Papers by Roland A Werner
Rapid Communications in Mass Spectrometry, 2009
The carbon isotope signatures (d 13 C) of primary photosynthates closely track changes in leaf ga... more The carbon isotope signatures (d 13 C) of primary photosynthates closely track changes in leaf gas exchange via changes in the ratio between leaf internal and atmospheric CO 2 concentration (c i :c a ), and they thus reflect the balance between foliar limitation and CO 2 diffusion and the rate of photosynthetic CO 2 fixation. 1,2 Leaf carbohydrates (starch, soluble sugars) rapidly display environmental fluctuations, often with a time lag of a few hours to days, while bulk leaf Analysis of starch and soluble sugars of plant material 2481
Oecologia, Jan 1, 2008
The 13C isotopic signature (C stable isotope ratio; δ13C) of CO2 respired from forest ecosystems ... more The 13C isotopic signature (C stable isotope ratio; δ13C) of CO2 respired from forest ecosystems and their particular compartments are known to be influenced by temporal changes in environmental conditions affecting C isotope fractionation during photosynthesis. Whereas most studies have assessed temporal variation in δ13C of ecosystem-respired CO2 on a day-to-day scale, not much information is available on its diel dynamics. We investigated environmental and physiological controls over potential temporal changes in δ13C of respired CO2 by following the short-term dynamics of the 13C signature from newly assimilated organic matter pools in the needles, via phloem-transported organic matter in twigs and trunks, to trunk-, soil- and ecosystem-respired CO2. We found a strong 24-h periodicity in δ13C of organic matter in leaf and twig phloem sap, which was strongly dampened as carbohydrates were transported down the trunk. Periodicity reappeared in the δ13C of trunk-respired CO2, which seemed to originate from apparent respiratory fractionation rather than from changes in δ13C of the organic substrate. The diel patterns of δ13C in soil-respired CO2 are partly explained by soil temperature and moisture and are probably due to changes in the relative contribution of heterotrophic and autotrophic CO2 fluxes to total soil efflux in response to environmental conditions. Our study shows that direct relations between δ13C of recent assimilates and respired CO2 may not be present on a diel time scale, and other factors lead to short-term variations in δ13C of ecosystem-emitted CO2. On the one hand, these variations complicate ecosystem CO2 flux partitioning, but on the other hand they provide new insights into metabolic processes underlying respiratory CO2 emission.
Significant gaps still exist in our knowledge about post-photosynthetic leaf level and downstream... more Significant gaps still exist in our knowledge about post-photosynthetic leaf level and downstream metabolic processes and iso -
topic fractionations. This includes their impact on the isotopic climate signal stored in the carbon isotope composition (δ 13 C) of
leaf assimilates and tree rings. For the first time, we compared the seasonal δ 13 C variability of leaf sucrose with intra-annual,
high-resolution δ 13 C signature of tree rings from larch (Larix gmelinii Rupr.). The trees were growing at two sites in the continuous
permafrost zone of Siberia with different growth conditions. Our results indicate very similar low-frequency intra-seasonal trends
of the sucrose and tree ring δ 13 C records with little or no indication for the use of ‘old’ photosynthates formed during the previ-
ous year(s). The comparison of leaf sucrose δ 13 C values with that in other leaf sugars and in tree rings elucidates the cause for
the reported 13 C-enrichment of sink organs compared with leaves. We observed that while the average δ 13 C of all needle sugars
was 1.2‰ more negative than δ 13 C value of wood, the δ 13 C value of the transport sugar sucrose was on an average 1.0‰ more
positive than that of wood. Our study shows a high potential of the combined use of compound-specific isotope analysis of
sugars (leaf and phloem) with intra-annual tree ring δ 13 C measurements for deepening our understanding about the mechanisms
controlling the isotope variability in tree rings under different environmental conditions.
Isotopes in environmental and health studies, 2015
Many physical and chemical processes in living systems are accompanied by isotope fractionation o... more Many physical and chemical processes in living systems are accompanied by isotope fractionation on H, C, N, O and S. Although kinetic or thermodynamic isotope effects are always the basis, their in vivo manifestation is often modulated by secondary influences. These include metabolic branching events or metabolite channeling, metabolite pool sizes, reaction mechanisms, anatomical properties and compartmentation of plants and animals, and climatological or environmental conditions. In the present contribution, the fundamentals of isotope effects and their manifestation under in vivo conditions are outlined. The knowledge about and the understanding of these interferences provide a potent tool for the reconstruction of physiological events in plants and animals, their geographical origin, the history of bulk biomass and the biosynthesis of defined representatives. It allows the use of isotope characteristics of biomass for the elucidation of biochemical pathways and reaction mechanism...
The Journal of experimental biology, 2010
Digestion, absorption and assimilation of the meal are active processes that require start-up ene... more Digestion, absorption and assimilation of the meal are active processes that require start-up energy before the energy contained in a meal can be utilized. The energetic costs associated with feeding (specific dynamic action, SDA) are high in sit-and-wait foraging snakes that tolerate long fasting periods. We used (13)C-labelled prey to partition between endogenous energy sources (i.e. snakes' own resources) and exogenous energy sources (i.e. prey). A linear mixing model was then applied to determine the portion of (13)C originating from the different sources. The snakes showed a normal and typical postprandial response. By four hours after feeding, the delta(13)C-values indicated fuel switching from endogenous to exogenous. From then on, fuel mixing continuously increased until, at 20 h after feeding, 75% of fuel was exogenous. Resource partitioning showed that throughout SDA, the amount of exogenous energy increased to approximately 60% of SDA, which was equivalent to approxim...
Phytochemistry, 2002
The bulk 15 N-value of plant (leaf) biomass is determined by that of the inorganic primary nitrog... more The bulk 15 N-value of plant (leaf) biomass is determined by that of the inorganic primary nitrogen sources NO 3 À , NH 4 + and N 2 , and by isotope discriminations on their uptake or assimilation. NH 4 + from these is transferred into ''organic N'' mainly by the glutamine synthetase reaction. The involved kinetic nitrogen isotope effect does not become manifest, because the turnover is quantitative. From the product glutamine any further conversion proceeds in a ''closed system'', where kinetic isotope effects become only efficient in connection with metabolic branching. The central and most important corresponding process is the GOGAT-reaction, involved in the de novo nitrogen binding and in recycling processes like the phenylpropanoid biosynthesis and photorespiration. The reaction yields relatively 15 N-depleted glutamate and remaining glutamine, source of 15 N-enriched amide-N in heteroaromatic compounds. Glutamate provides nitrogen for all amino acids and some other compounds with different 15 Nabundances. An isotope equilibration is not connected to transamination; the relative 15 N-value of individual amino acids is determined by their metabolic tasks. Relative to the bulk 15 N-value of the plant cell, proteins are generally 15 N-enriched, secondary products like chlorophyll, lipids, amino sugars and alkaloids are depleted in 15 N. Global 15 N-values and 15 N-patterns of compounds with several N-atoms can be calculated from those of their precursors and isotope discriminations in their biosyntheses.
Phytochemistry Reviews, 2000
The relative global
2
H-content of natural plant products is correlated to that of the primary hy... more The relative global
2
H-content of natural plant products is correlated to that of the primary hydrogen source, i.e.
water, to the site of their biosynthesis (C3-, C4- and CAM-plants; chloroplasts, cytosol), and to their biosynthetic
pathways. A relative global
2
H-content sequence can be established in the order phenylpropanoids> carbohydrates
> bulk material > hydrolysable lipids > steroids. A detailed analysis of the
2
H-patterns of the main groups of
secondary compounds reveals regularities, in that they are correlated to the primary precursors and to the origin of
hydrogen from four main pools with the mean δ
2
H-values [ ]V − SMOW: leaf H2O ∼+ 30; carbohydrates ∼− 70;
NADPH ∼− 250; flavoproteins ∼− 350. Aside from the
2
H-discrimination between these pools, kinetic isotope
effects on defined reactions only become effective in connection with metabolic branching events. So, the
2
H-
pattern of natural aromatic compounds can be correlated to the
2
H-pattern of the precursor carbohydrates and a
reduction step in the course of the shikimic acid pathway, furthermore to the implication of the NIH-shift. The
pattern of aromatic compounds from the polyketide is different from that of the shikimate pathway. The alternating
2
H-abundance of fatty acid chains is caused by the origin of their hydrogen atoms from carbohydrates and from
NADPH, directly or via a flavoprotein, respectively. This is similar for isoprenoids, and the natural
2
H-patterns
permit their assignment to the mevalonate or non-mevalonate biosynthetic pathway. Generally, the correlations
and regularities of the
2
H-patterns of organic compounds found are a new reliable tool for the elucidation of
biosynthetic pathways and origin assignments.
Phytochemistry, 2004
The biosynthetic pathway of gallic acid in leaves of Rhus typhina is studied by oxygen isotope ra... more The biosynthetic pathway of gallic acid in leaves of Rhus typhina is studied by oxygen isotope ratio mass spectrometry at natural oxygen isotope abundance. The observed delta18O-values of gallic acid indicate an 18O-enrichment of the phenolic oxygen atoms of more than 30 per thousand above that of the leaf water. This enrichment implies biogenetical equivalence with oxygen atoms of carbohydrates but not with oxygen atoms introduced by monooxygenase activation of molecular oxygen. It can be concluded that all phenolic oxygen atoms of gallic acid are retained from the carbohydrate-derived precursor 5-dehydroshikimate. This supports that gallic acid is synthesized entirely or predominantly by dehydrogenation of 5-dehydroshikimate.
Journal of Agricultural and Food Chemistry, 2011
The δ(18)O value of the p-hydroxy group of L-tyrosine depends on the biosynthesis by plants or an... more The δ(18)O value of the p-hydroxy group of L-tyrosine depends on the biosynthesis by plants or animals, respectively. In animal proteins it reflects the diet and is therefore an absolute indicator for illegal feeding with meat and bone meal. The aim of this investigation was to perform the positional (18)O determination on L-tyrosine via a one-step enzymatic degradation. Proteins from plants, herbivores, omnivores, and carnivores were characterized by their δ(13)C, δ(15)N, and δ(18)O values, the latter for normalizing the positional δ(18)O values. Their L-tyrosine was degraded by tyrosine phenol lyase to phenol, analyzed as (2,4,6)-tribromophenol. Degradation by tyrosine decarboxylase yielded tyramine. The δ(18)O values of both analytes corresponded to the trophic levels of their sources but were not identical, probably due to an isotope effect on the tyrosine phenol lyase reaction. Availability of the enzyme, easy control of the reaction, and isolation of the analyte are in favor of tyrosine decarboxylase degradation as a routine method.
Isotopes in Environmental and Health Studies, 2003
Oxygen is a globally important element, in inorganic compounds it is involved in key structural c... more Oxygen is a globally important element, in inorganic compounds it is involved in key structural compounds of the earth, and it is providing functional groups for most organic compounds. Oxygen isotope ratio analyses on these compounds provide information on the oxygen sources and (formation) reactions in which the compound was involved. Therefore generally applicable analytical methods for the delta18O determination are highly desirable. After a description of online high temperature "carbon reduction" methods for the conversion of oxygen in the compounds mentioned into CO and discussion of problems involved, especially in analysis of inorganic substances like carbonates and silicates, selected examples for the application of these carbon reduction methods will be presented. The well-known correlation of delta18O values of cellulose (in tree rings) to that of (leaf) water is used since the 1970's as climate indicator. The observed enrichment in 18O in cellulose by about 27% in comparison to leaf water is attributed to an oxygen equilibrium isotope effect between carbonyl groups and water. But not all carbohydrates show this "general"18O enrichment relative to water. By means of a recently published model a non-statistical oxygen isotope distribution in carbohydrates is postulated. Oxygen isotope discrimination has been recognized long ago as an important principle of authenticity evaluation in food and beverages. Though many basic mechanisms of isotope discrimination in nature are known, the corresponding application of data is often based only on empirical observations in this field. The fact that oxygen in natural organic plant material is derived from three sources (CO2, H2O, O2) with distinct differences in and that their incorporation by different reactions implies oxygen isotope effects of different sizes, is therefore of special importance, and it is attempted by means of individual isotopic increments of functional groups to predict global delta18O values of natural and nature-identical compounds. Vice versa delta18O values can also give hints on the elucidation of biosynthetic pathways.
Analytica Chimica Acta
A new method for the automated sample preparation and on-line isotope ratio determination of S"O ... more A new method for the automated sample preparation and on-line isotope ratio determination of S"O values of organic compounds is presented. The principle of the production of CO as measuring gas is a sudden pyrolysis in a helium carrier stream at a temperature of 1080°C in the absence of surplus carbon. Results obtained with this method for carbohydrates and some aromatic substances show a very satisfactory agreement with St80 values obtained by the Rittenberg-Ponticorvo method and with known 6 "0 values of standards; the standard deviation observed is usually better than 0.8%. The method is in principle also suitable for nitrogen containing compounds, as it implies a gas chromatographic separation of CO and N,. Long-chained aliphatic alcohols, aldehydes, esters, and some nitrogen containing compounds did not give satisfactory results, probably because of an insufficient CO yield.
The application of 13 C/ 12 C in ecosystem-scale tracer models for CO 2 in air requires accurate ... more The application of 13 C/ 12 C in ecosystem-scale tracer models for CO 2 in air requires accurate mea-10 surements of mixing ratios and stable isotope ratios of CO 2 . To increase measurement reliability and 11 data intercomparability as well as to shorten analysis times, we have improved an existing field sampling 12 setup with portable air sampling units and developed a laboratory setup for analysis of δ 13 C of CO 2 in 13 air by isotope ratio mass spectrometry (IRMS). The changes consist of (a) optimization of sample and 14 standard gas flow paths, (b) additional software configuration and (c) automation of liquid nitrogen refill-15 ing for the cryogenic trap. We achieved a precision better than 0.1 and an accuracy of 0.11±0.04 16 for δ 13 C of CO 2 in air and unattended operation of measurement sequences up to 12 hours. 17 18 The interest in the global atmospheric car-19 bon cycle has intensified as a response to re-20 ported trends in global climate change. These 21 trends are primarily related to atmospheric in-22 creases in greenhouse gas concentrations. 1 On 23 the global average, carbon dioxide (CO 2 ) plays 24 the most important role and thus ecosystem ori-25 ented research has particularly focused on CO 2 . 26 The potential use of the stable isotope ratios of 27 CO 2 (e.g. 13 C/ 12 C, 18 O/ 16 O) in ecosystem-scale 28 atmosphere-biosphere process studies has often 29 been highlighted and is believed to be a power-30 ful tool for carbon cycle studies, in particular to 31 disentangle ecosystem flux components. e.g. 2-7 It is 32 commonly used to quantify mixing contributions 33 from sources with differing isotopic composi-34 tions. 8,9 However, this requires accurate measure-35 ments of both CO 2 mixing ratios and isotopic com-36 position in order to be useable in ecosystem-scale 37 tracer model approaches. 4,10,11 On local (species 38 to ecosystem) scales this can be quite a challenge; 39 CO 2 mixing ratios and isotopic composition in the 40 air close to the vegetation are known to fluctu-41 ate strongly, i.e. on short time scales (seconds to 42 hours), especially under less turbulent atmospheric 43 conditions due to accumulation of CO 2 . Moreover, 44 with conventional flask sampling the measurement 45 strategy is mostly limited to discrete sampling, and 46 typically these samples need to be transferred to a 47 distant laboratory for analysis by an Isotope Ratio 48 Mass Spectrometer, so the insight into ecosystem 49 processes is hampered by technical and logistical 50 constraints. 51 In this paper, we aim to optimize and ex-52 tensively test air sampling and analysis of stable 53 carbon and oxygen isotope ratios in atmospheric 54 CO 2 for stable isotope studies at the ecosystem 55 level. The setup described here has been suc-56 cessfully used for grassland ecosystem studies in 57 Switzerland and intercomparisons of stable iso-58 tope ratio instrumentation (e.g. a comparison of 59 a quantum cascade laser based absorption spec-60 trometer, a field-deployable Fourier transform in-61 frared spectrometer and an Isotope Ratio Mass 62 Spectrometer). e.g. 12-14 The basic considerations 63 for the chosen measurement approach haves been 64 (a) the collection of samples at multiple locations 65 for (b) sample measurements by laboratory based 66 high precision Isotope Ratio Mass Spectrometer. 67 The most important implication of this approach 68 is that the conditions (e.g. temperature, pres-69 sure) might be different between location of sam-70 ple collection and the laboratory. Thus, gas sam-71 ples might be contaminated during the storage pe-72 riod between sampling and analysis, which is es-73 pecially likely if samples are collected at higher 74 altitudes under reduced ambient pressure. 15-18 For 157 changed the original Theis et al. 19 design and the 158 position of the Teflon membrane pump (N811K-159
A method for isotope ratio analysis of water samples is described comprising an on-line high-temp... more A method for isotope ratio analysis of water samples is described comprising an on-line high-temperature reduction technique in a helium carrier gas. Using a gas-tight syringe, injection of 0.5 to 1 mL sample is made through a heated septum into a glassy carbon reactor at temperatures in excess of 13008C. More than 150 injections can be made per day and both isotope ratios of interest, d 2 H and d 18 O, can be measured with the same setup. The technique has the capability to transfer high-precision stable isotope ratio analysis of water samples from a specialized to a routine laboratory task compatible with other common techniques (automated injection for GC, LC, etc.). Experiments with an emphasis on the reactor design were made in two different laboratories using two different commercially available high-temperature elemental analyser (EA) systems.
Three research sites on elevations covering the relevant stages of the Swiss agricultural system ... more Three research sites on elevations covering the relevant stages of the Swiss agricultural system (400, 1000, and 2000 m a.s.l.) have been established. This allows for in-situ investigation of the processes involved in green-house gas exchanges of grassland. A first assessment of stable carbon dioxide isotope analysis has provided valuable information on CO2 flux partitioning. For the first time a comparison of three independent measurement techniques for stable isotope ratios (13C/12C) and (18O/16O) and green-house gas concentrations of carbon dioxide, methane and nitrous oxide was performed. During a three week period, air samples were collected at four height profiles (z = 0.055; 0.14; 0.40; 1.90 m) and in a regular two hours interval by automated air samplers connected to a switching inlet system. The isotopic ratios (13C/12C) and (18O/16O) of carbon dioxide were measured in the laboratory with Isotope Ratio Mass Spectrometry (IRMS). Simultaneously, two additional optical techniq...
To improve our understanding of greenhouse gas dynamics of managed ecosystems such as grasslands,... more To improve our understanding of greenhouse gas dynamics of managed ecosystems such as grasslands, we not only need to investigate the effects of management (e.g., grass cuts) and weather events (e.g., rainy days) on carbon dioxide fluxes, but also need to increase the time resolution of our measurements. Thus, for the first time, we assessed respiration and assimilation fluxes with high time resolution (5Hz) stable isotope measurements at an intensively managed farmland in Switzerland (Chamau, 400m ASL). Two different methods were used to quantify fluxes of carbon dioxide and associated fluxes of stable carbon isotopes: (1) the flux gradient method, and (2) the eddy covariance method. During a week long intensive measurement campaign, we (1) measured mixing ratios of carbon dioxide isotopomers (12C16O2, 12C16O18O, 13C16O2) with a Quantum Cascade Laser (QCL, Aerodyne Inc.) spectroscope and (2) collected air samples for isotope analyses (13C/12C) and (18O/16O) of carbon dioxide by Iso...
The biosynthesis of L-tyrosine in plants by the shikimate pathway via arogenate implies that the ... more The biosynthesis of L-tyrosine in plants by the shikimate pathway via arogenate implies that the oxygen atom in the p-position originates from D-erythrose with a δ 18 O-value near +30‰ above leaf water, while its synthesis in animals by hydroxylation of external L-phenylalanine with O 2 as oxygen source and a kinetic isotope effect k 16 /k 18 ≅1.018 demands a δ 18 O-value near +6‰. These expectations are fully confirmed by experimental data from the 18 O-pattern analysis of natural aromatic compounds. The result is considered as a basis for the assignment of L-tyrosine and L-tyrosine-derived material of plant or animal origin, respectively, and for the determination of the relative amounts of plant and animal material in food and animal feed.
Aiming at developing a novel tool for palaeoclimate research, we recently proposed a new method f... more Aiming at developing a novel tool for palaeoclimate research, we recently proposed a new method for determining the oxygen isotope composition of monosaccharides . Compound-specific d 18 O analyses of neutral sugars in soils using GC-Py-IRMS: problems, possible solutions and a first application. Rapid Communications in Mass Spectrometry 23, 3522-3532). In order to answer the question whether isotope fractionation and oxygen exchange reactions during litter decomposition affect the climatically controlled d 18 O values of plant derived sugars, such as for instance xylose and arabinose from hemicelluloses, we studied the compound specific d 18 O values of five different litter species having been decomposed in a field litterbag experiment for 27 months.
Journal of experimental botany, Jan 2, 2015
Dissimilation of carbon sources during plant respiration in support of metabolic processes result... more Dissimilation of carbon sources during plant respiration in support of metabolic processes results in the continuous release of CO2. The carbon isotopic composition of leaf dark-respired CO2 (i.e. δ (13) C R ) shows daily enrichments up to 14.8‰ under different environmental conditions. However, the reasons for this (13)C enrichment in leaf dark-respired CO2 are not fully understood, since daily changes in δ(13)C of putative leaf respiratory carbon sources (δ (13) C RS ) are not yet clear. Thus, we exposed potato plants (Solanum tuberosum) to different temperature and soil moisture treatments. We determined δ (13) C R with an in-tube incubation technique and δ (13) C RS with compound-specific isotope analysis during a daily cycle. The highest δ (13) C RS values were found in the organic acid malate under different environmental conditions, showing less negative values compared to δ (13) C R (up to 5.2‰) and compared to δ (13) C RS of soluble carbohydrates, citrate and starch (up to ...
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Papers by Roland A Werner
topic fractionations. This includes their impact on the isotopic climate signal stored in the carbon isotope composition (δ 13 C) of
leaf assimilates and tree rings. For the first time, we compared the seasonal δ 13 C variability of leaf sucrose with intra-annual,
high-resolution δ 13 C signature of tree rings from larch (Larix gmelinii Rupr.). The trees were growing at two sites in the continuous
permafrost zone of Siberia with different growth conditions. Our results indicate very similar low-frequency intra-seasonal trends
of the sucrose and tree ring δ 13 C records with little or no indication for the use of ‘old’ photosynthates formed during the previ-
ous year(s). The comparison of leaf sucrose δ 13 C values with that in other leaf sugars and in tree rings elucidates the cause for
the reported 13 C-enrichment of sink organs compared with leaves. We observed that while the average δ 13 C of all needle sugars
was 1.2‰ more negative than δ 13 C value of wood, the δ 13 C value of the transport sugar sucrose was on an average 1.0‰ more
positive than that of wood. Our study shows a high potential of the combined use of compound-specific isotope analysis of
sugars (leaf and phloem) with intra-annual tree ring δ 13 C measurements for deepening our understanding about the mechanisms
controlling the isotope variability in tree rings under different environmental conditions.
2
H-content of natural plant products is correlated to that of the primary hydrogen source, i.e.
water, to the site of their biosynthesis (C3-, C4- and CAM-plants; chloroplasts, cytosol), and to their biosynthetic
pathways. A relative global
2
H-content sequence can be established in the order phenylpropanoids> carbohydrates
> bulk material > hydrolysable lipids > steroids. A detailed analysis of the
2
H-patterns of the main groups of
secondary compounds reveals regularities, in that they are correlated to the primary precursors and to the origin of
hydrogen from four main pools with the mean δ
2
H-values [ ]V − SMOW: leaf H2O ∼+ 30; carbohydrates ∼− 70;
NADPH ∼− 250; flavoproteins ∼− 350. Aside from the
2
H-discrimination between these pools, kinetic isotope
effects on defined reactions only become effective in connection with metabolic branching events. So, the
2
H-
pattern of natural aromatic compounds can be correlated to the
2
H-pattern of the precursor carbohydrates and a
reduction step in the course of the shikimic acid pathway, furthermore to the implication of the NIH-shift. The
pattern of aromatic compounds from the polyketide is different from that of the shikimate pathway. The alternating
2
H-abundance of fatty acid chains is caused by the origin of their hydrogen atoms from carbohydrates and from
NADPH, directly or via a flavoprotein, respectively. This is similar for isoprenoids, and the natural
2
H-patterns
permit their assignment to the mevalonate or non-mevalonate biosynthetic pathway. Generally, the correlations
and regularities of the
2
H-patterns of organic compounds found are a new reliable tool for the elucidation of
biosynthetic pathways and origin assignments.
topic fractionations. This includes their impact on the isotopic climate signal stored in the carbon isotope composition (δ 13 C) of
leaf assimilates and tree rings. For the first time, we compared the seasonal δ 13 C variability of leaf sucrose with intra-annual,
high-resolution δ 13 C signature of tree rings from larch (Larix gmelinii Rupr.). The trees were growing at two sites in the continuous
permafrost zone of Siberia with different growth conditions. Our results indicate very similar low-frequency intra-seasonal trends
of the sucrose and tree ring δ 13 C records with little or no indication for the use of ‘old’ photosynthates formed during the previ-
ous year(s). The comparison of leaf sucrose δ 13 C values with that in other leaf sugars and in tree rings elucidates the cause for
the reported 13 C-enrichment of sink organs compared with leaves. We observed that while the average δ 13 C of all needle sugars
was 1.2‰ more negative than δ 13 C value of wood, the δ 13 C value of the transport sugar sucrose was on an average 1.0‰ more
positive than that of wood. Our study shows a high potential of the combined use of compound-specific isotope analysis of
sugars (leaf and phloem) with intra-annual tree ring δ 13 C measurements for deepening our understanding about the mechanisms
controlling the isotope variability in tree rings under different environmental conditions.
2
H-content of natural plant products is correlated to that of the primary hydrogen source, i.e.
water, to the site of their biosynthesis (C3-, C4- and CAM-plants; chloroplasts, cytosol), and to their biosynthetic
pathways. A relative global
2
H-content sequence can be established in the order phenylpropanoids> carbohydrates
> bulk material > hydrolysable lipids > steroids. A detailed analysis of the
2
H-patterns of the main groups of
secondary compounds reveals regularities, in that they are correlated to the primary precursors and to the origin of
hydrogen from four main pools with the mean δ
2
H-values [ ]V − SMOW: leaf H2O ∼+ 30; carbohydrates ∼− 70;
NADPH ∼− 250; flavoproteins ∼− 350. Aside from the
2
H-discrimination between these pools, kinetic isotope
effects on defined reactions only become effective in connection with metabolic branching events. So, the
2
H-
pattern of natural aromatic compounds can be correlated to the
2
H-pattern of the precursor carbohydrates and a
reduction step in the course of the shikimic acid pathway, furthermore to the implication of the NIH-shift. The
pattern of aromatic compounds from the polyketide is different from that of the shikimate pathway. The alternating
2
H-abundance of fatty acid chains is caused by the origin of their hydrogen atoms from carbohydrates and from
NADPH, directly or via a flavoprotein, respectively. This is similar for isoprenoids, and the natural
2
H-patterns
permit their assignment to the mevalonate or non-mevalonate biosynthetic pathway. Generally, the correlations
and regularities of the
2
H-patterns of organic compounds found are a new reliable tool for the elucidation of
biosynthetic pathways and origin assignments.