Effects of sulphur dioxide, hydrogen fluoride and their combination on three Eucalyptus species

The effects of joint action of SO(2) and HF on three Eucalyptus species were studied by exposing them to combinations of < 13, 122 or 271 microg m(-3) of SO(2) and 0.03, 0.39 or 1.05 microg m(-3) of HF in open top chambers for 120 days. HF and SO(2) reduced the area and weight of immature leaves in all three species, but there were few interactive effects on immature leaves. The response of mature leaves to exposure differed among the species, with the greatest effects on E. calophylla and least effects on E. marginata. The interaction of HF + SO2 had no effect on leaf S concentrations in any of the species, but it reduced leaf F concentrations in E. calophylla and E. gomphocephala. HF increased leaf injury in E. calophylla and E. gomphocephala when simultaneously exposed to 271 microg m(-3) of SO(2), but had no effect at 122 microg m(-3), or on E. marginata. The addition of 271 microg m(-3) of SO(2) increased leaf injury when E. gomphocephala was exposed to 0.39 microg m(-3) of HF and when E. calophylla was exposed to 1.05 microg m(-3) of HF, despite reducing the leaf F concentrations. In some cases the interaction of the pollutants may increase susceptibility to visible injury.     

Improving urban air quality in China: Beijing case study

China is undergoing rapid urbanization because of unprecedented economic growth. As a result, many cities suffer from air pollution. Two-thirds of China's cities have not attained the ambient air quality standards applicable to urban residential areas (Grade II). Particulate matter (PM), rather than sulfur dioxide (SO2), is the major pollutant reflecting the shift from coal burning to mixed source pollution. In 2002, 63.2 and 22.4% of the monitored cities have PM and SO2 concentrations exceeding the Grade II standard, respectively. Nitrogen oxides (NOx) concentration kept a relatively stable level near the Grade II standard in the last decade and had an increasing potential in recent years because of the rapid motorization. In general, the air pollutants emission did not increase as quickly as the economic growth and energy consumption, and air quality in Chinese cities has improved to some extent. Beijing, a typical representative of rapidly developing cities, is an example to illustrate the possible options for urban air pollution control. Beijing's case provides hope that the challenges associated with improving air quality can be met during a period of explosive development and motorization.     

Effects of acidic solutions on element dynamics in the monsoon evergreen broad-leaved forest at Dinghushan,China

BACKGROUND: Soil metal dynamics are affected by acid deposition. Little knowledge is available about the process in the lateritic soils under the monsoon forest in south China. METHODS: Samplings of Acmera acuminatissima, Cryptocarya concinna and Schima superba were grown from October, 2000 to July, 2002 in pots with a natural acid lateritic forest soil from Dinghushan. Pots were watered weekly with an acid solution (pH 3.05, 3.52, 4.00 or 4.40) or with tap water. Fe, Mn, Cu and Al were measured in soils, leachates and sapling leaves. RESULTS: Soil extractable Fe and leachate Al and Mn concentrations increased with a decreasing treatment pH. Soil reactive Al exhibited the opposite trend and decreased over time. The Ca/Al and Mg/ (Al+Mn) ratios did not decrease in the leaves of Schima superba, but decreased with a decreasing treatment pH for Cryptocaria concinna. Both ratios only decreased in the pH 3.05 treatment for Acmena CONCLUSIONS: Cu will not be toxic for plants since soil extractable Cu was not high and Fe will not be toxic either given that its root uptake was inhibited by Mn. Acid rains will lead to increased Mn and Al mobility in soil. Cryptocaria concinna will be the most sensible species to these changes (nutrient deficiency and direct Mn toxicity), while Schima superba should retain a good growth.     

Particulate composition characteristics under different ambient air quality conditions

Particulate compositions including elemental carbon (EC), organic carbon (OC), water-soluble ionic species, and elemental compositions were investigated during the period from 2004 to 2006 in southern Taiwan. The correlation between the pollutant standard index (PSI) of ambient air quality and the various particle compositions was also addressed in this study. PSI revealed a correlation with fine (r = 0.74) and coarse (r = 0.80) particulate matter (PM). PSI manifested a significant correlation with the amount of analyzed ionic species (r approximately 0.80) in coarse and fine particles and a moderate correlation with carbon content (r = 0.63) in fine particles; however, it showed no correlation with elemental content. Although the ambient air quality ranged from good to moderate, the ionic species including chloride (Cl-), nitrate (NO3-), sulfate (SO4(2-)), sodium (Na+), ammonium (NH4+), magnesium (Mg2+), and calcium (Ca2+) increased significantly (1.5-3.7 times for Daliao and 1.8-6.9 times for Tzouying) in coarse PM. For fine particles, NO3-, SO4(2-), NH4+, and potassium (K+) also increased significantly (1.3-2.4 times for Daliao and 2.8-9.6 times for Tzouying) when the air quality went from good to moderate. For meteorological parameters, temperature evidenced a slightly negative correlation with PM concentration and PSI value, which implied a high PM concentration in the low-temperature condition. This reflects the high frequency of PM episodes in winter and spring in southern Taiwan. In addition, the mixing height increase from 980 to 1450 m corresponds to the air quality condition changing from unhealthy to good.     

Effects of air filtration on spring wheat grown in open-top field chambers at a rural site. I. Effects on growth, yield and dry matter partitioning

Spring wheat, Triticum aestivum, was grown in open-top field chambers and exposed during the whole life cycle to filtered and non-filtered ambient air. The relatively low ambient pollution level did affect plant growth but had no effect on the overall grain yield of the two spring wheat cultivars Echo (1987) and Pelican (1988). A reduced root growth was found in both years which could be attributed mainly to the deposition of NO2 and SO2. Effects on crop development most likely due to ozone were limited to the 1987 growing season during which the ambient ozone concentrations were enhanced compared to 1988. This resulted in a slightly increased grain harvest index, a reduced 1000-grain weight, straw yield and a greater reduction in root growth. Visible damage resembling ozone injury appeared both years during seedling growth.     

An open-top chamber study with filtered and non-filtered air to evaluate the effects of air pollutants on crops

Four non-filtered and four charcoal-filtered open-top chambers were employed to determine the effects of ambient levels of gaseous air pollutants at Braunschweig, FRG, on growth and yield of potted plants of winter and spring barley. During the exposure period (November 1985-August 1986) monthly mean values of gaseous air pollutants (microg m(-3)) ranged between 34 and 127 for SO(2), 34 and 52 for NO(2) and 12 and 33 for O(3) in winter (November-March), and 16 to 26 for SO(2), 20 to 33 for NO(2) and 42 to 53 for O(3) in spring-summer (April-August). Monthly 2% percentile values for these gases reached (microg m (-3)) 561 for SO(2), 140 for NO(2) and 170 for O(3). The filtering efficiencies of the charcoal filters used averaged 60% for SO(2), 50% for NO(2) and 70% for O(3). All plants of winter barley from the unchambered plot were killed by severe frost periods in winter, 1986. Little frost damage occurred on plants grown in the chambers. Air filtration resulted in higher numbers of plants of winter barley per pot, i.e. a higher number of individuals per area, and a higher dry weight of whole plants and ears compared to the non-filtered atmosphere. In the experiments with spring barley, fresh and dry weight of whole plants were lower and dry weight of leaves were higher in the filtered open-top chambers. These effects could not be observed at all harvests which were carried out during the growing season. Grain yield and sulphur content of the leaves of both barley cultivars were not affected by the air filtration. Production of biomass of spring barley grown in ambient air was higher than of that grown in open-top chambers.     

The effects of prior exposure to sulphur dioxide and nitrogen dioxide on the water relations of timothy grass (Phleum pratense) under drought conditions

Studies of the growth and water relations of the grass Phleum pratense L. (Timothy) were made after simultaneous exposure to SO(2) and NO(2) at concentrations ranging from 80 + 57.4 microg m(-3) to 240 + 172.2 microg m(-3) (SO(2) + NO(2)). Decreased partitioning to the roots was evident during exposure to the pollutants, but when the plants were returned to clean air restrictions in root growth did not persist. Shoot to root partitioning was, however, complicated by the additional factor of changes in the nutritional status of the soil after additional columns of fresh soil were attached to the original tubes. The rate of use of soil water was nevertheless substantially increased by the pollution treatment and after a period of 23 days in which water was withheld, a clear pollution x water stress interaction was seen. The ability of polluted leaves to conserve water under severe water stress was tested by excising the leaves and measuring their water loss over time. The results from this second experiment showed that conservation of water by the leaves was appreciably affected after exposure to 80 + 57.4 microg m(-3) or 133.3 + 95.6 microg m(-3) SO(2) + NO(2). It seems likely that damage to the cells in the epidermal layer, leading to malfunctioning of stomata, is mainly responsible for the reduced ability to conserve water under conditions of extreme stress.     

Growth and nutrition of Quercus rubra L. seedlings and mature trees after three seasons of ozone exposure

Seedling growth and nutritional status have been shown to be sensitive to ozone, but the influence of multi-season ozone exposure on mature tree growth and nutrition has not been examined. To determine if seedlings and mature trees were similarly affected by ozone exposure, growth and nutrient concentrations in northern red oak (Quercus rubra L.) 4-year-old seedlings and 32-year-old mature trees were examined after treatment with subambient, ambient and twice ambient concentrations of ozone for three growing seasons. SUM00 values summed over the three growing seasons were 147, 255 and 507 ppm-h, respectively, for the subambient, ambient and twice ambient exposures. For mature trees, no influence of ozone treatment on lower stem diameter growth, stem growth within the mid-canopy and foliar biomass was observed. Seedling height was increased by ozone, but biomass and diameter were unaffected. A reduction in the specific leaf weight of leaves in response to ozone coincident with the loss of recurrent flushing was observed in seedlings. Ozone exposure reduced foliar nitrogen concentrations and increased woody tissue nutrient concentrations in seedlings and mature trees at the end of the third growing season. These results suggest an influence of ozone on retranslocation processes in seedlings and mature trees.     

The impact of SO2 and SO2 + ascorbic acid treatments on growth and partitioning of dry matter in Trigonella foenum-graecum L

To study the impact of SO(2) and SO(2) + ascorbic acid on growth and partitioning of dry matter in Trigonella foenum-graecum L., two-week-old plants were exposed to SO(2) for 2 h daily over a 42 day period. One of the exposed sets was treated with ascorbic acid. Plants were grown in a wire house and unexposed plants were used as controls for comparison. The parameters measured, such as dry weights of leaf, stem and root per plant, were found to be lower in the exposed sets than in the controls. The reductions were greater in dry weights of stem and root as compared with weights of leaves, indicating that the partitioning of the dry matter was altered. Greater amounts of soluble sugars and starch in the leaves of exposed plants, compared with the stem, also revealed that translocation was hampered. Reductions were greater in fruiting than in flowering, suggesting that fruit abortion was high. Although ascorbic acid treatment could mitigate the effect of SO(2), the differences were not found to be statistically significant. Significant changes were seen in fruit yield, suggesting that the effect of ascorbic acid is cumulative. The impact of SO(2) and SO(2) + ascorbic acid on partitioning of dry matter to different 'sinks' is discussed.     

SO2-induced growth reductions and sulphur accumulation in wheat

Ten open-top chambers were used to obtain SO(2) concentration-response relationships for growth in wheat cv. Banks, and to study the associated sulphur accumulation. Two-week-old seedlings were exposed to 0.004, 0.042, 0.121, 0.256 or 0.517 microl litre(-1) SO(2) for 79 days, 4 h per day. Response variables measured included height, shoot weight, development stage, tiller number, ear weight per plant, average ear weight, total ear number and shoot sulphur concentration. All growth parameters were significantly negatively affected by SO(2) concentrations above and including 0.042 microl litre(-1). A highly significant positive correlation existed between shoot sulphur concentration and ambient SO(2) concentration.     

Effects of ultraviolet-B radiation (UV-B) on growth and physiology of the dune grassland species Calamagrostis epigeios

Seedlings of Calamagrostis epigeios were exposed to four levels of UV-B radiation (280-320 nm), simulating up to 44% reduction of stratospheric ozone concentration during summertime in The Netherlands, to determine the response of this plant species to UV-B irradiation. After six weeks of UV-B treatment, total biomass of all UV-B treated plants was higher, compared to plants that had received no UV-B radiation. The increase of biomass did not appear to be the result of a stimulation of net photosynthesis. Also, transpiration rate and water use efficiency were not altered by UV-B at any exposure level. Pigment analysis of leaf extracts showed no effect of enhanced UV-B radiation on chlorophyll content and accumulation of UV absorbing pigments. UV-B irradiance, however, did reduce the transmittance of visible light (400-700 nm) of intact attached leaves, suggesting a change in anatomical characteristics of the leaves. Additionally, the importance of including an ambient UV-B treatment in indoor experiments is discussed.     

Effects of photochemical smog and mineral nutrition on ponderosa pine seedlings

Two-year-old seedlings of ponderosa pine (Pinus ponderosa Dougl. ex Laws) were exposed to ambient concentrations of photochemical smog (AA) and clean air (CA) during a single field season at Tanbark Flat of the San Gabriel Mountains in the Los Angeles Basin. The seedlings were grown in a perlite-vermiculite medium with full supply of nutrients (based on modified Hoagland solution); reduced to 50% supply of N; reduced to 50% supply of Mg; and reduced to 50% supply of N+Mg. No significant effects of air pollution exposures on injury development, stem growth and concentrations of plant pigments were determined. The seedlings in the AA treatment had decreased N concentration in current year needles compared with CA seedlings; however, the needle concentrations of other elements did not change. Reduction of N supply in the growing medium caused decreased N, P, Ca, K and chlorophyll a concentrations in needles. Stem growth of the seedlings with reduced N supply was significantly decreased as well. No changes in stem growth or chemical composition of plants with reduced Mg supply were noted. Reduction of supply of nutrients did not change responses of trees to the air pollution exposures.     

Performance of some growth variables

European beech (Fagus sylvatica L.), Norway spruce (Picea abies L. Karst.) and Silver fir (Abies alba Mill.) were exposed to low concentrations of ozone (O(3)) and sulfur dioxide (SO(2)), alone and combined, and simulated acid rain (pH 4.0) in sheltered open-top chambers in Hohenheim (Southwest Germany) for almost five years. The concentrations of O(3) and SO(2) used were related to annual ambient average found in southern West Germany. Two control chambers were ventilated with charcoal filtered air and rainfall was simulated at pH 4.0 and 5.0. Because of large dense plant growth in the chambers it was only possible to measure uncompleted growth of shoots in the upper canopy. Therefore, growth analysis was restricted to this area. The treatment with acidic precipitation decreased the annual shoot growth of beech and reduced leaf surface area of those trees. Exposure to SO(2), O(3) alone and in combination resulted in further reduction of shoot length and leaf surface area. Fumigation with SO(2) and O(3) + SO(2) caused insignificant decreases of shoot length, total dry weight and needle surface area of spruce. The lateral leader shoot growth of spruce exposed to O(3) was significantly reduced only in the last year of the experiment. Growth rates of the spruce exposed to charcoal filtered air and non-acidic precipitation were reduced more than those of beech and fir. Growth variables determined for fir reflected different rates of incremental change. Exposure to O(3) resulted in the largest dry matter production of all fir groups but those exposed to charcoal filtered air and non-acidic precipitation responded with the best lateral leader shoot growth, lowest specific leaf area (SLA) and leaf area ratio (LAR) respectively indicating best metabolic efficiency. At the conclusion of this study a classification of sensitivity was developed for the tree species.     

Simulated Effects of Acidic Solutions on Element Dynamics in Monsoon Evergreen Broad-leaved Forest at Dinghushan,China - Part 1: Dynamics of K,Na, Ca,Mg and P (7 pp)

Background, Aim and Scope Acid deposition has become a concern in south China in recent years. This phenomenon has increased to a dramatic extent with the large use of cars and coal- fueled power plants. As a consequence, soils are becoming acidified and their element dynamics will change. A decrease in the nutrient availability will lead to slower plant growth and maybe to a change in the forest type with current species being replaced by new ones with less nutrient requirements. Because of these reasons, it is important to understand how the dynamics of elements will change and what mechanism is part of the process. This knowledge is important for modeling the acidification process and either finding ways to counter it or to predict its consequences. The primary purpose of this study was to provide information about how the dynamics of K, Na, Ca, Mg and P are affected by acid deposition in a typical forest in southern China. Materials and Methods: Experimental soils and saplings were collected directly from the monsoon evergreen broad-leaved forest in Dinghushan. All saplings were transplanted individually into ceramic pots in August 2000 and placed in an open area near their origin site. Pot soils were treated weekly from October, 2000 to July, 2002 with an acidic solution at pH 3.05, pH 3.52, pH 4.00 or pH 4.40, or with tap water as a control. The concentrations of SO42-, NO3-, K+, Na+, Ca2+, Mg2+ and available P and the pH were measured in soil and leachate samples taken at different times. The sapling leaves were collected and their element concentrations were measured at the end of the experiment. Results: Concentrations of soil exchangeable Ca and Mg decreased quickly over time, although only Ca showed changes with the acidic solution treatment and soil exchangeable K was stable because of soil weathering. Leaching of K, Mg and Ca was dependent upon the treatment acidity. Soil available P decreased slowly without any correlation with the acidity of the treatment. All the NO3- added by the treatment was taken up by the plants, but the SO42- added accumulated in the soil. Discussion: Amongst the plant species, Schima superba was little affected by the treatment, the leaf P content was affected in Acmena acuminatissima plants and Cryptocarya concinna was the most susceptible species to soil acidification, with a marked decrease of the leaf K, Ca and Mg concentrations when the treatment acidity increased. Conclusions: Simulated acid deposition affected the dynamics of K, Ca and Mg in the monsoon evergreen broad-leaved forest. The dynamics of Ca in the soil and of K, Mg and Ca in the soil leachates were affected by the acidic solution treatment. If such a soil acidification occurs, Cryptocarya concinna will be amongst the first affected species, but Schima superba will be able to sustain a good growth and mineral nutrition. Recommendations and Perspectives: Acid deposition will lead to imbalance the nutrient elements in the evergreen broad-leaved forest because of accelerated leaching losses of soil exchangeable Ca and Mg. Measures should be developed to slow down soil acidification or nutrient decrease.     

Effect of carbon dioxide concentration on biomass production and partitioning in Betula pubescens Ehrh. seedlings at different ozone and temperature regimes

Seedlings of Betula pubescens were grown at two CO(2) concentrations, in combination with either two O(3) concentrations or two air temperatures, during 34-35 days at 24 h day(-1) photoperiod in growth chambers placed in a greenhouse. Increasing the CO(2) concentration from 350 to 560 micromol mol(-1) at 17 degrees C air temperature increased the dry weight of the main leaves, main stem, branches and root. The mean relative growth rate (RGR) was increased 10% by CO(2) enrichment, while increasing the O(3) concentration from 7 to 62 nmol mol(-1) decreased the RGR by 9%. The relative biomass distribution between the different plant components was not significantly affected by the CO(2) concentration irrespective of the O(3) concentration. No significant interactions between CO(2) and O(3) concentration were found except on leaf size, which was stimulated more by elevated CO(2) concentration at high, compared to low, O(3) levels. In another experiment, elevated CO(2) (700 micromol mol(-1)) significantly increased the dry weight of the different plant components, and more at 20 degrees C than at 15 degrees C. Raising the CO(2) concentration increased the RGR by 5 and 10% at 15 and 20 degrees C, respectively. CO(2) enrichment increased the branch dry weight relatively more than the dry weight of the other plant parts. Increasing the CO(2) concentration or temperature increased the plant height and stem diameter, however, no interactions between CO(2) and temperature were found.     

Exposure of chronic obstructive pulmonary disease patients to particulate matter: relationships between personal and ambient air concentrations

Mot time-series studies of particulate air pollution and acute health outcomes assess exposure of the study population using fixed-site outdoor measurements. To address the issue of exposure misclassification, we evaluate the relationship between ambient particle concentrations and personal exposures of a population expected to be at risk of particle health effects. Sampling was conducted within the Vancouver metropolitan area during April-September 1998. Sixteen subjects (non-smoking, ages 54-86) with physician-diagnosed chronic obstructive pulmonary disease (COPD) wore personal PM2.5 monitors for seven 24-hr periods, randomly spaced approximately 1.5 weeks apart. Time-activity logs and dwelling characteristics data were also obtained for each subject. Daily 24-hr ambient PM10 and PM2.5 concentrations were measured at five fixed sites spaced throughout the study region. SO4(2-), which is found almost exclusively in the fine particle fraction and which does not have major indoor sources, was measured in all PM2.5 samples as an indicator of accumulation mode particulate matter of ambient origin. The mean personal and ambient PM2.5 concentrations were 18 micrograms/m3 and 11 micrograms/m3, respectively. In analyses relating personal and ambient measurements, ambient concentrations were expressed either as an average of the values obtained from five ambient monitoring sites for each day of personal sampling, or as the concentration obtained at the ambient site closest to each subject's home. The mean personal to ambient concentration ratio of all samples was 1.75 (range = 0.24 to 10.60) for PM2.5, and 0.75 (range = 0.09 to 1.42) for SO4(2-). Regression analyses were conducted for each subject separately and on pooled data. The median correlation (Pearson's r) between personal and average ambient PM2.5 concentrations was 0.48 (range = -0.68 to 0.83). Using SO4(2-) as the exposure metric, the median r between personal and average ambient concentrations was 0.96 (range = 0.66 to 1.0). Use of the closest ambient site did not improve the median correlation of the group for either PM2.5 or SO4(2-). All pooled analyses resulted in lower correlation coefficients than the median correlation coefficient of individual regressions. Personal SO4(2-) was more highly correlated with all ambient measures than PM2.5. Inclusion of time-activity and dwelling characteristics data did not result in a useful predictive regression model for PM2.5 personal exposure, but improved the model fit from simply regressing against ambient concentration (R2 = 0.27). The model for SO4(2-) was predictive (R2 = 0.82), as personal exposures were largely explained by ambient levels. These results indicate a relatively low correlation between personal exposure and ambient PM2.5 that is not improved by assigning exposure to the closest ambient monitor. The correlation between personal exposure and ambient concentration is high, however, when using SO4(2-), an indicator of accumulation mode particulate matter of ambient origin.     

Seasonal aerosol sulfate trends for selected regions of the United States

Site and regional trends in seasonally averaged particle SO4(2-) concentrations were examined for a large portion of the United States using data collected by the CASTNet air monitoring network. Trends were analyzed for overlapping periods of 1988-1999 and 1992-1999. The largest absolute SO4(2-) decreases--approximately -0.4 microg/m3/yr--between 1988 and 1999 occurred in summer for sites in the Ohio River Valley and areas to the east. Generally, the largest SO4(2-) reductions were found for summer, but larger relative reductions often occurred for spring and autumn. Sulfate changes during 1992-1999 were quite different from those found for 1988-1999 and were not entirely consistent with changes in SO2 emissions. In some locations, the 1992-1999 period saw smaller declines in SO4(2-), while in other places seasonal SO4(2-) actually increased. Increases were mostly confined to summer and autumn across the southern and southwestern states. Multivariate analysis of ambient sulfur levels, by region, versus SO2 emissions reveals that annual emissions are associated with more than 80% of the variance in seasonal sulfur (SO2 and SO4(2-)) in more than three-quarters of the cases examined. The weakest associations were found for the southeastern United States.     

Yield responses of different crop species to long-term fumigation with sulphur dioxide in open-top chambers

Potted plants of commercial cultivars of rape (Brassica napus L., cv. 'callypso'), summer barley (Hordeum vulgare L., cvs. 'arena' and 'hockey') and bush beans (Phaseolus vulgaris L., cvs. 'rintintin' and 'rosisty') were continuously exposed in open-top chambers to sulphur dioxide (SO(2)) for the whole growing season in order to assess effects of this pollutant on growth and various yield parameters. Treatments consisted of charcoal-filtered air (CF) and CF supplemented with four levels of SO(2), resulting in mean exposure concentrations (microg m(-3)) of approximately 8, 50, 90, 140 and 190. With the exception of the 1000 seeds weight, which was slightly reduced, dry matter production and yield parameters of rape remained unaffected by all SO(2) concentrations or were even stimulated. Compared to CF vegetative growth of both bean cultivars was reduced by 10-26% at all SO(2) levels; however, with significant effects only for cv. 'rintintin'. While all SO(2) additions reduced significantly the yield (dry weight of pods) of the bean cultivar 'rosisty' between 17% and 32%, cv. 'rintintin' showed a significant reduction of up to 42% only at the two highest pollutant concentrations. Dry matter production of the barley cultivars was mainly impaired at SO(2) concentrations > 100 microg m(-3) with a reduction of 30-52%. While nearly all yield parameters of cv. 'hockey' reacted similar to the dry matter production, the yield of cv. 'arena' was reduced already at the low SO(2) levels. At a treatment concentration of 90 microg SO(2) m(-3) a significant yield loss of 30% was recorded. A reduction of the 1000 grains weight mainly contributed to these yield losses observed for both barley cultivars. From these results, it may be assumed that SO(2) concentrations within the range 50-90 microg m(-3) are potentially phytotoxic to some crop species.     

Physiological and growth responses of differentially irrigated cotton to ozone

This study was conducted to determine the physiological and growth responses of cotton (Gossypium hirsutum L.) to the interaction of ozonee (O3) and drought stress. Cotton (cv SJ-2) was grown in open-top chambers in the field at three levels of soil water and exposed to charcoal-filtered air (CF), nonfiltered air (NF), and NF x 1.25, and NF x 1.5 ambient O3 concentrations in Riverside, CA, from June to October 1986. Ozone reduced carbon fixation an average of 74.6% in optimally watered (OW) plots, 63.4% in suboptimal (SO) plots, but only 19.3% in severely water-stressed (SS) plots. Leaf and stem biomass in OW and SO plots showed similar linear reductions in mass response to increased O3 concentrations, but SS plots showed no response to O3 except at the highest O3 treatment (seasonal 12-h O3 mean of 0.111 ppm 218 microm(-3)). These results showed that moderately water-stressed cotton had similar physiological and growth responses to O3 as well-watered plants, but severely water-stressed cotton showed little response to O3 at ambient O3 concentrations.     

Effects of elevated CO2 nitrogen supply and tropospheric ozone on spring wheat. I. Growth and yield

Spring wheat (Triticum aestivum L. cv. Minaret) was exposed to three CO(2) levels, in combination with two nitrogen fertilizer levels and two levels of tropospheric ozone, from sowing to ripening in open-top chambers. Three additional nitrogen fertilizer treatments were carried out at the lowest and the highest CO(2) level, respectively. Plants were harvested at growth stages 31, 65 and 93 and separated into up to eight fractions to gain information about biomass partitioning. CO(2) enrichment (263 microl litre(-1) above ambient levels) drastically increased biomass of organs serving as long-term carbohydrate pools. Peduncle weight increased by 92%, stem weight by 73% and flag leaf sheath weight by 59% at growth stage 65. Average increase in shoot biomass due to CO(2) enrichment amounted to 51% at growth stage 65 and 36% at final harvest. Average yield increase was 34%. Elevated nitrogen application was most effective on biomass of green tissues. Yield was increased by 30% when nitrogen application was increased from 150 to 270 kg N ha(-1). Significant interactions were observed between CO(2) enrichment and nitrogen application. Yield increase due to CO(2) ranged from 23% at 120 kg N to 47% at 330 kg N. Triticum aestivum cv. Minaret was not very responsive to ozone at 1.5 times ambient levels. 1000 grain weight was slightly decreased, which was compensated by an increased number of grains.