Non-filtered Chambers Research Articles

Yield and kernel nutritional quality in normal maize and quality protein maize cultivars exposed to ozone.

Tropospheric ozone (O3 ) is phytotoxic and therefore impacts global food security. In the present study yield responses and kernel quality traits of two maize cultivars [DHM117: normal maize (NM)] and [HQPM1: quality protein maize (QPM)] are investigated. Cultivars were exposed to two doses of elevated O3 , namely NFC+15 and NFC+30 ppb O3 above ambient level (NFC, non-filtered chambers) while filtered chambers served as control. Test weight (thousand kernel weight), weight of kernels per square meter and kernel starch content reduced more in NM than QPM due to elevated O3 exposure. Total soluble and reducing sugars increased in both the cultivars being more in NM. Though, endosperm protein showed comparatively more increase in QPM than NM, decline in essential amino acids tryptophan and lysine was higher in QPM. Majority of nutrient elements increased after O3 treatment, while reductions in oil content as well as saturated fatty acids were observed in both test cultivars. Of the two essential fatty acids, omega 3 fatty acid reduced while omega 6 fatty acid contents increased in QPM. Oil became more unsaturated (increase in polyunsaturated fatty acids) upon O3 exposure, thus increasing its reactivity and hence became more prone to auto-oxidation. Elevated O3 caused losses in yield of maize cultivars and NM showed higher sensitivity than QPM. Kernel quality analysis revealed significant changes in nutritional parameters. Carbohydrate content reduced more in NM, while essential amino acids and saturated fatty acids showed more decline in QPM. © 2018 Society of Chemical Industry.

Cultivar specific variations in antioxidative defense system, genome and proteome of two tropical rice cultivars against ambient and elevated ozone

For the past few decades continuous increase in the levels of tropospheric ozone (O3) concentrations is posing to be a threat for agricultural productivity. Two high yielding tropical rice cultivars (Malviya dhan 36 and Shivani) were evaluated against different concentrations of O3 under field conditions. Experimental design included filtered chambers, non-filtered chambers having ambient O3 and 10 and 20ppb elevated O3 above the ambient. Study was conducted to assess differential response if any in induction of antioxidative defense system, genome stability, leaf proteome, yield and quality of the product in both the test cultivars. Superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), and glutathione reductase (GR) were induced under ambient and elevated levels of O3. Native polyacrylamide gel electrophoresis (PAGE) of SOD, CAT and POD also displayed increased enzymatic activity along with associated alterations in specific isoforms. Ascorbic acid, thiols and phenolics were also stimulated at ambient and elevated O3. Structural alterations in DNA of rice plants due to O3 affecting its genome template stability (GTS) was examined using RAPD technique. 2-D PAGE revealed 25 differential spots in Malviya dhan 36 and 36 spots in Shivani after O3 treatment with reductions in RuBisCO subunits. Reductions in yield and change in the quality of grains were also noticed.

Genotypic differences in utilization of nutrients in wheat under ambient ozone concentrations: Growth, biomass and yield

The effects of ambient ozone (O3) on wheat (Triticum aestivum L.) varieties HUW 510 and LOK-1 were studied at recommended and 1.5 times recommended NPK under natural field conditions using open top chambers under varying NPK levels. Ambient O3 was filtered out from air through charcoal filters for control plants (FCs), while non-filtered chambers received ambient O3 (NFCs). Twelve hourly mean concentrations of O3 varied from 10.3 to 110ppb. Plants growing in FCs showed better growth performance and higher biomass accumulation compared to those in NFCs at both NPK levels. There were improvements in yield and its quality parameters in FCs compared to NFCs at both NPK levels with no significant difference in yield between FCs and NFCs at 1.5 times recommended NPK in LOK-1 and at RNPK in HUW 510. Nitrogen utilization efficiency increased in NFCs compared to FCs in both the varieties, but lower capability of N acquisition under ambient O3 led to higher magnitude of reduction in yield of LOK-1 compared to HUW 510 at recommended NPK. The results clearly showed that 1.5 times recommended NPK alleviated the negative effects of ambient O3 pollutant in LOK-1 variety whereas recommended NPK in HUW 510.

Assessment of growth and yield losses in two Zea mays L. cultivars (quality protein maize and nonquality protein maize) under projected levels of ozone

Rapid industrialization and economic developments have increased the tropospheric ozone (O3) budget since preindustrial times, and presently, it is supposed to be a major threat to crop productivity. Maize (Zea mays L.), a C4 plant is the third most important staple crop at global level with a great deal of economic importance. The present study was conducted to evaluate the performance of two maize cultivars [HQPM1: quality protein maize (QPM)] and [DHM117: nonquality protein maize (NQPM)] to variable O3 doses. Experimental setup included filtered chambers, nonfiltered chambers (NFC), and two elevated doses of O3 viz. NFC+15 ppb O3 (NFC+15) and NFC+30 ppb O3 (NFC+30). During initial growth period, both QPM and NQPM plants showed hormetic effect that is beneficial due to exposure of low doses of a toxicant (NFC and NFC+15 ppb O3), but at later stages, growth attributes were negatively affected by O3. Growth indices showed the variable pattern of photosynthate translocation under O3 stress. Foliar injury in the form of interveinal chlorosis and reddening of leaves due to increased production of anthocyanin pigments was observed at higher concentrations of O3. One-dimensional gel electrophoresis of leaves taken from NFC+30 showed reductions of major photosynthetic proteins, and differential response was observed between the two test cultivars. Decline in the number of male flowers at elevated O3 doses suggested damaging effect of O3 on reproductive structures which might be a cause of productivity losses. Variable carbon allocation pattern particularly to husk leaves, foliar injury, and damage of photosynthetic proteins led to significant reductions in economic yield at higher O3 doses. PCA showed that both the cultivars responded more or less similarly to O3 stress in their respective groupings of growth and yield parameters, but magnitude of their response was variable. It is further supported by difference in the significance of correlations between variables of yield and AOT40. Cultivar response reflects that QPM performed better than NQPM against elevated O3.

Assessment of the interactive effects of ambient O3 and NPK levels on two tropical mustard varieties (Brassica campestris L.) using open-top chambers

Rising O(3) concentrations in agricultural areas have been identified as a significant threat to crop production in Asia including India. The present work reports the results of a field study conducted to assess the usefulness of higher than recommended NPK dose in modifying the physiological, growth, yield, and seed quality responses of two mustard (Brassica campestris L. var. Vardan and Aashirwad) varieties under ambient ozone level at a rural site of India, using open-top chambers. Twelve hourly mean O(3) concentrations ranged between 27.7 and 59.04 ppb during the growth period. Plants in nonfiltered chambers (NFCs) showed reductions in photosynthetic rate, stomatal conductance, and growth parameters compared to the plants in filtered chambers (FCs), but reductions were of lower magnitude at 1.5 times recommended dose of NPK (1.5 RNPK) compared to recommended (RNPK). Yield and seed quality reduced significantly in plants of NFCs compared to FCs at RNPK, but no significant differences were recorded at 1.5 RNPK. There were higher N uptake and N uptake efficiency of plants in FCs compared to NFCs. Nitrogen utilization efficiency increased in Vardan, but decreased in Aashirwad in NFCs compared to FCs suggesting higher capability of N acquisition and utilization under ambient O(3), which led to a less pronounced reduction in the yield of the former than the latter variety. The differential nitrogen utilization efficiency in these varieties may be potentially used as measure of sensitivity characteristics in breeding programs for yield improvement in mustard under the present trend of increase in O(3) concentrations.

Effects of ambient O<sub>3</sub> on wheat during reproductive development: Gas exchange, photosynthetic pigments, chlorophyll fluorescence, and carbohydrates

The current concentrations of O3 have been shown to cause significant negative effects on crop yield. The present levels of ozone may not induce visible symptoms in most of plants, but can result in substantial losses in reproductive output. This paper considers the impact of ambient O3 on gas exchange, photosynthetic pigments, chlorophyll (Chl) fluorescence and carbohydrate levels in the flag leaf of wheat plants during various stages of reproductive development using open-top chambers. Mean O3 concentration was 45.7 ppb during wheat growth and 50.2 ppb after flag leaf development. Reproductive stage showed higher exceedence of O3 above 40 ppb compared to the vegetative stage. Diurnal variations in net photosynthetic rate (P N) and stomatal conductance (g s), intercellular CO2 concentration (C i), Fv/Fm ratio, photosynthetic pigments, soluble sugars, and starch were measured at 10, 30, and 50 days after flag leaf expansion (DAFE). The results showed reductions in P N, g s, Fv/Fm ratio, photosynthetic pigments and starch, and increases in C i, F0, and soluble sugars in nonfiltered chambers (NFCs) compared to filtered chambers (FCs). Maximum changes in measured parameters were observed at 50 DAFE (i.e. grain filling and setting phase). Diurnal variation in P N showed double peaked curve in both FCs and NFCs, but delayed peak and early depression in NFCs. Stomatal conductance was significantly lower in NFCs. The study suggests that higher prevalence of ambient O3 during reproductive development led to significant alteration in physiological vitality of wheat having potential negative influence on yield.

Urban, traffic- related particles and lung tumors in urethane treated mice

OBJECTIVE:The present study was designed to evaluate the effects of urban, traffic-related, fine particulate matter (PM2.5) on mice lung tumorigenesis under controlled exposure conditions.METHODS:Four groups of female Swiss mice were treated with intraperitonial injections of urethane and saline solution. Urethane was used to start the carcinogenesis process. The animals were housed in two chambers receiving filtered and polluted air. In the polluted air chamber, pollutant levels were low. After two months of exposure, the animals were euthanized and lung tumoral nodules were counted.RESULTS:Saline-treated animals showed no nodules. Urethane-treated animals showed 2.0+2.0 and 4.0+3.0 nodules respectively, in the filtered and non-filtered chambers (p = 0.02), thus showing experimental evidence of increased carcinogenic-induced lung cancer with increasing PM2.5 exposure.CONCLUSION:Our data support the concept that low levels of PM2.5 may increase the risk of developing lung tumors.

Threat to food security under current levels of ground level ozone: A case study for Indian cultivars of rice

A higher ozone concentration in rural agricultural region poses threat to food production in developing countries. The present study was conducted to evaluate the growth, biomass accumulation and allocation pattern, quantitative and qualitative characteristics of grains for two tropical rice cultivars ( Oryza sativa L. cv NDR 97 and Saurabh 950) at ambient O 3 concentrations at a rural site in the Indo Gangetic plains of India. Percent inhibition in number of leaves was higher for NDR 97, but in leaf area for Saurabh 950 grown in non filtered chambers (NFCs) compared to filtered chambers (FCs). Higher inhibition in root biomass was recorded in Saurabh 950 and in leaf and standing dead biomass for NDR 97. During vegetative phase, relative growth rate showed more percent inhibition in Saurabh 950, but at reproductive phase in NDR 97. Net assimilation rate showed higher values for Saurabh 950 than NDR 97 in NFCs but percent inhibition in leaf area ratio was higher for former than latter cultivar in NFCs. The ozone resistance was higher in NDR 97 during vegetative phase, but in Saurabh 950 at reproductive phase. Number of grains was higher in NDR 97 than Saurabh 950, but test weight and weight of grains m −2 showed reverse trends. Concentrations of starch, protein, P, N, Ca, Mg and K decreased, while reducing and total soluble sugar increased in grains of both the cultivars in NFCs compared to FCs. The study concluded that under ambient condition of O 3 exposure, the two cultivars responded differently. Saurabh 950 favoured biomass translocation priority towards ear in reproductive phase and hence showed higher resistivity due to maintenance of higher test weight. NDR 97, however, showed better growth during vegetative period, but could not allocate efficiently to developing ears, hence higher number of unfilled grains in NFCs led lower test weight.

Differences in Ozone Sensitivity at Different NPK Levels of Three Tropical Varieties of Mustard (Brassica campestris L.): Photosynthetic Pigments, Metabolites, and Antioxidants

The effects of ambient O3 at two different levels of nitrogen, phosphorus, and potassium, (recommended and 1.5 times the recommended NPK) on three tropical varieties of mustard (Brassica campestris L. var. Kranti, Aashirwad and Vardan) were explored to unravel the mechanism of protection under higher NPK level at a rural experimental site using open top chambers. Ambient O3 concentrations ranged from 27.7 to 59.04 ppb. Lipid peroxidation, antioxidative enzymes, and metabolites were higher, whereas photosynthetic pigments and protein were lower in all the varieties of mustard grown in non-filtered chambers than in filtered chambers. The magnitude of response varied with varieties, NPK levels and ages. Vardan showed a maximum stimulation in the antioxidative defense system, thus efficient scavenging of ROS produced by O3 and consequently conferred greater tolerance in terms of least reductions in pigments and protein as compared to Kranti and Aashirwad. The antioxidant defense system was not stimulated in response to 1.5 times the recommended NPK, but higher levels of pigments and protein were maintained compared to the recommended NPK under ambient O3 levels.

Evaluation of physiological and biochemical responses of two rice ( Oryza sativa L.) cultivars to ambient air pollution using open top chambers at a rural site in India

Air pollutant concentrations are rising in India, causing potential threats to crop production. As air pollutants are known to interfere with physiological processes, this study was conducted to assess the relative responses of physiological and biochemical characteristics of two cultivars of rice ( Oryza sativa L. cv. Saurabh 950 and NDR 97) leading to variable yield responses. Twelve hour monitoring of ambient concentrations of SO 2, NO 2 and O 3 in filtered chambers (FCs), non-filtered chambers (NFCs) and open plots (OPs) showed that O 3 was the main pollutant at the experimental site. Ozone concentrations often exceeded 40 ppb during anthesis but not during the vegetative growth period. Photosynthetic rate (Ps), stomatal conductance ( g s) and Fv/Fm ratio, superoxide dismutase (SOD) and peroxidase (POD) activities and photosynthetic pigments, ascorbic acid, total phenolics and protein contents were assessed at different developmental stages and yield of grains were quantified. Lipid peroxidation, SOD and POD activities, ascorbic acid and total phenolics were higher, whereas Ps, g s, Fv/Fm ratio and contents of protein and photosynthetic pigment were lower in plants of NFCs as compared to FCs. Yield decreased significantly in both cultivars grown in NFCs. NDR 97 showed less reductions in physiological characteristics, photosynthetic pigments and protein, but a greater increase in the antioxidative defense system as compared to Saurabh 950. Yield reduction was higher in NDR 97 than in Saurabh 950. This suggested that NDR 97 utilized more photosynthate in maintaining the metabolic machinery against O 3 stress leading to lower translocation of photosynthate to reproductive parts. The study concluded that under natural field conditions, physiological and biochemical responses of plants varied with pollutant concentrations leading to different translocation strategies in plants, modifying their yield responses. NDR 97, a fast growing and high yielding cultivar was more sensitive than slow growing Saurabh 950.

Assessment of yield losses in tropical wheat using open top chambers

The present study deals with the evaluation of effects of ambient gaseous air pollution on wheat ( Triticum aestivum L. var. HUW-234) growing in a suburban area situated in eastern Gangetic plain of India, using open top chambers. Eight hourly air monitoring was conducted for ambient concentrations of SO 2, NO 2 and O 3 in filtered chambers (FCs), non-filtered chambers (NFCs) and open plots (OPs). Various morphological, physiological and biochemical parameters were assessed during different developmental stages and finally yield parameters were quantified at the time of harvest. Mean concentrations of SO 2, NO 2 and O 3 were 8.4, 39.9 and 40.1 ppb, respectively during the experiment in NFCs. Concentrations of SO 2, NO 2 and O 3 reduced by 74.6%, 84.7% and 90.4%, respectively in FCs as compared to NFCs. Plants grown in FCs showed higher photosynthetic rate, stomatal conductance, chlorophyll content and Fv/Fm ratio as compared to the plants in NFCs and OPs. Lipid peroxidation, proline, total phenol and ascorbic acid contents and peroxidase activity were higher in plants grown in NFCs. There were improvements in morphological parameters of plants growing in FCs as compared to those in NFCs and OPs. Yield of plants also increased significantly in FCs as compared to those ventilated with ambient air (NFCs) or grown in OPs. During the vegetative phase, NO 2 concentrations were higher than O 3, but O 3 became dominant pollutant during the time of grain setting and filling. The study concludes that O 3 and NO 2 are the main air pollutants in the sub-urban areas causing significant yield reductions in tropical wheat plants.

Seasonal trends in reduced leaf gas exchange and ozone-induced foliar injury in three ozone sensitive woody plant species

Seasonal trends in leaf gas exchange and ozone-induced visible foliar injury were investigated for three ozone sensitive woody plant species. Seedlings of Populus nigra L., Viburnum lantana L., and Fraxinus excelsior L. were grown in charcoal-filtered chambers, non-filtered chambers and open plots. Injury assessments and leaf gas exchange measurements were conducted from June to October during 2002. All species developed typical ozone-induced foliar injury. For plants exposed to non-filtered air as compared to the charcoal-filtered air, mean net photosynthesis was reduced by 25%, 21%, and 18% and mean stomatal conductance was reduced by 25%, 16%, and 8% for P. nigra, V. lantana, and F. excelsior, respectively. The timing and severity of the reductions in leaf gas exchange were species specific and corresponded to the onset of visible foliar injury.

Monitoring Yield Loss from Ozone Pollution in a Mediterranean Environment: A Comparison of Methods

Yield losses from ozone pollution can be estimated by two methods: one involves the use of sensitive (S) and resistant (R) biotypes of white clover (Trifolium repens L., cv. Regal) exposed in ambient air, the other is based on the use of open-top chambers (OTC) supplied either with charcoal-filtered (CF) or non-filtered (NF) air. In southern Italy the two methods have been compared using the clover biotypes. The aim was (1) to compare the extent of ozone-induced yield reductions estimated by the two methods, (2) to evaluate the effect of the chamber enclosure on the growth of both biotypes, and (3) to compare plant water consumption in the different environments. On the average, the yield reduction was 23% when derived from the S/R yield ratio in ambient air, and 18% obtained by the CF/NF yield ratio of the S-type, without a significant difference between the two values. The slightly lower value for the OTC-based system may be due to the lower ozone levels in NF chambers due to losses in the ventilation system. Thus, both methods yielded equivalent yield reductions of about 20% due to ozone at this Mediterranean site. However, the higher air temperature inside OTCs influenced the plant growth, and this effect was stronger in the case of the R type. Therefore, R/S yield ratios in NF chambers differed from ambient air. Also, plant water consumption was higher in OTCs than in ambient air. The results suggest that the OTC-based method enables yield loss estimates at this Mediterranean site, in spite of chamber effects on plant growth and water use.

Variation of gas exchange within native plant species of Switzerland and relationships with ozone injury: an open-top experiment

Gas exchange and ozone-induced foliar injury were intensively measured during a 6-day period in mid-August 1998 on leaves of Acer pseudoplatanus, Betula pendula, Corylus avellana, Fagus sylvatica, Fraxinus excelsior, Morus nigra, Prunus avium, Prunus serotina, Rhamnus cathartica, and Viburnum lantana at a forest nursery site in Canton Ticino, Switzerland. Plants were grown in four open plots (AA), four open-top chambers receiving carbon-filtered (CF) air, and four receiving non-filtered (NF) air. Significant variation in gas exchange ( F>12.7, P<0.001) was detected among species with average net photosynthesis and average stomatal conductance differing by a factor of two. Species also varied significantly in foliar injury for those leaves for which we measured gas exchange ( F=39.6, P<0.001). Fraxinus excelsior, M. nigra, P. avium , P. serotina, R. cathartica, and V. lantana showed more injury than A. pseudoplatanus, B. pendula, C. avellana, and Fagus sylvatica. Plants grown in CF chambers had significantly higher net photosynthesis ( A) and stomatal conductance to water vapor ( g wv), and lower foliar injury than plants grown in NF chambers and AA plots; interactions between species and ozone treatments were significant for all variables ( F⩾2.2, P<0.05) except g wv ( F=0.7, P>0.1). Although A and g wv decreased and foliar injury increased with leaf age, the magnitude of these changes was lower for plants grown in CF chambers than for plants grown in NF chambers and AA plots. Neither ozone uptake threshold ( r=0.26, P>0.20) nor whole-plant injury ( r=−0.15, P>0.41) was significantly correlated with stomatal conductance across these species. It appears that the relationships between stomatal conductance and foliar injury are species-specific and interactions between physiology and environments and leaf biochemical processes must be considered in determining species sensitivity to ambient ozone exposures.

Temporal development of visual ozone injury on the foliage of Prunus serotina—a statistical evaluation

Ozone-induced visible injury to plants is relatively common in North America but has rarely been reported in Europe. The south of Switzerland (canton Ticino) has been identified as having high ambient ozone exposures relative to other parts of Switzerland, with accumulated annual exposures over a threshold of 40 ppb (40 nl O 3 litre −1) for daylight hours from April to September of >30 ppm×h. Ozone-induced foliar injury on black cherry ( Prunus serotina) has been observed in the area. The main purpose of this study was to establish whether seedlings of black cherry grown in three different treatments (open plots [ambient ozone concentrations], chambers receiving non-filtered [96% ambient] air and charcoal-filtered chambers [ca. 60% ambient]) showed significant differences with respect to the various aspects of ozone injury development, particularly trends in injury development, the survival probabilities, the average injury level of a tree and the proportion of trees showing any sign of injury over the summer growing season. Visual estimates of the percentage of leaves showing symptoms (adaxial stipple and leaf reddening) on a plant and the percentage of leaf area of only the injured leaves which showed symptoms of ozone injury were recorded weekly for each seedling for eight consecutive weeks. These two scores were multiplied to derive a measure of injury ( Y) which can be interpreted as the proportion of injured leaf area on a tree. This derived score was used in all subsequent analyses. In this paper we assess whether, overall, an increasing trend in the injury levels, as given by the values of Y, was evident. We have also estimated the probability F( t) that the first sign of injury (measured by Y) might occur after a given number t of weeks. The smaller the value of F( t) for a given t, the stronger the effect of the treatment (i.e. the treatment causes relatively more damage). The average injury level of a tree and the proportion of trees that showed any sign of injury over the 8-week period were also analysed. The results from the open plots, the non-filtered chambers and the charcoal-filtered chambers were significantly different. However, no statistically significant difference was found between the open plots and the non-filtered chambers.

Acetylene reduction rate as a physiological indicator of the response of field-grown soybeans to simulated acid rain and ambient gaseous pollutants

The usefulness of nitrogenase activity as a physiological indicator of whole-plant response to environmental stresses such as gaseous air pollutants or acidic rain was evaluated. The acetylene reduction rate of excised nodules of field-grown soybean plants [ Glycine max (L.) Merr. cv. Davis] was assayed during 2 years of an experiment in which the soybean were exposed in open-top field chambers to simulated rain of pH 3.2, 4.2, or 5.2 in combination with nonfiltered (polluted) or charcoal-filtered air. There was no evidence of an effect of rain chemistry on nitrogenase activity. There was also no statistically significant effect of air filtration on the acetylene reduction rates, although rates were consistently lower in the nonfiltered chambers than in the charcoal-filtered chambers. The large experimental variance, which was partly attributable to sampling constraints, and the evidence for biological compensatory responses suggest that nitrogenase activity may not be a sensitive physiological indicator of stresses induced by acid rain or gaseous pollutants in soybeans.

Cotton Yield Responses to Ozone as Mediated by Soil Moisture and Evapotranspiration

AbstractA 2‐yr field study was conducted to determine injury and yield responses of normally irrigated and water‐stressed cotton (Gossypium hirsutum L.) to a gradient of ozone (O3) concentrations. Cotton (cv. SJ‐2), grown in open‐top chambers in the Central Valley of California, was exposed to six O3 treatments ranging from charcoal‐filtered (CF) to ambient plus 0.10 µL L−1 O3 (1981) or twice ambient O3 concentrations (1982) for the growing seasons of 1981 and 1982. Half the plots were irrigated optimally and the other half were provided with 25% (1981) or 20% (1982) less irrigation water (water‐stressed treatment). During the typically hot, dry growing season of 1981, cotton yield in normally irrigated treatments was reduced 20% by ambient levels of O3 in nonfiltered chambers (NF) relative to CF controls. Doubling ambient O3 concentration reduced yield 45%. Water‐stressed plants showed almost no response to O3. In 1982, the weather was cooler and cloudier than normal and potential evapotranspiration during the growing season averaged 20% less and ambient O3 concentrations averaged 39% lower than in 1981. Under these conditions, cotton yields at both levels of soil moisture treatments responded similarly to O3. Yields in NF chambers were reduced 15% relative to CF chambers. Doubling ambient O3 concentrations reduced yields 65%. The greater relative response of cotton to O3 in 1982 may have resulted from the cooler, more humid growing conditions, which increased the susceptibility of cotton to O3.

The effects of photochemical oxidants on the yield of snap beans

Effects of photochemical oxidants (primarily ozone) in the ambient air of Eastern United States on the yields of selected snap bean ( Phaseolus vulgaris L.) cultivars grown from the seedling stage to maturity in “open-top” field chambers were studied. The chambers were supplied with either carbon-filtered or nonfiltered air. The research was conducted at Beltsville, Maryland, near Washington, D.C. during 1972–1976 and at Raleigh, North Carolina, in 1972. Cultivars Bush Blue Lake (BBL) 290, BBL 274 and Gallatin 50 represented processing type beans and Astro, fresh market beans. Two crops, an early and a late crop, were grown each year. At Beltsville from 1972 to 1974, BBL 290, the most sensitive cultivar to oxidants, averaged 14% less bean yield (range 5–27%) in nonfiltered air than in filtered air. Gallatin 50 and Astro, two oxidant tolerant cultivars, yielded about the same in the two environments. The results were similar in North Carolina. In 1975 yields were greatly reduced due to heavy rains. Consequently, no measurable yield effects attributable to oxidants could be determined. In the late crop in 1976, however, BBL 274 yielded 22% less in the nonfiltered air. The other three cultivars did not exhibit statistically significant oxidant induced yield losses. Yields in ambient air field plots without chambers were essentially equivalent to those in the nonfiltered chambers indicating that chamber effects per se were minimal. The microclimates of the chambers are described in an Appendix.