Effects of CO₂ Increase on Wheat Growth and Yield under Different Atmospheric Pressures and Their Interaction with Temperature

抄録

To determine the effects of CO₂ under different atmospheric pressures, we assessed the effects of elevated CO₂ on the growth of spring wheat (Triticum aestivum L.) in a field experiment in Lhasa (3688 m above sea level), the Tibet Plateau, China, and in a growth chamber (GC) experiment in Sapporo (15 m above sea level), Japan. Open-top chambers (OTCs) were installed at Lhasa and spring wheat was grown under CO₂ at a partial pressure of 23.4 Pa (ambient CO₂) and 38.5 Pa (elevated CO₂, equivalent to a 200 µmol mol^-1 increase). In the OTC experiments, CO₂ was elevated with gas-firing equipment and a blower, so that the air temperature inside the OTC for elevated CO₂ was raised 0.8ºC. In the GC experiment in Sapporo, we used three CO₂ partial pressure levels; 24.8, 39.8 and 59.3 Pa and two air temperature regimes, 11/19ºC and 11/21ºC (night/day). In the OTC experiment, dry weight at harvest was lower in the elevated CO₂ than in the ambient CO₂. In the GC experiment, the effect of the elevation of CO₂ from 24.8 to 39.8 Pa on biomass was greater than that from 39.8 to 59.3 Pa. A 2ºC increase in temperature reduced dry weight at all CO₂ levels and offset the positive effect of CO₂ increase from 39.8 to 59.3 Pa. The difference between the results obtained in the experiments in OTC and GC was not clear and might have involved artifacts such as blower and/or ethylene effects.