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  • 1
    Electronic Resource
    Electronic Resource
    Does Atmospheric Hydrogen Peroxide Contribute to Damage to Forest Trees? (1994)
    s.l. : American Chemical Society
    Environmental science & technology 28 (1994), S. 812-815 
    Details
    ISSN: 1520-5851
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/es00054a011
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  • 2
    Electronic Resource
    Electronic Resource
    Characterisation of antioxidative systems in the ectomycorrhiza-building basidiomycete Paxillus involutus (Bartsch) Fr. and its reaction to cadmium (2002)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 42 (2002), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effect of different cadmium (Cd) concentrations (5, 50 and 500 μM) on growth, Cd accumulation and antioxidative systems was studied in Paxillus involutus, grown in liquid medium. Cd was rapidly accumulated by P. involutus and resulted in growth inhibition within 24 h. Antioxidative enzymes (superoxide dismutase (SOD), EC 1.15.1.1; catalase (CAT), EC 1.11.1.6; monodehydroascorbate radical reductase (MDAR), EC 1.6.5.4; dehydroascorbate reductase (DAR) glutathione reductase (GR), EC 1.8.1.7 and glutathione-dependent peroxidase (GPx), EC 1.11.1.9) were active in the investigated fungus. Furthermore, high concentrations of glutathione but no ascorbate were detected. Cd exposure resulted in a significant induction of SOD activity. However, activities of enzymes responsible for the detoxification of H2O2 showed no Cd-dependent increase or were only transiently induced (CAT, GPx) and no accumulation of H2O2 was detected. Exposure to low Cd concentrations (5 and 50 μM) caused an increase in GR, while 500 μM Cd led to an inhibition of GR and CAT. Increased glutathione concentrations were observed as a consequence of all Cd treatments. These results suggest that the antioxidative protection of the investigated strain of P. involutus was sufficient to avoid Cd-mediated oxidative stress. It is likely that this strain was able to detoxify high concentrations of Cd by transport of Cd into the vacuole because a high correlation between Cd and sulphur in the vacuole was detected by EDX.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.2002.tb01025.x
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  • 3
    Electronic Resource
    Electronic Resource
    Leaf litter production and decomposition in a poplar short-rotation coppice exposed to free air CO2 enrichment (POPFACE) (2005)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 11 (2005), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: The capacity of forest ecosystems to sequester C in the soil relies on the net balance between litter production above, as well as, below ground, and decomposition processes. Nitrogen mineralization and its availability for plant growth and microbial activity often control the speed of both processes. Litter production, decomposition and N mineralization are strongly interdependent. Thus, their responses to global environmental changes (i.e. elevated CO2, climate, N deposition, etc.) cannot be fully understood if they are studied in isolation. In the present experiment, we investigated litter fall, litter decomposition and N dynamics in decomposing litter of three Populus spp., in the second and third growing season of a short rotation coppice under FACE. Elevated CO2 did not affect annual litter production but slightly retarded litter fall in the third growing season. In all species, elevated CO2 lowered N concentration, resulting in a reduction of N input to the soil via litter fall, but did not affect lignin concentrations. Litter decomposition was studied in bags incubated in situ both in control and FACE plots. Litter lost between 15% and 18% of the original mass during the eight months of field incubation. On average, litter produced under elevated CO2 attained higher residual mass than control litter. On the other end, when litter was incubated in FACE plots it exhibited higher decay rates. These responses were strongly species-specific. All litter increased their N content during decomposition, indicating immobilization of N from external sources. Independent of the initial quality, litter incubated on FACE soils immobilized less N, possibly as a result of lower N availability in the soil. Indeed, our results refer to a short-term decomposition experiment. However, according to a longer-term model extrapolation of our results, we anticipate that in Mediterranean climate, under elevated atmospheric CO2, soil organic C pool of forest ecosystems may initially display faster turnover, but soil N availability will eventually limit the process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2486.2005.00958.x
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  • 4
    Electronic Resource
    Electronic Resource
    Interactive effects of ozone and low UV-B radiation on antioxidants in spruce (Picea abies) and pine (Pinus sylvestris) needles (1998)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 104 (1998), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: To study the role of low UV-B radiation in modulating the response of antioxidants to ozone, 4-year-old pine (Pinus sylvestris L.) and spruce (Picea abies L.) seedlings potted in natural soil, were exposed in phytochambers to fluctuating ozone concentrations between 9 and 113 nl 1−1 according to field data recorded at Mt Wank (1175 m above sea level, Bavaria, Germany) and two-times ambient O3 levels. UV-B radiation was either added at a biologically effective level of ca 1.2 kJ m−2 day−1 , which is close to that found in March at Mt Wank, or was excluded by filters (〈0.08 kJ m−2 day−1). After one growth phase current-year needles were collected and analysed for antioxidative enzyme activities (superoxide dismutase, SOD, EC 1.15.1.1; catalase, CAT, EC 1.11.1.6; guaiacol peroxidase, POD, EC 1.11.1.7) and soluble antioxidants (ascorbate, glutathione). CAT, POD, ascorbate and glutathione, but not SOD, were increased in needles of both species in response to twice ambient O3 levels. UV-B radiation in the presence of ambient O3 caused an increase in total SOD activity in spruce but had no effects on antioxidants in pine. Twice ambient O3 levels together with low UV-B radiation counteracted the O3-induced increases in ascorbate and CAT in pine but not in spruce. Under these conditions spruce needles showed the highest antioxidative protection and revealed no indication of lipid peroxidation. Pine needles exposed to UV-B and elevated O3 levels showed elevated lipid peroxidation and a 5-fold increase in dehydroascorbate, suggesting that this species was less protected and suffered higher oxidative stress than spruce.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.1998.1040213.x
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  • 5
    Electronic Resource
    Electronic Resource
    Lignification and structural biomass production in tobacco with suppressed caffeic/5-hydroxy ferulic acid-O-methyl transferase activity under ambient and elevated CO2 concentrations (2004)
    Oxford, UK; Malden, USA : Munksgaard International Publishers
    Physiologia plantarum 121 (2004), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: To investigate the relationship between growth, biomass partitioning and lignification we used tobacco (Nicotiana tabacum) in which O-methyl transferase (OMT) activity, an enzyme involved in the pathway of sinapyl alcohol formation for lignin synthesis, was suppressed by antisense transformation. To modulate growth, controls and transformed tobacco plants were grown under ambient (approximately 380 p.p.m) or elevated CO2 (700 p.p.m), respectively. Lignin concentrations and composition were determined with spectrophotometric methods (thioglycolate and acetyl bromide) and Fourier transform infrared (FTIR) spectroscopy, respectively. A comparison of the thioglycolate and acetylbromide method suggested that the thioglycolate method was sensitive to changes in the syringyl/guaiacyl (S/G)-ratio in lignin and therefore not suitable for quantification in tissues with altered lignin composition. Growth under elevated CO2 increased leaf and stem biomass of both genotypes by 40 and 20%, respectively, compared with ambient CO2 and had no effect on root biomass. OMT suppression did not affect lignin concentrations in the leaves but caused a shift in biomass partitioning from the structural to the non-structural fraction. Elevated CO2 caused a shift towards production of structural compounds resulting in decreased foliar lignin concentrations and indicating that the lignin/structural mass ratio is flexible in leaves. By contrast, the lignin concentrations of stems were unaffected by elevated CO2 or OMT suppression and increased about three-fold from the apex to the base. Antisense-OMT plants produced more stem biomass than controls but showed no changes of the relative partitioning of biomass to the different pools. This indicates that the metabolic control of carbon fluxes to the production of structural versus non-structural fractions is tighter in stems than in leaves. FTIR spectroscopy indicated a relative increase in guaiacyl- as compared with syringyl-units in antisense-OMT tobacco, which was more pronounced under elevated as compared with ambient CO2. Since there was no evidence for decreased lignin concentrations in the antisense-OMT plants but increased biomass formation we suggest that less methylated lignins are ‘cheaper’ in biosynthetic carbon and energy demand and, thus, may enable plants to allocate increased resources to growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.0031-9317.2004.00297.x
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  • 6
    Electronic Resource
    Electronic Resource
    Diurnal fluctuations of antioxidative systems in leaves of field-grown beech trees (Fagus sylvatica): Responses to light and temperature (2001)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 111 (2001), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: To test the hypothesis that antioxidant systems flexibly adjust to short-term, diurnal fluctuations of ambient environmental conditions, ascorbate-related systems were studied over several day/night cycles in mature sun-acclimated leaves of field-grown beech trees (Fagus sylvatica). Light-dependent increases in the activities of ascorbate peroxidase (APX, EC 1.11.1.11), monodehydroascorbate radical reductase (MDAR, EC 1.1.5.4) and glutathione reductase (GR, EC 1.6.4.2) were not observed. Lowest activities of APX and MDAR were found on hot, sunny days. A strong negative correlation occurred between APX activities and ambient temperatures suggesting that this enzyme was temperature- rather than light-regulated. In contrast to the enzymatic defences, ascorbate levels increased by about 30% under bright sunlight suggesting that protection from excess light is mediated via the adjustment of metabolites. Under these conditions the apparent electron transport rate exceeded the capacity for assimilation and the dehydroascorbate pool increased twofold. Since dehydroascorbate reductase activities were hardly detected, MDAR activities seemed to be the major enzyme to keep ascorbate in its reduced state. However, MDAR appeared to be insufficient to maintain the redox balance of the ascorbate pool under high light intensities in the field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2001.1110205.x
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  • 7
    Electronic Resource
    Electronic Resource
    5-Oxo-prolinase activity in tobacco suspension cultures: Regulation by sulfate nutrition (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 59 (1983), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In heterotrophic and photoheterotrophic tobacco (Nicotiana tabacum L., var. Samsun) suspensions cultured with growth-limiting amounts of sulfate, 5-oxo-prolinase activity declines at the same time as the growth rate of the cells decreases. However, 5-oxo-prolinase activity is reduced to a greater extent than growth. As a result, the specific activity of 5-oxo-prolinase also declines when sulfur is scarce. The decrease in both growth and 5-oxo-prolinase activity can be prevented by adding sulfate to the suspensions during exponential growth. Addition of sulfate after the exponential growth phase restored neither growth nor 5-oxo-prolinase activity. These observations show that 5-oxo-prolinase activity in tobacco cells is regulated by the sulfate supply in the medium. Such a regulation is an essential prerequisite, but not a proof, for a role of 5-oxo-prolinase as the rate-limiting factor in glutathione degradation.During exponential growth the average specific activity of 5-oxo-prolinase in heterotrophic tobacco cells is twice as high as in photoheterotrophic cells. This difference is consistent with the idea that green cells are equipped for glutathione synthesis and export, and chloroplast-free cells for uptake and degradation of this peptide.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1983.tb06571.x
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  • 8
    Electronic Resource
    Electronic Resource
    Growth and protection against oxidative stress in young clones and mature spruce trees (Picea abies L.) at high altitudes (1999)
    Springer
    Oecologia 121 (1999), S. 149-156 
    Details
    ISSN: 1432-1939
    Keywords: Key words Ascorbate ; Glutathione reductase ; Superoxide dismutase ; Tree line growth ; Genetic variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Clones of Norway spruce (Picea abies L.) were grown for several years on an altitudinal gradient (1750 m, 1150 m and 800 m above sea level) to study the effects of environmental × genetic interactions on growth and foliar metabolites (protein, pigments, antioxidants). Clones at the tree line showed 4.3-fold lower growth rates and contained 60% less chlorophyll (per gram of dry matter) than those at valley level. The extent of growth reduction was clone-dependent. The mortality of the clones was low and not altitude-dependent. At valley level, but not at high altitude, needles of mature spruce trees showed lower pigment and protein concentrations than clones. In general, antioxidative systems in needles of the mature trees and young clones did not increase with increasing altitude. Needles of all trees at high altitude showed higher concentrations of dehydroascorbate than at lower altitudes, indicating higher oxidative stress. In one clone, previously identified as sensitive to acute ozone doses, this increase was significantly higher and the growth reduction was stronger than in the other genotypes. This clone also displayed a significant reduction in glutathione reductase activity at high altitude. These results suggest that induction of antioxidative systems is apparently not a general prerequisite to cope with altitude in clones whose mother plants originated from higher altitudes (about 650–1100 m above sea level, Hercycnic-Carpathian distribution area), but that the genetic constitution for maintenance of high antioxidative protection is important for stress compensation at the tree line.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050916
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  • 9
    Electronic Resource
    Electronic Resource
    Developmental changes of antioxidative systems in tobacco leaves as affected by limited sucrose export in transgenic plants expressing yeast-invertase in the apoplastic space (1996)
    Springer
    Planta 198 (1996), S. 253-262 
    Details
    ISSN: 1432-2048
    Keywords: Ascorbate ; Carbohydrate metabolism ; Glutathione ; Oxidative stress ; Superoxide dismutase ; Nicotiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It is generally believed that a restricted export of carbohydrates from source leaves causes oxidative stress because of an enhanced utilisation of O2 instead of NADP+ as electron acceptor in photosynthesis. To test this hypothesis, developmental changes of antioxidative systems were investigated in wild-type and transgenic tobacco (Nicotiana tabacum L.) suffering from disturbed sink-source relations by expression of yeast invertase in the apoplastic space. Young expanding leaves of the wild type contained higher activities of Superoxide dismutase (EC 1.15.1.1), ascorbate peroxidase (EC 1.11.1.11), catalase (EC 1.11.1.6), dehydroascorbate reductase (EC 1.8.5.1), glutathione reductase (EC 1.6.4.2) and a higher glutathione content than mature source leaves. The activity of monodehydroascorbate-radical reductase (EC 1.1.5.4) and the ascorbate content remained unaffected by the developmental stage in the wild type. In young expanding leaves of the transgenic plants the capacity of the antioxidative systems was similar to or higher than in corresponding leaves from the wild type. Source leaves of transgenic tobacco with an increased carbohydrate content showed a small chlorophyll loss, an increased malondialdehyde content, a selective loss of the activities of Cu/Zn-superoxide dismutase isoenzymes and a fourfold decrease in ascorbate compared with the wild type. There was no evidence that the protection from H2O2 was insufficient since source leaves of transgenic tobacco contained increased activities of catalase, ascorbate peroxidase, and monodehydroascorbate-radical reductase and an increased ascorbate-to-dehydroascorbate ratio compared with source leaves of the wild type. In severely chlorotic leaf sections of the transgenic plants, most components of the antioxidative system were lower than in green leaf sections, but the ascorbate-to-dehydroascorbate ratio was increased. These results suggest that carbohydrate-accumulating cells have an increased availability of reductant, which can increase the degree of reduction of the ascorbate system via glutathione-related systems or via the activity of monodehydroascorbate-radical reductase. At the same time, transgenic tobacco leaves seem to suffer from an increased oxidative stress, presumably as a result of a decreased consumption of O 2 .- by Cu/Zn-superoxide dismutases in the chloroplasts. There was no evidence that carbohydrate-accumulating leaves acclimated to enhanced O 2 .- production rates in the chloroplasts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00206251
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  • 10
    Electronic Resource
    Electronic Resource
    Interaction of sulfate and glutathione transport in cultured tobacco cells (1988)
    Springer
    Planta 176 (1988), S. 68-74 
    Details
    ISSN: 1432-2048
    Keywords: Glutathione (transport, regulation) ; Nicotiana ; Solanaceae ; Sultate (transport, regulation) ; Sulfur nutrition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photoheterotrophic and heterotrophic suspension cultures of tobacco (Nicotiana tabacum L.) were grown with 1 mM glutathione (reduced; GSH) as sole source of sulfur. Addition of sulfate to both cultures did not alter the rate of exponential growth, but affected the removal of GSH and sulfate in different ways. In photoheterotrophic suspensions, addition of sulfate caused a decline in the net uptake of GSH, whereas sulfate was taken up by the green cells immediately. In heterotrophic suspensions, however, addition of sulfate did not affect the net uptake of GSH and sulfate was only taken up by the cells after the GSH supply in the medium had been exhausted. Apparently, GSH uptake in photoheterotrophic cells is inhibited by sulfate, whereas sulfate uptake is inhibited by GSH in heterotrophic cells. The differences in the effect of GSH on sulfate uptake in photoheterotrophic and heterotrophic tobacco suspensions cannot be attributed to differences in the kinetic properties of sulfate carriers. In short-time transport experiments, both cultures took up sulfate almost entirely by an active-transport system as shown by experiments with metabolic inhibitors; sulfate transport of both cultures obeyed monophasic Michaelis-Menten kinetics with similar app. Km (photoheterotrophic cells: 16.0±2.0 μM; heterotrophic cells: 11.8±1.8 μM) and Vmax (photoheterotrophic cells: 323±50 nmol·min-1·g-1 dry weight; heterotrophic cells: 233±3 nmol·min-1·g-1 dry weight). Temperature- and pH-dependence of sulfate transport showed almost identical patterns. However, the cultures exhibited remarkable differences in the inhibition of sulfur influx by GSH in short-time transport experiments. Whereas 1 mM GSH inhibited sulfate transport into heterotrophic tobacco cells completely, sulfate transport into photoheterotrophic cells proceeded at more than two-thirds of its maximum velocity at this GSH concentration. The mode of action of GSH on sulfate transport in chloroplast-free tobacco cell does not appear to be direct: a 14-h exposure to 1 mM GSH was found to be necessary to completely block sulfate transport; a 4-h time of exposure did not affect this process. Consequently, glutathione does not seem to be a product of sulfur metabolism acting on sulfate-carrier entities by negative feedback control. When transferred to the whole plant, the observed differences in sulfate and glutathione influx into green and chloroplast-free cells may be interpreted as a regulatory device to prevent the uptake of excess sulfate by plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392481
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