@article{booker_burkey_pursley_heagle_2007, title={Elevated carbon dioxide and ozone effects on peanut: I. Gas-exchange, biomass, and leaf chemistry}, volume={47}, ISSN={["1435-0653"]}, DOI={10.2135/cropsci2006.08.0537}, abstractNote={The effects of elevated CO2 and ozone (O3) on net photosynthetic rate (A) and growth are generally antagonistic although plant responses are highly dependent on crop sensitivity to the individual gases and their concentrations. In this experiment, we evaluated the effects of various CO2 and O3 mixtures on leaf gas‐exchange, harvest biomass, and leaf chemistry in peanut (Arachis hypogaea L.), an O3–sensitive species, using open‐top field chambers. Treatments included ambient CO2 (about 375 μmol mol−1) and CO2 enrichment of approximately 173 and 355 μmol mol−1 in combination with charcoal‐filtered air (22 nmol O3 mol−1), nonfiltered air (46 nmol O3 mol−1), and nonfiltered air plus O3 (75 nmol O3 mol−1). Twice‐ambient CO2 in charcoal‐filtered air increased A by 23% while decreasing seasonal stomatal conductance (gs) by 42%. Harvest biomass was increased 12 to 15% by elevated CO2 In ambient CO2, nonfiltered air and added O3 lowered A by 21% and 48%, respectively, while added O3 reduced gs by 18%. Biomass was not significantly affected by nonfiltered air, but was 40% lower in the added O3 treatment. Elevated CO2 generally suppressed inhibitory effects of O3 on A and harvest biomass. Leaf starch concentration was increased by elevated CO2 and decreased by O3 Treatment effects on foliar N and total phenolic concentrations were minor. Increasing atmospheric CO2 concentrations should attenuate detrimental effects of ambient O3 and promote growth in peanut but its effectiveness declines with increasing O3 concentrations.}, number={4}, journal={CROP SCIENCE}, author={Booker, Fitzgerald L. and Burkey, Kent O. and Pursley, Walter A. and Heagle, Allen S.}, year={2007}, pages={1475–1487} }
 @article{burkey_booker_pursley_heagle_2007, title={Elevated carbon dioxide and ozone effects on peanut: II. Seed yield and quality}, volume={47}, ISSN={["1435-0653"]}, DOI={10.2135/cropsci2006.08.0538}, abstractNote={Many adverse effects of tropospheric O3 on C3 crop plants are ameliorated by elevated concentrations of atmospheric CO2, but the extent of the interaction can vary, depending on the species, gas concentrations, and other experimental conditions. A 2‐yr open‐top field chamber experiment was conducted to examine this interaction in peanut (Arachis hypogaea L.) by testing the effects of O3 and CO2 mixtures on yield and seed quality. Treatments were ambient CO2 (375 μmol mol−1) and CO2 additions of approximately 173 and 355 μmol mol−1 in combination with charcoal‐filtered (CF) air (22 nmol O3 mol−1), nonfiltered (NF) air (46 nmol O3 mol−1), and NF air plus O3 (75 nmol O3 mol−1). At ambient CO2, pod number was suppressed 16% in NF air and 44% in elevated O3 Pod and seed mass were not significantly affected in NF air but were lowered 33 to 37% in elevated O3 Elevated CO2 increased yield parameters 7 to 17% for plants grown in CF air and restored yield in NF air and elevated O3 treatments to control or higher levels. Gas treatment effects on peanut market grade characteristics were small. No treatment effects were observed on the protein and oil contents of seeds, but there were changes in fatty acid composition. Overall results indicate that increasing concentrations of tropospheric O3 will suppress yield of O3–sensitive peanut cultivars, while elevated CO2 will moderate this response. Elevated O3 and CO2 are not expected to have major effects on peanut seed composition and quality.}, number={4}, journal={CROP SCIENCE}, author={Burkey, Kent O. and Booker, Fitzgerald L. and Pursley, Walter A. and Heagle, Allen S.}, year={2007}, pages={1488–1497} }
 @article{booker_miller_fiscus_pursley_stefanski_2005, title={Comparative responses of container- versus ground-grown soybean to elevated carbon dioxide and ozone}, volume={45}, ISSN={["1435-0653"]}, DOI={10.2135/cropsci2004.0198}, abstractNote={In studies of CO2–enrichment effects on plants, the applicability of results derived from experiments using container‐grown plants for predictions of future crop performance in a CO2–enriched atmosphere has been questioned. Concerns also have been expressed about plant growth studies with the air pollutant O3 in pot‐grown plants. Further, since elevated CO2 and O3 co‐occur, studies are required with the combination of gases. In this 2‐yr experiment, soybean [Glycine max (L.) Merr.] plants grown in large pots (15 and 21 L) and in the ground were exposed to mixtures of CO2 and O3 in open‐top chambers. The CO2 treatments were ambient and CO2 enrichment of approximately 337 μmol mol−1 added 24 h d−1 Ozone treatments were charcoal‐filtered (CF) air (23 nmol mol−1) and approximately 1.5 times ambient O3 levels (71 nmol mol−1) given 12 h d−1 Relative effects of elevated CO2 and O3 on aboveground biomass and seed yield were quite similar for plants grown in pots compared with plants grown in the ground. Elevated CO2 increased total seed mass and O3 suppressed it to similar magnitudes in both rooting environments. Elevated CO2 also reduced the toxic effects of O3 Net photosynthesis (A) was similar while stomatal conductance (gs) was higher in pot‐grown compared with ground‐grown plants, possibly due to better soil moisture status. The results indicated that planting density and rooting environment affected plant morphology, but relative responses of seed yield to elevated CO2 and O3 were not fundamentally different between soybean plants grown in large pots and in the ground in open‐top chambers.}, number={3}, journal={CROP SCIENCE}, author={Booker, FL and Miller, JE and Fiscus, EL and Pursley, WA and Stefanski, LA}, year={2005}, pages={883–895} }
 @article{booker_prior_torbert_fiscus_pursley_hu_2005, title={Decomposition of soybean grown under elevated concentrations of CO2 and O-3}, volume={11}, DOI={10.1111/j.1365.2486.2005.00939.x}, number={4}, journal={Global Change Biology}, author={Booker, F. L. and Prior, S. A. and Torbert, H. A. and Fiscus, E. L. and Pursley, W. A. and Hu, Shuijin}, year={2005}, pages={685–698} }
 @article{heagle_miller_pursley_2003, title={Growth and yield responses of potato to mixtures of carbon dioxide and ozone}, volume={32}, ISSN={["0047-2425"]}, DOI={10.2134/jeq2003.1603}, abstractNote={ABSTRACT}, number={5}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={Heagle, AS and Miller, JE and Pursley, WA}, year={2003}, pages={1603–1610} }
 @article{heagle_miller_burkey_eason_pursley_2002, title={Growth and yield responses of snap bean to mixtures of carbon dioxide and ozone}, volume={31}, ISSN={["1537-2537"]}, DOI={10.2134/jeq2002.2008}, abstractNote={ABSTRACT}, number={6}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={Heagle, AS and Miller, JE and Burkey, KO and Eason, G and Pursley, WA}, year={2002}, pages={2008–2014} }
 @article{heagle_miller_pursley_2000, title={Growth and yield responses of winter wheat to mixtures of ozone and carbon dioxide}, volume={40}, ISSN={["0011-183X"]}, DOI={10.2135/cropsci2000.4061656x}, abstractNote={Ozone (O3) in the troposphere can cause plant stress, whereas elevated CO2 generally enhances plant growth. Until recently, few studies have considered whether O3 can affect plant response to CO2 or vice versa. We examined these possibilities for soft red winter wheat (Triticum aestivum L.). Plants were grown in 14‐L pots and exposed in open‐top field chambers to all combinations of three CO2 and three O3 treatments. The CO2 treatments were ambient (approximately 380 μL L−1), or ambient with CO2 added for 24 h d−1 to achieve mean concentrations of approximately 540, or 700 μL L−1 The O3 treatments were charcoal‐filtered air (CF), nonfiltered air (NF), or NF with O3 added for 12 h d−1 (NF+). Mean O3 concentrations in the CF, NF, and NF+ treatments were approximately 27, 45, and 90 nL L−1 In the first experiment, eight cultivars with widely different genetic backgrounds were tested. `Coker 9835' was relatively resistant to O3 and `Coker 9904' was relatively sensitive; these cultivars were tested in Exp. 2. Foliar injury caused by O3 was suppressed by elevated CO2 in both experiments. In Exp. 1, plant size and yield increased with CO2 enrichment in the NF and NF+ treatments, but not in the CF treatment. However, the O3 × CO2 interaction was rarely significant. In Exp. 2, growth and yield of C9904 was suppressed more by O3 than was that of C9835. Because of cultivar differences in sensitivity to O3, CO2 enrichment caused greater amelioration of O3 stress and greater enhancement for C9904 than for C9835. Significant cultivar × O3 × CO2 interactions occurred for all growth and yield measures. These results are similar to results with other crops, and further emphasize the need to consider possible interactions between O3 and CO2 when investigating effects of O3 or CO2 on plant systems.}, number={6}, journal={CROP SCIENCE}, author={Heagle, AS and Miller, JE and Pursley, WA}, year={2000}, pages={1656–1664} }
 @article{heagle_booker_miller_pursley_stefanski_1999, title={Influence of daily carbon dioxide exposure duration and root environment on soybean response to elevated carbon dioxide}, volume={28}, ISSN={["0047-2425"]}, DOI={10.2134/jeq1999.00472425002800020034x}, abstractNote={Abstract}, number={2}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={Heagle, AS and Booker, FL and Miller, JE and Pursley, WA and Stefanski, LA}, year={1999}, pages={666–675} }
 @article{heagle_miller_booker_pursley_1999, title={Ozone stress, carbon dioxide enrichment, and nitrogen fertility interactions in cotton}, volume={39}, ISSN={["0011-183X"]}, DOI={10.2135/cropsci1999.0011183X003900030021x}, abstractNote={Ozone (O 3 ) in the troposphere can cause plant stress leading to foliar injury and suppressed growth and yield, whereas elevated CO 2 generally enhances growth and yield. Numerous studies have been performed to determine effects of O 3 and CO 2 separately, but relatively few have been performed to determine if 03 can affect plant response to CO 2 or vice versa. Open-top field chambers were used to determine if such interactions occur for cotton (Gossypium hirsutum L.), which is relatively sensitive to O 3 . Nitrogen nutrition is especially important in cotton production so N nutrition was included as an experimental factor. Plants were grown in 14-L pots at low, medium, and high soil N levels and exposed to three CO 2 and two or three 03 treatments in all combinations during two seasons. The CO 2 treatments were ambient (370 μL L -1 ) and two treatments with CO 2 added for 24 h d -1 at approximately 1.5 and 2.0 times ambient. In 1995, the O 3 treatments were charcoal filtered air (CF), and nonfiltered air (NF) with 03 added for 12 h d -1 (NF+). In 1996, a NF treatment was also included to represent ambient 03 conditions. The CF, NF, and NF+ treatments resulted in seasonal 03 concentrations of approximately 23, 51, and 75 nL L -1 . Carbon dioxide enrichment generally stimulated growth and yield whereas 03 exposure suppressed growth and yield. Stimulation induced by CO 2 increased as O 3 stress increased. For example, in 1995 at medium N, the percentage increase in yield caused by doubling CO 2 in CF air was 0%, but was 52% in NF+ air. Comparable values for 1996 were 23% in CF air and 140% in NF+ air. These interactions occurred for a range of soil N levels, and were probably caused by CO 2 -induced prevention of 03 stress. The results emphasize the need to consider O 3 X CO 2 interactions to ensure correct interpretation of cause-effect relationships in CO 2 enrichment studies with crops that are sensitive to O 3 .}, number={3}, journal={CROP SCIENCE}, author={Heagle, AS and Miller, JE and Booker, FL and Pursley, WA}, year={1999}, pages={731–741} }
 @article{miller_heagle_pursley_1998, title={Influence of ozone stress on soybean response to carbon dioxide enrichment: II. Biomass and development}, volume={38}, ISSN={["0011-183X"]}, DOI={10.2135/cropsci1998.0011183X003800010021x}, abstractNote={Previous research has shown that elevated CO2 concentrations can increase plant growth, whereas the air pollutant O3 is phytotoxic. Because elevated concentrations of these gases will co‐occur, the objective of our experiment was to determine if estimates of plant growth response to future levels of CO2 and O3 require experiments to test the gases in combination. Soybean plants [Glycine max (L.) Merr. cv. Essex) were exposed in open‐top chambers to combinations of O3 and CO2 from plant emergence through physiological maturity. Ozone treatments were charcoal‐filtered air (CF), nonfiltered air (NF), and NF with O3 added for 12 d−1 (NF+) (seasonal mean 12 d−1 O3 concentrations of 20, 50, or 79 nL L−1, respectively). Carbon dioxide exposures were for 24 h d−1 giving seasonal mean 12 d−1 concentrations of 370, 482, 599, or 713 μL L−1. Over the season, elevated CO2 usually stimulated growth and O3 suppressed growth. Elevated CO2 usually increased partitioning of biomass to branches, decreased partitioning to pods, increased specific leaf weight, and decreased leaf area ratio. Ozone suppressed leaf and root weight ratios, increased pod weight ratios, and decreased specific leaf weight. Toward the end of the season, both O3 and CO2 accelerated reproductive development. Elevated CO2 moderated suppression of growth by O3, and the highest CO2 concentration completely ameliorated O3 effects on main stem biomass, root biomass, and leaf area. Ozone, however, limited some positive growth responses to CO2, especially at less than a doubling of CO2 concentrations. These results indicate that in order to understand the future impacts of atmospheric gases such as elevated CO2 and O3 on crop growth, their combined effects should be determined.}, number={1}, journal={CROP SCIENCE}, author={Miller, JE and Heagle, AS and Pursley, WA}, year={1998}, pages={122–128} }
 @article{miller_shafer_schoeneberger_pursley_horton_davey_1997, title={Influence of a mycorrhizal fungus and/or rhizobium on growth and biomass partitioning of subterranean clover exposed to ozone}, volume={96}, ISSN={["0049-6979"]}, DOI={10.1023/A:1026496420809}, number={1-4}, journal={WATER AIR AND SOIL POLLUTION}, author={Miller, JE and Shafer, SR and Schoeneberger, MM and Pursley, WA and Horton, SJ and Davey, CB}, year={1997}, month={May}, pages={233–248} }