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191444 
Journal Article 
How does elevated CO2 or ozone affect the leaf-area index of soybean when applied independently? 
Dermody, O; Long, SP; DeLucia, EH 
2006 
New Phytologist
ISSN: 0028-646X
EISSN: 1469-8137 
169 
145-155 
Changes in leaf-area index (LAI) may alter ecosystem productivity in elevated [CO2] or [O-3]. By increasing the apparent quantum yield of photosynthesis (phi(c,max)), elevated [CO2] may increase maximum LAI. However, [O-3] when elevated independently accelerates senescence and may reduce LAI. Large plots (20 m diameter) of soybean (Glycine max) were exposed to ambient (approx. 370 mu mol mol(-1)) or elevated (approx. 550 mu mol mol(-1)) CO2 or 1.2 times ambient [O-3] using soybean free-air concentration enrichment (SoyFACE). In 2001 elevated CO2 had no detectable effect on maximum LAI, but in 2002 maximum LAI increased by 10% relative to ambient air. Elevated [CO2] also increased the phi(c,max) of shade leaves in both years. Elevated [CO2] delayed LAI loss to senescence by approx. 54% and also increased leaf-area duration. Elevated [O-3] accelerated senescence, reducing LAI by 40% near the end of the growing season. No effect of elevated [O-3] on photosynthesis was detected. Elevated [CO2] or [O-3] affected LAI primarily by altering the rate of senescence; knowledge of this may aid in optimizing future soybean productivity. 
NAAQS
• ISA-Ozone (2012)
     Considered
     Eco/Welfare
 

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