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Influence of selected abiotic factors on the decomposition of chlorophylls

100%
Kowalewska G., Szymczak M.
Oceanologia
|
2001
|
tom 43
|
nr 3
315-328
The paper presents the results of experiments to determine the influence of selected physico-chemical factors – oxygen, visible light and temperature – on the decomposition of (1) chlorophylls a, b and c, chlorophyll a derivatives and β-carotene in acetone solution, and (2) chlorophyll a and β-carotene in axenic cultures of the blue-green algae Anabaena variabilis. The results indicate that both in acetone extracts and in blue-green algae cultures these pigments were most sensitive to light and oxygen; temperatures of up to 25◦C had no marked influence on these compounds. Under anoxia in acetone solution, the stability towards light decreased in the order chlorophyll a, chlorophyll b, chlorophylls c. Chlorophyll a, moreover, was less stable than its derivatives – phaeophorbides, phaeophytins, pyrophaeophytins and steryl chlorins – but more stable than β-carotene, in the last case also in the blue-green algae cultures. Decomposition of all the pigments proceeded mainly via the breakdown of the porphyrin macrocycle, since the decomposition products were not detected in the VIS range. On the basis of these experiments one can state that while light and oxygen may have a decisive direct influence on the distribution of chlorophylls and β-carotene in sediments, in the natural environment, temperatures of up to 25◦ C may have very little immediate effect.
2

Effects of tropical solar radiation on the velocity and photophobic behavior of filamentous gliding cyanobacteria

84%
Donkor V. A., Amewowor D. H. A. K., Hader D. P.
Acta Protozoologica
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1993
|
tom 32
|
nr 2
3

Nutrient modulated alkaline phosphatase and associated processes in diazotrophic cyanobacteria

67%
Pandey M.
Polish Journal of Microbiology
|
2006
|
tom 55
|
nr 1
Nutrient regulation of alkaline phosphatase (Phosphomonoesterase - PMEase) was studied in some diazotrophic cyanobacterial strains like Anabaena variabilis, Anabaena torulosa, Calothrix brevissima, Scytonema javanicum and Hapalosiphon intricatus, in response to the macronutrients (Phosphate, Calcium and Magnesium) and the micronutrients (Zinc, Copper, Iron and Manganese). The phosphate grown cells of cyanobacterial strains when transferred to the phosphate deficient medium, showed expression of cellular PMEase activity and released the enzyme extracellularly. The increased concentration of phosphate inhibited enzyme activity severely in a concentration dependent manner. The phosphate depletion stimulated spore formation in A. variabilis and H. intricatus, whereas its addition enhanced spore's differentiation in A. torulosa. The switch-on time detected for both cellular and extracellular PMEase varies among the strains. The increase in ionic concentration of Ca²⁺ enhanced the PMEase activity more profoundly than Mg²⁺ in diazotrophic strains. The lower level of micronutrients either promoted or had no effect on photosynthetic inhibitors (DCMU) and respiratory electron transport chain inhibitor (sodium azide). It revealed that the energy for the synthesis of PMEase enzyme is mostly derived from photosynthesis and the role of respiratory energy is marginal. The Phosphate (Pi) uptake function in the strains was found to be substrate concentration dependent.
4

Effects of siderophores and amino acids on the growth and photosynthesis of populations of Chlorella vulgaris Beijerinck and Anabaena variabilis Kutzing

59%
Surosz W., Kosakowska A.
Oceanologia
|
1996
|
tom 38
|
nr 4
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