Effects of air pollutants on the photosynthetic capacity of young Norway spruce trees. Response of single needle age classes during and after different treatments with O3, SO2, or NO2

Summary Potted young Norway spruce trees were exposed to different concentrations of the air pollutants ozone, sulphur dioxide and nitrogen dioxide under completely controlled environmental conditions. After the treatment, the potted trees were kept outdoors. Measurements of the maximum photosynthetic capacity (A₂₅₀₀) were performed with current-year and 1-year-old needles during and after exposure of the trees. In trees fumigated with nitrogen oxides no damage was found at the concentrations used, and the trees' ability to fix carbon dioxide was increased. Using SO₂, a rapid and marked decrease in A₂₅₀₀ was obtained within the first days of the experiment. This decrease did not continue further, but was reversed upon cessation of the fumigation. However, a clear dose-dependent decrease in A₂₅₀₀ occurred when trees were fumigated continuously with an ozone concentration of 450 nl l^–1 or more. The effect of ozone was not reversible, but continued during post-culture of the trees.     

Growth of adult Norway spruce (Picea abies [L.] Karst.) and European beech (Fagus sylvatica L.) under free-air ozone fumigation

This study attempted to detect the impact of ozone on adult trees of Norway spruce ( Picea abies [L.] Karst.) and European beech ( Fagus sylvatica L.) in an experimental mixed stand in Southern Bavaria, Germany. The aim was to examine whether there is a decrease in growth when trees are exposed to higher than atmospheric concentrations of ozone. This exposure was put into effect using a free-air fumigation system at tree crown level. Growth analysis was carried out on a group of 47 spruce and 36 beech trees, where radial stem increment at breast height - a sensitive index for stress - was measured. The ozone monitoring system allowed values to be obtained for the accumulated ozone exposure (SUM00) of each individual tree, so that their radial increment over three years could be correlated with the corresponding ozone exposure for the same time period. Correlation and regression analysis were then carried out to test the influence of ozone on diameter increment. In both spruce and beech, the initial stem diameter was the most influential factor on radial increment in the following year. A linear model was applied, including the diameter of the preceding year and the ozone exposure of the current year as predicting factors. For spruce trees, a significant negative influence of ozone exposure was found. In contrast, no significant ozone effect on diameter increment of beech was detected. The effect of ozone stress on a large spruce tree can lead to a decrease in potential radial increment of 22 %. The results are discussed in relation to other stress factors such as drought and lack of light.     

Association between air pollution and acute childhood wheezy episodes: prospective observational study.

OBJECTIVE--To examine the association between the air pollutants ozone, sulphur dioxide, and nitrogen dioxide and the incidence of acute childhood wheezy episodes. DESIGN--Prospective observational study over one year. SETTING--District general hospital. SUBJECTS--1025 children attending the accident and emergency department with acute wheezy episodes; 4285 children with other conditions as the control group. MAIN OUTCOME MEASURES--Daily incidence of acute wheezy episodes. RESULTS--After seasonal adjustment, day to day variations in daily average concentrations of ozone and sulphur dioxide were found to have significant associations with the incidence of acute wheezy episodes. The strongest association was with ozone, for which a non-linear U shaped relation was seen. In terms of the incidence rate ratio (1 at a mean 24 hour ozone concentration of 40 microg/m3 (SD=19.1)), children were more likely to attend when the concentration was two standard deviations below the mean (incidence rate ratio=3.01; 95% confidence interval 2.17 to 4.18) or two standard deviations above the mean (1.34; 1.09 to 1.66). Sulphur dioxide had a weaker log-linear relation with incidence (1.12; 1.05 to 1.19 for each standard deviation (14.1) increase in sulphur dioxide concentration). Further adjustment for temperature and wind speed did not significantly alter these associations. CONCLUSIONS--Independent of season, temperature, and wind speed, fluctuations in concentrations of atmospheric ozone and sulphur dioxide are strongly associated with patterns of attendance at accident and emergency departments for acute childhood wheezy episodes. A critical ozone concentration seems to exist in the atmosphere above or below which children are more likely to develop symptoms.     

Efficacy of ozone fumigation for laboratory animal sanitation]

Ozone resistance of spores of 2 strains of Bacillus isolated from laboratory animals was examined. Each of 0.02 ml of phosphate-buffered saline at pH 7.0 containing 10(6) Bacillus spores was dropped onto sterilized filter strips, wood chip bedding, pellets of diet, cloth pieces and stainless steel plates. After drying at room temperature, the test materials were exposed to ozone gas of different concentrations at 90% RH. Exposure to 200ppm ozone for 6 hours was sufficient to kill spores in filter strips, but a little higher concentration or a little longer period of ozone fumigation was necessary for sterilization of wood chips, cotton cloth pieces and steel plates. The present results indicated that 600ppm ozone fumigation for 6 hours might be effective for routine sterilization of cages, wood bedding, working clothes and other materials used in laboratory animal facilities. However, exposure to ozone gas of 500 or 1,000 ppm for 6 hours or 200 ppm for 24 hours could not kill spores in pellets of diet, suggesting that dietary protein inhibited the bactericidal activity of ozone.     

Variations in sulphur content and stable sulphur isotope composition of vegetation near a SO2 source at Fox Creek,Alberta, Canada

Summary The proportion of sulphur found in vegetation increases as an industrial sulphur dioxide emission source is approached, but this trend is modified by topographic extremes. Stable sulphur isotope analysis revealed that increased sulphur concentrations in arborcal and terricolous lichens, andPicea glauca needles were due to incorporation of sulphur emitted as sulphur dioxide by the Kaybob sour gas plant near Fox Creek, Alberta, Canada. It is confirmed thatPicea glauca gets its sulphur from both the soil and the air; arboreal lichens get their sulphur primarily from the atmosphere; and terricolous lichens get theirs from the air and particulate fallout. It is suggested that arboreal lichens selectively excrete isotopically light sulphur when thallus concentrations exceed 1,400 ppm. Accumulation of sulphur in vegetation is dependent, on fumigation episode duration, frequency, and concentration, as well as the plant's ability to avoid injury, but is not closely correlated with average sulphation rates. The implications of terrestrial moss-lichen carpet destruction is discussed.     

Effects of ozone and elevated atmospheric carbon dioxide on carbohydrate metabolism of spruce needles. Catabolic and detoxification pathways

We have studied the effects of ozone, carbon dioxide and ozone combined with carbon dioxide fumigations on catabolic and detoxification pathways in spruce ( Picea abies [L.] Karst.) needles. The results obtained showed an increase in the activities of three enzymes involved in the detoxification pathway, superoxide dismutase (SOD, EC 1.15.1.1), ascorbate peroxidase (AscPOD, EC 1.11.1.11) and glutathione reductase (GR, EC 1.6.4.2) when trees were exposed to ozone and to ozone‐carbon dioxide treatments. In these two treatments, the fraction of SOD activity due to the chloroplastic isoform was increased (1.5‐fold). In the needles of trees exposed to ozone and to ozone‐carbon dioxide fumigation, an increase in the activities of glucose‐6‐phosphate dehydrogenase (G‐6‐PDH, EC 1.1.1.49) showed that the cell had the capacity to produce more NADPH necessary for the detoxification. Stimulation of other enzymes of catabolic pathways (fumarase [EC 4.2.1.2], phosphofructokinase [PFK, EC 2.7.1.1] and phosphoenolpyruvate carboxylase [PEPC, EC 4.1.1.31]), was also observed making it possible for the cell to provide the reducing power necessary for detoxification as well as energy and carbon skeletons involved in the repair processes.
When carbon dioxide alone was applied, no effects could be detected on these enzyme activities. However, when carbon dioxide was combined with ozone, the effect of ozone on trees was less than that induced by ozone alone, suggesting that elevated atmospheric carbon dioxide concentrations may to some extent protect plants from ozone injury.     

The effects of SO2 and O3 on the foliar nutrition of Scots pine, Norway spruce and Sitka spruce in the Liphook open-air fumigation experiment

Foliar elements were analysed in Scots pine, Sitka spruce and Norway spruce over a 6 year period before and during continuous exposure to SO₂ and O₃ in an open-air fumigation experiment. Sulphur dioxide treatment elevated foliar sulphur concentration in all species, and there were increases in foliar nitrogen in the two spruce species but not in pine. The concentrations of cations were frequently increased by SO₂ treatment, but there was no correlation between the sulphur concentration of needles and their total cation charge. SO₂-related elevations of foliar magnesium were correlated with the concentration of this element in soil solution, but the mechanism by which other cations were enhanced remains unclear. The only consistent effects on nutrient ratios were for SO₂ treatments to increase sulphur/cation ratios.     

The response of sensitive and tolerant clones of Populus tremuloides to dynamic ozone exposure under controlled environmental conditions

Both sensitive and tolerant clones of aspen ( Populus tremuloides ) were exposed to ozone using four different exposure regimes under controlled environmental conditions. Based on data on ambient ozone from 10 cities in the USA, three treatments of 4-wk exposure to the same SUM06 (an accumulation of hourly O₃ concentrations greater than 0.06 ml l⁻¹) were constructed. The regimes allowed us to investigate: (a) the importance of long (3 wk, treatment 1) versus short (1 wk, treatment 2) duration of regimes with high peaks; (b) the effect of treatments with variable peak occurrence (treatments 1 and 2) versus uniform peak occurrence (treatment 3) during the exposure period. Nonfumigated control plants were maintained at ozone concentrations <10 nl l⁻¹. Bifacial black necrosis, a typical symptom of ozone injury on aspen leaves, occurred on both clones after 2 wk exposure. Up to 60% of the leaves on the sensitive clone were injured, with an average of 6% of total leaf area injured. In the tolerant clone only 10% of the leaves were injured, with less than 1% of the total leaf area symptomatic. The severity of injury was consistently greatest in treatment 2, followed by treatments 1 and 3, respectively. The interval between peak exposures was less important than the occurrence of peaks versus a stable maximum concentration. Premature leaf abscission occurred in the sensitive clone. Measures of gas exchange demonstrated reduced photosynthesis under ozone fumigation, but exposure regime was not a significant factor. Concentrations of two antioxidants, ascorbic acid and glutathione, were almost always greater in the resistant than in the sensitive clone, but the differences were not statistically significant. The levels of these antioxidants in aspen leaves did not change with ozone fumigation or leaf age.     

Evidence that branch cuvettes are reasonable surrogates for estimating O3 effects in entire tree crowns

Within the scope of quantifying ozone (O(3)) effects on forest tree crowns it is still an open question whether cuvette branches of adult trees are reasonable surrogates for O(3) responses of entire tree crowns and whether twigs exhibit autonomy in defense metabolism in addition to carbon autonomy. Therefore, cuvette-enclosed branches of mature beech (Fagus sylvatica) trees were compared with branches exposed to the same and different ozone regimes by a free-air fumigation system under natural stand conditions by means of a VICE VERSA experiment. For this purpose, cuvettes receiving 1 x O(3) air were mounted in trees exposed to 2 x O(3) and cuvettes receiving 2 x O(3) air were mounted in trees exposed to 1 x O (3) in the upper sun crown. At the end of the fumigation period in September 2004, leaves were examined for differences in gas exchange parameters, pigments, antioxidants, carbohydrates, and stable isotope ratios. No significant differences in foliar gas exchange, total carbohydrates, stable isotope ratios, pigment, and antioxidant contents were found as a consequence of cuvette enclosure (cuvette versus free-air branches) of the same O(3) concentrations besides increase of glucose inside the cuvettes and reduction of the de-epoxidation state of the xanthophyll cycle pigments. No significant ozone effect was found for the investigated gas exchange and most biochemical parameters. The total and oxidized glutathione level of the leaves was increased by the 2 x O(3) treatment in the cuvette and the free-air branches, but this effect was significant only for the free-air branches. From these results we conclude that cuvette branches are useful surrogates for examining the response of entire tree crowns to elevated O(3) and that the defence metabolism of twigs seems to be at least partially autonomous.     

Impacts of urban levels of ozone on Pinus halepensis foliage

Between May and September, 1996, seedlings of Pinus halepensis were placed at a site adjacent to an automated air pollution monitoring station within the urban area of Florence. Additional 'control' plants were placed in chambers ventilated with charcoal/Purafil(R)-filtered air. All trees were well watered throughout the whole experimental period. During the exposure period, ambient levels of sulphur dioxide were very low, whilst the accumulated hourly exposure to ozone above 40 ppb (i.e. AOT40) exceeded 20000 ppb h(-1) - peak hourly ozone concentrations rising to levels above 100 ppb. Trees exposed to ambient levels of air pollution exhibited typical symptoms of ozone damage (chlorotic mottle) on previous year needles toward the end of the summer. Similar symptoms were not observed on equivalent trees exposed to filtered-air, nor were visible symptoms accompanied by insect or pest infestation. Anatomical and ultrastructural observations made on symptomatic needles revealed degeneration in mesophyll cells bordering sub-stomatal cavities and alterations in chloroplast ultrastructure (fat accumulation, starch and tannin pattern modifications). These observations are consistent with the known effects of air pollutants (namely ozone) recorded in the literature. Findings are discussed in relation to the impacts of ozone on P. halepensis in the Mediterranean region.     

Effect of long term fumigation with ozone on the turnover of the D-1 reaction center polypetide of photosystem II in spruce (Picea abies)

Long term fumigation of 4-year-old spruce trees with ozone concentrations up to 200 nl l⁻¹ has only minor effects on the photosynthetic activities measured as chlorophyll a fluorescence. Nevertheless, it drastically changes the turnover of the D-1 reaction center polypeptide of photosystem II. During summer, fumigation with ozone for 2 weeks resulted in an almost 4-fold stimulation of the light dependent incorporation of [¹⁴C] leucine into the D-1 protein in the exposed trees. The amount of immunodetectable D-1 protein remained constant when based on chlorophyll. This indicates that exposure to ozone stimulates both the synthesis and the degradation of the D-1 protein. When spruce trees were exposed during winter for 4 weeks to 100 and 200 nl l⁻¹ ozone, respectively, an almost 3-fold increase of the amount of immunodetectable D-1 protein per chlorophyll in the exposed trees was observed. This can be explained by a varying stimulation of D-1 protein synthesis and degradation depending on the different physiological conditions. Since so far the D-1 protein has been found only as a component of photosystem II reaction centers, one has to assume that the relative content of photosystem II reaction centers also increases under certain stress conditions. The increased turnover of the D-1 protein in trees exposed to ozone explains the synergistic effects of stress conditions and high light intensities often observed in the field.     

二氧化硫污染对植物体酶活性的影响

通过用６种浓度的ＳＯ２气体对６种植物进行熏气处理,然后测定植物叶片内的过氧化物酶,抗坏血酸氧化酶及多酚氧化酶的活性,为环境监测提供理论依据。通过试验,发现ＳＯ２气体对植物叶内不同酶的活性的影响有别。６种植物受不同浓度的ＳＯ２污染,叶内的过氧化物酶活性随ＳＯ２浓度增加而增加,促进叶片的衰老;而对其他的２种酶,则６种植物表现不同     

Variable growth and reproduction response of the spruce shoot aphid, Cinara pilicornis, to increasing ozone concentrations

Spruce shoot aphid, Cinara pilicornis Hartig (Homoptera: Lachnidae), is an aphid species that has shown enhanced performance on trees exposed to SO₂ or mixtures of air pollutants, whereas results with ozone have been contradictory. Using a 4-week chamber fumigation experiment, we tested how different population dynamic parameters of aphids are affected by ozone (O₃). Mean relative growth rate (MRGR), development time and reproduction rate of C. pilicornis were determined using 7h day-time O₃ concentrations of 0, 40, 80 and 160 ppb. Development period from birth to reproductive stage was fastest at 80 ppb during early shoot elongation, while reproduction and intrinsic rate of population increase was not significantly affected by ozone concentration. There was a significant negative correlation between ozone concentration and the MRGR of first instar nymphs in the third fumigation week. In feeding test performed on seedlings after fumigation, the MRGR was reduced on shoots which had been exposed to 80 ppb O₃. The results suggest that elevated O₃ concentration during early shoot elongation period may stimulate population development of C. pilicornis, but on maturing shoots, high O₃ concentration has a negative effect on aphid performance. This might be due to accelerated ageing of O₃ exposed shoots.     

Carbon fixation in Pinus halepensis submitted to ozone. Opposite response of ribulose-1,5-bisphosphate carboxylase/oxygenase and phosphoenolpyruvate carboxylase

The effects of ozone exposure on carbon-fixation-related processes in Pinus halepensis Mill. needles were assessed over 3 months under controlled conditions. Ozone fumigation (200 ppb) did not induce a modification of either net CO₂ assimilation or stomatal conductance in 1-year-old needles, whereas ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39) activity was shown to be reduced by a half. Moreover, this ozone-induced reduction in Rubisco activity was associated with a decrease in the quantity of Rubisco, as determined by the decrease in the large subunit (LSU). On the other hand, 200-ppb ozone fumigation induced a strong increase in both activity and quantity of another carboxylating enzyme, phospho enol pyruvate carboxylase (PEPC, EC 4.1.1.31), generally considered in C₃ plants to participate in carbon catabolism processes. Ozone induced a significant decrease in the Rubisco/PEPC activity ratio which promotes the role of PEPC in trees under ozone stress. The role of this carboxylase will be discussed.     

Assessing the impact of ozone on photosynthesis of European beech (Fergus sylvatica L.) in environmental chambers

An exposure — response study with proportionalto-ambient ozone levels was conducted in closed chambers on 3-year-old European beech (Fagus sylvatica L.) of montane origin. The fumigation started in April 1990 and lasted for a single growing season. Climate data and ozone concentrations monitored at an experimental station of the Institute for Applied Plant Biology, Schönenbuch, Switzerland were simulated in the exposure chambers 12 days later (1*O₃). To test exposure-response relations three additional treatments were applied, subambient (0.2*O₃) and two proportionally increased ozone treatments (1.5*O₃ and 2*O₃). The photosynthetic behaviour of the trees in August revealed the light reactions to be less affected than parameters which are related to the dark reactions of photosynthesis. Assimilation (A₃₅₀), apparent carboxylation efficiency (CE), and maximum photosynthetic capacity (A₂₅₀₀) were reduced with increasing ozone concentration. For the ozone response of CE and A₂₅₀₀ Critical Levels were calculated.     

Ozone, air pollution, and respiratory health.

Of the outdoor air pollutants regulated by the Clean Air Act of 1970 (and recently revised in 1990), ozone has been the one pollutant most difficult to control within the federal standards. The known human health effects are all on the respiratory system. At concentrations of ozone which occur during summer air-pollution episodes in many urban metropolitan areas of the United States, a portion of the healthy population is likely to experience symptoms and reversible effects on lung function, particularly if exercising heavily outdoors. More prolonged increase in airway responsiveness and the presence of inflammatory cells and mediators in the airway lining fluid may also result from these naturally occurring exposures. Serial exposures to peak levels of ozone on several consecutive days are more characteristic of pollution episodes in the Northeast United States and may be associated with recurrent symptoms. No "high-risk" or more sensitive group has been found, in contrast to the case of sulfur dioxide, to which asthmatics are more susceptible than normals. The occurrence of multiple exposure episodes within a single year over many years in some areas of California has led to studies looking for chronic effects of ozone exposure on the lung. To date, no conclusive studies have been reported, although further work is under way. Much of what we know about the effects of this gas on the lung are based on controlled exposures to pure gas within an environmental exposure laboratory. Interactions between substances which commonly co-occur in air-pollution episodes are also under investigation.     

Differential expression of CuZn-superoxide dismutases in Pinus sylvestris needles exposed to SO2 and NO2

Mature Pinus sylvestris trees were exposed to air-pollution strees in an open field fumigation experiment. The trees were exposed to low-levels of sulphur dioxide and nitrogen oxides throughout the whole growing season (June to October 1991). Three age-classes (current, one- and two-year-old) of needles were collected from exposed and control trees and the expression of chloroplastic and cytosolic CuZn-superoxide dismutase (SOD; EC 1.15.1.1) genes was studied. The levels of chloroplastic and cytosolic CuZn-SOD mRNA were significantly (up to 2.3-fold) higher in exposed trees for all age-classes of needles as compared to control trees. No significant differences were observed between different needle age-classes in CuZn-SOD mRNA induction. The chloroplastic and cytosolic CuZn-SOD mRNA were induced to the same extent, however, the level of chloroplastic CuZn-SOD mRNA was higher than the cytosolic one. Small differences were observed in CuZn-SOD mRNA levels for individual trees both within exposed and control areas. Protein activity measurements of the CuZn-SOD isozymes did not reveal any significant differences between control and exposed trees. The results are discussed in relation to protection against oxidant stress from air pollutants.     

O3浓度升高对植物活性氧代谢系统影响的研究进展

为了揭示臭氧（O3）浓度升高对植物活性氧代谢系统的影响机理,从代谢生理角度,总结了近年来国内外关于臭氧浓度升高对植物活性氧自由基代谢速率、细胞膜脂过氧化程度、抗氧化系统及生物量和产量影响的研究进展,同时,就臭氧浓度升高与二氧化碳浓度升高的复合作用对植物活性氧代谢系统的影响,及阐明二者相互作用对植物抗氧化系统影响机理的研究进行了综述。在此基础上指出在未来研究中,要在分子水平上进一步深入研究植物活性氧代谢系统对高浓度臭氧、二氧化碳复合作用的响应机理,并应加强高浓度二氧化碳对臭氧胁迫下植物抗氧化系统影响的研究,为解决如何减轻臭氧浓度升高对植物造成的氧化伤害提供基础理论依据。     

Enhanced ozone exposure of European beech (Fagus sylvatica) stimulates nitrogen mobilization from leaf litter and nitrogen accumulation in the soil

Abstract

In a lysimeter study with young beech trees, the effects of elevated ozone concentration on the decomposition and fate of nitrogen in ¹⁵N‐labeled leaf litter were analyzed after one growing season. Nitrogen in the litter was dominated by a relatively inert, residual fraction, but easily decomposable nitrogen was present in substantial amounts. Nitrogen loss was significantly higher at twice‐ambient ozone which was largely attributed to an enhanced mobilization of residual nitrogen. Enhanced mobilization of nitrogen from litter at twice‐ambient ozone exposure resulted in additional ¹⁵N incorporation into the soil down to 30 cm depth. Only 0.41–0.62% of the nitrogen in the litter was incorporated into plant material at both ozone concentrations. Twice‐ambient ozone exposure changed the distribution of the nitrogen taken up from litter inside the beech trees in favor of the shoot, where it may have been used in biosynthetic processes required for defense reactions.     

Analysis of vertical ozone and nitrogen oxides profiles in aPrunus cerasifera canopy

An automatic system was installed for continuous analyses of ozone, sulphur dioxide, nitrogen monoxide and nitrogen dioxide in an experimental orchard with a canopy ofPrunus cerasifera plants in summer 1993. Air samples from three elevations (0.8 m, 1.6 m and 3 m above ground) were sequentially analyzed. Ozone concentrations above the canopy were usually higher than within the canopy; their relationships with stomatal resistance have been investigated. Sulphur dioxide levels were negligible. Nitrogen oxides showed a complex profile, with no particular trend, likely due to a reciprocal exchange between the atmosphere and the ground surface.