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  • 1
    Electronic Resource
    Electronic Resource
    Lipid composition of plasma membranes isolated from sunflower seedlings grown under water-stress (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 87 (1993), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Plasma membranes were isolated by aqueous two-phase-partitioning from sunflower (Helianthus annuus cv. Isabel) seedlings grown both under field irrigation and dryland conditions. Water-stressed plants showed a decrease in the leaf water potential and in the osmotic potential at full turgor, with the turgor pressure remaining at positive values. Dryland conditions also induced a reduction in the bulk modulus of elasticity. Plasma membranes of irrigated plants were characterized by high contents of phospholipids (68% of total lipids), free sterols (15. 7%) and glycolipids (9. 1%), mainly glycosphingolipids and steryl glycosides. Diacylglycerols, triacylglycerols and free fatty acids were also present. The major phospholipids were phosphatidylcholine and phosphatidylethanolamine with smaller amounts of phosphatidylinositol and phosphatidylglycerol. Following water stress, the plasma membranes showed a reduction of about 24 and 31% in total lipids and phospholipids, respectively. Also the amounts of glycolipids and diacylglycerols decreased significantly upon water stress. There was no change in free fatty acids, however, and triacylglycerols and free sterols increased. As a consequence, the free sterol to phospholipid molar ratio increased from 0. 4 to 0. 7 under water deficit conditions. The ratio of phosphatidylcholine to phosphatidylethanolamine increased from 1. 1 (control plants) to 1. 6 (water-stressed plants), while phosphatidic acid rose to 4% of total phospholipids. Dehydration did not result in any substantial change in the unsaturation level of the individual lipid classes, however. The results show that dryland conditions resulted in a marked alteration in the lipid composition of the sunflower leaf plasma membrane
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1993.tb02500.x
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  • 2
    Electronic Resource
    Electronic Resource
    Chemical changes and O2˙− production in thylakoid membranes under water stress (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 87 (1993), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Sunflower seedlings (Helianthus annuus cv. Isabel) subjected to a moderate level of water stress showed a reduced growth and a 0. 1 MPa osmotic adjustment came into play. Thylakoid membranes isolated from stressed leaves showed decreased chlorophyll (Chl) and protein contents but the Chl al/Chlb and protein/Chl ratios were unchanged. Water stress caused a preferential hydrolysis in thylakoid proteins: the hydrophilic to hydrophobic protein ratio increased from 0. 8 in the control to 4. 5 in the stressed plants. However, the degree of unsaturation was unchanged and the electron spin resonance (ESR) measurements did not show an increased level of O2.-radical production by photosynthetic membranes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1993.tb00144.x
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  • 3
    Electronic Resource
    Electronic Resource
    Degradation of membrane lipid components and antiovidanl levels in Hordeum vulgare exposed to long-term fumigation with SO2 (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 84 (1992), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Hordeum vulgare L. (cv. Barberousse) seedlings were continuosly exposed to SO2 (40±5 and 117±20 ppb) for 48 days and compared to control plants exposed to charcoal-filtered air. Glyco-and phospolipid amounts were strongly affected by exposure to SO2:, and decreased with increasing SO2, fumigation. The chloroplast membranes of fumigated leaves were characterized by lower quantities of rnonogalacto-syldiacylglycerol (MGDG) as well as of sulphoquinovosyldiacylglycerol (SQDG). Among the phospholipids a decrease in the phosphatidylglycerol (PG) content was observed, indicating that the chloroplast membranes are affected even by such low concentrations of SO2 as used here. As for the other phospholipids, phosphatidylcholine (PC) and phosphatidylinositol (PI) suffered a reduction and phosphatidylethano-lairrine (PE) almost disappeared at the highest SO2, concentration, whereas phosphatidic acid (PA) followed the opposite trend. The fatty acids of both glyco- and phospholipids fell sharply upon fumigation without any decline in the degree of unsataration. In particuSar, neither linoleic nor linolenic acid showed any evident change in level, suggesting that no lipid peroxidation of polytmsaturated fatty acid tails occurred. Furthermore, the electron spin resonance (ESR) showed no differences in the free radical levels between control and fumigated leaves.The level of malondialdehyde (MDA) decreased, while lipid-soluble antioxidants, as well as superoxide dismutase (SOD; EC 1.15.1.1) and catalase (EC 1.11.1.6) activities increased with the increase in SO2 concentration, providing evidence that defence mechanisms against oxy-radical action are activated by the plants at low levels of SO2,. Even if SO2, at low concentrations may not directly oxidize polyunsaturated fatty acids, it may act as a deesterifying factor on each component of both glyco- and phospholipids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1992.tb08767.x
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  • 4
    Electronic Resource
    Electronic Resource
    Role of phenolics in the antioxidative status of the resurrection plant Ramonda serbica during dehydration and rehydration (2004)
    Oxford, UK; Malden, USA : Munksgaard International Publishers
    Physiologia plantarum 122 (2004), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Ramonda serbica plants dehydrated for 14 days reached a relative water content of 4.2% and entered into anabiosis prior to being rehydrated for 48 h. Total ascorbate (AsA + DHA) and glutathione (GSH + GSSG) contents increased during dehydration and approached control values by the end of rehydration. Reduced ascorbate (AsA) and glutathione (GSH) were consumed during the first 13 days of dehydration when guaiacol-, syringaldazine- and phenolic peroxidases (EC 1.11.1.7) increased. At the end of dehydration AsA and GSH accumulated whereas peroxidases decreased to half the value of controls. In this period, plants of R. serbica face a phase of reduced metabolism and, thus, of reduced consumption of antioxidants. During rehydration, both AsA and GSH were utilized reaching, after 48 h, about 20 and 40% of their total pools, respectively; moreover peroxidases increased showing the recovery of metabolic activities. In the dehydration process total phenolic acids decreased, but accumulated after 5 h of rehydration and returned to control values at the end of rehydration. In R. serbica leaves, the most representative phenolic acids were protocatechuic, p-hydroxybenzoic and chlorogenic acids. Most concentrated phenolic acids, such as protocatechuic and chlorogenic acids, accumulated during the first period of rehydration when AsA decreased. These results suggest a role of ascorbate in inhibiting oxidation when phenolic peroxidases remain at low levels. As a consequence of this inhibition, ascorbate was oxidized and when most of it was consumed, oxidation of phenols resumed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.2004.00428.x
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  • 5
    Electronic Resource
    Electronic Resource
    Sunflower seedlings subjected to increasing water deficit stress: oxidative stress and defence mechanisms (1995)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 93 (1995), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Sunflower seedlings (Helianthus annuus cv. Licia Stella) reached a mild, moderate and severe level of water deficit stress after 5, 8 and 11 days of soil water depletion, respectively. At a moderate level of water deficit stress, an elastic adjustment occurred. At the same time, in response to a minor osmotic potential (Ψπ) and an intermediate rate of water potential (Ψw) decrease, glutathione level increased and enzyme activities related to the ascorbate/glutathione cycle were induced. At severe water deficit stress, the efficiency of this defence mechanism fell, oxidative processes intensified and soluble protein content decreased further. The results of the present experiments suggest that during water deficit stress the water status of the plants plays a key role in the activation of defence mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.1995.930105.x
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of in vivo copper treatment on the photosynthetic apparatus of two Triticum durum cultivars with different stress sensitivity (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 100 (1997), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effect of copper on the photosynthetic apparatus of two cultivars of durum wheat (Triticum durum cvs Adamello and Ofanto) with different sensitivity to drought and nickel stress were investigated. Plants were grown in nutrient solution or in nutrient solution further supplemented with CuSO4 to achieve final concentrations of 3.6 μM and 20 μM Cu. Several fluorescence analyses were performed, in presence or absence of DCMU, and with varying light intensities. Furthermore, light and electron microscopic investigations were carried out. In vivo treatment using 3.6 μ Cu produced a marked reduction in growth of the Cu-treated plants, but only mild effects on the fluorescence-related parameters. The Cu-induced reduction in the area above the fluorescence induction curve and in the time needed to reach the maximum of chlorophyll fluorescence (Fmax) were more pronounced. These results favour the hypothesis that under such conditions copper affects photosynthesis mainly in an indirect way, causing a slowing down of the electron transport as a consequence of the reduced requirement for photosynthesis products. The morphological analyses corroborate this hypothesis, showing toxic effects on the chloroplast structure due to Cu treatment. The differences between the two cultivars were not as pronounced as reported in the case of nickel or drought stresses; nevertheless, cv. Ofanto seemed to be less sensitive also to Cu stress than cv. Adamello.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1997.tb00016.x
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  • 7
    Electronic Resource
    Electronic Resource
    Thylakoid-bound and stromal antioxidative enzymes in wheat treated with excess copper (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: Copper is a catalyst in the formation of reactive free radicals and its toxicity may be due, at least in part, to oxidative damage. The response of thylakoid-bound and stromal antioxidative enzymes against the generation of superoxide radical was investigated in seedlings of wheat (Triticum durum L. cv. Adamello) grown in hydroponic culture for 10 days and subjected to 10 and 50 µM copper treatments. Electron spin resonance of roots evidenced a spectrum of copper, the intensity of which increased with the treatment, whereas the carbon-centered free radical spectrum detected in the control leaves was not seen anymore in the treated samples. As well as thylakoids, photosystem II (PSII) particles were able to produce the superoxide radical. Increased superoxide production both by thylakoids and PSII was observed in the sample treated with 50 µM Cu. Induction of thylakoid-bound and stromal antioxidative enzymes, with the exception of dehydroascorbate reductase, was also detected in leaves treated with the highest copper concentration. No Mn-superoxide dismutase (SOD, EC 1.15.1.1) was detected in thylakoids of wheat. Both stromal and thylakoid-bound SOD were CuZn-SOD with 16.2-kDa subunits. Both western blotting and immuno-electron microscopy showed that the SOD subunit was recognized by a polyclonal antibody against glyoxisomal CuZn-SOD from watermelon cotyledon. In the stroma of wheat, ascorbate peroxidase showed at least three well-resolved bands differently induced by copper treatments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.1998.1040416.x
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  • 8
    Electronic Resource
    Electronic Resource
    Unusual composition of thylakoid membranes of the resurrection plant Boea hygroscopica: Changes in lipids upon dehydration and rehydration (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 94 (1995), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Boea hygroscopica is a resurrection plant that is able to pass from biosis to anabiosis and vice versa following slow dehydration, but loses this ability following a rapid water loss. Fresh leaves were detached from plants grown in well-watered conditions and subjected to either rapid or slow dehydration and rehydration. Upon rehydration only slowly dried leaves revived. Analysis of thylakoid membranes revealed a rather small amount of total lipids (1,4–2 μmol g−1 dry weight) in comparison with other flowering plants. The main glycolipid was digalactosyldiacylglycerol (DGDG) rather than monogalactosyldiacylglycerol (MGDG) as is common in higher plants.Linoleic acid was the main fatty acid (30–40 mol% of total fatty acids), while linolenic acid was present from 14 to 26 mol%. In both the fresh and rehydrated leaves nearly all lipid components were present in similar amounts. Following dehydration the DGDG/MGDG molar ratio, which was 1.1 in control and rehydrated leaves, doubled by the end of the rapid drying period and was three times as high in slowly dried leaves. The total polar lipid/free sterol molar ratio as well as the free fatty acid level assumed the highest values in the rapidly dehydrated leaves. A shift towards the more unsaturated fatty acids was observed in all lipid classes upon dehydration irrespective of whether it was slow or rapid. Our data show only small differences between rapidly and slowly dehydrated leaves which can be correlated to the capacity of slowly dehydrated leaves to revive.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1995.tb00794.x
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  • 9
    Electronic Resource
    Electronic Resource
    Impaired carotenogenesis can affect organization and functionality of etioplast membranes (2004)
    Oxford, UK; Malden, USA : Munksgaard International Publishers
    Physiologia plantarum 122 (2004), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effects of impaired carotenogenesis on plastid membrane organization, functionality and stability were studied in etiolated barley plants grown at 20 and 30°C. The plants were treated with norflurazon or amitrole, two herbicides affecting phytoene desaturation and lycopene cyclization, respectively. At 20°C, the amitrole-treated etioplasts, which accumulated lycopene in their inner membranes, exhibited disorganized prolamellar bodies, containing a prevalent form of non-phototransformable protochlorophyllide (Pchlide). They also showed a certain difficulty in reducing the phototransformable pigment to chlorophyllide when exposed to light, and were unable to reform the active ternary complex [protochlorophyllide–oxidoreductase (POR)–Pchlide–NADPH] when placed back in darkness. No ultrastructural alterations were found in norflurazon-treated etioplasts, with carotenogenesis inhibited at the phytoene desaturation step. In these latter organelles, Pchlide, whose forms were comparable with those of the control etioplasts, was photoreduced quickly after illumination and the ternary complex was reformed during a subsequent dark period. Thus, the impaired carotenogenesis leading to the accumulation of lycopene showed greater interference with the etioplast membrane arrangement and functionality than did the earlier interruption of the biosynthetic pathway at the phytoene level. This might be due to the different interactions of the distinct carotenoid precursors with other membrane components. However, in etioplasts of norflurazon-treated plants, a rise in growth temperature caused a partial demolition of prolamellar bodies, showing a lowered thermostability of the carotenoid-deficient membranes. This latter effect strengthens the concept that a correct and complete carotenogenesis pathway, leading to the synthesis of polar carotenoids (i.e. xanthophylls), is required for the maintenance of stable plastid membranes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.2004.00376.x
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  • 10
    Electronic Resource
    Electronic Resource
    Growth in excess copper induces changes in the lipid composition and fluidity of PSII-enriched membranes in wheat (2000)
    Copenhagen : Munksgaard International Publishers
    Physiologia plantarum 108 (2000), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Changes in the lipid composition and fluidity of PSII-enriched thylakoids were studied in seedlings of wheat (Triticum durum Desf. cv. Adamello) grown in nutrient solution supplemented with CuSO4 to achieve a final concentration of 10 and 50 μM Cu. Metal content increased in the chloroplasts of the 50 μM Cu-grown plants. PSII isolated from wheat supplied with 10 μM Cu did not show any alteration in the lipid composition or in the lipid and protein levels of the membranes, nor was any change in the ultrastructure of the membranes detected. The 50 μM Cu-grown plants showed thylakoid swelling, particularly in the stroma and terminal grana thylakoids. Furthermore, an alteration in the lipid composition of PSII preparations was observed together with a decrease in the lipid content, which resulted in a reduction in the lipid to protein ratio. The monogalactosyldiacylglycerol (MGDG) to digalactosyldiacylglycerol (DGDG) molar ratio decreased, whereas the degradation of the polar lipids caused an accumulation of free fatty acids (FFA). The total amount of unsaturated lipids associated with the PSII-enriched membranes of wheat was not affected by excess copper supplies, even though changes in the individual fatty acids occurred. The effect of copper on the fluidity of PSII membranes was evaluated by electron paramagnetic resonance (EPR) measurements, using spin-probed fatty acids as probes. The PSII membranes, spin probed by means of 5- and 16-doxylstearic acids, showed that only the fluidity of the surface region of the bilayer close to the polar head group was reduced following the 50 μM Cu supply. In contrast, the fluidity of the inner membrane region of the bilayer did not show any change. The implications of changes in the lipid composition and lipid-protein interactions on the fluidity of specific transversal membrane regions are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2000.108001087.x
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