Effects of acid mist on mature grafts of Sitka spruce. Part I. Frost hardiness and foliar nutrient concentrations

Mature grafts of five clones of Sitka spruce (Picea sitchensis Bong. Sarg.) were exposed to simulated acid mist composed of an equimolar mixture of sulphuric acid and ammonium nitrate at pH 2.5 and pH 5.0 in open-top chambers from May to November 1991. Treatments were applied on consecutive days, four times a week. The pH 2.5 treatment provided an overall dose three times higher than that received by forests in upland areas of Britain. Frost hardiness was assessed in November by freezing detached current year shoots at a range of temperatures and assessing the rate of electrolyte leakage Foliar nutrient concentrations were determined on the same shoots. Acid mist at pH 2.5 significantly reduced frost hardiness in four of the five clones; the temperature causing 50% shoot death (LT50) was increased by 0 to 7 degrees C. The clones varied in their level of hardiness, one clone being exceptionally frost sensitive. The frost hardiness of the frost sensitive clone was found to be less perturbed by acid mist than the hardiness of the more frost resistant clones. Mature grafts showed a smaller reduction in hardiness at an equivalent dose than that found previously with Sitka spruce seedlings. Compared with seedlings, grafts had lower absolute concentrations of foliar sulphur. Exposure to acid mist at pH 2.5 increased %S in current year foliage by <0.05% compared with absolute increases of more than 0.10% in current year foliage of seedlings. We conclude that the effect of acid mist on frost hardiness is likely to be less on mature trees than on seedlings and that the increased frost risk to mature trees of Sitka spruce from occult deposition alone is small.     

Biochemical response of Norway spruce (Picea abies (L.) Karst.) towards 14-month exposure to ozone and acid mist: effects on amino acid, glutathione and polyamine titers

Two clones of Norway spruce were exposed to elevated ozone levels (100 microg m(-3) with episodes of 130-360 microg m(-3)) in combination with acidic mist (pH 3.0) for two vegetation periods. The plants did not exhibit any visible injury, but levels of several amino acids and polyamines were altered in comparison with control plants (50 microg m(-3) ozone, mist of pH 5.6), the changes being pronounced in clone 14. Total free amino acids as well as methionine titers were increased in clone 14. Asparagine was significantly increased in clone 11 and less so in clone 14. Arginine, which comprised more than 50% of the free amino acids in spruce needles, was not changed by the exposure regime applied. Reduced glutathione was significantly increased in all clones/soil/needle age combinations (average increase 50%). Free soluble putrescine was enhanced by 50-200% in clone 14, but remained unchanged in clone 11. Conjugated putrescine was significantly, and conjugated spermidime was slightly, increased in both clones, whereas other polyamines did not responde to the treatment.     

Mineral and nutrient supply, content and leaching in Norway spruce exposed for 14 months to ozone and acid mist

The nutrient contents of an acid and a calcareous soil, as well as the foliar contents of four clones of Norway spruce grown on these soils, were evaluated during a 14-month exposure to low level ozone (100 microg m(-3) + peaks between 130 and 360 microg m(-3)) plus acid mist (pH 3.0). Whilst distinct differences could be established between and within clones depending on soil types and genotype, only few pollutant-related effects were observed. Leaching losses from foliage were generally low compared to field studies. The data obtained with young trees in an artificial environment do not support the hypothesis that enhanced leaching from foliage may contribute to nutrient deficiencies in mature stands of Norway spruce.     

Acid mist and ozone effects on the leaf chemistry of two western conifer species

Seedlings of Jeffrey pine (Pinus jeffreyi) and giant sequoia (Sequoiadendron gigantea) were more susceptible to leaf chemical changes following exposure to acid mist (pH 3.4-2.0) or acid mist/ozone combinations, than to ozone alone (0.1-0.2 microl/litre), when plants were exposed to alternating doses of these pollutants for 6-9 weeks. Under acid mist treatment, leaves exhibited higher levels of nitrogen and sulfur, two elements applied in acid mist. In addition, levels of foliar sodium, and, in the case of giant sequia, potassium, as well, increased under acid mist treatment. Iron and manganese were also mobilized, resulting in significant increases in these elements in pine, and decreases in manganese in giant sequoia foliage. The acid treatment also reduced chlorophyll b concentrations in pine, and, to a less significant extent, in giant sequoia. Calcium, magnesium, barium and strontium were differentially accumulated in giant sequoia compared to Jeffrey pine. Under acid mist treatment, all of these elements (except strontium) declined in concentration in giant sequoia, with calcium showing the most significant trend. The more extensive changes in leaf chemistry induced by acid mist are consistent with earlier observations of significant changes in spectral reflectance of these seedlings after 3 weeks of fumigation. Limited foliage samples collected from these two species in 1985 and 1986 in Sequoia/Kings Canyon National Parks in the southern Sierra Nevada do not in themselves indicate any clearcut or severe effects of ozone alone on leaf chemistry of these species, but a mild influence of nitrate-laden acid deposition, possibly in combination with ozone, is consistent with the rise in nitrogen and lignin levels in Jeffrey pine on sites observed to have moderate visible injury symptoms. No firm conclusions about effects of pollutants on leaf chemistry in these field sites is possible without further study.     

Effects of low-level long-term ozone fumigation and acid mist on photosynthesis and stomata of clonal Norway spruce (Picea abies (L.) Karst.)

Four clones of 3-year-old Norway spruce (Picea abies (L.) Karst.), grown on two soils, were from July 1986 to September 1987 exposed to ozone fumigation (50 microg m(-3) as a control, 100 microg m(-3) plus peaks between 130 and 360 microg m(-3) as treatment) and acid mist of pH 3.0 (versus mist pH 5.6 in the control). Climatic conditions, identical for both control and treatment, followed a diurnal and seasonal pattern characteristic of medium high altitudes of the Bavarian Forest, an area affected by the new-type forest decline. Gas-exchange measurements were carried out on the plants from December 1986 until the end of the 14-month's exposure using a series of climate-controlled minicuvettes. ANOVA of the four clones investigated towards the end of the experiment gave hints of a treatment-related depression of the photosynthetic capacity of the previous year's needles (age-class 1986). Within this age-class only one of the clones (11) showed a significant treatment effect, indicating an age-class dependence and a genetic influence of the treatment-related depression of the photosynthetic capacity. The current year's flush was not impaired through the ozone and acid mist exposure. Analysis also revealed clear effects of soil, clone and needle age on photosynthetic parameters.     

Studies on the Effects of Saline Aerosols of Cooling Tower Origin on Plants

A research program was undertaken to develop information that could be used to estimate the risk of adverse effects of saline cooling tower drift on native and cultivated flora in the Indian Point, New York area. Eleven species of woody plants were exposed at 85 % relative humidity to a saline mist with 95% of the particles between 50 and 150 nm in diameter. Three biological factors—stage of development, species, and phenotype—determined the susceptibility of plants to saline aerosols when the occurrence of any lesion on the foliage was used as a measure of response. The effects of stage of development on the incidence and severity of foliar lesions depended upon the kind of plant. In deciduous woody species, the youngest leaves were most susceptible, but in conifers, the year-old needles were most susceptible. Canadian hemlock was the most susceptible species and witch hazel was the least susceptible. Median effective doses for these two species, although undetermined, could be more than 100-fold different (less than 2.4, the lowest used, and greater than 264 ng CI cm^-2, respectively). Other species, ranked in decreasing order of susceptibility were: white ash, white flowering dogwood, forsythia, chestnut oak, silk tree, black locust, red maple, eastern white pine, and golden rain free. Phenofypic variation within a species was not so great—within a 10 to 20-fold increase in dose the incidence of injury went from 0 to 100%. Exposures with bush bean showed that the relative humidity (RH) during or after the exposure period affected the incidence of saline induced foliar injury. A change from 50 to 85% RH doubled the effectiveness of the saline mist. It was also found that compared to particles between 50 and 150 jum in diameter, an increase in the fraction of particles above 150 /xm increased the toxicity of the mist.     

Cytological observations on spruce needles after prolonged treatment with ozone and acid mist

Light and electron microscopic studies of four clones of 5-year-old Picea abies trees subjected to ozone and acid mist treatment showed, that: (1) Clones respond differently to the treatment, with clone 14 the most sensitive clone. (2) Main effects were observed in the mesophyll; the vascular strand showed minor cellular changes. (3) Needle shape and ratio of intercellular area to cross section was clone- age-dependent, with a clear increase in intercellular space associated with the treatment (clone 14 and 11 only). (4) Accumulation of tannins in vacuoles was clone-specific. (5) Strong starch formation was found in all samples; in clones 14 and 133 this formation was enhanced by the treatment in older needles, if number of starch grains per cell was calculated. (6) The accumulation of plastoglobules in plastids depended on clone and age, with the older needles containing more globules. In clones 11 and 133, the treatment led to an increase in the number of plastoglobules. (7) Grana stacking in all clones and both needle ages subjected to ozone and acid mist was significantly reduced. The observed changes in the ultrastructure of needle tissue are comparable to those found in field investigations with similar conditions, or phytotron studies evaluating pollution effects on spruce trees.     

Clone and soil effects on the growth of young Norway spruce during 14 months exposure to ozone plus acid mist

Five clones of 3-year old Norway spruce (Picea abies [L.] Karst), planted in a soil from the Bavarian Forest (pH 4.4) or a soil from the Calcareous Bavarian Alps (pH 6.9), were exposed for two successive vegetation periods, in closed environmental chambers, to a pollution treatment consisting of acidic mist (pH 3.0) plus ozone levels of 100 microg m(-3) with episodes of 130-360 microg m(-3); control trees were exposed to mist of pH 5.6 and ozone levels of 50 microg m(-3). Climatic and pollution protocols followed the diurnal and seasonal pattern characteristic for the Inner Bavarian Forest in Southern Germany, an area affected by the new-type forest decline. Biometric parameters were strongly related to clone and soil. Pollution treatment had a limited effect on only a few growth parameters. The stem diameter growth increment of two clones was reduced by pollution treatment in both soils, a third clone was affected in the acidic soil only. Two other clones were not affected at all. Stem volume increment of three clones, calculated as D(2)H, was reduced by pollution treatment in the neutral soil, a fourth clone was affected in the acidic soil only. Bud break was either delayed (two clones) or accelerated (two other clones) by treatment. Depending on soil and clone, needle yellowing was observed in previous years' needles in both treatment and control trees exposed to increased light intensities. The 'spotted' yellowing was not identical to symptoms found in forest decline areas and was most likely a consequence of nutrient deficiencies during the vegetation period preceding the experiment. The results of this experiment are discussed with regard to field observations and forest productivity. The complex pattern of growth responses resulting from interactions between air pollution, soil and genetic factors is considered to reflect different susceptibilities of trees to air pollutants.     

An assessment of the impact of ambient ozone on field-grown crops in New Jersey using the EDU method: part 1-white potato (Solanum tuberosum)

Six potato cultivars were grown to maturity in field plots in New Brunswick, New Jersey, according to standard commercial practices over a 5-year period. One-half of the plots were given a periodic soil drench of an antioxidant (EDU) which has the capacity to protect foliage against ozone toxicity. Based upon visible foliar injury and total tuber yield, the cultivars Norland and Norchip proved significantly more sensitive to ambient ozone pollution than Green Mountain, Irish Cobbler, Belrus or Superior. When foliar injury was less than 20%, no impact on tuber yield was detected. However, when 75% of the foliage exhibited O(3) toxicity symptoms, tuber yield was reduced 25% and 31%, respectively, in 'Norland' and 'Norchip'. A review of results from studies in the US and Canada utilizing different assessment methodologies provides evidence that ambient ozone causes significant tuber yield reduction in sensitive white potato genotypes when foliar injury exceeds 20 to 40%.     

Growth responses of birch and Sitka spruce exposed to acidified rain

Seedlings of birch and Sitka spruce were grown on a range of British soils for 2 years and exposed to simulated acid rainfall treatments of pHs 5.6, 4.5, 3.5 and 2.5. Both species developed visible leaf injury patterns when exposed to the pH 2.5 treatment. In Sitka spruce this leaf injury was followed by high needle loss during the first winter and greater mortality. Generally, height growth of Sitka spruce was unaffected by treatments, but acid rainfall at pH 2.5 increased the height of birch. Mean height of both species was strongly affected by soil type. Significant soils x treatment effects on the heights of both species indicated that on some soils plant growth responses to the treatments did not fit the general pattern. Hence, while the results indicate that generally ambient acidities of rainfall in the UK are unlikely to adversely affect the growth of birch or Sitka spruce, plants growing on some soils may be susceptible to injury.     

Open-top chamber and field exposure of Sitka spruce to simulated acid mist: a comparison of results

Sitka spruce seedlings grown in pots of compost in open-top chambers (OTCs) or outside, in an agricultural loam soil, in different years, were treated with pH 2.5 acid mist comprising an equimolar solution, of H₂SO₄ and NH₄NO₃ at 1.6 mol m⁻³. The effects of rain, and frequency of acid mist applications on visible injury, nutrition and frost hardiness were evaluated in the OTC experiment. Similar evaluations were undertaken in the field where application frequency was dependent on windspeed, rain and direct sunlight. Rain washing significantly ameliorated the effect of acid mist on frost hardiness in OTCs. In the field experiment there was no effect of acid mist treatment. Increasing the frequency of misting in OTCs for the same exposure exacerbated the detrimental effects of acid mist, causing both visible damage and further increasing the sensitivity of the acid treated trees to freezing temperatures. The results show that the treatment environment can both ameliorate and exacerbate treatment effects.     

Foliar response of black cherry (Prunus serotina) clones to ambient ozone exposure in central Pennsylvania

During late summer of 1996 and 1997 we examined ozone-induced foliar injury in a plantation of 111 black cherry trees (ramets) comprising 15 clones originating from wild ortets growing in the Allegheny National Forest, Pennsylvania, and the Monongahela National Forest, West Virginia. The experimental plantation was a clonal seed orchard in Centre County, Pennsylvania, started in 1971 using ortet buds grafted onto seedling rootstocks of mixed origin. Clones differed significantly in severity of foliar injury symptoms (F=31.83, p<0.001). One clone (R-12) had significantly more foliar injury with >50% leaf area affected than other clones during both years. In contrast, clone R-14, which is from the same area in northcentral Pennsylvania as R-12, exhibited significantly less injury (LAA<6%). Although ambient O(3) concentrations were similar in both years, foliar injury was significantly greater (15.7%) in 1996 than in 1997 (9.9%). This is probably explained by lower stomatal conductance in 1997 caused by drier and hotter weather patterns in June and July of that year. Despite very different weather patterns and overall levels of injury in 1996 and 1997, mean clonal injury was significantly correlated between both years of assessment (r=0.92, p<0.001). Within tree crowns, foliage in lower and inner crown positions was significantly more injured than foliage in upper and exterior crown positions. There was no evidence of geographically based population differences in sensitivity to foliar O(3) injury. On the contrary, results demonstrate that wild genotypes of proximal geographic origin may differ greatly in sensitivity.     

Ozone Injury to Pinus Strobus

In a study of the ozone-induced needle blight of eastern white pine in central New York, acute injuries naturally induced on field trees during a year of relatively low ozone concentrations (1 966) were compared with injuries induced during a year of higher concentrations (1967). Injuries were more frequent and severe and were associated with higher mean ozone concentrations in 1967 than in 1966. Characteristic symptoms were induced on foliage of pine branches exposed to controlled doses of ozone as low as 7 ± 1 pphm for four hours or 3 ± 1 pphm for 48 hours. Such doses were equalled or exceeded two and four times, respectively, in the field during the 1 967 season. Ozone sensitivity of pine needle tissue was increased by fumigation in atmospheres containing water mist. High concentrations of ozone (40-60 pphm) caused general injury of foliage of both ozone-susceptible and resistant trees; the symptoms were unlike those found in the field or caused by fumigation with low concentrations of ozone.     

Are N and S deposition altering the mineral composition of Norway spruce and Scots pine needles in Finland?

Data from a large-scale foliar survey were used to calculate the extent to which N and S deposition determined the mineral composition of Scots pine and Norway spruce needles in Finland. Foliar data were available from 367 needle samples collected on 36 plots sampled almost annually between 1987 and 2000. A literature study of controlled experiments revealed that acidifying deposition mediates increasing N and S concentrations, and decreasing Mg:N and Ca:Al ratios in the needles. When this fingerprint for N and S elevated deposition on tree foliage was observed simultaneously with increased N and S inputs, it was considered sufficient evidence for assuming that acidifying deposition had altered the mineral composition of tree needles on that plot in the given year. Evidence for deposition-induced changes in the mineral composition of tree foliage was calculated on the basis of a simple frequency model. In the late eighties the evidence was found on 43% of the Norway spruce and 27% of Scots pine plots. The proportion of changed needle mineral composition decreased to below 8% for both species in the late nineties.     

Foliar injury in young Betula pendula roth., Salix purpurea L. and Ilex aquifolium L. trees and in propagated Taxus baccata L. shoots exposed to intermittent fog at a range of acidities

The occurrence of various visible symptoms of foliar injury was assessed on a 5-point scale for each of the species. There was a distinct increase in the incidence of most types of injury in plant material which has been exposed to pH 2.5 acid fog. No clear pH-related trend in foliar injury occurred in plants exposed to acid fog at pH 3.5, pH 4.5 and pH 5.6, indicating that a threshold for a range of different types of visible injury may exist between pH 2.5 and pH 3.5 for all four species.     

Foliage responses of spruce trees to long-term low-grade sulfur dioxide deposition

Foliage on spruce trees (Picea rubens Sarg.) growing on dry SO(2) deposition zones (dry SO(2) deposition ranging from 0.5 and 8.5 S kg ha(-1) year(-1)) downwind from a SO(2) emission source was analyzed to assess chronic effects of long-term low-grade SO(2) deposition on net photosynthesis, stomatal conductance, dark respiration, stomatal antechamber wax structures, elemental concentrations in and on foliage (bulk and surficial concentrations), and types of epiphytic fungi that reside in the phylloplane. Elemental distributions on stomatal antechambers, on fungal colonies, and on smooth surfaces between stomates and fungus colonies were determined with a scanning electronic microscope (SEM) by way of X-ray scanning. It was found that net photosynthesis of newly developed spruce foliage (current-year, and 1-year-old) was not significantly affected by the local SO(2) deposition rates. Sulfur dioxide deposition, however, may have contributed to the gradual decrease in net photosynthesis with increasing needle age. Dark respiration rates were significantly higher on foliage taken from high SO(2) deposition zones. Stomatal rod-web structures deteriorated to flakes with increasing needle age and increasing SO(2) deposition. Further inspection of the needle surfaces revealed an increasing abundance of fungal colonies with increasing needle age. Many fungal taxa were isolated and identified. It was found that black yeasts responded positively, and Xylohypha pinicola responded negatively to high rates of SO(2) deposition. Surficial concentrations of elements such as P, S, K, Cl, Ca were about 10 times higher on fungal colonies than on smooth needle surfaces. Surficial Ca contents on 4 or 5-year-old needles decreased with increasing SO(2) deposition, but surficial S concentrations remained the same. In contrast, bulk foliar Ca and S concentrations increased with increasing SO(2) deposition.     

Influence of light fleck and low light on foliar injury and physiological responses of two hybrid poplar clones to ozone

Five-month old hybrid poplar clones NE388 and NE359 were exposed to square-wave 30, 55, and 80 ppb O(3) (8 h/day, 7 day/week) under constant high light (HL) and light fleck (LF) during 28 May-29 June 1999, and exposed to 30 and 55 ppb O(3) under HL, LF, and constant low light (LL) during 22 May-28 June 2000 within Continuously Stirred Tank Reactors (CSTR) in a greenhouse. Ramets of these two hybrid clones received similar total photosynthetically active radiation (PAR) within the LF and LL treatments. Visible foliar symptoms, leaf gas exchange, and growth were measured. More severe O(3) induced foliar symptoms were observed on ramets within the LF and LL treatments than within the HL treatment for both clones. The LF treatment resulted in significantly greater foliar injury than the LL treatment for NE388. The LF and LL treatments generally resulted in lower photosynthetic rates (Pn) for both clones, but did not affect stomatal conductance (g(wv)); therefore, the ratios of g(wv)/Pn and the O(3) uptake/Pn were greatest in plants grown under the LF treatment, followed by those grown under LL treatment; plants grown under HL had the lowest ratios of g(wv)/Pn and O(3) uptake/Pn. Greater ratios of g(wv)/Pn and O(3) uptake/Pn were consistently associated with more severe visible foliar symptoms. The negative impacts of the LF treatment on growth were greater than those of the LL treatment. Results indicate that not only the integral, but also the pattern of photo flux density, may affect carbon gain in plants. Increased foliar injury may be expected under light fleck conditions due to the limited repair capacity as a result of continuity of O(3) uptake while photosynthesis decreases under LL conditions.     

The role of arginine decarboxylase in modulating the sensitivity of barley to ozone

Polyamines (PA) are known to be involved in the areas of plant physiology and biochemistry which are related to the response of a plant to air pollution. This study examines the role of arginine decarboxylase (ADC), an important rate-limiting enzyme in polyamine synthesis, in barley plants exposed to ozone (O(3)). The activity of ADC increased significantly in O(3)-treated leaves when visible injury was hardly apparent. The increase in ADC activity may be a mechanism to increase the PA levels in O(3)-treated leaves and so minimize the damaging effects of O(3). Supporting this, foliar applications of DL-alpha-difluoromethylarginine (DFMA), a specific inhibitor of ADC, prevented the rise in ADC activity and visible injury was considerable on exposure to O(3). This damage was not due to the foliar sprays, as little visible injury was seen in leaves in the O(3)-free controls. The results are discussed in terms of the roles of PA in conferring O(3) resistance in plants.     

Ozone exposure thresholds and foliar injury on forest plants in Switzerland

Canton Ticino in southern Switzerland is exposed to some of the highest concentrations of tropospheric ozone in Europe. During recent field surveys in Canton Ticino, foliar symptoms identical to those caused by ozone have been documented on native tree and shrub species. In Europe, the critical ozone level for forest trees has been defined at an AOT40 of 10 ppm.h O3 (10 ppm.h accumulated exposure of ozone over a threshold of 40 ppb) during daylight hours over a six-month growing season. The objective of this study was to determine the amount of ambient ozone required to induce visible foliar symptoms on various forest plant species in southern Switzerland. Species were grown within eight open-top chambers and four open plots at the Vivaio Lattecaldo Cantonal Forest Nursery in Ticino, Switzerland. Species differed significantly in terms of the ppb.h exposures needed to cause visible symptoms. The most to least symptomatic species grown within open-plots in this study rank as Prunus serotina, Salix viminalis, Vibrnum lantana, Rhamnus cathartica, Betula pendula, Rumex obtusifolius, Sambucus racemosa, Morus nigra, Prunus avium, Fraxinus excelsior, Rhamnus frangula, Alnus viridis, Fagus sylvatica and Acer pseudoplatanus. Similar rankings were obtained in the non-filtered chamber plots. The ranking of species sensitivity closely follows AOT values for the occurrence of initial symptoms and symptom progression across the remainder of the exposure season. Species that first showed evidence of foliar injury also demonstrated the most sensitivity throughout the growing season, with symptoms rapidly advancing over ca. 25-30% of the total plant leaf surfaces by the end of the observation period. Conversely, those species that developed symptoms later in the season had far less total injury to plant foliage by the end of the observation period (1.5 to < 5% total leaf area injured). The current European ambient ozone standard may be insufficient to protect native plant species from visible foliar injury, and many more native species may be sensitive to ozone-induced foliar injury than are currently known.     

The effects of excess nitrogen deposition on young Norway spruce trees. Part II the vegetation

The effects of wet-deposited nitrogen on soil acidification and the health of Norway spruce were investigated in a pot experiment using an open-air spray/drip system. Nitrogen was applied as ammonium ((NH(4))(2)SO(4)) or nitrate (HNO(3)/NaNO(3)) in simulated rain to either the soil or the foliage. Symptoms of forest decline as observed in the field were not reproduced, and there was no evidence of direct toxicity. Treatments did, however, have significant effects on tree nutrition. Both NH(+)(4) and NO(-)(3) treatment applied to the foliage lowered foliar K concentrations. NH(+)(4) to a greater extent. Soil-applied NH(+)(4) reduced foliar Mg concentrations and increased foliar Al and Fe. Soil-applied NO(-)(3) significantly reduced foliar P concentrations, and at high doses prevented the alleviation of P deficiency by fertiliser. These effects could be important in some field situations. Ammonium deposition is predicted to be more damaging than nitrate deposition, although the latter may be critical for forests where P status is marginal, such as in parts of the British uplands.