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  • 1
    Electronic Resource
    Electronic Resource
    Methionine loss during protein hydrolysis of plant material (1969)
    s.l. : American Chemical Society
    Journal of agricultural and food chemistry 17 (1969), S. 668-669 
    Details
    ISSN: 1520-5118
    Source: ACS Legacy Archives
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jf60163a019
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  • 2
    Electronic Resource
    Electronic Resource
    Inorganic carbon fixation and metabolism in maize roots as affected by nitrate and ammonium nutrition (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 89 (1993), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effects of NO−3 and NH+4 nutrition on the rates of dark incorporation of inorganic carbon by roots of hydroponically grown Zea mays L. cv. 712 and on the metabolic products of this incorporation, were determined in plants supplied with NaH14CO3 in the nutrient solution. The shoots and roots of the plants supplied with NaH14CO3 in the root medium for 30 min were extracted with 80%; (v/v) ethanol and fractionated into soluble and insoluble fractions. The soluble fraction was further separated into the neutral, organic acid, amino acid and non-polar fractions. The amino acid fraction was then analyzed to determine quantities and the 14C content of its individual components.The rates of dark incorporation of inorganic carbon calculated from H14CO−3 fixation and attributable to the activity of phosphoenolpyuvate carboxylase (EC 4.1.1.31), were 5-fold higher in ammonium-fed plants than in nitrate-fed plants after a 30-min pulse of 14C. This activity forms a small, but significant component of the carbon budget of the root. The proportion of 14C located in the shoots was also significantly higher in ammonium-fed plants than in nitrate-fed plants, indicating more rapid translocation of the products of dark fixation to the shoots in plants receiving NH+/sp4 nutrition.Ammonium-fed plants favoured incorporation of 14C into amino acids, while nitrate-fed plants allocated relatively more 14C into organic acids. The amino acid composition was also dependent on the type of nitrogen supplied, and asparagine was found to accumulate in ammonium-fed plants. The 14C labelling of the amino acids was consistent with the diversion of 14C-oxaloacetate derived from carboxlyation of phosphoenolpyruvate into the formation of both asparatate and glutamate. The results support the conclusion that inorganic carbon fixation in the roots of maize plants provides an important anaplerotic source of carbon for NH+4 assimilation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1993.tb05226.x
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  • 3
    Electronic Resource
    Electronic Resource
    Short Ion-exchange Column Method for the Estimation of Cystine and Methionine (1966)
    [s.l.] : Nature Publishing Group
    Nature 209 (1966), S. 1239-1240 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] To avoid the loss of cystine and methionine during acid hydrolysis in the presence of carbohydrates3'4, performic acid oxidation of cystine to cysteic acid and methionine to methionine sulphone is first carried out as follows: sufficient dry, powdered material to contain about 10 mg of nitrogen ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/2091239a0
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  • 4
    Electronic Resource
    Electronic Resource
    Phloem bleeding from legume fruits—A technique for study of fruit nutrition (1974)
    Springer
    Planta 120 (1974), S. 229-243 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Bleeding from phloem of cut distal tips of attached fruits was demonstrated in the genera Spartium, Genista, Lupinus and Jacksonia. Bleeding occurred over a 2–25 min period enabling 0.5–10 μl of sap to be collected from a fruit. A detailed study of Lupinus albus L. showed that exudation rate declined exponentially after cutting, but without any change with time in solute levels in exudate. Bleeding resumed at its initial rate and solute concentration on recutting the fruit tip. Phloem exudates had a high pH (7.8-8.0), a sucrose content of 100–210 mg ml-1 but only traces of monosaccharides. Surrounding pod tissues contained only 15–35 mg ml-1 of sugars (tissue water basis) more than two thirds of this monosaccharide. Amino compounds were present in phloem exudates at 8–28 mg ml-1, asparagine and glutamine predominating but a wide spectrum of other amino acids being also present. No significant differences in levels of organic solutes were observed in phloem exudates collected from tips of attached versus detached fruits, from phloem exudates collected from fruit tips versus pedicels, or from basal versus distal ends of a detached fruit. Potassium was the major cation (1.5–2.2 mg ml-1) of the phloem exudate, Ca2+ was at a much lower level than either Mg2+ or Na+. Trace element levels in phloem exudates appeared to be influenced by availability to the plant from the rooting medium. Nitrate was absent though detectable in non-vascular tissues of the shoot. 14C- labelled assimilates were detected in exudates of L. albus one hour after feeding a source leaf 14CO2; sucrose, organic acids and certain amino compounds achieved high specific labelling. 14CO2 feeding studies coupled with the phloem bleeding technique revealed highly specific source-sink relationships between foliar organs and fruits of the primary inflorescence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00390291
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  • 5
    Electronic Resource
    Electronic Resource
    Xylem to phloem transfer of solutes in fruiting shoots of legumes, studied by a phloem bleeding technique (1975)
    Springer
    Planta 122 (1975), S. 11-26 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Comparisons were made of the levels of various solutes in xylem (tracheal) sap and fruit tip phloem sap of Lupinus albus (L.) and Spartium junceum (L.). Sucrose was present at high concentration (up to 220 mg ml-1) in phloem but was absent from xylem whereas nitrate was detected in xylem (up to 0.14 mg ml-1) but not in phloem. Total amino acids reached 0.5–2.5 mg ml-1 (in xylem) versus 16–40 mg ml-1 in phloem. Phloem: xylem concentration ratios for mineral nutrients (K, Na, Mg, Ca, Fe, Zn, Mn, Cu) spanned the range 0.7 to 20, the ratios generally reflecting an element's phloem mobility and its availability to the xylem from the roots. The accessibility of nitrate to xylem and phloem was studied in Lupinus. Increasing the nitrate supply to roots from 100 to 1000 mg NO3−Nl-1 increased nitrate spill over into xylem, but nitrate always failed to appear in phloem. However, phloem loading of small amounts of nitrate was induced by feeding 750 or 1000 mg NO3−Nl-1 directly to cut shoots via the transpiration stream. Transfer of reduced nitrogen to phloem was demonstrated by feeding 15NO3 to shoots and recovering 15N-enriched amides and amino acids in phloem sap. Increased nitrate supply to roots led to increased amino acid levels in xylem and phloem but did not alter markedly the balance between individual amino acids. The fate of xylem-fed 14C-labelled asparagine, glutamine and aspartic acid and of photosynthetically fed 14CO2 was studied in Spartium, with reference to phloem transport to seeds. Substantial fractions of the 14C of all sources appeared in non-amino compounds. [14C]asparagine passed largely in unchanged form to the phloem whereas the 14C from aspartic acid or glutamine appeared in phloem attached to other amino acids (e.g. asparagine and glutamic acid). Serine, asparagine and glutamine were the main amino compounds labelled in phloem sap after feeding 14CO2. The wide distribution of 14C amongst free and bound amino acids of seeds suggested that extensive metabolism of phloem-borne solutes occurred in the fruits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00385400
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  • 6
    Electronic Resource
    Electronic Resource
    Glutamine as a major acceptor of reduced nitrogen in leaves (1975)
    Springer
    Planta 125 (1975), S. 77-80 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The feeding of K15NO3 via the xylem stream to photosynthesising leaves of Datura stramonium L. shows a massive routing of 15N to glutamine, increasing with rise in the N-feeding level (between 0 and 400 μg N ml-1). At each feeding level the glutamine and glutamate pools have very similar 15N enrichment despite disparity in pool size. Amino-compound pool-size and 15N enrichment do not increase above the 300 μg ml-1 feeding level which corresponds to the normal level of nitrate-N in the xylem stream of the experimental plants. Thus, the rôle of glutamine as an N storage compound and ammonia “detoxifier” in many plants extends to the incorporation of photosynthetically reduced N newly produced in Datura leaves; the level of N incorporation into glutamine is apparently dependent on the level of nitrate feeding and the degree of induction of nitrate-reducing enzymes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00388876
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  • 7
    Electronic Resource
    Electronic Resource
    Seasonal allocation of dry mass and nitrogen in a fynbos endemic Restionaceae species Thamnochortus punctatus Pill. (1987)
    Springer
    Oecologia 72 (1987), S. 315-320 
    Details
    ISSN: 1432-1939
    Keywords: Allocation patterns ; Restionaceae ; Nitrogen ; Dry mass ; Fynbos
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The annual growth pattern of male plants of the endemic, dioecious fynbos species, Thamnochortus punctatus, revealed sequential growth of the various below-and above-ground organs. Root and rhizome development were favoured in the wet winter months while culm elongation occurred in the warmer but drier spring to summer period. The reproductive phase of development followed in the hot dry summer and autumn. The asynchronous pattern of growth is suggested to enable the plant to maximize utilization of scarce resources within the confines of the environmental controls determined by the mediterranean-climate. Maximum root and rhizome activity in the rainy season enabled the plant to absorb and store nitrogen in mature culms for later above ground organ development. As the absorption of nitrogen from senscing material is essential for this pattern of organ development to assist in alleviating nutrient scarcity the high degree of nitrogen reabsorption, 35 to 70% for branches and culms respectively, shows the potential importance of asynchronous organ growth in overcoming nitrogen limitation of plant growth. Comparisons of dry mass and nitrogen allocation patterns indicate that developmental strategies employed by evergreen, perennial plants in climatically and edaphically constrained environments cannot be deduced from biomass allocation patterns alone as they do not appear to reflect strategies evolved to overcome nutrient limitation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379284
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  • 8
    Electronic Resource
    Electronic Resource
    The assimilation of ammonium by barley roots (1983)
    Springer
    Planta 159 (1983), S. 483-486 
    Details
    ISSN: 1432-2048
    Keywords: Ammonium assimilation ; Glutamate dehydrogenase ; Hordeum ; NH 4 + assimilation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Enzyme assays of the roots of barley (Hordeum vulgare L.) fed NH 4 + show high glutamate-dehydrogenase (GDH; EC 1.4.1.3) activity compared with glutamine-synthetase (GS; EC 6.3.1.2) activity, indicating that GDH may be involved in ammonium assimilation in the root. When 15NH 4 + is fed to barley roots, a high accumulation of 15N takes place in free amino compounds, particularly glutamine and glutamate. When the GS inhibitor, methionine sulfoximine (MSO), is added to the 15NH 4 + feeding medium the free amino compounds remain unlabelled while 15NH 4 + accumulates rapidly in the roots. Root enzyme assays demonstrate that GS is completely inhibited by MSO treatment, while the activity of GDH remains unaffected. The feeding of 15N-amido glutamine to the roots in the presence of MSO and the subsequent 15N enrichment of the free amino compounds of the root show that MSO does not interfere substantially with nitrogen assimilation after the formation of glutamine. These results indicate that in the barley root, ammonium absorbed from the soil is assimilated entirely via the GS-glutamate synthase (GOGAT) pathway, and that GDH plays little, if any, part in this process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00409136
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  • 9
    Electronic Resource
    Electronic Resource
    Soil nitrogen mineralization in a coastal fynbos succession (1988)
    Springer
    Plant and soil 106 (1988), S. 295-298 
    Details
    ISSN: 1573-5036
    Keywords: fynbos ; fire ; mineralization ; nitrification ; succession
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Patterns of net nitrogen mineralization and nitrification in 0–7.5 cm deep mineral soils of different stages (seral ages 1, 6 and 20 years) of a post-fire coastal fynbos succession were assayed using laboratory andin situ incubations. No evidence of increasing allelopathic inhibition of nitrification with successional development was found as NO3−N was the predominant product at all seral stages and the NO3−N∶NH4−N ratio remained constant. Rather the results of field incubations of soils beneathProtea repens stands of different successional ages showed that increased mineralization and nitrification appeared to be associated with increased soil total N content rather than with successional age. Further, the incubation of soilsin situ during the dry summer months showed that NO3−N production appears to be closely related to temperature and soil moisture content, both of which are variables that vary throughout succession due to the changing structure of the vegetation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02371229
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  • 10
    Electronic Resource
    Electronic Resource
    The effect of nitrate feeding levels on the pathway of nitrogen incorporation into photosynthesizing leaf metabolism ofDatura stramonium L (1978)
    Springer
    Plant and soil 49 (1978), S. 625-631 
    Details
    ISSN: 1573-5036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Datura stramonium leaves fed K15NO3 at 25 μg N ml−1 and 200 μg N ml−1 for 7 and 17 min show that at both time courses the main route of newly reduced nitrogen is to glutamate at the low N-feeding level, and to glutamine at the high N-feeding level. At the high N-feeding level the amido-N of glutamine shows higher15N enrichment than the amino-N, whereas at the low N-feeding level the opposite is true. Feeding of glutamine (15N amido labelled) at the 25 and 200 μg N ml−1 level produces15N enrichment of leaf amino acids, the prime routing being to glutamate. This indicates the operation of glutamate synthase at both feeding levels. It is possible that inDatura stramonium leaves both the glutamate dehydrogenase and glutamine synthetase/GOGAT pathways are simultaneously operative, the former route being favoured at low N-feeding levels, the latter at high N-feeding levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02183286
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