ARS | Publication request: TEMPERATURE AND CO2 EFFECTS ON GAMAGRASS: PHOTOSYNTHETIC PERFORMANCE

Submitted to: Eastern Native Grass Symposium
Publication Type: Proceedings/Symposium
Publication Acceptance Date: July 3, 2003
Publication Date: October 21, 2004
Citation: GITZ, D.C., RITCHIE, J.C., KIRZEK, D.T., BAKER, J.T., REDDY, V.R. 2004. PROCEEDINGS OF THE THIRD EASTERN NATIVE GRASS SYMPOSIUM, THE NORTH CAROLINA BOTANICAL GARDEN, CHAPEL HILL, NC, OCT 1-3, 2002. OMNIPRESS, MADISON, WI. P. 203-210.

Interpretive Summary: Eastern gamagrass is a warm season perennial C4 bunchgrass native to the Americas. It is also of interest as a potential forage plant because it can be grown on a range of soils and is tolerant to drought and flooding. On the basis of how well its leaves can absorb carbon dioxide, eastern gamagrass is one of the most productive species known. We investigated how gamagrass would respond to high carbon dioxide and high temperature, conditions associated with global warming. We found that gamagrass responded extremely well to high temperature, but was relatively insensitive to carbon dioxide level. These results will be of interest to scientists studying adaptation of plants to high temperatures.

Technical Abstract: Eastern gamagrass [Tripsacum dactyloides (L.) L.] was grown in large 1 m3 bins on a sand:vermiculite mix with regular application of a complete nutrient solution in closed sunlit chambers (Soil Plant Atmosphere Research (SPAR) chambers) at 370 or 740 PPM CO2 and 20/14 C, 27.5/21.5 C or 35/29 C day/night temperatures. Plants were allowed to develop from mid-May to mid-October. Leaf and canopy photosynthesis were investigated. Results from leaf based observations were consistent with canopy level observations. Temperature effects on assimilation were much more pronounced than CO2 effects. Increased temperatures led to increased maximal assimilation rates and increased quantum use efficiencies (as Fv/Fm and CO2 assimilation vs PAR). In plants grown at lowest temperature the maximum rate of carbon assimilation was reached at relatively low PAR flux densities (1500 micro mol m-2 s-1 PAR) as compared to high temperature plants (2500 micro mol m-2 s-1). We found no conclusive evidence of a CO2 effect on carbon assimilation in these plants.