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1.
Summary Stable carbon isotope ratio analysis is a powerful technique in tracing ecosystem carbon flows, especially those between primary and secondary producers. The distinctive 13C/12C ratios of plant species tend to pass along the food chain with little further fractionation, hence the stable carbon isotope composition of an animal is an important clue to what it has eaten. We compared the stable carbon isotope composition of plants and insects in an old field in Georgia. Of the dominant plants in the old field, 6 were C4 species and had 13C1 values of-10.9 to 12.9, and 7 were C3 species with values of-27.3 to-29.1. Insects known to be feeding on only one plant species had 13C values within 1 of the isotopic composition of the plant. Wasp larvae parasitizing two insect species had 13C values 1.3 and 1.7 higher than that of the food plant. A variety of insects of unknown food habits collected on monospecific and mixed species plant stands in the old field had 13C values ranging from-10.1 to-30.0. Two species of leafhopper and a grasshopper had isotopic compositions within the range of C4 plant values; a tortoise beetle and a lace bug had isotopic compositions within C3 plant values. Other insects had intermediate 13C values, suggesting a mixed diet composed of both C3 and C4 plants. The carbon isotopic ratios of field collected insects appears to be a useful qualitative indicator of their feeding preference. 相似文献
2.
Summary Measurements are reported of carbon isotope ratios of Dudleya species growing in natural plant communities. Considerable variation in the 13C values are interpreted as indicating substantial flexibility of the photosynthetic pathways between C3 and CAM. The variability in photosynthetic pathway was in response to genetic factors, stage of plant development, life-form, and environmental conditions. Species active during drought periods have less carbon isotope fractionation than species that are summer-dormant. Summer-active species from drier habitats have less negative 13C values than those from more mesic sites. On the same plant, leaf tissue had more negative 13C values than tissue from the inflorescence. The less negative carbon isotope ratios are indicative of an increased proportion of exogenous CO2 fixed in dark vs light. The ecological significance of these results is discussed.CIW-DPB Publication No. 522 相似文献
3.
Summary Succulent plants representing 16 families and a variety of growth forms originating from winter, summer, and year-round rainfall regimes in southern Africa were analyzed for carbon isotope ratios. Most families had species with 13C values indicative of CAM, particularly those from winter and year-round rainfall regimes. Plants with 13C values intermediate between CAM and C3, indicating flexible photosynthetic pathways, were generally leafy perennials subject to seasonal tissue dehydration. Reproductive tissue tended to have less negative 13C values than vegetative tissue on the same plant, indicating drought-season origin of the former.CIW-DPB Publication No. 609 相似文献
4.
The use of 13C isotope tracer techniques in terrestrial ecology has been restricted by the technical requirements and high costs associated with the production of 13C enriched plant material by 13CO2 release in labelling chambers. We describe a novel, simple and relatively inexpensive method for the small-scale production of 13C and 15N labelled plant material. The method is based on foliar feeding of plants with a urea solution (97 atom% 13C, 2 atom% 15N) by daily misting. Maize was grown in a greenhouse in a compost–soil mixture and enclosed in clear polythene bags between urea applications. Final enrichment in 27 d old maize shoots was 211 13C (1.34 atom% 13C) and 434 15N (0.52 atom% 15N). Enrichments of hot-water extractable fractions (289 13C, 469 15N) were only slightly higher than those observed in plant bulk material, which suggests that daily urea applications ensured fairly uniform labelling of different biochemical fractions and plant tissues. Recovery of applied excess 13C and 15N in plant shoots was 22% and 42%, respectively. Roots were less enriched (21 13C and 277 15N), but no attempts were made to recover roots quantitatively. 相似文献
5.
Bender MM 《Plant physiology》1973,52(5):427-430
13C/12C ratios have been found in totally combusted leaves of Crassulacean acid metabolism plants to range from −14 to −33 δ 13C‰ compared with a limestone standard. Crassulacean acid metabolism plants apparently utilize both ribulose-1, 5-diphosphate carboxylase and phosphoenolpyruvate carboxylase to assimilate atmospheric CO2 and, depending on environmental conditions, have 13C/12C ratios indicative of either carboxylase or to any intermediate value. The degree of discrimination against 13C and the resultant 13C/12C ratio from the photosynthetically fixed CO2 is influenced by environmental conditions and is not a specific and fixed characteristic of a Crassulacean acid metabolism plant. Certain Crassulacean acid metabolism plants may shift their ratios as much as 17 δ 13C‰ in specific environments. 相似文献
6.
Summary Carbon 13/12 isotope ratios have been determined from leaves of a hundred C3 plant species (or ecotypes) from all major mountain ranges of the globe, avoiding drought stressed areas. A general increase in 13C content was found with increasing altitude, i.e. overall discrimination against the heavy isotope is reduced at high elevation. The steepest decline of discrimination is observed in taxa typically ranging to highest elevations (e.g. the genus Ranunculus). Mean 13C for all samples collected between 2500 and 5600 m altitude is-26.15 compared to the lowland average of-28.80 (P<0.001). Forbs from highest elevations reach-24. According to theory of 13C discrimination this indicates decreasing relative limitation of carbon uptake by carboxylation. In other words, we estimate that the ratio of internal to external partial pressure of CO2 (p
i
/p
a
)in leaves of high elevation plants is lower than in leaves of low altitude. These results confirm recent gas exchange analyses in high and low elevation plants. 相似文献
7.
Summary Using natural-abundance 13C/12C ratios as tracers, carbon turnover rates were determined for postlarval brown shrimp, Penaeus aztecus, in five laboratory growth experiments. Although tissue turnover in adult animals generally occurs during maintenance metabolism and is a function of time, turnover for young postlarval shrimp was accelerated during growth, and was primarily a function of weight gained rather than time. Metabolic loss of tissue carbon during growth was usually approximated by the function, Fraction lost=1-(initial weight/final weight). For shrimp that switch diets in the sea, model calculations show that this high turnover rate coupled with a four-fold weight increase suffices for shrimp to achieve a close isotopic resemblance of 1 or less (13C units) to the new diet.In accordance with these predictive calculations, shrimp which had increased in weight by a factor of four or more in the culture experiments showed essentially constant isotopic values reflecting their new diets. For these larger animals, the average animal-diet difference varied across three diets from-0.9 to +11, and the 13C range among individuals was 1.4 in each experiment. 相似文献
8.
Summary Previous studies have shown that plant carbon isotope composition varies when plants experience differences in water and nutrient availability. However, none have addressed the effect of root interactions, including competition for these soil resources, on carbon isotope ratios. We studied the effect of interspecific root interactions on the productivity and carbon isotope ratios of two Great Basin tussock grass species (Agropyron desertorum and Pseudoroegneria spicata). We compared grasses grown in mixture with sagebrush (Artemisia tridentara) to grasses in similar mixtures but where root interactions with sagebrush were limited by fiberglass partitions. During both years of the study, tussocks growing in competition with sagebrush produced tissue with more negative 13C values than grasses experiencing limited root interaction with sagebrush. The magnitude of this difference (0.5 to 0.9%) is similar to that found in other studies when soil fertility and moisture availability were altered. 相似文献
9.
Summary Organic carbon-rich sediments from the surface of fresh, intermediate, brackish and salt marshes of coastal Louisiana were sampled and analyzed for their 13C content. The average 13C from all sites within each wetland type was-27.8,-22.1,-16.9, and-16.2, for fresh, intermediate, brackish and salt marshes, respectively. Means from the fresh, intermediate and brackish marshes were significantly different at the 0.01 level. A mixing model using measurements of standing crop and 13C of plant carbon was applied to estimate the contribution of each species to the sedimentary carbon at four of the marsh sites. Sedimentary 13C values generally reflected that of the dominant species present at each site. Brackish and salt marsh samples, however, showed a negative shift of 13C with respect to whole plant carbon. We interpret these depeleted 13C values to be the result of more extensive organic matter decomposition and selective preservation of 13C-depleted refractory components in sediments from saline sites. The results of this study suggest that 13C composition of sedimentary carbon may offer a valuable tool for distinguishing subtle changes in paleohydrology of wetlands resulting from relative sea level changes. 相似文献
10.
Abstract We measured plant structural and physiological responses of two sympatric Picea species, Picea likiangensis (Franchet) E. Pritzel var. balfouriana and Picea asperata Masters var. retroflexa to altitude close to the treeline in the eastern Himalaya. Most measured tree characteristics differed between different altitudes, between different ages, and between shaded and un-shaded treatments. Both P. likiangensis and P. asperata had lower foliage area/stem cross-sectional area ratios, smaller specific leaf areas, higher root mass/foliage area ratios, and less negative 13C at 3,900 m than at 3,600 m altitude, and in the un-shaded treatment than in the shaded treatment. The 7- and 9-year-old seedlings also showed lower foliage area/stem cross-sectional area ratios, higher root mass/foliage area ratios and less negative 13C than younger seedlings. Shading resulted in an increase of biomass accumulation at all altitudes. A close relationship, independent of altitude, was observed between 13C and specific leaf area, suggesting that internal resistance could limit CO2 diffusion to the site of carboxylation. The results indicate that, in spite of greater water availability, trees at higher altitudes show quite a number of apparent acclimations to drought. 相似文献
11.
Charalampos G. Kalodimos Ioannis P. Gerothanassis Anastasios Troganis Bernard Loock Michel Momenteau 《Journal of biomolecular NMR》1998,11(4):423-435
13C NMR spectra of several carbon monoxide (99.7% 13C and 11.8% 18O enriched) hemoprotein models with varying polar and steric effects of the distal organic superstructure and constraints of the proximal side are reported. This enables the 57Fe-13C(O) coupling constants (
), 13C shieldings ((13C)), and 18O isotope effects on13 C shieldings (113C(18O/16O)) to be measured and hence comparisons with hemoproteins, C-O vibrational frequencies and X-ray structural data to be made. Negative polar interactions in the binding pocket and inhibition of Fe//CO back-donation or positive distal polar interactions with amide NH groups appear to have little direct effect on
couplings. Similarly, the axial hindered base 1,2-dimethylimidazole has a minor effect on the
values despite higher rates of CO desorption being observed for such complexes. On the contrary,13 C shieldings vary widely and an excellent correlation was found between the infrared C-O vibrational frequencies ((C-O)) and13 C shieldings and a reasonable correlation with18 O isotope effects on 13C shieldings. This suggests that (13C), (C-O) and1 13 C(18O/16O) are accurate monitors of the multiple mechanisms by which steric and electronic interactions are released in superstructured heme model compounds. The 13C shieldings of heme models cover a 4.0 ppm range which is extended to 7.0 ppm when several HbCO and MbCO species at different pH values are included. The latter were found to obey a similar linear (13 (13C) versus (C-O) relationship, which proves that both heme models and heme proteins are homogeneous from the structural and electronic viewpoint. Our results suggest that (C-O), (13C) and 113C(18O/16O) measurements reflect similar interaction which is primarily the modulation of back-bonding from the Fe d to the CO * orbital by the distal pocket polar interactions. The lack of correlation between1 13 C(18O/16O) and crystallographic CO bond lengths (r(C-O)) reflects significant uncertainties in the X-ray determination of the carbon and oxygen positions. 相似文献
12.
Takeshi Uozumi Takayuki Hoshino Kiyoshi Miwa Sueharu Horinouchi Teruhiko Beppu Kei Arima 《Molecular & general genetics : MGG》1977,152(1):65-69
Summary Host specific restriction was detected in 13 Bacillus strains, when 63 strains of Bacillus subtilis and 15 other Bacillus strains were tested with phage 105C. These 13 strains were classified into 8 groups (M,H,C,N,E,F,G,P) by the type of restriction. M-type strains (B. subtilis Marburg 168, its derivatives, and two other strains) showed relatively weak restriction, restricting 105C from other groups of Bacillus by ratios of 10-1 to 10-3. Strains of groups H,C,N,E,F,G, and P restricted 105C from other groups by ratios of 10-2 to 10-8. It was confirmed with some of the strains that type-specific modification was endowed only by the last host. Furthermore, we isolated one restriction deficient mutant of B. subtilis marburg 168-YS11, which had also lost its modification phenotype. 相似文献
13.
Jér^ome Boisbouvier Bernhard Brutscher Jean-Pierre Simorre Dominique Marion 《Journal of biomolecular NMR》1999,14(3):241-252
A set of new NMR pulse sequences has been designed for the measurement of 13C relaxation rate constants in RNA and DNA bases: the spin-lattice relaxation rate constant R(Cz), the spin-spin relaxation rate constant R(C+), and the CSA-dipolar cross-correlated relaxation rate constant
. The use of spin-state selective correlation techniques provides increased sensitivity and spectral resolution. Sensitivity optimised C-C filters are included in the pulse schemes for the suppression of signals originating from undesired carbon isotopomers. The experiments are applied to a 15% 13C-labelled 33-mer RNA–theophylline complex. The measured
ratios indicate that 13C CSA tensors do not vary significantly for the same type of carbon (C2, C6, C8), but that they differ from one type to another. In addition, conformational exchange effects in the RNA bases are detected as a change in the relaxation decay of the narrow 13C doublet component when varying the spacing of a CPMG pulse train. This new approach allows the detection of small exchange effects with a higher precision compared to conventional techniques. 相似文献
14.
The possibility of ecosystem boundary changes in northern Brazilian Amazonia during the Holocene period was investigated using soil organic carbon isotope ratios. Determination of past and present fluctuations of the forest-savanna boundary involved the measurement of natural 13C isotope abundance, expressed as 13C, in soil organic matter (SOM). SOM 13C analyses and radiocarbon dating of charcoal fragments were carried out on samples derived from soil profiles taken along transects perpendicular to the ecotonal boundary. SOM 13C values in the upper soil horizons appeared to be in equilibrium with the overlying vegetation types and did not point to a movement of the boundary during the last decades. However, 13C values obtained from deeper savanna and forest soil layers indicated that the vegetation type has changed in the past. In current savanna soil profiles, we observed the presence of mid-Holocene charcoals derived from forest species: fire frequency at that time was probably greater, and more extensive savanna may have resulted. Isotope data and the presence of these charcoals thus suggest that the forest-savanna boundary has shifted significantly in the recent Holocene period, forest being more extensive during the early Holocene than today. During the middle Holocene, the forest could have strongly regressed, and fires appeared, with a maximum development of the savanna vegetation. At the beginning of the late Holocene, the forest may have invaded a part of this savanna, and fires occurred again. 相似文献
15.
Rotational diffusion properties have been derived for the DNA dodecamer d(CGCGAATTCGCG)2 from 13C R1 and R1 measurements on the C1, C3, and C4 carbons in samples uniformly enriched in 13C. The narrow range of C-H bond vector orientations relative to the DNA axis make the analysis particularly sensitive to small structural deviations. As a result, the R1/R1 ratios are found to fit poorly to the crystal structures of this dodecamer, but well to a recent solution NMR structure, determined in liquid crystalline media, even though globally the structures are quite similar. A fit of the R1/R1 ratios to the solution structure is optimal for an axially symmetric rotational diffusion model, with a diffusion anisotropy, D||/D, of 2.1±0.4, and an overall rotational correlation time, (2D||+4D)–1, of 3.35 ns at 35 °C in D2O, in excellent agreement with values obtained from hydrodynamic modeling. 相似文献
16.
M.R. Abney C.E. Sorenson F. Gould & J.R. Bradley Jr. 《Entomologia Experimentalis et Applicata》2008,126(1):46-52
Differences in the stable carbon isotope ratios of plants utilizing the C3 vs. C4 photosynthetic pathway have been used to broadly identify the natal host origins of herbivorous insects. This study explored whether adequate variation exists between the carbon isotope ratios of different C3 plants in the host range of Heliothis virescens (Fabricius) (Lepidoptera: Noctuidae) to enable accurate identification of natal host‐plant species. Isotope ratio mass spectrometry (IRMS) analysis of 13C/12C ratios of moths reared on four crop plant species [Gossypium hirsutum (L.), Nicotiana tabacum L., Glycine max (L.) Merrill, and Arachis hypogaea L.] and two common weed species [Geranium carolinianum L. and Linaria canadensis (L.) Chaz.] revealed a range of δ13C values within that expected for plants utilizing the C3 photosynthetic pathway. Analysis of vegetative and reproductive tissues from the plants utilized in the study resulted in statistically different δ13C values for some plant species; nevertheless, the range of δ13C values observed for many plant species overlapped. Significant differences in mean δ13C values were detected between groups of moths reared on different host‐plant species, but there was no significant correlation between the δ13C values of moths vs. the δ13C value of plant tissue on which they were reared. Feral tobacco budworm moths collected over 3 years were found to have carbon isotope ratios consistent with those having fed on C3 plants, confirming little utilization of C4 plant species by the insect. Results demonstrate that within the range of C3 host plants tested, carbon isotope signatures are not sufficiently unique to enable a reliable determination of natal origin of feral tobacco budworm with current IRMS technology. 相似文献
17.
Fujita K Ye LH Sato M Okagaki T Nagamachi Y Kohama K 《Molecular and cellular biochemistry》1999,202(1-2):85-90
Investigations with protein kinase C (PKC) isoform-specific antisera, revealed distinct profiles of PKC isoform content amongst pituitary tissues. Western analysis revealed the and isoforms of PKC are present in rat anterior and posterior pituitary tissue as well as in the GH3 somatomammotrophic cell line. AtT-20/D16-V corticotrophic and T3-1 gonadotrophic murine cell lines contained no PKC-. The or isoforms were undetected in any pituitary tissue. PKC activity measurements revealed Ca2+-independent PKCs in T3-1 and GH3 cells which were more sensitive to activation by phorbol-dibutyrate (PDBu) than the corresponding PKC activity found in COS cells. However, Ca2+-dependent PKC activities were of similar sensitivity to PDBu in GH3, T3-1 and COS cells, indicating that functional differences observed in PDBu-sensitivity in these cells may be due to differential activation of Ca2+-independent PKC isoforms. Moreover, substrate-specificity of these PKCs were also compared indicating that the amount of Ca2+-dependency of the observed PKC activity from the same pituitary tissue is dependent upon the substrate utilized by the PKC isotypes present. These findings explain differential sensitivities of PKC-mediated actions that have previously been observed in a range of pituitary cells. (Mol Cell Biochem 000-000, 1999) 相似文献
18.
Stable carbon and nitrogen isotope ratios were used to posit the relative importance of microbial processes on energy pathways in an ephemeral, humic boreal wetland compared to four clearwater lakes in northwestern Ontario, Canada. In addition to algae and dipteran larvae, odonate larvae were sampled as these latter organisms are known to predate indiscriminately on smaller invertebrates and are thus likely to have average isotope ratios reflective of their habitats. Similarities in 13C and 15N values between lake insect larvae and emerged adults suggested that littoral foodwebs in these oligotrophic lakes may rely to a considerable degree upon terrestrial carbon. Wetland insect larvae and algae were depleted in both 13C and 15N compared to biota in lakes. Carbon isotope analysis implied a substantial presence of microbial respiration from decomposition in the humic wetland, whereas nitrogen isotope analysis suggested the prevalence of microbially modified nitrogen dynamics, including the possibilty of N-fixation. 相似文献
19.
van Gammeren AJ Hulsbergen FB Hollander JG de Groot HJ 《Journal of biomolecular NMR》2004,30(3):267-274
Partly biosynthetic site-directed isotopically 13C enriched photosynthetic light-harvesting 2(LH2) complexes have been prepared from Rhodopseudomonas acidophila strain 10050 by using chemically labeled [1,2,3,4–13C], [1,4–13C] and [2,3–13C] succinic acid as a precursor in the growth medium. Two-dimensional proton driven spin diffusion (PDSD) solid state NMR correlation spectroscopy has been used to trace each individual 13C isotope from the labeled succinic acid precursor to its destination into the protein and into the embedded major light-absorbing bacteriochlorophyll cofactors. For both the residues of the protein and for the cofactors distinct labeling patterns have been deduced, for protein complexes prepared from [1,4–13C]-succinic acid or [2,3–13C]-succinic labeled media. All residues, except isoleucine and leucine, have been labeled almost homogeneously by the succinic acid precursor. Carbonyl carbons in the protein backbone were labeled by [1,4–13C]-succinic acid, while the C and C carbons of the residues were labeled by [2,3 13C]-succinic acid. Leucine and isoleucine residues were labeled using a uniformly labeled amino acid mixture in the medium. The pattern labeling yields an increase of the resolution and less spectral crowding. The partial labeling technique in combination with conventional solid state NMR methods at ultra high magnetic fields provides an attractive route to resolve chemical shifts for -helical transmembrane protein structures. 相似文献
20.
Factors influencing the stable carbon and oxygen isotopic composition ofPorites lutea coral skeletons from Phuket,South Thailand 总被引:1,自引:0,他引:1
We determined the 18O and 13C composition of the same fixed growth increment in severalPorites lutea coral skeletons from Phuket, South Thailand. Skeletal growth rate and 18O are inversely related. We explain this in terms of McConnaughey's kinetic isotopic disequilibria model. Annual trends in 18O cannot be solely explained by observed variations in seawater temperature or salinity and may also reflect seasonal variations in calcification rate. Coral tissue chlorophylla content and 13C of the underlying 1 mm of skeleton are positively related, suggesting that algal modification of the dissolved inorganic carbonate pool is the main control on skeletal 13C. However, in corals that bleached during a period of exceptionally high seawater temperatures in the summer of 1991, 13C of the outer 1 mm of skeleton and skeletal growth rate (over 9 months up to and including the bleaching event) are inversely related. Seasonal variations in °13C may reflect variations in calcification rate, zooxanthellae photosynthesis or in seawater 13C composition. Bleached corals had reduced calcification over the 9-month period up to and including the bleaching event and over the event they deposited carbonate enriched in13C and18O compared with unaffected corals. However, calcification during the event was limited and insufficient material was deposited to influence significantly the isotopic signature of the larger seasonal profile samples. In profile, overall decreases in 18O and 13C were observed, supporting evidence that positive temperature anomalies caused the bleaching event and reflecting the loss of zooxanthellae photosynthesis. 相似文献