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  • Glutamine synthetase  (3)
  • Allelopathy  (2)
  • Springer  (5)
  • Springer Nature
  • 1
    ISSN: 1432-2048
    Keywords: Glutamine synthetase ; Nitrate (as inductor) ; Nitrite reductase ; Phytochrome (as inductor) ; Sinapis (nitrate assimilation)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The extent to which the appearances of nitrite reductase (NIR; EC 1.7.7.1) and glutamine synthetase (GS; EC 6.3.1.2) are coordinated was studied in mustard (Sinapis alba L.) seedlings. It was established by immunotitration that the increased activities of NIR and GS in the presence of light and nitrate can be attributed to the de-novo synthesis of enzyme protein. The bulk of the NIR and GS was found in the developing cotyledons. In the absence of nitrate in the growth medium there was no coordinate appearance of NIR and GS. While light strongly stimulated the appearance of GS, the level of NIR was hardly affected and remained low. On the other hand, in the presence of nitrate in the medium the appearances of NIR and GS were strictly coordinated, the GS level being considerably above that of NIR. It is argued that phytochrome-controlled synthesis of GS in the absence of nitrate is part of the mechanism to reassimilate ammonium liberated during proteolysis of storage protein and metabolism of the resulting amino acids, whereas the strictly coordinated synthesis in the presence of light and nitrate indicates the dominance of nitrate assimilation under these circumstances. The fact that the level of GS was always considerably above that of NIR appears to be a safety measure to prevent ammonium accumulation.
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  • 2
    ISSN: 1432-2048
    Keywords: Ammonium assimilation ; Glutamine synthetase ; Nitrate ; Phytochrome ; Sinapis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During transformation of mustard seedlings cotyledons from storage organs to photosynthetically competent leaves, a process which occurs during the first 4 d after sowing, total glutamine-synthetase (GS, EC 6.3.1.2) activity increases from zero to the high level usually observed in green leaves. In the present study we have used ion-exchange chromatography to separate possible isoforms of GS during the development of the cotyledons. The approach failed since we could only detect a single form of GS, presumably plastidic GS, under all circumstances tested. The technique of selective photooxidative destruction of plastids in situ was applied to solve the problem of GS localization. It was inferred from the data that the GS as detected by ion-exchange chromatography is plastidic GS. The regulatory role, if any, of light, nitrate and ammonium in the process of the appearance of GS in the developing cotyledons was investigated. The results show that nitrate and ammonium play only minor roles. Light, operating via phytochrome, is the major regulatory factor.
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  • 3
    ISSN: 1432-2048
    Keywords: Glutamine synthetase ; Nitrate (as inductor) ; Nitrite reductase ; Phytochrome (as inductor) ; Sinapis (nitrate assimilation)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The extent to which the appearances of nitrite reductase (NIR; EC 1.7.7.1) and glutamine synthetase (GS; EC 6.3.1.2) are coordinated was studied in mustard (Sinapis alba L.) seedlings. It was established by immunotitration that the increased activities of NIR and GS in the presence of light and nitrate can be attributed to the de-novo synthesis of enzyme protein. The bulk of the NIR and GS was found in the developing cotyledons. In the absence of nitrate in the growth medium there was no coordinate appearance of NIR and GS. While light strongly stimulated the appearance of GS, the level of NIR was hardly affected and remained low. On the other hand, in the presence of nitrate in the medium the appearances of NIR and GS were strictly coordinated, the GS level being considerably above that of NIR. It is argued that phytochrome-controlled synthesis of GS in the absence of nitrate is part of the mechanism to reassimilate ammonium liberated during proteolysis of storage protein and metabolism of the resulting amino acids, whereas the strictly coordinated synthesis in the presence of light and nitrate indicates the dominance of nitrate assimilation under these circumstances. The fact that the level of GS was always considerably above that of NIR appears to be a safety measure to prevent ammonium accumulation.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 26 (2000), S. 2049-2057 
    ISSN: 1573-1561
    Keywords: Allelopathy ; alpine soils ; salicylate ; Salix ; SIGR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract We used the substrate-induced growth-response (SIGR) method to quantify salicylate-mineralizing microbes and total microbial biomass in soils from under willows (Salix brachycarpa) and in surrounding meadows dominated by the sedge Kobresia myosuroides. Willows had a strong effect on the biomass of salicylate-mineralizing microbes in both years of this study. There were always higher biomass levels of salicylate mineralizers in soils from under Salix (4.6–10.1 μg C/g) than under Kobresia (0.23–0.76 μg/g). In contrast, total microbial biomass was not significantly different under these plant species in 1996 and was only higher under Salix on one date in 1997. These results show that the standing biomass and activity of salicylate-mineralizing microbes can be greatly enhanced by salicylate-producing plants in the field. Given this finding, it is unlikely that simple phenolic compounds like salicylate would persist for very long in soil beneath the plants that produce them.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 14 (1988), S. 1561-1571 
    ISSN: 1573-1561
    Keywords: Allelopathy ; biodegradation ; humic acids ; Juglans nigra ; juglone ; nonlinear regression ; Pseudomonas putida biovar A
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Bacteria that can degrade juglone (5-hydroxy-1,4-naphthoquinone) were isolated from soil beneath black walnut trees. Autecological studies with one of these bacteria (Pseudomonas J1), demonstrated that it could grow rapidly using juglone as its sole source of carbon and energy. Using nonlinear regression analysis and the Monod equation, it was determined that this bacterium had a high affinity for juglone (K s = 0.95 μg/ml).Pseudomonas J1 can also utilize other aromatic compounds from plants as its sole source of carbon and energy. Compounds such as chlorogenic acid, ferulic acid, gallic acid, and 2-hydroxy-1,4-naphthoquinone (Lawson) were rapidly degraded byPseudomonas J1. The rapid degradation of juglone and other suspected allelochemicals by soil bacteria make it unlikely that these compounds are important mediators of plant-plant interactions under natural conditions.
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