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1.
The effects of ozone (O 3) exposure under different water availabilities were studied in two Mediterranean tree species: Quercus ilex and Ceratonia siliqua. Plants were exposed to different O 3 concentrations in open top chambers (charcoal-filtered air (CF), non-filtered air (NF)) and non-filtered air plus 40 ppb v of O 3 ((7:00–17:00 solar time) (NF+)) during 2 years, and to different water regimes (IR, sample irrigation, and WS, reduced water dose to 50%) through the last of those 2 years. AOT40 in the NF+ treatment was 59265 ppb v h (from March 1999 to August 1999) while in the NF treatment, the AOT40 was 6727 ppb v h for the same period. AOT40 was always 0 in the CF treatment. WS plants presented lower stomatal conductances and net photosynthetic rates, and higher foliar N concentrations than IR plants in both species. The irrigation treatment did not change the response trends to ozone in Q. ilex, the most sensitive species to O 3 ambient concentrations, but it changed those of C. siliqua, the least sensitive species, since its ozone-fumigated WS plants did not decrease their net photosynthetic rates nor their biomass accumulation as it happened to its ozone-fumigated IR plants. These results show interspecific variations in O 3 sensitivity under different water availabilities. 相似文献
2.
The influence of ambient ozone (O 3) concentrations and nitrogen (N) fertilization, singly and in combination, on the growth and nutritive quality of Trifolium subterraneum was assessed. This is an important O 3-sensitive species of great pastoral value in Mediterranean areas. Plant material was enclosed in open-top chambers (OTCs). Three O 3 levels were established: Filtered air with O 3 concentrations below 15 ppb (CFA), non-filtered air with O 3 concentrations in the range of ambient levels (NFA), and non-filtered air supplemented with 40 ppb O 3 over ambient levels (NFA+). Similarly, three N levels were defined: 5, 15 and 30 kg ha −1. The increase in O 3 exposure induced a reduction of the clover aerial green biomass and an increase of senescent biomass. Ozone effects were more adverse in the root system, inducing an impairment of the aerial/subterranean biomass ratio. Compared with the CFA treatment, nutritive quality of aerial biomass was 10 and 20% lower for NFA and NFA+ treatments, respectively, due to increased concentrations of acid detergent fiber, neutral detergent fiber and lignin. The latter effect appears to be related to senescence acceleration. The increment in N supplementation enhanced the increase of ADF concentrations in those plants simultaneously exposed to ambient and above-ambient O 3 concentrations, and reduced the incremental rate of foliar senescence induced by the pollutant. 相似文献
3.
We investigated the effect of leaf age on the response of net photosynthesis (A), stomatal conductance ( gwv), foliar injury, and leaf nitrogen concentration (N L) to tropospheric ozone (O 3) on Prunus serotina seedlings grown in open-plots (AA) and open-top chambers, supplied with either carbon-filtered or non-filtered air. We found significant variation in A, g wv, foliar injury, and N L ( P < 0.05) among O 3 treatments. Seedlings in AA showed the highest A and g wv due to relatively low vapor pressure deficit (VPD). Older leaves showed significantly lower A, g wv, N L, and higher foliar injury ( P < 0.001) than younger leaves. Leaf age affected the response of A, g wv, and foliar injury to O 3. Both VPD and N L had a strong influence on leaf gas exchange. Foliar O 3-induced injury appeared when cumulative O 3 uptake reached 8-12 mmol m −2, depending on soil water availability. The mechanistic assessment of O 3-induced injury is a valuable approach for a biologically relevant O 3 risk assessment for forest trees. 相似文献
4.
Open pollinated families of black cherry seedlings were studied to determine genotypic differences in foliar ozone injury and leaf gas exchange in 1994 and growth response following three growing seasons. An O(3)-sensitive half-sibling family (R-12) and an O(3)-tolerant half-sibling family (MO-7) planted in natural soil were studied along with generic nursery stock (NS) seedlings. Ozone exposure treatments were provided through open top chambers and consisted of 50, 75, and 97% of ambient ozone, and open plots from May 9 to August 26, 1994. Ambient ozone concentrations reached an hourly peak of 88 ppb with 7-hour averages ranging from 39 to 46 ppb. Seedlings in the 50 and 75% of ambient chambers were never exposed to greater than 80 ppb O(3). Visible foliar ozone injury (stipple) was significantly higher for R-12 seedlings than MO-7 seedlings and increased with increasing ozone exposures. For the chamber treatments averaged over all families, there was no significant difference in stomatal conductance and net photosynthetic rates, but there was a significant decrease in root biomass, and a significant decrease in root/shoot ratio between the 50 and 97% of ambient chambers. Stomatal conductance and net photosynthetic rates were significantly different between families with R-12 seedlings generally greater than MO-7 seedlings. The R-12 seedlings had a 7.5 mmol m(-2) increase in ozone uptake compared to MO-7, and at the same cumulative O(3) exposure R-12 exhibited 40.9% stippled leaf area, whereas MO-7 had 9.2% stippled leaf area. Significant differences were observed in stem volume growth and total final biomass between the open-top chambers and open plots. Although R-12 had the most severe foliar ozone injury, this family had significantly greater stem volume growth and total final biomass than MO-7 and NS seedlings. Root:shoot ratio was not significantly different between MO-7 and R-12 seedlings. 相似文献
5.
The combined impacts of simulated increased nitrogen (N) deposition (75 kg N ha −1 yr −1) and increasing background ozone (O 3) were studied using two mesotrophic grassland species ( Dactylis glomerata and Ranunculus acris) in solardomes, by means of eight O 3 treatments ranging from 15.5 ppb to 92.7 ppb (24 h average mean). A- Ci curves were constructed for each species to gauge effects on photosynthetic efficiency and capacity, and effects on biomass partitioning were determined after 14 weeks. Increasing the background concentration of O 3 reduced the healthy above ground and root biomass of both species, and increased senesced biomass. N fertilisation increased biomass production in D. glomerata, and a significantly greater than additive effect of O 3 and N on root biomass was evident. In contrast, R. acris biomass was not affected by high N. The study shows the combined effects of these pollutants have differential implications for carbon allocation patterns in common grassland species. 相似文献
6.
Rapid industrialization and economic developments have increased the tropospheric ozone (O 3) budget since preindustrial times, and presently, it is supposed to be a major threat to crop productivity. Maize ( Zea mays L.), a C4 plant is the third most important staple crop at global level with a great deal of economic importance. The present study was conducted to evaluate the performance of two maize cultivars [HQPM1: quality protein maize (QPM)] and [DHM117: nonquality protein maize (NQPM)] to variable O 3 doses. Experimental setup included filtered chambers, nonfiltered chambers (NFC), and two elevated doses of O 3 viz. NFC+15 ppb O 3 (NFC+15) and NFC+30 ppb O 3 (NFC+30). During initial growth period, both QPM and NQPM plants showed hormetic effect that is beneficial due to exposure of low doses of a toxicant (NFC and NFC+15 ppb O 3), but at later stages, growth attributes were negatively affected by O 3. Growth indices showed the variable pattern of photosynthate translocation under O 3 stress. Foliar injury in the form of interveinal chlorosis and reddening of leaves due to increased production of anthocyanin pigments was observed at higher concentrations of O 3. One-dimensional gel electrophoresis of leaves taken from NFC+30 showed reductions of major photosynthetic proteins, and differential response was observed between the two test cultivars. Decline in the number of male flowers at elevated O 3 doses suggested damaging effect of O 3 on reproductive structures which might be a cause of productivity losses. Variable carbon allocation pattern particularly to husk leaves, foliar injury, and damage of photosynthetic proteins led to significant reductions in economic yield at higher O 3 doses. PCA showed that both the cultivars responded more or less similarly to O 3 stress in their respective groupings of growth and yield parameters, but magnitude of their response was variable. It is further supported by difference in the significance of correlations between variables of yield and AOT40. Cultivar response reflects that QPM performed better than NQPM against elevated O 3. 相似文献
7.
Concentrations of CO, SO 2, NO, NO 2, and NO Y were measured atop the University of Houston's Moody Tower supersite during the 2006 TexAQS-II Radical and Aerosol Measurement Project (TRAMP). The lowest concentrations of all primary and secondary species were observed in clean marine air in southerly flow. SO 2 concentrations were usually low, but increased dramatically in sporadic midday plumes advected from sources in the Houston Ship Channel (HSC), located NE of the site. Concentrations of CO and NO x displayed large diurnal variations in keeping with their co-emission by mobile sources in the Houston Metropolitan Area (HMA). CO/NO x emission ratios of 5.81 ± 0.94 were observed in the morning rush hour. Nighttime concentrations of NO x (NO x = NO + NO 2) and NO Y (NO Y = NO + NO 2 + NO 3 + HNO 3 + HONO + 21N 2O 5 + HO 2NO 2 + PANs + RONO 2 + p-NO 3? + …) were highest in winds from the NNW-NE due to emission from mobile sources. Median ratios of NO x/NO Y were approximately 0.9 overnight, reflecting the persistence and/or generation of NO Z (NO Z = NO Y ? NO x) species in the nighttime Houston boundary layer, and approached unity in the morning rush hour. Daytime concentrations of NO x and NO Y were highest in winds from the HSC. NO x/NO Y ratios reached their minimum values (median ca 0.63) from 1300 to 1500 CST, near local solar noon, and air masses often retained enough NO x to sustain additional O 3 formation farther downwind. HNO 3 and PANs comprised the dominant NO Z species in the HMA, and on a median basis represented 17–20% and 12–15% of NO Y, respectively, at midday. Concentrations of HNO 3, PANs, and NO Z, and fractional contributions of these species to NO Y, were at a maximum in NE flow, reflecting the source strength and reactivity of precursor emissions in the HSC. As a result, daytime O 3 concentrations were highest in air masses with HSC influence. Overall, our findings confirm the impact of the HSC as a dominant source region within the HMA. A comparison of total NO Y measurements with the sum of measured NO Y species (NO Yi = NO x + HNO 3 + PANs + HONO + p-NO 3?) yielded excellent overall agreement during both day ([NO Y](ppb) = ([NO Yi](ppb)11.03 ± 0.16) ? 0.42; r2 = 0.9933) and night ([NO Y](ppb) = ([NO Yi](ppb)11.01 ± 0.16) + 0.18; r2 = 0.9975). A similar comparison between NO Y–NO x concentrations and the sum of NO Zi (NO Zi = HNO 3 + PANs + HONO + p-NO 3?) yielded good overall agreement during the day ([NO Z](ppb) = ([NO Zi](ppb)11.01 ± 0.30) + 0.044 ppb; r2 = 0.8527) and at night ([NO Z](ppb) = ([NO Zi](ppb)11.12 ± 0.69) + 0.16 ppb; r2 = 0.6899). Median ratios of NO Z/NO Zi were near unity during daylight hours but increased to approximately 1.2 overnight, a difference of 0.15–0.50 ppb. Differences between NO Z and NO Zi rarely exceeded combined measurement uncertainties, and variations in NO Z/NO Zi ratios may have resulted solely from errors in conversion efficiencies of NO Y species and changes in NO Y composition. However, nighttime NO Z/NO Zi ratios and the magnitude of NO Z ? NO Zi differences were generally consistent with recent observations of ClNO 2 in the nocturnal Houston boundary layer. 相似文献
8.
Most available exposure-response relationships for assessing crop loss due to elevated ozone (O 3) have been established using data from chamber and open-top chamber experiments, using a simulated constant O 3 concentration exposure (square wave), which is not consistent with the diurnal variation of O 3 concentration that occurs in nature. We investigated the response of oilseed rape ( Brassica napus L.) to O 3 as affected by two exposure regimes: one with a diurnal variation (CF100D) and another with a constant concentration (CF100). Although the two exposure regimes have the same mean O 3 concentration and accumulated O 3 concentration above 40 ppb (AOT40), our results show that O 3 at CF100D reduced biomass and number of pods/plant more than O 3 at CF100. Both O 3 exposures resulted in larger seed weights/100 pods compared to CF. Numbers of seeds/100 pods were reduced by CF100, while numbers of seeds/100 pods in the CF100D chambers were comparable to those in CF. Our results suggest that chamber experiments that use a constant O 3 exposure may underestimate O 3 effects on biomass and yields. 相似文献
9.
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
10.
An assessment of the effects of tropospheric ozone (O 3) levels and substrate nitrogen (N) supplementation, singly and in combination, on phenology, growth and nutritive quality of Briza maxima was carried out. Two serial experiments were developed in Open-Top Chambers (OTC) using three O 3 and three N levels. Increased O 3 exposure did not affect the biomass-related parameters, but enhanced senescence, increased fiber foliar content (especially lignin concentration) and reduced plant life span; these effects were related to senescence acceleration induced by the pollutant. Added N increased plant biomass production and improved nutritive quality by decreasing foliar fiber concentration. Interestingly, the effects of N supplementation depended on meteorological conditions and plant physiological activity. N supplementation counteracted the O 3-induced senescence but did not modifiy the effects on nutritive quality. Nutritive quality and phenology should be considered in new definitions of the O 3 limits for the protection of herbaceous vegetation. 相似文献
11.
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
12.
A meta-analysis was conducted to quantitatively assess the effects of ethylenediurea (EDU) on ozone (O 3) injury, growth, physiology and productivity of plants grown in ambient air conditions. Results indicated that EDU significantly reduced O 3-caused visible injury by 76%, and increased photosynthetic rate by 8%, above-ground biomass by 7% and crop yield by 15% in comparison with non-EDU treated plants, suggesting that ozone reduces growth and yield under current ambient conditions. EDU significantly ameliorated the biomass and yield of crops and grasses, but had no significant effect on tree growth with an exception of stem diameter. EDU applied as a soil drench at a concentration of 200-400 mg/L has the highest positive effect on crops grown in the field. Long-term research on full-grown tree species is needed. In conclusion, EDU is a powerful tool for assessing effects of ambient [O 3] on vegetation. 相似文献
13.
Photosynthetic acclimation under elevated carbon dioxide (CO 2) and/or ozone (O 3) has been the topic of discussion in many papers recently. We examined whether or not aspen plants grown under elevated CO 2 and/or O 3 will acclimate after 11 years of exposure at the Aspen Face site in Rhinelander, WI, USA. We studied diurnal patterns of instantaneous photosynthetic measurements as well as A/C i measurements monthly during the 2004-2008 growing seasons. Our results suggest that the responses of two aspen clones differing in O 3 sensitivity showed no evidence of photosynthetic and stomatal acclimation under either elevated CO 2, O 3 or CO 2 + O 3. Both clones 42E and 271 did not show photosynthetic nor stomatal acclimation under elevated CO 2 and O 3 after a decade of exposure. We found that the degree of increase or decrease in the photosynthesis and stomatal conductance varied significantly from day to day and from one season to another. 相似文献
14.
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
15.
To clarify the effects of O 3 on crop plants cultivated in Bangladesh, two Bangladeshi wheat cultivars (Sufi and Bijoy) were grown in plastic boxes filled with Andisol and exposed daily to charcoal-filtered air or O 3 at 60 and 100 nl l −1 (10:00-17:00) from 13 March to 4 June 2008. The whole-plant dry mass and grain yield per plant of the two cultivars at the final harvest were significantly reduced by the exposure to O 3. Although there was no significant effect of O 3 on stomatal diffusive conductance to H 2O of flag leaf, net photosynthetic rate of the leaf was significantly reduced by the exposure to O 3. The sensitivity of growth, yield, yield components and leaf gas exchange rates to O 3 was not significantly different between the two cultivars. The results obtained in the present study suggest that ambient levels of O 3 may detrimentally affect wheat production in Bangladesh. 相似文献
16.
Psidium guajava “Paluma”, a tropical tree species, is known to be an efficient ozone indicator in tropical countries. When exposed to ozone, this species displays a characteristic leaf injury identified by inter-veinal red stippling on adaxial leaf surfaces. Following 30 days of three ozone treatments consisting of carbon filtered air (CF – AOT40 = 17 ppb h), ambient non-filtered air (NF – AOT40 = 542 ppb h) and ambient non-filtered air + 40 ppb ozone (NF + O 3 – AOT40 = 7802 ppb h), the amounts of residual anthocyanins and tannins present in 10 P. guajava (“Paluma”) saplings were quantified. Higher amounts of anthocyanins were found in the NF + O 3 treatment (1.6%) when compared to the CF (0.97%) and NF (1.30%) ( p < 0.05), and of total tannins in the NF + O 3 treatment (0.16%) compared to the CF (0.14%). Condensed tannins showed the same tendency as enhanced amounts. Regression analyses using amounts of tannins and anthocyanins, AOT40 and the leaf injury index (LII), showed a correlation between the leaf injury index and quantities of anthocyanins and total tannins. These results are in accordance with the association between the incidence of red-stippled leaves and ozone polluted environments. 相似文献
17.
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
18.
Two-week average concentrations of ozone (O 3), nitric acid vapor (HNO 3) and ammonia (NH 3) were measured with passive samplers during the 2002 summer season across the central Sierra Nevada Mountains, California, along the San Joaquin River drainage. Elevated concentrations of the pollutants were determined with seasonal means for individual sites ranging between 62 and 88 ppb for O 3, 1.0-3.8 μg m −3 for HNO 3, and 2.6-5.2 μg m −3 for NH 3. Calculated O 3 exposure indices were very high, reaching SUM00-191 ppm h, SUM60-151 ppm h, and W126-124 ppm h. Calculated nitrogen (N) dry deposition ranged from 1.4 to 15 kg N ha −1 for maximum values, and 0.4-8 kg N ha −1 for minimum values; potentially exceeding Critical Loads (CL) for nutritional N. The U.S., California, and European 8 h O 3 human health standards were exceeded during 104, 108, and 114 days respectively, indicating high risk to humans from ambient O 3. 相似文献
19.
The mixing ratios of surface ozone at two rural/remote sites in Thailand, Inthanon and Srinakarin, have been measured continuously for the first time. Almost identical seasonal variations of O 3 with dry season maximum and a wet season minimum with a large seasonal amplitude are observed at both sites during 1996–1998. At Inthanon, the monthly averaged O 3 mixing ratios range 9–55 ppb, with the annual average of 27 ppb. The ozone mixing ratios at Srinakarin are in the similar range, 9–45 ppb with annual average of 28 ppb. Based on trajectory analysis of O 3 data at Inthanon, the long-range transport of O 3 under Asian monsoon regime could primarily explain the low O 3 mixing ratios of 13 ppb in clean marine air mass from Indian Ocean during wet season but only partly explain the relatively low O 3 mixing ratios, 26 ppb or less, in continental air mass from northeast Asia either in wet or dry season. The highest O 3 mixing ratios are found in air masses transported within southeast Asia, averaged 46 ppb in dry season. The high O 3 mixing ratios during the dry season are suggested to be significantly due to the local/sub-regional scale O 3 production triggered by biomass burning in southeast Asia rather than long-range transport effect. 相似文献
20.
Cutleaf coneflower ( Rudbeckia laciniata L.) seedlings were placed into open-top chambers in May, 2004 and fumigated for 12 wks. Nine chambers were fumigated with either carbon-filtered air (CF), non-filtered air (NF) or twice-ambient (2×) ozone (O 3). Ethylenediurea (EDU) was applied as a foliar spray weekly at 0 (control), 200, 400 or 600 ppm. Foliar injury occurred at ambient (30%) and elevated O 3 (100%). Elevated O 3 resulted in significant decreases in biomass and nutritive quality. Ethylenediurea reduced percent of leaves injured, but decreased root and total biomass. Foliar concentrations of cell-wall constituents were not affected by EDU alone; however, EDU × O 3 interactions were observed for total cell-wall constituents and lignocellulose fraction. Our results demonstrated that O 3 altered the physiology and productivity of cutleaf coneflower, and although reducing visible injury EDU may be phytotoxic at higher concentrations. 相似文献
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