@article{hung_kittur_wharton_umstead_burwell_thomas_qi_zhang_oldham_burkey_et al._2023, title={A Rapid Alkalinization Factor-like Peptide EaF82 Impairs Tapetum Degeneration during Pollen Development through Induced ATP Deficiency}, volume={12}, ISSN={["2073-4409"]}, DOI={10.3390/cells12111542}, abstractNote={In plants, the timely degeneration of tapetal cells is essential for providing nutrients and other substances to support pollen development. Rapid alkalinization factors (RALFs) are small, cysteine-rich peptides known to be involved in various aspects of plant development and growth, as well as defense against biotic and abiotic stresses. However, the functions of most of them remain unknown, while no RALF has been reported to involve tapetum degeneration. In this study, we demonstrated that a novel cysteine-rich peptide, EaF82, isolated from shy-flowering 'Golden Pothos' (Epipremnum aureum) plants, is a RALF-like peptide and displays alkalinizing activity. Its heterologous expression in Arabidopsis delayed tapetum degeneration and reduced pollen production and seed yields. RNAseq, RT-qPCR, and biochemical analyses showed that overexpression of EaF82 downregulated a group of genes involved in pH changes, cell wall modifications, tapetum degeneration, and pollen maturation, as well as seven endogenous Arabidopsis RALF genes, and decreased proteasome activity and ATP levels. Yeast two-hybrid screening identified AKIN10, a subunit of energy-sensing SnRK1 kinase, as its interacting partner. Our study reveals a possible regulatory role for RALF peptide in tapetum degeneration and suggests that EaF82 action may be mediated through AKIN10 leading to the alteration of transcriptome and energy metabolism, thereby causing ATP deficiency and impairing pollen development.}, number={11}, journal={CELLS}, author={Hung, Chiu-Yueh and Kittur, Farooqahmed S. and Wharton, Keely N. and Umstead, Makendra L. and Burwell, D'Shawna B. and Thomas, Martinique and Qi, Qi and Zhang, Jianhui and Oldham, Carla E. and Burkey, Kent O. and et al.}, year={2023}, month={Jun} }
 @article{zentella_burkey_tisdale_2023, title={Impact of tropospheric ozone on root proteomes of two soybean genotypes with contrasting sensitivity to ozone}, volume={208}, ISSN={["1873-7307"]}, DOI={10.1016/j.envexpbot.2023.105269}, abstractNote={Tropospheric ozone (O3), a critically harmful greenhouse gas, has steadily increased over the last several decades, leading to significant soybean (Glycine max) yield loses worldwide. However, substantial efforts have focused on the effect of elevated O3 concentration (eOZ) on shoots rather than the roots that support plant fitness and directly interact with soil ecosystems. To better assess the impact of eOZ on roots, this study investigated morphological and proteomic profiles of two soybean genotypes from the same genetic background, but with contrasting O3 resilience, Fiskeby III (O3-tolerant) and Fiskeby 840–7–3 (O3-sensitive). Plants were treated either with sub-ambient O3 or eOZ in a field-based air exclusion system (AES) and harvested at flowering and pod-filling stages. Our results established that the effect of eOZ on decreasing root biomass initiated at the flowering stage, while above-ground biomass was not altered. However, O3-caused biomass reduction was observed in both, roots and shoots, at the pod-filling stage. Season-long eOZ ultimately caused a 29 % seed yield reduction in Fiskeby III, and 50 % in Fiskeby 840–7–3. Root proteome analysis showed that the effect of O3 in roots is complex, and distinct between flowering and pod-filling stages. Changes in the abundance of proteins correspond to glycolysis, TCA cycle, nitrogen metabolism, secondary metabolites, antioxidant, and stress response pathway, and differed between genotypes. Some of these changes may be in response to eOZ as an attempt to mitigate the effects of a challenging environment, and others are likely due to genetic differences that confer an adaptative advantage to the O3 resilient genotype. These findings provide further knowledge of proteins and pathways that may confer O3-tolerance, which can be applied to develop O3-resistant, high-yielding soybean.}, journal={ENVIRONMENTAL AND EXPERIMENTAL BOTANY}, author={Zentella, Rodolfo and Burkey, Kent O. and Tisdale, Ripley H.}, year={2023}, month={Apr} }
 @article{zhang_zentella_burkey_liao_tisdale_2023, title={Microbial community dynamics responding to nutrient allocation associated with soybean cultivar ?Jake? ozone adaptation}, volume={864}, ISSN={["1879-1026"]}, DOI={10.1016/j.scitotenv.2022.161008}, abstractNote={Tropospheric ozone (O3), a major air pollutant, leads to significant global yield loss in soybean [Glycine max (L.) Merr.]. Soybean cultivar 'Jake' shows O3 resilient traits in above-ground organs, but the root system remains sensitive to elevated O3 (eO3). Changing carbon (C) and nitrogen (N) resource composition during eO3 stress suggests that eO3 presumably alters belowground soil microbial communities and their driven nutrient transformation. Yet, the responses of belowground microbes to eO3 and their feedback on nutrient cycling in 'Jake' are unknown. In this study, we holistically investigated soil microbial communities associated with C and N dynamics and bacterial-fungal inter-kingdom networks in the rhizosphere and bulk soil at different developmental stages of 'Jake' grown under sub-ambient O3 [charcoal-filtered (CF) air, 12 h mean: 20 ppb] or eO3 (12 h mean: 87 ppb). The results demonstrated eO3 significantly decreased fungal diversity and complexity of microbial networks at different 'Jake' developmental stages, whereas bacterial diversity was more tolerant to eO3 in both bulk soil and rhizosphere. In the bulk soil, no O3-responsive microbial biomarkers were found to be associated with C and N content, implying eO3 may stimulate niche-based processes during 'Jake' growth. In contrast, this study identified O3-responsive microbial biomarkers that may contribute to the N acquisition (Chloroflexales) and C dynamics (Caldilineales, Thermomicrobiales, and Hypocreales) in the rhizosphere, which may support the O3 resilience of the 'Jake' cultivar. However, further investigation is required to confirm their specific contributions by determining changes in microbial gene expression. Overall, these findings conduce to an expanding knowledge base that O3 induces temporal and spatial changes in the effects of microbial and nutrient networks in the O3-tolerant agriculture ecosystems.}, journal={SCIENCE OF THE TOTAL ENVIRONMENT}, author={Zhang, Kaile and Zentella, Rodolfo and Burkey, Kent O. and Liao, Hui-Ling and Tisdale, Ripley H.}, year={2023}, month={Mar} }
 @article{mashaheet_burkey_marshall_2023, title={The interaction of O3 and CO2 concentration, exposure timing and duration on stem rust severity on winter wheat variety 'Coker 9553'}, volume={334}, ISSN={["1873-6424"]}, DOI={10.1016/j.envpol.2023.122122}, abstractNote={Wheat rusts, elevated ozone (O3), and carbon dioxide (CO2) are simultaneously impacting wheat production worldwide, but their interactions are not well understood. This study investigated whether near-ambient O3 is suppressive or conducive to stem rust (Sr) of wheat, considering the interactions with ambient and elevated CO2. Winter wheat variety 'Coker 9553' (Sr-susceptible; O3 sensitive) was inoculated with Sr (race QFCSC) following pre-treatment with four different concentrations of O3 (CF, 50, 70, and 90 ppbv) at ambient CO2 levels. Gas treatments were continued during the development of disease symptoms. Disease severity, measured as percent sporulation area (PSA), significantly increased relative to the CF control only under near-ambient O3 conditions (50 ppbv) in the absence of O3-induced foliar injury. Disease symptoms at higher O3 exposures (70 and 90 ppbv) were similar to or less than the CF control. When Coker 9553 was inoculated with Sr while exposed to CO2 (400; 570 ppmv) and O3 (CF; 50 ppbv) in four different combinations, and seven combinations of exposure timing and duration, PSA significantly increased only under continuous treatment with O3 for six weeks or pre-inoculation treatment for three weeks, suggesting that O3-predisposes wheat to the disease rather than enhancing disease post-inoculation. O3 singly and in combination with CO2 increased PSA on flag leaves of adult Coker 9553 plants while elevated CO2 alone had little effect on PSA. These findings show that sub-symptomatic O3 conditions are conducive to stem rust, contradicting the current consensus that biotrophic pathogens are suppressed by elevated O3. This suggests that sub-symptomatic O3 stress may enhance rust diseases in wheat-growing regions.}, journal={ENVIRONMENTAL POLLUTION}, author={Mashaheet, Alsayed M. and Burkey, Kent O. and Marshall, David S.}, year={2023}, month={Oct} }
 @article{kittipornkul_thiravetyan_de carlo_burkey_paoletti_2021, title={Different Capability of Native and Non-native Plant Growth-Promoting Bacteria to Improve Snap Bean Tolerance to Ozone}, volume={232}, ISSN={["1573-2932"]}, DOI={10.1007/s11270-021-05230-z}, number={7}, journal={WATER AIR AND SOIL POLLUTION}, author={Kittipornkul, Piyatida and Thiravetyan, Paitip and De Carlo, Anna and Burkey, Kent and Paoletti, Elena}, year={2021}, month={Jul} }
 @article{tisdale_zentella_burkey_2021, title={Impact of elevated ozone on yield and carbon-nitrogen content in soybean cultivar 'Jake'}, volume={306}, ISSN={["1873-2259"]}, DOI={10.1016/j.plantsci.2021.110855}, abstractNote={Tropospheric ozone (O3) is a pollutant that leads to significant global yield loss in soybean [Glycine max (L.) Merr.]. To ensure soybean productivity in areas of rising O3, it is important to identify tolerant genotypes. This work describes the response of the high-yielding soybean cultivar ‘Jake’ to elevated O3 concentrations. ‘Jake’ was treated with either low O3 [charcoal-filtered (CF) air, 12 h mean: 20 ppb] or with O3-enriched air (12 h mean: 87 ppb) over the course of the entire growing season. In contrast to the absence of O3-induced leaf injury under low O3, elevated O3 caused severe leaf injury and decreased stomatal conductance and photosynthesis. Although elevated O3 reduced total leaf area, leaf number, and plant height at different developmental stages, above-ground and root biomass remained unchanged. Analyzing carbon and nitrogen content, we found that elevated O3 altered allocation of both elements, which ultimately led to a 15 % yield loss by decreasing seed size but not seed number. We concluded that cultivar ‘Jake’ possesses developmental strength to tolerate chronic O3 conditions, attributes that make it suitable breeding material for the generation of new O3 tolerant lines.}, journal={PLANT SCIENCE}, author={Tisdale, Ripley H. and Zentella, Rodolfo and Burkey, Kent O.}, year={2021}, month={May} }
 @article{hung_zhang_bhattacharya_li_kittur_oldham_wei_burkey_chen_xie_2021, title={Transformation of Long-Lived Albino Epipremnum aureum 'Golden Pothos' and Restoring Chloroplast Development}, volume={12}, ISSN={["1664-462X"]}, DOI={10.3389/fpls.2021.647507}, abstractNote={Chloroplasts are organelles responsible for chlorophyll biosynthesis, photosynthesis, and biosynthesis of many metabolites, which are one of key targets for crop improvement. Elucidating and engineering genes involved in chloroplast development are important approaches for studying chloroplast functions as well as developing new crops. In this study, we report a long-lived albino mutant derived from a popular ornamental plant Epipremnum aureum 'Golden Pothos' which could be used as a model for analyzing the function of genes involved in chloroplast development and generating colorful plants. Albino mutant plants were isolated from regenerated populations of variegated 'Golden Pothos' whose albino phenotype was previously found to be due to impaired expression of EaZIP, encoding Mg-protoporphyrin IX monomethyl ester cyclase. Using petioles of the mutant plants as explants with a traceable sGFP gene, an efficient transformation system was developed. Expressing Arabidopsis CHL27 (a homolog of EaZIP) but not EaZIP in albino plants restored green color and chloroplast development. Interestingly, in addition to the occurrence of plants with solid green color, plants with variegated leaves and pale-yellow leaves were also obtained in the regenerated populations. Nevertheless, our study shows that these long-lived albino plants along with the established efficient transformation system could be used for creating colorful ornamental plants. This system could also potentially be used for investigating physiological processes associated with chlorophyll levels and chloroplast development as well as certain biological activities, which are difficult to achieve using green plants.}, journal={FRONTIERS IN PLANT SCIENCE}, author={Hung, Chiu-Yueh and Zhang, Jianhui and Bhattacharya, Chayanika and Li, Hua and Kittur, Farooqahmed S. and Oldham, Carla E. and Wei, Xiangying and Burkey, Kent O. and Chen, Jianjun and Xie, Jiahua}, year={2021}, month={May} }
 @article{tisdale_zobel_burkey_2021, title={Tropospheric ozone rapidly decreases root growth by altering carbon metabolism and detoxification capability in growing soybean roots}, volume={766}, ISSN={["1879-1026"]}, DOI={10.1016/j.scitotenv.2020.144292}, abstractNote={High tropospheric ozone (O 3 ) concentrations lead to significant global soybean ( Glycine max ) yield reductions. Research concerning O 3 impacts on soybean has focused on the contributions of above-ground tissues. In this study, Mandarin (Ottawa) (O 3 -sensitive) and Fiskeby III (O 3 -tolerant) soybean genotypes provide contrasting materials to investigate O 3 effects on root growth. We compared root morphological and proteomic changes when 16-day-old plants were treated with charcoal-filtered (CF) air or elevated O 3 (80 ppb O 3 for 7 h/day) in continuously stirred-tank reactors (CSTR) for 7 days. Our results showed that in Mandarin (Ottawa), decreased expression of enzymes involved in the tricarboxylic acid (TCA) cycle contributes to reduction of root biomass and diameter under elevated O 3 . In contrast, O 3 tolerance in Fiskeby III roots was associated with O 3 -dependent induction of enzymes involved in glycolysis and O 3 -independent expression of enzymes involved in the ascorbate-glutathione cycle. We conclude that a decreased abundance of key redox enzymes in roots due to limited carbon availability rapidly alters root growth under O 3 stress. However, maintaining a high abundance of enzymes associated with redox status and detoxification capability contributes to overall O 3 tolerance in roots. • O 3 rapidly reduces root development prior to effects on above-ground growth. • Enzymes involved in the TCA and glutathione redox cycle are decreased by O 3 . • O 3 tolerance in roots is related to high detoxification capability. • O 3 increases energy molecules by inducing glycolytic enzymes in O 3 -tolerent roots.}, journal={SCIENCE OF THE TOTAL ENVIRONMENT}, author={Tisdale, Ripley H. and Zobel, Richard W. and Burkey, Kent O.}, year={2021}, month={Apr} }
 @article{qiu_guo_xu_zhang_zhang_chen_zhao_burkey_shew_zobel_et al._2021, title={Warming and elevated ozone induce tradeoffs between fine roots and mycorrhizal fungi and stimulate organic carbon decomposition}, volume={7}, ISSN={["2375-2548"]}, DOI={10.1126/sciadv.abe9256}, abstractNote={Warming and elevated ozone alter root traits and mycorrhizal fungal community and stimulate organic carbon decomposition.}, number={28}, journal={SCIENCE ADVANCES}, author={Qiu, Yunpeng and Guo, Lijin and Xu, Xinyu and Zhang, Lin and Zhang, Kangcheng and Chen, Mengfei and Zhao, Yexin and Burkey, Kent O. and Shew, H. David and Zobel, Richard W. and et al.}, year={2021}, month={Jul} }
 @article{mashaheet_burkey_saitanis_abdelrhim_rafiullah_marshall_2020, title={Differential Ozone Responses Identified among Key Rust-Susceptible Wheat Genotypes}, volume={10}, ISSN={["2073-4395"]}, DOI={10.3390/agronomy10121853}, abstractNote={Increasing ambient ozone (O3) concentrations and resurgent rust diseases are two concomitant limiting factors to wheat production worldwide. Breeding resilient wheat cultivars bearing rust resistance and O3 tolerance while maintaining high yield is critical for global food security. This study aims at identifying ozone tolerance among key rust-susceptible wheat genotypes [Rust near-universal susceptible genotypes (RnUS)], as a first step towards achieving this goal. Tested RnUS included seven bread wheat genotypes (Chinese Spring, Line E, Little Club, LMPG 6, McNair 701, Morocco and Thatcher), and one durum wheat line (Rusty). Plants were treated with five O3 concentrations (CF, 50, 70, 90, and 110 ppb), in two O3 exposure systems [continuous stirred tank reactors (CSTR) and outdoor-plant environment chambers (OPEC)], at 21–23 Zadoks decimal growth stage. Visible injury and biomass accumulation rate were used to assess O3 responses. Visible injury data showed consistent order of genotype sensitivity (Thatcher, LMPG 6 > McNair 701, Rusty > Line E, Morocco, Little Club > Chinese Spring). Additionally, leaves at different orders showed differential O3 responses. Biomass accumulation under O3 stress showed similar results for the bread wheat genotypes. However, the durum wheat line “Rusty” had the most O3-sensitive biomass production, providing a contrasting O3 response to the tolerance reported in durum wheat. Chinese Spring was the most tolerant genotype based on both parameters and could be used as a source for O3 tolerance, while sensitive genotypes could be used as sensitive parents in mapping O3 tolerance in bread wheat. The suitability of visible symptoms and biomass responses in high-throughput screening of wheat for O3 tolerance was discussed. The results presented in this research could assist in developing future approaches to accelerate breeding wheat for O3 tolerance using existing breeding materials.}, number={12}, journal={AGRONOMY-BASEL}, author={Mashaheet, Alsayed M. and Burkey, Kent O. and Saitanis, Costas J. and Abdelrhim, Abdelrazek S. and Rafiullah and Marshall, David S.}, year={2020}, month={Dec} }
 @article{burkey_tisdale_zobel_ray_pursley_2020, title={Interactive Effects of Elevated Ozone and Temperature on Growth and Yield of Soybean (Glycine max (L.) Merr.) under Field Conditions}, volume={10}, ISSN={["2073-4395"]}, DOI={10.3390/agronomy10111803}, abstractNote={Elevated ozone and rising temperature are both factors in climate change, but they are difficult to study in combination due to exposure system requirements. We developed and deployed an air exclusion exposure system to treat soybean (Glycine max (L.) Merr.) cultivar “Jake” with season-long combinations of sub-ambient ozone (18 ppb, 12 h mean), elevated ozone (66 ppb, 12 h mean), and elevated temperature (+3.5 °C daytime, +2.4 °C nighttime) in irrigated field plots. Warming caused a shift in biomass partitioning from reproductive tissues into stems and petioles at mid-season that resulted in a significant 25% reduction in final seed yield and a significant reduction in harvest index. The elevated ozone treatment delayed mid-season biomass production, and final seed yield was reduced by a non-significant 2%. However, there were significant underlying effects of elevated ozone on seed production. The non-significant impact of ozone on seed yield of cultivar “Jake” resulted from significant increases in pod number (+16%) and seed number (+18%) that were offset by a significant reduction in seed size (−16%). No evidence of significant warming–ozone interactions was found in biomass or seed yield responses. In general, significant impacts of the individual warming or ozone treatments were found to be additive.}, number={11}, journal={AGRONOMY-BASEL}, author={Burkey, Kent and Tisdale, Ripley and Zobel, Richard and Ray, Samuel and Pursley, Walter}, year={2020}, month={Nov} }
 @article{mashaheet_burkey_marshall_2019, title={Chromosome Location Contributing to Ozone Tolerance in Wheat}, volume={8}, ISSN={["2223-7747"]}, DOI={10.3390/plants8080261}, abstractNote={Breeding wheat for higher grain yield can contribute to global food security and sustainable production on less land. Tropospheric ozone can injure wheat plants and subsequently reduce grain yield. Identification of ozone tolerance in the wheat genome can assist plant breeders in developing new sources of tolerant germplasm. Our objective was to use the ‘Chinese Spring’ monosomic lines to screen for ozone response and identify the chromosomic locations contributing to ozone tolerance based on foliar injury. Two methodologies, Continuous Stirred Tank Reactors and Outdoor Plant Environment Chambers, were used to expose wheat monosomic lines to varying concentrations and durations of ozone. Each wheat monosomic line in ‘Chinese Spring’ has a missing chromosome in each of the wheat subgenomes (A, B, and D). In both methodologies, we found significant and repeatable data to identify chromosome 7A as a major contributor to tolerance to ozone injury in ‘Chinese Spring’. In every experiment, the absence of chromosome 7A resulted in significant injury to wheat due to ozone. This was not the case when any other chromosome was missing.}, number={8}, journal={PLANTS-BASEL}, author={Mashaheet, Alsayed M. and Burkey, Kent O. and Marshall, David S.}, year={2019}, month={Aug} }
 @article{guarin_kassie_mashaheet_burkey_asseng_2019, title={Modeling the effects of tropospheric ozone on wheat growth and yield}, volume={105}, ISSN={["1873-7331"]}, DOI={10.1016/j.eja.2019.02.004}, abstractNote={Abstract Elevated tropospheric ozone (O3) concentrations can negatively impact wheat growth by reducing photosynthesis and accelerating leaf senescence. Future global O3 concentrations are expected to increase in many regions, which will further limit global wheat production. However, few crop models consider the effects of O3 stress on wheat. We incorporated the effects of O3 stress on photosynthesis and leaf senescence into the DSSAT-NWheat crop model and reproduced an observed experiment and reported yield declines from the literature. Simulated wheat yields decreased as daily O3 concentrations increased above 25 ppb, with yield losses ranging from 0.26% to 0.95% per ppb O3 increase, depending on the cultivar O3 sensitivity. The model reproduced known wheat physiological responses from the combination of O3 stress with water deficit and elevated atmospheric CO2 concentration. Increased water deficit stress and elevated atmospheric CO2 both reduce the negative impact of O3, but yield benefits from elevated CO2 can be lost due to elevated O3 concentrations. The O3-modified NWheat model simulates the effects of O3 stress on wheat growth and yield in interaction with other growth factors and can be used for studies on climate change and O3 impacts.}, journal={EUROPEAN JOURNAL OF AGRONOMY}, author={Guarin, Jose Rafael and Kassie, Belay and Mashaheet, Alsayed M. and Burkey, Kent and Asseng, Senthold}, year={2019}, month={Apr}, pages={13–23} }
 @article{abdallah_mashaheet_zobel_burkey_2019, title={Physiological basis for controlling water consumption by two snap beans genotypes using different anti-transpirants}, volume={214}, ISSN={["1873-2283"]}, DOI={10.1016/j.agwat.2018.12.029}, abstractNote={Enhancing water use efficiency (WUE), while maintaining productivity, represents a challenge, particularly, in arid and semi-arid environments. The use Antitranspirants (ATs) is an effective approach to mitigate water deficit- and drought-induced yield losses, via reducing transpiration. This study aimed to determine the effects of ATs compounds on WUE and root and shoot physiological responses of two snap bean genotypes with different ozone sensitivity [tolerant (R123) and sensitive (S156)]. Under glasshouse conditions, plants were sprayed (25 days after planting) with 4% (w/v) kaolin (KPF); 0.0015% (w/v) Fulvic acid (FA); 1% (v/v) Pinolene (PIN) or water (control). Treatments were subjected to three irrigation/drying cycles, and then exposed to survivability test by ceasing irrigation. Water consumption (WC), leaf water potential (Ψw), total dry matter (TDM), dry matter accumulation rate (DMAR), leaf temperature, plant survival and root development were determined. There was a minimal genotype effect on all parameters, except TDM, DMAR, and fine-root diameter and length. KPF treatment was cooler than the control (<3.83 °C), consequently, had higher Ψw and lower WC, without affecting TDM and DMAR. Therefore, biomass-WUE (total dry matter/transpired water) of KPF treatment increased (29.4% and 13.3% for R123 and S156, respectively). Pinolene and FA treatments exerted no effects on those parameters. KPF treatment alleviated most of the physiological effects of water deficit, hence plants survived longer. KPF and FA treatments had thicker very fine (0.0726 to 0.29 mm) and fine (0.308 to 0.562 mm) roots than the control, with KPF having the strongest effect on roots development. Pinolene treatment showed no effect on the roots of R123, but conditioned significant thickening of S156 roots; a notable reversal of the observed effect of KPF and FA. In conclusion, conserved water by KPF, could reduce irrigation frequency and, later, play as a crucial water resource for plant survival. Moreover, future research with ATs must take root responses into account.}, journal={AGRICULTURAL WATER MANAGEMENT}, author={AbdAllah, Ahmed M. and Mashaheet, Alsayed M. and Zobel, Richard and Burkey, Kent O.}, year={2019}, month={Apr}, pages={17–27} }
 @article{qiu_jiang_guo_zhang_burkey_zobel_reberg-horton_shew_hui_2019, title={Shifts in the Composition and Activities of Denitrifiers Dominate CO2 Stimulation of N2O Emissions}, volume={53}, ISSN={["1520-5851"]}, DOI={10.1021/acs.est.9b02983}, abstractNote={Elevated atmospheric CO2 (eCO2) often increases soil N2O emissions, but the underlying mechanisms remain largely unknown. One hypothesis suggests that high N2O emissions may stem from increased denitrification induced by CO2 enhancement of plant carbon (C) allocation belowground. However, direct evidence illustrating linkages among N2O emissions, plant C allocation, and denitrifying microbes under eCO2 is still lacking. We examined the impact of eCO2 on plant C allocation to roots and their associated arbuscular mycorrhizal fungi and its subsequent effects on N2O emissions and denitrifying microbes in the presence of two distinct N sources, ammonium nitrogen (NH4+–N) and nitrate nitrogen (NO3––N). Our results showed that the form of the N inputs dominated the effects of eCO2 on N2O emissions: eCO2 significantly increased N2O emissions with NO3––N inputs but had no effect with NH4+–N inputs. eCO2 increased plant biomass N more with NH4+–N than with NO3––N inputs, likely reducing microbial access to available N under NH4+–N inputs and/or contributing to higher N2O emissions under NO3––N inputs. eCO2 enhanced root and mycorrhizal N uptake and also increased N2O emissions under NO3––N inputs. Further, eCO2 enhancement of N2O emissions under NO3––N inputs concurred with a shift in the soil denitrifier community composition in favor of N2O-producing (nirK- and nirS-type) over N2O-consuming (nosZ-type) denitrifiers. Together, these results indicate that eCO2 stimulated N2O emissions mainly through altering plant N preference in favor of NH4+ over NO3– and thus stimulating soil denitrifiers and their activities. These findings suggest that effective management of N sources may mitigate N2O emissions by negating the eCO2 stimulation of soil denitrifying microbes and their activities.}, number={19}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Qiu, Yunpeng and Jiang, Yu and Guo, Lijin and Zhang, Lin and Burkey, Kent O. and Zobel, Richard W. and Reberg-Horton, S. Chris and Shew, H. David and Hui, Shuijin}, year={2019}, month={Oct}, pages={11204–11213} }
 @article{zhang_qiu_cheng_wang_liu_tu_bowman_burkey_bian_zhang_et al._2018, title={Atmospheric CO2 Enrichment and Reactive Nitrogen Inputs Interactively Stimulate Soil Cation Losses and Acidification}, volume={52}, ISSN={["1520-5851"]}, DOI={10.1021/acs.est.8b00495}, abstractNote={Reactive N inputs (Nr) may alleviate N-limitation of plant growth and are assumed to help sustain plant responses to the rising atmospheric CO2 (eCO2). However, Nr and eCO2 may elicit a cascade reaction that alters soil chemistry and nutrient availability, shifting the limiting factors of plant growth, particularly in acidic tropical and subtropical croplands with low organic matter and low nutrient cations. Yet, few have so far examined the interactive effects of Nr and eCO2 on the dynamics of soil cation nutrients and soil acidity. We investigated the cation dynamics in the plant–soil system with exposure to eCO2 and different N sources in a subtropical, acidic agricultural soil. eCO2 and Nr, alone and interactively, increased Ca2+ and Mg2+ in soil solutions or leachates in aerobic agroecosystems. eCO2 significantly reduced soil pH, and NH4+-N inputs amplified this effect, suggesting that eCO2-induced plant preference of NH4+-N and plant growth may facilitate soil acidification. This is, to our knowledge, the first direct demonstration of eCO2 enhancement of soil acidity, although other studies have previously shown that eCO2 can increase cation release into soil solutions. Together, these findings provide new insights into the dynamics of cation nutrients and soil acidity under future climatic scenarios, highlighting the urgency for more studies on plant–soil responses to climate change in acidic tropical and subtropical ecosystems.}, number={12}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Zhang, Li and Qiu, Yunpeng and Cheng, Lei and Wang, Yi and Liu, Lingli and Tu, Cong and Bowman, Dan C. and Burkey, Kent O. and Bian, Xinmin and Zhang, Weijian and et al.}, year={2018}, month={Jun}, pages={6895–6902} }
 @article{qu_jiang_guo_burkey_zobel_shew_hu_2018, title={Contrasting Warming and Ozone Effects on Denitrifiers Dominate Soil N2O Emissions}, volume={52}, ISSN={["1520-5851"]}, DOI={10.1021/acs.est.8b01093}, abstractNote={Nitrous oxide (N2O) in the atmosphere is a major greenhouse gas and reacts with volatile organic compounds to create ozone (an air pollutant) in the troposphere. Climate change factors such as warming and elevated ozone (eO3) affect N2O fluxes, but the direction and magnitude of these effects are uncertain and the underlying mechanisms remain unclear. We examined the impact of simulated warming (control + 3.6 °C) and eO3 (control + 45 ppb) on soil N2O fluxes in a soybean agroecosystem. Results obtained showed that warming significantly increased soil labile C, microbial biomass, and soil N mineralization, but eO3 reduced these parameters. Warming enhanced N2O-producing denitrifers (nirS- and nirK-type), corresponding to increases in both the rate and sum of N2O emissions. In contrast, eO3 significantly reduced both N2O-producing and N2O-consuming (nosZ-type) denitrifiers but had no impact on N2O emissions. Further, eO3 offsets the effects of warming on soil labile C, microbial biomass, and the population size of denitrifiers but still increased N2O emissions, indicating a direct effect of temperature on N2O emissions. Together, these findings suggest that warming may promote N2O production through increasing both the abundance and activities of N2O-producing microbes, positively feeding back to the ongoing climate change.}, number={19}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Qu, Yunpeng and Jiang, Yu and Guo, Lijin and Burkey, Kent O. and Zobel, Richard W. and Shew, H. David and Hu, Shuijin}, year={2018}, month={Oct}, pages={10956–10966} }
 @article{sun_hung_qiu_chen_kittur_oldham_henny_burkey_fan_xie_2017, title={Accumulation of high OPDA level correlates with reduced ROS and elevated GSH benefiting white cell survival in variegated leaves}, volume={7}, ISSN={["2045-2322"]}, DOI={10.1038/srep44158}, abstractNote={Abstract Variegated ‘Marble Queen’ ( Epipremnum aureum ) plant has white (VMW) and green (VMG) sectors within the same leaf. The white sector cells containing undifferentiated chloroplasts are viable, but the underlying mechanism for their survival and whether these white cells would use any metabolites as signal molecules to communicate with the nucleus for maintaining their viability remain unclear. We analyzed and compared phytohormone levels with their precursors produced in chloroplasts between VMW and VMG, and further compared their transcriptomes to understand the consequences related to the observed elevated 12-oxo phytodienoic acid (OPDA), which was 9-fold higher in VMW than VMG. Transcriptomic study showed that a large group of OPDA-responsive genes (ORGs) were differentially expressed in VMW, including stress-related transcription factors and genes for reactive oxygen species (ROS) scavengers, DNA replication and repair, and protein chaperones. Induced expression of these ORGs could be verified in OPDA-treated green plants. Reduced level of ROS and higher levels of glutathione in VMW were further confirmed. Our results suggest that elevated OPDA or its related compounds are recruited by white cells as a signaling molecule(s) to up-regulate stress and scavenging activity related genes that leads to reduced ROS levels and provides survival advantages to the white cells.}, journal={SCIENTIFIC REPORTS}, author={Sun, Ying-Hsuan and Hung, Chiu-Yueh and Qiu, Jie and Chen, Jianjun and Kittur, Farooqahmed S. and Oldham, Carla E. and Henny, Richard J. and Burkey, Kent O. and Fan, Longjiang and Xie, Jiahua}, year={2017}, month={Mar} }
 @article{wu_chen_tu_qiu_burkey_reberg-horton_peng_hu_2017, title={CO2-induced alterations in plant nitrate utilization and root exudation stimulate N2O emissions}, volume={106}, ISSN={["0038-0717"]}, DOI={10.1016/j.soilbio.2016.11.018}, abstractNote={Atmospheric carbon dioxide enrichment (eCO2) often increases soil nitrous oxide (N2O) emissions, which has been largely attributed to increased denitrification induced by CO2-enhancement of soil labile C and moisture. However, the origin of the N remains unexplained. Emerging evidence suggests that eCO2 alters plant N preference in favor of ammonium (NH4+-N) over nitrate (NO3−-N). Yet, whether and how this attributes to the enhancement of N2O emissions has not been investigated. We conducted a microcosm experiment with wheat (Triticum aestivum L.) and tall fescue (Schedonorus arundinaceus (Schreb.) Dumort.) to examine the effects of eCO2 on soil N2O emissions in the presence of two N forms (NH4+-N or NO3−-N). Results obtained showed that N forms dominated eCO2 effects on plant and microbial N utilization, and thus soil N2O emissions. Elevated CO2 significantly increased the rate and the sum of N2O emissions by three to four folds when NO3−-N, but not NH4+-N, was supplied under both wheat and tall fescue. While enhanced N2O emission was more related to the reduced plant NO3−-N uptake under wheat, it concurred with increased labile C under tall fescue. In the presence of NO3−-N, significantly lower shoot biomass N and 15N, but higher plant biomass C:N ratio, microbial biomass C and N, and/or soil extractable C indicated that eCO2 constrained plant NO3−-N utilization and likely stimulated root exudation. We propose a new conceptual model in which eCO2-inhibition of plant NO3−-N uptake and/or CO2-enhancement of soil labile C enhances the N and/or C availability for denitrifiers and increases the intensity and/or the duration of N2O emissions. Together, these findings indicate that CO2-enhancement of soil N and labile C favors denitrification, suggesting that management of N fertilizers in intensive systems will likely become more challenging under future CO2 scenarios.}, journal={SOIL BIOLOGY & BIOCHEMISTRY}, author={Wu, Keke and Chen, Dima and Tu, Cong and Qiu, Yunpeng and Burkey, Kent O. and Reberg-Horton, S. Chris and Peng, Shaolin and Hu, Shuijin}, year={2017}, month={Mar}, pages={9–17} }
 @article{waldeck_burkey_carter_dickey_song_taliercio_2017, title={RNA-Seq study reveals genetic responses of diverse wild soybean accessions to increased ozone levels}, volume={18}, ISSN={["1471-2164"]}, DOI={10.1186/s12864-017-3876-2}, abstractNote={Ozone is an air pollutant widely known to cause a decrease in productivity in many plant species, including soybean (Glycine max (L.) Merr). While the response of cultivated soybean to ozone has been studied, very little information is available regarding the ozone response of its wild relatives. Ozone-resistant wild soybean accessions were identified by measuring the response of a genetically diverse group of 66 wild soybean (Glycine soja Zucc. and Sieb.) accessions to elevated ozone levels. RNA-Seq analyses were performed on leaves of different ages from selected ozone-sensitive and ozone-resistant accessions that were subjected to treatment with an environmentally relevant level of ozone. Many more genes responded to elevated ozone in the two ozone-sensitive accessions than in the ozone-resistant accessions. Analyses of the ozone response genes indicated that leaves of different ages responded differently to ozone. Older leaves displayed a consistent reduction in expression of genes involved in photosynthesis in response to ozone, while changes in expression of defense genes dominated younger leaf tissue in response to ozone. As expected, there is a substantial difference between the response of ozone-sensitive and ozone-resistant accessions. Genes associated with photosystem 2 were substantially reduced in expression in response to ozone in the ozone-resistant accessions. A decrease in peptidase inhibitors was one of several responses specific to one of the ozone resistant accessions. The decrease in expression in genes associated with photosynthesis confirms that the photosynthetic apparatus may be an early casualty in response to moderate levels of ozone. A compromise of photosynthesis would substantially impact plant growth and seed production. However, the resistant accessions may preserve their photosynthetic apparatus in response to the ozone levels used in this study. Older leaf tissue of the ozone-resistant accessions showed a unique down-regulation of genes associated with endopeptidase inhibitor activity. This study demonstrates the existence of significant diversity in wild soybean for ozone response. Wild soybean accessions characterized in this study can be used by soybean breeders to enhance ozone tolerance of this important food crop.}, journal={BMC GENOMICS}, author={Waldeck, Nathan and Burkey, Kent and Carter, Thomas and Dickey, David and Song, Qijian and Taliercio, Earl}, year={2017}, month={Jun} }
 @article{estrada_bohlke_sturchio_gu_harvey_burkey_grantz_mcgrath_anderson_rao_et al._2017, title={Stable isotopic composition of perchlorate and nitrate accumulated in plants: Hydroponic experiments and field data}, volume={595}, ISSN={["1879-1026"]}, DOI={10.1016/j.scitotenv.2017.03.223}, abstractNote={Natural perchlorate (ClO4−) in soil and groundwater exhibits a wide range in stable isotopic compositions (δ37Cl, δ18O, and Δ17O), indicating that ClO4− may be formed through more than one pathway and/or undergoes post-depositional isotopic alteration. Plants are known to accumulate ClO4−, but little is known about their ability to alter its isotopic composition. We examined the potential for plants to alter the isotopic composition of ClO4− in hydroponic and field experiments conducted with snap beans (Phaseolus vulgaris L.). In hydroponic studies, anion ratios indicated that ClO4− was transported from solutions into plants similarly to NO3− but preferentially to Cl− (4-fold). The ClO4− isotopic compositions of initial ClO4− reagents, final growth solutions, and aqueous extracts from plant tissues were essentially indistinguishable, indicating no significant isotope effects during ClO4− uptake or accumulation. The ClO4− isotopic composition of field-grown snap beans was also consistent with that of ClO4− in varying proportions from irrigation water and precipitation. NO3− uptake had little or no effect on NO3− isotopic compositions in hydroponic solutions. However, a large fractionation effect with an apparent ε (15N/18O) ratio of 1.05 was observed between NO3− in hydroponic solutions and leaf extracts, consistent with partial NO3− reduction during assimilation within plant tissue. We also explored the feasibility of evaluating sources of ClO4− in commercial produce, as illustrated by spinach, for which the ClO4− isotopic composition was similar to that of indigenous natural ClO4−. Our results indicate that some types of plants can accumulate and (presumably) release ClO4− to soil and groundwater without altering its isotopic characteristics. Concentrations and isotopic compositions of ClO4− and NO3− in plants may be useful for determining sources of fertilizers and sources of ClO4− in their growth environments and consequently in food supplies.}, journal={SCIENCE OF THE TOTAL ENVIRONMENT}, author={Estrada, Nubia Luz and Bohlke, J. K. and Sturchio, Neil C. and Gu, Baohua and Harvey, Greg and Burkey, Kent O. and Grantz, David A. and McGrath, Margaret T. and Anderson, Todd A. and Rao, Balaji and et al.}, year={2017}, month={Oct}, pages={556–566} }
 @article{chutteang_booker_na-ngern_burton_aoki_burkey_2016, title={Biochemical and physiological processes associated with the differential ozone response in ozone-tolerant and sensitive soybean genotypes}, volume={18}, ISSN={["1438-8677"]}, DOI={10.1111/plb.12347}, abstractNote={Biochemical and physiological traits of two soybean [Glycine max (L.) Merr.] genotypes differing in sensitivity to ozone (O3 ) were investigated to determine the possible basis for the differential response. Fiskeby III (O3 -tolerant) and Mandarin (Ottawa) (O3 -sensitive) were grown in a greenhouse with charcoal-filtered air for 4 weeks, then treated with O3 for 7 h·day(-1) in greenhouse chambers. Mandarin (Ottawa) showed significantly more leaf injury and hydrogen peroxide (H2 O2 ) and superoxide (O2 (-) ) production compared with Fiskeby III. Peroxidase activity in Mandarin (Ottawa) was 31% higher with O3 but was not significantly different in Fiskeby III. Ozone did not affect superoxide dismutase or glutathione reductase activities, or leaf concentrations of glutathione or ascorbic acid. Thus, variation in O3 response between Fiskeby III and Mandarin (Ottawa) was not explained by differences in antioxidant enzymes and metabolites tested. Ethylene emission from leaves declined in Fiskeby III following O3 exposure but not in Mandarin (Ottawa). Ozone exposure reduced quantum yield (ΦPSII ), electron transport rate (ETR) and photochemical quenching (qp ) in Mandarin (Ottawa) more than in Fiskeby III, indicating that efficiency of energy conversion of PSII and photosynthetic electron transport was altered differently in the two genotypes. Short-term exposure to O3 had minimal effects on net carbon exchange rates of both soybean cultivars. A trend toward higher stomatal conductance in Mandarin (Ottawa) suggested stomatal exclusion might contribute to differential O3 sensitivity of the two genotypes. Increased sensitivity of Mandarin (Ottawa) to O3 was associated with higher H2 O2 and O2 (-) production compared with Fiskeby III, possibly associated with genotype differences in stomatal function or regulation of ethylene during the initial phases of O3 response.}, journal={PLANT BIOLOGY}, author={Chutteang, C. and Booker, F. L. and Na-Ngern, P. and Burton, A. and Aoki, M. and Burkey, K. O.}, year={2016}, month={Jan}, pages={28–36} }
 @article{burton_burkey_carter_orf_cregan_2016, title={Phenotypic variation and identification of quantitative trait loci for ozone tolerance in a Fiskeby III x Mandarin (Ottawa) soybean population}, volume={129}, ISSN={["1432-2242"]}, DOI={10.1007/s00122-016-2687-1}, number={6}, journal={THEORETICAL AND APPLIED GENETICS}, author={Burton, Amy L. and Burkey, Kent O. and Carter, Thomas E., Jr. and Orf, James and Cregan, Perry B.}, year={2016}, month={Jun}, pages={1113–1125} }
 @article{de kok_grantz_burkey_2016, title={Plants and the changing environment}, volume={18}, ISSN={["1438-8677"]}, DOI={10.1111/plb.12413}, abstractNote={Plant BiologyVolume 18, Issue S1 p. 3-4 Editorial Plants and the changing environment L. J. De Kok, L. J. De Kok [email protected] Laboratory of Plant Physiology, Groningen Institute for Evolutionary Life Sciences, University of Groningen, P.O. Box 11103, 9700 CC Groningen, The NetherlandsSearch for more papers by this authorD. A. Grantz, D. A. Grantz [email protected] Department of Botany and Plant Sciences, University of California, Riverside, Parlier, 93648 CA, USASearch for more papers by this authorK. O. Burkey, K. O. Burkey [email protected] U.S. Department of Agriculture, Agricultural Research Service, Plant Science Research, Department of Crop Science, North Carolina State University, 3127 Ligon Street, Raleigh, 27607 NC, USASearch for more papers by this author L. J. De Kok, L. J. De Kok [email protected] Laboratory of Plant Physiology, Groningen Institute for Evolutionary Life Sciences, University of Groningen, P.O. Box 11103, 9700 CC Groningen, The NetherlandsSearch for more papers by this authorD. A. Grantz, D. A. Grantz [email protected] Department of Botany and Plant Sciences, University of California, Riverside, Parlier, 93648 CA, USASearch for more papers by this authorK. O. Burkey, K. O. Burkey [email protected] U.S. Department of Agriculture, Agricultural Research Service, Plant Science Research, Department of Crop Science, North Carolina State University, 3127 Ligon Street, Raleigh, 27607 NC, USASearch for more papers by this author First published: 12 December 2015 https://doi.org/10.1111/plb.12413Citations: 1Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. References Burkhardt J., Pariyar S. (2016) How does the VDP response of isohydric and anisohydric plants depend on leaf surface particles? Plant Biology, 18 (Suppl. 1), 91– 100. Carta A., Probert R., Puglia G., Peruzzi L., Bedini G. (2016) Local climate explains degree of seed dormancy in Hypericum elodes L. (Hypericaceae). Plant Biology, 18 (Suppl. 1), 76– 82. Carvalho L.C., Coito J.L., Gonçalves E.F., Chaves M.M., Amâncio S. (2016) Differential physiological response of the grapevine varieties Touriga Nacional and Trincadeira to combined heat, drought and light stresses. Plant Biology, 18 (Suppl. 1), 101– 111. Chappelka A.H., Grulke N.E. (2016) Disruption of the ‘disease triangle’ by chemical and physical environmental change. Plant Biology, 18 (Suppl. 1), 5– 12. Chutteang C., Booker F.L., Na-Ngern P., Burton A., Aoki M., Burkey K.O. (2016) Biochemical and physiological processes associated with the differential ozone response in ozone-tolerant and sensitive soybean genotypes. Plant Biology, 18 (Suppl. 1), 28– 36. De Kok L.J., Hawkesford M.J. (2013) Plant functioning in a changing global and polluted environment. Environmental and Experimental Botany, 88, 1– 112. De Kok L.J., Stulen I., Grill D., Tausz M. (Eds) (2002) Special issue: responses of plant metabolism to air pollution and global change. Phyton, 42, 1– 172. Fusaro L., Gerosa G., Salvatori E., Marzuoli R., Monga R., Kuzminsky E., Angelaccio C., Quarato D., Fares S. (2016) Early and late adjustments of the photosynthetic traits and stomatal density in Quercus ilex L. grown in an ozone-enriched environment. Plant Biology, 18 (Suppl. 1), 13– 21. Gilliland N.J., Chappelka A.H., Muntifering R.B., Ditchkoff S.S. (2016) Changes in southern Piedmont grassland community structure and nutritive quality with future climate scenarios of elevated tropospheric ozone and altered rainfall patterns. Plant Biology, 18 (Suppl. 1), 47– 55. Goh H.-H., Khairudin K., Surkiran N.A., Normah M.N., Baharum S.N. (2016) Metabolite profiling reveals temperature effects on the VOCs and flavonoids of different plant populations. Plant Biology, 18 (Suppl. 1), 130– 139. Grantz D.A., Paudel R., Vu H.-B., Shrestha A., Grulke N.E. (2016) Diel trends in stomatal response to ozone and water deficit: a unique relationship of midday values to growth and allometry in Pima cotton? Plant Biology, 18 (Suppl. 1), 37– 46. Kitao M., Hida T., Eguchi N., Tobita H., Utsugi H., Uemura A., Kitaoka S., Koike T. (2016) Light compensation points in shade-grown seedlings of deciduous broadleaf tree species with different successional traits raised under elevated CO2. Plant Biology, 18 (Suppl. 1), 22– 27. Omasa K., Nouchi I., Goto E., Oki K., Shimizu Y., De Kok L.J., Grill D., Stulen I. (Eds) (2005) Special issue: plant responses to air pollution and global change. Phyton, 45, 1– 607. Reich M., van den Meerakker A.N., Parmar S., Hawkesford M.J., De Kok L.J. (2016) Temperature determines size and direction of effects of elevated CO2 and nitrogen form on yield quantity and quality of Chinese cabbage. Plant Biology, 18 (Suppl. 1), 63– 75. Rühl A.T., Eckstein R.L., Otte A., Donath T.W. (2016) Distinct germination response of endangered and common arable weeds to reduced water potential. Plant Biology, 18 (Suppl. 1), 83– 90. Sun C.X., Li M.Q., Gao X.X., Liu L.N., Wu X.F., Zhou J.H. (2016) Metabolic response of maize plants to multi-factorial abiotic stresses. Plant Biology, 18 (Suppl. 1), 120– 129. Tausz M., De Kok L.J. (Eds) (2009) Plant functioning in a changing global environment. Plant Biology, 11 (Suppl. 1), 1– 130. Tausz M., Dreyer E., De Kok L.J. (2009) Plant functioning in a changing global environment. Plant Biology, 11 (Suppl. 1), 1– 3. Visser E.J.W., Zhang Q., De Gruyter F., Martens S., Huber H. (2016) Shade affects responses to drought and flooding – acclimation to multiple stresses in bittersweet (Solanum dulcamara L.). Plant Biology, 18 (Suppl. 1), 112– 119. Watanabe M., Kitaoka S., Eguchi N., Watanabe Y., Satomura T., Takagi K., Satoh F., Koike T. (2016) Photosynthetic traits of Siebold's beech seedlings in changing light conditions by removal of shading trees under elevated CO2. Plant Biology, 18 (Suppl. 1), 56– 62. Citing Literature Volume18, IssueS1Special Issue: PLANTS AND THE CHANGING ENVIRONMENTJanuary 2016Pages 3-4 ReferencesRelatedInformation}, journal={PLANT BIOLOGY}, author={De Kok, L. J. and Grantz, D. A. and Burkey, K. O.}, year={2016}, month={Jan}, pages={3–4} }
 @article{hung_umstead_chen_holliday_kittur_henny_burkey_xie_2014, title={Differential expression of a novel gene EaF82a in green and yellow sectors of variegated Epipremnum aureum leaves is related to uneven distribution of auxin}, volume={152}, ISSN={["1399-3054"]}, DOI={10.1111/ppl.12219}, abstractNote={EaF82, a gene identified in previous studies of the variegated plant Epipremnum aureum, exhibited a unique expression pattern with greater transcript abundance in yellow sectors than green sectors of variegated leaves, but lower abundance in regenerated pale yellow plants than in green plants derived from leaf tissue culture. Studies of its full-length cDNA and promoter region revealed two members with only the EaF82a expressed. Immunoblotting confirmed that EaF82a encodes a 12 kDa protein and its accumulation consistent with its gene expression patterns in different color tissues. Transient expression of EaF82a-sGFP fusion proteins in protoplasts showed that EaF82a seems to be present in the cytosol as unidentified spots. Sequence motif search reveals a potential auxin responsive element in promoter region. Using transgenic Arabidopsis seedlings carrying EaF82a promoter driving the bacterial uidA (GUS) gene, an increased GUS activity was observed when IAA (indole-3-acetic acid) concentration was elevated. In E. aureum, EaF82a is more abundant at the site where axillary buds emerge and at the lower side of bending nodes where more IAA accumulates relative to the upper side. The measurement of endogenous IAA levels in different color tissues revealed the same pattern of IAA distribution as that of EaF82a expression, further supporting that EaF82a is an IAA responsive gene. EaF82a expression in etiolated transgenic Arabidopsis seedlings responded to IAA under the influence of light suggesting a microenvironment of uneven light condition affects the EaF82a transcript levels and protein accumulation in variegated leaves.}, number={4}, journal={PHYSIOLOGIA PLANTARUM}, author={Hung, Chiu-Yueh and Umstead, Makendra L. and Chen, Jianjun and Holliday, Bronwyn M. and Kittur, Farooqahmed S. and Henny, Richard J. and Burkey, Kent O. and Xie, Jiahua}, year={2014}, month={Dec}, pages={749–762} }
 @article{cheng_booker_burkey_tu_shew_rufty_fiscus_deforest_hu_2014, title={SOIL MICROBIAL RESPONSES TO ELEVATED CO2 AND O-3 IN A NITROGEN-AGGRADING AGROECOSYSTEM}, volume={6}, ISBN={["978-1-77188-021-3"]}, DOI={10.1371/journal.pone.0021377}, abstractNote={Climate change factors such as elevated atmospheric carbon dioxide (CO2) and ozone (O3) can exert significant impacts on soil microbes and the ecosystem level processes they mediate. However, the underlying mechanisms by which soil microbes respond to these environmental changes remain poorly understood. The prevailing hypothesis, which states that CO2- or O3-induced changes in carbon (C) availability dominate microbial responses, is primarily based on results from nitrogen (N)-limiting forests and grasslands. It remains largely unexplored how soil microbes respond to elevated CO2 and O3 in N-rich or N-aggrading systems, which severely hinders our ability to predict the long-term soil C dynamics in agroecosystems. Using a long-term field study conducted in a no-till wheat-soybean rotation system with open-top chambers, we showed that elevated CO2 but not O3 had a potent influence on soil microbes. Elevated CO2 (1.5×ambient) significantly increased, while O3 (1.4×ambient) reduced, aboveground (and presumably belowground) plant residue C and N inputs to soil. However, only elevated CO2 significantly affected soil microbial biomass, activities (namely heterotrophic respiration) and community composition. The enhancement of microbial biomass and activities by elevated CO2 largely occurred in the third and fourth years of the experiment and coincided with increased soil N availability, likely due to CO2-stimulation of symbiotic N2 fixation in soybean. Fungal biomass and the fungi∶bacteria ratio decreased under both ambient and elevated CO2 by the third year and also coincided with increased soil N availability; but they were significantly higher under elevated than ambient CO2. These results suggest that more attention should be directed towards assessing the impact of N availability on microbial activities and decomposition in projections of soil organic C balance in N-rich systems under future CO2 scenarios.}, number={6}, journal={CARBON CAPTURE AND STORAGE: CO2 MANAGEMENT TECHNOLOGIES}, author={Cheng, Lei and Booker, Fitzgerald L. and Burkey, Kent O. and Tu, Cong and Shew, H. David and Rufty, Thomas W. and Fiscus, Edwin L. and Deforest, Jared L. and Hu, Shuijin}, year={2014}, pages={277–307} }
 @article{cheng_booker_burkey_tu_shew_rufty_fiscus_deforest_hu_2014, title={Soil microbial responses to elevated CO2 and O-3 in a nitrogen-aggrading agroecosystem}, DOI={10.1201/b16845-14}, journal={Carbon Capture and Storage: CO2 Management Technologies}, author={Cheng, L. and Booker, F. L. and Burkey, K. O. and Tu, C. and Shew, H. D. and Rufty, T. W. and Fiscus, E. L. and Deforest, J. L. and Hu, Shuijin}, year={2014}, pages={277–307} }
 @article{hung_fan_kittur_sun_qiu_tang_holliday_xiao_burkey_bush_et al._2013, title={Alteration of the Alkaloid Profile in Genetically Modified Tobacco Reveals a Role of Methylenetetrahydrofolate Reductase in Nicotine N-Demethylation}, volume={161}, ISSN={["1532-2548"]}, DOI={10.1104/pp.112.209247}, abstractNote={Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme of the tetrahydrofolate (THF)-mediated one-carbon (C1) metabolic network. This enzyme catalyzes the reduction of 5,10-methylene-THF to 5-methyl-THF. The latter donates its methyl group to homocysteine, forming methionine, which is then used for the synthesis of S-adenosyl-methionine, a universal methyl donor for numerous methylation reactions, to produce primary and secondary metabolites. Here, we demonstrate that manipulating tobacco (Nicotiana tabacum) MTHFR gene (NtMTHFR1) expression dramatically alters the alkaloid profile in transgenic tobacco plants by negatively regulating the expression of a secondary metabolic pathway nicotine N-demethylase gene, CYP82E4. Quantitative real-time polymerase chain reaction and alkaloid analyses revealed that reducing NtMTHFR expression by RNA interference dramatically induced CYP82E4 expression, resulting in higher nicotine-to-nornicotine conversion rates. Conversely, overexpressing NtMTHFR1 suppressed CYP82E4 expression, leading to lower nicotine-to-nornicotine conversion rates. However, the reduced expression of NtMTHFR did not affect the methionine and S-adenosyl-methionine levels in the knockdown lines. Our finding reveals a new regulatory role of NtMTHFR1 in nicotine N-demethylation and suggests that the negative regulation of CYP82E4 expression may serve to recruit methyl groups from nicotine into the C1 pool under C1-deficient conditions.}, number={2}, journal={PLANT PHYSIOLOGY}, author={Hung, Chiu-Yueh and Fan, Longjiang and Kittur, Farooqahmed S. and Sun, Kehan and Qiu, Jie and Tang, She and Holliday, Bronwyn M. and Xiao, Bingguang and Burkey, Kent O. and Bush, Lowell P. and et al.}, year={2013}, month={Feb}, pages={1049–1060} }
 @article{grantz_vu_heath_burkey_2013, title={Demonstration of a diel trend in sensitivity of Gossypium to ozone: a step toward relating O-3 injury to exposure or flux}, volume={64}, ISSN={["1460-2431"]}, DOI={10.1093/jxb/ert032}, abstractNote={Plant injury by ozone (O3) occurs in three stages, O3 entrance through stomata, overcoming defences, and attack on bioreceptors. Concentration, deposition, and uptake of O3 are accessible by observation and modelling, while injury can be assessed visually or through remote sensing. However, the relationship between O3 metrics and injury is confounded by variation in sensitivity to O3. Sensitivity weighting parameters have previously been assigned to different plant functional types and growth stages, or by differentially weighting O3 concentrations, but diel and seasonal variability have not been addressed. Here a plant sensitivity parameter (S) is introduced, relating injury to O3 dose (uptake) using three independent injury endpoints in the crop species, Pima cotton (Gossypium barbadense). The diel variability of S was determined by assessment at 2h intervals. Pulses of O3 (15 min) were used to assess passive (constitutive) defence mechanisms and dose was used rather than concentration to avoid genetic or environmental effects on stomatal regulation. A clear diel trend in S was apparent, with maximal sensitivity in mid-afternoon, not closely related to gas exchange, whole leaf ascorbate, or total antioxidant capacity. This physiologically based sensitivity parameter provides a novel weighting factor to improve modelled relationships between either flux or exposure to O3, and O3 impacts. This represents a substantial improvement over concentration- or phenology-based weighting factors currently in use. Future research will be required to characterize the variability and metabolic drivers of diel changes in S, and the performance of this parameter in prediction of O3 injury.}, number={6}, journal={JOURNAL OF EXPERIMENTAL BOTANY}, author={Grantz, D. A. and Vu, H. -B. and Heath, R. L. and Burkey, K. O.}, year={2013}, month={Apr}, pages={1703–1713} }
 @article{rua_umbanhowar_hu_burkey_mitchell_2013, title={Elevated CO2 spurs reciprocal positive effects between a plant virus and an arbuscular mycorrhizal fungus}, volume={199}, ISSN={["1469-8137"]}, DOI={10.1111/nph.12273}, abstractNote={Plants form ubiquitous associations with diverse microbes. These interactions range from parasitism to mutualism, depending partly on resource supplies that are being altered by global change. While many studies have considered the separate effects of pathogens and mutualists on their hosts, few studies have investigated interactions among microbial mutualists and pathogens in the context of global change. Using two wild grass species as model hosts, we grew individual plants under ambient or elevated CO(2), and ambient or increased soil phosphorus (P) supply. Additionally, individuals were grown with or without arbuscular mycorrhizal inoculum, and after 2 wk, plants were inoculated or mock-inoculated with a phloem-restricted virus. Under elevated CO(2), mycorrhizal association increased the titer of virus infections, and virus infection reciprocally increased the colonization of roots by mycorrhizal fungi. Additionally, virus infection decreased plant allocation to root biomass, increased leaf P, and modulated effects of CO(2) and P addition on mycorrhizal root colonization. These results indicate that plant mutualists and pathogens can alter each other's success, and predict that these interactions will respond to increased resource availability and elevated CO(2). Together, our findings highlight the importance of interactions among multiple microorganisms for plant performance under global change.}, number={2}, journal={NEW PHYTOLOGIST}, author={Rua, Megan A. and Umbanhowar, James and Hu, Shuijin and Burkey, Kent O. and Mitchell, Charles E.}, year={2013}, month={Jul}, pages={541–549} }
 @article{burkey_booker_ainsworth_nelson_2012, title={Field assessment of a snap bean ozone bioindicator system under elevated ozone and carbon dioxide in a free air system}, volume={166}, ISSN={["1873-6424"]}, DOI={10.1016/j.envpol.2012.03.020}, abstractNote={Ozone-sensitive (S156) and -tolerant (R123 and R331) genotypes of snap bean (Phaseolus vulgaris L.) were tested as a plant bioindicator system for detecting O3 effects at current and projected future levels of tropospheric O3 and atmospheric CO2 under field conditions. Plants were treated with ambient air, 1.4× ambient O3 and 550 ppm CO2 separately and in combination using Free Air Concentration Enrichment technology. Under ambient O3 concentrations pod yields were not significantly different among genotypes. Elevated O3 reduced pod yield for S156 (63%) but did not significantly affect yields for R123 and R331. Elevated CO2 at 550 ppm alone did not have a significant impact on yield for any genotype. Amelioration of the O3 effect occurred in the O3 + CO2 treatment. Ratios of sensitive to tolerant genotype pod yields were identified as a useful measurement for assessing O3 impacts with potential applications in diverse settings including agricultural fields.}, journal={ENVIRONMENTAL POLLUTION}, author={Burkey, Kent O. and Booker, Fitzgerald L. and Ainsworth, Elizabeth A. and Nelson, Randall L.}, year={2012}, month={Jul}, pages={167–171} }
 @article{fiscus_booker_sadok_burkey_2012, title={Influence of atmospheric vapour pressure deficit on ozone responses of snap bean (Phaseolus vulgaris L.) genotypes}, volume={63}, ISSN={["1460-2431"]}, DOI={10.1093/jxb/err443}, abstractNote={Environmental conditions influence plant responses to ozone (O(3)), but few studies have evaluated individual factors directly. In this study, the effect of O(3) at high and low atmospheric vapour pressure deficit (VPD) was evaluated in two genotypes of snap bean (Phaseolus vulgaris L.) (R123 and S156) used as O(3) bioindicator plants. Plants were grown in outdoor controlled-environment chambers in charcoal-filtered air containing 0 or 60 nl l(-1) O(3) (12 h average) at two VPDs (1.26 and 1.96 kPa) and sampled for biomass, leaf area, daily water loss, and seed yield. VPD clearly influenced O(3) effects. At low VPD, O(3) reduced biomass, leaf area, and seed yield substantially in both genotypes, while at high VPD, O(3) had no significant effect on these components. In clean air, high VPD reduced biomass and yield by similar fractions in both genotypes compared with low VPD. Data suggest that a stomatal response to VPD per se may be lacking in both genotypes and it is hypothesized that the high VPD resulted in unsustainable transpiration and water deficits that resulted in reduced growth and yield. High VPD- and water-stress-induced stomatal responses may have reduced the O(3) flux into the leaves, which contributed to a higher yield compared to the low VPD treatment in both genotypes. At low VPD, transpiration increased in the O(3) treatment relative to the clean air treatment, suggesting that whole-plant conductance was increased by O(3) exposure. Ozone-related biomass reductions at low VPD were proportionally higher in S156 than in R123, indicating that differential O(3) sensitivity of these bioindicator plants remained evident when environmental conditions were conducive for O(3) effects. Assessments of potential O(3) impacts on vegetation should incorporate interacting factors such as VPD.}, number={7}, journal={JOURNAL OF EXPERIMENTAL BOTANY}, author={Fiscus, Edwin L. and Booker, Fitzgerald L. and Sadok, Walid and Burkey, Kent O.}, year={2012}, month={Apr}, pages={2557–2564} }
 @article{hung_sun_chen_darlington_williams_burkey_xie_2010, title={Identification of a Mg-protoporphyrin IX monomethyl ester cyclase homologue, EaZIP, differentially expressed in variegated Epipremnum aureum 'Golden Pothos' is achieved through a unique method of comparative study using tissue regenerated plants}, volume={61}, ISSN={["1460-2431"]}, DOI={10.1093/jxb/erq020}, abstractNote={Variegated plants provide a valuable tool for studying chloroplast biogenesis by allowing direct comparison between green and white/yellow sectors within the same leaf. While variegated plants are abundant in nature, the mechanism of leaf variegation remains largely unknown. Current studies are limited to a few mutants in model plant species, and are complicated by the potential for cross-contamination during dissection of leaf tissue into contrasting sectors. To overcome these obstacles, an alternative approach was explored using tissue-culture techniques to regenerate plantlets from unique sectors. Stable green and pale yellow plants were developed from a naturally variegated Epipremnum aureum ‘Golden Pothos’. By comparing the gene expression between green and pale yellow plants using suppression subtractive hybridization in conjunction with homologous sequence search, nine down-regulated and 18 up-regulated genes were identified in pale yellow plants. Transcript abundance for EaZIP (Epipremnum aureum leucine zipper), a nuclear gene homologue of tobacco NTZIP and Arabidopsis CHL27, was reduced more than 4000-fold in qRT-PCR analysis. EaZIP encodes the Mg-protoporphyrin IX monomethyl ester cyclase, one of the key enzymes in the chlorophyll biosynthesis pathway. Examination of EaZIP expression in naturally variegated ‘Golden Pothos’ confirmed that EaZIP transcript levels were correlated with leaf chlorophyll contents, suggesting that this gene plays a major role in the loss of chlorophyll in the pale yellow sectors of E. aureum ‘Golden Pothos’. This study further suggests that tissue-culture regeneration of plantlets from different coloured sectors of variegated leaves can be used to investigate the underlying mechanisms of variegation.}, number={5}, journal={JOURNAL OF EXPERIMENTAL BOTANY}, author={Hung, Chiu-Yueh and Sun, Ying-Hsuan and Chen, Jianjun and Darlington, Diane E. and Williams, Alfred L. and Burkey, Kent O. and Xie, Jiahua}, year={2010}, month={Mar}, pages={1483–1493} }
 @article{tu_booker_burkey_hu_2009, title={Elevated Atmospheric Carbon Dioxide and O-3 Differentially Alter Nitrogen Acquisition in Peanut}, volume={49}, ISSN={["1435-0653"]}, DOI={10.2135/cropsci2008.10.0603}, abstractNote={ABSTRACT Elevated atmospheric CO 2 and ozone (O 3 ) may affect productivity of legumes in part by altering symbiotic N 2 fixation. To investigate this possibility, measurements of plant biomass, N levels and natural 15 N abundance (δ 15 N) were used to examine the effects of elevated CO 2 and O 3 on N acquisition in field‐grown peanut ( Arachis hypogaea L.) using open‐top chambers. Seasonal 12‐h daily average CO 2 treatment concentrations were 376, 550, and 730 μmol mol −1 Carbon dioxide treatments were applied in reciprocal combinations with seasonal 12‐h daily average O 3 concentrations of 21, 49, and 79 nmol mol −1 At mid‐vegetative growth, elevated CO 2 significantly reduced leaf N concentrations by up to 44%, but not δ 15 N values. Elevated O 3 did not significantly affect N concentrations or δ 15 N values. At harvest, plant N concentrations were similar among treatments except for a 14% reduction in the highest‐level CO 2 –O 3 treatment. Plant N accumulation varied in proportion with treatment effects on biomass production, which was increased with elevated CO 2 when averaged over the O 3 treatments and suppressed by high‐level O 3 at ambient CO 2 Elevated CO 2 reduced plant δ 15 N values in low‐ and mid‐level O 3 treatments while mid‐ and high‐level O 3 increased them at ambient CO 2 The changes in δ 15 N values suggested that N 2 fixation activity was stimulated with elevated CO 2 and inhibited by elevated O 3 Elevated CO 2 ameliorated detrimental O 3 effects to varying extents depending on the concentrations of the two gases. These results indicated that interactions between CO 2 and O 3 on plant physiology can alter N acquisition processes, with impacts on peanut productivity likely dependent in part on these changes.}, number={5}, journal={CROP SCIENCE}, author={Tu, Cong and Booker, Fitzgerald L. and Burkey, Kent O. and Hu, Shuijin}, year={2009}, pages={1827–1836} }
 @article{burkey_carter_2009, title={Foliar resistance to ozone injury in the genetic base of US and Canadian soybean and prediction of resistance in descendent cultivars using coefficient of parentage}, volume={111}, ISSN={["0378-4290"]}, DOI={10.1016/j.fcr.2008.12.005}, abstractNote={Development of ozone (O3)-resistant cultivars is a potentially important approach for maintaining crop productivity under future climate scenarios in which tropospheric O3 pollution is projected to rise. A first step in the breeding of resistant cultivars for a crop such as soybean (Glycine max (L.) Merr.) is identification of sources of O3 resistance genes. Thirty ancestral lines of soybean were screened for differences in O3 foliar injury under greenhouse conditions. The ancestors represented 92% of the genetic base of North American soybean as determined by pedigree analysis. Injury among ancestors ranged from 5 to 50% of leaf area, based on response of the five oldest main stem leaves, indicating both the presence of substantial genetic variation for O3 injury among the ancestors as well as resistance levels greater than that of the standard control cultivar, resistant Essex (15% injury). Ancestral types Fiskeby 840-7-3 and Fiskeby III exhibited the greatest foliar resistance and PI 88788 the least. A subsequent field study confirmed the foliar resistance of the Fiskeby types. Resistant ancestors identified here are proposed for inheritance and DNA mapping studies to determine the genetic basis of foliar resistance. Because the presence of O3-resistant ancestors suggested that resistant descendents may exist in addition to the resistant control Essex, a method was developed to facilitate their identification. A predicted O3-resistance score was calculated for 247 publicly-released cultivars, based on pedigree analysis and ancestral response to ozone. Using this approach, the 32 public cultivars most closely related to resistant ancestors and, thus, most likely to be resistant were identified as priority candidates for future screening efforts. Predicted scores from the analysis suggested that cultivars from the Midwest may be more sensitive to foliar injury, on average, than Southern cultivars.}, number={3}, journal={FIELD CROPS RESEARCH}, author={Burkey, Kent O. and Carter, Thomas E., Jr.}, year={2009}, month={Apr}, pages={207–217} }
 @misc{booker_muntifering_mcgrath_burkey_decoteau_fiscus_manning_krupa_chappelka_grantz_2009, title={The Ozone Component of Global Change: Potential Effects on Agricultural and Horticultural Plant Yield, Product Quality and Interactions with Invasive Species}, volume={51}, ISSN={["1744-7909"]}, DOI={10.1111/j.1744-7909.2008.00805.x}, abstractNote={The productivity, product quality and competitive ability of important agricultural and horticultural plants in many regions of the world may be adversely affected by current and anticipated concentrations of ground-level ozone (O3). Exposure to elevated O3 typically results in suppressed photosynthesis, accelerated senescence, decreased growth and lower yields. Various approaches used to evaluate O3 effects generally concur that current yield losses range from 5% to 15% among sensitive plants. There is, however, considerable genetic variability in plant responses to O3. To illustrate this, we show that ambient O3 concentrations in the eastern United States cause substantially different levels of damage to otherwise similar snap bean cultivars. Largely undesirable effects of O3 can also occur in seed and fruit chemistry as well as in forage nutritive value, with consequences for animal production. Ozone may alter herbicide efficacy and foster establishment of some invasive species. We conclude that current and projected levels of O3 in many regions worldwide are toxic to sensitive plants of agricultural and horticultural significance. Plant breeding that incorporates O3 sensitivity into selection strategies will be increasingly necessary to achieve sustainable production with changing atmospheric composition, while reductions in O3 precursor emissions will likely benefit world food production and reduce atmospheric concentrations of an important greenhouse gas.}, number={4}, journal={JOURNAL OF INTEGRATIVE PLANT BIOLOGY}, author={Booker, Fitzgerald and Muntifering, Russell and McGrath, Margaret and Burkey, Kent and Decoteau, Dennis and Fiscus, Edwin and Manning, William and Krupa, Sagar and Chappelka, Arthur and Grantz, David}, year={2009}, month={Apr}, pages={337–351} }
 @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 CO 2 and ozone (O 3 ) 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 CO 2 and O 3 mixtures on leaf gas‐exchange, harvest biomass, and leaf chemistry in peanut ( Arachis hypogaea L.), an O 3 –sensitive species, using open‐top field chambers. Treatments included ambient CO 2 (about 375 μmol mol −1 ) and CO 2 enrichment of approximately 173 and 355 μmol mol −1 in combination with charcoal‐filtered air (22 nmol O 3 mol −1 ), nonfiltered air (46 nmol O 3 mol −1 ), and nonfiltered air plus O 3 (75 nmol O 3 mol −1 ). Twice‐ambient CO 2 in charcoal‐filtered air increased A by 23% while decreasing seasonal stomatal conductance (g s ) by 42%. Harvest biomass was increased 12 to 15% by elevated CO 2 In ambient CO 2 , nonfiltered air and added O 3 lowered A by 21% and 48%, respectively, while added O 3 reduced g s by 18%. Biomass was not significantly affected by nonfiltered air, but was 40% lower in the added O 3 treatment. Elevated CO 2 generally suppressed inhibitory effects of O 3 on A and harvest biomass. Leaf starch concentration was increased by elevated CO 2 and decreased by O 3 Treatment effects on foliar N and total phenolic concentrations were minor. Increasing atmospheric CO 2 concentrations should attenuate detrimental effects of ambient O 3 and promote growth in peanut but its effectiveness declines with increasing O 3 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{cheng_burkey_robinson_booker_2007, title={Leaf extracellular ascorbate in relation to O(3) tolerance of two soybean cultivars}, volume={150}, ISSN={["0269-7491"]}, DOI={10.1016/j.envpol.2007.01.022}, abstractNote={Soybean [Glycine max (L.) Merr.] cultivars Essex and Forrest that exhibit differences in ozone (O3) sensitivity were used in greenhouse experiments to investigate the role of leaf extracellular antioxidants in O3 injury responses. Charcoal-filtered air and elevated O3 conditions were used to assess genetic, leaf age, and O3 effects. In both cultivars, the extracellular ascorbate pool consisted of 80–98% dehydroascorbic acid, the oxidized form of ascorbic acid (AA) that is not an antioxidant. For all combinations of genotype and O3 treatments, extracellular AA levels were low (1–30 nmol g−1 FW) and represented 3–30% of the total antioxidant capacity. Total extracellular antioxidant capacity was twofold greater in Essex compared with Forrest, consistent with greater O3 tolerance of Essex. The results suggest that extracellular antioxidant metabolites in addition to ascorbate contribute to detoxification of O3 in soybean leaves and possibly affect plant sensitivity to O3 injury.}, number={3}, journal={ENVIRONMENTAL POLLUTION}, author={Cheng, Fang-Yi and Burkey, Kent O. and Robinson, J. Michael and Booker, Fitzgerald L.}, year={2007}, month={Dec}, pages={355–362} }
 @article{chen_tu_burton_watson_burkey_hu_2007, title={Plant nitrogen acquisition and interactions under elevated carbon dioxide: impact of endophytes and mycorrhizae}, volume={13}, ISSN={["1365-2486"]}, DOI={10.1111/j.1365-2486.2007.01347.x}, abstractNote={Both endophytic and mycorrhizal fungi interact with plants to form symbiosis in which the fungal partners rely on, and sometimes compete for, carbon (C) sources from their hosts. Changes in photosynthesis in host plants caused by atmospheric carbon dioxide (CO2) enrichment may, therefore, influence those mutualistic interactions, potentially modifying plant nutrient acquisition and interactions with other coexisting plant species. However, few studies have so far examined the interactive controls of endophytes and mycorrhizae over plant responses to atmospheric CO2 enrichment. Using Festuca arundinacea Schreb and Plantago lanceolata L. as model plants, we examined the effects of elevated CO2 on mycorrhizae and endophyte (Neotyphodium coenophialum) and plant nitrogen (N) acquisition in two microcosm experiments, and determined whether and how mycorrhizae and endophytes mediate interactions between their host plant species. Endophyte-free and endophyte-infected F. arundinacea varieties, P. lanceolata L., and their combination with or without mycorrhizal inocula were grown under ambient (400 μmol mol−1) and elevated CO2 (ambient + 330 μmol mol−1). A 15N isotope tracer was used to quantify the mycorrhiza-mediated plant acquisition of N from soil. Elevated CO2 stimulated the growth of P. lanceolata greater than F. arundinacea, increasing the shoot biomass ratio of P. lanceolata to F. arundinacea in all the mixtures. Elevated CO2 also increased mycorrhizal root colonization of P. lanceolata, but had no impact on that of F. arundinacea. Mycorrhizae increased the shoot biomass ratio of P. lanceolata to F. arundinacea under elevated CO2. In the absence of endophytes, both elevated CO2 and mycorrhizae enhanced 15N and total N uptake of P. lanceolata but had either no or even negative effects on N acquisition of F. arundinacea, altering N distribution between these two species in the mixture. The presence of endophytes in F. arundinacea, however, reduced the CO2 effect on N acquisition in P. lanceolata, although it did not affect growth responses of their host plants to elevated CO2. These results suggest that mycorrhizal fungi and endophytes might interactively affect the responses of their host plants and their coexisting species to elevated CO2.}, number={6}, journal={GLOBAL CHANGE BIOLOGY}, author={Chen, Xin and Tu, Cong and Burton, Michael G. and Watson, Dorothy M. and Burkey, Kent O. and Hu, Shuijin}, year={2007}, month={Jun}, pages={1238–1249} }
 @article{souza_neufeld_chappelka_burkey_davison_2006, title={Seasonal development of ozone-induced foliar injury on tall milkweed (Asclepias exaltata) in Great Smoky Mountains National Park}, volume={141}, ISSN={["0269-7491"]}, DOI={10.1016/j.envpol.2005.07.022}, abstractNote={The goals of this study were to document the development of ozone-induced foliar injury, on a leaf-by-leaf basis, and to develop ozone exposure relationships for leaf cohorts and individual tall milkweeds (Asclepias exaltata L.) in Great Smoky Mountains National Park. Plants were classified as either ozone-sensitive or insensitive based on the amount of foliar injury. Sensitive plants developed injury earlier in the season and to a greater extent than insensitive plants. Older leaf cohorts were more likely to belong to high injury classes by the end of each of the two growing seasons. In addition, leaf loss was more likely for older cohorts (2000) and lower leaf positions (2001) than younger cohorts and upper leaves, respectively. Most leaves abscised without prior ozone-like stippling or chlorosis. Failure to take this into account can result in underestimation of the effects of ozone on these plants.}, number={1}, journal={ENVIRONMENTAL POLLUTION}, author={Souza, L and Neufeld, HS and Chappelka, AH and Burkey, KO and Davison, AW}, year={2006}, month={May}, pages={175–183} }
 @article{burkey_neufeld_souza_chappelka_davison_2006, title={Seasonal profiles of leaf ascorbic acid content and redox state in ozone-sensitive wildflowers}, volume={143}, ISSN={["0269-7491"]}, DOI={10.1016/j.envpol.2005.12.009}, abstractNote={Cutleaf coneflower (Rudbeckia laciniata L.), crown-beard (Verbesina occidentalis Walt.), and tall milkweed (Asclepias exaltata L.) are wildflower species native to Great Smoky Mountains National Park (U.S.A.). Natural populations of each species were analyzed for leaf ascorbic acid (AA) and dehydroascorbic acid (DHA) to assess the role of ascorbate in protecting the plants from ozone stress. Tall milkweed contained greater quantities of AA (7–10 μmol g−1 fresh weight) than crown-beard (2–4 μmol g−1 fresh weight) or cutleaf coneflower (0.5–2 μmol g−1 fresh weight). DHA was elevated in crown-beard and cutleaf coneflower relative to tall milkweed suggesting a diminished capacity for converting DHA into AA. Tall milkweed accumulated AA in the leaf apoplast (30–100 nmol g−1 fresh weight) with individuals expressing ozone foliar injury symptoms late in the season having less apoplast AA. In contrast, AA was not present in the leaf apoplast of either crown-beard or cutleaf coneflower. Unidentified antioxidant compounds were present in the leaf apoplast of all three species. Overall, distinct differences in antioxidant metabolism were found in the wildflower species that corresponded with differences in ozone sensitivity.}, number={3}, journal={ENVIRONMENTAL POLLUTION}, author={Burkey, Kent O. and Neufeld, Howard S. and Souza, Lara and Chappelka, Arthur H. and Davison, Alan W.}, year={2006}, month={Oct}, pages={427–434} }
 @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_burkey_overmyer_jones_2004, title={Differential responses of G-protein Arabidopsis thaliana mutants to ozone}, volume={162}, ISSN={["1469-8137"]}, DOI={10.1111/j.1469-8137.2004.01081.x}, abstractNote={• Ground-level ozone (O3) curtails agricultural production in many regions worldwide. However, the etiology of O3 toxicity remains unclear. Activated oxygen species appear to inflict biochemical lesions and propagate defense responses that compound plant injury. Because some plant defense responses involve membrane-delimited GTPases (G proteins), we evaluated the O3 sensitivity of Arabidopsis mutants altered in the heterotrimeric G-protein pathway. • Eight genotypes were treated with a range of O3 concentrations (0, 100, 175 and 250 nmol mol−1) for 13 d in controlled environment chambers. • After treatment with O3, the epinasty typically observed for wild type leaves did not occur in mutant plants lacking the alpha subunit of the G-protein complex (gpa1). O3-induced suppression of leaf chlorophyll levels and leaf mass per unit leaf area were less for gpa1 mutants and were not due to differences in O3 flux. • There was a positive correlation between the lack of a G-protein alpha subunit and decreased O3 sensitivity. Our results suggest that a heterotrimeric G-protein is critically involved in the expression of O3 effects in plants.}, number={3}, journal={NEW PHYTOLOGIST}, author={Booker, FL and Burkey, KO and Overmyer, K and Jones, AM}, year={2004}, month={Jun}, pages={633–641} }
 @article{burkey_eason_fiscus_2003, title={Factors that affect leaf extracellular ascorbic acid content and redox status}, volume={117}, ISSN={["1399-3054"]}, DOI={10.1034/j.1399-3054.2003.1170106.x}, abstractNote={Leaf ascorbic acid content and redox status were compared in ozone-tolerant (Provider) and ozone-sensitive (S156) genotypes of snap bean (Phaseolus vulgaris L.). Plants were grown in pots for 24 days under charcoal-filtered air (CF) conditions in open-top field chambers and then maintained as CF controls (29 nmol mol−1 ozone) or exposed to elevated ozone (71 nmol mol−1 ozone). Following a 10-day treatment, mature leaves of the same age were harvested early in the morning (06:00–08:00 h) or in the afternoon (13:00–15:00 h) for analysis of ascorbic acid (AA) and dehydroascorbic acid (DHA). Vacuum infiltration methods were used to separate leaf AA into apoplast and symplast fractions. The total ascorbate content [AA + DHA] of leaf tissue averaged 28% higher in Provider relative to S156, and Provider exhibited a greater capacity to maintain [AA + DHA] content under ozone stress. Apoplast [AA + DHA] content was 2-fold higher in tolerant Provider (360 nmol g−1 FW maximum) relative to sensitive S156 (160 nmol g−1 FW maximum) regardless of sampling period or treatment, supporting the hypothesis that extracellular AA is a factor in ozone tolerance. Apoplast [AA + DHA] levels were significantly higher in the afternoon than early morning for both genotypes, evidence for short-term regulation of extracellular ascorbate content. Total leaf ascorbate was primarily reduced with AA/[AA + DHA] ratios of 0.81–0.90. In contrast, apoplast AA/[AA + DHA] ratios were 0.01–0.60 and depended on genotype and ozone treatment. Provider exhibited a greater capacity to maintain extracellular AA/[AA + DHA] ratios under ozone stress, suggesting that ozone tolerance is associated with apoplast ascorbate redox status.}, number={1}, journal={PHYSIOLOGIA PLANTARUM}, author={Burkey, KO and Eason, G and Fiscus, EL}, year={2003}, month={Jan}, pages={51–57} }
 @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{burkey_eason_2002, title={Ozone tolerance in snap bean is associated with elevated ascorbic acid in the leaf apoplast}, volume={114}, ISSN={["1399-3054"]}, DOI={10.1034/j.1399-3054.2002.1140308.x}, abstractNote={Ascorbic acid (AA) in the leaf apoplast has the potential to limit ozone injury by participating in reactions that detoxify ozone and reactive oxygen intermediates and thus prevent plasma membrane damage. Genotypes of snap bean (Phaseolus vulgaris L) were compared in controlled environments and in open-top field chambers to assess the relationship between extracellular AA content and ozone tolerance. Vacuum infiltration methods were employed to separate leaf AA into extracellular and intracellular fractions. For plants grown in controlled environments at low ozone concentration (4 nmol mol-1 ozone), leaf apoplast AA was significantly higher in tolerant genotypes (300-400 nmol g-1 FW) compared with sensitive genotypes (approximately 50 nmol g-1 FW), evidence that ozone tolerance is associated with elevated extracellular AA. For the open top chamber study, plants were grown in pots under charcoal-filtered air (CF) conditions and then either maintained under CF conditions (29 nmol mol-1 ozone) or exposed to elevated ozone (67 nmol mol-1 ozone). Following an 8-day treatment period, leaf apoplast AA was in the range of 100-190 nmol g-1 FW for all genotypes, but no relationship was observed between apoplast AA content and ozone tolerance. The contrasting results in the two studies demonstrated a potential limitation in the interpretation of extracellular AA data. Apoplast AA levels presumably reflect the steady-state condition between supply from the cytoplasm and utilization within the cell wall. The capacity to detoxify ozone in the extracellular space may be underestimated under elevated ozone conditions where the dynamics of AA supply and utilization are not adequately represented by a steady-state measurement.}, number={3}, journal={PHYSIOLOGIA PLANTARUM}, author={Burkey, KO and Eason, G}, year={2002}, month={Mar}, pages={387–394} }
 @article{krupa_mcgrath_andersen_booker_burkey_chappelka_chevone_pell_zilinskas_2001, title={Ambient ozone and plant health}, volume={85}, ISSN={["0191-2917"]}, DOI={10.1094/PDIS.2001.85.1.4}, abstractNote={HomePlant DiseaseVol. 85, No. 1Ambient Ozone and Plant Health PreviousNext OPENOpen Access licenseAmbient Ozone and Plant HealthSagar Krupa, Margaret Tuttle McGrath, Christian P. Andersen, Fitzgerald L. Booker, Kent O. Burkey, Arthur H. Chappelka, Boris I. Chevone, Eva J. Pell, and Barbara A. ZilinskasSagar KrupaSearch for more papers by this author, Margaret Tuttle McGrathSearch for more papers by this author, Christian P. AndersenSearch for more papers by this author, Fitzgerald L. BookerSearch for more papers by this author, Kent O. BurkeySearch for more papers by this author, Arthur H. ChappelkaSearch for more papers by this author, Boris I. ChevoneSearch for more papers by this author, Eva J. PellSearch for more papers by this author, and Barbara A. ZilinskasSearch for more papers by this authorAffiliationsAuthors and Affiliations Sagar Krupa , University of Minnesota, St. Paul Margaret Tuttle McGrath , Cornell University, Riverhead, NY Christian P. Andersen , U.S. Environmental Protection Agency, Corvallis, OR Fitzgerald L. Booker Kent O. Burkey , USDA-ARS Air Quality Research Unit, North Carolina State University, Raleigh Arthur H. Chappelka , Auburn University, Auburn, AL Boris I. Chevone , Virginia Polytechnic Institute & State University, Blacksburg Eva J. Pell , Pennsylvania State University, University Park Barbara A. Zilinskas , Rutgers University, New Brunswick, NJ Published Online:23 Feb 2007https://doi.org/10.1094/PDIS.2001.85.1.4AboutSectionsPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat DetailsFiguresLiterature CitedRelated Vol. 85, No. 1 January 2001SubscribeISSN:0191-2917e-ISSN:1943-7692 Metrics Article History Issue Date: 25 Jan 2008Published: 23 Feb 2007 Pages: 4-12 Information© 2000 The American Phytopathological SocietyPDF downloadCited byAcute ozone exposure decreases terpene emissions from Canary Island pinesAgricultural and Forest Meteorology, Vol. 333Physiological status of House Sparrows (Passer domesticus) along an ozone pollution gradient21 February 2023 | Ecotoxicology, Vol. 32, No. 2Impacts of Agricultural Soil NO x Emissions on O 3 Over Mainland China11 February 2023 | Journal of Geophysical Research: Atmospheres, Vol. 128, No. 4Improvement of local ozone phytotoxicity modelling for autochthonous grape 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Cogn., a native Atlantic Forest species, as a bio-indicator of ozone: Visible injuryEnvironmental Pollution, Vol. 152, No. 2Visible leaf injury in young trees of Fagus sylvatica L. and Quercus robur L. in relation to ozone uptake and ozone exposure. An Open-Top Chambers experiment in South Alpine environmental conditionsEnvironmental Pollution, Vol. 152, No. 2Ecotoxicology of ozone: Bioactivation of extracellular ascorbateBiochemical and Biophysical Research Communications, Vol. 366, No. 2Avaliação da sensibilidade de plantas jovens de quiabo (Abelmoschus esculentus (L.) Moench. - Malvaceae) ao ozônioHoehnea, Vol. 35, No. 3Effect of Air Pollution and Ethylene Diurea on Broad Bean Plants Grown at Two Localities in KSAInternational Journal of Botany, Vol. 4, No. 1Oxidative Stress, the Paradigm of Ozone Toxicity in Plants and Animals11 October 2007 | Water, Air, and Soil Pollution, Vol. 187, No. 1-4Foliar, Physiologial and Growth Responses of Four Maple Species Exposed to Ozone10 July 2007 | Water, Air, and Soil Pollution, Vol. 185, No. 1-4Response of gas exchange and yield components of field-grown Triticum aestivum L. to elevated ozone in ChinaPhotosynthetica, Vol. 45, No. 3Ozone Reactivity and Free Radical Scavenging Behavior of Phenolic Secondary Metabolites in Lichens Exposed to Chronic Oxidant Air Pollution from Mexico City10 July 2007 | Journal of Chemical Ecology, Vol. 33, No. 8Influence of elevated CO2 and ozone concentrations on late blight resistance and growth of potato plantsEnvironmental and Experimental Botany, Vol. 60, No. 3Expression of the rice cytoplasmic cysteine synthase gene in tobacco reduces ozone-induced damage19 April 2007 | Plant Biotechnology Reports, Vol. 1, No. 2Perspectives regarding 50years of research on effects of tropospheric ozone air pollution on US forestsEnvironmental Pollution, Vol. 147, No. 3Psidium guajava ‘Paluma’ (the guava plant) as a new bio-indicator of ozone in the tropicsEnvironmental Pollution, Vol. 147, No. 3Assessment of Vegetation Stress Using Reflectance or Fluorescence Measurements1 May 2007 | Journal of Environmental Quality, Vol. 36, No. 3Ozone stress and antioxidant substances in Trifolium repens and Centaurea jacea leavesEnvironmental Pollution, Vol. 146, No. 3Variations and trends of ground-level ozone and AOT40 in the rural areas of Lithuania5 August 2006 | Environmental Monitoring and Assessment, Vol. 127, No. 1-3Ozone-induced foliar injury in saplings of Psidium guajava ‘Paluma’ in São Paulo, BrazilChemosphere, Vol. 66, No. 7Alterações bioquímicas associadas a injúrias foliares visíveis em plantas jovens de Psidium guajava 'Paluma' mantidas em ambiente contaminado por ozônioHoehnea, Vol. 34, No. 2Tropospheric Ozone and Interspecific Competition between Yellow Nutsedge and Pima Cotton1 September 2006 | Crop Science, Vol. 46, No. 5Soil respiration in northern forests exposed to elevated atmospheric carbon dioxide and ozone18 February 2006 | Oecologia, Vol. 148, No. 3Interannual climatic variation mediates elevated CO 2 and O 3 effects on forest growth19 April 2006 | Global Change Biology, Vol. 12, No. 6Visible foliar injury caused by ozone alters the relationship between SPAD meter readings and chlorophyll concentrations in cutleaf coneflower26 January 2006 | Photosynthesis Research, Vol. 87, No. 3Efficacy of OxiDate™ for Control of Early Blight (Alternaria solani) in Potato StoragesPlant Pathology Journal, Vol. 4, No. 1Tropospheric O 3 compromises net primary production in young stands of trembling aspen, paper birch and sugar maple in response to elevated atmospheric CO 22 September 2005 | New Phytologist, Vol. 168, No. 3Growth Parameters and Resistance against Drechslera teres of Spring Barley (Hordeum vulgare L. cv. Scarlett) Grown at Elevated Ozone and Carbon Dioxide ConcentrationsPlant Biology, Vol. 7, No. 6Role of ethylene diurea (EDU) in assessing impact of ozone on Vigna radiata L. plants in a suburban area of Allahabad (India)Chemosphere, Vol. 61, No. 2Air pollution, precipitation chemistry and forest health in the Retezat Mountains, Southern Carpathians, RomaniaEnvironmental Pollution, Vol. 137, No. 3Assessment of Ambient Ozone Effects on Vegetation Using Snap Bean as a Bioindicator Species1 May 2005 | Journal of Environmental Quality, Vol. 34, No. 3Gesunde Pflanzen unter zuk�nftigem Klima14 December 2004 | Gesunde Pflanzen, Vol. 57, No. 1ENVIRONMENTAL FACTORS THAT CAUSE PLANT DISEASESA chamberless field exposure system for ozone enrichment of short vegetationEnvironmental Pollution, Vol. 133, No. 1Elevated CO2 protects poplar (Populus trichocarpa × P. deltoides) from damage induced by O3: identification of mechanismsFunctional Plant Biology, Vol. 32, No. 3Effects of ozone on the foliar histology of the mastic plant (Pistacia lentiscus L.)Environmental Pollution, Vol. 132, No. 2Aphid individual performance may not predict population responses to elevated CO 2 or O 35 July 2004 | Global Change Biology, Vol. 10, No. 8Responses of hybrid poplar clones and red maple seedlings to ambient O3 under differing light within a mixed hardwood forestEnvironmental Pollution, Vol. 130, No. 2Ecophysiological and biochemical strategies of response to ozone in Mediterranean evergreen broadleaf speciesAtmospheric Environment, Vol. 38, No. 15Ambient flux-based critical values of ozone for protecting vegetation: differing spatial scales and uncertainties in risk assessmentAtmospheric Environment, Vol. 38, No. 15Ozone impacts on cotton: towards an integrated mechanismEnvironmental Pollution, Vol. 126, No. 3Field crop responses to ultraviolet-B radiation: a reviewAgricultural and Forest Meteorology, Vol. 120, No. 1-4Sensitivity of Watermelon Cultigens to Ambient Ozone in North CarolinaGerald J. Holmes and Jonathan R. Schultheis23 February 2007 | Plant Disease, Vol. 87, No. 4Ozone: A Novel Plant “Pathogen”Factors that affect leaf extracellular ascorbic acid content and redox status20 December 2002 | Physiologia Plantarum, Vol. 117, No. 1The impact of ozone on a salt marsh cordgrass (Spartina alterniflora)Environmental Pollution, Vol. 120, No. 3}, number={1}, journal={PLANT DISEASE}, author={Krupa, S and McGrath, MT and Andersen, CP and Booker, FL and Burkey, KO and Chappelka, AH and Chevone, BI and Pell, EJ and Zilinskas, BA}, year={2001}, month={Jan}, pages={4–12} }
 @article{burkey_wei_eason_ghosh_fenner_2000, title={Antioxidant metabolite levels in ozone-sensitive and tolerant genotypes of snap bean}, volume={110}, ISSN={["0031-9317"]}, DOI={10.1034/j.1399-3054.2000.110208.x}, abstractNote={Ozone-sensitive and tolerant genotypes of snap bean (Phaseolus vulgaris L.) were compared for differences in leaf ascorbic acid (vitamin C), glutathione and α-tocopherol (vitamin E) content to determine whether antioxidant levels were related to ozone tolerance. Seven genotypes were grown in pots under field conditions during the months of June and July. Open top chambers were used to establish either a charcoal filtered (CF) air control (36 nmol mol−1 ozone) or a treatment where CF air was supplemented with ozone from 8:00 to 20:00 h with a daily 12 h mean of 77 nmol mol−1. Fully expanded leaves were analyzed for ascorbic acid, chlorophyll, glutathione, guaiacol peroxidase (EC 1.11.1.7) and α-tocopherol. Leaf ascorbic acid was the only variable identified as a potential factor in ozone tolerance. Tolerant genotypes contained more ascorbic acid than sensitive lines, but the differences were not always statistically significant. Genetic differences in glutathione and α-tocopherol were also observed, but no relationship with ozone tolerance was found. Guaiacol peroxidase activity and leaf α-tocopherol content increased in all genotypes following a one week ozone exposure, indicative of a general ozone stress response. Ozone had little effect on the other variables tested. Overall, ozone sensitive and tolerant plants were not clearly distinguished by differences in leaf antioxidant content. The evidence suggests that screening for ozone tolerance based on antioxidant content is not a reliable approach.}, number={2}, journal={PHYSIOLOGIA PLANTARUM}, author={Burkey, KO and Wei, CM and Eason, G and Ghosh, P and Fenner, GP}, year={2000}, month={Oct}, pages={195–200} }
 @article{reid_fiscus_burkey_1999, title={Effects of chronic ozone and elevated atmospheric CO2 concentrations on ribulose-1,5-bisphosphate in soybean (Glycine max)}, volume={106}, ISSN={["1399-3054"]}, DOI={10.1034/j.1399-3054.1999.106404.x}, abstractNote={Ribulose-1,5-bisphosphate (RuBP) pool size was determined at regular intervals during the growing season to understand the effects of tropospheric ozone concentrations, elevated atmospheric carbon dioxide concentrations and their interactions on the photosynthetic limitation by RuBP regeneration. Soybean (Glycine max [L.] Merr. cv. Essex) was grown from seed to maturity in open-top field chambers in charcoal-filtered air (CF) either without (22 nmol O3 mol−1) or with added O3 (83 nmol mol−1) at ambient (AA, 369 μmol CO2 mol−1) or elevated CO2 (710 μmol mol−1). The RuBP pool size generally declined with plant age in all treatments when expressed on a unit leaf area and in all treatments but CF-AA when expressed per unit ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39) binding site. Although O3 in ambient CO2 generally reduced the RuBP pool per unit leaf area, it did not change the RuBP pool per unit Rubisco binding site. Elevated CO2, in CF or O3-fumigated air, generally had no significant effect on RuBP pool size, thus mitigating the negative O3 effect. The RuBP pools were below 2 mol mol−1 binding site in all treatments for most of the season, indicating limiting RuBP regeneration capacity. These low RuBP pools resulted in increased RuBP regeneration via faster RuBP turnover, but only in CF air and during vegetative and flowering stages at elevated CO2. Also, the low RuBP pool sizes did not always reflect RuBP consumption rates or the RuBP regeneration limitation relative to potential carboxylation (%RuBP). Rather, %RuBP increased linearly with decrease in the RuBP pool turnover time. These data suggest that amelioration of damage from O3 by elevated atmospheric CO2 to the RuBP regeneration may be in response to changes in the Rubisco carboxylation.}, number={4}, journal={PHYSIOLOGIA PLANTARUM}, author={Reid, CD and Fiscus, EL and Burkey, KO}, year={1999}, month={Aug}, pages={378–385} }
 @article{burkey_1999, title={Effects of ozone on apoplast/cytoplasm partitioning of ascorbic acid in snap bean}, volume={107}, ISSN={["0031-9317"]}, DOI={10.1034/j.1399-3054.1999.100206.x}, abstractNote={Apoplast/cytoplasm partitioning of ascorbic acid (AA) was examined in four genotypes of snap bean (Phaseolus vulgaris L.) known to differ in ozone sensitivity. Plants were grown in pots under field conditions using open-top chambers to establish charcoal-filtered (CF) air (36 nmol mol−1 ozone) or elevated ozone (77 nmol mol−1 ozone) treatments. AA in fully expanded leaves of 36-day-old plants was separated into apoplast and cytoplasm fractions by vacuum infiltration methods using glucose 6-phosphate as a marker for cytoplasm contamination. Apoplast ascorbate levels ranged from 30 to 150 nmol g−1 fresh weight. Ozone-sensitive genotypes partitioned 1–2% of total AA into the apoplast under CF conditions and up to 7% following a 7-day ozone exposure. In contrast, an ozone-tolerant genotype partitioned 3–4% of total leaf AA into the leaf apoplast in both CF and ozone-treated plants. The results suggest that genetic background and ozone stress are factors that affect AA levels in the extracellular space. For all genotypes, the fraction of AA in the oxidized form was higher in the apoplast compared to the cytoplasm, indicative of a more oxidizing environment within the cell wall.}, number={2}, journal={PHYSIOLOGIA PLANTARUM}, author={Burkey, KO}, year={1999}, month={Oct}, pages={188–193} }
 @article{reid_fiscus_burkey_1998, title={Combined effects of chronic ozone and elevated CO2 on Rubisco activity and leaf components in soybean (Glycine max)}, volume={49}, ISSN={["1460-2431"]}, DOI={10.1093/jexbot/49.329.1999}, number={329}, journal={JOURNAL OF EXPERIMENTAL BOTANY}, author={Reid, CD and Fiscus, EL and Burkey, KO}, year={1998}, month={Dec}, pages={1999–2011} }
 @article{burkey_mathis_1998, title={Identification of a novel isoform of the chloroplast-coupling factor alpha-subunit}, volume={116}, ISSN={["0032-0889"]}, DOI={10.1104/pp.116.2.703}, abstractNote={Abstract Studies were conducted to identify a 64-kD thylakoid membrane protein of unknown function. The protein was extracted from chloroplast thylakoids under low ionic strength conditions and purified to homogeneity by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Four peptides generated from the proteolytic cleavage of the wheat 64-kD protein were sequenced and found to be identical to internal sequences of the chloroplast-coupling factor (CF1) α-subunit. Antibodies for the 64-kD protein also recognized the α-subunit of CF1. Both the 64-kD protein and the 61-kD CF1α-subunit were present in the monocots barley (Hordeum vulgare), maize (Zea mays), oat (Avena sativa), and wheat (Triticum aestivum); but the dicots pea (Pisum sativum), soybean (Glycinemax Merr.), and spinach (Spinacia oleracea) contained only a single polypeptide corresponding to the CF1 α-subunit. The 64-kD protein accumulated in response to high irradiance (1000 μmol photons m−2 s−1) and declined in response to low irradiance (80 μmol photons m−2 s−1) treatments. Thus, the 64-kD protein was identified as an irradiance-dependent isoform of the CF1 α-subunit found only in monocots. Analysis of purified CF1 complexes showed that the 64-kD protein represented up to 15% of the total CF1 α-subunit.}, number={2}, journal={PLANT PHYSIOLOGY}, author={Burkey, KO and Mathis, JN}, year={1998}, month={Feb}, pages={703–708} }
 @article{burkey_wilson_wells_1997, title={Effects of canopy shade on the lipid composition of soybean leaves}, volume={101}, DOI={10.1034/j.1399-3054.1997.1010320.x}, number={3}, journal={Physiologia Plantarum}, author={Burkey, K. O. and Wilson, R. F. and Wells, R.}, year={1997}, pages={591–598} }
 @article{burkey_wells_1996, title={Effects of natural shade on soybean thylakoid membrane composition}, volume={50}, ISSN={["0166-8595"]}, DOI={10.1007/BF00014885}, number={2}, journal={PHOTOSYNTHESIS RESEARCH}, author={Burkey, KO and Wells, R}, year={1996}, month={Nov}, pages={149–158} }
 @article{burkey_gizlice_carter_1996, title={Genetic variation in soybean photosynthetic electron transport capacity is related to plastocyanin concentration in the chloroplast}, volume={49}, ISSN={["0166-8595"]}, DOI={10.1007/BF00117664}, number={2}, journal={PHOTOSYNTHESIS RESEARCH}, author={Burkey, KO and Gizlice, Z and Carter, TE}, year={1996}, month={Aug}, pages={141–149} }
 @article{burkey_1994, title={GENETIC-VARIATION OF PHOTOSYNTHETIC ELECTRON-TRANSPORT IN BARLEY - IDENTIFICATION OF PLASTOCYANIN AS A POTENTIAL LIMITING FACTOR}, volume={97}, ISSN={["0168-9452"]}, DOI={10.1016/0168-9452(94)90055-8}, abstractNote={Cultivated (Hordeum vulgare) and wild (Hordeum spontaneum) genotypes of barley were compared for differences in photosynthetic electron transport activity and chloroplast membrane composition. Plants were grown at 21°C in a controlled environment chamber (500 μmol photons m−2s−1). Thylakoid membranes were isolated from vegetative and flag leaves and analyzed for uncoupled electron transport activity. Significant genetic variability in chloroplast electron transport was found with fourfold differences in activity observed in the genotypes tested. Quantitative measurements were made for each component of the chloroplast electron transport chain, including the development of an immunochemical assay for plastocyanin. The genetic differences in electron transport activity were related to the concentration of plastocyanin in the thylakoid membrane. The fivefold differences in plastocyanin content observed within the genotypes tested corresponded to a plastocyanin pool size of 0.8–3.8 mol of plastocyanin per mol of photosystem I reaction center. Therefore, plastocyanin was a significant limiting factor in barley genotypes expressing low photosynthetic electron transport activity.}, number={2}, journal={PLANT SCIENCE}, author={BURKEY, KO}, year={1994}, pages={177–187} }
 @article{burkey_1993, title={EFFECT OF GROWTH IRRADIANCE ON PLASTOCYANIN LEVELS IN BARLEY}, volume={36}, ISSN={["0166-8595"]}, DOI={10.1007/BF00016275}, number={2}, journal={PHOTOSYNTHESIS RESEARCH}, author={BURKEY, KO}, year={1993}, month={May}, pages={103–110} }
 @article{burkey_1992, title={NOVEL LIGHT-REGULATED CHLOROPLAST THYLAKOID MEMBRANE-PROTEIN}, volume={98}, ISSN={["0032-0889"]}, DOI={10.1104/pp.98.3.1211}, abstractNote={A 64 kilodalton chloroplast membrane polypeptide was dependent on growth irradiance with 10-fold greater quantities of the protein present in barley (Hordeum vulgare) grown under 500 micromoles of photons per square meter per second compared with growth at 50 micromoles per square meter per second. The concentration of the protein was sensitive to changes in irradiance, with a slow time course for the response (days) similar to other reported light acclimation processes. The polypeptide also was observed in maize (Zea mays), oats (Avena sativa), and wheat (Triticum aestivum), but not in soybean (Glycine max Merr). The 64 kilodalton polypeptide did not correspond to any thylakoid membrane protein with an assigned function, so its structural or regulatory role is not known.}, number={3}, journal={PLANT PHYSIOLOGY}, author={BURKEY, KO}, year={1992}, month={Mar}, pages={1211–1213} }
 @article{burkey_wells_1991, title={RESPONSE OF SOYBEAN PHOTOSYNTHESIS AND CHLOROPLAST MEMBRANE-FUNCTION TO CANOPY DEVELOPMENT AND MUTUAL SHADING}, volume={97}, ISSN={["0032-0889"]}, DOI={10.1104/pp.97.1.245}, abstractNote={The effect of natural shading on photosynthetic capacity and chloroplast thylakoid membrane function was examined in soybean (Glycine max. cv Young) under field conditions using a randomized complete block design. Seedlings were thinned to 15 plants per square meter at 20 days after planting. Leaves destined to function in the shaded regions of the canopy were tagged during early expansion at 40 days after planting. To investigate the response of shaded leaves to an increase in available light, plants were removed from certain plots at 29 or 37 days after tagging to reduce the population from 15 to three plants per square meter and alter the irradiance and spectral quality of light. During the transition from a sun to a shade environment, maximum photosynthesis and chloroplast electron transport of control leaves decreased by two- to threefold over a period of 40 days followed by rapid senescence and abscission. Senescence and abscission of tagged leaves were delayed by more than 4 weeks in plots where plant populations were reduced to three plants per square meter. Maximum photosynthesis and chloroplast electron transport activity were stabilized or elevated in response to increased light when plant populations were reduced from 15 to three plants per square meter. Several chloroplast thylakoid membrane components were affected by light environment. Cytochrome f and coupling factor protein decreased by 40% and 80%, respectively, as control leaves became shaded and then increased when shaded leaves acclimated to high light. The concentrations of photosystem I (PSI) and photosystem II (PSII) reaction centers were not affected by light environment or leaf age in field grown plants, resulting in a constant PSII/PSI ratio of 1.6 +/- 0.3. Analysis of the chlorophyll-protein composition revealed a shift in chlorophyll from PSI to PSII as leaves became shaded and a reversal of this process when shaded leaves were provided with increased light. These results were in contrast to those of soybeans grown in a growth chamber where the PSII/PSI ratio as well as cytochrome f and coupling factor protein levels were dependent on growth irradiance. To summarize, light environment regulated both the photosynthetic characteristics and the timing of senescence in soybean leaves grown under field conditions.}, number={1}, journal={PLANT PHYSIOLOGY}, author={BURKEY, KO and WELLS, R}, year={1991}, month={Sep}, pages={245–252} }