ACORN MASS AND SEEDLING GROWTH IN QUERCUS-RUBRA IN RESPONSE TO ELEVATED CO2

In order to explore whether seed size affects plant response to elevat ed CO2 plants grown from red oak (Quercus rubra L.) acorns were studie d for differences in their first year response to CO2 concentrations o f 350 and 700 ul/l. Overall, at final harvest, total biomass of plants grown in elevated CO2 were 47 % larger than that of plants grown in a mbient 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 ini tial 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, an d root weight ratios, and leaf area ratio. These results suggest that variation in seed size or initial plant size can cause intraspecific v ariation in response to elevated CO2.