Varied Growth Response of Cogongrass Ecotypes to Elevated CO(2)

Cogongrass [Imperata cylindrica (L.) P. Beauv] is an invasive C(4) perennial grass which is listed as one of the top ten worst weeds in the world and is a major problem in the Southeast US. Five cogongrass ecotypes [Florida (FL), Hybrid (HY), Louisiana (LA), Mobile (MB), and North Alabama (NA)] collected across the Southeast and a red-tip (RT) ornamental variety were container grown for 6 months in open top chambers under ambient and elevated (ambient plus 200 ppm) atmospheric CO(2). Elevated CO(2) increased average dry weight (13%) which is typical for grasses. Elevated CO(2) increased height growth and both nitrogen and water use efficiencies, but lowered tissue nitrogen concentration; again, these are typical plant responses to elevated CO(2). The HY ecotype tended to exhibit the greatest growth (followed by LA, NA, and FL ecotypes) whiles the RT and MB ecotypes were smallest. Interactions of CO(2) with ecotype generally showed that the HY, LA, FL, and/or NA ecotypes showed a positive response to CO(2) while the MB and RT ecotypes did not. Cogongrass is a problematic invasive weed in the southeastern U.S. and some ecotypes may become more so as atmospheric CO(2) continues to rise.