Date of Award:


Document Type:


Degree Name:

Master of Science (MS)


Plants, Soils, and Climate

Department name when degree awarded

Plants, Soils, and Biometeorology

Committee Chair(s)

Bruce Bugbee


Bruce Bugbee


Larry Rupp


V. Philip Rasmussen


This research was conducted to quantify short- and long-term effects of atmospheric carbon dioxide on wheat. Growth, development, and yield of the spring wheat cultivar Veery-10 were measured in response to CO2 concentrations of 340 (ambient), 1200, and 2500 μmol moI-1 of CO2 air. These 3 CO2 levels were chosen to provide a control group, a predicted optimal CO2 environment, and a potentially toxic CO2environment, respectively. A recirculating hydroponic system provided a near-optimal root-zone environment that was identical for all CO2 treatment levels. Environmental factors, other than CO2, were controlled at near optimal levels, although photosynthetic photon flux was actually suboptimal and higher levels would increase growth. Standard growth analysis procedures were used to measure growth rates and carbon partitioning to leaves, stems, and roots. Yield components were measured on mature plants. Because elevated CO2 levels may increase growth by increasing radiation absorption or by increasing photosynthetic efficiency, measurements of absorbed photosynthetic photon flux were calculated from measurements of incident, reflected, and transmitted photosynthetic photon flux. Growth and yield were increased by the 1200 μmol moI-1 of CO2 in air treatment in all trials. Growth and yield were reduced by the 2500 μmol moI-1 treatment in both long-term trials, but growth was not reduced by this treatment in two short-term trials. These data indicate that CO2 is toxic to wheat at 2500 μmol moI-1 (0.25%), but the effects are not expressed until the last half of the life cycle.