Annual Report (2001)

 

Title: NE-176 - Characterization and Mechanisms of Plant Responses to Ozone (O3) in the Northeastern US

 

 

1.         Alabama

 

 

Investigator Name(s)             A.H. Chappelka

 Period Covered:   01/01/01 to 12/31/01

 

 Progress Report:

A study investigating the effects of ambient ozone on native plant communities growing in the Great Smoky Mountains National Park (GRSM) was conducted in 2001. Plants were rated for symptoms of ozone, and measured for rates of stomatal conductance and net photosynthesis. In addition, ozone profiles within plant canopies were examined. Plant symptoms on cutleaf coneflower were found to be greater near trails than off-trail, and greater on the lower leaves. Symptoms increased during the growing season. Cut leaf coneflower was found to be very sensitive to regarding visible symptom expression. Similar results were found with crownbeard, although this species was not as sensitive to ozone. To determine if ambient ozone concentrations are affecting the growth of yellow-poplar and black cherry, trees previously identified regarding ozone sensitivity were re-evaluated for visible sensitivity to ozone and re-cored at three sites within the GRSM in the vicinity (< 2 km) of ambient ozone monitors during 2001. Data are currently being analyzed.

 Impact:

Results from these studies will provide information to decision makers so adequate protective standards can be developed.

Publications:

Krupa, S. M.T. McGrath, C.P. Andersen, F.L. Booker, K.O. Burkey, A.H. Chappelka, B.I. Chevone, E.J. Pell and B.A. Zillinskas. 2001. Ambient ozone and plant health. Plant Disease 85: 4-12.

 

2.         Maryland

 

 

Name of Investigator:  C.L. Mulchi

 

Institution:  Maryland Agricultural Experiment Station

 

Period:  01-01-2001 to 12-31-2001

 

Objective:  Whole Plant Foliar Injury, Growth and Yield Responses (Objective #1):  A.  Assessing Ozone Tolerance Among Soybean Cultivars Grown in Mid-Atlantic Region.  B.  Examining Ozone Effects on Yields and Grain Quality of Soybeans.

 

Progress Report

 

Twenty-four cultivars, 8 each from maturity groups III, IV, and V, were selected from entries in the MAES Soybean Variety Testing Program and grown full-season in 5-m diameter open-top chambers exposed to charcoal-filtered air (8 hr Av. O3 = 27.4 ± 11.8 nL L-1) and non-filtered air + O3 (8 hr Av. O3 = 55.7 ± 20 nL L-1).  The cultivars represented a combination of public and commercial lines with a high percentage exhibiting tolerance to the herbicide Glyphosate (RoundUp®).  Relative chlorophyll contents were measured in fully expanded upper canopy leaves on two dates during early pod development.  The plants were harvested in mid-October, thrashed and data collected for seed wt. m-2, seed wt. 100-1 and seeds plant-1.  Ozone Tolerance Index (OTI) values were calculated for each line based on summing the ratios of CF/NF + O3 for the yield characteristics data above.  OTI values ranged from 2.78 (tolerant) to 5.39 (highly sensitive) with 8 of the 24 showing values ≥ 4.0, thus exhibiting moderate to high sensitivity to O3.  Grain from the 24 lines will be analyzed for oil, protein, and fatty acid composition.

 

Grain samples from 1999 and 2000 studies involving 21 cultivars, 7 each from groups III, IV, and V exposed full season to charcoal vs. elevated O3 levels were analyzed for oil, protein, and fatty acids composition.  Protein contents were largely unaffected by treatments in all groups; however, oil contents were lowered by the elevated O3 in group III.  The 16:0 and 18:0 fatty acids were elevated in groups IV and V, and 18:3 levels were lowered in all three groups in response to elevated O3 when cultivar means within a group were combined over years.  Also, the 18:1 fatty acid levels were lower in group III in response to elevated O3 treatments combined over cultivars and years.  Significant differences were observed for several of the fatty acids in response to elevated O3 in individual cultivars within a group when compared against CF controls.

 

Impact

 

Regional effects of air pollution on grain quality has major importance to society, in general, in view of the linkages now being recognized between seed characteristics and value added traits with respect to health.

 

Publications

 

Kim, M.S., C.L. Mulchi, C.S.T. Daughtry, and J.E. McMurtrey.  2001.  Multispectral Fluorescence Imaging for Water Stress and Air Pollution Effects on Crops.  2001 Amer. Soc. Agron. Abstracts, Charlotte, NC.  CD-ROM.

 

Islam, K.R., C.L. Mulchi, B. Momen, and R.R. Weil.  2001.  C, N and N Distribution in Soil Aggregates Under Elevated CO2 and O3 Concentrations.  2001 Amer. Soc. Agron. Abstracts, Charlotte, NC.  CD-ROM.

 

Islam, K.R., C.L. Mulchi, B. Momen, and R.R. Weil.  2001.  Distribution of Soil Organic C Pools in Response to Elevated CO2 and O3 Effects on Crops.  2001 Amer. Soc. Agron. Abstracts, Charlotte, NC.  CD-ROM.

 

 

3.         Maryland

 

Name of Investigator: J. M. Robinson

 

Institution:  Environmental Quality Laboratory, Beltsville Agricultural

Research Center, USDA, ARS, Beltsville, Maryland

 

Period: 01-01-2001 to 12-31-2001

 

Objective:  Characterize whole plant responses to ozone, including carbon

assimilation and allocation, growth and productivity.

 

Progress Report:

 

   The effect of prolonged exposure to elevated ozone (O3) levels on shoot

dry mass, leaflet length, foliar photosynthetic rate (Pn rate), and

stomatal conductance (Gsw) was examined using eight modern soybean

cultivars.  This study was conducted in open-top chambers situated in our

greenhouse system.  Experimental plants were given chronic moderately

elevated O3 (49-59 nL per L) for 20-26 days.  These plants were compared

with counterpart control plants growing in carbon filtered chambers with

low O3 (9-15 nL per L).  Pn rate was not inhibited significantly by

elevated O3 exposure in new fully expanded leaves in any of the eight

cultivars examined.  However, Pn rate was inhibited significantly by

elevated O3 in older mature leaves in some of the cultivars.  For example,

Pn rate was inhibited by O3 exposure in older mature leaves of cv Forrest

and cv Clifford, but not in the older mature leaves of cv Essex and cv

Wicomico.  Also, elevated O3 exposure mediated a significant decrease of

Gsw in new fully expanded leaves as well as in mature leaves of cv Forrest

and cv Clifford but not in those leaflets of cv Essex and cv Wicomico.

Based upon these criteria, cultivars Essex and Wicomico were among the more

O3-tolerant soybean cultivars, while cv Forrest and Clifford appeared to be

two of the more O3-sensitive cultivars.  The results suggest that O3

sensitivity in some soybean cultivars, e.g. cv Forrest and cv Clifford, is

due to the negative influence of O3 on photosynthetic carbon assimilation

and stomatal conductance.  Cultivars Essex and Wicomico may be O3-tolerant,

in part, because their leaf photosynthetic assimilation mechanisms and Gsw

appear to be less sensitive to elevated ozone.

 

Impact:

 

This study makes it clear that when examining soybean leaves for

O3-mediated inhibition of growth, photosynthesis, stomatal movement, and

metabolic processes, it is important to monitor these processes in leaflet

of leaves of all ages, for example, in newly fully expanded leaves as well

as in mature leaves.

 

 

Publications (not previously reported to N-176 by Mike Robinson)

 

Chernikova T., Robinson J.M., Lee E.H. and Mulchi, C.H.  2000.  Ozone

tolerance and antioxidant enzyme activity in soybean cultivar.  Photosynth

Res 64(1): 15-26.

 

Robinson J.M. and Britz, S. J.  2000.  Tolerance of a field grown soybean

cultivar to elevated ozone level is concurrent with higher leaflet ascorbic

acid level, higher ascorbate: dehydroascorbate redox status, and long term

photosynthetic productivity.  Photosynth Res 64(1): 77-87.

 

Britz S J. and Robinson, J.M.  2001.  Chronic ozone exposure and

photosynthate partitioning into starch in soybean leaves.  Int J Plant Sci

162 (1): 111-117

 

Robinson J.M. and Britz, S.J.  2001.  Ascorbate-dehydroascorbate level and

redox status in       leaflets of field grown soybeans exposed to elevated

ozone levels.  Int J Plant Sci 162 (1): 119-125.

 

Robinson J.M. and Britz, S.J.  2001.  Characterization of antioxidants and

chlorophyll content within peach and apricot cultivars grown under open-top

chamber conditions and ambient ozone exposures in south central

Pennsylvania.  In: A Combined First Year Report of Findings with

Contributuions Concerning " Screening Fruit Tree Species within the Genus

Prunus Grown under Open-Top Chamber conditions and Ambient Ozone Exposures in

South Central Pennsylvania,  by Skelly J. M., Ferdinand, J, Stevenson R,

Savage JE, Halbrendt J. and  Halbrendt N. Contribution No. ER 2000-3,

Report 2. 2001. pp 1-15.

 

4.         Massachusetts

 

 

Name of the Investigator:  W.J. Manning

 

Institution:  University of Massachusetts

 

Period:  01-01-2001 to 12-31-2001

 

Progress Report

 

Two snapbean (Phaseolus vulgaris) lines have been made available to members of this project by the ARS/USDA Air Quality Research Program at Raleigh, NC. R123 is tolerant of ozone injury, S156 is susceptible to ozone injury. We have begun to determine how morphological characteristics and rate of growth affect the response of these two lines to ozone in continuously-stirred reaction chambers (CSTRs) and in the field in open-top chambers (OTCs) and ambient air plots (AA). In CSTRs, ozone at 80 ppb S156 produced less biomass and more flowers and pods than R123. S156 pods, however, either aborted soon after formation or remained immature. R123 had larger pods and seeds than S156. In OTCs in the field, R123 plants had higher aboveground biomass in charcoal-filtered air (CF), non-filtered air (NF), and ambient air (AA) than S156 plants. R123 plants in AA produced more seeds than those grown in CF. Root/shoot ratios and seed weight/plant were also higher in R123 in AA than in CF. Differences like this were not observed in S156 plants. We have begun a project on assessing the impact of ambient ozone on wine grapes (Vitis vinifera) in coastal vineyards in Massachusetts, Connecticut and Rhode Island. Red wine cultivars Chancellor and Pinot Noir and the white wine cultivar Chardonnay sustained extensive foliar stipple in summer 2001. Bi-weekly applications of the antioxidant sodium erythorbate, at 500 or 1000 ppm a.i. reduced stipple on less susceptible cultivars Cabernet Franc (red) and Vidal (white). The exposed sides of north/south rows sustained the most foliar injury. Ozone is borne on southwest winds from the New York/New Jersey metroplex. Two PhD students are working on this project. Their assistantships are not supported by the project.

 

Impact

 

Our results are fundamental to understanding the factors that affect ozone uptake and plant injury. This has a direct bearing on air quality standards for all people and for agro and natural ecosystems. The use of bioindicators of ozone will increase awareness of the ozone problem by all people.

 

Publications

 

Bergweiler, C.J. 2001. Characterization of ambient ozone uptake and development of foliar injury models from a –plant physiological ecology perspective. PhD Dissertation.

 

 

5.         Minnesota

 

Investigator(s): S.V.Krupa

Reporting period: 01/01/2001 to 12/31/2001

 

Progress Report:

In ecological effects research, there is a rapid increase in the application of passive sampling techniques for measuring ambient ozone (03) concentrations. Passive samplers provide data on cumulative exposures of a plant to a pollutant. However, 03 is not an accumulative contaminant within the plant tissue and use of prolonged passive sampling durations cannot account for the dynamics of the occurrences of 03 that have a significant influence on the plant response. Therefore, a stochastic Weibull probability model was developed and applied to a site in Washington State (1650 m MSL) to simulate the cumulative exposure data from a passive sampler to mimic the corresponding frequency distributions of hourly 03 concentrations that would otherwise have been obtained by continuous monitoring. The simulation of the hourly ozone data was based on and compared with the results obtained from a co-located continuous monitor. At that site the initial correlation between the actual weekly average values from the passive sampler and the corresponding continuous monitor data was, R2 = 0.74. Subsequently the model was applied to data from an unrelated monitoring site (New Hampshire, 476 m MSL) showing poor initial correlation between the actual average values from co-located passive sampling and the co-located continuous monitoring (R2 = 0.24). In spite of the major difference in the R2 values, at both sites the simulation provided very satisfactory results of the frequency distributions of the synthetic hourly ozone concentrations, in comparison to the actual continuously measured, within the 95% confidence interval, suggesting the robustness and broad applicability of the model. The final objective of this overall approach is to develop a generic model that can simulate reasonably well, the occurrences of ambient 03 concentrations that are dependent upon the elevation of the measurement site and the synoptic and local meteorology. Such an effort would extend the relative utility of the passive sampling data in explaining stochastic plant responses on a regional scale.

 

Publications:

Krupa, S.V. 2001. Surface level ozone and its adverse effects on crops and forests: A need for interdisciplinary understanding. TheScientificWorld 1: 148-149.

 

Krupa, S. and Nosal, M. 2001. Relationships between passive sampler and continuous ozone (03) measurement data in ecological effects research. TheScientificWorld 1: 593-601.

 

Krupa, S., Nosal, M.and Peterson, D.L. 2001. Use of passive ozone (O3) samplers in vegetation effects assessment. Environ. Pollut. 112: 303-309.

 

Krupa, S., McGrath, M.T., Andersen, C.P., Booker, F.L., Burkey, K.O., Chappelka, A.H., Chevone, B.I., Pell, E.J. and Zilinskas, B.A. 2001. Ambient ozone and plant health. Plant Dis. 85: 4-12.

 

Impact:

This work is still in its growing stages and therefore, its societal impact, output to target audience and the outcome cannot be gauged as yet. However, it has the potential to verify the regional scale validity of ambient air quality regulations.

 

6.         New Jersey

 

 

Name of the Investigator:  B.A. Zilinskas

 

Institution:  New Jersey Agricultural Experiment Station, New Jersey

 

Period:  01-01-2001 to 12-31-2001

 

Progress Report

 

Ascorbic acid is known to be an effective antioxidant.  Particularly in the apoplastic space of plants, it is thought that ascorbate can counteract some of the damaging effects of ozone.  Recently the ascorbic acid biosynthetic pathway in plants has been elucidated in which GDP-D-mannose, L-galactose and L-galactono-1,4-lactone are key intermediates.  In our laboratory, we have cloned and subsequently overexpressed in tobacco two of the enzymes in the ascorbate biosynthetic pathway, namely GDP-D-mannose pyrophosphorylase (thought to be the rate-limiting enzyme) and L-galactono-1,4-lactone dehydrogenase (the last enzyme in the pathway).  The objective is to try to genetically modify these plants such that they produce more ascorbic acid in order to test whether tolerance to ozone or other forms of oxidative stress will be improved.

 

Impact

 

If ascorbate content can be genetically modified in plants, it may be possible to develop plants that are tolerant of ozone or certain other types of environmental stress.

 

Publications

 

Krupa, S., M.T. McGrath, C. Anderson, F.L. Booker, K.O. Burkey, A.H. Chappelka, B.I. Chevone, E.J. Pell and B.A. Zilinskas. 2001.  Ambient ozone and plant health.  Plant Disease 85:4-12.

 

Bick, J.A., A.T. Setterdahl, D.B. Knaff, Y. Chen, L.H. Pitcher, B.A. Zilinskas and T. Leustek.  2001.  Regulation of plant-type 5’-adenylylsulfate reductase by oxidative stress.  Biochemistry 40:9040-9048.

 

 

7.         New York

 

Name of the Investigator: M. T. McGrath

Institution: Cornell University, New York

Period: 01-01-2001 to 12-31-2001

Objective: Characterize whole plant responses to ozone, including carbon assimilation and allocation, growth and productivity.

Progress Report:

Ozone-sensitive (S) and ozone-tolerant (R) white clover and snap beans were grown on Long Island. Ozone (O3) was >80 ppb for at least 67 hrs on 17 days: 2-4 May; 19, 28, 30 Jun; 1, 9, 10, 25 Jul; and 1, 2, 6-10 Aug (equipment broken 11–31 May and 10–12 Aug). Highest level (122 ppb) was on 9 Aug. Clover was grown in pots or the ground and harvested monthly. Dry wt of leaves and flowers from pot-grown plants differed significantly between clones for all but harvest 2 (30 Jul). Severest O3 episode (started 6 Aug) occurred during growth period 3 when S clone’s growth was reduced most compared to R. Reduction was 17% over the 4 harvests. Average daily 12-hr O3 mean was 41.2, 40.1, 43.8, and 32.1 ppb for the 4 growth periods. Highest daily 12-hr O3 mean was 73.2, 66.4, 85.8, and 62.1 ppb. Daily 12-hr O3 mean exceeded 50 ppb for at least 6 of 38 days, 5 of 28 days, at least 6 of 32 days, and 1 of 26 days. Exposure index AOT40 was 3020, 1752, 3750, and 663 ppb.h. Wt of tissue harvested from field-grown clones did not differ significantly at any time because of poorer growth and greater variation than in pots. This confirms previous results that pot-grown clover is better for a bioindicator system. O3 injury was first seen on S bean line on 7 Aug, following the episode on 1-2 Aug with a peak of 92 ppb. Extensive injury was seen on 14 Aug, when pods were reaching marketable size, following the worst O3 episode of 2001. R line produced a similar number of pods harvested for fresh-market consumption as the S line but they were larger, weighing 38% more. Pod wt was not significantly different at the first of 3 harvests on 16 Aug, just 9 days after injury first seen. Mature bean yield was affected greatly. R line produced 49% more pods/plant and 72% more seeds. Seed wt was 43% greater. Applying herbicide (metolachlor) and insecticide (disulfoton) improved detection of O3 effects most likely by controlling insects that would have had a greater impact on R plants.

Impact: Ambient ozone has been demonstrated to be high enough to greatly reduce growth and yield of sensitive plants on Long Island in one of the most important agricultural counties in New York. Growth of an ozone-sensitive white clover was reduced 17% averaged over the 2001 growing season. A sensitive snap bean line exhibited yield reductions of 27% in weight of beans harvested for fresh-market consumption and 42% in number of seeds at maturity compared to an ozone-tolerant snap bean line.

 

Publications:

Krupa, S., McGrath, M.T., Andersen, C.P., Booker, F.L., Burkey, K.O., Chappelka, A.H., Chevone, B.I., Pell, E.J. and Zilinskas, B.A. 2001. Ambient ozone and plant health. Plant Disease 85: 4-12.

 

8.         New York

 

Effects of Changes in Air Quality on the Genetic Diversity of Plant Populations

 

Robert Kohut, Denise Costich

 

Plants respond to changes in their environment by adaptation, evolution, or, if neither of these approaches is effective, extinction.  Evolution is characterized by a change in gene frequency in a population as a consequence of selection.  For selection to occur, three conditions must be satisfied: phenotypic variation must exist in a character within a population; part of the variation in the character must be under genetic control; and variation in the character must affect reproductive fitness.   If changes in air quality have an impact on a character, if the population shows variation in the level of impact produced, and if the impact has an effect on reproductive fitness, the stress may produce changes in gene frequencies, or evolution, within the population.  My current research focuses on assessing the long-term, independent effects of carbon dioxide and ozone on plant populations, with particular emphasis on their potential to produce changes in population genetic diversity.

 

An on-going study is assessing how gradually escalating levels of carbon dioxide will effect the phenotypic, physiological, and genetic properties of plant populations after several generations of exposure.  The studies use Brassica rapa (Wisconsin Fast-Plant) as the model system for assessment.  Populations are either maintained in ambient levels of carbon dioxide or grown in carbon dioxide environments that increase 10% each generation.  Phenotypic and physiological properties of the populations are assessed each generation, and population genetic diversity is characterized using microsatellite DNA markers.  Every generation, plants in each of the populations are subject to selection based on reproductive fitness as characterized by numbers of seeds produced and percent germination of seed.  The top 25% of the plants in each population, based on reproductive fitness, serve as sources of seed for the following generation.  The study is concluding the fourth generation of exposure.

 

I am also interested in the possible effects ozone may be having on the genetic diversity of plant populations because of its regional distribution and the long-term exposures that have taken place.  Proposals are currently pending to conduct field studies on the long-term effects of ozone on the genetics of black cherry and on ozone-sensitive understory species along gradients of exposure in the northeast.  The proposed studies will assess the distribution of sensitivity to ozone in populations receiving different levels of long-term exposure, and the levels of genetic diversity within the same populations.  Genetic diversity will be assessed using AFLP and microsatellite DNA analyses.  Relationships among level of exposure, distribution of sensitivity, and genetic diversity will be assessed. 

 

 

 

 

Assessment of Effects of Ozone of Forest Resources in the Southern Appalachian Mountains

 

David Weinstein

 

The Southern Appalachian Mountain Initiative (SAMI) is a regional partnership led by eight southern states.  SAMI’s mission is to identify and recommend emissions strategies to remedy existing and prevent future adverse air quality effects in Southern Appalachia, with particular focus on Class I areas.  SAMI’s integrated assessment is evaluating effects of ozone, acid deposition, and fine particles that impair visibility.  SAMI’s Policy Committee has defined air emissions reduction strategies for which emissions, atmospheric transport, exposures, environmental effects, and socioeconomic impacts are being characterized.  The integrated assessment results will be delivered in 2001 and will provide the basis for SAMI policy recommendations to the southern states. 

 

SAMI’s Effects Subcommittee is responsible for the ozone assessment design. The subcommittee includes representatives from state regulatory agencies, the Environmental Protection Agency, US Forest Service, National Park Service, industry, and several environmental organizations.  Boyce Thompson Institute, SAMI’s contractor, is using a multi-model approach to project forest responses to future changes in ozone as a function of SAMI strategies. The U.S. Forest Service’s Forest Inventory and Analysis data was used to characterize forest types and species abundance in each of 12 geographic areas within the SAMI region.   Ozone responses of the most abundant forest types in each area and of unique forest types in selected Class I areas are being represented using the TREGRO and ZELIG models.  TREGRO is a single tree physiology model that incorporates experimentally-determined effects of ozone on leaf photosynthesis to project ozone effects on leaf area, tree height, and root growth.  ZELIG is a stand model that projects forest growth and species composition as a function of available resources (light, moisture, nutrients).  Ozone responses of 2-5 species are being evaluated in TREGRO for each forest stand modeled in ZELIG (35 total stands).   Hourly ozone and meteorological records for 1993-1995 for ozone monitoring sites in each of the 12 areas are the basis for the TREGRO analyses.  Changes in hourly ozone as a function of SAMI strategies are being provided from the results of SAMI’s air quality modeling. Species-specific responses to ozone from TREGRO are used as inputs to ZELIG.  The projected changes in forest growth and species composition for the 25 stands in 2010 and 2040 will be described for each SAMI strategy and will be interpreted regionally for policy audiences.

 

 

9.         North Carolina

 

Name of the Investigator: H.S. Neufeld

 

Institution: Appalachian State University

 

Period: 01-01-2001 to 12-31-2001

 

Objective: Characterize whole plant responses to O3, including carbon assimilation and allocation, growth and productivity.

 

Progress Report

We measured the responses of these native species (cutleaf coneflower, Rudbeckia laciniata; crownbeard, Verbesina occidentalis; tall milkweed, Asclepias exaltata) to ozone in the summers of 2000 and 2001.  Ozone exposures increased with elevation, and total seasonal exposures were higher in 2000, whereas 2001 was wetter.

 

Injury from ozone depressed both photosynthesis and stomatal conductance.  In coneflower, photosynthesis in the most recently matured leaves was reduced from approximately 12 umol m-2 s-1 in leaves showing no injury to about 2.6 umol m-2 s-1 in leaves showing Class 4 injury ratings (26-50% stipple).  Conductance values were higher in the morning for coneflower and declined during the day, with plants off the trail showing higher conductances than those along the trail.  Additional gas exchange data are currently being analyzed.

 

Light levels declined significantly in the coneflower stands at Clingman’s Dome, reaching less than 1% at the base of the plants, while ozone remained at 40% or more of that above the canopy.  This suggests that uptake patterns and stand structure determine injury extent in these plants.  RAPDs analyses suggests that the plants along the trail at Clingman’s Dome are one clone, while those off the trail constitute a different clone.  At Purchase Knob, genetic variability among symptomatic and asymptomatic plants is much greater, for reasons unknown at present.

 

Tall milkweed had more extracellular ascorbate than the other two species.  In addition, the majority of the extracellular ascorbate was in the reduced form, whereas in the other two species, most of it was already oxidized.  Further work using common gardens at two elevations in the mountains is planned for the coming year.  The results so far suggest that current levels of ozone are harming native plants in the Park.

                                               

Impact

This work is still in progress, but by documenting the impacts of ozone on native wildflowers in the Park, which is also a Class I area, we are providing the necessary information for land managers to make recommendations concerning air quality regulations to protect biological resources.

 

Publications

None

 

 

10.       North Carolina

 

 

Name of the Investigators:  F.L. Booker, K.O. Burkey, A.S. Heagle, J.E. Miller

 

Institution:  USDA-ARS Air Quality Research Unit, Raleigh, NC

 

Period: 01-01-2001 to 12-31-2001

 

Objective:  Characterize whole plant responses to ozone, including carbon assimilation and allocation, growth and productivity.

 

Progress Report

 

A field experiment to determine effects of mixtures of ozone and carbon dioxide on Irish potato was performed in open-top field chambers.  Plants were exposed from emergence to maturity to all combinations of three ozone and three carbon dioxide concentrations.  Carbon dioxide provided less protection of potato from ozone stress than we have previously measured for crops such as soybean, cotton and winter wheat.

 

Effects of elevated carbon dioxide on Western flower thrips were measured on white clover.  Thrips population was not affected by carbon dioxide, but leaf area scarred by thrips feeding was 90% greater at elevated than at ambient carbon dioxide.  Because of increased growth however, undamaged leaf area was approximately 15% greater at elevated than at ambient carbon dioxide.  The results suggest that double ambient carbon dioxide concentrations will be a net benefit for white clover.

 

An experiment using white clover clones confirmed that ozone concentrations in North Carolina are high enough to significantly stress some crop plants.

 

Field experiments indicated that decomposition of soybean leaf residues from plants treated with ozone was 45 to 60% slower than residues from plants grown in charcoal-filtered air. This suggests that ozone exposure could affect carbon sequestration and nutrient cycling in agricultural soils.

 

Leaf extracellular ascorbic acid was compared in ozone-sensitive (S156) and ozone-tolerant (Provider) genotypes of snap bean under field conditions in open-top chambers. Extracellular ascorbic acid was higher in tolerant Provider relative to sensitive S156. The results suggest that ozone tolerance could be enhanced in crop plants by manipulating leaf extracellular ascorbate content so that the apoplastic space contains sufficient antioxidant capacity to neutralize ozone and thus reduce/prevent leaf injury.

 

 

Impact

 

This work is still in its growing stages and therefore, its societal impact, output to target audience and the outcome cannot be gauged as yet. However, it has the potential to verify the regional scale validity of ambient air quality regulations.

 

Publications

 

Booker, F.L. and K.O. Burkey.  2001.  Extracellular RNase in snap bean leaves is stimulated by ozone.  Plant Biology 2001 meeting abstract #458, p.105.

 

Booker, F.L. and K.O. Burkey.  2001.  Stimulation of RNase activity by ozone stress.  European Science Foundation Workshop, Adaptation of plant populations to environmental insult, Newcastle, UK.  July 27-30.

 

Booker, F.L. and K.O. Burkey.  2001.  Leaf extracellular RNase activity is stimulated by ozone.  Southern Section of the ASPP meeting, Raleigh.  March 24-26.

 

Booker, F. L. and C. Maier.  2001.  Atmospheric carbon dioxide, irrigation, and fertilization effects on phenolic and nitrogen concentrations in loblolly pine (Pinus Taeda L.) needles.  Tree Physiology 21:609-616.

 

Fiscus, E.L., F.L. Booker, C.D. Reid and J.E. Miller.  2001.  Unconsidered environmental stresses may cause overestimates of the CO­2-fertilization effect.  PS2001 Proceedings, 12th International Congress on Photosynthesis.  CSIRO Publishing, Collingwood, Australia.  S33-003.

 

Burkey, K.O.  2001.  Leaf extracellular ascorbic acid as a factor in ozone tolerance.  Plant Biology 2001 meeting abstract #456, p. 105.

 

Heagle, A.S., S. Costa, and G.G. Kennedy.  2001.  Effect of host plant ozone stress on Colorado potato beetles. Environmental Entomology 30(5): 824-831.

 

Krupa, S.V., G.T. McGrath, C. P. Andersen, F.L. Booker, K.O. Burkey, A. Chappelka, B. Chevone, E. Pell, and B. Zilinskas.  2001.  Ambient ozone and plant health.  Plant Disease Vol. 85(1): 4-12.

 

 

11.       Virginia

 

Name of the Investigator:  B.I. Chevone

 

Institution:  Virginia Polytechnic Institute and State University

 

Period:  01-01-2001 to 12-31-2001

 

Progress

Maximum net photosynthesis (Pn) and chlorophyll fluorescence were measured in ozone-tolerant and ozone-sensitive black cherry trees at a field site during the summer, 2001.  Ambient hourly ozone (O3) concentrations were low and never exceeded 100 ppb. Visible foliar  injury was present initially in the second week of July, but never exceeded 5% of the leaf surface area. In September at a secondary site, O3 injury ranged from 0 to 5% in youngest leaves to 35 to 45% in oldest leaves.  In June, Pn of tolerant and sensitive trees was similar (about 8.5 umols CO2/m2/s).  However, in September, Pn in sensitive leaves was 53% less than in tolerant leaves, which was similar to the 65% difference in Pn between the two genotypes observed in September, 2000.  Stomatal conductance rates between the two sensitivity groups was similar indicating that CO2 uptake was not involved in altering Pn rates.  By September, ambient O3 concentrations had reduced the electron transport rate through PSII reaction centers by 55% in sensitive leaves compared to tolerant ones.  A highly significant inverse relationship between foliar symptoms and Pn was evident in both 2000 and 2001.  At 45% leaf injury, Pn was reduced by 80% relative to healthy leaves.  Ozone symptoms of only 5.5% inhibited Pn by 10%.  These results demonstrate that low, ambient ozone concentrations can significantly reduce photosynthetic capacity in ozone-sensitive black cherry trees.  Such reductions in Pn should have a negative impact on tree growth.

 

Impact

These results demonstrate that low, ambient O3 concentrations can significantly reduce photosynthesis in a sensitive forest tree species, like black cherry. Such reductions in photosynthesis should have a negative impact on tree growth.

 

Publications

None.