Mathematical growth analysis techniques were used to assess the possible interactive effects of atmospheric carbon dioxide enrichment and water stress on growth and biomass partitioning of Liquidambar styraciflua L. (sweetgum) and Pinus taeda L. (loblolly pine) seedlings. Plants were grown from seed under 1000 μmol∙m−2∙s−1 photosynthetic photon flux density at CO2 concentrations of 350, 675, and 1000 μL∙L−1 for 56 days. At this time, half the seedlings in each CO2 treatment had water withheld until plant water potentials reached about −2.5 MPa in the most stressed plants, while the remaining plants were well watered. At the end of the drying cycle, stressed plants were returned to well-watered conditions for a 14-day recovery period. The greatest effects of water stress on growth were seen following the recovery period and were most severe for sweetgum seedlings grown at the lowest CO2 concentration. For sweetgum seedlings in particular, the reduction of early seedling growth following exposure to a period of drought under normal atmospheric CO2 concentration was ameliorated by growing plants under elevated CO2, primarily because of maintenance of greater net assimilation rates following a period of stress. The data presented here suggest that a doubling of atmospheric CO2 concentration would enable sweetgum seedlings to become established in drier sites which are currently dominated by loblolly pine seedlings.
Assimilation, Distribution, and Root Exudation of 14C by Ponderosa Pine Seedlings under Induced Water Stress