Diagnostic parameters for selecting against novel spruce (Picea abies) decline: IV. Response of photosynthesis and transpiration to SO2+NO2 exposures

The dose- and time-response effects of 3 days of 6 h day-time sequential exposures to NO₂, SO₂ and SO₂+NO₂ of 0.45–1.81 μl l⁻¹ (ppm) SO₂ and 1.50–7.65 μl l⁻¹ NO₂ on photosynthesis, transpiration and dark respiration were examined for nine Carpatho-Ukrainian half-sib families and a population from the GFR ('Westerhof') of Norway spruce [ Piecea abies (L.) Karst.], all in their 5th growing season.
SO₂+NO₂ inhibited photosynthesis and transpiration and stimulated dark respiration more than SO₂ alone. SO₂ and SO₂+NO₂ at the lowest concentrations inhibited night transpiration, but increased it at the highest concentration, the strongest effects being obtained with combined exposures. Photosynthesis of the different half-sib families was affected significantly differently by SO₂+NO₂ exposures. NO₂ alone had no effects.
Sensitivity to transpiration decline correlated negatively with branch density. Height of trees correlated postitively with decline sensitivity in the seed orchard. The distribution of photosynthesis and transpiration sensitivities over all tested half-sib families correlated negatively with the distribution of decline sensitivity of their parents in a rural Danish seed orchard. The relative photosynthesis and transpiration sensitivities may thus serve as diagnostic parameters for selecting against novel spruce decline.     

THE COMBINED EFFECTS OF LOW TEMPERATURE AND SO2+NO2 POLLUTION ON THE NEW SEASON'S GROWTH AND WATER RELATIONS OF PICEA SITCHENSIS

Picea sitchensis (Bong.) Carr. seedlings were exposed to SO₂, NO₂ and SO₂+ NO₂ during dormancy in controlled environments, and were taken to night temperatures of 4, 0, −5, −10 and −15 °C in a freezer. Conditions in the freezer were carefully monitored during the low–temperature treatments. In two experiments, different photoenvironments and temperature regimes were imposed prior to the cold treatments, and different effects were observed. In the first, only limited frost hardiness was achieved and night temperatures of −15 °C were lethal. Temperatures of −5 and − 10 °C led to poor survival of lateral buds, particularly in plants exposed to 45 ppb SO₂. The poor bud break in plants exposed to SO₂ and to − 5 °C resulted in a loss of the effectiveness of this temperature as a chill requirement. Pressure-volume analysis showed that the shoots of plants exposed to NO₂ had greater elasticity (lower elastic moduli, e), so that loss of turgor occurred at lower relative water contents. In contrast, a hardening period (2 weeks in night/day temperatures of 3/10 °C and 8 h days at 50 μmol m⁻² s⁻¹ PAR) gave decreased elasticity and lower solute potentials of spruce shoots. In the second experiment, exposure to 30 ppb SO₂ and SO₂+ NO₂ led to slight, but consistent, increases in frost injury to the needles of plants frozen to − 5 and − 10 °C. The results suggest that the main interaction of low temperatures and winter pollutants may be on bud survival rather than on needle damage, but that effects are subtle, only occurring with certain combinations of pollutant dose and cold treatment.     

NO2‐induced nitrate reductase activity in needles of Norway spruce (Picea abies) under laboratory and field conditions

The induction of activity of the enzyme nitrate reductase (NR, EC 1.6.6.1, 1.6.6.2) in needles of Norway spruce ( Picea abies [L.] Karst.) by nitrogen dioxide (NO₂) was studied under laboratory and field conditions. In fumigation chambers an increase in nitrate reductase activity (NRA) was detected 4 h after the start of the NO₂ treatment. During the first 2 days with 100 µg NO₂ m⁻³, NRA reached a constant level and did not change during the following 4 days. At the same level of NO₂, NRA was lower in needles from trees grown on NPK‐fertilized soil than on non‐fertilized soil. After the transfer of spruce trees from fertilized soil to NPK‐rich nutrient solution, NRA was transiently increased. This effect was assigned to root injuries causing nitrate transport to the shoot and subsequent induction of NRA. Neither trees on fertilized soil nor trees transferred to NPK‐poor nutrient solution had increased NRA unless NO₂ was provided. The NO₂ gradient in the vicinity of a highway was used to test the long‐term effect of elevated levels of NO₂ on needle NRA of potted and field‐grown spruce trees. Compared with less polluted sites, permanently increased NRAs were detected when NO₂ concentrations were above 20 µg m⁻³. Controls of field measurements some 10 years after the introduction of catalytic converters in cars showed no significant change neither in NO₂ levels nor in the decreasing NRA of spruce needles with the distance from the highway.     

SO2 and assimilatory sulfate reduction in beech leaves

The effect of SO₂ on the extractable activity of ATP sulfurylase (EC 2.7.7.4.). adenosine 5'-phosphosulfate sulfotransferase, ribulosebisphosphate carboxylase, chlorophyll, protein, sulfate, and amino acids was examined in leaves of potted grafts of beech ( Fagus sylvatica L.) treated in outdoor fumigation chambers. Addition of 0.025 and 0.075 μl SO₂ 1⁻¹ to unfiltered ambient air caused a decrease in the extractable activity of adenosine 5'-phosphosulfate sulfotransferase to about 20 to 30% of the controls. Neither the extractable activity of ATP sulfurylase and ribulosebisphosphate carboxylase nor the content in chlorophyll, total amino acids and protein were significantly affected by SO₂, but there was an increase in the sulfate content. Leaves treated with 0.075 μl SO₂ 1⁻¹ contained more alanine and cysteine and less serine than the controls. After transfer of the SO2-treated beech trees to control chambers there was an increase in adenosine 5'-phosphosulfate sulfotransferase activity, but no significant decrease in SO₂₋⁴-sulfur.     

Effect of SO2, on the activity of adenosine 5'-phosphosulfate sulfotransferase from spruce trees (Picea abies) in fumigation chambers and under field conditions

The effect of SO₂ on adenosine 5'-phosphosulfate sulfotransferase activity and various other parameters of needles from spruce ( Picea abies L.) was studied using potted grafts in outdoor fumigation chambers and trees growing near a factory. In summer and autumn fumigation of grafted spruce, SO₂, decreased the extractable activity of adenosine 5'-phosphosulfate sulfotransferase to 12–50% of the controls, and reduced the amount of ³⁵S from sulphate incorporated into protein by excised branches to a comparable degree. SO₂ treatment in January and February inhibited the increase in adenosine 5'phosphosulfate sulfotransferase activity measured in the controls during this time. ATP-sulfurylase activity was less affected by SO₂. fumigation. In trees growing near a factory with high SO₂. emission, the activity of adenosine 5'-phosphosulfate sulfotransferase was about 35% of that of trees from a control area. The low enzyme activity was correlated with a high content of sulfate and compounds containing thiol groups.     

Influence of air pollutants and nutrient deficiency on D-1 protein content and photosynthesis in young spruce trees

Long-term fumigation with different mixtures of air pollutants, such as O₃, NO₂ and SO₂, in combination with potassium deficiency in 4-year-old spruce trees shows clearly that the photosynthetic apparatus reacts very sensitively to environmental stress. Even when no change in photosynthetic oxygen evolution of the leaves was measurable, the content of D-1 protein in the reaction center of photosystem II already increased significantly at low stress conditions. With increasing concentrations of pollutants, the content of D-1 protein decreased considerably. This pattern was observed with all combinations of gases, although they differed in effectiveness. The most potent effect on the content of D-1 protein was found with a combined fumigation of SO₂ plus NO₂. Obviously, the ratio between synthesis and degradation of the D-1 protein is influenced by stress factors. However, the content of D-1 protein was not strongly correlated with photosynthetic oxygen evolution in whole needles nor with electron transport rate in isolated thylakoids. Under controlled potassium deficiency, effects similar to those observed upon ozone fumigation developed. The results suggest unspecific stress answers for the D-1 content and the photosynthetic reactions rather than specific responses.     

The response of Norway spruce seedlings to simulated acid mist

Four pot experiments are reported in which Norway spruce ( Picea abies (L.) Karst) seedlings, of different nutrient status, were treated with acid mist for one growing season in open-top chambers (OTCs). Combinations of H⁺, SO₄²⁻, NH₄⁺ and NO₃⁻ were applied at different frequencies of application and supplying different doses of S and N kg ha⁻¹. Plant growth, visible injury, frost hardiness and nutrient status were observed. These experiments were undertaken to improve our understanding of the interaction of environmental factors such as nutrition and mist-exposure frequency on seedling response to N and S deposition.
Both acidity (pH 2·7) and SO₄²⁻ ions were necessary to induce visible injury. Mist containing SO₄²⁻, H⁺ and to a lesser extent NH₄⁺ significantly reduced winter frost hardiness. Increasing the misting frequency, and to a lesser extent the overall dose, increased the likelihood of acid mist causing visible injury and reducing frost hardiness. Post-planting stress, low N status and needle juvenility increased the likelihood of acid mist causing visible injury. Increased plant vitality, adequate N status and growth rate reduced the likelihood of acid-mist-induced reductions in frost hardiness.
Principles underlying the responses of spruce seedlings treated in controlled conditions to acid mist are discussed.     

The Toxicity of Sulphur Dioxide towards Certain Lactic Acid Bacteria from Fermented Apple Juice

This paper describes a method for testing the effect of various concentrations of SO₂ on lactic acid bacteria from ciders. The media and methods were devised to minimize loss of SO₂ due to oxidation or binding with carbonyl compounds. Exposure of laboratory or freshly isolated strains to various concentrations of free SO₂ at pH 4·0 did not readily kill them even at high concentrations of free SO₂ ( c. 150 p/m or 0·97 p/m molecular SO₂) yet they were suppressed at low concentrations ( c. 5 p/m or 0·032 p/m molecular SO₂). Reducing the pH to 3·4 reaffirmed how much more effective SO₂ is against lactic acid bacteria at lower pH levels because more is present as molecular SO₂. As a result of this the idea of quoting SO₂ values as p/m molecular SO₂ is advocated. Addition of hydrogen peroxide or acetaldehyde to a test system containing 142 p/m free SO₂ showed that they had a similar effect in nullifying its antimicrobial properties and allowing the test bacteria to grow. There was no indication that acetaldehyde bisulphite was toxic to the test bacteria.     

The role of sulphur compounds for breeding success of Ips typographus L. (Col., Scolytidae) on Norway Spruce (Picea abies [L.] Karst.)

Bark beetles, especially Ips typographus L. represent a severe biotic threat for spruce ( Picea abies [L.] Karst.) at low altitudes in Europe. We compared sulphur (total S, SO₄²⁻, glutathione, cysteine, methionine), nitrogen (total N, NO₃⁻, total protein, free amino acids), carbon, total phosphorus and PO₄³⁻, tree vigour index (TVI) and water content of the phloem after felling, and their dependent changes (tdc) with the breeding success of I. typographus . Twenty trees were classified according to age (34/90 years) and crown density (high/intermediate/low). Water content was higher in young trees than in old trees, higher in the crown than at breast height, and decreased significantly within the 8-week study period. In old trees, breeding success, length of mother galleries and SO₄²⁻ were significantly higher, while total protein, NO₃⁻ and water content were significantly lower than in young trees. Trees with intermediate crown density provided the best breeding success for I. typographus and had significantly higher arginine content and C/N ratio as well as low amounts of phosphate and glutamine. During the period of bark beetle breeding, total sulphur, glutathione, protein, NO₃⁻, aspartate, glutamine, glutamate, arginine and γ-aminobutyrate decreased significantly. The results support previous investigations that I. typographus develops best in physiologically weakened trees.     

Effects of sulphur dioxide on leaf photosynthesis: the role of temperature and humidity

The effect of temperature and humidity on SO₂–induced photosynthetic depression was determined in gas exchange experiments with leaves of Vicia faba , L. Stomatal behaviour was sensitive to humidity resulting in higher uptake rates of SO₂ and stronger reductions of photosynthesis at low VPD (vapour pressure deficit). After a fumigation period of 2 h, when the photosynthetic rate had stabilized, photosynthesis of leaves exposed to SO₂ at 8°C was reduced much more than at 18°C at the same rate of SO₂ uptake. Data analysis with a mechanistic model revealed that this effect was due to the slower rate of S(IV) oxidation at lower temperatures, resulting in higher accumulation of S(IV) and thus stronger reduction of photosynthesis. These results were confirmed by experimental analyses of the S(IV) concentration in leaves following fumigation, which showed that more S(IV) accumulated in leaves exposed at a lower temperature. This may explain the high sensitivity of plants exposed to SO₂ under winter conditions, when both VPD and temperature are low.     

Lichen recolonization in London under conditions of rapidly falling sulphur dioxide levels, and the concept of zone skipping

HAWKSWORTH, D. L. & McMANUS, P. M., 1989. Lichen recolonization in London under conditions of rapidly falling sulphur dioxide levels, and the concept of zone skipping. The lichen flora on trees and wood at 50 sites in north-west London was examined in 1988 to determine what changes had taken place since 1980, a period when mean winter SO₂ levels had fallen from around 130 μg m^-3 to within the range 29–55 μg m^-3 in the study area. Forty-nine species were found. The fruticose lichens Evernia prunaslri and Ramalina farinacea now occur in many central London parks, and the yellow green foliose Parmelia caperata was discovered at 12 sites (previously only at one, Ruislip, in 1980). Comparable numbers and growth forms of species occurred throughout the area. An assemblage of zone 4–5 species (Hawksworth & Rose, 1970 Nature, 227: 145–148) tolerant of mean winter SO₂ levels of 60–70 μg m^-3 failed to penetrate central London, although more sensitive species of zones 6 and 7 had; this phenomenon, which has not previously been reported, is referred to as 'zone skipping' and is attributed to the speed at which mean sulphur dioxide levels in London have fallen. Species returning are those to be expected on the basis of previously-published field correlations with mean winter SO₂ levels. Twenty-five species not seen within 16 km of the centre of London on trees or wood during this century were found; of these, eight had not been seen during the last 200 years.     

Interaction between sublethal pollution by sulphur dioxide and drought stress. The effect on photosynthetic capacity

Five-year-old Picea abies L. plants were grown in growth cabinets in the presence (3.1 μmol m⁻³) or absence of SO₂. After 5 weeks, the photosynthetic capacity of mature needles produced in the year was the same in both conditions. Trees were then submitted in situ to drought stress by withholding water. The decline of leaf photosynthetic capacity was greatest in the presence of SO₂. Chlorophyll decreased only when trees were submitted to dehydration in the presence of SO₂; however, this al-one could not account for the large decline in photosynthetic capacity observed under that condition. Needle water content was the lowest during dehydration in the presence of SO₂. It is concluded that the critical factor in the interaction between pollution by SO₂ and drought stress is the greater dehydration of the tissue found in stressed plants grown in the presence of SO₂. The large decline in photosynthetic capacity under such conditions might be due to this greater dehydration.     

The effect of nutrient and water additions on elemental mobility through small tundra watersheds

The objective was to quantify elemental movement through small tundra watersheds as affected by nutrient and water additions. Nutrient (slow-release NPK fertilizer) and water additions were applied to small tundra watersheds along Imnavait Creek Northern Alaska. Suction lysimeters and weired watersheds were used to monitor elemental mobility. Elemental concentrations in undisturbed watersheds were similar to Hubbard Brook watersheds except for NO₃-N which was much higher and PO₄-P which was lower in the Hubbard Brook watersheds. The water addition treatment led to a significant increase in Ca, Mg, Na, Fe, Mn and SO₄ concentrations which was attributed to contamination originating from within the water distribution system. Increased elemental concentrations in the irrigated watersheds were found up to 85 m below the point of application. Ammonium and NO₃ originating from the fertilizer were detected 6 m below the application point within two weeks of application. The NH₄ and NO₃ concentrations remained above background levels for two field seasons following fertilization. Both the irrigation and fertilization studies show that disturbances in tundra ecosystems may spread far beyond the initially impacted area both with respect to time and space.     

Physiological effects of sulphur dioxide. 1. The effect of SO2 on photosynthesis and stomatal regulation of Vicia faba L.

Abstract. The effect of short-term SO₂ fumigation on photosynthesis and transpiration of Vicia faba L. was measured at different irradiances and SO₂ concentrations. At high irradiances photosynthetic rates were reduced when leaves were exposed to SO₂ and the magnitude of the reduction was linearly related to the rate of SO₂ uptake through the stomata. Photosynthetic rates stabilized within 2 h after the start of fumigation.
The effect of SO₂ on photosynthesis was measured at different CO₂ concentrations to analyse the contribution of stomatal and non-stomatal factors to photosynthetic inhibition. Mesophyll resistance to CO₂ diffusion increased as a result of SO₂ exposure and caused a rapid reduction in photosynthesis after the start of fumigation. Stomatal resistance was not affected directly by SO₂ fumigation, but indirectly as a result of a feedback loop between net photosynthesis and internal CO₂ concentration.
Analysis of gas-exchange measurements in biochemical terms indicated that photosynthetic inhibition during SO₂ exposure can be explained by a stronger reduction in the affinity of RBP carboxylase/oxygenase for CO₂ than for O₂.     

Free fatty acids, neutral and polar lipids in Hordeum vulgare exposed to long-term fumigation with SO2

Three 9-day-old cultivars of Hordeum vulgare L. (Barberousse, Gerbel and Panda) were exposed to low levels of SO₂ fumigation (40 ± 5 and 117 ± 20 ppb). After 48 days of treatment the seedlings were harvested for lipid analysis. In comparison to the control (plants exposed to charcoal-filtered air), the total lipid content of fumigated seedlings declined at 40 ppb SO₂ and even more so at 117 ppb in all three cultivars. A large reduction in diacylglycerols. polar lipids and free sterols was also observed after fumigations at both SO₂ concentrations, whereas the treatments resulted in an increase in triacylglycerols and free fatty acids. The percentage composition of total fatty acids and that of each lipid class were changed by the fumigations. resulting in an increase in the degree of unsaturation. No changes in the percentage composition of sterols occurred in the fumigated leaves. These results suggest that even if SO₂ may not directly oxidize unsaturated fatty acids at the low concentrations used here (which do not cause visible injury). it may alter lipid metabolism. This alteration. which was particularly evident in the polar lipids and sterols, could affect the functions associated with membrane stabilization, in which lipids plus sterols play a key part.     

Effects of atmospheric SO2 on Azolla and Anabaena symbiosis

The water fern Azolla pinnata R. Br. was fumigated for 1 week with either 25, 50 or 100 nl 1⁻¹ SO₂. The symbiosis of Azolla with Anabaena azollae (spp.) was severely damaged by atmospheric SO₂ even at concentrations as low as 25 nl 1⁻¹, with significant reductions in growth, reduction of C₂H₂, NH₃ assimilation, protein synthesis, and heterocyst development. These disturbances appear to be mainly responsible for the extreme sensitivity of this fern to atmospheric SO₂. Changes in violaxanthin/antheraxanthin and epoxy-lutein/lutein ratios also indicate that free radical products are induced by atmospheric SO₂. These results suggest that the Azolla-Anabaena symbiotic system is a very responsive and reliable lower plant model to study the detailed effects of total sulphur deposition upon the balances between various important plant metabolic processes.     

Air pollution by SO2 amplifies the effects of water stress on enzymes and total soluble proteins of spruce needles

Measurements of soluble protein levels and catalytic capacity (maximum extractable activity) of isocitrate, glucose-6-phosphate and glutamate dehydrogenases were performed in needles of Picea abies L. Karst. under phytotron-controlled conditions in filtered or SO₂ polluted (0.08 ppm, 3.1 μmol m⁻³) air. In watered plants, pollution had no significant effects, although sulphur accumulated in the needles. Water deprivation (1 or 2 weeks depending on the experiments) of non-polluted plants decreased protein concentration and modified enzyme capacity, particularly for isocitrate and glucose-6-phosphate dehydrogenases. These effects were amplified in the polluted plants. Visible damage occurred only in plants subjected to both pollution and water stress. The results indicate that in spruce needles vulnerability of cell metabolism to the effects of a drought period is increased when water deprivation occurs under SO₂ pollution.     

Influence of nitrate and ammonium on the growth and 2,4-diaminobutyric acid composition of flatpea (Lathyrus sylvestris L.)

Abstract. Presence of 2.4-diaminobutyric acid (A₂bu), a neurotoxin, in tissues of flatpea ( Lathyrus sylvestris L.) necessitates a thorough understanding of the regulation of this nonprotein amino acid before the species can be recommended to livestock producers for forage applications. To determine how different concentrations and ratios of NO₃ and NH⁺₄ in growth media influence the levels of A₂bu and other free amino acids in the 'Lathco'flatpea cultivar, plants were grown hydroponically in controlled environments. The concentration of A₂bu was highest in tissues when the NO₃ to NH⁺₄ ratio in the nutrient solution was low. Responses of amides and other nonprotein amino acids, especially in the roots, followed a similar trend. Free protein amino acids in leaves and stems were generally unaffected by changes in NO₃ to NH⁺₄ ratios. In roots, protein amino acids increased as the NO₃ to NH⁺₄ ratio in the growth medium increased. Ammonium inhibited shoot and root growth; NO₃ alleviated the toxic effects of NH⁺₄. Soluble protein concentrations were higher in the shoots of NO₃-fed plants and in the roots of plants supplied with NH⁺₄. These results suggest that accumulation of A₂bu and other nonprotein amino acids, as well as asparagine and glutamine, plays a role in detoxification of NH⁺₄ and storage of N.     

Effect of nitrate on nitrogen fixation and nodule carbohydrate and organic acid concentrations in pea mutants deficient in nitrate reductase

Nitrate inhibits symbiotic N₂ fixation and a number of hypotheses concerned with NO₃⁻ assimilation have been suggested to explain this inhibition. These hypotheses were tested using a pea ( Pisum sativum L. cv. Juneau) with normal nitrate reductase NR; (EC 1,6,6,4) activity and two mutants of cv. Juneau, A317 and A334, with impaired NR activity. The plants were inoculated with three strains of Rhizobium leguminosarum and grown for 3 weeks in N-free medium, followed by 1 week in medium supplemented with 0, 5 or 10 m M KNO₃ before harvesting. NO₃ was taken up at comparable rates by the parent and the mutants and accumulated in leaf and stem tissue of the latter. Acetylene reduction rates were inhibited similarly in both the parent and mutants in the presence of KNO₃ but there were differences among rhizobial strains. Starch concentration of the nodules decreased by 46% in the presence of KNO₃ and there were differences among rhizobial strains but not among pea genotypes. Malate and succinate accumulated in nodules in the presence of KNO₃. These data are not consistent with the photosynthate deprivation hypothesis as a primary mechanism for NO₃ inhibition of N₂ fixation since NO₃ affected the nodule carbohydrate composition of all three pea genotypes in a similar manner. The lack of correlation between NR activity and NO₃ inhibition of N₂ fixation suggests that NO₃ assimilation may be only indirectly involved in the inhibition phenomenon.     

Dormancy in red rice. IV. Response of unimbibed and imbibing seeds to nitrogen dioxide

Nitrogen dioxide at 4 to 8 ml 1⁻¹ breaks dormancy of dehulled, unimbibed seeds of red rice ( Oryza sativa L.) with minimum exposure times to the gas of 20 min or less. The response is independent of incubation medium pH following treatment. Germination is complete within 2 days but proceeds 4 to 6 h more slowly than non-dormant controls. The magnitude of response at a constant NO₂ dose is dependent upon initial seed moisture. There was less than 40% germination at 9.6% initial moisture while germination was 95% at 12% initial moisture. NO₂ treatment also breaks dormancy of imbibing, dehulled seeds, but the response is dependent upon the pH of the medium. Dormancy is broken at pHs close to the pK_a of nitrous acid. Intact, unimbibed or imbibing seeds respond to NO₂ treatment only if partially dry-afterripened prior to exposure.