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  • Nostoc calcicola  (4)
  • Hg2+ toxicity  (2)
  • Leafdrop  (2)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    BioMetals 3 (1990), S. 208-212 
    ISSN: 1572-8773
    Schlagwort(e): Hg2+ toxicity ; Nostoc calcicola ; Electrolyte leakage ; NO3 − uptake ; Nitrate reductase ; Metal interactions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary The effect of mercury (Hg2+) in the absence and presence of methylmercury (CH3Hg+), cadmium (Cd2+), copper (Cu2+), nickel (Ni2+) and calcium (Ca2+) on Nostoc calcicola Bréb. has been studied in terms of electrolyte leakage, NO3 − uptake and in vivo nitrate reductase (NR) activity to discover any possible correlation among such parameters under Hg2+ stress. Leakage of electrolytes from Hg2+-treated cyanobacterial cells was directly proportional to Hg2+ concentrations and exposure time. In comparison to NO3 − uptake, an about 60-fold slower rate of NR activity was observed in the untreated cultures, the former being five times more Hg2+-sensitive. A non-competitive synergistic interaction of Hg2+ with CH3Hg+ or Cd2+ and antagonistic with that of Ni2+ or Ca2+ has been observed for both the processes of NO3 − utilization. The antagonistic interaction of Cu2+ with Hg2+ in terms of NO3 − uptake and synergistic with respect to NR activity, has been attributed to the dual bonding preference of Cu2+ for cellular ligands. These findings suggest that (a) a statistically significant correlation exists among such parameters; (b) Hg2+ predominantly attacks the cyanobacterial cell membrane; (c) Hg2+ inhibits NO3 − utilization; (d) the presence of other cations increases or decreases the inhibitory actions of Hg2+.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    BioMetals 5 (1992), S. 229-234 
    ISSN: 1572-8773
    Schlagwort(e): biofilm ; cell aging ; cyanobacterium foam ; immobilization ; Nostoc calcicola ; spheres
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Methyl mercury uptake in free cells and different immobilizates of the cyanobacteriumNostoc calcicola has been examined. The general growth of the immobilized cyanobacterial cells could be negatively correlated with methyl mercury uptake. Alginate spheres proved most efficient in terms of uptake rate (0.48 nmol mg protein−1 min−1, 10 min) and total bioaccumulation (10.71 nmol mg protein−1, 1 h) with a bioconcentration factor of 3.3×103. Alginate biofilms showed a faster methyl mercury accumulation rate (0.83 nmol mg protein−1 min−1, 10 min) with a saturation of 10.28 nmol mg protein−1 reached within only 30 min (bioconcentration factor, 3.1×103). Foam preparations with a slow initial uptake approximated biofilms but were characterized by a lower bioconcentration factor (2.8×103). Free cells, in comparison, maintained the initial slow rate of uptake (0.62 nmol mg protein−1 min−1, 10 min), saturating at 30 min (8.81 nmol mg protein−1), and the resultant lowest bioconcentration factor (2.7×103). Cell ageing (30 days) brought a drastic reduction (3-fold) in organomercury uptake by free cells while alginate spheres maintained the same potential. Foam preparations of the same age showed a significant improvement in methyl mercury uptake followed by only a marginal decline in alginate biofilms. Data are discussed in the light of the physiological efficiency and longevity of immobilized cells.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    BioMetals 4 (1991), S. 192-196 
    ISSN: 1572-8773
    Schlagwort(e): Cu uptake ; Starvations ; Recovery ; ATP ; Nostoc calcicola
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary The kinetics of Cu uptake in nutritionally starved cells of the diazotrophic cyanobacteriumNostoc calcicola Bréb. have been compared with those in cells recovering from starvation. Unstarved cyanobacterial cells assimilated 97.0 nmol Cu mg−1 protein within 1 h when incubated in medium containing 40 μM Cu. Uptake was markedly inhibited in carbon-starved cells and, to a lesser extent, in cells starved of nitrogen or sulphur. The intracellular concentrations of protein and photopigments were markedly lower in cells starved of carbon, nitrogen, sulphur or phosphorus, whilst that of carbohydrate was lower in cells starved of carbon, sulphur or phosphorus, but almost doubled in cells starved of nitrogen. The ability to assimilate Cu was partially restored in cells after 72 h of recovery from phosphorus or sulphur deprivation, but showed little improvement during recovery from carbon or nitrogen starvation. A possible role of phosphorus in regulating Cu transport and accumulation is discussed.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    BioMetals 5 (1992), S. 149-156 
    ISSN: 1572-8773
    Schlagwort(e): Hg2+ toxicity ; cyanobacterium ; Nostoc calcicola ; growth ; photopigments ; nucleic acids ; photosynthesis ; membrane integrity ; nutrient uptake ; enzymes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Toxicological responses of the filamentous N2-fixing cyanobacteriumNostoc calcicola Bréb. towards Hg2+ were studied to enumerate the decisive lethal events. In low-dose, long-term experiments (0.05–0.25 μm Hg2+, 10 days), photoautotrophic growth was severely inhibited with concurrent loss of photosynthetic pigments (phycocyanin〉chlorophyll α〉carotenoids) and nucleic acids. The termination of growth after a day 4 exposure to 0.25 μm Hg2+ has been attributed to the complete inhibition ofin vivo photosynthetic activity in the cyanobacterium (O2 evolution〉14CO2 incorporation). The elevated Hg2+ concentrations irreversibly damaged the cell membrance as observed under light microscopy, and as indicated by the leakage of intracellular electrolytes and phycocyanin. In high-dose, short-term experiments (0.5–20.0 μm Hg2+, up to 6 h), thein vivo activities of selected enzymes (glutamine synthetase 〉 nitrate reductase 〉 nitrogenase) were less inhibited by Hg2+ than the uptake of nutrient ions (NH 4 + 〉NO 3 − 〉PO 4 3− ).
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Plant ecology 63 (1985), S. 113-119 
    ISSN: 1573-5052
    Schlagwort(e): Flowering ; Fruiting ; Leafdrop ; Leaf flushing ; Kumaun Himalayan forest ; Phenology ; Shrub layer phenology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The phenology of 49 shrub species in five forest types occurring along an altitudinal gradient (350–2150 m) in Kumaun Himalaya has been studied. The evergreen leaf-exchanging taxa accounted for nearly half of the species, the remaining half was nearly equally divided between an evergreen continual leaf drop type and deciduous taxa. The percentage of species with lengthy leaf drop increased with elevation and finally leveled off. At each site the maximum leaf drop period coincided with the warm dry period. Percentage of species with multiple leaf flushing was low for all forests. The degree of extended leafing decreased with increasing elevation along which summer dryness also decreased. Earliest leaf initiation was observed for evergreen continual leaf drop species, followed by evergreen leaf-exchanging, and deciduous types. For each forest, two peaks of flowering activity occurred, one during the warm dry period and the other in the warm wet period. The percentage of species with multiple flowering increased with increasing elevation. Nearly half of the species bore fleshy fruits. The mature fruit retention period for different forests ranged from about 2–3 months. The proportion of deciduous species was similar in trees and shrubs; leaf drop was common during the summer season for trees, while it was common during the winter season for shrubs; the proportion of species with multiple leafings was greater and leaf initiation earlier in shrubs than trees; and generally shrubs showed two flowering peaks and trees only one.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Plant ecology 60 (1985), S. 91-101 
    ISSN: 1573-5052
    Schlagwort(e): Flowering ; Forest ; Fruiting ; Kumaun Himalaya ; Leafdrop ; Leaf flushing ; Phenology ; Phenological activity level ; Treelayer phenology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The phenology of tree components of natural forests occurring between 350 and 2150 m in Kumaun Himalaya is descibed. All forests had more evergreen than deciduous taxa. The degree of evergreenness increased with increasing elevation and decreasing summer dryness. For most species (including all dominants) concentrated leafdrop and simultaneous leafing occurred during the warm-dry period of the year. About half of the species showed multiple leafing. All species had a sharp flowering peak in April. Wet-season flowering was rare. Most of the species flowered synchronously. In the sal- (Shorea robusta) and pine (Pinus roxburghii) forests a single peak of fruit maturation occurred in summer, while in other forests there also was a secondary peak in autumn.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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