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  • 1
    Electronic Resource
    Electronic Resource
    Regulation of growth, water use efficiency and δ13C by the nitrogen source in Casuarina equisetifolia Forst. & Forst. (1998)
    Oxford, UK : Blackwell Science Ltd, UK
    Plant, cell & environment 21 (1998), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Carbon isotope composition (δ13C) was measured in a glasshouse experiment with N2-fixing and NO3–- or NH4+-fed Casuarina equisetifolia Forst. & Forst plants, both under well-watered and drought conditions. The abundance of 13C was higher (more positive δ13C) for NH4+- than for NO3– -grown plants and was lowest for N2-fixing plants. NH4+-fed plants had more leaf area and dry weight and higher water use efficiency (on a biomass basis) than N2- and NO3–-grown plants and had lower water consumption than plants supplied with NO3–, either with high or low water supply. Specific leaf areas and leaf area ratios were higher with NH4+ than with NO3– or N2 as the N source. The difference observed in δ13C between plants grown with different N sources was higher than that predicted by theory and was not in the right direction (NH4+-grown plants with a more negative δ13C) to be explained by differences in plant composition and engagement of the various carboxylation reactions. The more positive δ13C in NH4+- than in NO3–-grown plants is probably due to a decreased ratio of stomatal to carboxylation conductances, which accounts for the lower water cost of C assimilation in NH4+-grown plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1998.00302.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of the ecto- and VA-mycorrhizal fungi Hydnagium carneum and Glomus clarum on the δ15N and δ13C values of Eucalyptus globulus and Ricinus communis (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 16 (1993), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Glasshouse experiments with Ricinus communis showed that the presence/absence of a VA mycorrhizal fungus (Glomus clarum) changed the δ15N value of the host by as much as 2‰ when the plants were given urea (released as NH4+) as their only N-source. This small change in Δ15N would create a large error in calculating sources of plant N. In particular, these results throw into doubt any models of N-cycling which assume that soil N can be treated as a single source. The correct N-source value for VAM-infected NH4− -using plants may be the δ15N of soil NH4++ 2‰. Treatment effects were also found in the distribution of δ15N and % N among plant organs. Plants with VAM had a lower N:P atom ratio and were larger in total biomass. Carbon discrimination (δ13C) was greater in the VA-infected plants. The measured effects of VAM infection suggest that for some plants the fungus may be the primary site of N assimilation. A parallel experiment with Eucalyptus globulus and the ectomycorrhizal fungus Hydnangium carneum resulted in no significant differences in any of the variables measured for this host-fungus pair when the sole N-sources were inorganic (NO3− and NH4+ released from urea). Ectomycorrhizal fungi are diverse in their physiological behaviour, and these data should not be taken as being representative of the whole group. More work is required with other types of mycorrhiza and more complex sources of N. Future work will include a water balance to partition the effects of water use and nutrient supply in determining δ13C. An on-line combustion-ANCA-MS method is described for fully automated measurement of natural abundance levels of 15/14N and 13/12C for plant materials. This method achieves the required precision while dramatically increasing sample throughout.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1993.tb00883.x
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  • 3
    Electronic Resource
    Electronic Resource
    Sulphur accumulation and redistribution in wheat (Triticum aestivum): a study using stable sulphur isotope ratios as a tracer system (1999)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 22 (1999), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Wheat plants were grown hydroponically and fed with two sulphate sources differing in stable isotope composition, one having a δ34S of 13·7‰ and the other 4·1‰. Plant sulphur (S) isotope ratios were determined using an on-line continuous flow-isotope ratio mass spectrometer. This method greatly simplified the procedure for the measurement of S isotope ratios, and was found to be precise for samples containing 〉 1 mg S g–1 dry weight. The δ34S values of plant shoots, which had been grown on a single sulphate source, were very close to the source values, suggesting little isotope fractionation during sulphate uptake and transport from roots to shoots. By changing the sulphate sources at different growth stages, it was possible to estimate S accumulation and redistribution within different plant parts. At maturity, wheat grain derived 14, 30, 6 and 50% of its S from the accumulation during the following successive growth stages: between emergence and early stem extension, between stem extension and flag leaf emergence, between flag leaf emergence and anthesis, and after anthesis, respectively. It was estimated that 39, 32 and 52% of the S present in the flag leaves, older leaves and stems, respectively, at anthesis, was exported during the postanthesis period. These results demonstrate considerable cycling of S within wheat plants, and highlight the importance of S uptake after anthesis to the accumulation of S in grain under the experimental conditions employed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1999.00445.x
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  • 4
    Electronic Resource
    Electronic Resource
    The structure of L-α-aminoadipic acid (1988)
    Oxford [u.a.] : International Union of Crystallography (IUCr)
    Acta crystallographica 44 (1988), S. 1762-1764 
    Details
    ISSN: 1600-5759
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108270188006997
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  • 5
    Electronic Resource
    Electronic Resource
    Shoot δ15N correlates with genotype and salt stress in barley (1997)
    Springer
    Planta 201 (1997), S. 100-102 
    Details
    ISSN: 1432-2048
    Keywords: 15N natural abundance ; Genetic variation ; Hordeum ; Salt stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Given a uniform N source, the δ15N of barley shoots provided a genotypic range within treatments and a separation between control and salt-stress treatments as great as did δ13C*. Plant δ15N has been represented in the literature as a bioassay of external source δ15N and used to infer soil N sources, thus precluding consideration of the plant as a major cause in determining its own 815N. We believe this to be the first report of plant δ15N as a genetic trait. No mechanistic model is needed for use of δ15N as a trait in controlled studies; however, a qualitative model is suggested for further testing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01258686
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  • 6
    Electronic Resource
    Electronic Resource
    A theory for 15N/14N fractionation in nitrate-grown vascular plants (1998)
    Springer
    Planta 205 (1998), S. 397-406 
    Details
    ISSN: 1432-2048
    Keywords: Key words:15N/14N ; Nitrate assimilation ; Nitrogen isotope fractionation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. We present a theory describing how the δ15N values of the nitrogen (N) pools in a vascular plant depend on that of its source N (nitrate), on 15N/14N fractionations during N assimilation, and on N transport within and N loss from the plant. The theory allows measured δ15N values to be interpreted in terms of physiological processes. The δ15N values of various N pools are calculated using three rules: (1) when a pool divides without transformation, there is no change in the δ15N values of the N entering the resulting pools; (2) when nitrate is assimilated by nitrate reductase, the δ15N values of the resulting pools (product and residual substrate) are described by a Rayleigh equation; (3) when two N pools mix, the δ15N value of the mixture is a weighted average of the δ15N values of the component pools. The theory is written as a spreadsheet and solved numerically. Potentially, it has multiple solutions. Some contravene physiological reality and are rejected. The remainder are distinguished, where possible, using additional physiological information. The theory simulated independent measurements of δ15N in N pools of Brassica campestris L. var. rapa (komatsuna) and Lycopersicon esculentum Mill. cv. T-5 (tomato).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250050336
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  • 7
    Electronic Resource
    Electronic Resource
    Post-exercise gastric emptying of carbohydrate solutions determined using the 13C acetate breath test (1995)
    Springer
    European journal of applied physiology 71 (1995), S. 306-310 
    Details
    ISSN: 1439-6327
    Keywords: Gastric emptying ; Carbohydrate ; Acetate Exercise ; Stable isotope
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In an attempt to measure gastric emptying of carbohydrate solutions after exercise, we used the 13C acetate breath test to differentiate the gastric emptying of three approximately isoenergetic carbohydrate solutions (i.e. glucose, glucose polymer and sucrose) from each other and from water. On four separate occasions, six post-absorptive subjects walked on an inclined treadmill at 70% maximum oxygen uptake for 1 h and were then given 330 ml of one of the solutions in which 150 mg of sodium 1-[13C] acetate had been dissolved. Breath samples were collected at regular (2–30 min) intervals over the next 3.5 h for analysis of expired 13CO2 by isotope ratio mass spectrometry. When water was given, all subjects reached peak breath enrichment after 30 min, and had a mean (SE) gastric emptying time of 33.2 (1.6) min. Peak breath enrichment occurred later for sucrose and glucose polymer at 54.3 (3.1) min and 59.0 (2.1) min respectively (P 〈 0.01), and for glucose this was even later, at 62.3 (1.0) min (P 〈 0.05). Calculated gastric emptying times for sucrose and glucose polymer were almost identical [66.5 (2.5) and 69.8 (2.9) min respectively], whereas that for glucose was significantly slower [76.8 (3.2) min; P 〈 0.02], probably reflecting the effects of increased osmolality. The gastric emptying of all carbohydrates were significantly longer than for water (P 〈 0.01). These results show that in the post-exercise state the 13C acetate breath test can be used to differentiate the gastric emptying rates of water and carbohydrate solutions of different properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00240409
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