Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/30/2002
Publication Date: 6/30/2004
Citation: Krizek, D.T., Gitz, D.C., Ritchie, J.C., Reddy, V. 2004. Biomass accumulation and partitioning of eastern gammagrass grown under different temperature and CO2 levels. Acta Horticulturae. 638:293-299. Interpretive Summary: Eastern gamagrass has one of the highest photosynthetic rates of any grass species, but little is known about its response to projected increases in carbon dioxide (CO2) and temperature. Seedlings were grown for 5 months in six specially designed environmentally controlled sun lit enclosures at three day/night temperatures (20/14, 27.5/21.5, or 35/29C) and ambient or twice ambient CO2 level. Temperature had a much greater effect on growth of leaves, crowns and roots than CO2. The optimum day/night temperature in our study for dry matter accumulation in the leaves was 35/29 C but 27.5/21.5 C for the crowns and roots. Plants grown at warm temperatures grew rapidly and produced nearly twice the biomass of plants grown at cool temperature. Although field-grown plants are not typically harvested until the second year from seeding, plants grown under our optimum conditions produced three cuttings in only five months from planting. Doubling the CO2 level had only a modest effect on biomass accumulation over a single growing season and this was largely confined to the leaves and crowns. Increasing CO2 failed to increase biomass accumulation in the roots. Since there is a potential for a cumulative response to carbon dioxide with time, further studies are needed to determine the long-term effects of carbon dioxide enhancement at realistic levels projected to occur in the future. These findings provide the first information on carbon dioxide x temperature interactions in this important warm season grass and demonstrate that under optimum conditions, plants are capable of producing a crop ready to harvest in only a fraction of the time observed in nature. This information will be useful to policy makers, scientists, and specialists interested in rapid growth rates and their response to global change
Technical Abstract: Eastern gamagrass has been reported to have one of the highest photosynthetic rates of any C4 species but data on temperature x CO2 interactions are lacking. This study was conducted to determine the potential effects of future increases of atmospheric carbon dioxide on growth, biomass accumulation and root/shoot carbon allocation under three day/night temperatures and two CO2 levels. Eastern gamagrass (cv. Pete) plants were grown in 1 m3 soil bins containing sand:vermiculite (1:1), fertilized weekly with a complete nutrient solution in closed, transparent SPAR (Soil, Plant, Atmospheric Research) chambers maintained at 370 or 740 umol/mol CO2 and 20/14, 27.5/21.5 or 35/29 C day/night temperatures, and allowed to develop from mid-May to mid-October. Three harvests were taken during this period. Leaves were collected during the first two harvests. During the final harvest, leaves, crowns, and roots were collected from each individual plant. The optimum day/night temperature in our study for biomass accumulation in the leaves (35/29 C) was higher than that for the crowns and roots (27.5/21.5 C). Biomass accumulation in leaves increased two-fold over the entire temperature range. Temperature had a greater effect on vegetative growth than CO2. CO2 enhanced biomass accumulation was modest, restricted to leaves, and observed only at higher temperatures and later in development. Under optimum soil moisture conditions in the SPAR chambers, high amounts of carbon were captured in the above ground biomass for potential later incorporation into soil. This study demonstrates the potential of eastern gamagrass to capture carbon for sequestration.