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At least 811 records · Page 45Linked to original sources
PubMed1990

Effect of ozone on growth of mosses on disturbed forest soil.

Mixed forest floor organic matter and upper mineral soil from a 1580 m elevation conifer-hardwood stand in the Pisgah National Forest, NC, was placed in 4-cm diameter x 21-cm deep tubes and exposed to 0.00, 0.08, 0.16, 0.24 or 0.32 microl O3/liter air (ppm). Twelve tubes in each of three replications/treatment were fumigated in continuously-stirred tank reactors in a greenhouse for 6 h/day on 4 consecutive days/week. Soil was watered 3 days/week with deionized water amended with ions and adjusted to pH 4.3 with H2SO4 + HNO3 (70 meq SO4(2-): 30 meq NO3(-)). After 10 weeks the amount of soil surface covered by moss (predominantly Ditrichum pusillum, but also D. lineare, and Pohlia nutans) was estimated visually and assigned a rating on a scale of: 1 = 0-25%; 2 = 26-50%; 3 = 51-75%; 4 = 76-100%. Linear regression analysis revealed a significant (p < 0.001) negative relationship between coverage ratings and O3 concentration. Surface coverage in tubes exposed to 0.32 or 0.24 ppm was about half of that for 0.00 ppm (mean ratings of 1.1, 1.4 and 2.6, respectively). Coverage differences appeared to be due in part to O3 suppression of plant numbers. Linear regression analysis also revealed a significant (p < 0.001) negative relationship between heights of D. pusillum plants (measured after 12 weeks treatment) and O3 concentration.

Journal Article↗
PubMed1990

Persistent effects of ozone on needle water loss and wettability in Norway spruce.

Four-year-old, seed-grown trees of Norway spruce (Picea abies (L.) Karst.) were exposed in open-top chambers to charcoal-filtered air (8 h daily mean 54 microg O(3) m(-3)) over three consecutive summers (1986-1988). In mid-May 1988, before the third season of fumigation and more than 7 months after exposure to ozone the previous summer had terminated, daily rates of transpiration from intact shoots and water loss from excised needles were measured together with the amount of wax on the needle surface. In mid-July, 92 days after the beginning of the third year of exposure, the wettability of needles was assessed by measuring the contact angle of water droplets on the surface of needles. Exposure to 156 microg O(3) m(-3) resulted in a 16% increase in daily transpiration in current year's needles and a 28% increase in 1-year old needles. These effects were associated with slower stomatal closure in response to increasing water deficit in the needles previously exposed to 156 microg m(-3) ozone. The long-lasting nature of such ozone-induced effects could predispose trees to drought and winter desiccation. No significant effects of ozone were found on the amount of wax covering the needle surface, but a marked increase in the wettability of needles exposed to ozone was observed. The far reaching physiological consequences of these effects in the field and the possibility that similar disturbances may contribute to the decline of high-altitude forests of Norway spruce in Europe are discussed.

Journal Article↗
PubMed1990

Effects of nitrogen dioxide pollution on the growth of three fern species.

The effects of exposing plants of Dryopteris filix-mas (L.) Schott, Phyllitis scolopendrium (L.) Newman and Polypodium vulgare L. to 60 nl litre(-1) (122 microg m(-3)) NO(2) for 37 weeks were investigated in a closed chamber fumigation system. There was no effect of NO(2) on the numbers of fronds produced for any species at any time during the exposure period. However, at the end of the study, there was a lower dry weight yield of green shoots of D. filix-mas and P. scolopendrium and a higher yield of green shoots of P. vulgare for plants in the NO(2) treatment as compared to control plants. These differences in shoot dry weights were not accompanied by an effect of NO(2) exposure on total plant dry weights.

Journal Article↗
PubMed1990

Ozone episodes in Southern Lower Saxony (FRG) and their impact on the susceptibility of cereals to fungal pathogens.

Spring wheat (Triticum aestivum L.) and spring barley (Hordeum vulgare L.) plants were exposed to simulated ozone (O(3)) episodes (7 h day(-1) for 7 days) at maximum concentrations of 120, 180 and 240 microg m(-3) O(3), in comparison to a charcoal-filtered air control. Fumigations were conducted in four closed chambers placed in a climate room. Exposures took place prior to inoculation of the plants with six different facultative leaf pathogens. On wheat, significant enhancement of leaf attack by Septoria nodorum Berk. and S. tritici Rob. ex Desm. appeared, particularly on the older leaves and at the highest level of O(3). The same was true for Gerlachia nivalis W. Gams et E. Müll/Fusarium culmorum (W.F.Sm.) Sacc. on wheat and net blotch (Drechslera teres (Sacc.) Shoem.) or G. nivalis leaf spots on barley. Disease development was promoted both on leaves with and without visible injury following exposure to O(3). Sporulation of the two Septoria species increased at 120 and 180 microg m(-3) O(3); however, it was reduced to the level of the control, if 240 microg m(-3) were applied. No significant effects of predisposition were observed with Bipolaris sorokiniana (Sacc.) Shoem. (syn. Helminthosporium sativum Pamm., King et Bakke), the causal agent of spot blotch, neither on wheat nor on barley. Doses and peak concentrations applied in the experiments were in good agreement with measurements of ambient ozone in Southern Lower Saxony, FRG. Six years' ozone data (1984-1989) revealed the annual occurrence of between 3 and 11 ozone episodes with potentially harmful effects on cereals (three or more consecutive 'ozone days' with 8-h means above 80 microg m(-3)). The frequency of ozone episodes followed by weather periods favourable for infections by facultative pathogens was higher in years with low O(3) pollution than in ozone-rich years, and varied between one and five cases per season. The number of ozone days during the main growing season of cereals (1 April until 31 August) varied from 25 in 1984 to 98 in 1989. However, only 7.9% of ozone days during the 6 years examined were concurrent with weather conditions suitable for fungal infections. It is concluded that the majority of leaf infections in the field happens under low-level concentrations of photooxidants.

Journal Article↗
PubMed1991

Sensitivity of three leguminous crops to O3 as influenced by different stages of growth and development.

The sensitivity of Cicer arietinum, Vigna mungo and Trigonella foenum-graecum to O(3) has been assessed at different stages of growth and development. Plants of different ages (0, 1, 2, 4 and 6 weeks old) were fumigated with 0 and 120 nl litre(-1) O(3), from 09.30 h to 16.30 h each day for four weeks, in hemispherical chambers located out-of-doors. Seed germination was not affected by O(3) in any of the species, but there were responses (differing between species) on the cotyledons. True leaves were fairly resistant when young but later they became more sensitive. Premature senescence and earlier abscission of leaves (in C. arietinum and T. foenum-graecum) and flowers and abortive fruit drop (in C. arietinum) were also observed. Of the five growth stages examined, 2- and 4-week-old plants seemed to be most sensitive except for Trigonella where sensitivity decreased with increasing age of the plants. The partitioning and distribution of dry matter among different plant parts was also significantly disturbed and root, leaf and stem were adversely affected in a decreasing order. However, the percentage reductions in dry weight per plants for Cicer and Vigna increased with age up to four weeks, then declined abruptly. Growth reductions at the 0- and 6-week-old stages differed only slightly and were very small in magnitude. It may, therefore, be suggested that the plants of these legumes in early stages of exponential growth are more vulnerable to O(3) damage and that the developmental or physiological age is an important factor in O(3) sensitivity.

Journal Article↗
PubMed1991

Air pollution and agricultural aphid pests. II chamber filtration experiments.

The responses of four major aphid pest species feeding on three major crops were studied in a series of experimental chambers on the roof of Imperial College in South Kensington, London. The experimental chambers were continually circulated with air which had been subjected to a variety of filtration treatments. In the first series of experiments there were three chambers subject to ambient air, charcoal-filtered air, and charcoal plus 'Purafil'-filtered air; in the subsequent experiments there were four chambers, a charcoal plus 'Purafil' plus charcoal treatment being added. These treatments provided a range of concentrations and mixtures of the ambient gases present at the site. The growth rate of aphids was measured both during filtration and post-filtration, the plants being exposed from sowing for either 42 or 84 days. In all cases there were significant effects on aphid performance which seemed to be most strongly linked to absolute and relative NO concentrations. The pattern of responses by the aphids accorded extremely well with those observed in closed-chamber fumigation experiments with stimulation of performance in relatively polluted air in all cases except Acyrthosiphon pisum (Harris) feeding on Vicia faba L. where the opposite effect was recorded.

Journal Article↗
PubMed1992

Effects of rural roadside levels of nitrogen dioxide on Polytrichum formosum Hedw.

Polytrichum formosum Hedw. was exposed to 60 nl litre(-1) (122.4 microm(-3)) NO2 for 37 weeks in a closed chamber fumigation system. This concentration was chosen to simulate roadside levels in rural areas. Over an initial winter period (October-January) growth of existing shoots was stimulated by NO2. When new growth was recorded in April and May, NO2 pollution over winter and spring had resulted in a 36% reduction in new (< 1 cm) shoot production, and a 46% reduction in old shoots showing new growth. It is concluded that plants of Polytrichum formosum Hedw. growing near to roads may be adversely affected by NO2 pollution. Adverse effects of NO2 on plants and possible synergistic effects with other pollutants could cause growth reductions in sensitive species, thus affecting species composition of roadside vegetation.

Journal Article↗
PubMed1992

The effects of sulphur gas and elemental sulphur dust deposition on Pinus contorta x Pinus banksiana: cell walls and water relations.

The bulk modulus of elasticity (E) for Pinus contorta (lodgepole pine) x Pinus banksiana (jack pine) hybrids was compared between a site (AI) close to a sour gas processing plant and a control site (AV). The mean bulk modulus of elasticity for branches from AI was 47.5 MPa vs 18.5 MPa for the control site (AV). Site AI had been exposed to S-gas emissions and large amounts of elemental S deposition and had an acidic soil (pH 4.0 at 10 cm depth). During 1981 the needles at AI had more aluminum and iron compared to those at AV (900 ppm vs 390 ppm AI in the 3-year-old needles). Mean leader growth was measured over a 3-year period and was observed to be greater at AI than AV (46+/-7 cm vs 29+/-9 cm for 1988). Histochemically, the needles at AI had higher phenol and lignin content than AV. These results suggest that the S-gas fumigation, S-dust deposition, plus increased concentrations of soluble aluminum and iron had altered the cell wall elastic properties resulting in altered water relations. The implications of this on leaf diffusive resistance and photosynthesis are discussed.

Journal Article↗
PubMed1993

Effects of acidic gases and mists on the reproductive capability of three fern species.

The effects of exposure to 40 nl litre(-1) SO2 + 40 nl litre(-1) NO2 on the reproductive biology of Polypodium interjectum (Shivas), Dryopteris affinis (Lowe) Fraser-Jenkins and Phyllitis scolopendrium (L.) Newman were investigated after 14 weeks exposure in a closed chamber fumigation system. The numbers of sori per pinna were reduced in response to SO2 and NO2 for D. affinis but were unaffected for the other species. Numbers of sporangia in sori and spore viability were reduced in P. interjectum and P. scolopendrium but not in D. affinis in response to the SO2 and NO2 treatment. Spore size was not affected by the pollution treatment. A separate experiment tested viabilities of spores collected from the three species in response to daily spraying with simulated mists at pHs of 2.5, 3.5, 4.5 and 5.6. For all three species, there was little or no spore germination in the pH 2.5 treatment and significantly reduced germination in response to the pH 3.5 as compared to the pH 4.5 and pH 5.6 treatments.

Journal Article↗
PubMed1993

Physiological effects of ozone on cultivars of watermelon (Citrullus lanatus) and muskmelon (Cucumis melo) widely grown in Spain.

Two cultivars of watermelon (Citrullus lanatus) and muskmelon (Cucumis melo), which are widely grown in Spain, were exposed to ozone (70 nl litre(-1), 6 h d(-1)) for 21 days. Ozone sensitivity was assessed by recording the extent of visible injury, changes in fast-fluorescence kinetics, the relative-growth rate (R) of root (RR) and shoot (RS), and effects on the number of flowers produced per plant. Leaf gas exchange was measured in order to provide some indication of the factors underlying differential response to ozone. After 9-10 days of fumigation, all the cultivars developed typical visible symptoms of zone injury on the older leaves. However, significant (P < 0.05) changes in fast-fluorescence kinetics were detected prior to the development of visible foliar injury, indicating that detectable effects of ozone on primary photochemical processes supersede the appearance of visible symptoms. In both muskmelon and watermelon, there was a marked reduction in the rate of CO(2) assimilation as a result of exposure to ozone, and this was accompanied by a parallel decrease in stomatal conductance. Mean plant-relative-growth rate (R) was markedly (P < 0.01) suppressed by ozone in the two cultivars of watermelon, but there were no significant effects on R in muskmelon. Ozone reduced root growth relative to the shoot in three out of four cultivars-an effect that may be of considerable ecological significance. Moreover, exposure to ozone reduced flower production in both muskmelon and watermelon, which indicated effects on yield. There was no correlation between a variety of methods used to assess ozone sensitivity and visible injury, and reasons for this are discussed. This observation draws clear attention to the dangers in ranking plants for ozone sensitivity purely on the basis of visible symptoms. It is concluded from this study that ozone-insensitive genotypes should be identified and considered for planting in the major areas of melon production concentrated on the Mediterranean coast of Spain.

Journal Article↗
PubMed1994

Effects of sulfur dioxide on growth, photosynthesis and enzyme activities of Chinese Guger-Tree seedlings.

The Chinese Guger-Tree (Schima superba Gard et Champ var. superba) is an important harwood species in Taiwan where the ambient SO(2) concentration in some areas is high. Seedlings were raised in field chambers with and without SO(2) to determine whether this species is affected by this pollutant. After 4 weeks of exposure to 325 ppb of SO(2), the photosynthetic rate of seedlings decreased immediately. During the fumigation period, stem height growth was not inhibited, however, the stem diameter growth was reduced significantly. The dry weight of leaves was unchanged, while stem, root and total seedling weight were lower than those of control plants. Sulfhydryl groups in leaves increased by 75%, whereas they did not change in roots following SO(2) uptake. Superoxide dismutase in leaves did not change, however, peroxidase activity increased significantly. Results suggest that ambient SO(2) in some areas in Taiwan may affect the physiology and growth of the Chinese Guger-Tree.

Journal Article↗
PubMed1994

Effects of various ozone exposures on the susceptibility of bean leaves (Phaseolus vulgaris L.) to Botrytis cinerea.

The effects of various ozone exposures in predisposing bean leaves (Phaseolus vulgaris L.) to Botrytis cinerea have been investigated under laboratory conditions. Seedlings of two bean cultivars were exposed to incremental ozone concentrations (120, 180 and 270 microg m(-3) for 8-h day(-1)) for five days and primary leaves were subsequently inoculated with conidia suspended in water or in an inorganic phosphate solution (Pi), and with mycelium. Ozone injury increased with increasing ozone concentration and was much higher in the ozone-sensitive cultivar 'Pros' than in the ozone-insensitive 'Groffy'. Ozone only increased the number of lesions on leaves of Pros after inoculation with either of the conidial suspensions. The Pi-stimulated infection in Groffy was reduced by the lower ozone concentrations. Ozone decreased lesion expansion after inoculation with mycelium. In a chronic fumigation experiment, plants of the two cultivars were exposed to 90 microg m(-3) (7-h day(-1)) and the primary and the oldest tree trifoliate leaves were inoculated after five and seven weeks of exposure. Ozone enhanced the senescence-related injury only in Pros. The number of lesions was not influenced by ozone for either cultivar, conidial suspension or inoculation date. Lesion expansion after inoculation with mycelium was generally reduced in exposed plants. Thus, contrasting effects of ozone on the susceptibility of bean leaves to B. cinerea were observed depending on the cultivar, the conidial suspension, the disease parameter and the ozone exposure pattern. In extrapolating the laboratory results to the field, it is suggested that episodic and chronic exposures to ambient ozone are of minor importance in increasing the susceptibility of bean leaves to B. cinerea.

Journal Article↗
PubMed1995

Changes in pigment concentration and composition in Norway spruce induced by long-term exposure to low levels of ozone.

Rametes of Norway spruce were fumigated with 30 ppb (nl litre(-1)) ozone above ambient level for 4 years in open-top chambers. They were grown under different light conditions, because some of the chambers received approximately 10% less light than the others. Samples from three age classes were analyzed for nitrogen and pigments using HPLC. It could be demonstrated that the ozone treatment reduced the concentration of chlorophyll (a) and (b), alpha- and beta-carotene, but increased the concentration of antheraxanthin. A significant decrease was found for the violaxanthin/antheraxanthin ratio following the ozone treatment. The concentration of all the pigments and of nitrogen were significantly related to the age classes, and a similar relationship was found for the light levels, except for antheraxanthin and total carotenoids. The ratio of chlorophyll a/b was only significantly related to the age classes.

Journal Article↗
PubMed1995

Fatty acids and ultrastructure of ozone-exposed Aleppo pine (Pinus halepensis Mill.) needles.

Fifteen or 18-month-old Aleppo pine seedlings were fumigated with different concentrations and doses of ozone over a period of 2-16 days in controlled-environmental growth chambers. The total fatty acid content and ultrastructure of the current year needles were subsequently analysed. In acute, high concentration exposures, significant reductions in the levels of linolenic acid were detected. Increases in myristic or palmitic acid were common in needles exposed to lower concentrations of ozone. Ultrastructural studies revealed reductions in chloroplast size and a darkening of stroma at low ozone exposures while at high concentrations disruption of the chloroplast membranes was also identified.

Journal Article↗
PubMed1996

Evidence that plant varieties respond differently to NO2 pollution as indicated by resistance to insect herbivores.

The effects of NO(2) pollution on the performance of aphids feeding on different bean varieties were investigated by fumigation experiments. The susceptibility of the different genotypes dramatically changed as the concentration of atmospheric pollutant was increased. The direction of change was not constant between varieties. Our data suggest that resistance or susceptibility of a plant variety to insect herbivory can be significantly altered when subjected to pollutant stress, thus indicating that it may be difficult to predict the susceptibility of host plants in a polluted atmosphere.

Journal Article↗
PubMed1986

Incapacitation and treatment of rats exposed to a lethal dose of sulfuryl fluoride.

Rats exposed to 4000 ppm sulfuryl fluoride (VIKANE gas fumigant, SO2F2) were incapacitated within 45 min and died within several hours after exposure. Exposure to higher concentrations resulted in a shorter time to incapacitation and death occurred within minutes. Treatment with calcium gluconate before exposure to 4000 ppm SO2F2 for 45 min resulted in 80% survival. However, calcium gluconate did not alleviate SO2F2-induced convulsions. Administration of phenobarbital before or after exposure to 4000 ppm SO2F2 for 45 min effectively reduced the frequency and severity of convulsions and resulted in survival of all animals. Exposure of rats to 10,000 ppm SO2F2 for 15 min followed by treatment with phenobarbital reduced the frequency of convulsions and delayed death, but did not prevent death. Diazepam was less effective than phenobarbital while diphenylhydantoin had no beneficial effect and, in fact, made the convulsions more severe and longer in duration. The results of this study indicate that phenobarbital was effective in ameliorating the acute toxic effects of an overexposure to SO2F2 in rats.

Animals↗
PubMed1987

Evaluation of the effects of inhalation exposure to 1,3-dichloropropene on fetal development in rats and rabbits.

1,3-Dichloropropene (DCP), which has found widespread use as a soil fumigant, was evaluated for its potential effects on embryonal and fetal development in rats and rabbits. Pregnant Fischer 344 rats and New Zealand White rabbits were exposed to 0, 20, 60, or 120 ppm of 1,3-dichloropropene for 6 hr/day during gestation Days 6-15 (rats) or 6-18 (rabbits). Exposure-related decreases in maternal weight gain and feed consumption were observed in rats at all treatment levels. Decreased weight gain was also observed among rabbits at 60 and 120 ppm. A slight, but statistically significant, increase in the incidence of delayed ossification of the vertebral centra in rats exposed in utero to 120 ppm of DCP was considered of little toxicologic significance in light of the maternal toxicity observed at this exposure concentration. No evidence of a teratogenic or embryotoxic response was observed in either species at any exposure level tested. Thus, it was concluded that DCP was not teratogenic at exposure levels up to 120 ppm in either rats or rabbits.

Aerosols↗
PubMed1988

Subchronic toxicity of inhaled technical grade 1,3-dichloropropene in rats and mice.

In order to provide a comprehensive subchronic inhalation toxicity study of the soil fumigant, technical grade 1,3-dichloropropene (DCPT), male and female Fischer 344 rats and B6C3F1 mice were exposed to 0, 10, 30, 90, or 150 ppm DCPT vapors 6 hr/day, 5 days/week for 13 weeks. The primary target tissues of inhaled DCPT were identified as the nasal mucosa of both sexes of rats and mice, and the urinary bladder of female mice. In addition, depressed growth rates of all animals exposed to 90 or 150 ppm DCPT (up to 20% in rats and 12% in mice) resulted in a variety of alterations in hematologic and clinical chemistry parameters, and changes in organ weights relative to controls. Nasal mucosal effects consisted of a dose-related slight degenerative effect of nasal olfactory epithelium or a mild hyperplasia of the respiratory epithelium or both in all animals exposed to 90 or 150 ppm and 2 of 10 male rats exposed to 30 ppm DCPT. Some focal areas of respiratory metaplasia were also noted in high exposure group mice. Urinary bladder effects consisted of a diffuse, moderate hyperplasia of the transitional epithelium in female mice exposed to 90 or 150 ppm DCPT. No treatment-related effects were observed in rats or mice exposed to 10 ppm DCPT vapors.

Administration, Inhalation↗