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1.
Pine ( Pinus silvestris L.) trees subjected to relatively low concentration of SO 2 in the field emit H 2S from the needles, as demonstrated by gas chromatographic analysis after preconcentration on a molecular sieve. H 2S is the only reduced sulfurous compound emitted from SO 2 fumigated leaves. The emission is light and SO 2 concentration dependent. Pine trees in the field and in laboratory experiments continue to emit H 2S several hours after the termination of prolonged SO 2 fumigation. The maximum emission rates observed from pine trees in the field and in laboratory experiments, 14 and 20 nanomoles per milligram chlorophyll per hour respectively, are about the activity expected for the sulfur assimilation pathway in the chloroplasts. 相似文献
2.
The emission of reduced volatile sulfur compounds from twigs of Norway spruce ( Picea abies (L.) Karst.) was measured in the field by cryosampling and gaschromatographic analysis. Trees were growing in the Erzgebirge (E-Germany) at Oberbärenburg and at the Kahleberg and at a third stand in NW-Bavaria (S-Germany). Emission rates were also measured for Scotch pine ( Pinus sylvestris L.) and Blue spruce ( Picea pungens Engelm.) at the Kahleberg. Twigs still attached to the trees were enclosed in a flow-through gas exchange cuvette. H 2S was detected as the predominant reduced sulfur compound emitted from the twigs. The mean H 2S emission rate from twigs of Norway spruce varied between 0.04 pmol kg -1 dw s -1 at Würzburg and 6.21 pmol kg -1 dw s -1 at the Kahleberg. Comparing different species at the Kahleberg, the mean H 2S emission rate was almost the same from twigs of Norway spruce (6.2 pmol kg -1 dw s -1) and Blue Spruce trees (5.9 pmol kg -1 dw s -1) but it was approximately 18 times higher for Scotch pine (110 pmol kg -1 dw s -1). The percentage of SO 2-exclusion via H 2S-emission of the tree species investigated at the Kahleberg is calculated on the basis of data on SO 2 fluxes. It is very small for Norway spruce and Blue spruce. However, for Scotch pine, H 2S emission contributes about 10% to the detoxification of SO 2. 相似文献
3.
H 2S emission from cucumber ( Cucumis sativus L.) leaf discs supplied with L-cysteine in the dark is inhibited 80–90% by aminooxyacetic acid (AOA), an inhibitor of pyridoxal-phosphate dependent enzymes. Exposure to L-cysteine in the light enhanced the emission of H 2S in response to this sulfur source. Turning off the light reduced the emission of H 2S to the rate observed in continuous dark; turning on the light enhanced the emission of H 2S to the rate observed in continuous light. Therefore, in the light H 2S emission in response to L-cysteine becomes a partially light-dependent process. Treatment with cyanazine, an inhibitor of photosynthetic electron transport, reduced H 2S emission in the light to the rate observed in continuous dark, but did not affect H 2S emission in the dark. In leaf discs pre-exposed to L-cysteine in the light, treatment with cyanazine+ AOA inhibited the emission of H 2S in response to L-cysteine completely. Therefore, only part of the H 2S emitted in response to this sulfur source is derived from a light-independent, but pyridoxal-phosphate-dependent process; the balance of the H 2S emitted is derived from a light-dependent process that can be inhibited by cyanazine. When cucumber leaf discs were supplied with a pulse of L-[ 35S]cysteine, radioactively labeled H 2S was emitted in two waves, one during the first hour of exposure to L-cysteine, and a second after 3–4 h; unlabeled H 2S, however, was emitted continuously. The second wave of emission of labeled H 2S was not observed in pulse-chase experiments in which sulfate or cyanazine were added to the treatment solution after 3 h of exposure to L-cysteine, or when the lights was turned off. The labeling pattern of sulfur compounds inside cucumber cells supplied with a pulse of L-[ 35S]cysteine showed that the labeled H 2S released from L-cysteine partially enters first the sulfite, then the sulfate pool of the cells. The radioactively labeled sulfate, however, is not incorporated into L-cysteine, but enters the H 2S pool of the cells again. These observations are consistent with the idea of an intracellular sulfur cycle in plant cells. The L-cysteine taken up by the leaf discs seems to be desulfhydrated in a light-independent, but pyridoxal-phosphate-dependent process. The H 2S synthesized this way may be partially released into the atmosphere; the other part of the H 2S produced in response to L-cysteine may be oxidized to sulfite, then to sulfate, which is subsequently reduced via the light-depent sulfate assimilation pathway. In the presence of excess L-cysteine, synthesis of additional cysteine may be inhibited, and the sulfide moiety may be split off carrier bound sulfide to enter the H 2S pool of the cells again. It is suggested that the function of this sulfur cycle may be regulation of the free cysteine pool.Abbreviation AOA
aminooxyacetic acid 相似文献
4.
Summary The 34S value of SO 2 emitted by natural gas refineries is about +25, which is higher than that for non-industrial sulfur sources in our study areas. Terrestrial mosses absorb SO 2 from the atmosphere and have a 34S value which is directly related to the degree of SO 2 stress to which they are subjected. The 34S values for conifer needles are lower than for mosses at the same collection site, which indicates that trees obtain sulfur from both atmospheric and soil sources.Potted conifers were transferred to sites differing in their degree of SO 2 stress. This difference is reflected by the change of 34S values of their needles. SO 2 absorbant pot covers, such as charcoal and moss, reduce the amount of airborne sulfur which is available to tress. Moss also may reduce SO 2 absorbed by soils in forest stands. We have used analysis of 34S values to (1) help define SO 2 dispersion patterns; (2) reveal the rates at which plants accumulate this pollutant; and (3) associate suspected SO 2 injury more closely to an emission source. 相似文献
5.
With the aid of a sulfur-specific flame photometric detector, an emission of volatile sulfur was detected from leaves of cucumber ( Cucumis sativus L.), squash and pumpkin ( Cucurbita pepo L.), cantaloupe ( Cucumis melo L.), corn ( Zea mays L.), soybean ( Glycine max [L.] Merr.) and cotton ( Gossypium hirsutum L.). The emission was studied in detail in squash and pumpkin. It occurred following treatment of the roots of plants with sulfate and was markedly higher from either detached leaves treated via the cut petiole, or whole plants treated via mechanically injured roots. Bisulfite elicited higher rates of emission than sulfate. The emission was completely light-dependent and increased with light intensity. The rate of emission rose to a maximum and then declined steadily toward zero in the course of a few hours. However, emission resumed after reinjury of roots, an increase in light intensity, an increase in sulfur anion concentration, or a dark period of several hours. The emission was identified as H2S by the following criteria: it had the odor of H2S; it was not trapped by distilled H2O, but was trapped by acidic CdCl2 resulting in the formation of a yellow precipitate, CdS; it was also trapped by base and the contents of the trap formed methylene blue when reacted with N,N-dimethyl-p-phenylenediamine and Fe3+. H2S emission is not the cause of leaf injury by SO2, since bisulfite produced SO2 injury symptoms in dim light when H2S emission was low, while sulfate did not produce injury symptoms in bright light when H2S emission was high. The maximum rates of emission observed, about 8 nmol min−1 g fresh weight−1, are about the activity that would be expected for the sulfur assimilation pathway of a normal leaf. H2S emission may be a means by which the plant can rid itself of excess inorganic sulfur when HS− acceptors are not available in sufficient quantity. 相似文献
6.
In the presence of excess sulfate, cysteine synthesis in pumpkin ( Cucurbita pepo) leaves is not limited by sulfate reduction, but by the availability of O-acetylserine. Feeding of O-acetylserine or its metabolic precursors S-acetyl-coenzyme-A and coenzyme A to leaf discs enhanced the incorportion of [ 35S]sulfate into reduced sulfur compounds, mainly into cysteine, at the cost of lowered H 2S emission; the uptake and reduction of sulfate is not affected by these treatments. β-Fluoropyruvate, an inhibitor of the generation of S-acetyl-coenzyme A via pyruvate dehydrogenase, stimulated H 2S emission in response to sulfate. This stimulation is overcompensated by addition of O-acetylserine, S-acetyl-coenzyme A, or coenzyme A. These results indicate that, in the presence of high amounts of sulfate, excess sulfur is reduced and emitted as H 2S into the atmosphere. The H 2S emitted seems to be produced by liberation from a precursor of cysteine rather than by cysteine desulfhydration. 相似文献
7.
Leaf discs and detached leaves exposed to l-cysteine emitted a volatile sulfur compound which was proven by gas chromatography to be H 2S. This phenomenon was demonstrated in all nine species tested ( Cucumis sativus, Cucurbita pepo, Nicotiana tabacum, Coleus blumei, Beta vulgaris, Phaseolus vulgaris, Medicago sativa, Hordeum vulgare, and Gossypium hirsutum). The emission of volatile sulfur by cucumber leaves occurred in the dark at a similar rate to that in the light. The emission of leaf discs reached the maximal rate, more than 40 picomoles per minute per square centimeter, 2 to 4 hours after starting exposure to l-cysteine; then it decreased. In the case of detached leaves, the maximum occurred 5 to 10 h after starting exposure. The average emission rate of H 2S during the first 4 hours from leaf discs of cucurbits in response to 10 millimolar l-cysteine, was usually more than 40 picomoles per minute per square centimeter, i.e. 0.24 micromoles per hour per square decimeter. Leaf discs exposed to 1 millimolar l-cysteine emitted only 2% as much as did the discs exposed to 10 millimolar l-cysteine. The emission from leaf discs and from detached leaves lasted for at least 5 and 15 hours, respectively. However, several hours after the maximal emission, injury of the leaves, manifested as chlorosis, was evident. H 2S emission was a specific consequence of exposure to l-cysteine; neither d-cysteine nor l-cystine elicited H 2S emission. Aminooxyacetic acid, an inhibitor of pyridoxal phosphate dependent enzymes, inhibited the emission. In a cell free system from cucumber leaves, H 2S formation and its release occurred in response to l-cysteine. Feeding experiments with [ 35S] l-cysteine showed that most of the sulfur in H 2S was derived from sulfur in the l-cysteine supplied and that the H 2S emitted for 9 hours accounted for 7 to 10% of l-cysteine taken up. 35S-labeled SO 32− and SO 42− were found in the tissue extract in addition to internal soluble S 2−. These findings suggest the existence of a sulfur cycle which converts l-cysteine to SO 42− through cysteine desulfhydration. 相似文献
8.
In Cucurbitaceae young leaves are resistant to injury from acute exposure to SO 2, whereas mature leaves are sensitive. After exposure of cucumber ( Cucumis sativus L.) plants to SO 2 at injurious concentrations, illuminated leaves emit volatile sulfur, which is solely H 2S. Young leaves emit H 2S many times more rapidly than do mature leaves. Young leaves convert approximately 10% of absorbed [ 35S]SO 2 to emitted [ 35S]H 2S, but mature leaves convert less than 2%. These results suggest that a high capability for the reduction of SO 2 to H 2S and emission of the H 2S is a part of the biochemical basis of the resistance of young leaves to SO 2. 相似文献
9.
Contents of organic sulfur, sulfate and the inorganic cations K +, Ca 2+, Mg 2+, Mn 2+ and Na + were compared in needles of three conifer species differing in tolerance to chronic SO 2 immissions. Sulfate and organic sulfur compounds were also measured in bark and wood. Field material was collected from Norway Spruce ( Picea abies (L.) Karst.), Colorado Spruce ( Picea pungens Engelm.) and Scots Pine ( Pinus sylvestris L.) at sites where the SO 2 concentration in air was high, and at another site where it was low. In general, sulfate contents were higher but cation contents lower at the sites where SO 2 concentrations were high than where they were low. Up to 114mmol · (kg DW) –1 sulfate was measured in fouryear-old needles of Norway Spruce from the Erzgebirge (annual mean of SO 2 in air 32 nl · 1 –1). Sulfate accumulation in this SO 2-sensitive conifer increased with SO 2 concentration in ambient air and with needle age, indicating that the main part of the sulfate resulted from the oxidative detoxification of SO 2. Loss of inorganic cations from ageing needles was reduced, or cation levels even increased, with increasing needle age, while sulfate accumulated. Apparently, cations served as counter-ions for sulfate, which is sequestered in the vacuoles. Individual trees differed in regard to the nature of cations which accumulated with sulfate. Calcium, potassium and magnesium were the dominating cations. Sodium levels were very low. Needles of the SO 2-tolerant conifers Colorado Spruce and Scots Pine growing next to Norway Spruce in the Erzgebirge did not accumulate, or accumulated less, sulfate with increasing needle age as compared to needles of Norway Spruce. However, somewhat more sulfate was found in the bark of the SO 2-tolerant species than in the bark of Norway Spruce. Scots Pine contained distinctly more sulfate in the wood than the other conifers. Since accumulation of organic sulfur compounds could not be observed with increasing needle age, or in bark and wood, reduction does not appear to play a major role in the detoxification of SO 2 by the investigated species. Physiological mechanisms permitting Colorado Spruce and Scots Pine to avoid the sulfate accumulation in the needles and the accompanying sequestration of cations that are observed in neighbouring Norway Spruce are discussed on the basis of the obtained data.Abbreviations S org
organic sulfur compounds
Died June 10, 1991, aged 29, in a traffic accident. He initiated this work.This work was supported by the Sonderforschungsbereich 251 of the University of Würzburg and by the Projektgruppe Bayern zur Erforschung der Wirkung von Umweltschadstoffen (PBWU). The authors with to thank Prof. Dr. W Kaiser and Prof. Dr. W. Urbach (both Julius-von-Sachs-Institut, University of Würzburg, Germany) for HPLC-analysis and ICP-analysis. 相似文献
10.
Concentrations of various sulfur compounds (SO 42−, H 2S, S 0, acid-volatile sulfide, and total sulfur) were determined in the profundal sediments and overlying water column of a shallow eutrophic lake. Low concentrations of sulfate relative to those of acid-volatile sulfide and total sulfur and a decrease in total sulfur with sediment depth implied that the contribution of dissimilatory sulfur reduction to H 2S production was relatively minor. Addition of 1.0 mM Na 235SO 4 to upper sediments in laboratory experiments resulted in the production of H 235S with no apparent lag. Kinetic experiments with 35S demonstrated an apparent Km of 0.068 mmol of SO 42− reduced per liter of sediment per day, whereas tracer experiments with 35S indicated an average turnover time of the sediment sulfate pool of 1.5 h. Total sulfate reduction in a sediment depth profile to 15 cm was 15.3 mmol of sulfate reduced per m 2 per day, which corresponds to a mineralization of 30% of the particulate organic matter entering the sediment. Reduction of 35S 0 occurred at a slower rate. These results demonstrated that high rates of sulfate reduction occur in these sediments despite low concentrations of oxidized inorganic compounds and that this reduction can be important in the anaerobic mineralization of organic carbon. 相似文献
11.
Summary Amounts of total sulfur and sulfate (NaHCO 3-extractable) were determined in soil samples from 19 representative profiles under forest vegetation in the areas of pleistocene and of the triassic middle range mountains in Germany. The mean total sulfur contents in surface and subsurface samples were 278 and 136 g S/g soil respectively. The total amount of sulfate and its fraction in the total sulfur was low in the surface samples. The subsurface soil samples of pH>5 contained very little sulfate. The difference between total sulfur and NaHCO 3-extractable sulfate described as nonsulfate fraction was mainly constituted by the fraction of organic sulfur. The mean C:N:S ratio (sulfur as nonsulfate) for samples with carbon content more than 2% was 225101.14. Compared with the parent material there was an accumulation of S in the acid brown earths developed from loess. Comparison of the sites with beech and spruce vegetation showed that the amount of nonsulfate-sulfur was of the same magnitude in both sites, but the amount of sulfate was higher in the spruce area. Similar differences between a beech and a spruce site were also observed for soils developed from weathered sandstone. The high amounts of sulfate under spruce are probably the result of higher inputs in the area due to the filtering action of the spruce trees on emitted SO 2. 相似文献
12.
Concentrations and natural isotope abundance of total sulfur and nitrogen as well as sulfate and nitrate concentrations were
measured in needles of different age classes and in soil samples of different horizons from a healthy and a declining Norway
spruce ( Picea abies (L.) Karst.) forest in the Fichtelgebirge (NE Bavaria, Germany), in order to study the fate of atmospheric depositions of
sulfur and nitrogen compounds.
The mean δ 15N of the needles ranged between −3.7 and −2.1 ‰ and for δ 34S a range between −0.4 and +0.9 ‰ was observed. δ 34S and sulfur concentrations in the needles of both stands increased continuously with needle age and thus, were closely correlated.
The δ 15N values of the needles showed an initial decrease followed by an increase with needle age. The healthy stand showed more
negative δ 15N values in old needles than the declining stand. Nitrogen concentrations decreased with needle age.
For soil samples at both sites the mean δ 15N and δ 34S values increased from −3 ‰ (δ 15N) or +0.9 ‰ (δ 34S) in the uppermost organic layer to about +4 ‰ (δ 15N) or +4.5 ‰ (δ 34S) in the mineral soil. This depth-dependent increase in abundance of 15N and 34S was accompanied by a decrease in total nitrogen and sulfur concentrations in the soil. δ 15N values and nitrogen concentrations were closely correlated (slope −0.0061 ‰ δ 15N per μmol eq N g dw
−1), and δ 34S values were linearly correlated with sulfur concentrations (slope −0.0576 ‰ δ 34S per μmol eq S g dw
−1). It follows that in the same soil samples sulfur concentrations were linearly correlated with the nitrogen concentrations
(slope 0.0527), and δ 34S values were linearly correlated with δ 15N values (slope 0.459). A correlation of the sulfur and nitrogen isotope abundances on a Δ basis (which considers the different
relative frequencies of 15N and 34S), however, revealed an isotope fractionation that was higher by a factor of 5 for sulfur than for nitrogen (slope 5.292).
These correlations indicate a long term synchronous mineralization of organic nitrogen and sulfur compounds in the soil accompanied
by element-specific isotope fractionations.
Based on different sulfur isotope abundance of the soil (δ 34S=0.9 ‰ for total sulfur of the organic layer was assumed to be equivalent to about −1.0 ‰ for soil sulfate) and of the atmospheric
SO 2 deposition (δ 34S=2.0 ‰ at the healthy site and 2.3 ‰ at the declining site) the contribution of atmospheric SO 2 to total sulfur of the needles was estimated. This contribution increased from about 20 % in current-year needles to more
than 50 % in 3-year-old needles. The proportion of sulfur from atmospheric deposition was equivalent to the age dependent
sulfate accumulation in the needles. In contrast to the accumulation of atmospheric sulfur compounds nitrogen compounds from
atmospheric deposition were metabolized and were used for growth. The implications of both responses to atmospheric deposition
are discussed. 相似文献
13.
Abstract. Leaching of inorganic cations (K +, Mg 2+) and in some cases of inorganic anions and sugars from detached twigs and single needles of spruce Picea abies L. Karst.) in the presence of acid rain (H 2SO 4, 1 mol m ?3) or salt solutions (Na 2 SO 4, 1 mol m ?3) was examined under laboratory conditions. Cation leaching (as percentage of the total water soluble ion content of the tissue per hour) was: K +: 0.01-0.02%; Mg 2+: 0.005-0.01%; Ca 2+: 0.1-0.2%. Leaching rates of anions were even lower than that and concentrations in the leachate were often below the detection limit of anion chromatography. Spraying with H 2SO 4 (pH 2.95, 1 mol m ?3) increased leaching only transiently. Similar effects were found when Na 2SO 4 was used instead of H 2SO 4. The transiently enhanced leaching was apparently due to H +/cation or cation/cation exchange at the twig or leaf surfaces. Feeding of K + or Al 3+ through the stems increased leaching of all cations within a few hours, again demonstrating rapid ion exchange in the apoplast. Leaching of potassium and magnesium from single needles occurred at similar relative rates as from twigs. Loss of Ca 2+ ions, however, was even smaller from needles than from twigs. Apparently, a large part of the Ca 2+ lost from twigs originated from the bark and not from the needles. Efflux of ions from longitudinal needle sections was about 1000 times taster than the rates obtained with intact needles, indicating that the cuticle was the main barrier Preventing solute loss. In relation to the total amount of mineral nutrients in trees, leaching is considered to be too small to be the primary cause of damage to trees stressed by acid rain, as has been suggested in the literature. 相似文献
14.
Major sulfur pools are quantified in soils and aboveground biomass of a coniferous boreal forest. Total ecosystem S averages
1395 kg·ha −1 of which 98% is found in the soil, with 89% being in the mineral horizons. Organic S dominates in soil, tree parts (trunks,
branches + foliage, roots) and litterfall, ranging from 77 to 99% of total S concentration. Carbon-bonded S, ester sulfate
and SO 4-S in soil profiles range respectively from 51–68%, 29–37% and 1–14% of total S concentrations and account respectively for
57, 33 and 10% of total S on an areal basis. Adsorbed SO 4 accounts for 82% of total SO 4, and can be predicted from Al bound to organic matter, amorphous Al and pH (r 2 = 0.81). There is a strong relationship between % carbon and carbon-bonded S in 4 of the 5 soil horizons studied which represent
over 95% of the total soil organic matter, whereas ester sulfate is related to % carbon in 3 soil horizons representing only
37% of the soil organic matter. An analysis of atmospheric S loading and S data for 10 forested sites in Europe and North
America suggests that the size of the organic S pool in forested systems is independent of atmospheric loading. 相似文献
15.
Summary Young Norway spruce seedlings irrigated with 5 per cent K 2SO 4 for 7 days exhale gaseous H 2S into the atmosphere. The share of the weight of H 2S per 1 kg of dry substance of needles for 1 h was 2.22 g during the 8th day. Where the K 2SO 4 solution was irrigated for 28 days, there began to appear on the needles a brown necrosis similar to those forming due to the effect of atmospheric sulphur dioxide. During the experiment, the exchange acidity of the soil pH/KCl did not change. The discussion discusses the mechanism of inhibition of metabolic processes in higher plants due to excessive amounts of SO 4-ion having been absorbed from the soil. 相似文献
16.
A computer model is used to analyze fluxes of SO 2 from polluted air into leaves and the intracellular distribution of sulfur species derived from SO 2. The analysis considers only effects of acidification and of anion accumulation. (i) The SO 2 flux into leaves is practically exclusively controlled by the boundary-layer resistance of leaves to gas diffusion and by stomatal opening. At constant stomatal opening, flux is proportional to the concentration of SO 2 in air. (ii) The sink capacity of cellular compartments for SO 2 depends on intracellular pH and the intracellular localization of reactions capable of oxidizing or reducing SO 2. In the mesophyll of illuminated leaves, the chloroplasts possess the highest trapping potential for SO 2. (iii) If intracellular ion transport were insignificant, and if bisulfite and sulfite could not be oxidized or reduced, leaves with opened stomata would rapidly be killed both by the accumulation of sulfites and by acidification of chloroplasts and cytosol even if SO 2 levels in air did not exceed concentrations thought to be permissible. Acidification and sulfite accumulation would remain confined largely to the chloroplasts and to the cytosol under these conditions. (iv) Transport of bisulfite and protons produced by hydration of SO 2 into the vacuole cannot solve the problem of cytoplasmic accumulation of bisulfite and sulfite and of cytoplasmic acidification, because SO 2 generated in the acidic vacuole from the bisulfite anion would diffuse back into the cytoplasm. (v) Oxidation to sulfate which is known to occur mainly in the chloroplasts can solve the problem of cytoplasmic sulfite and bisulfite accumulation, but aggravates the problem of chloroplastic and cytosolic acidification. (vi) A temporary solution to the problem of acidification requires the transfer of H + and sulfate into the vacuole. This transport needs to be energized. The storage capacity of the vacuole for protons and sulfate defines the extent to which SO 2 can be detoxified by oxidation and removal of the resulting protons and sulfate anions from the cytoplasm. Calculations show that even at atmospheric levels of SO 2 thought to be tolerable, known vacuolar buffer capacities are insufficient to cope with proton production during oxidation of SO 2 to sulfate within a vegetation period. (vii) A permanent solution to the problem of acidification is the removal of protons. Protons are consumed during the reduction of sulfate to sulfide. Proteins and peptides contain sulfur at the level of sulfide. During photosynthesis in the presence of the permissible concentration of 0.05l·l -1 SO 2, sulfur may be deposited in plants at a ratio not far from 1/500 in relation to carbon. The content of reduced sulfur to carbon is similar to that ratio only in fast-growing, protein-rich plants. Such plants may experience little difficulty in detoxifying SO 2. In contrast, many trees may contain reduced sulfur at a ratio as low as 1/10 000 in relation to carbon. Excess sulfur deposited in such trees during photosynthesis in polluted air gives rise to sulfate and protons. If detoxification of SO 2 by reduction is inadequate, and if the storage capacity of the vacuoles for protons and sulfate is exhausted, damage is unavoidable. Calculations indicate that trees with a low ratio of reduced S to C cannot tolerate long-term exposure to concentrations of SO 2 as low as 0.02 or 0.03 l·l -1 which so far have been considered to be non-toxic to sensitive plant species. 相似文献
17.
The microzonation of O 2 respiration, H 2S oxidation, and SO 42- reduction in aerobic trickling-filter biofilms was studied by measuring concentration profiles at high spatial resolution (25 to 100 μm) with microsensors for O 2, S 2-, and pH. Specific reaction rates were calculated from measured concentration profiles by using a simple one-dimensional diffusion reaction model. The importance of electron acceptor and electron donor availability for the microzonation of respiratory processes and their reaction rates was investigated. Oxygen respiration was found in the upper 0.2 to 0.4 mm of the biofilm, whereas sulfate reduction occurred in deeper, anoxic parts of the biofilm. Sulfate reduction accounted for up to 50% of the total mineralization of organic carbon in the biofilms. All H 2S produced from sulfate reduction was reoxidized by O 2 in a narrow reaction zone, and no H 2S escaped to the overlying water. Turnover times of H 2S and O 2 in the reaction zone were only a few seconds owing to rapid bacterial H 2S oxidation. Anaerobic H 2S oxidation with NO 3- could be induced by addition of nitrate to the medium. Total sulfate reduction rates increased when the availability of SO 42- or organic substrate increased as a result of deepening of the sulfate reduction zone or an increase in the sulfate reduction intensity, respectively. 相似文献
18.
In-situ partial pressures of hydrogen in anoxic profundal lake sediments reached values of up to 5 Pa which were more than 5 orders of magnitude lower than the partial pressures of methane. Analysis of gas bubbles collected from anoxic submerged paddy soil showed H 2 partial pressures in the range of 1.8 ± 1.3 Pa being ca. 4 orders of magnitude lower than the CH 4 partial pressures. H 2 emission rates, on the other hand, were less than 3 orders of magnitude lower than the CH 4 emission rates indicating that H 2 and CH 4 were oxidized to a different extent in the rhizosphere of the soil before they reached the atmosphere, or that H 2 was produced by the plants. More than 70% of the emitted H 2 reached the atmosphere via plant-mediated flux. The rest was emitted via ebullition from the anoxic soil and, in addition, was produced in the paddy water. A significant amount of H 2 was indeed found to be produced in the water under conditions where thallic algae and submerged parts of the rice plants produced oxygen by photosynthesis. Very little H 2 was emitted via molecular diffusion through the paddy water; in addition, this amount was less than expected from the degree of supersaturation and the diffusional emission rate of CH 4 indicating a relatively high rate of H 2 consumption in the surface film of the paddy water. The total H 2 source strength of rice paddies and other freshwater environments was estimated to be less than 1 Tg yr -1, being negligible in the atmospheric budget of H 2. 相似文献
19.
Brassica oleracea L. was rather insensitive to atmospheric H 2S: growth was only negatively affected at ≥0.4 μl I ?1. Shoots formed a sink for H 2S and the uptake rate showed saturation kinetics with respect to the atmospheric concentration. The H 2S uptake rate was high in comparison with other species, which may reflect the high sulfur need of Brassica. The net uptake of sulfate by roots of hydroponically grown plants was substantially reduced after one week of exposure to 0.25 μl l ?1 H 2S, indicating that plants switched in part from sulfate to H 2S as sulfur source for plant growth. Plants were sulfur deficient after two weeks of sulfur deprivation, illustrated by reduced growth, which was more pronounced for shoots than for roots, and in enhanced shoot dry matter content. The latter could for the greater part be attributed to enhanced levels of soluble sugars and starch. Sulfur deficiency was further characterized by a low pigment content, extremely low levels of sulfate and water-soluble non-protein thiols, and by enhanced levels of nitrate and free amino acids, particularly in the shoots. Furthermore, sulfur deficient plants contained a lower total lipid content in shoots, whereas its content in roots was unaffected. The level of sulfolipids was decreased in both roots and shoots. When sulfur deprived plants were exposed to 0.25 μl I ?1 H 2S for one week, all sulfur deficiency symptoms were abolished and growth was restored. Furthermore, plants were able to grow with 0.4 μl I ?1 H 2S as the sole sulfur source. Water-soluble non-protein thiol content was enhanced in both shoots and roots of H 2S exposed plants, irrespective of the sulfate supply to the roots, whereas plants grown with H 2S as sole sulfur source contained very low sulfate levels. The interaction between atmospheric and pedospheric sulfur nutrition in plants is discussed. 相似文献
20.
Summary Photosynthetic performance of several needle age classes of Norway spruce trees [ Picea abies (L.) Karst.] in highly SO 2-polluted and heavily damaged forest sites was measured at two different locations in the Ore Mountains (Erzgebirge, Krusne Hory) during early summer. The carboxylation efficiency showed a dramatic drop from current-year's needles to 1-year-old needles with only a slight further decrease with increased needle age. The light use efficiency also revealed these characteristics. For both parameters, no linear decrease with needle age could be found. In contrast, the maximum photosynthetic capacity (A 2500) decreased linearly with time and revealed a good correlation with the total sulfur content of the needles. Absolute values measured for A 2500 were approximately 50% lower than those of comparable trees in the nearby Fichtelgebirge. Mineral deficiencies or acute nutrient imbalances of the needles were not detected. In contrast to the situation in the forests of the Fichtelgebirge, a direct effect of gaseous SO 2 on the trees in the Ore Mountains seems plausible.This paper is dedicated to our teacher Professor Otto Ludwig Lange on the occasion of his 65th birthday 相似文献
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