scholarly journals Why are non-photosynthetic tissues generally 13C enriched compared with leaves in C3 plants? Review and synthesis of current hypotheses

2009 ◽  
Vol 36 (3) ◽  
pp. 199 ◽  
Author(s):  
Lucas A. Cernusak ◽  
Guillaume Tcherkez ◽  
Claudia Keitel ◽  
William K. Cornwell ◽  
Louis S. Santiago ◽  
...  
Keyword(s):  
Carbon Fixation ◽  
Dark Respiration ◽  
Isotope Composition ◽  
General Pattern ◽  
Isotopic Fractionation ◽  
C3 Plants ◽  
Future Research ◽  
Plant Variation ◽  
Developmental Variation ◽  
Isotopic Pattern

Non-photosynthetic, or heterotrophic, tissues in C3 plants tend to be enriched in 13C compared with the leaves that supply them with photosynthate. This isotopic pattern has been observed for woody stems, roots, seeds and fruits, emerging leaves, and parasitic plants incapable of net CO2 fixation. Unlike in C3 plants, roots of herbaceous C4 plants are generally not 13C-enriched compared with leaves. We review six hypotheses aimed at explaining this isotopic pattern in C3 plants: (1) variation in biochemical composition of heterotrophic tissues compared with leaves; (2) seasonal separation of growth of leaves and heterotrophic tissues, with corresponding variation in photosynthetic discrimination against 13C; (3) differential use of day v. night sucrose between leaves and sink tissues, with day sucrose being relatively 13C-depleted and night sucrose 13C-enriched; (4) isotopic fractionation during dark respiration; (5) carbon fixation by PEP carboxylase; and (6) developmental variation in photosynthetic discrimination against 13C during leaf expansion. Although hypotheses (1) and (2) may contribute to the general pattern, they cannot explain all observations. Some evidence exists in support of hypotheses (3) through to (6), although for hypothesis (6) it is largely circumstantial. Hypothesis (3) provides a promising avenue for future research. Direct tests of these hypotheses should be carried out to provide insight into the mechanisms causing within-plant variation in carbon isotope composition.

Stable carbon isotope analysis of faecal and blood samples of sheep in relation to the diet

2003 ◽  
Vol 2003 ◽  
pp. 159-159
Author(s):  
A. Balcaen ◽  
E. Claeys ◽  
V. Fievez ◽  
P. Boeckx ◽  
O. van Cleemput ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Carbon Isotope ◽  
Carbon Fixation ◽  
Isotope Composition ◽  
Stable Carbon Isotope ◽  
Isotope Analysis ◽  
Calvin Cycle ◽  
Isotopic Fractionation ◽  
Woody Species ◽  
Stable Carbon

Stable isotopes have been extraordinarily helpful in understanding animal migration, diet, food webs and nutrient flow (Hilderbrand et al., 1996), based on the property that C3 and C4 plants possess distinctly different 13C/12C ratios (δ13C value) due to isotopic fractionation during photosynthetic carbon fixation (Smith & Epstein, 1971). Most woody species and temperate graminoids assimilate carbon via the Calvin cycle (C3), which discriminates stronger against the heavier isotope (13C) than Hatch-Slack (C4) species (tropical and subtropical graminoids and some shrubs). C3 and C4 plant species have mean δ13C values of -27 ‰ and -13 ‰ respectively (O’Leary, 1981). DeNiro & Epstein (1978) were one of the first to show that the isotopic composition of the whole animal body is similar to that of its diet. Other authors have also found relationships between the isotopic composition of animal tissues and the diet (González-Martin et al., 1999; Jones et al., 1979). The aim of this study was to investigate stable carbon isotope composition in sheep fed diets consisting of either C3 or C3+C4 plants.

Dynamic carbon allocation into source and sink tissues determine within-plant differences in carbon isotope ratios

2015 ◽  
Vol 42 (7) ◽  
pp. 620 ◽  
Author(s):  
Frederik Wegener ◽  
Wolfram Beyschlag ◽  
Christiane Werner
Keyword(s):  
Nutrient Availability ◽  
Carbon Allocation ◽  
Plant Biomass ◽  
Dark Respiration ◽  
Isotope Composition ◽  
Isotopic Signature ◽  
C3 Plants ◽  
Whole Plant ◽  
Morphological And Physiological Traits ◽  
Allocation Strategies

Organs of C3 plants differ in their C isotopic signature (δ13C). In general, leaves are 13C-depleted relative to other organs. To investigate the development of spatial δ13C patterns, we induced different C allocation strategies by reducing light and nutrient availability for 12 months in the Mediterranean shrub Halimium halimifolium L. We measured morphological and physiological traits and the spatial δ13C variation among seven tissue classes during the experiment. A reduction of light (Low-L treatment) increased aboveground C allocation, plant height and specific leaf area. Reduced nutrient availability (Low-N treatment) enhanced C allocation into fine roots and reduced the spatial δ13C variation. In contrast, control and Low-L plants with high C allocation in new leaves showed a high δ13C variation within the plant (up to 2.5‰). The spatial δ13C variation was significantly correlated with the proportion of second-generation leaves from whole-plant biomass (R2 = 0.46). According to our results, isotope fractionation in dark respiration can influence the C isotope composition of plant tissues but cannot explain the entire spatial pattern seen. Our study indicates a foliar depletion in 13C during leaf development combined with export of relatively 13C-enriched C by mature source leaves as an important reason for the observed spatial δ13C pattern.

scholarly journals Microbial Isotopic Fractionation of Perchlorate Chlorine

2003 ◽  
Vol 69 (8) ◽  
pp. 4997-5000 ◽  
Author(s):  
Max L. Coleman ◽  
Magali Ader ◽  
Swades Chaudhuri ◽  
John D. Coates
Keyword(s):  
Stable Isotope ◽  
Environmental Samples ◽  
Microbial Respiration ◽  
Isotope Composition ◽  
Isotopic Fractionation ◽  
Stable Isotope Composition ◽  
Biotic Degradation ◽  
Chlorine Stable Isotope

ABSTRACT Perchlorate contamination can be microbially respired to innocuous chloride and thus can be treated effectively. However, monitoring a bioremediative strategy is often difficult due to the complexities of environmental samples. Here we demonstrate that microbial respiration of perchlorate results in a significant fractionation (∼−15‰) of the chlorine stable isotope composition of perchlorate. This can be used to quantify the extent of biotic degradation and to separate biotic from abiotic attenuation of this contaminant.

scholarly journals Excursions to C<sub>4</sub> vegetation recorded in the Upper Pleistocene loess of Surduk (Northern Serbia): an organic isotope geochemistry study

2013 ◽  
Vol 9 (3) ◽  
pp. 1001-1014 ◽  
Author(s):  
C. Hatté ◽  
C. Gauthier ◽  
D.-D. Rousseau ◽  
P. Antoine ◽  
M. Fuchs ◽  
...  
Keyword(s):  
General Pattern ◽  
Free Water ◽  
Circulation Pattern ◽  
Water Evaporation ◽  
C3 Plants ◽  
Mean Annual Precipitation ◽  
Glacial Cycle ◽  
Last Interglacial ◽  
The Balkans ◽  
The Mediterranean

Abstract. Loess sequences have been intensively studied to characterize past glacial climates of the 40–50° north and south latitude zones. Combining different approaches of sedimentology, magnetism, geochemistry, geochronology and malacology allows the general pattern of the climate and environment of the last interglacial–glacial cycle in Eurasia and America to be characterized. Previous studies performed in Europe have highlighted the predominance (if not the sole occurrence) of C3 vegetation. The presence of C3 plants suggests a regular distribution of precipitation along the year. Therefore, even if the mean annual precipitation remained very low during the most extensive glacial times, free water was available for more than 2 months per year. Contrarily, the δ13C record of Surduk (Serbia) clearly shows the occurrence and dominance of C4 plants during at least 4 episodes of the last glacial times at 28.0–26.0 kyr cal BP, 31.4–30.0 kyr cal BP, 53.4–44.5 kyr cal BP and 86.8–66.1 kyr. The C4 plant development is interpreted as a specific atmospheric circulation pattern that induces short and dry summer conditions. As possible explanation, we propose that during "C4 episodes", the Mediterranean Sea would have been under the combined influence of the following: (i) a strong meridional circulation unfavorable to water evaporation that reduced the Mediterranean precipitation on the Balkans; and (ii) a high positive North Atlantic Western Russian (NA/WR)-like atmospheric pattern that favored northerlies over westerlies and reduced Atlantic precipitation over the Balkans. This configuration would imply very dry summers that did not allow C3 plants to grow, thus supporting C4 development. The intra-"C4 episode" periods would have occurred under less drastic oceanic and atmospheric patterns that made the influence of westerlies on the Balkans possible.

scholarly journals Ecosystem effects of CO<sub>2</sub> concentration: evidence from past climates

2009 ◽  
Vol 5 (2) ◽  
pp. 937-963 ◽  
Author(s):  
I. C. Prentice ◽  
S. P. Harrison
Keyword(s):  
Forest Cover ◽  
Dissolved Inorganic Carbon ◽  
Net Primary Production ◽  
Isotope Composition ◽  
Late Quaternary ◽  
Co2 Concentration ◽  
C3 Plants ◽  
Sea Level Changes ◽  
Co2 Effects ◽  
Concentration Changes

Abstract. Atmospheric CO2 concentration has varied from minima of 170–200 ppm in glacials to maxima of 280–300 ppm in the recent interglacials. Photosynthesis by C3 plants is highly sensitive to CO2 concentration variations in this range. Physiological consequences of the CO2 changes should therefore be discernible in palaeodata. Several lines of evidence support this expectation. Reduced terrestrial carbon storage during glacials, indicated by the shift in stable isotope composition of dissolved inorganic carbon in the ocean, cannot be explained by climate or sea-level changes. It is however consistent with predictions of current process-based models that propagate known physiological CO2 effects into net primary production at the ecosystem scale. Restricted forest cover during glacial periods, indicated by pollen assemblages dominated by non-arboreal taxa, cannot be reproduced accurately by palaeoclimate models unless CO2 effects on C3-C4 plant competition are also modelled. It follows that methods to reconstruct climate from palaeodata should account for CO2 concentration changes. When they do so, they yield results more consistent with palaeoclimate models. In conclusion, the palaeorecord of the Late Quaternary, interpreted with the help of climate and ecosystem models, provides evidence that CO2 effects at the ecosystem scale are neither trivial nor transient.

Measurements of leaf sucrose to explain variability in hydrogen isotope composition of leaf cellulose

2021 ◽  
Author(s):  
Meisha Holloway-Philips ◽  
Jochem Baan ◽  
Daniel Nelson ◽  
Guillaume Tcherkez ◽  
Ansgar Kahmen
Keyword(s):  
Hydrogen Isotope ◽  
Metabolic Flux ◽  
Species Differences ◽  
Dark Respiration ◽  
Isotope Composition ◽  
Turnover Time ◽  
Water Soluble ◽  
Soluble Carbohydrates ◽  
Model Parameters ◽  
Hydrogen Isotope Composition

&lt;p&gt;The hydrogen isotope composition (&amp;#948;&lt;sup&gt;2&lt;/sup&gt;H) of cellulose has been used to assess ecohydrological processes and carries metabolic information, adding new understanding to how plants respond to environmental change. However, experimental approaches to isolate drivers of &amp;#948;&lt;sup&gt;2&lt;/sup&gt;H variation is limited to the Yakir &amp; DeNiro model (1990), which is difficult to implement and largely unvalidated. Notably, the two biosynthetic fractionation factors in the model, associated with photosynthetic (&amp;#949;&lt;sub&gt;A&lt;/sub&gt;) and post-photosynthetic (&amp;#949;&lt;sub&gt;H&lt;/sub&gt;) processes are currently accepted as constants, and the third parameter &amp;#8211; the extent to which organic molecules exchange hydrogen (f&lt;sub&gt;H&lt;/sub&gt;) with local water &amp;#8211; is usually tuned in order to resolve the difference between modelled and observed cellulose &amp;#948;&lt;sup&gt;2&lt;/sup&gt;H values. Thus, by virtue, the metabolically interpretable parameter is only f&lt;sub&gt;H&lt;/sub&gt;, whilst from theory, metabolic flux rates will also impact on the apparent fractionations. To overcome part of this limitation, we measured the &amp;#948;&lt;sup&gt;2&lt;/sup&gt;H of extracted leaf sucrose from fully-expanded leaves of seven species and a phosphoglucomutase &amp;#8216;starchless&amp;#8217; mutant of tobacco to estimate the isotopic offset between sucrose and leaf water (&amp;#949;&lt;sub&gt;sucrose&lt;/sub&gt;). Sucrose &amp;#948;&lt;sup&gt;2&lt;/sup&gt;H explained ~60% of the &amp;#948;&lt;sup&gt;2&lt;/sup&gt;H variation observed in cellulose. In general, &amp;#949;&lt;sub&gt;sucrose&lt;/sub&gt;&amp;#160;was higher (range: -203&amp;#8240; to -114&amp;#8240;; mean: -151 &amp;#177; 21&amp;#8240;) than the currently accepted value of -171&amp;#8240; (&amp;#949;&lt;sub&gt;A&lt;/sub&gt;) reflecting &lt;sup&gt;2&lt;/sup&gt;H-enrichment downstream of triose-phosphate export from the chloroplast, with statistical differences in &amp;#949;&lt;sub&gt;sucrose&lt;/sub&gt;&amp;#160;observed between species estimates. The remaining &amp;#948;&lt;sup&gt;2&lt;/sup&gt;H variation in cellulose was explained by species differences in f&lt;sub&gt;H&amp;#160;&lt;/sub&gt;(estimated by assuming &amp;#949;&lt;sub&gt;H &lt;/sub&gt;= +158&amp;#8240;). We also tested possible links between model parameters and plant metabolism. &amp;#949;&lt;sub&gt;sucrose&lt;/sub&gt;&amp;#160;was positively related to dark respiration (R&lt;sup&gt;2&lt;/sup&gt;=0.27) suggesting an important branch point influencing sugar &amp;#948;&lt;sup&gt;2&lt;/sup&gt;H. In addition, f&lt;sub&gt;H&lt;/sub&gt; was positively related to the turnover time (&amp;#964;) of water-soluble carbohydrates (R&lt;sup&gt;2&lt;/sup&gt;=0.38), but only when estimated using fixed &amp;#949;&lt;sub&gt;A &lt;/sub&gt;= -171&amp;#8240;. To decipher and isolate the &amp;#8220;metabolic&amp;#8221; information contained within &amp;#948;&lt;sup&gt;2&lt;/sup&gt;H values of cellulose it will be important to assess &amp;#948;&lt;sup&gt;2&lt;/sup&gt;H values of non-structural carbohydrates so that hydrogen isotope fractionation during sugar metabolism can be better understood. This study provides the first attempt at such measurements showing species differences in both source and sink processes are important in understanding &amp;#948;&lt;sup&gt;2&lt;/sup&gt;H variation of cellulose.&lt;/p&gt;

The Schizophrenia Spectrum

2018 ◽  
pp. 208-230
Author(s):  
Marco Del Giudice
Keyword(s):  
General Pattern ◽  
Future Research ◽  
Evolutionary Models ◽  
Schizophrenia Spectrum Disorders ◽  
External Reality ◽  
Schizotypal Personality ◽  
Schizophrenia Spectrum ◽  
New Directions ◽  
Loss Of Contact ◽  
Developmental Features

The chapter discusses schizophrenia spectrum disorders (SSDs), including schizophrenia and schizotypal personality disorder (SPD). Schizophrenia and related disorders are part of the broader spectrum of psychosis, a cluster of genetically and phenotypically related conditions marked by loss of contact with external reality. After an overview of these disorders, their developmental features, and the main risk factors identified in the epidemiological literature, the chapter critically reviews existing evolutionary models and suggests new directions for research. The final section applies the criteria developed earlier in the book to classify the disorders within the fast-slow-defense (FSD) model and identify functionally distinct subtypes. The author concludes that most instances of SSDs can be classified as fast spectrum (F-type) conditions; however, there are indications of heterogeneity within these conditions, and future research is likely to identify exceptions to the general pattern.

scholarly journals Searching for signatures of life on Mars: an Fe-isotope perspective

2006 ◽  
Vol 361 (1474) ◽  
pp. 1715-1720 ◽  
Author(s):  
M Anand ◽  
S.S Russell ◽  
R.L Blackhurst ◽  
M.M Grady
Keyword(s):  
Low Temperature ◽  
Liquid Water ◽  
Isotope Composition ◽  
Isotopic Fractionation ◽  
Isotope Ratios ◽  
Experimental Investigations ◽  
Form Of Life ◽  
Geological Past ◽  
Martian Meteorites ◽  
Fe Reduction

Recent spacecraft and lander missions to Mars have reinforced previous interpretations that Mars was a wet and warm planet in the geological past. The role of liquid water in shaping many of the surface features on Mars has long been recognized. Since the presence of liquid water is essential for survival of life, conditions on early Mars might have been more favourable for the emergence and evolution of life. Until a sample return mission to Mars, one of the ways of studying the past environmental conditions on Mars is through chemical and isotopic studies of Martian meteorites. Over 35 individual meteorite samples, believed to have originated on Mars, are now available for lab-based studies. Fe is a key element that is present in both primary and secondary minerals in the Martian meteorites. Fe-isotope ratios can be fractionated by low-temperature processes which includes biological activity. Experimental investigations of Fe reduction and oxidation by bacteria have produced large fractionation in Fe-isotope ratios. Hence, it is considered likely that if there is/were any form of life present on Mars then it might be possible to detect its signature by Fe-isotope studies of Martian meteorites. In the present study, we have analysed a number of Martian meteorites for their bulk-Fe-isotope composition. In addition, a set of terrestrial analogue material has also been analysed to compare the results and draw inferences. So far, our studies have not found any measurable Fe-isotopic fractionation in bulk Martian meteorites that can be ascribed to any low-temperature process operative on Mars.

scholarly journals <sup>2</sup>H and <sup>18</sup>O depletion of water close to organic surfaces

2016 ◽  
Vol 13 (10) ◽  
pp. 3175-3186 ◽  
Author(s):  
Guo Chen ◽  
Karl Auerswald ◽  
Hans Schnyder
Keyword(s):  
Isotopic Composition ◽  
Soil Water ◽  
Filter Paper ◽  
Surface Effect ◽  
Isotope Composition ◽  
Isotopic Fractionation ◽  
Adsorbed Water ◽  
Organic Soil ◽  
Surface Areas ◽  
Isotope Composition Of Water

Abstract. Hydrophilic surfaces influence the structure of water close to them and may thus affect the isotope composition of water. Such an effect should be relevant and detectable for materials with large surface areas and low water contents. The relationship between the volumetric solid : water ratio and the isotopic fractionation between adsorbed water and unconfined water was investigated for the materials silage, hay, organic soil (litter), filter paper, cotton, casein and flour. Each of these materials was equilibrated via the gas phase with unconfined water of known isotopic composition to quantify the isotopic difference between adsorbed water and unconfined water. Across all materials, isotopic fractionation was significant (p<0.05) and negative (on average −0.91 ± 0.22 ‰ for 18∕16O and −20.6 ± 2.4 ‰ for 2∕1H at an average solid : water ratio of 0.9). The observed isotopic fractionation was not caused by solutes, volatiles or old water because the fractionation did not disappear for washed or oven-dried silage, the isotopic fractionation was also found in filter paper and cotton, and the fractionation was independent of the isotopic composition of the unconfined water. Isotopic fractionation became linearly more negative with increasing volumetric solid : water ratio and even exceeded −4 ‰ for 18∕16O and −44 ‰ for 2∕1H. This fractionation behaviour could be modelled by assuming two water layers: a thin layer that is in direct contact and influenced by the surface of the solid and a second layer of varying thickness depending on the total moisture content that is in equilibrium with the surrounding vapour. When we applied the model to soil water under grassland, the soil water extracted from 7 and 20 cm depth was significantly closer to local meteoric water than without correction for the surface effect. This study has major implications for the interpretation of the isotopic composition of water extracted from organic matter, especially when the volumetric solid : water ratio is larger than 0.5 or for processes occurring at the solid–water interface.

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