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1.
Intraspecific variation in six cultivars of clover Trifolium alexandrinum L., (Bundel, Wardan, JHB-146, Saidi, Fahli, and Mescavi) has been studied with ambient and elevated O 3 (ambient?+?10 ppb O 3) in open top chambers. Significant effect of elevated O 3 was detected on different morphological, physiological, and biochemical parameters depicting differential response among the test cultivars. Results showed that the magnitude of O 3 induced foliar injury symptoms varied in all the cultivars. Ozone significantly depressed photosynthetic rate, stomatal conductance, and photosynthetic efficiency, although variations were cultivar specific. Ozone treatment diminished total biomass of all the cultivars; reduction was highest in Wardan with least O 3 resistance followed by Bundel, JHB-146, Saidi, Mescavi, and Fahli. According to the cumulative sensitive index, variations in the sensitivity showed that two cultivars (Wardan and Bundel) were sensitive to elevated O 3, while other three cultivars (Fahli, Saidi, and Mescavi) were resistant, and JHB-146 showed intermediate sensitivity. Therefore, the present study supported the selection of sensitive cultivar of clover as a bioindicator for O 3 under Indian conditions for the areas experiencing higher concentrations of O 3. 相似文献
2.
The concentrations of O 3 are increasing, which may have potential adverse effects on crop yield. This paper deals with assessing the intraspecific variability of two wheat cultivars (PBW 343 and M 533) at different growth stages using open top chambers. Mean O 3 concentrations were 50.2 and 53.2 ppb, and AOT40 values were 9 and 12.1 ppm h, respectively, in 2008–2009 and 2009–2010. Reproductive stage showed higher AOT40 values (6.9 and 9.2 ppm h) compared to vegetative (2.23 and 2.9 ppm h). Critical levels of a 3-month AOT 40 of 3 ppm h led to 6 % yield reduction in two wheat cultivars for two consecutive years. Variations in photosynthesis rate, stomatal conductance (g s), Fv/Fm ratio, photosynthetic pigments, primary and secondary metabolites, morphological parameters, and yield attributes were measured at vegetative and reproductive stages. Reductions in number of leaves, leaf area, total biomass, root/shoot ratio, RGR, photosynthetic pigments, protein content, and Fv/Fm ratio in PBW 343 were more than M 533 at reproductive stage. Photosynthetic rate did not vary between the cultivars, but g s was higher in PBW 343 compared to M 533 under ambient O 3. Higher total phenolics and peroxidase activity were recorded in M 533 at reproductive stage conferring higher resistance at latter age. Results of O 3 resistance showed that M 533 was sensitive compared to PBW 343 during vegetative stage but developed more resistance at reproductive stage. PBW 343 with larger leaf area and high g s is more sensitive than M 533 with smaller leaf area and low g s. The study suggests that the sensitivity varied with plant growth stage, and the plant showing higher sensitivity during vegetative period developed more resistance during reproductive period due to higher defense mechanism. Though the yield reductions were same in both cultivars under ambient O 3, the mechanism of acquiring the resistance is different between the cultivars. 相似文献
3.
To assess the effects of tropospheric O 3 on rice cultivated in Bangladesh, four Bangladeshi cultivars (BR11, BR14, BR28 and BR29) of rice ( Oryza sativa L.) were exposed daily to charcoal-filtered air or O 3 at 60 and 100 nl l −1 (10:00-17:00) from 1 July to 28 November 2008. The whole-plant dry mass and grain yield per plant of the four cultivars were significantly reduced by the exposure to O 3. The exposure to O 3 significantly reduced net photosynthetic rate of the 12th and flag leaves of the four cultivars. The sensitivity to O 3 of growth, yield and leaf gas exchange rates was not significantly different among the four cultivars. The present study suggests that the sensitivity to O 3 of yield of the four Bangladeshi rice cultivars is greater than that of American rice cultivars and is similar to that of Japanese rice cultivars and that O 3 may detrimentally affect rice production in Bangladesh. 相似文献
4.
To investigate the effects of ambient-level gas-phase peroxides concurrent with O 3 on foliar injury, photosynthesis, and biomass in herbaceous plants, we exposed Japanese radish ( Raphanus sativus) to clean air, 50 ppb O 3, 100 ppb O 3, and 2-3 ppb peroxides + 50 ppb O 3 in outdoor chambers. Compared with exposure to 100 ppb O 3, exposure to 2-3 ppb peroxides + 50 ppb O 3 induced greater damage in foliar injury, net photosynthetic rates and biomass; the pattern of foliar injury and the cause of net photosynthetic rate reduction also differed from those occurring with O 3 exposure alone. These results indicate for the first time that sub-ppb peroxides + 50 ppb O 3 can cause more severe damage to plants than 100 ppb O 3, and that not only O 3, but also peroxides, could be contributing to the herbaceous plant damage and forest decline observed in Japan's air-polluted urban and remote mountains areas. 相似文献
5.
Gas exchange responses to static and variable light were tested in three species: snap bean ( Phaseolus vulgaris, two cultivars), California black oak ( Quercus kelloggii), and blue oak ( Q. douglasii). The effects of 1-month (snap beans) and 2-month (oaks) O 3 (ozone) exposure (70 ppb over 8 h per day in open-top chambers) were investigated. A delay in stomatal responses (i.e., ‘sluggish’ responses) to variable light was found to be both an effect of O 3 exposure and a reason for increased O 3 sensitivity in snap bean cultivars, as it implied higher O 3 uptake during times of disequilibrium. Sluggishness increased the time to open (thus limiting CO 2 uptake) and close stomata (thus increasing transpirational water loss) after abrupt changes in light level. Similar responses were shown by snap beans and oaks, suggesting that O 3-induced stomatal sluggishness is a common trait among different plant physiognomic classes. 相似文献
6.
Modelling-based studies to assess the extent and magnitude of ozone (O 3) risk to agriculture in Asia suggest that yield losses of 5–20% for important crops may be common in areas experiencing elevated O 3 concentrations. These assessments have relied on European and North American dose–response relationships and hence assumed an equivalent Asian crop response to O 3 for local cultivars, pollutant conditions and climate. To test this assumption we collated comparable dose–response data derived from fumigation, filtration and EDU experiments conducted in Asia on wheat, rice and leguminous crop species. These data are pooled and compared with equivalent North American dose–response relationships. The Asian data show that at ambient O 3 concentrations found at the study sites (which vary between ~35–75 ppb 4–8 h growing season mean), yield losses for wheat, rice and legumes range between 5–48, 3–47 and 10–65%, respectively. The results indicate that Asian grown wheat and rice cultivars are more sensitive to O 3 than the North American dose–response relationships would suggest. For legumes the scatter in the data makes it difficult to reach any equivalent conclusion in relative sensitivities. As such, existing modelling-based risk assessments may have substantially underestimated the scale of the problem in Asia through use of North American derived dose–response relationships. 相似文献
7.
Ozone and other air quality data from five rural sites in the industrialized Latrobe Valley, Victoria, have been subject to statistical analyses including linear regression modelling. The behaviour of O 3 in the Latrobe Valley is explained largely in terms of natural background atmospheric processes as observed at Cape Grim, Tasmania.The maximum 1-h average concentration of naturally occurring O 3 (obtained from a 6-year record at Cape Grim) is less than 40 ppb (v/v). In contrast the industrialized Latrobe Valley sites show O 3 values exceeding 40 ppb between 1% and 3% of the time. These higher concentrations occur in conditions consistent with local photochemical production of O 3 via ‘smog’ type processes and appear preferentially at low NO x concentrations (3–4 ppb) during the afternoon (13–18 h) and at high temperatures (above 25°C).A comparison of observations from an elevated station (750 m) with those from the valley floor shows systematic differences in seasonal and diurnal O 3 variations and the time of day of occurrence of elevated O 3 concentrations which can be explained in terms of the diurnal cycle of convective mixing and mountain/valley winds.A linear regression model incorporating this understanding has accounted for between 43% and 64% of the variance of O 3 concentration at the elevated and rural stations. The statistical model incorporates temperature, time of day, month of year, wind speed, O 3 concentration 24-h earlier and NO x concentration as variables in the regression equation, with temperature being the dominant variable. The standard deviation of the residual O 3 values (observed minus fitted) is around 5 ppb. Auto and cross correlations are used to show that perhaps half of the unexplained variance is coherent from site to site and hence potentially could be modelled. 相似文献
8.
The antiozonant EDU (ethylenediurea) was used to assess the impact of ambient O 3 under field conditions on five cultivars of tropical wheat ( Triticum aestivum L.). EDU solution (0 ppm and 400 ppm) was applied as soil drench (100 ml plant ?1) 10 days after germination (DAG) at an interval of 12 days. EDU-treated plants showed significant increments in stomatal conductance, photosynthetic rate, variable fluorescence, total chlorophyll, ascorbic acid, proline and protein contents and protective enzymes (POX, SOD and APX) activities in HUW468, HUW510 and HUW234 cultivars, while, a reverse trend was observed for lipid peroxidation. EDU application restored grain yield significantly by maintaining higher levels of antioxidants, metabolites and enzymes in cultivars HUW468 and HUW510. Sonalika and PBW343 showed least response of measured parameters under EDU treatment suggesting their greater resistance to O 3. EDU, thus proved its usefulness in screening suitable wheat cultivars for areas experiencing elevated concentrations of O 3. 相似文献
9.
Thousands of tons of mercury (Hg) are released from anthropogenic and natural sources to the atmosphere in a gaseous elemental form per year, yet little is known regarding the influence of airborne Hg on the physiological activities of plant leaves. In the present study, the effects of low-level air and soil Hg exposures on the gas exchange parameters of maize ( Zea mays L.) leaves and their accumulation of Hg, proline, and malondialdehyde (MDA) were examined via field open-top chamber and Hg-enriched soil experiments, respectively. Low-level air Hg exposures (<50 ng m ?3) had little effects on the gas exchange parameters of maize leaves during most of the daytime ( p?>?0.05). However, both the net photosynthesis rate and carboxylation efficiency of maize leaves exposed to 50 ng m ?3 air Hg were significantly lower than those exposed to 2 ng m ?3 air Hg in late morning ( p?<?0.05). Additionally, the Hg, proline, and MDA concentrations in maize leaves exposed to 20 and 50 ng m ?3 air Hg were significantly higher than those exposed to 2 ng m ?3 air Hg ( p?<?0.05). These results indicated that the increase in airborne Hg potentially damaged functional photosynthetic apparatus in plant leaves, inducing free proline accumulation and membrane lipid peroxidation. Due to minor translocation of soil Hg to the leaves, low-level soil Hg exposures (<1,000 ng g ?1) had no significant influences on the gas exchange parameters, or the Hg, proline, and MDA concentrations in maize leaves ( p?>?0.05). Compared to soil Hg, airborne Hg easily caused physiological stress to plant leaves. The effects of increasing atmospheric Hg concentration on plant physiology should be of concern. 相似文献
10.
South Asia, particularly the Indo-Gangetic Plains and foothills of the Himalayas, has been found to be a major source of pollutant gases and particles affecting the regional as well as the global climate. Inventories of greenhouse gases for the South Asian region, particularly the sub-Himalayan region, have been inadequate. Hence, measurements of the gases are important from effective characterization of the gases and their climate effects. The diurnal, seasonal, and annual variation of surface level O 3 measured for the first time in northeast India at Dibrugarh (27.4° N, 94.9° E, 111 m amsl), a sub-Himalayan location in the Brahmaputra basin, from November 2009 to May 2013 is presented. The effect of the precursor gases NO x and CO measured simultaneously during January 2012–May 2013 and the prevailing meteorology on the growth and decay of O 3 has been studied. The O 3 concentration starts to increase gradually after sunrise attaining a peak level around 1500 hours LT and then decreases from evening till sunrise next day. The highest and lowest monthly maximum concentration of O 3 is observed in March (42.9?±?10.3 ppb) and July (17.3?±?7.0 ppb), respectively. The peak in O 3 concentration is preceded by the peaks in NO x and CO concentrations which maximize during the period November to March with peak values of 25.2?±?21.0 ppb and 1.0?±?0.4 ppm, respectively, in January. Significant nonlinear correlation is observed between O 3 and NO, NO 2, and CO. National Atmospheric and Oceanic Administration Hybrid Single-Particle Lagrangian Integrated Trajectory back-trajectory and concentration weighted trajectory analysis carried out to delineate the possible airmass trajectory and to identify the potential source region of NO x and O 3 concentrations show that in post-monsoon and winter, majority of the trajectories are confined locally while in pre-monsoon and monsoon, these are originated at the Indo-Gangetic plains, Bangladesh, and Bay of Bengal. 相似文献
11.
The effects of elevated concentrations of atmospheric tropospheric ozone (O 3) on DNA damage in five trembling aspen ( Populus tremuloides Michx.) clones growing in a free-air enrichment experiment in the presence and absence of elevated concentrations of carbon dioxide (CO 2) were examined. Growing season mean hourly O 3 concentrations were 36.3 and 47.3 ppb for ambient and elevated O 3 plots, respectively. The 4th highest daily maximum 8-h ambient and elevated O 3 concentrations were 79 and 89 ppb, respectively. Elevated CO 2 averaged 524 ppm (+150 ppm) over the growing season. Exposure to O 3 and CO 2 in combination with O 3 increased DNA damage levels above background as measured by the comet assay. Ozone-tolerant clones 271 and 8L showed the highest levels of DNA damage under elevated O 3 compared with ambient air; whereas less tolerant clone 216 and sensitive clones 42E and 259 had comparably lower levels of DNA damage with no significant differences between elevated O 3 and ambient air. Clone 8L was demonstrated to have the highest level of excision DNA repair. In addition, clone 271 had the highest level of oxidative damage as measured by lipid peroxidation. The results suggest that variation in cellular responses to DNA damage between aspen clones may contribute to O 3 tolerance or sensitivity. 相似文献
12.
Source contributions to the surface O 3 concentrations in southern Ontario were assessed for the 1979–1985 period. Ozone episode analyses indicate a frequency of about nine episodes per year (15 episode-days). These occur primarily in the summer months and are generally manifestations of the northern extent of the O 3 problem in eastern North America. Widespread elevated O 3 levels tend to occur under weather classes indicative of back or centre of the high pressure situations and associated flow/trajectory from areas south/southwest of the lower Great Lakes. These episodes vary considerably from year-to-year. Local impacts on O 3 levels are generally small.A study of O 3 levels during cloud-free summer days for the period 1981–1985 gave local ‘background’ O 3 levels of about 20–30 ppb daily and 30–50 ppb hourly maxima. The O 3 contributions from the U.S. to southern Canada (assuming local ‘background’ O 3 levels to be independent of wind direction) were estimated to be 30–35 ppb daily and 30–50 ppb hourly maxima. These results indicate an overall O 3 contribution of about 50–60% from the U.S. to southern Ontario. For episode-days, the U.S. contribution is even more significant. 相似文献
13.
Betula papyrifera trees were exposed to elevated concentrations of CO 2 (1.4 × ambient), O 3 (1.2 × ambient) or CO 2 + O 3 at the Aspen Free-air CO 2 Enrichment Experiment. The treatment effects on leaf surface characteristics were studied after nine years of tree exposure. CO 2 and O 3 increased epidermal cell size and reduced epidermal cell density but leaf size was not altered. Stomatal density remained unaffected, but stomatal index increased under elevated CO 2. Cuticular ridges and epicuticular wax crystallites were less evident under CO 2 and CO 2 + O 3. The increase in amorphous deposits, particularly under CO 2 + O 3, was associated with the appearance of elongated plate crystallites in stomatal chambers. Increased proportions of alkyl esters resulted from increased esterification of fatty acids and alcohols under elevated CO 2 + O 3. The combination of elevated CO 2 and O 3 resulted in different responses than expected under exposure to CO 2 or O 3 alone. 相似文献
14.
A 2-year open-top chamber experiment with field-grown winter wheat ( Triticum aestivum L. cv. Astron) was conducted to examine the effects of ozone on plant growth and selected groups of soil mesofauna in the rhizosphere. From May through June in each year, plants were exposed to two levels of O 3: non-filtered (NF) ambient air or NF+ 40 ppb O 3 (NF+). During O 3 exposure, soil sampling was performed at two dates according to different plant growth stages. O 3 exposure reduced above- and below-ground plant biomass in the first year, but had little effect in the second year. The individual density of enchytraeids, collembolans and soil mites decreased significantly in the rhizosphere of plants exposed to NF+ in both years. Differences were highest around anthesis, i.e. when plants are physiologically most active. The results suggest that elevated O 3 concentrations may influence the dynamic of decomposition processes and the turnover of nutrients. 相似文献
15.
A field study was conducted to evaluate the impact of ambient ozone on mustard ( Brassica campestris L. var. Kranti) plants grown under recommended and 1.5 times recommended NPK doses at a rural site of India using filtered (FCs) and non-filtered open top chambers (NFCs). Ambient mean O 3 concentration varied from 41.65 to 54.2 ppb during the experiment. Plants growing in FCs showed higher photosynthetic rate at both NPK levels, but higher stomatal conductance only at recommended NPK. There were improvements in growth parameters and biomass of plants in FCs as compared to NFCs at both NPK levels with higher increments at 1.5 times recommended. Seed yield and harvest index decreased significantly only at recommended NPK in NFCs. Seed quality in terms of nutrients, protein and oil contents reduced in NFCs at recommended NPK. The application of 1.5 times recommended NPK provided protection against yield loss due to ambient O 3. 相似文献
16.
Abstract A comprehensive, systematic synthesis was conducted of daily time-series studies of air pollution and mortality from around the world. Estimates of effect sizes were extracted from 109 studies, from single- and multipollutant models, and by cause of death, age, and season. Random effects pooled estimates of excess all-cause mortality (single-pollutant models) associated with a change in pollutant concentration equal to the mean value among a representative group of cities were 2.0% (95% CI 1.5-2.4%) per 31.3 μg/m 3 particulate matter (PM) of median diameter <10 μm (PM 10); 1.7% (1.2-2.2%) per 1.1 ppm CO; 2.8% (2.1-3.5%) per 24.0 ppb NO 2; 1.6% (1.1-2.0%) per 31.2 ppb O 3; and 0.9% (0.7-1.2%) per 9.4 ppb SO 2 (daily maximum concentration for O 3, daily average for others). Effect sizes were generally reduced in multipollutant models, but remained significantly different from zero for PM 10 and SO 2. Larger effect sizes were observed for respiratory mortality for all pollutants except O 3. Heterogeneity among studies was partially accounted for by differences in variability of pollutant concentrations, and results were robust to alternative approaches to selecting estimates from the pool of available candidates. This synthesis leaves little doubt that acute air pollution exposure is a significant contributor to mortality. 相似文献
17.
Ozone concentrations in Alberta cities typically exhibit a maximum in May (up to 35 ppb) and a minimum in November (as low as 4 ppb). This behaviour is similar to that of rural Alberta O 3 concentrations. Annual O 3 concentrations at six urban monitoring stations vary from 11 ppb to 22 ppb and are about one-half the values at rural stations. In winter, urban O 3 concentrations are always smaller than rural concentrations and the cities act as sinks for O 3. Although urban stations do not exceed Canada's maximum acceptable levels of daily (25 ppb) and annual (15 ppb) O 3 concentrations as often as rural stations, the frequency is still quite large. Canada's hourly maximum desirable level (50 ppb) is exceeded 11 times more often at the remote (rural) station than at the downtown (urban) stations. 相似文献
18.
Meta-analysis was conducted to quantitatively assess the effects of rising ozone concentrations ([O 3]) on yield and yield components of major food crops: potato, barley, wheat, rice, bean and soybean in 406 experimental observations. Yield loss of the crops under current and future [O 3] was expressed relative to the yield under base [O 3] (≤26 ppb). With potato, current [O 3] (31–50 ppb) reduced the yield by 5.3%, and it reduced the yield of barley, wheat and rice by 8.9%, 9.7% and 17.5%, respectively. In bean and soybean, the yield losses were 19.0% and 7.7%, respectively. Compared with yield loss at current [O 3], future [O 3] (51–75 ppb) drove a further 10% loss in yield of soybean, wheat and rice, and 20% loss in bean. Mass of individual grain, seed, or tuber was often the major cause of the yield loss at current and future [O 3], whereas other yield components also contributed to the yield loss in some cases. No significant difference was found between the responses in crops grown in pots and those in the ground for any yield parameters. The ameliorating effect of elevated [CO 2] was significant in the yields of wheat and potato, and the individual grain weight in wheat exposed to future [O 3]. These findings confirm the rising [O 3] as a threat to food security for the growing global population in this century. 相似文献
19.
The present work provides an insight into the development of biochemical adaptations in mung beans against ozone (O3) toxicity. The study aims to explore the O3 stress tolerance potential of mung bean genotypes under exogenous application of growth regulators. The seeds of twelve mung bean genotypes were grown in plastic pots under controlled conditions in the glasshouse. Six treatments, control (ambient ozone level 40–45 ppb), ambient O3 with ascorbic acid, ambient ozone with silicic acid, elevated ozone (120 ppb), elevated O3 with ascorbic acid (10 mM), and elevated ozone with silicic acid (0.1 mM) were applied. The O3 fumigation was carried out using an O3 generator. The results revealed that ascorbic acid and silicic acid application decreased the number of plants with foliar O3 injury symptoms in different degrees, i.e., zero, first, second, third, and fourth degrees; whereas 0–4 degree symptoms represent, no symptoms, symptoms occupying?<?1/4, 1/4–1/2, 1/2–3/4, and?>?3/4 of the total foliage area, respectively. Application of ascorbic acid and silicic acid also prevented the plants from the negative effects of O3 in terms of fresh as well as dry matter production, leaf chlorophyll, carotenoids, soluble proteins and ascorbic acid, proline, and malondialdehyde (MDA) contents. Overall, silicic acid application proved more effective in reducing the negative effects of O3 on mung bean genotypes as compared to that of the ascorbic acid. Three mung bean genotypes (NM 20–21, NM-2006, and NM-2016) were identified to have a better adaptive mechanism for O3 toxicity tolerance and may be good candidates for future variety development programs. 相似文献
20.
The effects of elevated O 3 on photosynthetic properties in adult beech trees ( Fagus sylvatica) were investigated in relation to leaf mass per area as a measure of the gradually changing, within-canopy light availability. Leaves under elevated O 3 showed decreased stomatal conductance at unchanged carboxylation capacity of Rubisco, which was consistent with enhanced δ 13C of leaf organic matter, regardless of the light environment during growth. In parallel, increased energy demand for O 3 detoxification and repair was suggested under elevated O 3 owing to enhanced dark respiration. Only in shade-grown leaves, light-limited photosynthesis was reduced under elevated O 3, this effect being accompanied by lowered Fv/ Fm. These results suggest that chronic O 3 exposure primarily caused stomatal closure to adult beech trees in the field regardless of the within-canopy light gradient. However, light limitation apparently raised the O 3 sensitivity of photosynthesis and accelerated senescence in shade leaves. 相似文献
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