
%0 Journal Article
%A Ziska, Lewis H. 
%A Teasdale, John R. 
%T Sustained growth and increased tolerance to glyphosate observed in a C<sub>3</sub> perennial weed, quackgrass (<i>Elytrigia repens</i>), grown at elevated carbon dioxide
%J Functional Plant Biology
%D 2000/02/09
%V 27
%N 2
%P 159-166
%K climate change, CO2 concentration, glyphosate, quackgrass, tolerance.
%R https://doi.org/10.1071/PP99099
%U https://www.publish.csiro.au/paper/PP99099 
%X Although the response of crop plants to rising atmospheric carbon dioxide concentration ([CO2]) has been well characterized, little is known concerning the long-term growth and/or photosynthetic response of peren-nial weeds. The growth and photosynthetic characteristics of three cohorts of a perennial C3 weedy species, quack-grass (Elytrigia repens (L.) Nevski) were examined at ~380 &#xb5;mol mol&#x2212;1 (ambient) and 720 &#xb5;mol mol&#x2212;1 (elevated) [CO2] in temperature-controlled greenhouses during 1998 and early 1999. Different cohorts were used to assess the sensitivity of growth, photosynthesis and glyphosate tolerance to elevated [CO2] for different stages in the life cycle of quackgrass. For the &#x2018;old&#x2019; cohort, planted on Day of Year (DOY) 187, elevated [CO2] resulted in a consistent stim-ulation of single leaf photosynthesis, vegetative and whole plant biomass relative to the ambient [CO2] condition over a 231-d period. Data from the &#x2018;intermediate&#x2019; (DOY 268) and &#x2018;young&#x2019; cohorts (DOY 350) indicated that the stimula-tion of biomass at the elevated [CO2] was time-dependent. To determine if the observed stimulation of growth at ele-vated [CO2] altered tolerance to chemical weed control, glyphosate [(N-phosphonomethyl)glycine] was applied to each cohort and each [CO2] treatment at rates of 0 (control) and 2.24 kg ai ha&#x2212;1 (sprayed). Tolerance was determined by following the growth and slope of each cohort at the growth [CO2] treatment for a 28-d period following glyphosate application. For the young cohort, [CO2] had no affect on glyphosate tolerance; however, an application rate of 2.24 kg ai ha&#x2212;1, reduced but did not eliminate growth for the intermediate and old cohorts grown at elevated [CO2]. The basis for increased glyphosate tolerance at elevated [CO2] for these cohorts was unclear, but was not related to plant size at the time of glyphosate application. Data from this experiment indicate that sustained stimula-tion of photosynthesis and growth in perennial weeds could occur as atmospheric [CO2] increases, with a reduction in chemical control effectiveness and potential increases in weed/crop competition. 
