Acorn mass and seedling growth in Quercus rubra in response to elevated CO2

Abstract. In order to explore whether seed size affects plant response to elevated CO₂, plants grown from red oak (Quercus rubra L.) acorns were studied for differences in their first year response to CO₂ concentrations of 350 and 700 μl/l. Overall, at final harvest, total biomass of plants grown in elevated CO₂ were 47 % larger than that of plants grown in ambient CO₂. There were significant interactions between CO₂ treatments and initial acorn mass for total biomass, as well as for root, leaf, and stem biomass. Although total biomass increased with increasing initial acorn mass for both high and ambient CO₂ plants, high CO₂ plants exhibited a greater increase than ambient CO₂ plants, as indicated by a steeper slope in high CO₂ plants. However, CO₂ levels did not affect biomass partitioning traits, such as root/shoot ratio, leaf, stem, and root weight ratios, and leaf area ratio. These results suggest that variation in seed size or initial plant size can cause intraspecific variation in response to elevated CO₂.