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1
Villani, F., M. Pigliucci, M. Lauteri, M. Cherubini, and O. Sun. "Congruence between genetic, morphometric, and physiological data on differentiation of Turkish chestnut (Castanea sativa)." Genome 35, no. 2 (April 1, 1992): 251–56. http://dx.doi.org/10.1139/g92-038.
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Patterns of variability of genetic, morphometric, and physiological traits in Turkish chestnut (Castanea sativa Mill.) are investigated. Previous studies suggested a marked genetic differentiation of Turkish demes, arranged in an east-west cline. Genetic distances based on 21 isozyme loci, discriminant analysis of 13 fruit traits, and analysis of variance of carbon isotope discrimination were carried out. The results agree with genetic divergence reported earlier, and reveal remarkably consistent variation patterns for the three types of biological traits. Historical and anthropogenic effects are discussed as causes of chestnut evolution after the Wurm glaciation and of chestnut dispersal in historical times. Particular attention is focused on probable selective forces that molded the phenotypic variation of C. sativa and lead to the observed similarity of patterns of genetic and morphophysiological levels of variation.Key words: Castanea sativa, isozymes, morphometries, carbon isotype discrimination.
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Virgona, JM, KT Hubick, HM Rawson, GD Farquhar, and RW Downes. "Genotypic Variation in Transpiration Efficiency, Carbon-Isotype Discrimination and Carbon Allocation During Early Growth in Sunflower." Functional Plant Biology 17, no. 2 (1990): 207. http://dx.doi.org/10.1071/pp9900207.
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Transpiration efficiency of dry matter production (W), carbon-isotope discrimination (�) and dry matter partitioning were measured on six sunflower (Helianthus annuus L.) genotypes grown for 32 days in a glasshouse. Two watering regimes, one well watered (HW) and the other delivering half the water used by the HW plants (LW), were imposed. Four major results emerged from this study. (1) There was significant genotypic variation in W in sunflower and this was closely reflected in Δ for both watering treatments. (2) The low watering regime caused a decrease in Δ but no change in W; nonetheless the genotypic ranking for either Δ or W was not significantly altered by water stress. (3) A positive correlation between W and biomass accumulation occurred among genotypes of HW plants. (4) Q, the ratio of total plant carbon content to leaf area, was positively correlated with W and negatively correlated with Δ. These results are discussed with reference to the connection between transpiration efficiency and plant growth. In short, Δ can be used to select for W among young vegetative sunflower plants. However, selection for W may be accompanied by changes in other important plant growth characteristics such as Q.
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Evans, JR, TD Sharkey, JA Berry, and GD Farquhar. "Carbon Isotope Discrimination measured Concurrently with Gas Exchange to Investigate CO2 Diffusion in Leaves of Higher Plants." Functional Plant Biology 13, no. 2 (1986): 281. http://dx.doi.org/10.1071/pp9860281.
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Conventional gas-exchange techniques that measure the stomatal conductance and rate of CO2 assimilation of leaves were combined with measurements of the carbon isotope composition of CO2 in air passing over a leaf. Isotopic discrimination during uptake was determined from the difference in the carbon isotope composition of air entering and leaving the leaf chamber. Isotopic discrimination measured over the short term correlated strongly with that determined from combusted leaf material. Environmental conditions were manipulated to alter the relative influences of stomatal conductance and carboxylation on the discrimination of carbon isotopes by intact leaves. With C3 plants, discrimination increased as the gradient in partial pressure of CO2 across the stomata decreased. For C4 plants there was little change in discrimination despite substantial changes in the diffusion gradient across the sto- mata. These results are consistent with, and provide the first direct experimental support for, theoretical equations describing discrimination during photosynthesis. Despite uncertainties about various processes affecting carbon isotope composition, the resistance to the transfer of CO2 from the intercellular airspaces to the sites of carboxylation in the mesophyll chloroplasts was estimated using this technique. For wheat the estimated resistance was 1.2-2.4 m2 s bar mol -1.
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Zámečník, J., and V. Holubec. "Heterogeneity in carbon isotope discrimination in leaves, stalks and spikes of ten annual wild Triticeae species." Czech Journal of Genetics and Plant Breeding 41, Special Issue (July 31, 2012): 212–17. http://dx.doi.org/10.17221/6177-cjgpb.
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Montanari, Shaena. "Discrimination factors of carbon and nitrogen stable isotopes in meerkat feces." PeerJ 5 (June 13, 2017): e3436. http://dx.doi.org/10.7717/peerj.3436.
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Stable isotope analysis of feces can provide a non-invasive method for tracking the dietary habits of nearly any mammalian species. While fecal samples are often collected for macroscopic and genetic study, stable isotope analysis can also be applied to expand the knowledge of species-specific dietary ecology. It is somewhat unclear how digestion changes the isotope ratios of animals’ diets, so more controlled diet studies are needed. To date, most diet-to-feces controlled stable isotope experiments have been performed on herbivores, so in this study I analyzed the carbon and nitrogen stable isotope ratios in the diet and feces of the meerkat (Suricata suricatta), a small omnivorous mammal. The carbon trophic discrimination factor between diet and feces (Δ13Cfeces) is calculated to be 0.1 ± 1.5‰, which is not significantly different from zero, and in turn, not different than the dietary input. On the other hand, the nitrogen trophic discrimination factor (Δ15Nfeces) is 1.5 ± 1.1‰, which is significantly different from zero, meaning it is different than the average dietary input. Based on data generated in this experiment and a review of the published literature, carbon isotopes of feces characterize diet, while nitrogen isotope ratios of feces are consistently higher than dietary inputs, meaning a discrimination factor needs to be taken into account. The carbon and nitrogen stable isotope values of feces are an excellent snapshot of diet that can be used in concert with other analytical methods to better understand ecology, diets, and habitat use of mammals.
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Raimanová, I., P. Svoboda, G. Kurešová, and J. Haberle. "The effect of different post-anthesis water supply on the carbon isotope discrimination of winter wheat grain." Plant, Soil and Environment 62, No. 7 (July 24, 2016): 329–34. http://dx.doi.org/10.17221/118/2016-pse.
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Raczka, Brett, Henrique F. Duarte, Charles D. Koven, Daniel Ricciuto, Peter E. Thornton, John C. Lin, and David R. Bowling. "An observational constraint on stomatal function in forests: evaluating coupled carbon and water vapor exchange with carbon isotopes in the Community Land Model (CLM4.5)." Biogeosciences 13, no. 18 (September 19, 2016): 5183–204. http://dx.doi.org/10.5194/bg-13-5183-2016.
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Abstract. Land surface models are useful tools to quantify contemporary and future climate impact on terrestrial carbon cycle processes, provided they can be appropriately constrained and tested with observations. Stable carbon isotopes of CO2 offer the potential to improve model representation of the coupled carbon and water cycles because they are strongly influenced by stomatal function. Recently, a representation of stable carbon isotope discrimination was incorporated into the Community Land Model component of the Community Earth System Model. Here, we tested the model's capability to simulate whole-forest isotope discrimination in a subalpine conifer forest at Niwot Ridge, Colorado, USA. We distinguished between isotopic behavior in response to a decrease of δ13C within atmospheric CO2 (Suess effect) vs. photosynthetic discrimination (Δcanopy), by creating a site-customized atmospheric CO2 and δ13C of CO2 time series. We implemented a seasonally varying Vcmax model calibration that best matched site observations of net CO2 carbon exchange, latent heat exchange, and biomass. The model accurately simulated observed δ13C of needle and stem tissue, but underestimated the δ13C of bulk soil carbon by 1–2 ‰. The model overestimated the multiyear (2006–2012) average Δcanopy relative to prior data-based estimates by 2–4 ‰. The amplitude of the average seasonal cycle of Δcanopy (i.e., higher in spring/fall as compared to summer) was correctly modeled but only when using a revised, fully coupled An − gs (net assimilation rate, stomatal conductance) version of the model in contrast to the partially coupled An − gs version used in the default model. The model attributed most of the seasonal variation in discrimination to An, whereas interannual variation in simulated Δcanopy during the summer months was driven by stomatal response to vapor pressure deficit (VPD). The model simulated a 10 % increase in both photosynthetic discrimination and water-use efficiency (WUE) since 1850 which is counter to established relationships between discrimination and WUE. The isotope observations used here to constrain CLM suggest (1) the model overestimated stomatal conductance and (2) the default CLM approach to representing nitrogen limitation (partially coupled model) was not capable of reproducing observed trends in discrimination. These findings demonstrate that isotope observations can provide important information related to stomatal function driven by environmental stress from VPD and nitrogen limitation. Future versions of CLM that incorporate carbon isotope discrimination are likely to benefit from explicit inclusion of mesophyll conductance.
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Malpica-Cruz, Luis, Sharon Z. Herzka, Oscar Sosa-Nishizaki, and Juan Pablo Lazo. "Tissue-specific isotope trophic discrimination factors and turnover rates in a marine elasmobranch: empirical and modeling results." Canadian Journal of Fisheries and Aquatic Sciences 69, no. 3 (March 2012): 551–64. http://dx.doi.org/10.1139/f2011-172.
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There are very few studies reporting isotopic trophic discrimination factors and turnover rates for marine elasmobranchs. A controlled laboratory experiment was conducted to estimate carbon and nitrogen isotope trophic discrimination factors and isotope turnover rates for blood, liver, muscle, cartilage tissue, and fin samples of neonate to young-of-the-year leopard sharks ( Triakis semifasciata ). Trophic discrimination factors varied (0.13‰–1.98‰ for δ13C and 1.08‰–1.76‰ for δ15N). Tissues reached or were close to isotopic equilibrium to the new diet after about a threefold biomass gain and 192 days. Liver and blood exhibited faster isotope turnover than muscle, cartilage tissue, and fin samples, and carbon isotopes turned over faster than those of nitrogen. Metabolic turnover contributed substantially to isotopic turnover, which differs from most reports for young marine teleosts. We modeled the relationship between muscle turnover rates and shark size by coupling laboratory results with growth rate estimates for natural populations. Model predictions for small, medium, and large wild leopard sharks indicate the time to isotopic equilibrium is from one to several years.
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Caemmerer, Susanne von, Martha Ludwig, Anthony Millgate, Graham D. Farquhar, Dean Price, Murray Badger, and Robert T. Furbank. "Carbon Isotope Discrimination during C4 Photosynthesis: Insights from Transgenic Plants." Functional Plant Biology 24, no. 4 (1997): 487. http://dx.doi.org/10.1071/pp97031.
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We have measured the discrimination against 13C during CO2 assimilation in Flaveria bidentis wild type plants and in transgenic Flaveria bidentis plants transformed (1) with an antisense RNA construct targeted to the nuclear encoded gene for the small subunit of Rubisco—these plants had reduced amounts of Rubisco, decreased CO2 assimilation rates and increased carbon isotope discrimination, which was also evident in the carbon isotope discrimination of leaf dry matter; and (2) transformed with the mature coding region of carbonic anhydrase, CA, from tobacco (Nicotiana tabacum) in the sense direction under the control of the cauliflower mosaic virus 35S promoter—these plants had slightly increased CA activity in the mesophyll as well as a 2–4-fold increase in CA activity in the bundle-sheath cells. The introduction of tobacco CA manifested itself by a reduction in CO2 assimilation rate and an increase in carbon isotope discrimination. We suggest that the increased carbon isotope discrimination is a result of increased bicarbonate leakage out of the bundle sheath.
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Farquhar, G. D., J. R. Ehleringer, and K. T. Hubick. "Carbon Isotope Discrimination and Photosynthesis." Annual Review of Plant Physiology and Plant Molecular Biology 40, no. 1 (June 1989): 503–37. http://dx.doi.org/10.1146/annurev.pp.40.060189.002443.
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Potočnik, Doris, Lidija Strojnik, Tome Eftimov, Alenka Levart, and Nives Ogrinc. "Fatty Acid and Stable Carbon Isotope Composition of Slovenian Milk: Year, Season, and Regional Variability." Molecules 25, no. 12 (June 23, 2020): 2892. http://dx.doi.org/10.3390/molecules25122892.
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This study examined the percentage and stable isotope ratios of fatty acids in milk to study seasonal, year, and regional variability. A total of 231 raw cow milk samples were analyzed. Samples were taken twice per year in 2012, 2013, and 2014, in winter and summer, covering four distinct geographical regions in Slovenia: Mediterranean, Alpine, Dinaric, and Pannonian. A discriminant analysis model based on fatty acid composition was effective in discriminating milk according to the year/season of production (86.9%), while geographical origin discrimination was less successful (64.1%). The stable isotope composition of fatty acids also proved to be a better biomarker of metabolic transformation processes in ruminants than discriminating against the origin of milk. Further, it was observed that milk from Alpine and Mediterranean regions was healthier due to its higher percentage of ω-3 polyunsaturated fatty acid and conjugated linoleic acid.
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Valentini, R., T. Anfodillo, and J. R. Ehleringer. "Water sources and carbon isotope composition (δ13C) of selected tree species of the Italian Alps." Canadian Journal of Forest Research 24, no. 8 (August 1, 1994): 1575–78. http://dx.doi.org/10.1139/x94-205.
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Selected species of the Italian Alpine region (Piceaabies (L.) Karst., Pinussylvestris L., Pinuscembra L., and Larixdecidua L.) have been investigated in terms of water-source utilization and carbon fixation estimated by the analysis of hydrogen and carbon stable isotopes composition at two sites of differing altitude (1000 and 1500 m above sea level). Larixdecidua is the species most dependent on groundwater in both sites, while Pinussylvestris utilizes rainwater to a greater extent. Concurrently, Pinussylvestris displayed the highest value of the carbon isotopic ratio (δ13C = −25.9 ± 0.6‰), while Larixdecidua had the most negative one (δ13C = −29.0 ± 0.4‰). A relationship was found between water-source utilization and carbon-isotope discrimination.
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Fielding, Anthony S., David H. Turpin, Robert D. Guy, Stephen E. Calvert, David W. Crawford, and Paul J. Harrison. "Influence of the carbon concentrating mechanism on carbon stable isotope discrimination by the marine diatom Thalassiosira pseudonana." Canadian Journal of Botany 76, no. 6 (June 1, 1998): 1098–103. http://dx.doi.org/10.1139/b98-069.
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There is no clear explanation why phytoplankton δ13C values are more negative in colder waters, but one current theory suggests that because colder waters hold more CO2, there is less diffusional limitation of CO2. This results in more discrimination against 13C and more negative phytoplankton δ13Cvalues. However, many species are able to actively take up CO2 or HCO3-, the latter being the major inorganic carbon species present in the dissolved inorganic carbon (DIC) pool of modern oceans. A previous study suggests that carbon concentrating mechanism (CCM) induction would affect carbon isotope discrimination, and this study confirms the presence of a relationship between discrimination and induction of a CCM in the marine diatom Thalassiosira pseudonana. CCM induction was measured by determining the half-saturation constant of photosynthesis (K0.5DIC). Values of K0.5DIC increased from 85 to 470 m M DIC over a range of ambient DIC levels from 0.2 to 2.7 mM. The fractionation factor increased from 10 to 21.3omicron over this same range. There was a significant relationship between K0.5DIC and the fractionation factor suggesting that CCM induction state influences carbon isotope discrimination. Other factors that influence discrimination may act through CCM induction.Key words: carbon isotope discrimination, carbon concentrating mechanism, Thalassiosira pseudonana, active carbon uptake, marine phytoplankton.
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Klaassen, Marcel, Michele Thums, and Ian D. Hume. "Effects of diet change on carbon and nitrogen stable-isotope ratios in blood cells and plasma of the long-nosed bandicoot (Perameles nasuta)." Australian Journal of Zoology 52, no. 6 (2004): 635. http://dx.doi.org/10.1071/zo04029.
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Carbon (C) and nitrogen (N) stable isotopes offer a powerful tool for assessing the extent of tissue assimilation of dietary components. However, the method relies on knowledge of diet–tissue isotopic discrimination and how quickly diet shifts become apparent in various tissues. In the present study, blood plasma and blood cells, tissues that are easily obtained under field conditions, were used to validate the stable isotope method over a period of 4–5 weeks using captive long-nosed bandicoots (Perameles nasuta). Diet–tissue discrimination effects appeared to be small. For C, derived diet–tissue isotopic discriminations were 1.4‰ for blood plasma and –0.2‰ for blood cells. For N the values were 2.8‰ and 2.1‰, respectively, and were independent of the nitrogen content of the food. C and N turnover measurements in the blood plasma and cells of the bandicoots indicated that blood plasma provides dietary information integrated over a period of ~3 weeks, whereas blood cells give an impression of the assimilated diet over a period of as much as half a year. These turnover rates were low compared with the little information available for birds and eutherian mammals, and probably relate to the typically low metabolic rate of marsupials.
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Dingkuhn, M., GD Farquhar, Datta SK De, JC O'Toole, and SKde Datta. "Discrimination of 13C among upland rices having different water use efficiencies." Australian Journal of Agricultural Research 42, no. 7 (1991): 1123. http://dx.doi.org/10.1071/ar9911123.
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Discrimination of stable carbon isotopes in leaves is physiologically linked to water-use efficiency. Twenty-eight contrasting rice (Oryza sativa L.) cultivars were grown in the Philippines as upland rice under continuous, mild water stress. In situ measurements of leaf level water-use efficiency (WUE), net photosynthesis, conductance, water potential and leaf rolling were reported previously. The present study used leaf samples from the same experiment to determine, by means of a mass spectrometer, the carbon isotope discrimination (-) and total C and N content. Among rice cultivars, - ranged from 19.8 to 21.5960, with japonica types having the lowest mean -, aus types, the greatest, and indica types, intermediate-the opposite pattern to that observed for WUE. Carbon isotope discrimination was negatively correlated with WUE across all cultivars (P < 0.001) and within japonica (P < 0 -01) and aus (P < 0.05) groups, but not among indica rices. No correlation was observed between - and any other measured variable. Varietal differences in - and WUE were not related to leaf N content or stomata1 conductance. High WUE was associated with high leaf C content (P < 0.01), with aus cultivars having the lowest mean WUE and C content among the genetic groups. We conclude that even under variable field conditions, analysis of foliar - is a potential tool to identify water-use efficient rice genotypes.
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Uriarte, Amaya, Alberto García, Aurelio Ortega, Fernando De la Gándara, José Quintanilla, and Raúl Laiz-Carrión. "Isotopic discrimination factors and nitrogen turnover rates in reared Atlantic bluefin tuna larvae (Thunnus thynnus): effects of maternal transmission." Scientia Marina 80, no. 4 (November 22, 2016): 447. http://dx.doi.org/10.3989/scimar.04435.25a.
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The use of stable isotope analysis to study animal diets requires estimates of isotopic turnover rates (half time, t50) and discrimination factors (Δ) for an accurate interpretation of trophic patterns. The stable isotopes of carbon and nitrogen were analysed for eggs and reared larvae of Thunnus thynnus, as well as for the different diets supplied during the experiment. The results showed high values of δ15N in eggs and larvae (n=646) until 4 DAH. After this time lapse, the stable isotope values declined progressively until 12 DAH, when notochord flexion began. The δ13C showed an inverse trend, suggesting that maternal inheritance of the stable isotopes is evident until pre-flexion stages. This study proposes a model for estimating maternal isotopic signatures of bluefin broodstock. After notochord flexion, larvae were fed with aquaculture-bred gilthead seabream, which resulted in a rapid increase of bluefin larvae δ15N values together with a rapid decrease in δ13C values. The estimated nitrogen half-time to reach the steady state from the diet was 2.5±0.3 days and the discrimination factor was 0.4±0.3(‰). These results represent the first data set that has allowed isotopic nitrogen turnover rates and discrimination factors of the larval stages of bluefin tuna to be estimated.
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Arneson, Lynne S., Stephen MacAvoy, and Ethan Basset. "Metabolic protein replacement drives tissue turnover in adult mice." Canadian Journal of Zoology 84, no. 7 (July 1, 2006): 992–1002. http://dx.doi.org/10.1139/z06-081.
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Stable isotopes are increasingly being used to examine ecological and physiological questions, such as dietary choices, migration routes and timing, and physiological condition. To address these questions in the field, laboratory experiments must be done to determine diet–tissue discrimination values and turnover rates for stable isotopes in tissues. In this study, we examined the carbon and nitrogen turnover rates of whole blood, skeletal muscle, liver, kidney, heart, and brain, as well as the sulfur turnover rate of whole blood, skeletal muscle, and liver in Mus musculus L., 1758 following a diet change. By examining tissue isotope change in two groups of mice fed different diets, we found that tissues turnover at different rates (in order of fastest to slowest — liver, kidney, heart, brain, whole blood, skeletal muscle), but that carbon, nitrogen, and sulfur isotopes turned over with similar half-lives within a single tissue. By using a diet with different nutrient isotopic values, we also calculated that up to approximately 90%–95% of carbon in newly synthesized tissue was contributed by dietary protein. These results will provide field researchers with additional tissue isotopic half-lives to elucidate dietary history with a greater degree of certainty. The tissue sulfur half-lives provide an extra stable isotope that may be used in situations where carbon and nitrogen values do not differ between old and new nutrient sources.
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Wei, Yang, and Li Pin-Fang. "Association of carbon isotope discrimination with leaf gas exchange and water use efficiency in maize following soil amendment with superabsorbent hydrogel." Plant, Soil and Environment 64, No. 10 (October 15, 2018): 484–90. http://dx.doi.org/10.17221/463/2018-pse.
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The correlation of carbon isotope discrimination (△<sup>13</sup>C) with photosynthetic gas exchange and water use efficiency (WUE) in maize was investigated under low rainfall conditions with or without superabsorbent polymer (SAP). SAP (45 kg/ha) was mixed into the top 10 cm soil layer at sowing in lysimeters. Compared with the control plants not treated with SAP, the application of SAP increased net photosynthesis rate; stomatal conductance (g<sub>s</sub>); transpiration rate; chlorophyll content (Chl) and intrinsic water use efficiency at leaf level (WUE<sub>i</sub>), but decreased intercellular CO<sub>2</sub> concentration (C<sub>i</sub>) and leaf △<sup>13</sup>C. In plants supplied with SAP, leaf △<sup>13</sup>C was positively correlated with C<sub>i</sub> (r = 0.864, P < 0.01) and negatively correlated with g<sub>s</sub> and WUE<sub>i</sub> (r = –0.860 and –0.626, P < 0.01, respectively). Leaf △<sup>13</sup>C was not correlated with Chl with or without SAP. Grain △<sup>13</sup>C significantly decreased by 12.4% and showed a significant negative correlation with grain WUE under SAP treatments (r = –0.670, P < 0.05). These results suggest that in the presence of SAP, maize leaf and grain △<sup>13</sup>C could be good indicators for evaluating maize WUE during periods of low rainfall.
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DeMots, Rachel L., James M. Novak, Karen F. Gaines, Aaron J. Gregor, Christopher S. Romanek, and Daniel A. Soluk. "Tissue–diet discrimination factors and turnover of stable carbon and nitrogen isotopes in white-footed mice (Peromyscus leucopus)." Canadian Journal of Zoology 88, no. 10 (October 2010): 961–67. http://dx.doi.org/10.1139/z10-063.
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Stable isotope analysis has become an increasingly valuable tool in investigating animal ecology. Here we document the turnover rates for carbon in the liver, muscle, and whole blood tissue, as well as the tissue–diet discrimination values for carbon and nitrogen isotopes in the liver, whole blood, muscle, and hair, of the white-footed mouse ( Peromyscus leucopus (Rafinesque, 1818)). A 168-day diet-switching experiment was conducted with a laboratory population of white-footed mice. The δ13C values for all tissues deviated less than 1‰ from those of the diet except for whole blood, which had a slightly higher tissue–diet discrimination factor of 1.8‰. All tissues were enriched in 15N by approximately 3‰ relative to the diet except for liver tissue, which was 4.5‰ higher than the dietary δ15N value. Turnover rates for tissues of white-footed mice were ranked liver > whole blood > muscle. The half-lives calculated for liver tissue differed significantly between the two diet switches performed in this experiment. We demonstrate that there is potential for variation in tissue–diet discrimination values and tissue turnover rates between even closely related species. These findings highlight the importance of determining species-specific estimates of these parameters prior to the use of stable isotope analysis in field investigations of animal ecology.
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Cernusak, Lucas A., John D. Marshall, Jonathon P. Comstock, and Nick J. Balster. "Carbon isotope discrimination in photosynthetic bark." Oecologia 128, no. 1 (June 2001): 24–35. http://dx.doi.org/10.1007/s004420100629.
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Caemmerer, SV, and JR Evans. "Determination of the Average Partial Pressure of CO2 in Chloroplasts From Leaves of Several C3 Plants." Functional Plant Biology 18, no. 3 (1991): 287. http://dx.doi.org/10.1071/pp9910287.
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Measurements of CO2 and water vapour exchange by leaves were combined with measurements of carbon isotope composition (13C/12C) of CO2 in the air passing over the leaf. Carbon isotope discrimination during CO2 uptake was determined from the difference in carbon isotope composition of the air leaving the leaf chamber with or without a leaf enclosed. Leaves of wheat plants grown with different nitrogen nutrition and leaves of several other species were examined. The measurements, made at different irradiances for a given leaf, showed that carbon isotope discrimination was strongly correlated with the rate of CO2 assimilation as well as the ratio of intercellular to ambient partial pressure of CO2, pI/pa. A function relating carbon isotope discrimination to the rate of CO2 assimilation was used to estimate the CO2 transfer conductance, gw, from the substomatal cavities to the sites of carboxylation for individual leaves. The photosynthetic capacity correlated with the CO2 transfer conductance, gw, and the average ratio of chloroplastic to intercellular partial pressure of CO2, pI/pa, was 0.7. This means that in general under high irradiance, the ratio of chloroplastic to ambient partial pressure of CO2 is about 0.5. In wheat, variation in gw was correlated with the chloroplast surface area appressing intercellular airspaces.
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Mauffrey, Jean-François, and François Catzeflis. "Ecological and isotopic discrimination of syntopic rodents in a neotropical rain forest of French Guiana." Journal of Tropical Ecology 19, no. 2 (February 6, 2003): 209–14. http://dx.doi.org/10.1017/s0266467403003237.
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Stable isotopes are commonly used in ecological studies to infer food resources (Ambrose & DeNiro 1986, Bocherens et al. 1990,1991,1994;Yoshinaga et al. 1991) since isotopic composition is conserved during the feeding process. Moreover,for herbivorous (sensu lato) species, it is often possible to identify the main resource because different photosynthetic pathways generate different values of carbon isotope ratios (Park & Epstein 1961, Sternberg et al. 1984). This allows the characterization of broad biota such as savannas or forest and discrimination of grazers from sympatric folivorous species (DeNiro & Epstein 1978).
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Rioux, Ève, Fanie Pelletier, and Martin-Hugues St-Laurent. "From diet to hair and blood: empirical estimation of discrimination factors for C and N stable isotopes in five terrestrial mammals." Journal of Mammalogy 101, no. 5 (October 3, 2020): 1332–44. http://dx.doi.org/10.1093/jmammal/gyaa108.
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Abstract Carbon and nitrogen stable isotope ratios are used widely to describe wildlife animal diet composition and trophic interactions. To reconstruct consumer diet, the isotopic differences between consumers and their diet items—called the trophic discrimination factor (TDF)—must be known. Proxies of diet composition are sensitive to the accuracy of TDFs. However, specific TDFs are still missing for many species and tissues because only a few controlled studies have been carried out on captive animals. The aim of this study was to estimate TDFs for hair and blood for carbon and nitrogen stable isotopes for caribou, moose, white-tailed deer, eastern coyote, and black bear. We obtained stable isotope ratios for diet items, hair, and blood samples, of 21 captive adult mammals. Diet–tissue discrimination factors for carbon in hair (∆ 13CLE) ranged from 0.96‰ to 3.72‰ for cervids, 3.01‰ to 3.76‰ for coyote, and 5.15‰ to 6.35‰ for black bear, while nitrogen discrimination factors (∆ 15N) ranged from 2.58‰ to 5.95‰ for cervids, 2.90‰ to 3.13‰ for coyote, and 4.48‰ to 5.44‰ for black bear. The ∆ 13CLE values in coyote blood components ranged from 2.20‰ to 2.69‰ while ∆ 15N ranged from 3.30‰ to 4.41‰. In caribou serum, ∆ 13CLE reached 3.34 ± 1.28‰ while ∆ 15N reached 5.02 ± 0.07‰. The TDFs calculated in this study will allow the evaluation of diet composition and trophic relationships between these five mammal species and will have important implications for the study of endangered caribou populations for which the use of noninvasive tissue sampling is highly relevant.
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Passey, Benjamin H. "Reconstructing Terrestrial Environments Using Stable Isotopes in Fossil Teeth and Paleosol Carbonates." Paleontological Society Papers 18 (November 2012): 167–94. http://dx.doi.org/10.1017/s1089332600002606.
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Carbon isotopes in Neogene-age fossil teeth and paleosol carbonates are commonly interpreted in the context of past distributions of C3 and C4 vegetation. These two plant types have very different distributions in relation to climate and ecology, and provide a robust basis for reconstructing terrestrial paleoclimates and paleoenvironments during the Neogene. Carbon isotopes in pre-Neogene fossil teeth are usually interpreted in the context of changes in the δ13C value of atmospheric CO2, and variable climate-dependent carbon-isotope discrimination in C3 plants. Carbon isotopes in pre-Neogene soil carbonates can be used to estimate past levels of atmospheric CO2. Oxygen isotopes in fossil teeth and paleosol carbonates primarily are influenced by the oxygen isotopic compositions of ancient rainfall and surface waters. The oxygen isotopic composition of rainfall is has a complex, but tractable, relationship with climate, and variably relates to temperature, elevation, precipitation amount, and other factors. Mammal species that rely on moisture in dietary plant tissues to satisfy their water requirements (rather than surface drinking water) may have oxygen isotopic compositions that track aridity. Thus, oxygen isotopes of fossil mammals can place broad constraints on paleoaridity. Carbonate clumped isotope thermometry allows for reconstruction of soil temperatures at the time of pedogenic carbonate mineralization. The method is unique because it is the only thermodynamically based isotopic paleothermometer that does not require assumptions about the isotopic composition of the fluid in which the archive mineral formed. Soil temperature reflects a complex interplay of air temperature, solar radiative heating, latent heat effects, soil thermal diffusivity, and seasonal variations of these parameters. Because plants and most animals live in and/or near the soil, soil temperature is an important aspect of terrestrial (paleo)climate.
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CAEMMERER, S. "Carbon isotope discrimination in C3-C4 intermediates." Plant, Cell and Environment 15, no. 9 (December 1992): 1063–72. http://dx.doi.org/10.1111/j.1365-3040.1992.tb01656.x.
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Hidy, D., L. Haszpra, Z. Barcza, A. Vermeulen, Z. Tuba, and Z. Nagy. "Modelling of carbon isotope discrimination by vegetation." Photosynthetica 47, no. 3 (September 1, 2009): 457–70. http://dx.doi.org/10.1007/s11099-009-0070-z.
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Abraham, Wolf-Rainer, Christian Hesse, and Oliver Pelz. "Ratios of Carbon Isotopes in Microbial Lipids as an Indicator of Substrate Usage." Applied and Environmental Microbiology 64, no. 11 (November 1, 1998): 4202–9. http://dx.doi.org/10.1128/aem.64.11.4202-4209.1998.
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ABSTRACT The occurrence and abundance of microbial fatty acids have been used for the identification of microorganisms in microbial communities. However, these fatty acids can also be used as indicators of substrate usage. For this, a systematic investigation of the discrimination of the stable carbon isotopes by different microorganisms is necessary. We grew 11 strains representing major bacterial and fungal species with four different isotopically defined carbon sources and determined the isotope ratios of fatty acids of different lipid fractions. A comparison of the differences of δ13C values of palmitic acid (C16:0) with the δ13C values of the substrates revealed that the isotope ratio is independent of the growth stage and that most microorganisms showed enrichment of C16:0 with 13C when growing on glycerol. With the exception of Burkholderia gladioli, all microorganism showed depletion of 13C in C16:0while incorporating the carbons of glucose, and most of them were enriched with 13C from mannose, with the exception ofPseudomonas fluorescens and the Zygomycotina. Usually, the glycolipid fractions are depleted in 13C compared to the phospholipid fractions. The δ13C pattern was not uniform within the different fatty acids of a given microbial species. Generally, tetradecanoic acid (C14:0) was depleted of13C compared to palmitic acid (C16:0) while octadecanoic acid (C18:0) was enriched. These results are important for the calibration of a new method in which δ13C values of fatty acids from the environment delineate the use of bacterial substrates in an ecosystem.
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Federer, R. N., T. E. Hollmén, D. Esler, M. J. Wooller, and S. W. Wang. "Stable carbon and nitrogen isotope discrimination factors from diet to blood plasma, cellular blood, feathers, and adipose tissue fatty acids in Spectacled Eiders (Somateria fischeri)." Canadian Journal of Zoology 88, no. 9 (September 2010): 866–74. http://dx.doi.org/10.1139/z10-052.
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Stable isotope analyses of animal tissues can be used to infer diet through application of mixing models. An important component in a mixing model is the incorporation of stable isotope discrimination factors so that isotopic shifts between diet and tissues built from the diet can be accounted for when comparing tissues to potential food sources. We determined the stable carbon and nitrogen isotopic discrimination factors between lipid-free diet and blood plasma, cellular blood, and adult chest contour feathers for captive female Spectacled Eiders ( Somateria fischeri (Brandt, 1847)). Mean discrimination factors for blood components and feathers were either similar or slightly larger compared with previously studied species. Additionally, we determined the stable carbon isotope discrimination factors between dietary lipids and adipose tissue fatty acids using three adipose tissue biopsies from captive male Spectacled Eiders that were fed three different diet treatments. Isotopic signatures of adipose tissue fatty acids closely reflected shifts in the diet and were either similar to or increased relative to diet. Our study provides a foundation for research using tissues as end-members in stable isotope nutrient allocation models and foraging ecology studies of Spectacled Eiders, and will provide the most applicable isotope data to date for sea ducks.
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Erez, Jonathan, Anne Bouevitch, and Aaron Kaplan. "Carbon isotope fractionation by photosynthetic aquatic microorganisms: experiments with Synechococcus PCC7942, and a simple carbon flux model." Canadian Journal of Botany 76, no. 6 (June 1, 1998): 1109–18. http://dx.doi.org/10.1139/b98-067.
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Stable carbon isotopes (12C and 13C) are widely used to trace biogeochemical processes in the global carbon cycle. Natural fractionation of carbon isotopes is mainly due to the discrimination of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) against 13C during photosynthesis. In marine and other aquatic microorganisms, this fractionation is lowered when the dissolved CO2 (CO2(aq)) is decreasing, but the underlying mechanisms are poorly understood. Cultured Synechococcus PCC7942 showed maximum isotopic fractionations of -33omicron (in delta 13C units) relative to the total inorganic carbon (Ci) when CO2(aq) is above 30 m M. As the culture grew, pH increased, CO2(aq) was lower than 1 m M, and the Ci concentrating mechanism was induced although the Ci was above 3 mM. The isotopic fractionation was drastically reduced to values of -1 to -3 omicron relative to Ci. A simple carbon isotope flux model suggests that during the first stages of the experiment the total uptake (F1) was roughly three- to four-fold greater than the photosynthetic net accumulation (F2). When the Ci concentrating mechanism was induced, the leakage of CO2 from the cells declined, the cells started to utilize HCO3- and the F1/F2 ratio decreased to values close to 1. Based on this model the isotopic variability of oceanic phytoplankton suggests that the F1/F2 ratio may be above 3 in high latitudes and ~1.1 in equatorial waters, where the Ci concentrating mechanism is probably induced. Attempts to reconstruct past atmospheric CO2 levels and paleoproductivity should take into account the effects of the Ci concentrating mechanism on the isotopic fractionation of aquatic primary producers.Key words: carbon concentrating mechanism, carbon isotope fractionation, CO2, photosynthesis.
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McNevin, Dennis B., Murray R. Badger, Heather J. Kane, and Graham D. Farquhar. "Measurement of (carbon) kinetic isotope effect by Rayleigh fractionation using membrane inlet mass spectrometry for CO2-consuming reactions." Functional Plant Biology 33, no. 12 (2006): 1115. http://dx.doi.org/10.1071/fp06201.
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Methods for determining carbon isotope discrimination, Δ, or kinetic isotope effects, α, for CO2-consuming enzymes have traditionally been cumbersome and time-consuming, requiring careful isolation of substrates and products and conversion of these to CO2 for measurement of isotope ratio by mass spectrometry (MS). An equation originally derived by Rayleigh in 1896 has been used more recently to good effect as it only requires measurement of substrate concentrations and isotope ratios. For carboxylation reactions such as those catalysed by d-ribulose-1,5-bisphosphate carboxylase / oxygenase (RuBisCO, EC 4.1.1.39) and PEP carboxylase (PEPC, EC 4.1.1.31), this has still required sampling of reactions at various states of completion and conversion of all inorganic carbon to CO2, as well as determining the amount of substrate consumed. We introduce a new method of membrane inlet MS which can be used to continuously monitor individual CO2 isotope concentrations, rather than isotope ratio. This enables the use of a simplified, new formula for calculating kinetic isotope effects, based on the assumptions underlying the original Rayleigh fractionation equation and given by: --> The combination of inlet membrane MS and this formula yields measurements of discrimination in less than 1 h. We validate our method against previously measured values of discrimination for PEP carboxylase and RuBisCO from several species.
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Hobson, Keith A., and Franz Bairlein. "Isotopic fractionation and turnover in captive Garden Warblers (Sylvia borin): implications for delineating dietary and migratory associations in wild passerines." Canadian Journal of Zoology 81, no. 9 (September 1, 2003): 1630–35. http://dx.doi.org/10.1139/z03-140.
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There is currently a great deal of interest in using stable-isotope methods to investigate diet and migratory connections in wild passerines. To apply these methods successfully, it is important to understand how stable isotopes discriminate or change between diet and the tissue of interest and what the element-turnover rates are in metabolically active tissues. Of particular use are studies that sample birds non-destructively through the use of blood and feathers. We investigated patterns of isotopic discrimination between diet and blood and feathers of Garden Warblers (Sylvia borin) raised on an isotopically homogeneous diet (48% C, 5% N) and then switched to one of two experimental diets, mealworms (56.8% C, 8.3% N) and elderberries, Sambucus niger (47.4% C, 1.5% N). We established that the discrimination factors between diet and blood appropriate for stable carbon (δ13C) and nitrogen (δ15N) isotopes are +1.7‰ and +2.4‰, respectively. For feathers, these values were +2.7‰ and +4‰, respectively. Turnover of elemental nitrogen in whole blood was best approximated by an exponential-decay model with a half-life of 11.0 ± 0.8 days (mean ± SD). Corresponding turnover of carbon was estimated to range from 5.0 ± 0.7 to 5.7 ± 0.8 days. We conclude that this decoupling of nitrogen- and carbon-turnover rates can be explained by differences in metabolic routing of dietary macromolecules. Our results suggest that tracking frugivory in migratory passerines that switch diets between insects and fruits may be complicated if only a trophic-level estimate is made using δ15N measurements.
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Olivas-García, J. Miguel, Bert M. Cregg, and Thomas C. Hennessey. "Genotypic variation in carbon isotope discrimination and gas exchange of ponderosa pine seedlings under two levels of water stress." Canadian Journal of Forest Research 30, no. 10 (October 1, 2000): 1581–90. http://dx.doi.org/10.1139/x00-080.
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As part of a program to select ponderosa pine (Pinus ponderosa Dougl. ex Laws.) genotypes for improved drought tolerance, we examined physiological and morphological characteristics of 12 half-sib families of ponderosa pine from four seed sources; New Mexico, South Dakota, Nebraska, and Wyoming. We analyzed genetic variation in carbon isotope discrimination (Δ), photosynthetic gas exchange, needle morphology, and growth of 2-year-old seedlings from the four seed sources grown under two levels of moisture availability. To gain a better understanding of within-provenance variation and identify opportunities to refine selection strategies, we also examined family within seed source variation in the traits. Water stress significantly (P < 0.05) reduced net photosynthesis (A), needle conductance to water vapor (gwv), carbon isotope discrimination (Δ), and growth of the seedlings as compared to well-watered seedlings. However, instantaneous water use efficiency (A/gwv) did not differ between water treatments. Seedlings from New Mexico had significantly lower gwv and higher A/gwv than seedlings from the other sources. Carbon isotope discrimination was lowest for seedlings from New Mexico and Nebraska. Families within seed sources varied significantly in A, gwv, stomatal density, needle length, height increment, and Δ. Carbon isotope discrimination was significantly correlated with gwv but not with A, supporting results from mature trees suggesting that variation in Δ in ponderosa pine is more related to gwv than to A. Seed source × water treatment interactions were not observed for any of the traits analyzed. These results support our previous assertion that genotype × environment interaction in Δ of mature ponderosa pine trees from these sources grown in Nebraska and Oklahoma was related to factors other than moisture availability.
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Carolan, J. Veliscek, D. Mazumder, C. Dimovski, R. Diocares, and J. Twining. "Biokinetics and discrimination factors for δ13C and δ15N in the omnivorous freshwater crustacean, Cherax destructor." Marine and Freshwater Research 63, no. 10 (2012): 878. http://dx.doi.org/10.1071/mf11240.
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Knowledge and understanding of biokinetics and discrimination factors for carbon-13 (δ13C) and nitrogen-15 (δ15N) are important when using stable isotopes for food-web studies. Therefore, we performed a controlled laboratory diet-switch experiment to examine diet–tissue and diet–faeces discrimination factors as well as the biokinetics of stable-isotope assimilation in the omnivorous freshwater crustacean, Cherax destructor. The biokinetics of δ13C could not be established; however, the δ15N value of C. destructor tissue reached equilibrium after 80 ± 35 days, with an estimated biological half-time for 15N of 19 ± 5 days. Metabolic activity contributed to the turnover of 15N by nearly an order of magnitude more than growth. The diet–tissue discrimination factors at the end of the exposure were estimated as –1.1 ± 0.5‰ for δ13C and +1.5 ± 1.0‰ for δ15N, indicating that a δ15N diet–tissue discrimination factor different from the typically assumed +3.4‰ may be required for freshwater macroinvertebrates such as C. destructor. The diet–faeces discrimination factor for δ15N after 120 days was estimated as +0.9 ± 0.5‰. The present study provides an increased understanding of the biokinetics and discrimination factors for a keystone freshwater macroinvertebrate that will be valuable for future food-web studies in freshwater ecosystems.
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Hokmabadi, H., K. Arzani, and P. F. Grierson. "Growth, chemical composition, and carbon isotope discrimination of pistachio (Pistacia vera L.) rootstock seedlings in response to salinity." Australian Journal of Agricultural Research 56, no. 2 (2005): 135. http://dx.doi.org/10.1071/ar04088.
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Pistachio is considered a potential crop for many semi-arid regions affected by salinisation. We examined the effects of salinity on growth of 3 pistachio rootstocks: Badami-e-zarand, Sarakhs, and Ghazvini. Rootstocks were grown in soil in 8-L polyethylene pots and irrigated every 3 days with treatments of 0, 75, 150, or 225 mm NaCl. We measured above-ground biomass, allocation of C to root systems and foliage, and carbon isotope discrimination (Δ) and proline accumulation after 30 days and again after 60 days. Relative growth rate (RGR) decreased with time for all treatments and rootstocks. RGR and net assimilation rates (NARw) decreased with increasing salinity. In all rootstocks, NARw, but not leaf weight ratio (LWR), was significantly correlated with RGR, indicating that NARw was an important factor underlying growth responses among rootstocks. Increased salinity did not affect leaf water potential (Ψleaf), even though proline concentrations increased with increasing NaCl concentration, particularly in the Ghazvini rootstocks. Both Cl– and Na+ concentrations in leaves increased from 30 to 60 days but not in roots and stems. The Sarakhs rootstocks accumulated more of Cl– and Na+ compared with other rootstocks. K+ concentration in the roots and stems of all rootstocks also decreased with increasing salinity at both 30 and 60 days. Concentrations of Ca2+ in stems and root systems, but not in leaves, were also reduced by increased salinity in all rootstocks but only after 60 days. Carbon isotope discrimination (Δ) decreased with increased salinity in the leaves, stems, and roots; however, there was no significant difference in carbon isotope discrimination among rootstocks. We conclude that the Ghazvini rootstock was the most salt tolerant among the rootstocks tested. Carbon isotope discrimination in pistachio rootstocks may be a useful indicator of cumulative salinity history of the plant but is not a suitable indicator for pre-screening of pistachio rootstocks for salinity resistance.
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Lambrides, C. J., S. C. Chapman, and R. Shorter. "Genetic Variation for Carbon Isotope Discrimination in Sunflower." Crop Science 44, no. 5 (September 2004): 1642–53. http://dx.doi.org/10.2135/cropsci2004.1642.
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Hubick, Kerry T., Graeme L. Hammer, Graham D. Farquhar, Len J. Wade, Susanne von Caemmerer, and Sally A. Henderson. "Carbon Isotope Discrimination Varies Genetically in C4 Species." Plant Physiology 92, no. 2 (February 1, 1990): 534–37. http://dx.doi.org/10.1104/pp.92.2.534.
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Morgan, J. A., G. Zerbi, M. Martin, M. Y. Mujahid, and J. S. Quick. "Carbon Isotope Discrimination and Productivity in Winter Wheat)." Journal of Agronomy and Crop Science 171, no. 5 (December 1993): 289–97. http://dx.doi.org/10.1111/j.1439-037x.1993.tb00143.x.
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Smedley, Mark P., Todd E. Dawson, Jonathan P. Comstock, Lisa A. Donovan, Dorothy E. Sherrill, Craig S. Cook, and James R. Ehleringer. "Seasonal carbon isotope discrimination in a grassland community." Oecologia 85, no. 3 (January 1991): 314–20. http://dx.doi.org/10.1007/bf00320605.
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Warren, Charles R., John F. McGrath, and Mark A. Adams. "Water availability and carbon isotope discrimination in conifers." Oecologia 127, no. 4 (May 2001): 476–86. http://dx.doi.org/10.1007/s004420000609.
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Craufurd, P. Q., R. B. Austin, E. Acevedo, and M. A. Hall. "Carbon isotope discrimination and grain-yield in barley." Field Crops Research 27, no. 4 (November 1991): 301–13. http://dx.doi.org/10.1016/0378-4290(91)90038-w.
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Bucholz, Ethan R., Kristen M. Waring, Thomas E. Kolb, Jared K. Swenson, and Amy V. Whipple. "Water relations and drought response of Pinus strobiformis." Canadian Journal of Forest Research 50, no. 9 (September 2020): 905–16. http://dx.doi.org/10.1139/cjfr-2019-0423.
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Southwestern white pine (Pinus strobiformis Engelm.) faces dual threats of climate change shifting its environmental niche and mortality due to a nonnative, invasive fungal pathogen. To inform efforts to sustain this species, we established experimental field trials in three common gardens along an elevational gradient with drought treatments to assess trait responses in southwestern white pine. We measured predawn and midday water potential on 44 maternal families from 10 populations at each garden. We used regression between predawn and midday water potentials to estimate hydroscape area, an index of stomatal regulation of transpiration. We measured leaf carbon isotope ratio and estimated carbon isotope discrimination and leaf mass per area to understand the effects of gardens and treatments on stomatal aperture and leaf structure. Water stress caused by experimental drought and temperature decreased leaf carbon isotope discrimination and leaf mass per area, indicating formation of thin leaves with low stomatal conductance in response to heat and drought. The hydroscape area of southwestern white pine suggests tight control of transpiration via stomatal closure, similar to other isohydric pines. Families with greater stomatal closure (inferred from carbon isotope ratio) at the warm, dry garden had higher survival than other families, suggesting an important role of isohydry in acclimation of southwestern white pine to expected habitat drying and warming.
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van der Velde, I. R., J. B. Miller, K. Schaefer, G. R. van der Werf, M. C. Krol, and W. Peters. "Terrestrial cycling of <sup>13</sup>CO<sub>2</sub> by photosynthesis, respiration, and biomass burning in SiBCASA." Biogeosciences 11, no. 23 (December 1, 2014): 6553–71. http://dx.doi.org/10.5194/bg-11-6553-2014.
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Abstract. We present an enhanced version of the SiBCASA terrestrial biosphere model that is extended with (a) biomass burning emissions from the SiBCASA carbon pools using remotely sensed burned area from the Global Fire Emissions Database (GFED), (b) an isotopic discrimination scheme that calculates 13C signatures of photosynthesis and autotrophic respiration, and (c) a separate set of 13C pools to carry isotope ratios into heterotrophic respiration. We quantify in this study the terrestrial exchange of CO2 and 13CO2 as a function of environmental changes in humidity and biomass burning. The implementation of biomass burning yields similar fluxes as CASA-GFED both in magnitude and spatial patterns. The implementation of isotope exchange gives a global mean discrimination value of 15.2‰, ranges between 4 and 20‰ depending on the photosynthetic pathway in the plant, and compares favorably (annually and seasonally) with other published values. Similarly, the isotopic disequilibrium is similar to other studies that include a small effect of biomass burning as it shortens the turnover of carbon. In comparison to measurements, a newly modified starch/sugar storage pool propagates the isotopic discrimination anomalies to respiration much better. In addition, the amplitude of the drought response by SiBCASA is lower than suggested by the measured isotope ratios. We show that a slight increase in the stomatal closure for large vapor pressure deficit would amplify the respired isotope ratio variability. Our study highlights the importance of isotope ratio observations of 13C to assess and improve biochemical models like SiBCASA, especially with regard to the allocation and turnover of carbon and the responses to drought.
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Stanek, A. E., N. Wolf, J. M. Welker, and S. Jensen. "Experimentally derived incorporation rates and diet-to-tissue discrimination values for carbon and nitrogen stable isotopes in gray wolves (Canis lupus) fed a marine diet." Canadian Journal of Zoology 97, no. 12 (December 2019): 1225–30. http://dx.doi.org/10.1139/cjz-2019-0049.
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Recent studies have noted the differential effects of marine versus terrestrial diets on the carbon and nitrogen stable isotope (13C and 15N, respectively) diet-to-tissue discrimination values and incorporation rates for omnivorous and carnivorous mammals. Inaccurate estimates of these parameters may result in misrepresentation of diet composition or in the timing of diet shifts. Here, we present the results of a diet-switch experiment designed to estimate diet-to-tissue discrimination values and incorporation rates for tissues of gray wolves (Canis lupus Linnaeus, 1758) fed a diet of Pacific salmon (genus Oncorhynchus Suckley, 1861). Our results demonstrate substantial differences in both parameters between wolves maintained on a marine (salmon) diet and wolves maintained on terrestrially sourced prey (beef, Bos taurus Linnaeus, 1758). Increased awareness of the significance of marine resources to omnivorous and carnivorous consumers, like wolves, highlights the importance of phenomenological and mechanistic understandings of the effects of fish and other marine prey on dietary investigations based on stable isotopes.
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Londry, Kathleen L., and David J. Des Marais. "Stable Carbon Isotope Fractionation by Sulfate-Reducing Bacteria." Applied and Environmental Microbiology 69, no. 5 (May 2003): 2942–49. http://dx.doi.org/10.1128/aem.69.5.2942-2949.2003.
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ABSTRACT Biogeochemical transformations occurring in the anoxic zones of stratified sedimentary microbial communities can profoundly influence the isotopic and organic signatures preserved in the fossil record. Accordingly, we have determined carbon isotope discrimination that is associated with both heterotrophic and lithotrophic growth of pure cultures of sulfate-reducing bacteria (SRB). For heterotrophic-growth experiments, substrate consumption was monitored to completion. Sealed vessels containing SRB cultures were harvested at different time intervals, and δ13C values were determined for gaseous CO2, organic substrates, and products such as biomass. For three of the four SRB, carbon isotope effects between the substrates, acetate or lactate and CO2, and the cell biomass were small, ranging from 0 to 2‰. However, for Desulfotomaculum acetoxidans, the carbon incorporated into biomass was isotopically heavier than the available substrates by 8 to 9‰. SRB grown lithoautotrophically consumed less than 3% of the available CO2 and exhibited substantial discrimination (calculated as isotope fractionation factors [α]), as follows: for Desulfobacterium autotrophicum, α values ranged from 1.0100 to 1.0123; for Desulfobacter hydrogenophilus, the α value was 0.0138, and for Desulfotomaculum acetoxidans, the α value was 1.0310. Mixotrophic growth of Desulfovibrio desulfuricans on acetate and CO2 resulted in biomass with a δ13C composition intermediate to that of the substrates. The extent of fractionation depended on which enzymatic pathways were used, the direction in which the pathways operated, and the growth rate, but fractionation was not dependent on the growth phase. To the extent that environmental conditions affect the availability of organic substrates (e.g., acetate) and reducing power (e.g., H2), ecological forces can also influence carbon isotope discrimination by SRB.
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Lin, GH, and LDSL Sternberg. "Effect of Growth Form, Salinity, Nutrient and Sulfide on Photosynthesis, Carbon Isotope Discrimination and Growth of Red Mangrove (Rhizophora mangle L.)." Functional Plant Biology 19, no. 5 (1992): 509. http://dx.doi.org/10.1071/pp9920509.
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The red mangrove (Rhizophora mangle L.), a dominant mangrove species in Florida, frequently occurs in two distinct growth forms, scrub and tall trees. These two growth forms show significant differences in physiology in the field, with lower CO2 assimilation rate, stomatal conductance, and carbon isotope discrimination or higher transpiration efficiency for the scrub form. To elucidate the possible factors responsible for these physiological differences, we studied the physiological and growth responses of scrub and tall red mangrove seedlings grown hydroponically in the greenhouse under 12 different growth conditions combining three salinities (100, 250, 500 mM NaCl), two nutrient levels (10, 100% strength of full nutrient solution), and two sulfide concentrations (0, 2.0 mM Na2S). The two growth forms showed similar physiological and growth responses to these treatments, suggesting no genetic control of physiological and growth differences between the growth forms of this species. High salinity, low nutrient level, and high sulfide concentration all significantly decreased CO2 assimilation, stomatal conductance, and plant growth, but only salinity significantly decreased intercellular CO2 concentration and leaf carbon isotope discrimination, suggesting that the lower carbon isotope discrimination, or higher transpiration efficiency, observed for scrub mangroves in the field is caused only by high salinity during the dry season. Hypersalinity thus seems to be one of the stressful environmental conditions common to all scrub red mangrove forests studied in southern Florida.
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Hussain, M. Iftikhar, and Manuel J. Reigosa. "Seedling growth, leaf water status and signature of stable carbon isotopes in C3 perennials exposed to natural phytochemicals." Australian Journal of Botany 60, no. 8 (2012): 676. http://dx.doi.org/10.1071/bt12072.
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In the present study, we evaluated the seedling growth, water status and signature of stable carbon isotopes in C3 perennial species exposed to natural phytochemicals. Three perennial species, cocksfoot (Dactylis glomerata), perennial ryegrass (Lolium perenne) and common sorrel (Rumex acetosa), were grown for 30 days in perlite, watered with Hoagland solution and exposed to the phytochemicals benzoxazolin-2(3H)-one (BOA) and cinnamic acid (CA) at 0, 0.1, 0.5, 1.0 and 1.5 mM concentrations. BOA markedly decreased the leaf and root fresh weights of D. glomerata and L. perenne in a concentration-dependent manner. The leaf fresh weight (LFW) of plants treated with CA (1.5 mM) was similarly affected by showing a decrease of LFW, being the lowest in L. perenne (56%) followed by D. glomerata (46%). The relative water contents of L. perenne, D. glomerata and R. acetosa were decreased while maximum RWC reduction was observed in L. perenne. Carbon isotope discrimination in L. perenne, D. glomerata and R. acetosa were reduced following treatment with BOA and CA at 1.5 mM. BOA at 1.5 mM decreased the ratio of intercellular to ambient CO2 concentration relative to control in L. perenne, D. glomerata and R. acetosa. There was an increase in water-use efficiency in L. perenne, D. glomerata and R. acetosa after treatment with BOA and CA. The dry weight of plants treated with CA (1.5 mM) showed different patterns of variation, being lowest in L. perenne (33%) followed by D. glomerata (3%) and R. acetosa (2%). Phytotoxicity was higher for the perennial grass than for the perennial broadleaf. These results clearly demonstrate a widespread occurrence of phytotoxicity among the three species, their tolerance and relationship between carbon isotope discrimination and intrinsic water-use efficiency.
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Tcherkez, Guillaume, and Graham D. Farquhar. "On the effect of heavy water (D2O) on carbon isotope fractionation in photosynthesis." Functional Plant Biology 35, no. 3 (2008): 201. http://dx.doi.org/10.1071/fp07282.
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Internal conductance to carbon dioxide is a key aspect of leaf photosynthesis although is still not well understood. It is thought that it comprises two components, namely, a gas phase component (diffusion from intercellular spaces to cell walls) and a liquid phase component (dissolution, diffusion in water, hydration equilibrium). Here we use heavy water (D2O), which is known to slow down CO2 hydration by a factor of nearly three. Using 12C/13C stable isotope techniques and Xanthium strumarium L. leaves, we show that the on-line carbon isotope discrimination (Δ13C, or Δobs) associated with photosynthesis is not significantly decreased by heavy water, and that the internal conductance, estimated with relationships involving the deviation of Δ13C, decreased by 8–40% in 21% O2. It is concluded that in typical conditions, the CO2-hydration equilibrium does not exert an effect on CO2 assimilation larger than 9%. The carbon isotope discrimination associated with CO2 addition to ribulose-1,5,bisphosphate by Rubisco is slightly decreased by heavy water. This effect is proposed to originate from the use of solvent-derived proton/deuteron during the last step of the catalytic cycle of the enzyme (hydration/cleavage).
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Flanagan, Lawrence B., and Kurt H. Johnsen. "Genetic variation in carbon isotope discrimination and its relationship to growth under field conditions in full-sib families of Piceamariana." Canadian Journal of Forest Research 25, no. 1 (January 1, 1995): 39–47. http://dx.doi.org/10.1139/x95-005.
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Measurements of the stable carbon isotope composition of leaf tissue were made on Piceamariana (Mill.) B.S.P trees from four full-sib families grown on three different field sites at the Petawawa National Forestry Institute, Ontario, Canada. The four families chosen exhibited genetic variation for growth characteristics. Genetic variation was also observed for carbon isotopic discrimination (Δ) among the families of P. mariana. In addition, a strong correlation occurred between Δ values measured on trees in 1991 and 1992, two years that had very different precipitation and temperature conditions during the growing season, indicating that the ranking of individual trees remained almost constant between years. A strong, negative correlation was observed between average carbon isotope discrimination and average tree height for the four families on the driest, least productive site, as was expected based on leaf photosynthetic characteristics. There was no significant correlation, however, between Δ values and growth on the other two study sites, where productivity was higher.
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Nowak, M. E., F. Beulig, J. von Fischer, J. Muhr, K. Küsel, and S. E. Trumbore. "Autotrophic fixation of geogenic CO<sub>2</sub> by microorganisms contributes to soil organic matter formation and alters isotope signatures in a wetland mofette." Biogeosciences 12, no. 23 (December 8, 2015): 7169–83. http://dx.doi.org/10.5194/bg-12-7169-2015.
Full textAbstract:
Abstract. To quantify the contribution of autotrophic microorganisms to organic matter (OM) formation in soils, we investigated natural CO2 vents (mofettes) situated in a wetland in northwest Bohemia (Czech Republic). Mofette soils had higher soil organic matter (SOM) concentrations than reference soils due to restricted decomposition under high CO2 levels. We used radiocarbon (Δ14C) and stable carbon (δ13C) isotope ratios to characterize SOM and its sources in two mofettes and compared it with respective reference soils, which were not influenced by geogenic CO2. The geogenic CO2 emitted at these sites is free of radiocarbon and enriched in 13C compared to atmospheric CO2. Together, these isotopic signals allow us to distinguish C fixed by plants from C fixed by autotrophic microorganisms using their differences in 13C discrimination. We can then estimate that up to 27 % of soil organic matter in the 0–10 cm layer of these soils was derived from microbially assimilated CO2. Isotope values of bulk SOM were shifted towards more positive δ13C and more negative Δ14C values in mofettes compared to reference soils, suggesting that geogenic CO2 emitted from the soil atmosphere is incorporated into SOM. To distinguish whether geogenic CO2 was fixed by plants or by CO2 assimilating microorganisms, we first used the proportional differences in radiocarbon and δ13C values to indicate the magnitude of discrimination of the stable isotopes in living plants. Deviation from this relationship was taken to indicate the presence of microbial CO2 fixation, as microbial discrimination should differ from that of plants. 13CO2-labelling experiments confirmed high activity of CO2 assimilating microbes in the top 10 cm, where δ13C values of SOM were shifted up to 2 ‰ towards more negative values. Uptake rates of microbial CO2 fixation ranged up to 1.59 ± 0.16 μg gdw−1 d−1. We inferred that the negative δ13C shift was caused by the activity of autotrophic microorganisms using the Calvin–Benson–Bassham (CBB) cycle, as indicated from quantification of cbbL/cbbM marker genes encoding for RubisCO by quantitative polymerase chain reaction (qPCR) and by acetogenic and methanogenic microorganisms, shown present in the mofettes by previous studies. Combined Δ14C and δ13C isotope mass balances indicated that microbially derived carbon accounted for 8–27 % of bulk SOM in this soil layer. The findings imply that autotrophic microorganisms can recycle significant amounts of carbon in wetland soils and might contribute to observed radiocarbon reservoir effects influencing Δ14C signatures in peat deposits.
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Nowak, M. E., F. Beulig, J. von Fischer, J. Muhr, K. Küsel, and S. E. Trumbore. "Autotrophic fixation of geogenic CO<sub>2</sub> by microorganisms contributes to soil organic matter formation and alters isotope signatures in a wetland mofette." Biogeosciences Discussions 12, no. 17 (September 4, 2015): 14555–92. http://dx.doi.org/10.5194/bgd-12-14555-2015.
Full textAbstract:
Abstract. To quantify the contribution of autotrophic microorganisms to organic matter formation (OM) in soils, we investigated natural CO2 vents (mofettes) situated in a wetland in NW Bohemia (Czech Republic). Mofette soils had higher SOM concentrations than reference soils due to restricted decomposition under high CO2 levels. We used radiocarbon (Δ14C) and stable carbon isotope ratios (δ13C) to characterize SOM and its sources in two moffetes and compared it with respective reference soils, which were not influenced by geogenic CO2. The geogenic CO2 emitted at these sites is free of radiocarbon and enriched in δ13C compared to atmospheric CO2. Together, these isotopic signals allow us to distinguish C fixed by plants from C fixed by autotrophic microorganisms using their differences in δ13C discrimination. We can then estimate that up to 27 % of soil organic matter in the 0–10 cm layer of these soils was derived from microbially assimilated CO2. Isotope values of bulk SOM were shifted towards more positive δ13C and more negative Δ14C values in mofettes compared to reference soils, suggesting that geogenic CO2 emitted from the soil atmosphere is incorporated into SOM. To distinguish whether geogenic CO2 was fixed by plants or by CO2 assimilating microorganisms, we first used the proportional differences in radiocarbon and δ13C values to indicate the magnitude of discrimination of the stable isotopes in living plants. Deviation from this relationship was taken to indicate the presence of microbial CO2 fixation, as microbial discrimination should differ from that of plants. 13CO2-labelling experiments confirmed high activity of CO2 assimilating microbes in the top 10 cm, where δ13C values of SOM were shifted up to 2 ‰ towards more negative values. Uptake rates of microbial CO2 fixation ranged up to 1.59 ± 0.16 μg gdw−1 d−1. We inferred that the negative δ13C shift was caused by the activity of chemo-lithoautotrophic microorganisms, as indicated from quantification of cbbL/cbbM marker genes encoding for RubisCO by quantitative polymerase chain reaction (qPCR) and by acetogenic and methanogenic microorganisms, shown present in the moffettes by previous studies. Combined Δ14C and δ13C isotope mass balances indicated that microbially derived carbon accounted for 8 to 27 % of bulk SOM in this soil layer. The findings imply that autotrophic organisms can recycle significant amounts of carbon in wetland soils and might contribute to observed reservoir effects influencing radiocarbon signatures in peat deposits.