Submitted to: Cellular and Molecular Biology of Soybean Biennial Conference
Publication Type: Proceedings
Publication Acceptance Date: 8/31/2002
Publication Date: 8/20/2002
Citation: LONG, S., NELSON, R.L., AINSWORTH, L., HOLLIS, K., MIES, T., MORGAN, P., NAIDU, S., ORT, D.R., WEBSTER, R., ZHU, X. ADAPTING SOYBEAN TO CURRENT AND FUTURE CHANGE IN ATMOSPHERIC COMPOSITION. DO WE NEED MORE THAN FIELD SELECTION UNDER CURRENT CONDITIONS?. CELLULAR AND MOLECULAR BIOLOGY OF SOYBEAN BIENNIAL CONFERENCE. 2002. p. 401. Interpretive Summary:
Technical Abstract: Carbon dioxide is rising at about 0.4 percent per year. In 1900, levels were about 290 parts per million (ppm), in 2000 they were 370 ppm, and by 2050 they will be about 550 ppm. Carbon dioxide has the potential to increase plant production by inhibiting the wasteful process of photo respiration. By decreasing photo respiration, the increase in CO2 to date theoretically has had the potential to increase production of C3 crops, including soybeans, by 20 percent. However, there is little evidence that plant breeding has selected lines capable of realizing this potential. Our review of studies on soybean responses to elevated CO2 show, that while significant increases in biomass production are limited by a loss of photo synthetic capacity. Increase in grain yields is yet further limited by a decrease in harvest indexes. Furthermore, analysis of Rubisco suggests that it is optimized to the pre industrial CO2 concentration, and is becoming increasingly inefficient as CO2 levels rise. Engineering a form optimized to current and future conditions would significantly improve nitrogen use. Ozone is a secondary pollutant that is formed a few to 1000 miles downwind of release of nitrogen oxides (NOx), mainly from fossil fuel combustion. Ozone has risen by about 1 percent per year in the northern temperate zone. Although ozone pollution in cities has received much attention, concentrations are often higher in the surrounding rural areas. Of the major crop plants, the soybean is the most vulnerable to ozone. A peak daily level of 40 ppb (parts per billion) is sufficient to significantly decrease yields, yet average summer levels in central Illinois are 60 ppb and can exceed 100 ppb. Depending on weather conditions, ozone concentrations fluctuate greatly from year to year, impairing the potential for selecting more tolerant cultivars in simple field selection. This may explain the lack of any apparent difference in the tolerance of old and recent cultivars. Further, plants grown in greenhouse and other sheltered conditions often respond differently to plants grown in the open. Selection and mechanistic understanding therefore require a facility where elevated levels can be maintained every year in the open SoyFACE. An open-air computer-controlled field-exposure system has been developed at the University of Illinois. This releases CO2 or/and ozone according to wind speed and direction to maintain elevation of these gases within 12 replicated 1200 ft2 plots. Within these, the effects of these gases on a range of genotypes are being assessed. Variation in responses of genotypes and insights into mechanisms of response, observed to date, will be presented.