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United States Department of Agriculture

Agricultural Research Service

Research Project: GLOBAL CHANGE AND BELOWGROUND PROCESSES IN AGRICULTURAL SYSTEMS Title: Effects of elevated atmospheric CO2 on a C3 and a C4 invasive weed

Authors
item Runion, George
item Price, Andrew
item Prior, Stephen
item Rogers Jr, Hugo
item Torbert, Henry
item Gjerstad, Dean - AUBURN UNIVERSITY

Submitted to: Botany Research Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 12, 2008
Publication Date: December 15, 2008
Citation: Runion, G.B., Price, A.J., Prior, S.A., Rogers Jr, H.H., Torbert III, H.A., Gjerstad, D.H. Effects of elevated atmospheric CO2 on a C3 and a C4 invasive weed. Botany Research Journal. 1(3):56-62.

Interpretive Summary: Loss of plant productivity and increases in weed control measures are estimated to cost U.S. agricultural and forest producers billion of dollars each year. One neglected aspect of global environmental change is how invasive plants might react to the rise in atmospheric CO2 level. Since elevated CO2 often stimulates plant growth, we studied CO2 effects on two invasive weeds (sicklepod and Johnsongrass) common to Southeast farms. This work indicated that high CO2 increased growth of both weeds, but this increase was greatest for sicklepod. However, seed production was lower or slower under high CO2 which might affect spread of these weeds in the future.

Technical Abstract: Invasive plants have become a serious problem during the past several decades, are a major threat to the Earth's biodiversity, and are estimated to cost U.S. agricultural and forest producers 34 billion dollars each year. Understanding how increased atmospheric CO2 may alter establishment, spread, and control of invasive weeds will be crucial to future management strategies. This study was conducted to determine the effects of elevated CO2 on growth of two invasive weeds of critical importance to agriculture in the Southeastern U.S. Sicklepod (Cassia obtusifolia L;C3 legume.) and Johnsongrass [Sorghum halepense (L.) Pers.; C4 grass], growing in 10.65 L containers, were placed in open top field chambers and grown at either 375 µmol mol-1 (ambient) or 575 µmol mol-1 (elevated) CO2. Measurements of photosynthesis, plant morphology, and biomass were assessed for both species. Growth in elevated CO2 increased photosynthetic rate (µmol CO2 m-2 s-1) and water use efficiency (mmol CO2 mol-1 H2O) for both species (34% and 47% for Johnsongrass vs. 43% and 59% for sicklepod for these two measurements, respectively). While both species increased leaf and stem dry weights when grown under elevated CO2 conditions, the response of sicklepod to high CO2 was greater than that for Johnsongrass. Both plants tended to partition less total dry weight to reproductive structures when grown under high CO2; however, for sicklepod, this may have merely represented a delay in reproductive development. This study suggests that, while both weeds are likely to increase in importance, sicklepod may be more of a problem than Johnsongrass in a future CO2-enriched world; this prediction may change if reproductive success is negatively impacted by elevated atmospheric CO2 and this potential certainly deserves further investigation.

Last Modified: 11/26/2014
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