Poster: Global Change
Abs #
57: Altered photosynthesis and biomass production by soybean grown in future O3 concentrations under open-air field conditions.
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Presenter: |
Morgan, Patrick B, patrickm@life.uiuc.edu |
Authors | Morgan, Patrick B (A) Bernacchi, Carl J (B) Bollero, German A (C) Long, Stephen P (A) (C) | | Affiliations: |
(A): Department of Plant Biology, University of Illinois
(B): United States Department of Agriculture/Agricultural Research Service
(C): Department of Crop Sciences, University of Illinois
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| Web Site: | http://www.soyface.uiuc.edu | |
Rising atmospheric carbon dioxide concentration ([CO2]) is well accepted, but less well publicized is the concomitant rise in tropospheric ozone concentration ([O3]). In industrialized countries, [O3] has risen by 0.5-2.5% per year (more rapidly than [CO2]) and is predicted to reach a global mean of 63 ppb by 2030 with greater averages locally (UN-IPCC, 2001). We expect decreased photosynthesis caused by elevated [O3] will severely limit growth and yield in soybean. SoyFACE (Soybean Free Air Concentration Enrichment, www.soyface.uiuc.edu) is the first facility to elevate atmospheric [O3] (1.21 x ambient) in replicated plots under open-air conditions within an agricultural field. Simultaneous measurements of fluorescence and gas-exchange (assimilation vs. light and assimilation vs. intercellular [CO2]) were made on excised leaves. In the topmost fully-expanded leaf, growth in elevated [O3] did not alter light-saturated photosynthesis (Asat, p=0.14), carboxylation capacity (Vc,max, p=0.81) or maximum electron transport (Jmax, p=0.65) at any developmental stage. However, as leaves aged, elevated [O3] caused a progressive and significant decrease in all three measurements of photosynthetic capacity. These ozone-induced decrease drove the 22% decrease (240 g/m2, p=0.007) in dry-matter production and the 20% loss (143 g/m2, p=0.022) in reproductive yield. Assuming that [O3] rises linearly, our measured biomass losses suggests that predicted rises in [O3] over the next 30 yrs would increase annual crop losses by $21 million/year in the US based on 2002 production. Since ozone-induced losses directly result from decreased photosynthesis, these findings emphasize the need to discover means of protecting the photosynthetic apparatus against damage both for the future and today.
