NIMSS: View = Report

SAES-422 Multistate Research Activity Accomplishments Report =

Approved =

Project No. and Title:	NE10= 30=20 Characterization and Mechanisms of Plant Responses to Ozone in the = U.S.=20
Period Covered:	10-2007 to 09-2008
Date of Report:	30-Sep-2008
Annual Meeting Dates:	15-May-2008 to 16-May-2008

Participants

Best, Teodora Best (txo115@psu.edu) - Pennsylvania State = University=20
Booker, Fitzgerald (fitz.booker@ars.usda.gov) - USDA-ARS, Raleigh, = NC=20
Chappelka, Art (chappah@auburn.edu) - Auburn University=20
Grantz, David (david@uckac.edu) - University of California - = Riverside=20
Manning, William (wmanning@microbio.umass.edu) - University of=20 Massachusetts=20
Matyssek, Rainer (matyssek@wzw.tum.de) - Technical University of = Munich=20
McGrath, Margaret (mtm3@cornell.edu) - Cornell University=20
Muntifering, Russell (rmuntife@acesag.auburn.edu) - Auburn = University=20
Neufeld, Howard (neufeldhs@appstate.) - Appalachian State = University=20
Ren, Wei renwei1@auburn.edu) - Auburn University=20
Sandermann, Heinrich (heinrich.sandermann@ctp.uni-freiburg.de) - = Ecotox=20
Wiese, Cosima cwiese@misericordia.edu)- College Misericordia=20
Zilinskas, Barbara (zilinskas@aesop.rutgers.edu) - Rutgers = University=20

Brief Summary of Minutes of Annual Meeting

The = Annual=20 Meeting of the Technical Committee was held at Auburn University, May = 15-16,=20 2008.=20

The meeting was hosted by Art Chappelka and Russell Muntifering of = Auburn=20 University and coordinated by outgoing Chair, Fitzgerald Booker of = USDA/ARS in=20 Raleigh NC.=20

Dr. Margaret Smith, Associate Director, Cornell Univ. Agricultural = Experiment=20 Station (attending on Mike Hoffmann's behalf) planned on attending the = meeting=20 but conflicts with travel arrangements prevented it.=20

Several members of the NE-1030 Technical Committee, along with Ray = Knighton=20 were unable to attend due to participation in the USDA-ARS Global Change = program=20 and Air Quality Task Force meetings.=20

Station reports were presented by project objective. Guest = presentations were=20 made at the conclusion of the station reports:=20

Rainer Matyssek - Spatio-Temporal Scaling of Ozone Uptake and = Effective Dose=20 in Forest Trees: Current Status and Perspectives;=20

Heinrich Sandermann - Bioactivation of Extracellular Ascorbate by = Ozone.=20

Business Meeting=20

1. At the conclusion of the technical meeting, a business meeting was = held.=20 The Committee expressed satisfaction with the term of outgoing Chair, = Fitz=20 Booker who oversaw two excellent meetings and the completion of the = Final Report=20 for the NE-1013 Project.=20

2. NE-1030 Annual Reports for the period October 1, 2007 =13 = September 30, 2008=20 should be sent to D. Grantz.=20

3. Snap bean project status was discussed. Committee members involved = in this=20 project have finalized the experimental protocol and now have a few = years of=20 data from several locations. It is anticipated that there will soon be = enough=20 data for the modeling work.=20

4. Art Chappelka was nominated and elected Chair-elect (2010-2012). = During=20 this term the current project will terminate and a new proposal will = need to be=20 written. Meg McGrath agreed to continue serving as Secretary.=20

5. It was decided that the 2009 meeting of NE-1030 will be Riverside, = CA,=20 hosted by Nancy Grulke (US Forest Service, Riverside, CA) and = coordinated by=20 Chair, David Grantz of the University of California at Riverside. = Meetings will=20 continue to be rotated between the western, southern and northeastern = regions of=20 the US. Dennis Decoteau (Penn State University, State College, PA) = offered to=20 host a meeting, and it was selected for the meeting in 2010.=20

6. Rainer Matyssek and Teodora Best expressed an interest in becoming = members=20 of the NE-1030 project. The necessary steps are in process through the=20 Administrative Advisor, Dr. Mike Hoffmann.=20

7. A number of other projects in the gestational stage, or with = preliminary=20 data not ready for public presentation, were discussed informally. The = NE-1030=20 technical committee represents a large fraction of the ongoing research = on the=20 effects of ozone on vegetation. A few key projects have had a low = profile in=20 this group, which should be rectified if possible.=20

8. The NE-1013 website has been updated and revised for the NE-1030 = project=20 although the URL remains unchanged = (http://www.ncsu.edu/project/usda-ne-1013/).=20 Searches for NE-1030 are re-directed to this URL.=20

9. Chair Elect David Grantz assumed the Chair of the NE-1030 = committee for=20 the next two years (2008-2010).=20

Meeting adjourned at 11:30 a.m. on May 16, 2008.=20

Respectively submitted, Meg McGrath, Secretary August 4, 2008=20

Accomplishments

Objective 1. Describe the = spatial -=20 temporal characteristics of the adverse effects of current ambient O3 = levels on=20 crop productivity, including the development of numerical models to = establish=20 cause =13 effect relationships that apportion the ozone contribution.=20

(MA) A MS thesis project was conducted by Jennifer Albertine on soil = warming,=20 seedling emergence, and ozone injury. Beans grown in the warm soil (25 = C)=20 germinated faster, developed leaves faster, and had visible ozone injury = 2 days=20 earlier than plants grown at 20 C. Exposure to elevated ozone resulted = in=20 reduced leaf area and reduced stem length. Height was not affected by = O3. (Bill=20 Manning, University of Massachusetts).=20

(NY) Plant response to ambient ozone on Long Island, NY, was examined = in 2007=20 by growing ozone-sensitive and ozone-tolerant snap bean lines (S156 and = R331) as=20 done since 2004. There were three successive field plantings of beans to = be able=20 to assess the impact of ambient ozone occurring throughout the growing = season=20 (14 May, 12 June, and 11 July 2007). As they developed, bean pods were = harvested=20 repeatedly from some plants when immature and at a size typical for = fresh-market=20 consumption. Pods were harvested from the other plants when mature and = dry. S156=20 yielded less than the tolerant line R331 when grown under ambient ozone=20 conditions on Long Island in 2007. Total weight and number of bean pods=20 harvested for fresh-market consumption from planting 1 (14 May) plants = was 23%=20 and 11% lower, respectively, for S156 compared to R331 (pods were = harvested from=20 9 July through 30 July). There was a 30% and 18% reduction in these = yield=20 variables, respectively, for planting 2 (12 June) plants (30 July = through 5=20 Sept). Reduction was 29% and 10%, respectively, for planting 3 (11 July) = plants=20 (29 Aug through 3 Oct). These differences were not always significant. = Mature=20 yield was also reduced for S156 compared to R331. For plants in planting = 1,=20 number of pods produced by S156 was reduced 10% compared to R331, number = of=20 seeds was reduced 22% and average seed weight was reduced 20%. There was = a 17%,=20 24%, and 32% reduction in these yield variables, respectively, for = planting 2=20 plants; and a 30%, 38%, and 28% reduction in these yield variables,=20 respectively, for planting 3 plants. From emergence until the last = fresh-market=20 pod harvest, plants in the three plantings were exposed to O3 that was = at least=20 40 ppb for 627, 791, and 605 hours, respectively. During these growth = periods of=20 63, 79, and 78 days, O3 exposure expressed as AOT40 was 7,643 ppb.h, = 10,451=20 ppb.h, and 6,827 ppb.h, respectively. These values greatly exceed the = long-term=20 critical level of ozone exposure for crops of 3000 ppb.h accumulated = over three=20 months. (Meg McGrath, Cornell University).=20

Objective 2. Assess the effects of O3 on structure, function and=20 inter-species competition in managed and native plant populations, = including=20 alterations in their nutrient quality.=20

(AL) O3 effects on forage quality were examined. We completed the = fourth year=20 of a 7-year (2004=132010) experiment to determine effects of co-exposure = to a=20 range of current and projected levels of O3 and atmospheric N on = productivity=20 and nutritive quality of an extensively managed, species-rich (primarily = Festuca, Nardus and Carex, numerous forb and few legume spp.) pasture = located at=20 Alp Flix, Switzerland. One hundred eighty plots (40 =C3=97 30 cm) = representative of=20 vegetation at the site were exposed during the April=13October growing = seasons in=20 2004=132007 to one of three levels of O3 (ambient, ambient + 20 ppb O3, = or ambient=20 + 40 ppb O3, corresponding to 1.0, 1.2 or 1.6 =C3=97 ambient O3, = respectively) in a=20 free-air fumigation system that comprised 9 exposure rings (3 rings/O3 = level).=20 Within each ring, 20 plots received biweekly applications of NH4NO3 = solution=20 that simulated five areal concentrations of atmospheric N deposition = equivalent=20 to 0, 5, 10, 25 or 50 kg/ha (4 plots/N concentration). Plots were = harvested once=20 each year in August by cutting forage at 2 cm above ground surface. = Differences=20 (P < 0.0001) were observed among years in forage concentrations of N = and=20 cell-wall constituents, and in relative nutritive quality calculated = from forage=20 concentrations of the latter. Across all four growing seasons and levels = of N=20 input, there was no systematic effect of O3 exposure level on grassland=20 nutritive quality. However, there was an O3 =C3=97 N interaction (P =3D = 0.09) such that=20 positive responses in forage quality to N inputs of 25 and 50 kg/ha were = ablated=20 by increased deposition, and lignification of cell-wall constituents = associated=20 with accelerated foliar senescence in the elevated-O3 treatments. = Results=20 indicate that excessive rates of N deposition may increase plant = sensitivity to=20 elevated O3, and further compound the phytotoxic effects of O3 on forage = quality.=20

In a second project just started, diet selection and nutrient = utilization are=20 being examined for a model herbivore (rabbit) receiving ozone-exposed = forage.=20 Clover, the current preferred forage over grass, is more sensitive to = ozone,=20 resulting in lower nutrient quality, which could lead to changes in = feeding=20 preference. (Russell Muntifering, Auburn University).=20

(AL) provided an overview of a project on ozone impacts on native = trees and=20 wildflowers in the Great Smoky Mountains National Park that he is = conducting=20 with other NE1030 participants. This, the most visited park in the US, = is=20 considered a Class 1 Wilderness area, thus project findings can have = policy=20 implications. Results also were presented on a study investigating the = effects=20 of concurrent elevated carbon dioxide and ozone on leaf gas exchange=20 characteristics. When European beech grown under ambient ozone and = carbon=20 dioxide was exposed to elevated ozone for 1 hr (55 or 95 ppb), stomatal = control=20 was reduced resulting in increased water loss. Ozone reduced = transpiration at=20 low but not elevated carbon dioxide. (Art Chappelka, Auburn University)=20

(CA) O3 effects on stomatal behavior in tree species were described. = Using a=20 newly modified steady state gas exchange system it was shown that ozone = exposure=20 reduced the rate of stomatal response, and attenuated the typical = closing=20 responses in woody species. This led to increased long term average = stomatal=20 conductance and thus ozone flux, as well as degraded plant water = relations.=20 (Nancy Grulke; U.S. Forest Service, Riverside CA)=20

(CA) Interactions between herbicide resistance and O3, comets, Grantz = (CA)=20 presented results on attempts to alter plant response to ozone by = applying=20 methyl jasmonate (o or 160 micrograms per plant applied in small = droplets to=20 youngest fully expanded leaves). These exogenous applications led to = foliar=20 symptoms that were similar to ozone symptoms. Jasmonate reduced growth = and=20 altered root to shoot ratios similarly to ozone. However, there was no=20 interaction between jasmonate and ozone, except in the case of root = respiration.=20 In this case ozone had little effect on respiration in the absence of = jasmonate,=20 but in its presence ozone had a substantial inhibitory effect. Effects = were=20 generally additive.=20

Horseweed is an increasingly important weed in CA partly because it = has=20 developed resistance to the herbicide glyphosate. It is newly invasive, = though=20 it is a native species to North America. Building on results presented = in=20 previous years, it was shown that ozone allows glyphosate-sensitive = genotypes to=20 escape the impact of the herbicide, potentially accelerating the = fixation of=20 alleles for glyphosate resistance in ozone impacted airbasins. (David = Grantz,=20 University of California =13 Riverside)=20

Objective 3. Examine the joint effects of O3 with other growth = regulating=20 factors (e.g., CO2, temperature) that are expected to vary with ongoing = climate=20 change on crop growth and productivity.=20

(NC) The relative sensitivity to ozone of some tree species in the = Great=20 Smoky Mountains was evaluated. Black cherry, winged sumac, sycamore, and = tulip=20 popular were among the most sensitive. A graduate student is = investigating=20 impacts on lichens of long-term exposure to elevated carbon dioxide and = ozone at=20 the Rhinelander FACE site. Identification of individual lichens remains=20 challenging. (Howard Neufeld, Appalachian State University)=20

Objective 4. Examine the physiological and molecular basis of O3 = toxicity and=20 tolerance in plants.=20

(NC) Isoprene emissions and O3: no interactions detected so far. The=20 biogenically-produced volatile hydrocarbon, isoprene, may be influential = in=20 protecting some plants from ozone injury. Isoprene emission is = correlated with=20 tolerance to high temperature and oxidative stress. Isoprene can also = scavenge=20 ozone in the leaf boundary layer and apoplast, although reaction = products may be=20 toxic and overall efficacy of the proposed mechanism is uncertain. A = series of=20 experiments conducted in Raleigh, NC investigated potential interactions = between=20 biogenically-synthesized isoprene and ozone. It was found that isoprene=20 biosynthesis in transgenic Arabidopsis had no influence on visible = injury,=20 decreased rosette diameter and lower biomass accumulation caused by 100 = ppb of=20 ozone for 21 days. Velvet bean (Mucuna pruriens) lines that displayed = varying=20 extents of foliar visible injury symptoms following acute ozone = exposures were=20 found to emit isoprene at similar rates when grown in clean air. = Isoprene is=20 synthesized in the chloroplast, so it was not unexpected that emission = rates=20 from velvet bean leaves declined with net photosynthesis following = treatment=20 with 70 ppb ozone for eight days. Inhibition of isoprene synthesis by=20 fosmidomycin in hydroponically-grown velvet bean had no effect on = suppression of=20 net photosynthesis by 125 ppb ozone for eight days. There was no = significant=20 effect of fosmidomycin on photosynthesis rates in control plants. These = results=20 raise significant questions about the proposed role of isoprene in = modifying=20 ozone injury in isoprene-emitting plants. (Fitz Booker, USDA-ARS, = Raleigh, NC).=20

(PA) Results were presented to identify molecular and physiological=20 mechanisms that confer enhanced tolerance to ozone stress in trees using = black=20 cherry and hybrid poplar. It is hypothesized that a network of genes = exists=20 whose expression confers resistance to ozone stress. A gene (OZO) was = found that=20 is highly expressed under high ozone. (Teodora Best, Pennsylvania State=20 University).=20

(PA) Phenolic antioxidant characterization in snap bean lines. The = goal of=20 this project, conducted in collaboration with Dr. Kent Burkey in the = Plant=20 Science Unit at USDA-ARS in Raleigh, NC, is to determine the role of the = apoplast in plant defense responses to oxidative stress. To examine = this,=20 apoplastic wash fluid was extracted from three snap bean (Phaseolus = vulgaris)=20 cultivars (Provider, R123, S156), which differ in their sensitivity to = O3, and=20 analyzed using High Performance Liquid Chromatography (HPLC). Initial=20 experiments primarily showed quantitative differences in apoplastic = constituents=20 at different leaf ages within one cultivar, indicating that the quantity = of the=20 chemical compounds changes as the leaves develop. Additional experiments = were=20 conducted during the summer of 2007, in which the R123 and S156 snap = bean=20 cultivars were exposed to O3 for 6 days and the first fully expanded = leaf third=20 was harvested at the end of the experiment. Initial analysis by HPLC did = not=20 show any significant effects of treatment or cultivar on the HPLC = profiles of=20 the apoplastic wash fluid. Currently, the HPLC separation procedure is = being=20 modified to optimize the separation of the unknown compounds in the = samples.=20 Additional experiments are planned to investigate the antioxidant = activity of=20 the insoluble cell wall fraction, and to determine whether changes in = the=20 apoplastic fluid occur sooner than six days into plant exposure to O3. = (Cosima=20 Wiese, College Misericordia).=20

(NJ) The snap bean experiment in New Jersey resulted in final yield = (both dry=20 bean weight and seed weight) was 48-50% lower in the sensitive line = compared to=20 the tolerant line. The role of glutathione perosidase in the response of = Arabidopsis thaliana to ozone was also examined. The hypothesis that = GPX3=20 (glutathione peroxidase 3) is involved in the signal transduction = pathway in=20 response to ozone is being tested systematically. (Barbara Zilinskas, = Rutgers=20 University).=20

(NC) Open-top chamber yield studies were completed for selected = soybean=20 ancestors exposed to season long treatments of either CF air (~25 ppb = 12-hour=20 seasonal mean) or CF+O3 (~75 ppb seasonal 12-hour mean). Analysis of = three years=20 of data is underway. (Kent Burkey, USDA-ARS, Raleigh).=20

(Germany) The Free-Air ozone experiment at the Kranzberg Forest Site = was=20 described. Data are being evalulated to contribute to the use of site = specific=20 fluxes of ozone as a predictor of phytotoxicity and as a regulatory = measure. It=20 is widely agreed in Europe that mechanistically-based O3 risk assessment = of=20 trees and forests needs to be related to two components: (1) stomatal = whole-tree=20 O3 uptake and (2) effective O3 dose (i.e. responsiveness per unit of O3 = uptake).=20 The presentation highlighted current methodologies and perspectives = towards=20 spatio-temporal scaling of both components, exemplifying the combination = of the=20 sapflow and eddy covariance approaches in relation to (1), which = provides a=20 phytomedically relevant whole-tree and stand-level O3 dose while = allowing to=20 empirically derive the non-stomatal O3 flux (with perspectives towards = the=20 landscape level). Stable isotope analysis was suggested, as one option, = in view=20 of (2), providing a mechanistically based, long-term integration of = metabolic O3=20 responsiveness and its temporal variation. Strategies were introduced = towards=20 proxies, which may be suitable for developing new risk modelling tools. = The=20 combination of whole-tree sap flow, stand-level eddy covariance, and=20 experimental free-air O3 release methodologies was acknowledged as a = promising=20 strategy, in view of (1) and (2), of promoting cause/effect-based O3 = risk=20 assessment. (R. Matyssek, Freiburg)=20

(Germany)=13Potential pro-oxidant reactions of ascorbic acid in = response to O3=20 were evaluated from a theoretical chemistry perspective. The results, = involving=20 inadequate kinetics and contents, as well as previously undescribed = toxic=20 byproducts, make it somewhat problematic for ascorbic acid to perform = the=20 primary ozone defensive role that it has been commonly assumed to = perform.=20 Extracellular ascorbate is considered to be the first line of defense = against=20 ozone. Experimental evidence for this includes the Arabidopsis mutant = vtc1, with=20 only 30 % of normal total ascorbate, is ozone-sensitive. Ascorbate = decomposes=20 ozone at an extremely high rate. However, only a single and toxic = decomposition=20 product has been identified (singlet oxygen). Ozone might act mainly = through=20 secondary toxicants such as singlet oxygen or peroxy-compounds, some of = which=20 may be produced by reactions between ascorbate and ozone. Protection = against=20 ozone requires not only quenching of ozone but also scavenging of = secondary=20 toxicants. Ozone might still act directly, e.g. by attack on a sensitive = =13SH=20 group of some receptor protein. In view of multiple candidate mechanisms = for=20 protection or sensitivity, it is too early to define a simple ozone=20 responsiveness parameter to be combined with an ozone flux parameter. = (H.=20 Sandermann Ecotox, Freiburg, Germany).=20

EDU may protect plants from ozone injury by acting as an antioxidant. = EDU has=20 some similarities with chemicals used in rubber products to protect them = from=20 oxidation by ambient ozone and UV radiation. A new field of study is = proposed=20 that examines applications of this technology to plants and may be = called "tire=20 biology." (H. Sandermann Ecotox, Freiburg, Germany).=20

Impacts

Regulatory focus and attention of Agricultural Air Quality Task = Force is=20 directed to ongoing impacts of ambient ozone on vegetation. (27% = reduction of=20 fresh bean yield in the field in rural Long Island, NY, 49% reduction = of dry=20 bean yield in rural New Jersey, visible damage to native species in = Class I=20 Wilderness Areas in Great Smoky Mountains National Park, demonstrate = ongoing=20 welfare effects of ozone air pollution).=20
Tropospheric ozone is recognized as an important element of global = change--ozone is a constituent of the changing atmosphere, has = greenhouse gas=20 potential, and interacts with other elements of global change. (warmer = soil=20 accelerated ozone damage to beans, nitrogen deposition increased ozone = sensitivity of forage nutritive quality, ozone increased tree water = loss which=20 may alter stream flows and water supplies).=20
Growers in California are adopting new control measures for the = native=20 weed, horseweed which is acting like an invasive species. (ozone = appears to=20 accelerate the spread of a more competitive and herbicide resistant = horseweed=20 biotype).=20
Regulatory standards for ozone are being developed that are more=20 vegetation-protective without simply requiring lower overall = concentrations.=20 (a combination of single plant water use and canopy flux measurements=20 predicted effective ozone dose in trees, a key regulatory parameter = that may=20 be adopted in the future).=20
Public educational facilities are in operation in California and=20 Pennsylvania to provide locally relevant information on ozone air = pollution,=20 its causes and effects, and feasible mitigation strategies.

Publications

Ainsworth EA. 2008. Rice = production in a=20 changing climate: A meta-analysis of responses to elevated carbon = dioxide and=20 elevated ozone concentration. Global Change Biology, 14: 1642-1650.=20

Ainsworth EA, Rogers A, Leakey ADB. 2008. Targets for crop = biotechnology in a=20 future high-CO2 and high-O3 world. Plant Physiology, 147: 13-19.=20

Bergweiler, C, WJ Manning and BI Chevone. 2008. Seasonal and diurnal = gas=20 exchange differences in ozone-sensitive common milkweed (Asclepias = syriaca L.)=20 in relation to ozone uptake. Environmental Pollution 152:403-415.=20

Bergweiler, C, H Carreras, E Wannaz, J Rodriguez, B Toselli, L Olcese = and ML=20 Pignata. 2008. Field surveys for potential ozone bioindicator plant = species in=20 Argentina. Environmental Monitoring and Assessment 138:305-312.=20

Booker, FL, R Muntifering, M McGrath, KO Burkey, D Decoteau, EL = Fiscus, W=20 Manning, S Krupa, A Chappelka, DA Grantz. 2008. The ozone component of = global=20 change: Potential effects on agricultural and horticultural plant yield, = product=20 quality and interactions with invasive species. Journal of Integrative = Plant=20 Biology: In press.=20

Feng, Z, K Kobayashi, EA Ainsworth. 2008. Impact of elevated ozone=20 concentration on growth, physiology, and yield of wheat (Triticum = aestivum L.):=20 a meta-analysis. Global Change Biology: In press.=20

E.A.Grantz, DA, A Shrestha and H-B Vu. 2008. Early vigor and ozone = response=20 in horseweed (Conyza canadensis) biotypes differing in glyphosate = resistance.=20 Weed Science 56:224-230.=20

Grantz, DA, A Shrestha and H-B Vu. 2008. Ozone enhances adaptive = benefit of=20 glyphosate resistance in horseweed (Conyza canadensis). Weed Science = 56:549-554.=20

Handley T, Grulke NE. 2008. Interactive effects of O3 exposure on = California=20 black oak (Quercus kelloggii Newb.) seedlings with and without nitrogen=20 amendment. Environmental Pollution = xx:1-8.doi:10.1016/j.envpol.2008.01.002.=20

Kline LJ, Davis DD, Skelly JM, Savage JE, Ferdinand J. 2008. Ozone=20 sensitivity of 28 plant selections exposed to ozone under controlled = conditions.=20 Northeastern Naturalist 15:57=1366=20

Krupa, S, FL Booker, V Bowersox, C Lehmann and D Grantz. 2008. = Uncertainties=20 in the current knowledge of some atmospheric trace gases associated with = US=20 agriculture. Journal of Air & Waste Management Association = 58:986-993.=20

Matyssek, RH Sandermann, G Wieser, FL Booker, S Cieslik, R Musselman = and D=20 Ernst. 2008. The challenge of making ozone risk assessment for forest = trees more=20 mechanistic. Environmental Pollution:In press.=20

Novak, K, M Schaub, J Fuhrer, JM Skelly, B Frey and N Kr=C3=A4uchi. = 2008. Ozone=20 effects on visible foliar injury and growth of Fagus sylvatica and = Viburnum=20 lantana seedlings grown in monoculture or in mixture. Environmental and=20 Experimental Botany, Volume 62, 212-220=20

Orendovici-Best, T, JM Skelly, DD Davis, JA Ferdinand, JE Savage and = RE=20 Stevenson. 2008. Ozone uptake (flux) as it relates to ozone-induced = foliar=20 symptoms of Prunus serotina and Populus maximowizii =C3=97 trichocarpa. = Environmental=20 Pollution 151:79-92=20

Paoletti, E., N. Contran, W.J. Manning, A. Castagna, A. Ranieri, and = F.=20 Tagliaferro. 2008. Protection of ash (Fraxinus excelsior) trees from = ozone=20 injury by ethylenediurea (EDU): Roles of biochemical changes and = decreased=20 stomatal conductance in enhancement of growth. Environmental Pollution=20 155:464-472.=20

Percy, K and R Rittmaster. 2008. Clearing the Air on Forest = Productivity.=20 Impact Note No. 47, Natural Resources Canada, Canadian Forest = Service-Atlantic=20 Forestry Centre, Fredericton. (http://cfs.nrcan.gc.ca)=20

Pregitzer, KS, AJ Burton, JS King and DR Zak. 2008. Soil respiration, = root=20 biomass, and root turnover following long-term exposure of northern = forests to=20 elevated atmospheric CO2 and tropospheric O3. New Phytologist doi:=20 10.1111/j.1469-8137.2008.02564.x=20

Qiu, Q-S, JL Huber, FL Booker, V Jain, ADB Leakey, EL Fiscus, PM Yau, = DR Ort=20 and SC Huber. 2008. Increased protein carbonylation in leaves of = Arabidopsis and=20 soybean in response to elevated [CO2]. Photosynthesis Research = 97:155-166.=20

Reid, CD and EL Fiscus. 2008. Ozone and density affect the response = of=20 biomass and seed yield to elevated CO2 in rice. Global Change Biology. = 14:60-76.=20

Wang, X, Q Zheng, Z Feng, J Xie, Z Feng, Z Ouyang, and WJ Manning. = 2008.=20 Comparison of a diurnal vs. steady-state ozone exposure profile on = growth and=20 yield of oilseed rape (Brassica napus L.) in open-top chambers in the = Yangtze=20 Delta, China. Environmental Pollution In Press.=20

2007=20

Booker, FL, KO Burkey, WA Pursley and AS Heagle. 2007. Elevated = carbon=20 dioxide and ozone effects on peanut. I. Gas-exchange, biomass, and leaf=20 chemistry. Crop Science 47:1475-1487.=20

Burkey, KO, FL Booker, WA Pursley and AS Heagle. 2007. Elevated = carbon=20 dioxide and ozone effects on peanut. II. Seed yield and quality. Crop = Science=20 47:1488-1497.=20

Calfapietra, C, AE Wiberley, TG Falbel, AR Linskey, G = Scarascia-Mugnozza, DF=20 Karnosky, F Loreto, and TD Sharkey. 2007. Isoprene synthase expression = and=20 protein levels are reduced under elevated O3 but not under elevated CO2 = (FACE)=20 in field-grown aspen trees. Plant Cell Environment 30:654-661.=20

Chen, X, C Tu, M Burton, D Watson, KO Burkey and S Hu. 2007. Plant = nitrogen=20 acquisition and interactions under elevated CO2: impact of endophytes = and=20 mycorrhizae. Global Change Biology. 13: 1238-1249.=20

Cheng, FY, KO Burkey, JM Robinson and FL Booker. 2007. Leaf = extracellular=20 ascorbate in relation to O3 tolerance of two soybean cultivars. = Environmental=20 Pollution 150:355-362.=20

Dubois, J.-J.B., EL Fiscus, FL Booker, MD Flowers and CD Reid. 2007.=20 Optimizing the statistical estimation of the parameters of the = Farquhar-von=20 Caemmerer-Berry model of photosynthesis. New Phytologist 176:402-414.=20

Farber, R.J. et. al. (Grantz is 15th out of 19 randomly ordered = authors).=20 2007. Obliterating the dust in the Antelope Valley. Paper Number 384,=20 Proceedings, Annual Meeting and Proceedings, Air and Waste Management=20 Association.=20

Fiscus, EL, FL Booker, J-JB Dubois, TR Rufty, JW Burton and WA = Pursley. 2007.=20 CO2 enhancement effects in container- versus ground-grown soybeans at = equal=20 planting densities. Crop Science 47:2486-2494.=20

Flowers, MD, EL Fiscus, KO Burkey, FL Booker and J-J Dubois. 2007.=20 Photosynthesis, chlorophyll fluorescence, and yield of snap bean = (Phaseolus=20 vulgaris L.) genotypes differing in sensitivity to ozone. Environmental = and=20 Experimental Botany 61:190-198.=20

Grulke, NE, HS Neufeld, AW Davison, M Roberts, and AH Chappelka. = 2007.=20 Stomatal behavior of ozone-sensitive and =13insensitive coneflowers = (Rudbeckia=20 laciniata var. digitata) in Great Smoky Mountains National Park. New = Phytologist=20 173: 100-109.=20

Grulke NE, Paoletti E, Heath RL. 2007. Chronic vs. short term acute = O3=20 exposure effects on nocturnal transpiration in two Californian oaks. The = Scientific World 7(S1):134-140. DOI 10.1100/tsw.20007.33=20

Grulke, NE, Paoletti, E, Heath, RA. 2007. Comparison of calculated = and direct=20 measurements of foliar O3 uptake in crop and native tree species. = Environmental=20 Pollution 146:640-647.=20

Holmes, WE, DR Zak, KS Pregitzer, and JS King. 2006. Elevated CO2 and = O3=20 alter soil nitrogen transformations beneath trembling aspen, paper = birch, and=20 sugar maple. Ecosystems 9:1354-1363.=20

Karnosky, DF, JM Skelly, KE Percy, and AH Chappelka. 2007. = Perspectives=20 regarding 50 years of research on effects of tropospheric ozone air = pollution on=20 U.S. Forests. Environmental Pollution 147:489-506.=20

Karnosky, DF, H Werner, T Holopainen, K Percy, T Oksanen, E Oksanen, = C=20 Heerdt, P Fabian, J Nagy, W Heilman, R Cox, N Nelson, and R Matyssek. = 2007.=20 Free-air exposure systems to scale up ozone research to mature trees. = Plant=20 Biology 9:181-190.=20

King, JS, CP Giardina, KS Pregtizer and AL Friend. 2007. Biomass = partitioning=20 in red pine (Pinus resinosa Ait.) along a chronosequence in the Upper = Peninsula=20 of Michigan. Canadian Journal of Forest Research 37:93-102.=20

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