The combined effect of CO2, ozone, and drought on the radical scavenging system of young oak trees (Quercus petraea) — A phytothron study

In order to study the combined effects of CO2, ozone, and drought, we simulated in a controlled environment the climatic conditions of a German oak stand with high ozone (daytime: 80 ppb, control: 20 ppb) during one vegetative period under a regime of low and high CO2 concentration (370 vs 720 ppm) and drought (4 weeks < −800 hPa). To investigate the effects of CO2, ozone and drought on the radical scavenging system, we monitored the level of glutathione, ascorbate, and α-tocopherol. However, it is important that, under the regime of elevated CO2, the antioxidative behaviour of glutathione and ascorbate appears to be masked by their function as storage molecules for sulfur or carbon.