COS 121-7 - Carbon gain, allocation, and storage in rhizomes in response to elevated CO2 and fertilization in an invasive perennial C3 grass, Phalaris arundinacea

Thursday, August 11, 2011: 3:40 PM
19A, Austin Convention Center
Hannah Kinmonth-Schultz, Biology, University of Washington and Soo-Hyung Kim, School of Environmental and Forest Sciences, University of Washington, Seattle, WA
Background/Question/Methods

Reed canary grass (Phalaris arundinacea L.) is a fast-growing, perennial, rhizomatous, C3 grass considered as a model invasive species for its aggressive weedy behavior in many parts of the world, including the United States. Conversely, the same traits make it a candidate for bioenergy feedstock elsewhere. We tested the hypothesis that elevated CO2 and fertilization promote the growth of this fructan accumulating cool-season grass with little or no photosynthetic down-regulation. We also tested whether elevated CO2 and nutrient availability alters fructan storage in rhizomes. Plants were grown at ambient or elevated (+320 μmol mol-1) CO2, and fertilized using full- or 1/8th-strength Hoagland’s solution. The experiment was repeated in summer and fall. We investigated leaf photosynthesis, whole-plant water use, biomass allocation, and nitrogen and carbon storage in rhizomes. 

Results/Conclusions

Elevated CO2 enhanced light-saturated net CO2 assimilation (Amax) by 61%. It doubled whole-plant, stem, and root biomass in summer. Plants grown in elevated CO2 assimilated carbon more efficiently at higher CO2 concentrations than those grown in ambient CO2. This response indicates an acclamatory shift for enhanced carbon gain under elevated CO2. In fall, fructan in rhizomes increased from 5.64% under ambient CO2 to 7.76% under elevated CO2 (P=0.054). Our results support that elevated CO2 combined with sufficient nutrients is likely to enhance carbon gain and growth of the species with little down-regulation and to increase productivity and competitiveness of Phalaris arundinacea in summer. Elevated CO2 is also likely to enhance long-term fructan storage in rhizomes in fall. This response may benefit overwintering and early sprouting.

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