SAES-422 Multistate Research Activity Accomplishments Report
Project No. and
Title:
NE1030 Characterization and Mechanisms of Plant
Responses to Ozone in the U.S.
Period Covered:
10-2010 to 09-2011
Date of Report:
30-Sep-2011
Annual Meeting
Dates:
27-July-2011 to 29-July-2011
Participants
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Best, Teodora Best (txo115@psu.edu) - Pennsylvania State
University
Booker, Fitzgerald (fitz.booker@ars.usda.gov) - USDA-ARS,
Raleigh, NC (Connected Remotely)
Burkey, Kent (kent.burkey@ars.usda.gov) - USDA-ARS Plant
Science Unit, Raleigh, NC
Chappelka, Art (chappah@auburn.edu) - Auburn University
Grantz, David (david@uckac.edu) - University of California Riverside
Grulke, Nancy (ngrulke@fs.fed.us) – USFS-Bend, OR (Connected
Remotely)
Knighton, Raymond (Rknighton@nifa.usda.gov) USDA-NIFA,
Washington, DC (Connected Remotely)
Kohut, Robert (rjk9@cornell.edu)- Cornell University (retired)
McGrath, Margaret (mtm3@cornell.edu) - Cornell University
Neufeld, Howard (neufeldhs@appstate.) - Appalachian State
University (Connected Remotely)
Brief Summary of Minutes of Annual Meeting
The 2011 meeting of the NE-1030 Multi-State Project Technical Committee
was held at Schoodic Environmental Center in Acadia National Park,
Winter Harbor, ME July 27-29. The meeting was called to order at 8:10
am 27 July 2011 by chairman Art Chappelka. The meeting agenda was
discussed followed by introductions by those attending the meeting in
person and remotely via conference telephone and GoToMeeting web
connection for presentations.
Station reports were then presented. Kent Burkey (NC) reported on
soybean introductions previously shown to exhibit differential ozone
tolerance were subjected to season long ozone exposures in open-topchambers. Using these data certain soybean varieties were selected for
crossing. A genetic cross has been made between Fiskeby III and
Mandarin Ottawa and a set of 240 random inbred lines developed for
future studies to map ozone tolerance genes in soybean. Teodora Best
(PA) reported on data used to develop genomic resources for the analysis
of traits related to ozone response in black cherry. There were two
objectives 1) Develop a sequence database for expressed genes in black
cherry using RNA isolated from the ozone-treated tissues of ozonetolerant/-sensitive trees. Two cDNA libraries derived from Prunus serotina
tissues were sequenced using Roche 454 technology, 2) Construct a
genetic linkage map for two full-sib black cherry populations segregating
for ozone sensitivity, which will serve as the reference map for the
Ap
species. David Grantz (CA) described recent research focusing on diurnal
trends in ozone sensitivity of vegetation. While the diurnal nature of ozone
sensitivity is confirmed, the mechanism remains to be elucidated. These
data indicate that parameterization of models of ozone injury to
vegetation will require measures of inherent defense capability, for which
time of day may be a key determinant. Ozone impacts on plants with C4
photosynthetic systems is also being investigated. Application of methyl
jasmonate was shown to have an additive, but no protective effect, on
ozone tolerance of Pima cotton. Continued studies of genotoxicity of ozone
in Pima cotton, using the Comet assay (alkaline single cell electrophoresis)
demonstrated that fine roots do not exhibit chromosomal damage. Art
Chappelka (AL) reported that clover biomass and nutritive quality were
affected by ozone, however, grasses growing the same community were
not. Rabbits fed elevated ozone forages were found to have lower DM,
ADF, and NDF digestibility. Forages treated with elevated ozone increased
bound phenolic composition which were correlated with lower DM, ADF,
and NDF ingestibility. Digestibility depression in forages contributed to
lower ingestion and utilization of energy. Dennis Decoteau (PA) presented
information regarding a teaching module for demonstrating ozone effects
on plants that has been developed at The Air Quality Learning and
Demonstration Center at Penn State. The ozone module has been tested
and is already being used in high school classrooms in Pennsylvania. The
module is available for download by educators and the general public at
various public websites. Research was continued in 2010 on Long Island,
NY, (McGrath, NY) at Cornell’s research center (LIHREC) in Riverhead to
further an investigation of the impact of ambient ozone on plant
productivity using the snap bean system developed by project
cooperators. Ozone injury occurred in all plantings. Quaking aspen,
cutleaf coneflower and spreading dogbane were set up in plots in national
parks and monitored during 2006-10 (Kohut, guest). Plots with elevated
soil moisture were selected. Different symptoms of ozone injury were
observed on cutleaf coneflower in the Rocky Mt and Smoky Mt national
parks.
After the presentations a general discussion occurred regarding the station
reports. Reduced funding for ozone research and challenges experienced
obtaining funding were also discussed. Concern was voiced and discussed
about the future of the study of plant response to ozone as a whole
generation of scientists is being lost now due to lack of funding with no
new scientists being trained, while this air pollutant continues to be an
increasing problem. Ray Knighton gave a presentation via conference call.
General budgetary constraints and funding challenges at the federal level
were described. Lack of funding for travel was the reason Ray was only
able to attend the meeting remotely, as was also the case for most
committee members who did not attend in person. The Agriculture and
Food Research Initiative (AFRI) was described, including opportunities in
this program for research pertaining to air pollution. Mechanisms of plant
response to stresses is a priority under Biology of Agriculture Plants. A
challenge with the APRI program is the need for large, multi-institutional
grants that integrate research with extension and/or education. Climate
Change Program is a Challenge Area that should be an appropriate fit for a
proposal from our group.
A field trip to Acadia National Park was taken by the members on July 28.
Sites used in previous ozone bioinidicator studies were examined and a
presentation was made by park personnel regarding their research in the
park.
Business Meeting (27 July and 29 July)
The future of this Multistate Ozone Effects Project was discussed. Our
proposal was approved to renew the project as a Coordinating Committee.
The project expires on 30 September 2012. The final report probably is
due 6 months after this date; this needs to be confirmed. Preparing the
report was discussed. Fitz Booker, David Grantz and Art Chappelka agreed
to take leadership on preparing the final report. Grant proposal topics and
potential funding sources were discussed. There was a lengthy discussion
of collaborations that could work with the range of expertise among the
committee members. Some topics included:
1. examining the effect modern variety development has had on ozone
sensitivity by comparing heirloom versus modern lines of vegetable, 2.
building on interesting results from initial work undertaken by committee
members on ozone and herbivore interactions, 3. relationship to ozone
sensitivity and defense mechanisms of the timing and seasonality of high
ozone episodes, and 4. the relationship between ozone episodes and
drought stress comparing natural and agricultural ecosystems.
Bend, OR in May – June 2012 was selected as the next meeting site and
time period, which Nancy Grulke agreed to host.
Meeting adjourned at 10:30 am on 29 July 2011.
Minutes prepared by Margaret McGrath, Cornell University.
Accomplishments
Objective 1. Describe the spatial - temporal characteristics of the adverse
effects of current ambient O3 levels on crop productivity, including the
development of numerical models to establish cause-effect relationships
that apportion the ozone contribution.
(IL) Ozone impacts on soybean quality in IL was reported by Ainsworth.
An experiment involving 10 soybean cultivars was performed to evaluate
agronomic and seed composition changes caused by exposure to elevated
ozone concentrations. The 10 cultivars selected have all contributed
significantly to North American soybean breeding efforts. Field
observations were made to evaluate appropriate response variables and
estimate their correlation with yield loss due to elevated ozone. Evaluated
responses included foliar damage, leaf chlorophyll content, photosynthetic
rates, plant height, stem diameter, leaf size, time to maturity, seed
weight, seed oil/protein content, and yield. Highly significant relationships
were observed between all of these responses and ozone concentration,
while the strongest correlations with yield loss due to ozone were with
physiological responses such as plant height, leaf size, and foliar damage.
Although little effect on seed oil and protein content was observed, seed
from plants grown in elevated ozone showed an altered fatty acid profile,
resulting in seed with higher levels of undesirable polyunsaturated fatty
acids.
(NY) Research on ozone-sensitive and ozone-resistant snap bean lines was
continued in 2010 (McGrath, NY) using field-grown plants. The lines,
sensitive S156 and resistant (tolerant) R331, were developed at the
USDA-ARS Air Quality Research Unit in Raleigh, NC, to be used to
investigate the impact of ambient ozone (O3) on plant productivity.
Exposure to ozone caused acute foliar injury in all three plantings. The
visible symptom was bronzing. The sensitive line was more severely
affected than the tolerant one. The O3-sensitive snap bean line S156
yielded numerically less than the tolerant line R331 when grown under
ambient O3 conditions on Long Island in 2010. However, yield was not
always significantly less.
(NJ) Using these same lines Zilinskas (NJ) analyzed 2009 growing season
data. A statistically significant decrease in total pod fresh weight of
marketable snapbeans was observed in S156 relative to R331 in three of
the five harvest dates, where the fresh weight of marketable pods of the
ozone-sensitive cultivar was between 37% and 73% less than that of the
ozone-tolerant cultivar. A final harvest of snapbeans was conducted at 84
days after planting. The number of seeds and the dry weight of seeds and
pods from the two cultivars were significantly different, with yield
reductions in the sensitive relative to the tolerant cultivar of 26%, 47%
and 50%, respectively. There was no significant difference in the pod
number of the sensitive cultivar relative to the tolerant cultivar.
(CA) Ozone impacts on plants with C4 photosynthetic systems. Novel
feedstocks for biofuel production will require evaluation of environmental
responses, including to tropospheric ozone. In potential production areas
in southeastern California, ozone exceedances persist due to in-migration
of urban plumes. We have showed previously that growth of a range of
Saccharum clones was differentially responsive to ozone. This was
reinforced with data on photosynthetic responses, including carbon
assimilation responses to photon flux density and to intercellular carbon
dioxide. This further confirms the conclusion that C4 crops are similar to
C3 crops in exhibiting a range of ozone sensitivity. It is not warranted to
assume that C4 crops will exhibit the high levels of ozone tolerance
observed in early studies.
(NC) Open-top chamber studies were initiated to test the feasibility of
identifying ozone-tolerant soybean cultivars based on pedigree analysis.
Two ozone-tolerant soybean ancestors, two cultivars genetically related to
the tolerant ancestors, and two ozone-sensitive ancestors are being
compared using season long exposures to four different ozone
concentrations ranging from sub-ambient to twice current ambient levels.
Ozone responses are being evaluated in terms of foliar injury, seed yield,
and antioxidant metabolism.
Objective 2. Assess the effects of O3 on structure, function and interspecies competition in managed and native plant populations, including
alterations in their nutrient quality.
(PA) To evaluate tree of heaven as a bioindicator for ozone pollution, seed
from six locations across the country were exposed to ozone using
continuously stirred tank reactor (CSTR) chambers on the campus of Penn
State University, PA. During fumigation, seven of the 16 CSTR chambers
were programmed to 75 ppb ozone concentration (the low ozone
treatment), seven were programmed to 120 ppb (the high ozone
treatment), and two chambers were programmed to 0 ppb ozone (the
control treatment). During fumigation of these tree of heaven seed
sources, it was observed that the most susceptible of these seed locations
was Corvallis, Oregon and the least susceptible was Far Rockaway, New
York.
(MA) Weekly foliar sprays of EDU reduced ozone injury symptoms on
leaves of Hibiscus syriacus L. ‘Minerva’ growing at the Millerose Park
Research Station outside Turin, Italy. Leaves located on the western side
of the hedge (exposed to more light) exhibited @3X more ozone injury
than leaves on the eastern side of the hedge. When transferred to opentop chambers seedlings exposed to NF air exhibited ozone symptoms, but
those in CF air did not. This validated symptoms from Mellerose Park and
demonstrated that ozone-sensitivity is a heritable trait in this species.
(AL) Two separate studies to quantify effects on community structure and
function were conducted and reported on: 1): Southern Piedmont plant
communities exposed to different ozone concentrations in combination
with altered rainfall predictions over a growing season: 2): Grassland
forage species grown under different ozone concentrations and fed to
rabbits in feeding trial to estimate digestibility and energy differences
between treatments. Regarding experiment 1, Sensitive species (clover)
biomass and nutritive quality adversely affected by ozone Individual
grasses: fescue and Bermuda. Grasses as a growth type insensitive,
tended to have greater biomass and nutritive quality. Precipitation had
minimal effects due to water treatment blocks and also high rainfall year.
The conclusions regarding experiment 2 are as follows; 2X forages
determined to have lower DM, ADF, and NDF digestibility. 2X forages
increased bound phenolic composition which was correlated with lower
DM, ADF, and NDF ingestibility. Implications for lower nutritive quality in
pastures exposed to ozone. Digestibility depression in 2X forages
contributed to lower ingestion and utilization of energy.
Objective 3. Examine the joint effects of O3 with other growth regulating
factors (e.g., CO2, temperature) that are expected to vary with ongoing
climate change on crop growth and productivity.
(NC) Climate change factors such as rising atmospheric CO2 and ozone
can exert significant impacts on crop growth, but it remains largely
unexplored how the soil microbes in agricultural systems respond to these
factors. This severely hinders our ability to predict soil carbon
sequestration potential. Using a long-term field study conducted in a notill wheat-soybean rotation system with open-top chambers, ARS
researchers in Raleigh, NC showed that elevated CO2 stimulated plant
biomass production and ozone lowered it, but only elevated CO2
significantly affected soil microbial biomass, respiration and community
composition. Enhancement of microbial biomass and activities by elevated
CO2 coincided with increased soil nitrogen availability, likely due to
stimulation of soybean nitrogen-fixation under elevated CO2. These
results highlight the need to consider the interactive effects of carbon and
nitrogen availability on microbial activities when projecting soil carbon
balance under future CO2 scenarios. The addition of nitrogen to
agricultural systems through fertilizers or legume crops may stimulate
microbial decomposition processes and limit carbon sequestration
potential. Our results also suggest that projected ozone concentrations
under future climate scenarios may reduce plant productivity but have
limited impact on soil microbial processes.
(NC) A prototype Air Enrichment System (AES) was designed and built
that provides a clean-air (charcoal-filtered) environment along with
elevated temperature, ozone and CO2 treatment capabilities (NC). The
AES uses passive solar heating and electrical resistance heaters to elevate
the air temperature 2.2 ± 0.4 °C and adds moisture to maintain relative
humidity. Two prototype units and ambient plots were planted with
soybean in June 2011. Harvest and environmental data are being
summarized for use in a crop growth computer model.
(NC) ARS researchers developed the "water stress field", a form of
precipitation exclusion technology, for the multiple purposes of studying
the physiology of water stress, comparing genetic lines of soybean and
snap bean for desirable water stress characteristics and to examine the
interactions between soil moisture levels and the toxic effects of ambient
atmospheric ozone. The 2008 and 2009 data were used to develop a
model for soybean predicting leaf conductance from measurements of soil
volumetric water content in the profile down to 40 cm. Coupled with
ambient ozone measurements a flux based risk assessment model, based
on soil moisture is also being developed.
(NC) Five wheat varieties with different levels of susceptibility/resistance
to the wheat stripe rust pathogen, Puccinia striiformis, were vernalized
and grown under combinations of elevated carbon dioxide, ozone, and
atmospheric vapor pressure deficit. Ozone significantly damaged the
growth and seed production of all five varieties. Carbon dioxide promoted
growth and lessened the effects of ozone. Vapor pressure deficits were too
low to allow for rust development in the leaves. In a second experiment in
open-top chambers, 60 varieties of wheat, barley, and oat juvenile plants
were shown to vary widely in response to ozone exposure, with oat and
barley varieties exhibiting greater leaf discoloration than wheat.
Objective 4. Examine the physiological and molecular basis of O3 toxicity
and tolerance in plants.
(PA) A new project expanded the analysis of the genetic response of
hardwood tree species to ozone. Messenger RNA was isolated from leaf
tissues of control and ozone-treated Red Oak seedlings. The mRNA preps
were sequenced by the 454-Roche technology. A database of over 1
Million sequence reads was created; the reads were assembled into
transcript contigs which were annotated by BLAST. The transcript contigs
fell into a very similar array of functional categories as observed with
black cherry. They observed that expression of chloroplast stress-response
genes were up-regulated after 30 days, while stress-response genes in the
mitochondria were down-regulated. Also, both heat shock proteins and
ubiquitins were up-regulated. HAG1 was up-regulated in the nucleus as
well, which functions in unfolding chromatin, for the binding of
transcription factors.
(PA) The Carlson Lab focused their research on characterizing and
understanding the genetic basis of variation in sensitivity to ozone stress
in forest trees. They developed a community resource for comparative
and functional genomics in Prunus serotina which provides tools for black
cherry tree improvement and for sustainable forest management. They
observed by comparing black cherry data from the EST sequencing with
data from Arabidopsis obtained by microarray analysis of ozone
treatments, that in black cherry fewer genes were both up-regulated and
down-regulated than in Arabidopsis.
(IL) Variation in ozone tolerance in five agriculturally important legume
species was reported by Ainsworth. The O3 response of Glycine max,
Pisum sativum, Phaseolus vulgaris, Cicer arietinum and Medicago sativa all commercially relevant crops, important for global food security was
compared in a growth chamber experment. When grown in elevated
chronic O3, in situ measurements of stomatal conductance and
photosynthesis revealed a broad range of O3 sensitivities. The most
sensitive species, P. vulgaris and M. sativa, each had decreases in
stomatal conductance of 55%, while the most tolerant species, P. sativum,
was not significantly different from ambient-grown plants. Whole plant
characteristics such as leaf longevity, total plant leaf area and biomass, as
well as biochemical markers of antioxidant capabilities such as apoplastic
ascorbate, were consistent with the O3 sensitivities determined from gas
exchange analysis. The results reveal a large degree of variation in
tolerance among legume species, much more so than within soybean
alone.
(PA, NC) A collaborative project (C. Wiese) in collaboration with Dr. Kent
Burkey and Dr. Fitz Booker in the Plant Science Unit at USDA-ARS in
Raleigh, NC, is to determine the role of the apoplast in plant defense
responses to oxidative stress. The specific objectives of this study are to
investigate whether there are differences in the apoplastic constituents of
two genotypes each of soybean and snap bean which differ in their O3
tolerance, and whether exposure to O3 affects the quantity and types of
apoplastic constituents in these genotypes. The tolerant R123 and
sensitive S156 snap bean genotypes were exposed to charcoal-filtered
(CF) air or elevated O3. Leaf intercellular wash fluid (IWF) was analyzed
for ascorbic acid and also by reversed-phase HPLC for other apoplastic
constituents of interest. While there were initial differences in apoplastic
ascorbate between the two genotypes, these differences were no longer
apparent after several days of O3 exposure. Exposure to O3 resulted in an
increase in total ascorbic acid quantities in both genotypes. Phaselic acid
(caffeoylmalate) was identified by HPLC-Mass Spectrometry as a major
constituent of the snap bean apoplast. The quantities of phaselic acid were
significantly higher in the O3-treated samples than the CF samples of both
snap bean cultivars at both time-points in the exposure. On the first day
of the exposure, phaselic acid quantities were also significantly higher in
the tolerant R123 genotype than in the sensitive S156. Therefore, it is
possible that phaselic acid, due to the large quantities found in the
apoplast and the increases in phaselic acid in O3-treated plants, may play
a role in determining plant sensitivity to O3. Further investigations will
address the role of phaselic acid in the apoplast, its interactions with other
apoplast constituents and its role in potential detoxification reactions
occurring in the apoplast.
(CA, NC) A collaboration of the University of California at Riverside (R.
Heath) University of California Kearney Agricultural Center (D. Grantz),
and USDA/ARS (K. Burkey) has developed the first demonstration that
defense capacity of leaves against ozone varies diurnally. This year we
have developed a more straightforward means of analyzing the diurnal
trends in ozone sensitivity of Pima cotton, cv. S-6, grown in a greenhouse.
Preliminary data were presented at last year’s meeting. The experiment
was repeated with constant and with variable irriadiance. The additional
effect of light stress was evaluated and found to not be a factor in the
diurnal sensitivity. The new analysis uses slopes of responses to ozone
flux to define a sensitivity parameter. These parameters are better
behaved than the extrapolated damage parameter presented previously.
These sensitivity parameters may prove useful in support of efforts to
model extensive regional impacts of ozone on vegetation. Total
antioxidant capacity, ascorbic acid and dehydroascorbic acid content were
determined on non-exposed leaves at different times of day, but did not
explain a substantial part of the diurnal variability. Regression
relationships between sensitivity to O3 injury and various measures of
antioxidant status were not significant. While the diurnal nature of ozone
sensitivity is confirmed, the mechanism remains to be elucidated. These
data indicate that parameterization of models of O3 injury to vegetation
will require measures of inherent defense capability, for which time of day
may be a key determinant.
(NC) Final steps were completed in the development of a soybean
population to map stress tolerance genes for drought, iron deficiency
chlorosis, ozone, salt, and toxic soil aluminum. The mapping population
consists of 240 random inbred lines developed from a cross between
Fiskeby III and Mandarin Ottawa plant introductions. Seed increases were
completed and initial screening of the population for ozone, drought and
iron deficiency chlorosis begun. DNA for use in SNP marker assays was
extracted from leaf tissue for approximately 90% of the random inbred
lines.
Objective 5. Develop educational tools and conduct advanced training for
K-12 public school teachers, college level instructors, and outreach
educators regarding the effects of ambient O3 pollution on plants.
(CA) Grantz in California continues to provide greenhouse exposure
chambers that are used to demonstrate ozone symptoms to visiting school
and industry groups and international visitors from commodity outreach
programs.
(CA) Grantz continues to address school groups and industry
organizations, and worked with individual commodity groups to explain
the importance of air quality improvement. Active involvement continues
with efforts to reduce the carbon footprint of energy production.
(NC) Participated in the UNECE/ICP Vegetation ambient ozone
biomonitoring project (snap bean project). Sensitive and tolerant snap
bean lines were grown at our field site and monitored for visible injury,
stomatal conductance, photosynthesis and yield. Results of the
experiment along with meteorological data and hourly ozone
measurements were forwarded to project organizers for incorporation into
their multi-location study and flux modeling investigations.
(NC) Seeds of ozone-sensitive and ozone-tolerant snap bean were
provided to UNECE/ICP Vegetation for use in their multi-location
biomonitoring and flux-modeling projects.
(NC) Ozone-sensitive and ozone-tolerant snap bean lines were used in
laboratory exercises in two classes at NC State University (Environmental
Technology 202 and Crop Physiology 714) to teach students about the
impacts of ozone on plants. Students measured photosynthesis, stomatal
conductance, chlorophyll fluorescence, biomass and leaf area of both
genotypes following treatment with clean air or 75 ppb ozone for 20 days.
Data were compiled and students presented the results in classroom
discussions.
(NC) Maintenance of a web educational presence. Booker of USDA in NC,
the Web Master for the NE-1030 Project, developed and maintained a
project web page at (http://www.ncsu.edu/project/usda-ne1013/index.htm). This web page is frequently updated with current news
items, project annual report and news of the project such as minutes of
the 20010 annual meeting. (NC).
Impacts
1. Personnel from this Multi-State Project have provided data to state
and federal regulatory bodies and Agricultural Air Quality Task
Force as air quality standards and policies are revised. Wilderness
and National Park managers have utilized Project data to
document long term impacts of ozone on unmanaged vegetation.
Across a broad spectrum of stakeholders, tropospheric ozone is
recognized as an element of global change that interacts with
other elements, such as temperature, moisture and nitrogen.
2. Arrangements are being made with Carolina Biological Supply Co.
in Burlington, NC to market the ozone-sensitive and ozonetolerant snap bean lines commercially. Seeds and an instructional
manual for conducting experiments with the snap beans in ozone
projects will be made available.
3. Public educational facilities are in operation in California and
Pennsylvania, and a comprehensive web presence is maintained in
North Carolina to provide information that is relevant locally,
nationally and internationally, with respect to ozone air pollution.
4. Ozone-sensitive and ozone-tolerant snap bean lines were used in
laboratory exercises in two classes at NC State University
(Environmental Technology 202 and Crop Physiology 714) to teach
students about the impacts of ozone on plants.
Publications
Aspinwall, MJ, JS King, FL Booker and SE McKeand. 2011. Genetic effects
on total phenolics, condensed tannins and non-structural carbohydrates in
loblolly pine (Pinus taeda L.) needles. Tree Physiology 31:831-842.
Betzelberger AM, Gillespie KM, McGrath JM, Koester RP, Nelson RL,
Ainsworth EA (2010) Biochemical, physiological and yield variation in
soybean cultivar responses to chronic elevated ozone concentration. Plant,
Cell Environment 33: 1569-1581.
Cheng, L., Booker, F.L., Burkey, K.O., Tu, C., Shew, H.D., Rufty, T.,
Fiscus, 0000251160E.L., Hu, S. 2011. Soil microbial responses to elevated
CO2 and O3 in a wheat-soybean agroecosystem. PLoS One. 6:e21377.
Chrzanowski, S., D. D. Davis, and D. R. Decoteau, 2011. The Air Quality
Learning and Demonstration Center at Penn State’s Teaching Module for
Demonstrating Ozone Effects on Plants. US EPA AirNow Conference
(http://airnow.gov/index.cfm?action=naq_conf_2011.aq3)
Decoteau, D.R. 2011. Air Pollution Symptoms, 2011 Mid-Atlantic Fruit &
Vegetable Convention Proceedings pages 10 – 11.
Grantz, D.A., Vu, H. B., Heath, R. L., Burkey, K. (2011). Diel trends in
plant sensitivity to ozone: Toward parameterization of the defense
component of effective flux. Abstract American Geophysical Union, Annual
Meeting. San Francisco, December 2011.
Neufeld, HS, SJ Peoples, AW Davison, AH Chappelka, GL Somers, JE
Thomley and FL Booker. 2011. Ambient ozone effects on gas exchange
and total non-structural carbohydrate levels in cutleaf coneflower
(Rudbeckia laciniata L.) growing in Great Smoky Mountains National Park.
Environmental Pollution:In press.
Niyogi, D., Mera, R., Xue, Y., Wilkerson, G., Booker, F.L. 2011. The use of
0000254469 Alpert-Stein Factor Separation Methodology for climate
variable interaction studies in hydrological land surface models and crop
yield models. In: Factor Separation in the Atmosphere. Cambridge
University Press. Book Chapter. 171--183.
Ren, W., H. Tian, B. Tao, A. Chappelka, G. Sun, C. Lu, M. Liu, G. Chen and
X. Xu. 2011. Impacts of tropospheric ozone and climate change on net
primary productivity and net carbon exchange of China’s forest
ecosystems. Global Ecol. Biogeogr. 20: 391-406.
Tian, H. G. Chen, M. Liu, C. Zhang, G. Sun, C. Lu, X. Xu, W. Ren, S. Pan,
A. Chappelka. 2010. Model estimates of net primary productivity,
evapotranspiration, and water use efficiency in the terrestrial ecosystems
of the southern United States during 1895–2007. For. Ecolog. & Mang.
259: 1311-1327.
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