Article,
How does elevated CO2 or ozone affect the leaf-area index of soybean when applied independently?
The New phytologist, 169 (1): 145--155 (January 2006)
DOI: 10.1111/j.1469-8137.2005.01565.x
Abstract
Changes in leaf-area index (LAI) may alter ecosystem productivity in elevated CO2 or O3. By increasing the apparent quantum yield of photosynthesis (phi(c,max)), elevated CO2 may increase maximum LAI. However, O3 when elevated independently accelerates senescence and may reduce LAI. Large plots (20 m diameter) of soybean (Glycine max) were exposed to ambient (approx. 370 micromol mol(-1)) or elevated (approx. 550 micromol mol(-1)) CO2 or 1.2 times ambient O3 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 O3 accelerated senescence, reducing LAI by 40\% near the end of the growing season. No effect of elevated O3 on photosynthesis was detected. Elevated CO2 or O3 affected LAI primarily by altering the rate of senescence; knowledge of this may aid in optimizing future soybean productivity.
