Response of 25-day old Eucalyptus globulus to elevated CO2

Increasing [CO2] may influence commercial crop and timber yield. While selection of genotypes sensitive to elevated [CO2] (e[CO2]) appears possible in agricultural crops, there is limited evidence for genotype-by-CO2 (G×CO2) interactions in commercial tree species. We examined [CO2] responsiveness in 124 open-pollinated Eucalyptus globulus subspecies globulus (E. globulus) families with the aim of assessing whether G×CO2 interactions are detectable in seedlings for early-age screening. Plants were grown in ambient (a[CO2]; ~405 μmol mol-1) and e[CO2] (640 μmol mol-1) and harvested 25 days after germination. Total, shoot and root dry weights were determined for each plant. Carbon isotopic discrimination against 13C (Δ13C) was determined at the family level. We observed highly significant (p<0.0001) increases in mean total, shoot, and root dry weights. Mixed-model equations were used to estimate the main and interaction effects of the G×CO2 for each mass trait. The main effects from th...