THE EFFECTS OF SULFUR-DIOXIDE AND SELECTED NUTRIENT SOLUTIONS UPON WESTERN WHEATGRASS

Sulfur dioxide is a key component of emissions from coal burning power plants. The effect of SO(,2) upon dominant vegetation in the northern mixed prairie, an area in which production and burning of coal are expected to expand, is of considerable importance. Western wheatgrass plants (Agropyron smithii Rydb.) were maintained in nutrient solutions and exposed to different atmospheric concentrations of SO(,2) and root medium concentrations of sulfate (SO(,4)('=)) in field experiments. Plants were analyzed at three levels of organization: segments of leaf blades, fully expanded leaf blades and tillers. There were substantial gradients of increasing sulfur concentration from the bases to the tips of individual leaf blades. There was also a general increase in sulfur concentration from the youngest to the oldest leaf blade. Differences in sulfur concentration of leaf blade segments and leaf blades were not strongly related to SO(,2) concentration. The sulfur concentration of entire shoot systems, however, increased linearly from 9 through 105 (mu)g (.) m('-3) SO(,2) and then declined slightly at the highest concentration (183 (mu)g (.) m('-3)). Elevated water use with exposure to SO(,2) indirectly suggested enhanced stomatal opening and uptake of SO(,2). The level of organization investigated determines the degree of measurable response to SO(,2). Further, accumulation of sulfur by western wheatgrass was not a reliable indicator of pollutant stress since the plant is relatively resistant to SO(,2) and demonstrates recognizable yet variable patterns of sulfur distribution.; The objective of the laboratory experiment was to determine the effect of sulfur nutrition on growth of western wheatgrass. Growth was only minimally affected by three nutrient solution concentrations of SO(,4)('=) (0 mM, 2 mM, and 4 mM). I suggest the importance of the pretreatment period and related sulfur reserves prior to the study to explain the apparent insensitivity of western wheatgrass during the nutrition experiment.; Based upon my work and substantial evidence from closely related studies, I concluded that the burning of coal and the maintenance of quality grassland dominated by western wheatgrass are compatible. I hypothesized that the doses of SO(,2) to which the plants were exposed were well within the range of natural stress.