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

Abstract

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.

Keywords

• Dry matter production
• High altitude
• Low partial pressure of CO2
• Temperature
• Triticum aestivum L
• Yield