Growth of five hybrid poplar genotypes exposed to interacting elevated CO₂ and O₃

Abstract

A wide variety of hybrid poplar clones are being introduced for intensive culture biomass production, but the potential clonal or genotypic response to increasing tropospheric carbon dioxide (CO 2 ), ozone (O 3 ), and their interactions are unknown. To study these effects, we exposed five different hybrid Populus clones to increased concentrations of CO 2 , O 3 , and CO 2 + O 3 in open-top chambers for one growing season and determined growth responses. Exposure to elevated CO 2 increased height growth, dry mass, and basal area; exposure to O 3 decreased all three of these growth responses. Exposure impact differed among the different plant parts (leaf, stem, and roots) and among the clones. These differences were associated with different growth strategies or carbon allocation patterns inherent in the different clones. The fastest growing clones had the greatest response to O 3 treatment. The addition of CO 2 to the O 3 exposure counteracted the negative impact of O 3 in all plant components except leaf mass (e.g., CO 2 + O 3 plant mass equaled control plant mass) in all of the clones. But correspondingly, added O 3 negated increased growth from CO 2 . Genetic variation in response to atmospheric pollutants must be considered even in closely related genotypes found in Populus culture.