Seneweera, Saman , Makino, Amane , Mae, Tadahiko .
Acclimation of canopy photosynthesis to long term CO2 enrichment: relationship between leaf nitrogen and ribulose-1,5-bisphosphate carboxylase/oxygenase concentrations.
We tested the hypothesis that acclimation of leaf photosynthesis to elevated CO2 is associated with factors other than accumulation of carbohydrates. This was achieved by determining the relationship between A, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), total nitrogen and carbohydrate concentrations in leaves at different positions in rice. The developmental stages of these leaves varied from expanding to fully expanded. Plants were grown for 70 days with a high nitrogen supply, in artificially illuminated growth chambers CO2 concentration of either 39 or 100 Pa. Gas exchange measurements were used to estimate in vivo maximum carboxylation (Vc.max) and maximum electron transport capacity (Jmax). Concentrations of Rubisco, soluble protein, chlorophyll, total nitrogen, carbon , sucrose and starch in leaf blades were also determined. Nitrogen allocation to leaf blade, sheaths and roots were also calculated. Long term growth at elevated CO2 suppressed light saturated photosynthesis (Amax), Vc.max and Jmax in leaf blades at all positions in the canopy. Amax was reduced at elevated CO2 by approximately 25% and this was associated with a similar reduction in leaf N and Rubisco concentrations. Less N was allocated to leaf blades over leaf sheath and root at elevated CO2. Regardless of growth CO2 or leaf position, Amax was positively correlated with leaf N and Rubisco concentration. However, the reduction in Amax and Rubisco concentration due to elevated CO2 tended to be smaller in the expanding and last fully expanded leaf blades (upper canopy) than in the expanded leaf blades of the lower canopy. Large reduction of Amax in lower canopy was associated with accelerated Rubisco degradation. Sucrose concentration was increased in the upper canopy by elevated CO2 but there was no relationship between Amax and sucrose concentration. We conclude that sucrose accumulation does not play an important role in acclimation of Amax to high CO2.
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1 - University of Western Sydney, Centre for Plant and Food Science, Bourke street, Richmond, NSW, 2753, Australia
2 - Tohoku University, Applied Plant Science
3 - Tohoku University, Department of Applied Plant Science
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM