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  • 1
    Electronic Resource
    Electronic Resource
    Light and dark assimilation of nitrate in plants (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 6 (1983), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Heterotrophic assimilation of nitrate in roots and leaves in darkness is closely linked with the oxidative pentose phosphate pathway. The supply of glucose-6-phosphate to roots and chloroplasts in leaves in darkness is essential for assimilation of nitrite into amino acids. When green leaves are exposed to light, the key enzyme, glucoses-phosphate dehydrogenase, is inhibited by reduction with thioredoxin. Hence the dark nitrate assimilatory pathway is inhibited under photoautotrophic conditions and replaced by regulatory reactions functioning in light. On account of direct photo-synthetic reduction of nitrite in chloroplasts and availability of excess NADH for nitrate reduclase, the rate of nitrate assimilation is extremely rapid in light. Under dark anaerobic conditions also nitrate is equally rapidly reduced to nitrite on account of abolition of competition for NADH between nitrate reductase and mitochondrial oxidation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11589193
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  • 2
    Electronic Resource
    Electronic Resource
    Photorespiratory nitrogen cycle – A critical evaluation (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 66 (1986), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The photorespiratory nitrogen cycle proposed by Keys et al. (Nature 275: 741–743, 1978) involved formation of glycine by transamination of glyoxylate in the peroxisomes utilizing glutamate. Subsequently, glycine is oxidized to ammonia, serine and CO2 in the mitochondria. The ammonia is reassimilated via the GS/GOGAT pathway generating glutamate. In this article, experimental evidence which suggests the occurrence of alternative mechanisms of glycolate and serine synthesis as well as of CO2 and ammonia evolution is discussed. The problem of utilization of NADH coupled to ATP synthesis during photosynthesis is still unresolved, which complicates the glycine oxidation reaction in light. Further, factors are presented that determine the availability of amino donors in the peroxisomes and of amino acids viz., glycine, serine and glutamate for the operation of the photorespiratory N cycle. Recent evidence regarding the role of formate arising out of the reaction of glyoxylate with H2O2 in the regulation of photosynthetic electron flow in the Hill reaction, as well as of photorespiratory substrates functioning as carbon sources for the citric acid cycle in the light or for export to the growing tissues, suggests that the role of photo-respiration in plant metabolism needs to be reexamined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1986.tb01252.x
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  • 3
    Electronic Resource
    Electronic Resource
    Nitrate Assimilation in Rice Grown under Lowland Conditions (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 47 (1979), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Pattern and extent to which the main shoot of rice (Oryza sativa L.) cv. Pusa 33 assimilates NO3- when grown under lowland conditions was determined in a field study. The in vivo NR (nitrate reductase) activity is low as compared to the value in other cereals grown under aerobic soil conditions. The leaf blades had higher NR activity (g fr. wt.)-1 than the sheaths and stem. Calculation of total NO3- (mol) reduced in the main shoot, obtained by integrating the in vivo NR assay values per plant part and per day over the duration for which the various plant parts on the main shoot remained metabolically active, showed that out of the total reduced N at harvest, 16.6% was assimilated via the enzyme nitrate reductase. In the leaf sheaths and stem the NO3- was reduced to slightly over 50% of the total NO3- that was reduced in the main shoot. The rest of the amount was reduced in the leaf blades.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1979.tb03205.x
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  • 4
    Electronic Resource
    Electronic Resource
    Nitrate assimilation in leaf blades of wheat of different age (1980)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 48 (1980), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A field experiment on wheat (Triticum aestivum L.) ev. Shera grown at 120 kg N ha−1 was conducted. Half of the dose of fertilizer N was applied at the pre-sowing stage and the other half when the seedlings were one month old. The leaf blades were examined for their NO3− content and NO3− assimilatory activity at various stages of growth and development. Soil nitrate level at 50 cm depth was determined throughout the wheat growing season in terms of cencentration (μg/ml) and total amount (kg ha−1). The upper leaf blades were examined for their capacity to assimilate NO3−. Highly significant correlation between NR (nitrate reductase) activity and NO3− content in the leaf blades. NR activity and soil NO3−, and between soil NO3− and leaf blade NO3− was observed. Findings on low soil NO3− status during the reproductive phase and the capacity of the upper leaf blades to assimilate additional amounts of NO3−, point to the need for developing a programme of soil fertilizer application whereby all the leaf blades can utilize the NO3− optimally and thus result in greater N harvest.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1980.tb03289.x
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  • 5
    Electronic Resource
    Electronic Resource
    Nitrogen Metabolism of the Upper Three Leaf Blades of Wheat at Different Soil Nitrogen Levels (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 42 (1978), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Some aspects of nitrogen metabolism, during grain development, of the upper three leaf blades on the mainshoot of wheat (Triticum aestivum L.) cv. Pusa Lerma, grown under three soil nitrogen levels (0, 30 and 120 kg ha-1), were investigated. It was observed that these leaf blades were active in NO-3 assimilation. Of the leaf blades, the flag lead blade had significantly higher nitrate reductase activity, higher amount of free amino acid and soluble protein content, whereas the content of NO-3 was significantly lower than in the other two leaf blades. Application of soil nitrogen significantly enhanced the nitrate reductase activity (N30 over N0 and N120 over N30), free amino acid (N30 over N0 and N120 over N30), soluble protein (N120 over N0) and NO-3 content (N30 and N120 over N0) in all three leaf blades. During the 35-day period, viz. from 7 days prior to anthesis to 28 days after anthesis, the three leaf blades together reduced 280, 608 and 1397 NO-3μmol under N0, N30 and N120, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1978.tb04084.x
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  • 6
    Electronic Resource
    Electronic Resource
    Nitrogen Metabolism of the Upper Three Leaf Blades of Wheat at Different Soil Nitrogen Levels (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 42 (1978), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Upper three leaf blades on the mainshoot of wheat cultivar, cv. Pusa Lerma, grown under three soil nitrogen levels (0, 30 and 120 kg ha-1), were examined for changes in total reduced nitrogen and protease activity at pH 4.0 and 7.0. No net loss of reduced nitrogen takes place prior to and around anthesis. The protease activity is low during this period. At later stages there is rise in the loss of nitrogen which is paralleled by enhancement in protease activity. From amongst the leaf blades, nitrogen concentration is significantly high in the flag and penultimate as compared to the values in the third leaf blade. There were significant differences in protease activity (pH 4.0) amongst the leaf blades. At pH 7.0, however, the differences between the flag and penultimate leaf blades were not significant. Highest enzyme activity was in the flag followed by penultimate and then third leaf blade. Soil N application significantly enhanced the nitrogen content of all the leaf blades. At pH 4.0, the protease activity (g fr. wt.-1) increased significantly due to soil N application (N30 over N0). There was, however, decline in the enzyme activity at pH 7.0, though the differences at different soil N levels were not significant. Analysis in terms of μmol N (reduced form) accumulated in the grains (ear)-1 revealed that two-thirds of N is translocated by 28-day stage and the rest between 28-day and final harvest. The three leaf blades together contributed 22.7, 32.6 and 48.5% of the grain N (ear)-1 at N0, N30 and N120- respectively. Most of the nitrogen applied to the soil is reduced by these leaf blades.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1978.tb04085.x
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  • 7
    Electronic Resource
    Electronic Resource
    Composition of Bleeding Sap in Vigna radiata (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 42 (1978), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Bleeding sap and nodules from Vigna radiata were analysed for their free amino nitrogen content and amino acid composition at different stages of growth and development. The bleeding sap contained mostly basic amino acids, whereas the nodules contained both acidic and basic amino acids. The amino nitrogen content of the bleeding sap increased during growth and then declined appreciably during fruit development. In contrast, nodule amino nitrogen declined from seedling stage onwards till flowering, increased during fruit development and then declined again. Nitrate reductase activity in the leaves examined at different stages of development increased from seedling stage onwards and was maximum during early fruit-development stage. It declined during pod-filling stage. The study suggests that the amount of nitrogen fixed from the atmosphere is insufficient, so that the plant has to draw upon soil nitrogen as well. This may be necessary due to the high demand of nitrogen during pod filling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1978.tb01536.x
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  • 8
    Electronic Resource
    Electronic Resource
    Nitrate reductase activity in developing wheat ears (1973)
    Springer
    Cellular and molecular life sciences 29 (1973), S. 1480-1481 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Zusammenfassung Die Fruchtstände der Weizenpflanzen reduzieren während ihrer Entwicklung beachtliche Mengen von Nitratstickstoff.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01943867
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  • 9
    Electronic Resource
    Electronic Resource
    An example of active transport of water through plants (1968)
    Springer
    Cellular and molecular life sciences 24 (1968), S. 304-304 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Zusammenfassung Am Beispiel des Wassertransports aus Samen der Tomate wird das Vorkommen eines aktiven Wassertransportmechanismus in Pflanzen nachgewiesen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02152835
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of exogenous supply of amino acids, amide, urea and ureide on free NH4 + level in mung beans (1983)
    Springer
    Cellular and molecular life sciences 39 (1983), S. 1302-1303 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The results of experiments on the possible source(s) of ammonia for the mung bean are reported. Different nitrogenous metabolites were fed to primary leaves of mung bean seedlings with and without methionine sulphoximine (MSO), an inhibitor of glutamine synthetase (GS). Their role in foliar ammonia loss is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01990381
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