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Abstract Changes in cell volume and solute content upon hyperosmotic shock have been studied for six unicellular blue-green algae (cyanobacteria): Synechococcus PCC 6301, PCC 6311; Synechocystis PCC 6702, PCC 6714, PCC 6803 and PCC 7008. The extent of change in volume was shown to be dependent upon the solute used to establish the osmotic gradient, with cells in NaCl showing a reduced shrinkage when compared to cells in media containing added sorbitol and sucrose. Uptake of extracellular solutes during hyperosmotic shock was observed in Synechocystis PCC 6714, with maximum accumulation of external solutes in NaCl and minimum solute uptake in sucrose solutions. Conversely, solute loss from the cells (K+ and amino acids) was greatest in sucrose-containing media and least in NaCl. The results show that these blue-green algae do not behave as ‘ideal osmometers’ in media of high osmotic strength. It is proposed that short-term changes in plasmalemma permeability in these organisms may be due to transient membrane instability resulting from osmotic imbalance between the cell and its surrounding fluid at the onset of hyperosmotic shock. 相似文献
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Carbonic Anhydrase and the Regulation of Photosynthesis 总被引:14,自引:0,他引:14
THE role of CO2 in the regulation of photosynthetic and respiratory metabolism in plants is little understood in the unicellular alga Chlorella pyrenoidosa; for example, after autotrophic growth in high CO2 (5·5% by volume), transfer to a CO2 concentration about ten times less than the concentration in air results initially in low rates of photosynthesis characterized by the virtual absence of the Calvin cycle1 of CO2 fixation2. An induction period of about 2 h is necessary before normal photosynthetic rates are established. Cells grown in air (0.03% CO2) do not show this effect and photosynthesize at comparatively high rates even in very low concentrations of CO2. 相似文献
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The Effects of Salinity upon Galactosyl-Glycerol Content and Concentration of the Marine Red Alga Porphyra purpurea (Roth) C.Ag. 总被引:2,自引:0,他引:2
REED ROBERT H.; COLLINS JULIAN C.; RUSSELL GEORGE 《Journal of experimental botany》1980,31(6):1539-1554
Changes in the major alcohol-soluble, low molecular weight carbohydratesof P. purpurea, O--D-galactopyranosyl-(1-2)-glycerol (floridoside)and O--D-galactopyranosyl-(1-1)-glycerol (isofloridoside),have been examined in response to salinity variation. Floridosideis shown to vary in absolute amount, increasing in hypersalineand decreasing in hyposaline media. Isofloridosidecontent per cell does not change in a similar manner. Responsesare almost identical under light or dark conditions, floridosidechanges being complete within 24 h. Decreasing the externalwater potential using ionic and non-ionic solutes has the sameeffect upon galactosyl-glycerol content. The amount of floridosidesynthesized, and degraded under hypersaline and hyposaline conditionsrespectively is shown to be insufficient to restore cell volumeto its original value. It is therefore suggested that the primaryfunction of floridoside increases in concentratedsea-waters is that of a compatible solute, serving to protectthe cell during periods when the external salt content is increaseddramatically. 相似文献
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CHARLES A. REED 《American anthropologist》1972,74(4):944-945
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TIMOTHY M. REED 《Biological journal of the Linnean Society. Linnean Society of London》1984,21(4):431-437
A multiple regression analysis was performed to establish relationships between the number of breeding landbird species and selected environmental variables for the Isles of Scilly, England.
Two analyses were made: the first with all variables log converted, the second without log conversion. In the log model the number of landbird species ( S ) was correlated with island area, r2 = 85.98. In the non-log model, S was most highly correlated with the number of habitats on an island.
Partial correlation analyses confirmed the importance of habitats, rejecting the importance of island area, and indicating that increasing intra-archipelagal isolation alone does not reduce the number of breeding species. 相似文献
Two analyses were made: the first with all variables log converted, the second without log conversion. In the log model the number of landbird species ( S ) was correlated with island area, r
Partial correlation analyses confirmed the importance of habitats, rejecting the importance of island area, and indicating that increasing intra-archipelagal isolation alone does not reduce the number of breeding species. 相似文献