Poster: Global change

Abs # 28: Effects of elevated CO₂ and Ozone on Rubisco and Rubisco Activase in soybeans

Presenter:	Ramig, Kelly M, kramig@knox.edu
Authors	Ramig, Kelly M (A)   Ewy, Robert G (A)
Affiliations:	(A): Knox College, Department of Biology

Atmospheric CO₂ levels are expected to increase 50% by the year 2050 from present levels. During this same period, ozone levels are expected to increase 20%. While plants grow better in elevated CO₂ environments, elevated O₃ levels have been shown to inhibit both plant growth and crop yield. This is especially true of soybeans, a key food crop worldwide. Previous work has shown that elevated O₃ decreases soybean dry matter and reproductive yield by at least 20%. The question then becomes will the increased levels of atmospheric CO₂ mitigate the negative effects of elevated O₃ on plant growth and yield in the future environment, particularly in crop plants? The results of studies under controlled environments suggest that elevated CO₂ levels do mitigate the effect of elevated O₃. However, these controlled environments may contribute artifacts and not allow a true determination of how elevated CO₂ may or may not mitigate the detrimental effects of elevated O₃ on soybeans. Elevated ozone decreases photosynthesis. We are interested in determining both the diurnal and seasonal variations in two key photosynthetic enzymes, Rubisco and its regulatory enzyme Rubisco Activase, in soybeans grown under field conditions with the following treatments: elevated O₃, elevated CO₂, and elevated CO₂ and O₃. Such conditions were obtained at the SoyFACE site in Champaign, Il (www.soyface.uiuc.edu) and minimize the artifacts observed in controlled environments. Protein levels for Rubisco, Rubisco Activase, as well as total soluble protein were determined from samples taken throughout the 2003 growing season. The effects of the various treatments on protein levels both throughout the day and throughout the season are compared to changes in ozone levels over the course of the growing season.