHC content. Elevated CO{sub 2} led to a larger increase in LHC/Rubisco in lower canopy leaves than in the uppermost leaf. Acclimation of leaf photosynthesis to elevated CO{sub 2} therefore depended on both vertical position within the canopy and the developmental stage.
- Sponsoring Organization:
- Natural Environment Research Council, London (United Kingdom); USDOE, Washington, DC (United States); Department of Agriculture, Washington, DC (United States)
- OSTI ID:
- 290212
- Journal Information:
- Plant Physiology (Bethesda), Vol. 117, Issue 3; Other Information: PBD: Jul 1998
- Country of Publication:
- United States
- Language:
- English
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