Ozone and drought stress — Interactive effects on the growth and physiology of Norway spruce (Picea abies (L.) Karst.)

Young trees of Norway spruce (Picea abies (L.) Karst.) were grown in 120 litre pots under two different ozone levels in open-top chambers for three seasons, 1992–1994. The ozone treatments were charcoal filtered air (CF, average 24 h seasonal mean 6.5 ppb) and non-filtered air with extra ozone aiming to track 1.5 times ambient (NF+, average seasonal mean 34 ppb). In addition, half of the spruce trees in Aug – Sep each season recieved a drought period of between five and seven weeks. The remaining half were kept well-watered. The soil water content, the needle water potentials, and the gas exchange as well as the chamber micro climate were measured before, during and after the drought period. Furthermore, the growth of the trees was measured as biomass increase. During the 1993 drought period, where the trees experienced a moderate drought stress, the trees grown in NF+ consumed soil water faster and showed a higher needle conductance compared to CF. However, no negative effects were found on needle water potential or growth. During the more severe 1994 drought stress period we did not find any differences between the two ozone treatments in soil water consumption, needle conductance or needle water potential. There was a significant negative effect of the high ozone treatment on tree biomass of the well-watered trees. Total plant biomass was reduced 18 % and stem biomass was reduced as much as 28 %. The negative effect of ozone on tree biomass was much smaller for the droughted trees.     

Long-term effects of ozone on Fagus sylvatica L. — An open-top chamber exposure study

The Landesumweltamt North-Rhine Westfalia is operating eight open-top chambers as well as six reference plots at a site on a westerly exposed slope (540 m a.s.) in the Egge mountains, 130 km northeast of the Ruhr area. Since 1991 eighteen 6 yr old beech trees (Fagus sylvatica L.) per plot/chamber were exposed either to ambient air (AA), non-filtered air (NF) or charcoal-filtered air. Ambient air pollutants (O3. SO2, NOx) as well as meteorological parameters were monitored continuously inside chambers as well as in the ambient. Growth parameters (bud development, stem diameter, shoot length, shoot diameter, leaf area, leaf colouration, leaf abscission) were assessed over the years 1992–1994.Even in the first year a marked earlier colouration of the leaves was observed in the NF (AOT 40=16.2 ppm·hr) versus the CF treatment (AOT 40=0.2 ppm·hr) and leaf abscission was two weeks earlier on NF-trees, indicating the common ozone effect of early senescence. Effects became more pronounced with increasing time of exposure. While hardly any effects on growth could be seen during the first and second year, shoot length and shoot diameter were reduced significantly by about 15 % in NF versus CF treatments in 1994. Similar effects were seen for the leaf area. No effects could be shown for bud development or stem diameter. Ozone specific symptoms were observed on individual trees in the NF and AA treatments and especially pronounced in 1994 (AOT 40=24.1 ppm·hr), but also to a much lesser extent in the CF-treatment. AOT40 value of 10 ppm·h, proposed as provisional standard for the protection of trees by UN-ECE seems to be stringent enough according to the results of this exposure study.     

地表臭氧浓度增加对南京地区冬小麦生长和产量的影响

利用改进后的开顶式气室（OTC）,开展了O3浓度增加对冬小麦生长与产量影响的大田实验研究。实验设置三种处理：CK为未经处理的空气,CF100处理O3浓度为100nL／L,CF150处理O3浓度为150nL／L。结果表明,地表O3浓度增加,冬小麦生育期缩短,籽粒的灌浆期缩短,植株提前老化;同时,冬小麦的株高、生物量、叶面积等生长指标均显著下降（P〈0．05）,最大降幅分别达到了10．01％、36．56％和29．17％;冬小麦的穗数、穗粒数、单位面积产量等产量指标也都出现了显著下降（P〈0．05）,其中CF100、CF150处理的单位面积产量分别比CK下降了16．11％和39．17％。试验结果对于评估地表O3浓度增加对粮食安全的影响具有重要的指导意义。     

Phenolic Pattern of Bean (Phaseolus vulgaris L.) as an Indicator of Chronic Ozone Stress

From sowing till emergence of the fourth trifoliolate leaf, beans were exposed for seven hr a day to four ozone concentrations in open-top chambers: filtered air (FA), non-filtered air (NF), non-filtered air plus 30 ppb ozone (NF+) and non-filtered air plus 60 ppb ozone (NF++). Controls in ambient air of open plots (AA) were also available. The free polyphenolic pool of the first trifoliolate leaf was systematically investigated using HPLC. The groups of phenolics to which the three main chromatographic signals belonged were identified as hydroxycinnamic acid derivative for peak No 1 and flavonoids for peaks Nos 4 and 6. The metabolic regulation of phenolic accumulation could be recognized as different clusters based on specific phenolic patterns that reflected some of the tested atmospheric conditions. The comparison of AA and NF conditions revealed a ‘chamber effect’. FA and NF atmospheres gave rise to almost the same phenolic equilibriums dominated by a hydroxycinnamic acid derivative (about 53% of the total phenolics). Ozone addition was associated with a regular reduction of the percentage of peak No 1: about 40% for NF+ and 19% for NF++. Therefore, the significant decrease of the vacuolar storage of this phenolic compound (from 23 mg g^-1 dry weight for NF to about 3 mg g^-1 dry weight for NF++) can be regarded as a useful tool for monitoring long-term exposure to elevated ozone concentrations.     

臭氧对水稻生长的影响及外源抗坏血酸的防护作用

利用开顶式气室研究了臭氧浓度升高对水稻（Oraza sativa L.）生长的影响及外源抗坏血酸（Exogenous Ascorbic Acid）的防护作用。臭氧处理共设4个水平：空气NF（No-Filter,臭氧浓度约20-50 nL·L^-1）、过滤CF（Charcoal-Filter,臭氧浓度约为5-15 nL·L^-1）、臭氧Ⅰ（8 h平均100 nL·L^-1）、臭氧Ⅱ（8 h平均200 nL·L^-1）,外源抗坏血酸浓度设置为0.1％（m/V）。结果表明,与NF处理相比,高浓度O3（200 nL·L^-1）处理会造成水稻叶片的叶绿素a、水稻的株高、叶面积、穗粒数及粒重,分别下降了47.9％、17. 8％、31.6％、45.7％和42.9％;喷施外源抗坏血酸后,与各自的对照相比,以上各生长指标分别上升了11.6％、7.7％、17.4％、5.6%、11.1%。可见外源抗坏血酸能有效缓解O3对水稻的胁迫作用,提高了水稻对O3的抗性,促进水稻的生长。     

臭氧胁迫对水稻光合作用与产量的影响

采用开顶式气室（OTC）,对水稻“3694繁”（Oryza sativa L.3694 Fan）进行田间原位臭氧（O3）熏气实验,研究了不同O3浓度熏气处理下水稻光合色素、气体交换参数以及产量的响应。实验设置分4个水平：过滤大气组（CF,10 nL.L^-1）、自然大气组（NF,40nL.L^-1）和两个不同浓度的O3处理组（O1：100 nL.L^-1;O2：150 nL.L^-1）。结果表明：（1）与CF组相比,两个不同浓度的O3处理均导致水稻叶片光合色素含量大幅度下降,加速水稻的衰老过程;（2）在实验进程中,O3处理导致水稻叶片气体交换参数发生显著变化,饱和CO2浓度的净光合速率（Psa）t、气孔导度（Gs）、水分利用效率（WUE）、气孔限制值（Ls）和羧化效率（CE）均呈现下降趋势,表明O3浓度的升高使水稻光合作用对CO2的利用效率降低,水稻在灌浆期对O3最为敏感;（3）O3处理使水稻产量损失明显,当AOT40值达到2.32μL.L^-1h时,就能导致水稻产量10%的减产。     

Plant production, and carbon and nitrogen source pools, are strongly intensified by experimental warming in alpine ecosystems in the Qinghai-Tibet Plateau

The aim of this study was to assess initial effects of warming on the nutrient pools of carbon and nitrogen of two most widespread ecosystem types, swamp meadow and alpine meadow, in the Qinghai-Tibet Plateau, China. The temperature of the air and upper-soil layer was passively increased using open-top chambers (OTCs) with two different temperature elevations. We analyzed air and soil temperature, soil moisture, biomass, microbial biomass, and nutrient dynamics after 2 years of warming. The use of OTCs clearly raised temperature and decreased soil moisture. The aboveground plant and root biomass increased in all OTCs in two meadows. A small temperature increase in OTCs resulted in swamp meadow acting as a net carbon sink and alpine meadow as a net source, and further warming intensified this processes, at least in a short term. On balance, the alpine ecosystems in the Fenghuoshan region acted as a carbon source.     

水稻气孔臭氧通量拟合及通量与产量关系的比较分析

利用田间原位开顶式熏气装置（Open-Top Chambers,OTCs）,研究了5种不同浓度臭氧（O3）处理下（自然大气处理,AA;箱内大气处理,NF;箱内低浓度O3处理,NF＋30nL·L-1;箱内中等浓度O3处理,NF＋60nL·L-1;箱内高浓度O3处理,NF＋90nL·L-1）我国珠三角地区水稻产量损失与累积气孔O3通量（AFstX）和累积O3浓度（AOT40和SUM06）的关系,同时利用边界线拟合法,分析了不同环境因子作用下水稻剑叶气孔导度的变化特征。结果表明：水稻气孔运动的光饱和点和最适温度分别约为500μmol·m-2·s-1和33.1℃,水汽压差、物候期和O3暴露剂量的气孔限制临界值分别约为1.3kPa、500℃·d和5μL·L-1·h,高于此临界值时,气孔导度会明显下降。利用Jarvis气孔导度模型对水稻剑叶气孔导度和气孔O3吸收通量进行了预测,结果表明Jarvis模型解释了水稻实测气孔导度61%的变异性。O3吸收速率临界值（X）为2nmol·m-2·s-1时,累积气孔O3吸收量（AFst2）与水稻产量的相关性最高（R2=0.63）,明显高于O3浓度指标（AOT40和SUM06）与水稻产量的相关性（R2值分别为0.49和0.51）,表明基于气孔通量的O3风险评价指标能更好地反映水稻产量的变化。     

Mediterranean natural forest living at elevated carbon dioxide: soil biological properties and plant biomass growth

Abstract. Biomass productivity and soil microbial responses to long-term CO₂ enrichment have been investigated in a Mediterranean natural forest ecosystem. Several biochemical parameters have been measured on soil samples taken from six open top chambers (OTCs), enclosing clumps of natural Mediterranean woody vegetation including: Quercus ilex L., Phillyrea angustifolia L., Pistacia lentiscus L. and Myrtus communis L. The CO₂ concentration of the air inside the OTCs was either ambient or ambient plus 350 μmol mol^–1 ( c . 710 ppm as mean daily value). Microbial C biomass, microbial respiration, dehydrogenase, β-glucosidase, acid phosphatase and protease activities, inorganic N and soluble P, were tested in order to evaluate soil microbial size and activity. Statistically correlated seasonal patterns have been identified in some biochemical parameters in response to climatic conditions, soil nutritional status and the physiology of the vegetative cover. In situ soil respiration and above- and below-ground productivity were also measured. Microbial responses to CO₂ enrichment were observed only at the beginning of the study and a general progressive reduction of the CO₂ effect was recorded as monitoring continued. These results are in agreement with data from literature regarding similar studies on natural complex communities.     

The Promoter of the Tnt1A Retrotransposon: A Biomarker to Monitor Ozone but not Formaldehyde and Benzene Pollution

Open top chambers (OTCs) are useful tools to assess the impact of atmospheric pollutants on plants in the natural environment. We have previously reported that, in tomato plants, the LTR-GUS construct derived from the Tnt1A promoter of tobacco was activated by a realistic level of ozone pollution. In this study, we used OTCs to fumigate tomato plants with benzene or formaldehyde in order to assess the impact of these pollutants on plant growth and development and evaluate the usefulness of the LTR-GUS construct as a biomarker in plants. Whereas the LTR-GUS construct could be used as an efficient biomarker of realistic levels of ozone pollution, it is to a lesser extent applicable to formaldehyde. Indeed, only unrealistic concentration of pollutant activated the construct though important injuries were observed at a lower concentration. For benzene, no activation could be demonstrated, however, we did not notice any visual impact on plant growth and health for this pollutant.     

Results from the UN/ECE ICP-Crops indicate the extent of exceedance of the critical levels of ozone in Europe

The experiments of the United Nations/Economic Commission for Europe (UN/ECE) International Cooperative Programme on effects of air pollution and other stresses on crops and non-wood plants (ICP-Crops) are designed to investigate the effects of ambient ozone pollution on crops and non-wood plants. Each year, participants from approximately 17 European countries conduct a series of coordinated experiments to determine which species develop visible injury following ozone episodes and whether the biomass or yield of sensitive species is reduced. In 1993, ozone injury was only seen at two thirds of sites but in 1994 injury was detected at almost all sites. This coincides with generally higher ozone concentrations measured in that year. Injury was seen on crops including subterranean clover (Trifolium subterraneum L.), white clover (Trifolium repens L.), bean (Phaseolus vulgaris L.), tomato (Lycopersicon esculentum), soybean (Glycine max), watermelon (Citrullus lanatus) and tobacco (Nicotiana tabacum L.) at experimental sites and in some cases, in commercial fields. The application of ethylenediurea (EDU) to some crop species reduced the level of visible injury. At some sites, the yield of EDU-treated bean plants was greater than that of untreated plants where the critical level of ozone for yield reduction was exceeded. Preliminary analysis of ozone concentrations in the days preceding injury indicated a sequential ozone concentration effect. The results are discussed in relation to Level I and Level II mapping of exceedance of the short- and long-term critical levels for ozone.     

The Relative Sensitivity of Different Mediterranean Plant Species to Ozone Exposure

An experimental study was performed in open-top chambers to assess the relative O₃-sensitivity of the following Mediterranean woody plants: Quercus ilex ssp. ilex, Quercus ilex ssp. ballota, Olea europaea ssp. sylvestris, Ceratonia siliqua and Arbutus unedo. Assessment of O₃ ‘sensitivity’ was based on the development of O₃-induced visible injury and the extent of the reduction in relative growth rate induced by O₃. Two-year-old seedlings were exposed in open-top chambers to charcoal filtered air (CFA), Non-filtered air (NFA) or Non-filtered air supplied with 40 ppb O₃ from 09:00 to 18:00 hours (NFA+40). No clear relationships were found between the development of visible injury and effects on plant growth or accumulated biomass. Olea europea ssp. sylvestris and Quercus ilex ssp. ballota appeared to be the most O₃-sensitive tree species screened; a ten month exposure to ambient O₃ levels (AOT40 = 12.4 ppm.h) caused reductions in height and/or stem growth. Further research is needed to characterise the physiological, biochemical and anatomical characteristics that may underlie the ‘sensitivity’ of certain Mediterranean species to O₃     

Improved recovery of fluoride in plant material using a low temperature sealed chamber digestion technique in conjunction with a fluoride ion‐specific electrode

Abstract

Seven different sample preparation methods (five ashing and fusion methods, an acid digestion method, an oxygen flask combustion method) and the AOAC extraction method (975.04) were compared with a newly developed sealed chamber digestion method for the determination of fluoride (F) in vegetation. Subterranean clover tissue was the test material. Fluoride concentration in digests was measured using a F ion‐selective electrode. The sealed chamber digestion carried out with nitric acid in Teflon chambers at 120°C for 6 hours gave the highest F concentration in the plant material and the highest recovery of added F of all methods. Tests on several types of plant material confirmed the superiority of the closed chamber digestion. The superiority of the method is attributed to the complete solubilisation of F in the sample and elimination of losses of volatile F.     

Oxidant effects on forest tree seedling growth in the Appalachian mountains

Long range transport of episodic concentrations of O₃ into the Appalachian Mountains of Virginia was recorded in the summer season of 1979 and 1980. Continuous monitoring of O₃ indicated monthly averages of ? 0.05 ppm O₃ and several periods averaged ? 0.08 ppm O₃. Open-top chambers were used to test the effect of ambient doses of the pollutant on the growth of 8 planted forest tree species native to the area. Height growth was suppressed for all species at the end of the second growing season when grown in open plots (no chamber) and ambient chambers compared to those grown in charcoal-filtered air supplied chambers. Height growth trends of open < ambient chamber < filtered air chamber were consistent. Virginia pine and green ash were significantly taller (p=0.10) when grown within filtered air chambers. Tulip poplar and green ash manifested purple stippling on the adaxial leaf surface and sweetgum developed purple coloration under open or ambient chamber conditions; other species exhibited no visible injury.     

地表臭氧含量增加和UV-B辐射增强对大豆生物量和产量的影响

利用开顶式气室(OTC)设置4个处理对大豆进行O3与UV-B增强的大田试验,通过观测生物量和产量研究两者对大豆生长的影响。T1为O3含量100nmol/mol的处理,T2为UV-B辐射强度比CK增加10%的处理,T3为T1和T2的复合处理,CK为自然空气。结果表明,O3含量与UV-B辐射增强的单因素对大豆株高、叶面积、茎干重等生物量都有不同程度的负影响,而两者复合后对各生物量的影响效果不一致,在分枝期至结荚期拮抗作用居多,而协同作用则多出现在生育期末期。在整个生育期,各处理均表现为茎分配指数变化幅度较小,CK、T1、T2、T3的根和叶分配指数逐渐降低,且荚分配指数呈快速上升的趋势。由此可见,O3和UV-B辐射单因子胁迫对大豆生物量和产量均产生不同程度的负效应,而两者的复合作用并不是两个单独作用的简单累加。     

Impact of Ambient Air Pollution on Locally Grown Rice Cultivars (Oryza Sativa L.) in Malaysia

This study presents the first experimental evidence of the sensitivity of rice plants to ambient air pollution from the Southeast Asian tropical region. Two widely adopted local cultivars of rice (Oryza sativa L.), MR84 and MR185, were grown in open top chambers ventilated with charcoal-filtered air and non filtered air, and in adjacent open plots on the campus of University Putra Malaysia. This is located on the south side of the Klang Valley, a rapidly developing area embracing Kuala Lumpur and other satellite cities, but where agriculture remains important The experimental period was from October 2000 to January 2001, corresponding to the main rice growing season in peninsular Malaysia. Adverse impacts on rice growth and yield were observed and were attributed to phytotoxic levels of ambient ozone. There was a clear difference in the sensitivity of the two selected cultivars. A yield reduction of 6.3% was observed for cultivar MR185 (p < 0.01) which was largely due to an increase in grain sterility, whilst the yield reduction for cultivar MR84 was not statistically significant. The reasons for these differing responses are discussed, and a comparison of the present findings with crop responses to ozone found under European conditions suggests a higher sensitivity in our study crops. With increasing industrialisation and urbanisation, this study highlights the need for further examination of the sensitivity of a wider range of crops and cultivars to ambient air pollution in this region, and also points to the potential for appropriate cultivar selection to ameliorate impacts.     

Critical levels of O3 for wood production of European beech (Fagus sylvatica L.)

During recent decades, ozone (O₃) has gained much attention as a possible contributor to forest decline. Attempts have been made to set critical levels for O₃ in order to protect vegetation. Damage to vegetation seems to depend on the pattern of exposure. Episodic peaks followed by periods with low concentrations are more phytotoxic than exposures with generally elevated concentrations but without peaks. The present experiment aims to examine whether O₃ affects the wood production of beech seedlings. The seedlings were exposed to three different air pollution regimes: charcoal-filtered ambient air (CF), non-filtered ambient air (NF), and NF+30nl^1?l^?1 O₃ 8 hours day¹ during summer periods (NFO). Basal stem diameter was measured regularly during three growing seasons. The relative diameter increase was significantly reduced with increased O₃ concentration. AOT40 is calculated for all treatments and evaluated in relation to the relative diameter growth.     

Ozone sensitivity of Phaseolus vulgaris in relation to cultivar differences,growth stage and growing conditions

Exposure of Phaseolus vulgaris cv. Lit to ambient ozone caused a 14% pod yield reduction in 1994. This yield loss was assessed by comparing plants that were protected against ozone by treatment with EDU (ethylenediurea) with unprotected plants, both cultivated in pots with a continuous water supply. The plants had experienced an AOT40 of 8135 ppb.h during their growth. However, plant response to ozone depends on a large number of environmental and plant-specific conditions. Visible injury increased mainly after flowering and was much less severe on soil-grown bean cultivars (Lit, Stella and Groffy) not receiving additional water. Ozone fumigations in closed chambers before or after flowering proved that the growth stage during which the plants are exposed also plays a very important role with regard to injury development. Plants seem to be more susceptible during the generative growth stage and the relative cultivar sensitivity was related to the developmental stage during fumigation. However with regard to yield effects the timing of the ozone exposure seems to be less important.     

Impacts of Ambient Ozone and/or Acid Mist on the Growth of 14 Tree Species: An Open-Top Chamber Study Conducted in Japan

Young trees of 14 species were exposed to ambient ozone (O₃), (charcoal-filtered air [CF] or non-filtered air [NF]) and/or acid mist (pH 5 or 3: SO₄ ^2?, NO₃ ^?, Cl^? at equivalent 1:2:1 ratio) over three seasons (from June 1993 to November 1995) using tunnel-type open-top chambers at two sites (Abiko: 25 m a.s.l. and Akagi: 540 m a.s.l.) in Japan. Ambient, 12-hr (0600–1800) mean O₃ concentration for April–September during the period of experiment at Akagi (41 ppb) was 40 % higher than that at Abiko (30 ppb). The NF- and CF-chambers had 90 % and 30 % of ambient O₃, respectively. Significant decreases in biomass in the NF treatments were observed in Pinus densiflora, Larix k aempferi, Picea abies, Abies firma, Abies homolepis, Abies veitchii, Cryptomeria japonica, Populus maximowiczii, Betula platyphylla, Fagus crenata and Zelkova serrata as compared with the CF treatment. These results indicate that the current ambient level of O₃ in Japan is high enough to have adverse effects on the growth of all tree species examined, except Pinus thunbergii, Chamaecyparis obtusa and Quercus mongolica. Increasing acidity of mist caused no growth decreases in all tree species examined. However, the growth decreases by O₃ were greater at pH 3 mist treatment than at pH 5 mist treatment on Abies veitchii and Fagus. This suggested that the O₃ effect on tree growth can be exacerbated by the deposition of acid mist, possibly associated with nitrate.     

Clover Sweden — A national three-year study of the effects of tropospheric ozone on Trifolium subterraneum,L.

In 1992 a cooperative project, Clover Sweden, was initiated. The aim was to study if subterranean clover could be used as a bioindicator in the different climate zones in Sweden by studying the impact of ambient ozone concentrations on this species in different parts of the country during three consecutive summer seasons. Plants of subterranean clover, Trifolium subterraneum, L., were exposed to ambient air at 24 sites from north to south Sweden. The project was designed to be compatible with the international programme, ICP Crops within the UNECE and the Convention on Long Range Transboundary Air Pollution. The results showed that subterranean clover is a useful bioindicator of ozone in all agricultural areas of Sweden, with the exception for very cool and rainy summers resulting in poor growth of the plants. In 1992, and especially in 1994, ozone injury was detected at almost all sites in Sweden, reflecting the higher ozone levels of those summers as compared to 1993, when ozone concentrations were generally low and not much injury was detected. Typical injury was chlorotic and bifacial necrotic lesions on parts of the leaf surface. It is concluded that at mean ozone concentrations of 25 ppb (24 h mean) and 30 ppb (7 h mean) there is a potential risk for injury on 10% of the leaves. When % injured leaves was plotted against AOT (Accumulated exposure Over a Threshold) using different thresholds, it became obvious that a threshold of 20 ppb ozone should be used in order to fully protect from leaf injury under Swedish conditions.