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L-ascorbic acid (vitamin C) is a powerful reducing agent found in millimolar concentrations in plants, and is proposed to play an important role in scavenging free radicals in plants and animals. However, surprisingly little is known about the role of this antioxidant in plant environmental stress adaptation or ascorbate biosynthesis. We report the isolation of soz1, a semi-dominant ozone-sensitive mutant that accumulates only 30% of the normal ascorbate concentration. The results of genetic approaches and feeding studies show that the ascorbate concentration affects foliar resistance to the oxidizing gas ozone. Consistent with the proposed role for ascorbate in reactive oxygen species detoxification, lipid peroxides are elevated in soz1, but not in wild type following ozone fumigation. We show that the soz1 mutant is hypersensitive to both sulfur dioxide and ultraviolet B irradiation, thus implicating ascorbate in defense against varied environmental stresses. In addition to defining the first ascorbate deficient mutant in plants, these results indicate that screening for ozone-sensitive mutants is a powerful method for identifying physiologically important antioxidant mechanisms and signal transduction pathways. Analysis of soz1 should lead to more information about the physiological roles and metabolism of ascorbate.

The activity of ATP sulfurylase extracted from roots of intact canola (Brassica napus L. cv Drakkar) increased after withdrawal of the S source from the nutrient solution and declined after refeeding SO4(2-) to S-starved plants. The rate of SO4(2-) uptake by the roots was similarly influenced. Identical responses were obtained in SO4(2-)-fed roots when one-half of the root system was starved for S. The internal levels of SO4(2-) and glutathione (GSH) declined after S starvation of the whole root system, but only GSH concentration declined in +S roots of plants from split root experiments. The concentration of GSH in phloem exudates decreased upon transfer of plants to S-free solution. Supplying GSH or cysteine to roots, either exogenously or internally via phloem sap, inhibited both ATP sulfurylase activity and SO4(2-) uptake. Buthionine sulfoximine, an inhibitor of GSH synthesis, reversed the inhibitory effect of cysteine on ATP sulfurylase. It is hypothesized that GSH is responsible for mediating the responses to S availability. ATP sulfurylase activity and the SO4(2-) uptake rate are regulated by similar demand-driven processes that involve the translocation of a phloem-transported message (possibly GSH) to the roots that provides information concerning the nutritional status of the leaves

We have studied the expression of antioxidant genes in response to near ambient conditions of O3, SO2, and ultraviolet B (UV-B) in Nicotiana plumbaginifolia L. The genes analyzed encode four different superoxide dismutases (SODs), three catalases (Cat1, Cat2, and Cat3), the cytosolic ascorbate peroxidase (cyt APx), and glutathione peroxidase (GPx). The experimental setup for each treatment was essentially the same and caused no visible damage, thus allowing direct comparison of the different stress responses. Our data showed that the effects of O3, SO2, and UV-B on the antioxidant genes are very similar, although the response to SO2 is generally less pronounced and delayed. The effects of the different stresses are characterized by a decline in Cat1, a moderate increase in Cat3, and a strong increase in Cat2 and GPx. Remarkably, SODs and cyt APx were not affected. Analysis of SOD and APx expression in the ozone-sensitive Nicotiana tabacum L. cv PBD6 revealed that induction of the cytosolic copper/zinc SOD and cyt APx occurs only with the onset of visible damage. It is proposed that alterations in mRNA levels of catalases and GPx, but not of SODs and cyt APx, form part of the initial antioxidant response to O3, SO2, and UV-B in Nicotiana

The content of free SO2 (1.3-37.9 mg/l and 5.3-19.7 mg/l for 2009 and 2010) and total SO2 (38.3-272.0 mg/l and 52.0-102.1 mg/l for 2009 and 2010) for individual wines was in a broad interval. Results of free SO2 found using the commercial SO2 reagent were higher than our results since the reagent determined not only free SO2 but also reductones. The content of titrated acids was constant with a very moderate time decrease and the values were on average about 9.1-5.3 g/l (2009) and 13.1-7.9 g/l (2010). Similarly, the content of tartaric acid was nearly constant and the values were on average about 2.37-1.47 g/l (2009) and 6.65-2.69 g/l (2010). The percentage ratio of tartaric acid in the content of titrated acids is also constant (average 24.39%-38.6% for individual wines).

The pretreatment of softwood with sulfuric acid impregnation in the production of ethanol, based on enzymatic hydrolysis, has been investigated. The parameters investigated were: H2SO4 concentration (0.5-4.4% w/w liquid), temperature (180-240 degrees C), and residence time (1-20 minutes). The combined severity (log Ro-pH) was used to combine the parameters into a single reaction ordinate. The highest yields of fermentable sugars, i.e., glucose and mannose, were obtained at a combined severity of 3. At this severity, however, the fermentability declined and the ethanol yield decreased. In a comparison with previous results, SO2 impregnation was found to be preferable, since it resulted in approximately the same sugar yields, but better fermentability

Symptoms of forest decline of spruce in Europe range from needle yellowing and loss to tree and stand mortality, In a study area in northeast Bavaria, West Germany, where forest decline was initially detected, exposure to high concentrations of gaseous pollutants, SO2, NO2, and ozone has had no long-lasting direct effect on needles, and pathogens have only been secondary agents. Deposition of sulfur, nitrate, and ammonium, however, have significantly modified plant nutrition and soil chemistry. Spruce roots apparently take up ammonium rather than nitrate with an antagonistic effect on uptake of Mg. Nitrate left in the soil solution is leached together with sulfate to ground water, accelerating soil acidification and decreasing Ca/Al and Mg/Al ratios in the soil solution. Soil solution chemistry affects root development, and water and nutrient uptake. Had all nutrients become equally deficient, spruce trees probably could have adjusted by retarding their growth. However, canopy uptake of atmospheric nitrogen in addition to root uptake stimulated growth and caused a nitrogen to cation imbalance to develop; this imbalance resulted in the decline symptoms

Site-specific estimates for various environmentalstress factors were related with measured crowncondition data at a systematic 16 ×: 16 km^sup 2^ gridover Europe, according to previously statedhypotheses, using a multiple regression approach,including interactions, and lagged effects of stressfactors. Methodological differences among countriesaccounted for >30% of the variation in defoliation.Nevertheless, crown condition was found to varynaturally with tree age, altitude, drought stress and,most likely, also pathogenic fungi and insects.Significant impacts of air pollution (specificallyozone but also NO^sub x^, SO^sub x^ and acid deposition)were found at regional levels in parts of centralEurope, particularly for deciduous species. Impactsseemed less significant for conifers, especially forspruce, but this might be affected by confoundingeffects or strong correlations between (a harsh)climate and (low) atmospheric deposition in the areawhere spruce predominates. National studies indicatethat ozone and acid deposition can have a significanteffect on the defoliation of spruce as well. Weconclude that while forest condition varies naturally,continued emissions will contribute further to forestdecline in the long term.[PUBLICATION ABSTRACT]

The dual role of glutathione as a transducer of S status (A.G. Lappartient and B. Touraine [1996] Plant Physiol 111:147-157) and as an antioxidant was examined by comparing the effects of S deprivation, glutathione feeding, and H2O2 (oxidative stress) on SO42- uptake and ATP sulfurylase activity in roots of intact canola (Brassica napus L.). ATP sulfurylase activity increased and SO42- uptake rate severely decreased in roots exposed to 10 mM H2O2, whereas both increased in S-starved plants. In split-root experiments, an oxidative stress response was induced in roots remote from H2O2 exposure, as revealed by changes in the reduced glutathione (GSH) level and the GSH/oxidized glutathione (GSSG) ratio, but there was only a small decrease in SO42- uptake rate and no effect on ATP sulfurylase activity. Feeding plants with GSH increased GSH, but did not affect the GSH/GSSG ratio, and both ATP sulfurylase activity and SO42- uptake were inhibited. The responses of the H2O2-scavenging enzymes ascorbate peroxidase and glutathione reductase to S starvation, GSH treatment, and H2O2 treatment were not to glutathione-mediated S demand regulatory process. We conclude that the regulation of ATP sulfurylase activity and SO42- uptake by S demand is related to GSH rather than to the GSH/GSSG ratio, and is distinct from the oxidative stress response

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 δ¹⁵N of the needles ranged between -3.7 and -2.1 % o and for δ³⁴S a range between -0.4 and + 0.9 % c was observed. δ³⁴S and sulfur concentrations in the needles of both stands increased continuously with needle age and thus, were closely correlated. The δ¹⁵N values of the needles showed an initial decrease followed by an increase with needle age. The healthy stand showed more negative δ¹⁵N values in old needles than the declining stand. Nitrogen concentrations decreased with needle age. For soil samples at both sites the mean δ¹⁵N and < 5 34 S values increased from -3 % c (δ¹⁵N) or + 0.9 % o (δ³⁴S) in the uppermost organic layer to about + 4 % c (δ¹⁵N) or + 4.5 % o (δ³⁴S) 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. δ¹⁵N values and nitrogen concentrations were closely correlated (slope -0.0061 % δ¹⁵N per µmol cq N $g_{dw}^{ - 1}$), and δ³⁴S values were linearly correlated with sulfur concentrations (slope -0.0576 δ³⁴S per µmol 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 δ³⁴S values were linearly correlated with < ¹⁵N values (slope 0.459). A correlation of the sulfur and nitrogen isotope abundances on a Ä basis (which considers the different relative frequencies of 1 5 N 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 (δ³⁴S = 0.9 % o for total sulfur of the organic layer was assumed to be equivalent to about -1.0 % c for soil sulfate) and of the atmospheric SO₂ deposition (δ³⁴S = 2.0 % o at the healthy site and 2.3 % o at the declining site) the contribution of atmospheric SO₂ 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.

The rapid economic growth in China has been accompanied by a corresponding increase in pollution. In this paper the extent and effects of acid precipitation and precursors are discussed based on field observations and literature studies. Sulfur dioxide emissions are at present the major cause of acid precipitation, but emissions of nitrogen oxides are increasing. The deposition of sulfur compounds in the most polluted areas in China is higher than in those parts of Eastern and Central Europe which are experiencing severe pollution. Soils and soil waters seem to be acidified in many areas in southern China. Pollution has affected the vitality of forests and other vegetation particularly in and close to urban areas. Surface water acidification is not likely to become a major regional problem in the near future, but streams in some areas, which currently receive little acid deposition, appear to be sensitive to acidification.