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Andreas Holzinger - One of the best experts on this subject based on the ideXlab platform.
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osmotic stress in arctic and antarctic strains of the green alga zygnema zygnematales streptophyta effects on photosynthesis and ultrastructure
Micron, 2013Co-Authors: Franziska Kaplan, Louise A Lewis, Klaus Herburger, Andreas HolzingerAbstract:The osmotic potential and effects of Plasmolysis on photosynthetic oxygen evolution and chlorophyll fluorescence were studied in two Arctic Zygnema sp. (strain B, strain G) and two Antarctic Zygnema sp. (strain E, strain D). Antarctic strain D was newly characterized by rbcL sequence analysis in the present study. The two Antarctic strains, D and E, are most closely related and may represent different isolates of the same species, in contrast, strain B and G are separate lineages. Incipient Plasmolysis in the cells was determined by light microscopy after incubating cells in sorbitol solutions ranging between 200 mM and 1000 mM sorbitol for 3, 6 and 24 h. In Zygnema strain B and G incipient Plasmolysis occurred at ∼600 mM sorbitol solution (720 mOsmol kg−1, ψ = −1.67 MPa) and in strains D and E at ∼300 mM (318 mOsmol kg−1, ψ = −0.8 MPa) sorbitol solution. Hechtian strands were visualized in all plasmolysed cells, which is particularly interesting, as these cells lack pores or plasmodesmata. Ultrastructural changes upon osmotic stress were a retraction of the condensed cytoplasm from the cell walls, damages to chloroplast and mitochondrial membranes, increasing numbers of plastoglobules in the chloroplasts and membrane enclosed particles in the extraplasmatic space. Maximum photosynthetic rates (Pmax) in light saturated range were between 145.5 μmol O2 h−1 mg−1 Chl a in Zygnema G and 752.9 μmol O2 h−1 mg−1 Chl a in Zygnema E. After incubation in 800 mM sorbitol for 3 h Pmax decreased to the following percentage of the initial values: B: 16.3%, D: 16.8%, E: 26.1% and G: 35.0%. Osmotic stress (800 mM sorbitol) decreased maximum photochemical quantum yield of photosystem II (Fv/Fm) when compared to controls. Maximum values of relative electron transport rates of photosystem II (rETRmax) decreased after incubation in 400 mM sorbitol in Zygnema D and E, while they decreased in Zygnema B and G only after incubation in 800 mM sorbitol. The kinetics of the rETR curves were similar for the Arctic strains Zygnema B and G, but distinct from the Antarctic strains Zygnema D and E, which were similar when compared with each other. This suggests that the investigated Arctic Zygnema sp. strains might be better adapted to tolerate osmotic water stress than the investigated strains from the Antarctic.
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osmotic stress in arctic and antarctic strains of the green alga zygnema zygnematales streptophyta effects on photosynthesis and ultrastructure
Micron, 2013Co-Authors: Franziska Kaplan, Louise A Lewis, Klaus Herburger, Andreas HolzingerAbstract:The osmotic potential and effects of Plasmolysis on photosynthetic oxygen evolution and chlorophyll fluorescence were studied in two Arctic Zygnema sp. (strain B, strain G) and two Antarctic Zygnema sp. (strain E, strain D). Antarctic strain D was newly characterized by rbcL sequence analysis in the present study. The two Antarctic strains, D and E, are most closely related and may represent different isolates of the same species, in contrast, strain B and G are separate lineages. Incipient Plasmolysis in the cells was determined by light microscopy after incubating cells in sorbitol solutions ranging between 200 mM and 1000 mM sorbitol for 3, 6 and 24 h. In Zygnema strain B and G incipient Plasmolysis occurred at ∼600 mM sorbitol solution (720 mOsmol kg−1, ψ = −1.67 MPa) and in strains D and E at ∼300 mM (318 mOsmol kg−1, ψ = −0.8 MPa) sorbitol solution. Hechtian strands were visualized in all plasmolysed cells, which is particularly interesting, as these cells lack pores or plasmodesmata. Ultrastructural changes upon osmotic stress were a retraction of the condensed cytoplasm from the cell walls, damages to chloroplast and mitochondrial membranes, increasing numbers of plastoglobules in the chloroplasts and membrane enclosed particles in the extraplasmatic space. Maximum photosynthetic rates (Pmax) in light saturated range were between 145.5 μmol O2 h−1 mg−1 Chl a in Zygnema G and 752.9 μmol O2 h−1 mg−1 Chl a in Zygnema E. After incubation in 800 mM sorbitol for 3 h Pmax decreased to the following percentage of the initial values: B: 16.3%, D: 16.8%, E: 26.1% and G: 35.0%. Osmotic stress (800 mM sorbitol) decreased maximum photochemical quantum yield of photosystem II (Fv/Fm) when compared to controls. Maximum values of relative electron transport rates of photosystem II (rETRmax) decreased after incubation in 400 mM sorbitol in Zygnema D and E, while they decreased in Zygnema B and G only after incubation in 800 mM sorbitol. The kinetics of the rETR curves were similar for the Arctic strains Zygnema B and G, but distinct from the Antarctic strains Zygnema D and E, which were similar when compared with each other. This suggests that the investigated Arctic Zygnema sp. strains might be better adapted to tolerate osmotic water stress than the investigated strains from the Antarctic.
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Plasmolysis effects and osmotic potential of two phylogenetically distinct alpine strains of klebsormidium streptophyta
Protoplasma, 2012Co-Authors: Franziska Kaplan, Louise A Lewis, Johann Wastian, Andreas HolzingerAbstract:The osmotic potential and effects of Plasmolysis were investigated in two different Klebsormidium strains from alpine habitats by incubation in 300–2,000 (3,000) mM sorbitol. Several members of this genus were previously found to tolerate desiccation in the vegetative state yet information was lacking on the osmotic potentials of these algae. The strains were morphologically determined as Klebsormidium crenulatum and Klebsormidium nitens. These species belong to distinct clades, as verified by phylogenetic analysis of the rbcL gene. K. crenulatum is part of to the K. crenulatum/mucosum (‘F’ clade) and K. nitens of the ‘E2’ clade. Plasmolysis occurred in K. crenulatum at 800 mM sorbitol (961 mOsmol kg−1, Ψ = −2.09 MPa) and in K. nitens at 600 mM sorbitol (720 mOsmol kg−1, Ψ = −1.67 MPa). These are extraordinarily high osmotic values (very negative osmotic potentials) compared with values reported for other green algae. In K. crenulatum, the maximum photosynthetic rate (Pmax) in the light-saturated range was 116 μmol O2 h−1 mg−1 chl a. Incubation in 1,000 mM sorbitol decreased Pmax to 74.1% of the initial value, whereas 2,000 mM sorbitol (Ψ = −5.87 MPa) lead to an almost complete loss of oxygen production. In K. nitens, Pmax was 91 μmol O2 h−1 mg−1 chl a under control conditions and incubation in 800 mM sorbitol did not decrease Pmax, 2,000 mM sorbitol decreased Pmax only to about 62.6% of the initial value whereas 3,000 mM sorbitol stopped oxygen evolution. This indicated a broader amplitude for photosynthesis in the examined strain of K. nitens. Control samples and samples plasmolysed for 3 h in 800 mM sorbitol (K. nitens), 1,000 mM sorbitol (K. crenulatum), or 2,000 mM sorbitol were investigated by transmission electron microscopy after chemical or high-pressure freeze fixation. In cells undergoing Plasmolysis the protoplasts were retracted from the cell wall, the cytoplasm appeared dense, vacuoles were small and fragmented, and the cytoplasm was filled with ribosomes. Thin cytoplasmic strands were connected to the cell wall; 2,000 mM sorbitol increased the effect. The content of soluble carbohydrates in these two strains was investigated by HPLC, as this is one known mechanism for cells to maintain high osmotic pressure of the cytosol. Both Klebsormidium species contained diverse soluble carbohydrates, including a dominant mixed peak of unidentified oligosaccharides, and more minor amounts of raffinose, sucrose, glucose, xylose, galactose, mannose, inositol, fructose, glycerol, mannitol, and sorbitol. The total content of soluble carbohydrates was approximately 1.2% of the dry weight, indicating that this is not a major factor contributing to the high osmotic potential in these strains of Klebsormidium.
Xiangling You - One of the best experts on this subject based on the ideXlab platform.
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callose deposition is required for somatic embryogenesis in plasmolyzed eleutherococcus senticosus zygotic embryos
International Journal of Molecular Sciences, 2012Co-Authors: Lei Tao, Qiuyu Wang, Yang Yang, Xiangling YouAbstract:Dynamic changes in callose content, which is deposited as a plant defense response to physiological changes, were analyzed during somatic embryogenesis in Eleutherococcus senticosus zygotic embryos plasmolyzed in 1.0 M mannitol. During Plasmolysis, callose deposition was clearly observed inside the plasma membrane of zygotic embryo epidermal cells using confocal laser scanning microscopy. The callose content of zygotic embryos gradually increased between 0 and 12 h Plasmolysis and remained stable after 24 h Plasmolysis. During eight weeks induction of somatic embryogenesis, the callose content of explants plasmolyzed for 12 h was slightly higher than explants plasmolyzed for 6 or 24 h, with the largest differences observed after 6 weeks culture, which coincided with the maximum callose content and highest number of globular somatic embryos. The highest frequency of somatic embryo formation was observed in explants plasmolyzed for 12 h. The somatic embryo induction rate and number of somatic embryos per explant were markedly different in zygotic embryos pretreated with Plasmolysis alone (78.0%, 43 embryos per explant) and those pretreated with Plasmolysis and the callose synthase inhibitor 2-deoxy-d-glucose (11.5%, 8 embryos per explant). This study indicates that callose production is required for somatic embryogenesis in plasmolyzed explants.
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Callose Deposition Is Required for Somatic Embryogenesis in Plasmolyzed Eleutherococcus senticosus Zygotic Embryos
2012Co-Authors: Lei Tao, Qiuyu Wang, Yang Yang, Xiangling YouAbstract:Abstract: Dynamic changes in callose content, which is deposited as a plant defense response to physiological changes, were analyzed during somatic embryogenesis in Eleutherococcus senticosus zygotic embryos plasmolyzed in 1.0 M mannitol. During Plasmolysis, callose deposition was clearly observed inside the plasma membrane of zygotic embryo epidermal cells using confocal laser scanning microscopy. The callose content of zygotic embryos gradually increased between 0 and 12 h Plasmolysis and remained stable after 24 h Plasmolysis. During eight weeks induction of somatic embryogenesis, the callose content of explants plasmolyzed for 12 h was slightly higher than explants plasmolyzed for 6 or 24 h, with the largest differences observed after 6 weeks culture, which coincided with the maximum callose content and highest number of globular somatic embryos. The highest frequency of somatic embryo formation was observed in explants plasmolyzed for 12 h. The somatic embryo induction rate and number of somatic embryos per explant were markedly different in zygotic embryos pretreated with Plasmolysis alone (78.0%, 43 embryos per explant) and those pretreated with Plasmolysis and the callose synthase inhibitor 2-deoxy-D-glucose (11.5%, 8 embryos per explant). This study indicates tha
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Plasmolysis treatment enhances the expression of callose synthase gene in zygotic embryos of eleutherococcus senticosus
Journal of Forestry Research, 2010Co-Authors: Hu Xilin, Dean Xia, Xiangling YouAbstract:In previous study we reported that pretreatment with Plasmolysis enhanced somatic embryo formation in hypocotyls of Eleutherococcus senticosus. In the present study, the expression level of callose synthase gene in embryos of E. senticosus in response to 2,4-D, sucrose and mannitol treatments was analyzed by RT-PCR. The results show that Plasmolysis pretreatment using sucrose and mannitol significantly promoted the expression of callose synthase gene. Also, the thicker cell walls of explant plasmolyzed compared with controls were observed during the somatic embryogenesis. We suggest that the callose may make the cells in epidermis separate from neighboring cells and then develop into embryogenic potential cells.
Franziska Kaplan - One of the best experts on this subject based on the ideXlab platform.
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osmotic stress in arctic and antarctic strains of the green alga zygnema zygnematales streptophyta effects on photosynthesis and ultrastructure
Micron, 2013Co-Authors: Franziska Kaplan, Louise A Lewis, Klaus Herburger, Andreas HolzingerAbstract:The osmotic potential and effects of Plasmolysis on photosynthetic oxygen evolution and chlorophyll fluorescence were studied in two Arctic Zygnema sp. (strain B, strain G) and two Antarctic Zygnema sp. (strain E, strain D). Antarctic strain D was newly characterized by rbcL sequence analysis in the present study. The two Antarctic strains, D and E, are most closely related and may represent different isolates of the same species, in contrast, strain B and G are separate lineages. Incipient Plasmolysis in the cells was determined by light microscopy after incubating cells in sorbitol solutions ranging between 200 mM and 1000 mM sorbitol for 3, 6 and 24 h. In Zygnema strain B and G incipient Plasmolysis occurred at ∼600 mM sorbitol solution (720 mOsmol kg−1, ψ = −1.67 MPa) and in strains D and E at ∼300 mM (318 mOsmol kg−1, ψ = −0.8 MPa) sorbitol solution. Hechtian strands were visualized in all plasmolysed cells, which is particularly interesting, as these cells lack pores or plasmodesmata. Ultrastructural changes upon osmotic stress were a retraction of the condensed cytoplasm from the cell walls, damages to chloroplast and mitochondrial membranes, increasing numbers of plastoglobules in the chloroplasts and membrane enclosed particles in the extraplasmatic space. Maximum photosynthetic rates (Pmax) in light saturated range were between 145.5 μmol O2 h−1 mg−1 Chl a in Zygnema G and 752.9 μmol O2 h−1 mg−1 Chl a in Zygnema E. After incubation in 800 mM sorbitol for 3 h Pmax decreased to the following percentage of the initial values: B: 16.3%, D: 16.8%, E: 26.1% and G: 35.0%. Osmotic stress (800 mM sorbitol) decreased maximum photochemical quantum yield of photosystem II (Fv/Fm) when compared to controls. Maximum values of relative electron transport rates of photosystem II (rETRmax) decreased after incubation in 400 mM sorbitol in Zygnema D and E, while they decreased in Zygnema B and G only after incubation in 800 mM sorbitol. The kinetics of the rETR curves were similar for the Arctic strains Zygnema B and G, but distinct from the Antarctic strains Zygnema D and E, which were similar when compared with each other. This suggests that the investigated Arctic Zygnema sp. strains might be better adapted to tolerate osmotic water stress than the investigated strains from the Antarctic.
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osmotic stress in arctic and antarctic strains of the green alga zygnema zygnematales streptophyta effects on photosynthesis and ultrastructure
Micron, 2013Co-Authors: Franziska Kaplan, Louise A Lewis, Klaus Herburger, Andreas HolzingerAbstract:The osmotic potential and effects of Plasmolysis on photosynthetic oxygen evolution and chlorophyll fluorescence were studied in two Arctic Zygnema sp. (strain B, strain G) and two Antarctic Zygnema sp. (strain E, strain D). Antarctic strain D was newly characterized by rbcL sequence analysis in the present study. The two Antarctic strains, D and E, are most closely related and may represent different isolates of the same species, in contrast, strain B and G are separate lineages. Incipient Plasmolysis in the cells was determined by light microscopy after incubating cells in sorbitol solutions ranging between 200 mM and 1000 mM sorbitol for 3, 6 and 24 h. In Zygnema strain B and G incipient Plasmolysis occurred at ∼600 mM sorbitol solution (720 mOsmol kg−1, ψ = −1.67 MPa) and in strains D and E at ∼300 mM (318 mOsmol kg−1, ψ = −0.8 MPa) sorbitol solution. Hechtian strands were visualized in all plasmolysed cells, which is particularly interesting, as these cells lack pores or plasmodesmata. Ultrastructural changes upon osmotic stress were a retraction of the condensed cytoplasm from the cell walls, damages to chloroplast and mitochondrial membranes, increasing numbers of plastoglobules in the chloroplasts and membrane enclosed particles in the extraplasmatic space. Maximum photosynthetic rates (Pmax) in light saturated range were between 145.5 μmol O2 h−1 mg−1 Chl a in Zygnema G and 752.9 μmol O2 h−1 mg−1 Chl a in Zygnema E. After incubation in 800 mM sorbitol for 3 h Pmax decreased to the following percentage of the initial values: B: 16.3%, D: 16.8%, E: 26.1% and G: 35.0%. Osmotic stress (800 mM sorbitol) decreased maximum photochemical quantum yield of photosystem II (Fv/Fm) when compared to controls. Maximum values of relative electron transport rates of photosystem II (rETRmax) decreased after incubation in 400 mM sorbitol in Zygnema D and E, while they decreased in Zygnema B and G only after incubation in 800 mM sorbitol. The kinetics of the rETR curves were similar for the Arctic strains Zygnema B and G, but distinct from the Antarctic strains Zygnema D and E, which were similar when compared with each other. This suggests that the investigated Arctic Zygnema sp. strains might be better adapted to tolerate osmotic water stress than the investigated strains from the Antarctic.
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Plasmolysis effects and osmotic potential of two phylogenetically distinct alpine strains of klebsormidium streptophyta
Protoplasma, 2012Co-Authors: Franziska Kaplan, Louise A Lewis, Johann Wastian, Andreas HolzingerAbstract:The osmotic potential and effects of Plasmolysis were investigated in two different Klebsormidium strains from alpine habitats by incubation in 300–2,000 (3,000) mM sorbitol. Several members of this genus were previously found to tolerate desiccation in the vegetative state yet information was lacking on the osmotic potentials of these algae. The strains were morphologically determined as Klebsormidium crenulatum and Klebsormidium nitens. These species belong to distinct clades, as verified by phylogenetic analysis of the rbcL gene. K. crenulatum is part of to the K. crenulatum/mucosum (‘F’ clade) and K. nitens of the ‘E2’ clade. Plasmolysis occurred in K. crenulatum at 800 mM sorbitol (961 mOsmol kg−1, Ψ = −2.09 MPa) and in K. nitens at 600 mM sorbitol (720 mOsmol kg−1, Ψ = −1.67 MPa). These are extraordinarily high osmotic values (very negative osmotic potentials) compared with values reported for other green algae. In K. crenulatum, the maximum photosynthetic rate (Pmax) in the light-saturated range was 116 μmol O2 h−1 mg−1 chl a. Incubation in 1,000 mM sorbitol decreased Pmax to 74.1% of the initial value, whereas 2,000 mM sorbitol (Ψ = −5.87 MPa) lead to an almost complete loss of oxygen production. In K. nitens, Pmax was 91 μmol O2 h−1 mg−1 chl a under control conditions and incubation in 800 mM sorbitol did not decrease Pmax, 2,000 mM sorbitol decreased Pmax only to about 62.6% of the initial value whereas 3,000 mM sorbitol stopped oxygen evolution. This indicated a broader amplitude for photosynthesis in the examined strain of K. nitens. Control samples and samples plasmolysed for 3 h in 800 mM sorbitol (K. nitens), 1,000 mM sorbitol (K. crenulatum), or 2,000 mM sorbitol were investigated by transmission electron microscopy after chemical or high-pressure freeze fixation. In cells undergoing Plasmolysis the protoplasts were retracted from the cell wall, the cytoplasm appeared dense, vacuoles were small and fragmented, and the cytoplasm was filled with ribosomes. Thin cytoplasmic strands were connected to the cell wall; 2,000 mM sorbitol increased the effect. The content of soluble carbohydrates in these two strains was investigated by HPLC, as this is one known mechanism for cells to maintain high osmotic pressure of the cytosol. Both Klebsormidium species contained diverse soluble carbohydrates, including a dominant mixed peak of unidentified oligosaccharides, and more minor amounts of raffinose, sucrose, glucose, xylose, galactose, mannose, inositol, fructose, glycerol, mannitol, and sorbitol. The total content of soluble carbohydrates was approximately 1.2% of the dry weight, indicating that this is not a major factor contributing to the high osmotic potential in these strains of Klebsormidium.
Louise A Lewis - One of the best experts on this subject based on the ideXlab platform.
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osmotic stress in arctic and antarctic strains of the green alga zygnema zygnematales streptophyta effects on photosynthesis and ultrastructure
Micron, 2013Co-Authors: Franziska Kaplan, Louise A Lewis, Klaus Herburger, Andreas HolzingerAbstract:The osmotic potential and effects of Plasmolysis on photosynthetic oxygen evolution and chlorophyll fluorescence were studied in two Arctic Zygnema sp. (strain B, strain G) and two Antarctic Zygnema sp. (strain E, strain D). Antarctic strain D was newly characterized by rbcL sequence analysis in the present study. The two Antarctic strains, D and E, are most closely related and may represent different isolates of the same species, in contrast, strain B and G are separate lineages. Incipient Plasmolysis in the cells was determined by light microscopy after incubating cells in sorbitol solutions ranging between 200 mM and 1000 mM sorbitol for 3, 6 and 24 h. In Zygnema strain B and G incipient Plasmolysis occurred at ∼600 mM sorbitol solution (720 mOsmol kg−1, ψ = −1.67 MPa) and in strains D and E at ∼300 mM (318 mOsmol kg−1, ψ = −0.8 MPa) sorbitol solution. Hechtian strands were visualized in all plasmolysed cells, which is particularly interesting, as these cells lack pores or plasmodesmata. Ultrastructural changes upon osmotic stress were a retraction of the condensed cytoplasm from the cell walls, damages to chloroplast and mitochondrial membranes, increasing numbers of plastoglobules in the chloroplasts and membrane enclosed particles in the extraplasmatic space. Maximum photosynthetic rates (Pmax) in light saturated range were between 145.5 μmol O2 h−1 mg−1 Chl a in Zygnema G and 752.9 μmol O2 h−1 mg−1 Chl a in Zygnema E. After incubation in 800 mM sorbitol for 3 h Pmax decreased to the following percentage of the initial values: B: 16.3%, D: 16.8%, E: 26.1% and G: 35.0%. Osmotic stress (800 mM sorbitol) decreased maximum photochemical quantum yield of photosystem II (Fv/Fm) when compared to controls. Maximum values of relative electron transport rates of photosystem II (rETRmax) decreased after incubation in 400 mM sorbitol in Zygnema D and E, while they decreased in Zygnema B and G only after incubation in 800 mM sorbitol. The kinetics of the rETR curves were similar for the Arctic strains Zygnema B and G, but distinct from the Antarctic strains Zygnema D and E, which were similar when compared with each other. This suggests that the investigated Arctic Zygnema sp. strains might be better adapted to tolerate osmotic water stress than the investigated strains from the Antarctic.
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osmotic stress in arctic and antarctic strains of the green alga zygnema zygnematales streptophyta effects on photosynthesis and ultrastructure
Micron, 2013Co-Authors: Franziska Kaplan, Louise A Lewis, Klaus Herburger, Andreas HolzingerAbstract:The osmotic potential and effects of Plasmolysis on photosynthetic oxygen evolution and chlorophyll fluorescence were studied in two Arctic Zygnema sp. (strain B, strain G) and two Antarctic Zygnema sp. (strain E, strain D). Antarctic strain D was newly characterized by rbcL sequence analysis in the present study. The two Antarctic strains, D and E, are most closely related and may represent different isolates of the same species, in contrast, strain B and G are separate lineages. Incipient Plasmolysis in the cells was determined by light microscopy after incubating cells in sorbitol solutions ranging between 200 mM and 1000 mM sorbitol for 3, 6 and 24 h. In Zygnema strain B and G incipient Plasmolysis occurred at ∼600 mM sorbitol solution (720 mOsmol kg−1, ψ = −1.67 MPa) and in strains D and E at ∼300 mM (318 mOsmol kg−1, ψ = −0.8 MPa) sorbitol solution. Hechtian strands were visualized in all plasmolysed cells, which is particularly interesting, as these cells lack pores or plasmodesmata. Ultrastructural changes upon osmotic stress were a retraction of the condensed cytoplasm from the cell walls, damages to chloroplast and mitochondrial membranes, increasing numbers of plastoglobules in the chloroplasts and membrane enclosed particles in the extraplasmatic space. Maximum photosynthetic rates (Pmax) in light saturated range were between 145.5 μmol O2 h−1 mg−1 Chl a in Zygnema G and 752.9 μmol O2 h−1 mg−1 Chl a in Zygnema E. After incubation in 800 mM sorbitol for 3 h Pmax decreased to the following percentage of the initial values: B: 16.3%, D: 16.8%, E: 26.1% and G: 35.0%. Osmotic stress (800 mM sorbitol) decreased maximum photochemical quantum yield of photosystem II (Fv/Fm) when compared to controls. Maximum values of relative electron transport rates of photosystem II (rETRmax) decreased after incubation in 400 mM sorbitol in Zygnema D and E, while they decreased in Zygnema B and G only after incubation in 800 mM sorbitol. The kinetics of the rETR curves were similar for the Arctic strains Zygnema B and G, but distinct from the Antarctic strains Zygnema D and E, which were similar when compared with each other. This suggests that the investigated Arctic Zygnema sp. strains might be better adapted to tolerate osmotic water stress than the investigated strains from the Antarctic.
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Plasmolysis effects and osmotic potential of two phylogenetically distinct alpine strains of klebsormidium streptophyta
Protoplasma, 2012Co-Authors: Franziska Kaplan, Louise A Lewis, Johann Wastian, Andreas HolzingerAbstract:The osmotic potential and effects of Plasmolysis were investigated in two different Klebsormidium strains from alpine habitats by incubation in 300–2,000 (3,000) mM sorbitol. Several members of this genus were previously found to tolerate desiccation in the vegetative state yet information was lacking on the osmotic potentials of these algae. The strains were morphologically determined as Klebsormidium crenulatum and Klebsormidium nitens. These species belong to distinct clades, as verified by phylogenetic analysis of the rbcL gene. K. crenulatum is part of to the K. crenulatum/mucosum (‘F’ clade) and K. nitens of the ‘E2’ clade. Plasmolysis occurred in K. crenulatum at 800 mM sorbitol (961 mOsmol kg−1, Ψ = −2.09 MPa) and in K. nitens at 600 mM sorbitol (720 mOsmol kg−1, Ψ = −1.67 MPa). These are extraordinarily high osmotic values (very negative osmotic potentials) compared with values reported for other green algae. In K. crenulatum, the maximum photosynthetic rate (Pmax) in the light-saturated range was 116 μmol O2 h−1 mg−1 chl a. Incubation in 1,000 mM sorbitol decreased Pmax to 74.1% of the initial value, whereas 2,000 mM sorbitol (Ψ = −5.87 MPa) lead to an almost complete loss of oxygen production. In K. nitens, Pmax was 91 μmol O2 h−1 mg−1 chl a under control conditions and incubation in 800 mM sorbitol did not decrease Pmax, 2,000 mM sorbitol decreased Pmax only to about 62.6% of the initial value whereas 3,000 mM sorbitol stopped oxygen evolution. This indicated a broader amplitude for photosynthesis in the examined strain of K. nitens. Control samples and samples plasmolysed for 3 h in 800 mM sorbitol (K. nitens), 1,000 mM sorbitol (K. crenulatum), or 2,000 mM sorbitol were investigated by transmission electron microscopy after chemical or high-pressure freeze fixation. In cells undergoing Plasmolysis the protoplasts were retracted from the cell wall, the cytoplasm appeared dense, vacuoles were small and fragmented, and the cytoplasm was filled with ribosomes. Thin cytoplasmic strands were connected to the cell wall; 2,000 mM sorbitol increased the effect. The content of soluble carbohydrates in these two strains was investigated by HPLC, as this is one known mechanism for cells to maintain high osmotic pressure of the cytosol. Both Klebsormidium species contained diverse soluble carbohydrates, including a dominant mixed peak of unidentified oligosaccharides, and more minor amounts of raffinose, sucrose, glucose, xylose, galactose, mannose, inositol, fructose, glycerol, mannitol, and sorbitol. The total content of soluble carbohydrates was approximately 1.2% of the dry weight, indicating that this is not a major factor contributing to the high osmotic potential in these strains of Klebsormidium.
Lei Tao - One of the best experts on this subject based on the ideXlab platform.
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callose deposition is required for somatic embryogenesis in plasmolyzed eleutherococcus senticosus zygotic embryos
International Journal of Molecular Sciences, 2012Co-Authors: Lei Tao, Qiuyu Wang, Yang Yang, Xiangling YouAbstract:Dynamic changes in callose content, which is deposited as a plant defense response to physiological changes, were analyzed during somatic embryogenesis in Eleutherococcus senticosus zygotic embryos plasmolyzed in 1.0 M mannitol. During Plasmolysis, callose deposition was clearly observed inside the plasma membrane of zygotic embryo epidermal cells using confocal laser scanning microscopy. The callose content of zygotic embryos gradually increased between 0 and 12 h Plasmolysis and remained stable after 24 h Plasmolysis. During eight weeks induction of somatic embryogenesis, the callose content of explants plasmolyzed for 12 h was slightly higher than explants plasmolyzed for 6 or 24 h, with the largest differences observed after 6 weeks culture, which coincided with the maximum callose content and highest number of globular somatic embryos. The highest frequency of somatic embryo formation was observed in explants plasmolyzed for 12 h. The somatic embryo induction rate and number of somatic embryos per explant were markedly different in zygotic embryos pretreated with Plasmolysis alone (78.0%, 43 embryos per explant) and those pretreated with Plasmolysis and the callose synthase inhibitor 2-deoxy-d-glucose (11.5%, 8 embryos per explant). This study indicates that callose production is required for somatic embryogenesis in plasmolyzed explants.
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Callose Deposition Is Required for Somatic Embryogenesis in Plasmolyzed Eleutherococcus senticosus Zygotic Embryos
2012Co-Authors: Lei Tao, Qiuyu Wang, Yang Yang, Xiangling YouAbstract:Abstract: Dynamic changes in callose content, which is deposited as a plant defense response to physiological changes, were analyzed during somatic embryogenesis in Eleutherococcus senticosus zygotic embryos plasmolyzed in 1.0 M mannitol. During Plasmolysis, callose deposition was clearly observed inside the plasma membrane of zygotic embryo epidermal cells using confocal laser scanning microscopy. The callose content of zygotic embryos gradually increased between 0 and 12 h Plasmolysis and remained stable after 24 h Plasmolysis. During eight weeks induction of somatic embryogenesis, the callose content of explants plasmolyzed for 12 h was slightly higher than explants plasmolyzed for 6 or 24 h, with the largest differences observed after 6 weeks culture, which coincided with the maximum callose content and highest number of globular somatic embryos. The highest frequency of somatic embryo formation was observed in explants plasmolyzed for 12 h. The somatic embryo induction rate and number of somatic embryos per explant were markedly different in zygotic embryos pretreated with Plasmolysis alone (78.0%, 43 embryos per explant) and those pretreated with Plasmolysis and the callose synthase inhibitor 2-deoxy-D-glucose (11.5%, 8 embryos per explant). This study indicates tha