Dohleman, Frank G. , Wang, Dafu , Heaton, Emily A. , Leakey, Andrew D.B. , Long, Stephen P. .
Does increased daily carbon assimilation coupled with a higher Leaf Area Index and longer growing season explain the difference in productivity between two potential bioenergy crops?
An economically and energetically favorable bioenergy crop must be able to produce large quantities of biomass with minimal inputs. The C4 perennial grasses switchgrass (Panicum virgatum) and Miscanthus (Miscanthus x giganteus) have been widely trialed as low-input bioenergy crops, in the US and EU, respectively. Until now their productivity has not been directly compared. In trials across Illinois, Miscanthus was more than twice as productive as switchgrass, and its efficiency of conversion of sunlight into biomass was amongst the highest ever recorded. Understanding why Miscanthus is more productive will indicate how other potential bioenergy crops might be engineered to increase productivity. We hypothesize that there are three physiological attributes which allow greater biomass accumulation in Miscanthus compared to switchgrass. First, daily photosynthetic carbon gain per unit leaf area (A’) will be higher in Miscanthus, second, the Leaf Area Index (LAI) for Miscanthus will be greater, and third, Miscanthus will have a longer growing season. We measured productivity in a completely randomized field trial (n=4) of these two energy crops. The diurnal course of gas exchange was measured in situ on upper canopy leaves of each crop on twenty dates throughout the 2005 and 2006 growing seasons. A’ was estimated by integrating over the diurnal course of CO2 assimilation. When averaged over the two years, A’ of Miscanthus was 48% greater than in switchgrass (p<0.0001). Further, average LAI was 45% greater for Miscanthus than switchgrass (p<0.0001). Finally, the Miscanthus growing season was on average 10 days longer than that of switchgrass. The longer growing season partially attributes to its high photosynthetic performance at low temperature. Our results showed that an increase in expression of pyruvate Pi dikinase and its low activation energy correspond to cold-tolerant C4 photosynthesis of Miscanthus.
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1 - University of Illinois at Urbana-Champaign, Plant Biology, 1201 W. Gregory Dr., 379 ERML, Urbana, IL, 61801, USA
2 - Ceres Inc., Department of Energy Crop Product Development
3 - University of Illinois, Institute for Genomic Biology
4 - University of Illinois at Urbana-Champaign, Departments of Crop Sciences and Plant Biology
Miscanthus x giganteus
Presentation Type: ASPB Minisymposium
Location: Continental A/Hilton
Date: Tuesday, July 10th, 2007
Time: 3:45 PM