Impact of Elevated Levels of CO2 and O3 on the Yield and Photosynthetic Capabilities of Brassica napus

Abstract

The impact of elevated CO2 (750 ppm), O3 (80 ppb), and the combination of these two gasses were investigated on Brassica napus under well watered and water deficit conditions in Open-top chambers. A decrease in the dry weight (stems and leaves) was observed in the well watered as well as the water deficit treatments when exposed to elevated levels of CO2 and O3. Elevated levels of CO2 and O3 resulted in a decline in yield under well watered conditions. This decline in yield was most likely caused by a decline in the photosynthetic capacity of the plants as revealed by the chlorophyll fluorescence kinetics. However, under water deficit conditions the CO2 fumigated plants had a slight increase in yield. The combined effect of CO2 and O3 did not reveal any significant reductions in yield. This is promising since elevated CO2 levels can reduce the negative effects that air pollutants such as O3 can have on Brassica napus. Though the yield was not affected by the combined fumigation of CO2 and O3, the O3 did managed seriously damage the cuticle layer of the plants leaving the plants exposed to pathogen and insect attack.