Simulated Acid Fog Research Articles

Gene response in rice plants treated with continuous fog influenced by pH, was similar to that treated with biotic stress.

BackgroundThroughout Asia, including Japan, rice plants are cultivated in a wide range of areas from lowlands to highlands and are frequently exposed to fog, including acid fog. Some physiological studies have shown that acid fog can be a stress factor for plants. We analyzed the gene expression profiles of rice plants treated with artificially prepared simulated acid fog (SiAF) or simulated neutral fog (SiNF) for 1 or 7 days.ResultsMicroarray analysis results suggested that both the SiAF and the SiNF treatments induced the expression of genes involved in the defense and stress responses in rice plants. Induction of such genes was detected in plants treated with SiAF for 1 day, and the number of induced genes increased in plants treated with SiAF for 7 days. The genes for defense and stress responses were also induced by SiNF for 7 days, although they were not induced by SiNF for 1 day. The gene expression profiles of the SiAF-treated and the SiNF-treated plants were compared to those of plants treated with other stress factors. The comparison revealed that both SiAF and SiNF treatments have similar effects to biotic stresses and ozone stress. The genes encoding NADPH oxidase and germin, which function in apoplasts, were also induced by SiAF, SiNF and biotic stresses.ConclusionsThese findings suggest that both the SiAF and the SiNF treatments may result in oxidative stress through the apoplastic production of reactive oxygen species.

Effects of acidic fog and ozone on the growth and physiological functions of Fagus crenata saplings

The effects of simulated acid fog (SAF) and ozone (O3) stress on the growth and physiology of beech (Fagus crenata) saplings were investigated. Three-year-old beech saplings were exposed to SAFs of pH 3 and pH 5 (control) during May 2007 to July 2008. In each SAF treatment group, half of the saplings were exposed to 60 ppb of O3 during September 2007 to July 2008. In comparison to the control saplings, those from the pH 3 treatment had lower total plant biomasses, epicuticular wax amounts, Ca2+ concentrations in their leaves, and lower starch concentrations in their leaves and roots. The effect of O3 was significant only for the starch concentration in the roots, but the O3 exposure also negatively affected the growth and physiology of beech saplings. Results show that acid fog exerts various severe effects, and that both chronic acid fog and O3 exposure suppressed the physiological functions of beech saplings.

Effect of simulated acid fog on membrane-bound calcium (mCa) in fir (Abies firma) and cedar (Cryptomeria japonica) mesophyll cells

The decline of virgin fir (Abies firma) forest at Mt. Oyama has been reported. Related field observations suggest that high acidity fog is linked with its decline. However, cedar (Cryptomeria japonica) in the same area shows no symptoms of decline. For assessing effects of acid fog on membrane-bound calcium (mCa) of the leaf mesophyll cells, 9-year-old seedlings of fir (Abies firma) and 8-year-old seedlings of cedar (Cryptomeria japonica) were exposed twice a week to simulated acid fog (SAF at pH 3 with pH 5 as control) for 2 h per day in a chamber during May–December 2007 (except August). Current and 1-year-old needles were collected from seedlings and analyzed at 1-month intervals. For current-year needles of fir, mCa levels in cells exposed to SAF at pH 3 were significantly lower than in cells exposed to pH 5, especially during September 2007–March 2008. In contrast, it is noteworthy that mCa levels of cedar were maintained as virtually constant irrespective of SAF acidity, indicating that fir is more sensitive to acid fog than is cedar. Based on these results, mCa loss by acid fog might also be caused in the declining virgin fir forest at Mt. Oyama.

Leaching of cell wall components caused by acid deposition on fir needles and trees

Virgin fir forests have been declining since the 1960s at Mt. Oyama, which is located at the eastern edge of the Tanzawa Mountains and adjacent to the Kanto plain in Japan. An acid fog frequently occurs in the mountains. We collected throughfall and stemflow under fir trees and rainfall every week during January–December 2004 at Mt. Oyama to clarify the influence of acid fog on the decline of fir ( Abies firma) needles. In relation to throughfall and stemflow, d-mannose, d-galactose, and d-glucose are the major neutral sugar components; only d-glucose is a major component of rainfall. The correlation coefficient between the total neutral sugars and uronic acid (as d-galacturonic acid), which is a key component of the cross-linking between pectic polysaccharides, was high except for rainfall. The leached amount of calcium ion, neutral sugars, uronic acid, and boron is related to the nitrate ion concentration in throughfall. Results of a laboratory exposure experiment using artificial fog water simulating the average composition of fog water observed at Mt. Oyama (simulated acid fog: SAF) on the fir seedling needles also shows a large leaching of these components from the cell walls of fir needles. The leaching amount increased concomitantly with decreasing pH of the SAF solution. We also observed that a dimeric rhamnogalacturonan II-borate complex (dRG-II-B) that exists in the cell wall as pectic polysaccharide was converted to monomeric RG-II (mRG-II) by the leaching of calcium ion and boron. Results not only of field observations but also those of laboratory experiments indicate a large effect of acid depositions on fir needles.

Growth and physiological responses of beech seedlings to long-term exposure of acid fog

Seven-year-old beech seedlings ( Fagus crenata) were exposed to simulated acid fog (SAF) at pH 3 or pH 5 (as control) prepared by adding a 2:1:1 mixture (molar ratio) of nitric acid, ammonium sulfate, and sodium chloride to ultrapure water from September 2004 to July 2006 in a mobile fog chamber. In comparison to control seedlings, seedlings from the pH 3 treatment displayed inferior plant height, stem diameter, number of leaves, and dry matter production, but greater leaf area. Furthermore, exposure to SAF induced early falling of leaves with a nearly two-times-greater normalized leaf number index than control. The starch levels in the stems of seedlings of the pH 3 treatment were much lower than those of control at the harvest. The acid fog-induced reduction of the starch accumulation is considered to occur mainly because of fewer leaves during the growth phase. Results of laboratory experiments demonstrate that the amount of base cations leached from the beech leaves increased with decreasing pH of SAF; the leaching amount of calcium ion from the beech was high relative to that of conifers such as fir and cedar. These results imply that chronic acid fog exposure suppresses growth and physiological activity of beech seedlings.

Effects of complex stress of chronic acid fog exposure with rhizosphere aluminum on nutrient status in Abies firma seedlings

We exposed momi fir (Abies firma Sieb. et Zucc.) seedlings to simulated acid fog of pH 3.0 for about 3 years (from July 1999). During the last year of acid fog exposure, half of the seedlings were subjected to rhizosphere Al stress (complex stress) and the nutrient status of seedlings was determined. Chronic acid fog exposure decreased Fe and Zn concentrations in current-year and 1-year needles, and Al in 1-year needles, but had little effect on major element concentrations. Aluminum treatment had a broad impact on nutrient status in fine roots and needles. In fine roots, increases in Al and Cu concentrations and decreases in B, Mn, and Zn concentrations were observed. In 1-year needles, Al treatment increased Al, B, and Mn concentrations and decreased Cu concentration. The complex effect of acid fog with aluminum on nutrient status was relatively slight. These results show that changes in nutrient status under chronic acid fog exposure and/or Al stress are induced before the decline of photosynthesis in momi fir seedlings, mainly due to Al stress.

Effects of chronic acid fog exposure with soil acidification or nitrogen loading on nutrient status in Abies firma seedlings

To clarify the nutrient status in momi fir (Abies firma Sieb. et Zucc.) seedlings under complex stress conditions of acid fog with soil acidification or nitrogen loading, we exposed seedling shoots to simulated acid fog (pH 3) and simultaneously loaded the soil with acid or excess nitrogen for 17 months. Proton and nitrogen loading reduced K concentration in soil, but these treatments had little effect on the nutrient status of fine roots in momi fir seedlings. Acid fog exposure resulted in reduced concentrations of Mg, Al, and Fe in current-year needles and Mg, Al, Cu, Fe, and Zn in 1-year-old needles. The complex effects of acid fog exposure with proton or nitrogen loading on nutrient status were relatively slight. However, elements such as Al and Cu notably reflect the effects of proton loading. These results show that the nutrient status of trace elements, rather than major elements, in needles of momi fir seedlings is sensitive to exposure to acid fog or proton loading.

Response of gas exchange rates in Abies firma seedlings to various additional stresses under chronic acid fog stress

In order to clarify the chronic influence of acid fog on the gas exchange rates of momi fir (Abies firma Sieb. et Zucc.) trees, we exposed them to simulated acid fog (pH 3) for 3 years. The composition of the acid fog was similar to that observed in a region where momi fir trees have been declining, and it contained organic acids. We then treated the firs with various additional stresses, such as drought, low temperature, fine root cutting, ozone exposure, soil acidification, nitrogen load, and rhizosphere aluminum stress. Under chronic exposure to acid fog, the momi fir seedlings exhibited a pattern of stomatal behavior whereby they excessively opened in summer and closed in winter. Furthermore, the stomata of these seedlings tended to open during drought stress, and their needles were visibly injured after ozone exposure. The net photosynthesis rates of the seedlings exposed to acid fog were regulated by their stomatal aperture, rather than directly by acid fog. These results suggest that acid fog exposure disturbs the control of stomatal function in the momi fir seedlings. In addition, we found that chronic acid fog exposure suppressed the decrease in net photosynthesis rate, due to its nitrogen load.

Long-Term Effects of Simulated Acid Fog on Visible Injury, Growth, Chlorophyll and Nitrogen Content of Japanese Cedar, Red Pine and Beech Seedlings

Long-Term Effects of Simulated Acid Fog on Visible Injury, Growth, Chlorophyll and Nitrogen Content of Japanese Cedar, Red Pine and Beech Seedlings

Acid Fog Removes Calcium and Boron from Fir Tree: One of the Possible Causes of Forest Decline

We have observed acid fog in Mt. Oyama adjacent to the Kanto Plains in Japan, where acid fog under pH 3 has been frequently observed and natural fir forest (Abies firma) has been declining. We applied the simulated acid fog to the needles of fir twigs and the treatment removed calcium, boron, and cell-wall acidic sugars from the needles. We also observed high contents of calcium, boron, and acidic sugars in throughfall collected under the declining forest canopy. Ca++ and Mg++ ion leach via ion-exchange with major cations of fog-water and the amount of leached boron increased with the increase in the concentration of leached Ca++. The deficiency of calcium and boron by leaching could be one of the main causes of decline of the fir forest.

Severe leaching of calcium ions from fir needles caused by acid fog

We have measured the components of the throughfall under fir trees ( Abies firma) in the field around Mt. Oyama, where the forest appears to be declining, for the period 1994–1998. Exposure experiments of a simulated acid fog to fir twigs were performed under field conditions. There was a similarity between the acid response in the field and that in the laboratory. In both studies, the severe leaching of calcium ions from the needle surface was caused by exposure to acid fog. We also applied acid fog to fir seedlings over 1 year and observed a decrease in the growth of the seedlings due to this application in the dormant season. These results suggest that the severe leaching of calcium ions due to acid fog may cause the deficiency of calcium and be responsible for the decline of the fir trees.

Birch foliar responses to simulated acidic fog andSeptoria betulaeinoculations

The effects of simulated acidic fog and inoculation with Septoria betulae Pass. on foliar symptom development and foliar senescence of Betula papyrifera Marsh. and Betula cordifolia Regel seedlings were investigated in 1997 and 1998 under greenhouse conditions. An interactive role may exist between acidic fog events and S. betulae in causing birch foliar browning, a disease reported over the past decade to occur on mature trees growing adjacent to the Bay of Fundy, Canada. Seedlings received applications of simulated fog adjusted to pH 3.2, 4.2, and 5.6 or a no-fog treatment. Inoculation treatments at each fog pH level were accomplished through spray atomization with S. betulae conidial suspensions and by placing naturally infected birch leaves bearing pycnidia of the fungus on plastic nets suspended above seedlings in enclosed chambers. Percent symptomatic leaf area of seedlings inoculated with S. betulae was nearly double that recorded for non-inoculated seedlings. Foliar browning resembled symptoms observed on mature trees in the field. Foliar symptoms were observed on non-inoculated seedlings, with greater severities associated with seedlings exposed to the most acidic fog treatment. Leaf senescence was also greatest for spray-inoculated leaves that had been exposed to the pH 3.2 fog treatment. Pycnidial development was not influenced by the pH of the fog treatments but was greater in all fog treatments than in no-fog treatments. Although both acidic fog and S. betulae infection are able to cause symptoms independently, the data suggest that an interactive role may exist in causing birch foliar browning. However, to obtain the same severity of foliar browning as observed on natural forest-grown trees in the Bay of Fundy region, S. betulae must be present.

Birch foliar responses to simulated acidic fog and <i>Septoria betulae</i> inoculations

Birch foliar responses to simulated acidic fog and <i>Septoria betulae</i> inoculations

Effect of simulated acid fog on needles of fir seedlings

Fir seedlings ( Abies firma) were treated with simulated acid fog from September 1992 to April 1995. The simulated acid fog was at pH 3 and consisted of 1 mM nitric acid, 1 mM sodium chloride, and 1 mM ammonium sulfate. In 1993 spring, needles of the seedlings treated with the simulated acid fog became greener than those of the control, which were treated with pH 5 fog water of one hundredfold diluted solution of pH 3 fog water. However, from June 1993 in the acid-fog-treated seedlings, the needles shed, and the growth in height declined. Many buds with their bearing sprouts died in 1993, and few twig tips put forth new sprouts in the spring of 1994. Other symptoms also developed because of the treatment with the simulated acid fog: the water loss from the needles increased and the needles became susceptible to water stress, the weight per area of the needles decreased, and chlorophyll concentration increased. The results were observational in nature and the data were generated from plants exposed to the atmosphere in Yokohama so that there is a possibility of interaction with other pollutants. The long-term treatment with simulated acid fog at pH 3 induced a decline of fir seedling growth and general well-being, although the data warrant further study of the effects of chronic exposure of acid fog on plant growth.

Trirhabda geminata (Coleoptera: Chrysomelidae) resistance to the direct impact of simulated acidic fog on larval growth and mortality

The direct effects of acidic fog (pH 2·75) upon the mortality and growth of Trirhabda geminata Horn (Coleoptera: Chrysomelidae), the dominant herbivore of the California coastal sage scrub, Encelia farinosa (Compositae: Asteraceae), were evaluated. Although there was a consistent pattern among and between experiments, suggesting that acidic fogs could reduce insect growth and survivorship within the first few days following application of treatments, an exposure to three consecutive, 3-h fogs over a five day period did not significantly affect mortality, biomass gain, or larval growth rate. There are two important implications from this study. First, even the highly acidic fogs found in southern California will have minimal direct effects on T. geminata performance. Second, the impacts on T. geminata biology observed in previous studies were likely mediated by host-plant responses to acidic-fog episodes.

Acidic Fog and Temperature Effects on Stigmatic Receptivity in Two Birch Species

AbstractFactorial assays were performed to determine the effects of simulated acid fog (SAF) and temperature on stigmatic receptivity in two birch species. Excised reproductive branches were sampled from representative individuals of mountain paper birch (Betula cordifolia Regel.) and paper birch (Betula papyrifera Marsh.) in populations adjacent to the Bay of Fundy, New Brunswick, Canada. Since 1979 these trees have exhibited branch dieback in association with abnormal foliar browning symptoms. This browning has been linked with acidity and nitrate deposited by fog, which is frequent in the area. In general, experimental results indicated that pollen germination increased with temperature, but pH effects were less obvious. Similarly, pollen tube growth responded positively to temperature and was little affected by fog acidity. ANOVA tests indicated a significant difference (P < 0.05) between species in their pollen germination response only at 12°C, and not at the other three temperatures tested. For pollen tube growth, significant differences between species (P < 0.05) were demonstrated at 12 and 22°C. A significant pH effect was demonstrated at 27°C for germination, while pH effects on tube growth were significant at 27 and 12°C (P < 0.01). A response surface regression analysis indicated that acidity significantly affected pollen germination in mountain paper birch (P < 0.001) but not in paper birch. Temperature was not a significant factor for in vivo pollen germination in either species. For pollen tube growth, however, temperature was more important than pH and produced highly significant effects in both species (P < 0.001). Acidity was also a significant factor in pollen tube growth for paper birch.

Effects of acid fog on cuticular permeability and cation leaching in holly ( Ilex aquifolium)

Young holly plants were exposed for up to 9 months to simulated acid fog at a chemical composition, pH range and deposition pattern consistent with those reported for an elevated site in northwest England. Plants were exposed to acid fog at pH 5.6 (control), pH 4.5, pH 3.5 and pH 2.5. Water permeability was higher in enzyme-isolated cuticles from low-pH leaves. Foliar leaching amounts of Mg 2+, Ca 2+ were higher in leaves exposed to lower pH acid fog. Similar effects for K + leaching rates were not significant. Increases in cuticular permeability and cation leaching were not accompanied by any observable changes in surface structure, as revealed by studies with wettability and extractable wax. It is suggested that any changes in cuticular functioning were the result of alterations to the intracuticular rather than epicuticular structure.

Effect of simulated acidic fog on carbohydrate leaching, CO 2 assimilation and development of damage symptoms in young spruce trees ( Picea abies L. Karst)

The effect of acidic fog on carbohydrate leaching, CO 2 assimilation, carbohydrate status, and cuticle development of young spruce trees was studied in a greenhouse experiment. Over a period of 9 weeks the plants were subjected to fog application on 27 occasions. In one treatment trees were exposed to a fog of pH 2.75 (acidic fog) and in one treatment to a fog of pH 5.00 (control treatment). Leaching rates for carbohydrates (sucrose, glucose, fructose) were significantly higher in the acidic fog treatment than in the control treatment. The total amount of carbohydrates leached out of the trees by acidic fog, however, was low and amounted to less than 1% of the non-structural carbohydrates in the needles. Trees which had been exposed to acidic fog were not affected in photosynthesis and in the distribution of photosynthates to various plant parts. In the younger needles significantly lower concentrations of starch, glucose, and fructose were found in the treatment with acidic fog as compared with the control plants. Also the starch concentration in the roots of the control plants was significantly higher than that in the plants exposed to acidic fog. These findings are suggestive of a stress situation with a high energy demand. Application of acidic fog resulted in a disintegration of the epicuticular wax layer and of the epistomatal wax props. In the treatment with acidic fog some needles of the current year turned reddish-brown and some older needles became chlorotic and later brown. These needles were shed to a large degree. Needle loss of the trees exposed to acidic fog was significantly higher than that of the control trees.

Injury of Three Ornamental Flower Crops from Simulated Acidic Fog

Response of carnation and chrysanthemum to acidic fog was similar. The most severe injury occurred near pH 1.8-2.0 and no injury was observed above approximately pH 3.8-4.0. Injury of zinnia was also most severe at pH 2.0 but was approximately 40% less severe than that of carnation or chrysanthemum at this acidity. All flowers tested were injured at ambient acidity levels measured in many of the primary cut flower production areas of California

Elemental leaching from quercus ilex L. in response to simulated acidic fog

Quercus ilex L. seedlings were intermittently exposed to simulated acidic and non-acidic fogs in 6-hr events for 16 times. After a 1-mo break, treatments were carried out again for a 5 day period. Strong acidity neutralization, weak acidity release and cation leaching from foliage and stem were determined. Leaching of Al, Cu, Mn, Fe, Cd, Pb, Ca, Mg, and K increased in response to acid treatment. This effect was less marked for Na. A positive correlation between H− uptake and cation leaching was found. Cationic release and neutralization of strong acidity increased after breaks in acid treatment, but this faculty and the amount of leached cations and neutralized acidity decreased with time. The stem showed a higher cation loss and higher buffer capacity than the leaves.