@article{burkey_miller_fiscus_2005, title={Assessment of ambient ozone effects on vegetation using snap bean as a bioindicator species}, volume={34}, ISSN={["0047-2425"]}, DOI={10.2134/jeq2004.0008}, abstractNote={Tropospheric ozone is an air pollutant that is toxic to plants, causing visible injury to foliage and a reduction in growth and yield. The use of plant bioindicators is one approach to assess the ozone impacts in diverse geographical areas. The objective of this study was to evaluate snap bean (Phaseolus vulgaris L.) as a potential bioindicator species. Three snap bean genotypes known to exhibit a range of ozone sensitivity were grown in pots under charcoal-filtered (CF) or nonfiltered (NF) treatments in open-top chambers, or under ambient air (AA) conditions. Treatment effects on biomass were not significant at 56 days after planting (DAP), but midseason foliar injury increased in the NF and AA treatments relative to CF controls. An increase in ozone from 25 to 30 nL L(-1) in CF controls to approximately 50 nL L(-1) in the NF and AA treatments was found to suppress final pod dry weight per plant by 40 to 60% in the most sensitive genotype S156. The same treatments suppressed final pod dry weight by 20 to 30% in a moderately sensitive genotype Oregon-91, and by 10% or less in a tolerant genotype R123. An S156 to R123 yield ratio of approximately one was observed under CF conditions. The S156 to R123 yield ratio declined to 0.6 to 0.7 in the NF treatment and declined further to 0.4 to 0.5 in the AA treatment, suggesting that ozone impact was underestimated in the open-top chambers. The results suggest that a snap bean bioindicator system has the potential to detect ambient ozone effects at present-day ozone concentrations.}, number={3}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={Burkey, KO and Miller, JE and Fiscus, EL}, year={2005}, pages={1081–1086} }
 @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{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={Elevated carbon dioxide (CO2) concentrations in the atmosphere can stimulate plant growth and yield, whereas ground-level ozone (O3) concentrations cause the opposite effect in many areas of the world. Recent experiments show that elevated CO2 can protect some plants from O3 stress, but this has not been tested for most crop species. Our objective was to determine if elevated CO2 protects Irish potato (Solanum tuberosum L.) from foliar injury and suppression of growth and yield caused by O3. An O3-resistant cultivar (Superior) and an O3-sensitive cultivar (Dark Red Norland) were exposed from within 10 d after emergence to maturity to mixtures of three CO2 and three O3 treatments in open-top field chambers. The three CO2 treatments were ambient (370 microL L(-1)) and two treatments with CO2 added to ambient CO2 for 24 h d(-1) (540 and 715 microL L(-1)). The O3 treatments were charcoal-filtered air (15 nL L(-1)), nonfiltered air (45 nL L(-1)), and nonfiltered air with O3 added for 12 h d(-1) (80 nL L(-1)). Elevated O3 and CO2 caused extensive foliar injury of Dark Red Norland, but caused only slight injury of Superior. Elevated CO2 increased growth and tuber yield of both cultivars, whereas elevated O3 generally suppressed growth and yield, mainly of Dark Red Norland. Elevated CO2 appeared to protect Dark Red Norland from O3-induced suppression of shoot, root, and tuber weight as measured at midseason but did not protect either cultivar from O3 stress at the final harvest. The results further illustrate the difficulty in predicting effects of O3 + CO2 mixtures based on the effects of the individual gases.}, 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={Elevated CO2 concentrations expected in the 21st century can stimulate plant growth and yield, whereas tropospheric O3 suppresses plant growth and yield in many areas of the world. Recent experiments showed that elevated CO2 often protects plants from O3 stress, but this has not been tested for many important crop species including snap bean (Phaseolus vulgaris L.). The objective of this study was to determine if elevated CO2 protects snap bean from O3 stress. An O3-tolerant cultivar (Tenderette) and an O3-sensitive selection (S156) were exposed from shortly after emergence to maturity to mixtures of CO2 and O3 in open-top field chambers. The two CO2 treatments were ambient and ambient with CO2 added for 24 h d(-1) resulting in seasonal 12 h d(-1) (0800-2000 h EST) mean concentrations of 366 and 697 microL L(-1), respectively. The two O3 treatments were charcoal-filtered air and nonfiltered air with O3 added for 12 h d(-1) to achieve seasonal 12 h d(-1) (0800-2000 h EST) mean concentrations of 23 and 72 nL L(-1), respectively. Elevated CO2 significantly stimulated growth and pod weight of Tenderette and S156, whereas elevated O3 significantly suppressed growth and pod weight of S156 but not of Tenderette. The suppressive effect of elevated O3 on pod dry weight of S156 was approximately 75% at ambient CO2 and approximately 60% at elevated CO2 (harvests combined). This amount of protection from O3 stress afforded by elevated CO2 was much less than reported for other crop species. Extreme sensitivity to O3 may be the reason elevated CO2 failed to significantly protect S156 from O3 stress.}, 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 (O 3 ) in the troposphere can cause plant stress, whereas elevated CO 2 generally enhances plant growth. Until recently, few studies have considered whether O 3 can affect plant response to CO 2 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 CO 2 and three O 3 treatments. The CO 2 treatments were ambient (approximately 380 μL L −1 ), or ambient with CO 2 added for 24 h d −1 to achieve mean concentrations of approximately 540, or 700 μL L −1 The O 3 treatments were charcoal‐filtered air (CF), nonfiltered air (NF), or NF with O 3 added for 12 h d −1 (NF+). Mean O 3 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 O 3 and `Coker 9904' was relatively sensitive; these cultivars were tested in Exp. 2. Foliar injury caused by O 3 was suppressed by elevated CO 2 in both experiments. In Exp. 1, plant size and yield increased with CO 2 enrichment in the NF and NF+ treatments, but not in the CF treatment. However, the O 3 × CO 2 interaction was rarely significant. In Exp. 2, growth and yield of C9904 was suppressed more by O 3 than was that of C9835. Because of cultivar differences in sensitivity to O 3 , CO 2 enrichment caused greater amelioration of O 3 stress and greater enhancement for C9904 than for C9835. Significant cultivar × O 3 × CO 2 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 O 3 and CO 2 when investigating effects of O 3 or CO 2 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={Little is known about effects of daily CO2 enrichment duration and root environment on plant response to elevated CO2. Two experiments were performed with Essex soybean (Glycine max L. Merr.) in open-top field chambers to address these questions. In one experiment, effects of 12 and 24 h d−1 exposures to double-ambient CO2 were compared for plants grown in 14 L pots that were either insulated to moderate soil temperature or not insulated. Although never significant statistically, trends at some growth stages suggested that nighttime CO2 enrichment contributed to growth and yield. Plants grew and yielded more in insulated than noninsulated pots, but there were no significant CO2 enrichment × insulation interactions. In the second experiment, response to approximately 1.3, 1.6, and 1.9 times ambient CO2 was compared for plants grown in the ground or 14 L pots. Enhancement of photosynthesis, growth, and yield by CO2 enrichment was similar in pots and in the ground. Linear responses to different CO2 concentrations were significant for all yield components in both root environments, whereas quadratic responses were significant for plants in pots but not for plants in the ground. Tests of proportionality of response for yield components showed no evidence of significant differences between plants in pots and in the ground except weight per 100 seeds. Seed yield enhancement at 1.9 times ambient CO2 was 36% for plants in pots and 33% for plants in the ground. Overall, proportional response of soybean to CO2 enrichment was relatively uniform in spite of large differences in baseline growth and yield.}, 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 (O3) in the troposphere can cause plant stress leading to foliar injury and suppressed growth and yield, whereas elevated CO2 generally enhances growth and yield. Numerous studies have been performed to determine effects of O3 and CO2 separately, but relatively few have been performed to determine if O3 can affect plant response to CO2 or vice versa. Open-top field chambers were used to determine if such interactions occur for cotton (Gossypium hirsurum L.), which is relatively sensitive to O3. 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 CO2 and two or three O3 treatments in all combinations during two seasons. The CO2 treatments were ambient (370 μL L−1) and two treatments with CO2 added for 24 h d−1 at approximately 1.5 and 2.0 times ambient. In 1995, the O3 treatments were charcoal filtered air (CF), and nonfiltered air (NF) with 0, added for 12 h d−1 (NF+). In 1996, a NF treatment was also included to represent ambient O3 conditions. The CF, NF, and NF+ treatments resulted in seasonal O3 concentrations of approximately 23, 51, and 75 nL L−1. Carbon dioxide enrichment generally stimulated growth and yield whereas O3 exposure suppressed growth and yield. Stimulation induced by CO2 increased as O3 stress increased. For example, in 1995 at medium N, the percentage increase in yield caused by doubling CO2 in CF air was O%, 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 CO2-induced prevention of O3 stress. The results emphasize the need to consider O3 × CO2 interactions to ensure correct interpretation of cause-effect relationships in CO2 enrichment studies with crops that are sensitive to O3.}, number={3}, journal={CROP SCIENCE}, author={Heagle, AS and Miller, JE and Booker, FL and Pursley, WA}, year={1999}, pages={731–741} }
 @article{heagle_miller_booker_1998, title={Influence of ozone stress on soybean response to carbon dioxide enrichment: I. Foliar properties}, volume={38}, ISSN={["0011-183X"]}, DOI={10.2135/cropsci1998.0011183X003800010020x}, abstractNote={Tropospheric O 3 can cause foliar injury, decreased growth, and decreased yield, whereas CO 2 enrichment generally causes opposite effects. Little is known about plant response to mixtures of O 3 and CO 2 . Open‐top field chambers were used to determine if foliar responses of soybean [ Glycine max (L.) Merr.] to CO 2 enrichment are affected by O 3 stress and vice versa. Plants were grown in 14‐L pots and exposed to four CO 2 and three O 3 concentrations in 12 combinations. The CO 2 treatments were ambient (366 μL − ) and three treatments with CO 2 added for 24 h d 1 at approximately 1.3, 1.6, and 2.0 times ambient. The O 3 treatments were charcoal‐filtered air (CF), nonfiltered air (NF), and NF with O 3 added for 12 h −1 ( NF+), resulting in seasonal concentrations of approximately 20, 46, and 75 nL L −1 . Foliar effects of CO 2 enrichment were dependent on the amount of stress caused by O 3 . In the CF treatment, plants were not stressed by O 3 , and CO 2 enrichment caused chlorosis and decreased chlorophyll. In the NF and NF+ treatments, plants were stressed by 03, and CO 2 enrichment suppressed chlorosis and increased chlorophyll. Ozone decreased specific leaf weight, increased foliar N and C, and decreased C/N ratios, whereas CO 2 caused opposite responses for these measures. Ozone increased foliar S and B but did not affect P or K concentrations. Conversely, CO 2 enrichment suppressed foliar S, B, P, and K concentrations. These interactions between O 3 and CO 2 emphasize a need to consider the amount of plant stress caused by O 3 in studies to measure effects of CO 2 enrichment.}, number={1}, journal={CROP SCIENCE}, author={Heagle, AS and Miller, JE and Booker, FL}, year={1998}, pages={113–121} }
 @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{heagle_miller_pursley_1998, title={Influence of ozone stress on soybean response to carbon dioxide enrichment: III. Yield and seed quality}, volume={38}, ISSN={["0011-183X"]}, DOI={10.2135/cropsci1998.0011183X003800010022x}, abstractNote={Ozone in the troposphere can cause plant stress, whereas elevated CO2 generally causes positive responses. Little is known of how these gases interact to affect plant response. Interactive effects on yield and seed quality of soybean [Glycine max (L.) Merr.] grown in 14-L pots were measured in open-top field chambers. Essex was tested in 1993, and Essex, Holladay, and NK 6955 were tested in 1994. Plants were exposed from emergence to maturity to four CO2 levels (ambient and 1.3,1.6, and 2.0 times ambient) and three O3 levels (0.4, 0.9, and 1.5 times ambient) in 12 combinations. Increasing O3 suppressed growth and yield, whereas CO2 enrichment stimulated growth and yield. Carbon dioxide-induced stimulation was greater for plants stressed by O3 than for non stressed plants. For example, CO2 at 2.0 times ambient increased 2-yr mean seed yield of Essex by 16, 24, and 81% at O2 levels of 0.4, 0.9, and 1.5 times ambient, respectively. Effects of O3 and CO2 on seed oil content were variable with numerous cultivar differences. Seed protein content was never affected. Elevated O3 suppressed oleic acid content in seeds, whereas CO2 increased it; the nature of the O3 × CO2 interaction for oleic acid was similar to that observed for most yield measures. Carbon dioxide-induced stimulation of plants stressed by O3 was apparently caused partly by amelioration of O3 stress. Interactions between O3 and CO2 must be considered for proper interpretation of cause-effect relationships in CO2, enrichment studies.}, number={1}, journal={CROP SCIENCE}, author={Heagle, AS and Miller, JE and Pursley, WA}, year={1998}, pages={128–134} }
 @article{booker_miller_1998, title={Phenylpropanoid metabolism and phenolic composition of soybean [Glycine max (L.) Merr.] leaves following exposure to ozone}, volume={49}, ISSN={["1460-2431"]}, DOI={10.1093/jexbot/49.324.1191}, abstractNote={Plants treated with the air pollutant, ozone (O3), often respond with increased transcript levels and activities of enzymes in the general phenylpropanoid and lignin pathways. This suggests that increased biosynthesis of lignin and related products also occurs. The purpose of this study was to determine whether O3 stimulated enzyme activities in these pathways in soybean [Glycine max (L.) Merr.] leaves, and if so, were hydroxycinnamic acids, lignin and suberin also produced. Plants were grown for 6 weeks in charcoal-filtered (CF) air and then treated with either CF air or CF air plus 100 nmol O3 mol−-1 7 h daily for up to 13 d in chambers in the greenhouse or in open-top chambers in the field. In greenhouse experiments, the activities of general phenylpropanoid pathway enzymes (phenylalanine ammonia-lyase and 4-coumarate:CoA ligase) were stimulated by O3 after 6 h. The activity of an enzyme in the lignin pathway (cinnamyl alcohol dehydrogenase) increased in O3-treated plants after 27 h. In greenhouse and field experiments, levels of cell-wall-bound total phenolics, acid-insoluble lignin and lignothioglycolic acid (LTGA) extracted from leaf tissue from O3-treated plants increased on average by 65%. However, histochemistry, UV and IR spectra, radiolabelling and a nitrobenzene oxidation assay all indicated that lignin and suberin did not increase with O3 treatment. Acidinsoluble lignin and LTGA extracted from O3-treated plants probably contained phenolic polymers that form in wounded or senescent tissues, thereby causing overestimates of the changes. Ozone-induced increases in phenolic metabolism, resembling certain elicited defence responses, thus occurred in concert with effects characteristic of the browning reaction and wound responses.}, number={324}, journal={JOURNAL OF EXPERIMENTAL BOTANY}, author={Booker, FL and Miller, JE}, year={1998}, month={Jul}, pages={1191–1202} }
 @article{fiscus_reid_miller_heagle_1997, title={Elevated CO2 reduces O-3 flux and O-3-induced yield losses in soybeans: Possible implications for elevated CO2 studies}, volume={48}, ISSN={["0022-0957"]}, DOI={10.1093/jxb/48.2.307}, abstractNote={Soybeans were grown for three seasons in open-top field chambers to determine (1) whether elevated CO2 (360 versus 700 μmol mol−1) alleviates some of the yield loss due to pollutant O3, (2) whether the partial stomatal closure resulting from chronic O3 exposure (charcoal-filtered air versus 1.5 × ambient concentrations) is a cause or result of decreased photosynthesis, and (3) possible implications of CO2/O3 interactions to climate change studies using elevated CO2. Leaf conductance was reduced by elevated CO2, regardless of O3 level, or by exposure to O3 alone. As.a result of these effects on conductance, high CO2 reduced estimated midday O3 flux into the leaf by an average of 50% in charcoal-filtered air and 35% in the high O3 treatment. However, while exposure to O3 reduced seed yields by 41% at ambient CO2 levels, the yield reduction was completely ameliorated by elevated CO2. The threshold midday O3 flux for yield loss appears to be 20–30 nmol m−2 s−1 in this study. Although elevated CO2 increased total biomass production, it did not increase seed yields. A/Ci curves show a large reduction in the stomatal limitation to photosynthesis due to elevated CO2 but no effect of O3. These data demonstrate that (1) reduced conductance due to O3 is the result, and not the cause, of reduced photosynthesis, (2) 700 μmol mol−1 CO2 can completely ameliorate yield losses due to O3 within the limits of these experiments, and (3) some reports of increased yields under elevated CO2 treatments may, at least in part, reflect the amelioration of unrecognized suppression of yield by O3 or other stresses.}, number={307}, journal={JOURNAL OF EXPERIMENTAL BOTANY}, author={Fiscus, EL and Reid, CD and Miller, JE and Heagle, AS}, year={1997}, month={Feb}, pages={307–313} }
 @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} }
 @article{booker_reid_brunschonharti_fiscus_miller_1997, title={Photosynthesis and photorespiration in soybean [Glycine max (L.) Merr.] chronically exposed to elevated carbon dioxide and ozone}, volume={48}, ISSN={["0022-0957"]}, DOI={10.1093/jexbot/48.315.1843}, number={315}, journal={JOURNAL OF EXPERIMENTAL BOTANY}, author={Booker, FL and Reid, CD and BrunschonHarti, S and Fiscus, EL and Miller, JE}, year={1997}, month={Oct}, pages={1843–1852} }
 @article{miller_pursley_heagle_1994, title={EFFECTS OF ETHYLENEDIUREA ON SNAP BEAN AT A RANGE OF OZONE CONCENTRATIONS}, volume={23}, ISSN={["0047-2425"]}, DOI={10.2134/jeq1994.00472425002300050033x}, abstractNote={Ethylenediurea (EDU) [N-[2-(2-Oxo-1-imidazolidinyl)ethyl]-N′-phenylurea] often protects plants from visible foliar injury due to the air pollutant O3, and it has been used to demonstrate yield losses from O3 under field conditions. A few studies, however, have indicated that EDU can suppress plant growth and yield. Because of the potential value of EDU as a research and assessment tool, controlled field experiments with snap bean (Phaseolus vulgaris L. ‘BBL-290’) were performed to test the effectiveness of different EDU application rates across a range of O3 concentrations. Four O3 concentrations were used in open-top chambers in each of two experiments [charcoal-filtered (CF) air, nonfiltered (NF) air, and nominal O3 additions of 0.025 and 0.05 or 0.03 and 0.06 μL L−1 O3 to NF air]. Ethylenediurea was added biweekly to the potting medium (four applications per experiment) as a soil drench. The EDU treatment concentrations were 0, 14, 28, 56, and 120 and 0, 8, 16, and 32 mg EDU (active) L−1 of potting medium in experiments one and two, respectively. Ethylenediurea provided some protection against O3-induced foliar injury and growth suppression in both experiments. Measurements of net carbon exchange rate (NCER) and carbohydrate status of the tissues reflected the protective effects of EDU. In the first experiment, however, EDU caused visible foliar injury at some growth stages and suppressed growth. In the second experiment, visible foliar injury was not caused by EDU at any concentration, but pod biomass (yield) was suppressed by EDU in CF chambers. The differences in response to EDU between the experiments may have been due to environmental conditions (i.e., hot and dry during the first experiment and cooler during the second). Ethylenediurea also affected biomass partitioning in the plants grown in CF air (relative biomass was increased in leaves and decreased in pods). The results indicate that although EDU does protect or partially protect snap bean against O3 injury, it may also affect physiology and growth.}, number={5}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={MILLER, JE and PURSLEY, WA and HEAGLE, AS}, year={1994}, pages={1082–1089} }
 @article{miller_booker_fiscus_heagle_pursley_vozzo_heck_1994, title={ULTRAVIOLET-B RADIATION AND OZONE EFFECTS ON GROWTH, YIELD, AND PHOTOSYNTHESIS OF SOYBEAN}, volume={23}, ISSN={["0047-2425"]}, DOI={10.2134/jeq1994.00472425002300010012x}, abstractNote={The projected increase in solar ultraviolet-B (UV-B) radiation due to depletion of stratospheric ozone (O3) has caused concern regarding possible UV-B damage to crops. At the same time, tropospheric O3 is projected to remain at concentrations that are known to damage crops. Since these two stressors may co-occur, experiments were performed to determine their separate and joint effects on crop growth, yield, and photosynthesis. Open-top chambers, equipped with filtered UV-B lamp systems, were used in 3 yr of field studies to treat soybean [Glycine max (L.) Merr.; ‘Coker 6955’, ‘Essex’, and ‘S 53-34’] with supplemental UV-B radiation and/or O3 from emergence through physiological maturity. Treatment levels of biologically effective UV-B radiation (UV-BBE) simulated the increase in ground level UV-B for stratospheric O3 depletion up to 37% (approximately a doubling of ambient UV-BBE). Ozone treatment concentrations ranged from 14 to 83 nL L−1 (seasonal mean 12 h d−1 concentrations). Ultraviolet-B radiation did not affect soybean seed yield in any of the 3 yr of the study. In 1 yr, UV-B affected pod and seed number and pod weight, but the treatment means were not consistently related to the UV-B dose. No O3 × UV-B interactions were found for any yield component at final harvest. Biweekly harvests of Essex during the growing season did not reveal any persistent effects of increased UV-B radiation on growth. Net carbon exchange rate (NCER), stomatal conductance, and transpiration of Essex soybean leaves were not suppressed by supplemental UV-B radiation. On the other hand, O3 treatment consistently induced visible injury, suppressed NCER and water use efficiency, accelerated reproductive development, and suppressed growth and yield. It is concluded that tropospheric O3 poses a greater threat to soybean production than projected levels of UV-B radiation.}, number={1}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={MILLER, JE and BOOKER, FL and FISCUS, EL and HEAGLE, AS and PURSLEY, WA and VOZZO, SF and HECK, WW}, year={1994}, pages={83–91} }
 @article{miller_heagle_vozzo_philbeck_heck_1989, title={EFFECTS OF OZONE AND WATER-STRESS, SEPARATELY AND IN COMBINATION, ON SOYBEAN YIELD}, volume={18}, ISSN={["0047-2425"]}, DOI={10.2134/jeq1989.00472425001800030016x}, abstractNote={Abstract A primary concern in applying existing 0 3 ‐effects data on crop production is the relatively unknown influence of soil moisture, which may modify plant response to 0 3 . One deficiency in field experiments that have tested the influence of soil moisture on crop response to 0 3 has been lack of control of soil moisture conditions in open‐top chamber plots. Most experiments have relied on the occurrence of normal drought periods during the growing season and use of irrigation to adjust soil moisture conditions. This has not allowed the control of the water stress cycles that is desirable. In 1986 a field experiment was performed with soybean [ Glycine max. (L.) Merr. cv. Young] to test the influence of periodic water stress on the yield response to O 3 . Open‐top field chambers were used to expose plants to a range of O 3 concentrations, and rain exclusion caps were used on individual chambers to help regulate soil moisture levels. Three soil moisture treatments were used [well‐watered (WW), waterstressed (WS), and well‐watered with permanent rain exclusion caps that were in place from 35 d after planting until physiological maturity (WW‐C)]. In the WW and WS treatments, the rain caps were put in place only during an exceptionally wet period from mid‐August to mid‐September. The WW and WW‐C treatments had approximately the same yield and response to O 3 , indicating that the presence of the caps for most of the growing season had little effect on growth or sensitivity to O 3 . The WS plots yielded approximately 10% less on the average than the WW and WW‐C plots, but water stress did not change the response to O 3 (i.e., no significant O 3 × water interaction). Based on a Weibull dose‐response model, O 3 reduced yield of ‘Young’ soybean 13% at a concentration of 0.05 µ L L −1 (12 h d −1 seasonal mean) compared to a hypothetical background of 0.02 µ L L −1 .}, number={3}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={MILLER, JE and HEAGLE, AS and VOZZO, SF and PHILBECK, RB and HECK, WW}, year={1989}, pages={330–336} }
 @article{miller_patterson_pursley_heagle_heck_1989, title={RESPONSE OF SOLUBLE SUGARS AND STARCH IN FIELD-GROWN COTTON TO OZONE, WATER-STRESS, AND THEIR COMBINATION}, volume={29}, ISSN={["0098-8472"]}, DOI={10.1016/0098-8472(89)90026-9}, abstractNote={Ozone (O3) stress is known to reduce the growth and yield of a number of crops, and water stress can modify the extent of these effects. Both O3 and water stress alter the carbohydrate status of plants. Little is known, however, concerning O3 effects on carbohydrate pools of field-grown plants and whether water stress will modify the carbohydrate response to O3. Cotton (Gossypium hirsutum L. “McNair-235”) plants were exposed to five O3 concentrations in open-top field chambers for 12 hr/day throughout the growing season at two levels of soil water (well-watered or periodically water-stressed). The O3 concentrations ranged from 0.021 to 0.073 μl/l (seasonal mean 12 hr/day concentration). Plants were sampled from each plot on four occasions encompassing the early- to late-reproductive stages of growth. Soluble sugars (glucose, fructose and sucrose) and starch were measured in leaves, stems and roots at each sampling date. Analysis of variance was performed for main effects and interactions of O3 and water treatments at each sampling date (O3 effects were partitioned in linear and quadratic components). Effects of O3 and water stress on soluble carbohydrates and starch were most common in stems and roots. Ozone suppressed carbohydrate concentrations in all cases where significant O3 effects were detected in the absence of O3 × water interactions. On the other hand, soluble carbohydrate concentrations were greater in water-stressed plant tissues when effects were significant and in the absence of interactions. Water-stress effects on starch were variable. Interactions of O3 and water stress were not consistent but often included interaction with the quadratic O3 component.}, number={4}, journal={ENVIRONMENTAL AND EXPERIMENTAL BOTANY}, author={MILLER, JE and PATTERSON, RP and PURSLEY, WA and HEAGLE, AS and HECK, WW}, year={1989}, month={Oct}, pages={477–486} }