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1.
We show that an animal's past and present diet can be distinguished through the delta(13)C of exhaled CO(2). The exhaled delta(13)C of 12 pigeons fed solely corn (a C(4) plant) for 30 days was -13.63 per thousand (+/-0.30). We then fed six pigeons wheat (a C(3) plant) and continued to feed the other six corn. After 48 h the exhaled delta(13)C from the corn-fed pigeons was unchanged; that from the wheat-fed pigeons was -20.5 per thousand. We then fasted three of the wheat-fed pigeons for 3 days, after which their exhaled delta(13)C was -14.96 per thousand, while it was -13.57 per thousand in corn-fed pigeons, and -22.22 per thousand in pigeons that continued on wheat. Thus, we could infer diet from the (13)C/(12)C ratios of exhaled CO(2). Significantly, breath samples from fasted pigeons also revealed that they had eaten corn when their lipid stores were formed. We also showed that the change in the (13)C/(12)C of exhaled CO(2) had a half-life of approximately 3.5 h, and a time constant of approximately 6.7 h. Thus one can infer past and present diet from exhaled delta(13)C alone, if the initial breath sample is followed by a fasted breath sample, without harming the animal or having to recapture it successively.  相似文献   

2.
Shoots of intact peanut and sunflower seedlings evolved CO2in the light which was enriched more than 10 per mille in 13Ccompared with simultaneous CO2 evolution from the roots. Carbondioxide collected from tobacco leaves in the light was 10 permille enriched in 13C compared with that collected in the dark.Anaerobic conditions inhibited photorespiration but did notchange isotopic ratios of dark respiration. 1 Department of Biology, Fresno State College, Fresno, California93710, U. S. A. 2 Deceased. (Received February 29, 1972; )  相似文献   

3.
During the first month after germination peanut and sunflowerseedlings exhibit a significant shift in the 13C/12C ratiosof respired CO2 indicating thatcarbohydrate gives way to lipidas the respiratory substrate. Other species (castor bean, corn,pea,radish, squash and wheat) show no change in the 13C/12C ratio (Received March 9, 1971; )  相似文献   

4.
Three sets of comparisons of net and gross inorganic carbonassimilation and 14C uptake were made with an axenic cultureof Skdetonema costatum. The comparisons showed that in the physiologicalwindow studied (10–20% of the intrinsic generation timeand gross photosynthesis/respiration ratios of 2–3), 14Cuptake into the paniculate plus the dissolved fractions approximatedto net photosynthesis. Rate constants derived from the chemicallydetermined changes were used to parameterize models that accountedfor the respiration of photosynthetic products and for the recyclingof respiratory CO14. The conclusion drawn was that over thetime scale studied, the 14C technique was measuring net photosynthesis,consistent with essentially 100% recycling of respiratory CO2.The study has shown that we now possess the basis to make arigorous analysis of net, gross CC4 fixation and net 14C uptake,and forms the first step in the development of algorithms forthe interpretation of 14C field observations.  相似文献   

5.
In a study on metabolic consumption of photosynthetic electronsand dissipation of excess light energy under water stress, O2and CO2 gas exchange was measured by mass spectrometry in tomatoplants using 18O2 and 13CO2. Under water stress, gross O2 evolution(EO), gross O2 uptake (UO), net CO2 uptake (PN), gross CO2 uptake(TPS), and gross CO2 evolution (EC) declined. The ratio PN/EOfell during stress, while the ratios UO/EO and EC/TPS rose.Mitochondrial respiration in the light, which can be measureddirectly by 12CO2 evolution during 13CO2 uptake at 3000 µll–1 13CO2, is small in relation to gross CO2 evolutionand CO2 release from the glycolate pathway. It is concludedthat PSII, the Calvin cycle and mitochondrial respiration aredown-regulated under water stress. The percentages of photosyntheticelectrons dissipated by CO2 assimilation, photorespiration andthe Mehler reaction were calculated: in control leaves morethan 50 % of the electrons were consumed in CO2 assimilation,23 % in photorespiration and 13 % in the Mehler reaction. Undersevere stress the percentages of electrons dissipated by CO2assimilation and the Mehler reaction declined while the percentageof electrons used in photorespiration doubled. The consumptionof electrons in photorespiration may reduce the likelihood ofdamage during water deficit.  相似文献   

6.
KOUCHI  H.; YONEYAMA  T. 《Annals of botany》1984,53(6):875-882
A long-term, steady-state 13CO2 assimilation system at a constantCO2 concentration with a constant 13C abundance was designedand applied to quantitative investigations on the allocationof photoassimilated carbon in nodulated soya bean (Glycine maxL.) plants. The CO2 concentration in the assimilation chamberand its 13C abundance were maintained constant with relativevariances of less than ±0.5 per cent during an 8-h assimilationperiod. At the termination of 8-h 13CO2 assimilation by plantsat early flowering stage, the currently assimilated carbon relativeto total tissue carbon (measured by the degree of isotopic saturation)were for young leaves (including flower buds), 13.9 per cent;mature leaves, 15.7 per cent; stems+petioles, 5.9 per cent;roots, 5.4 per cent and nodules, 6.9 per cent, 48 h after theend of the 13CO2 assimilation period, they were 12.3, 7.5, 7.4,6.8 and 6.1 per cent, respectively. The treatment with a highconcentration of nitrate in the nutrient media significantlydecreased the allocation of 13C into nodules. Experiments on13CO2 assimilation by plants at the pod-filling stage were alsoconducted. Labelling by 13C was weaker than at the early floweringstage, but an intense accumulation of 13C into reproductiveorgans was observed. Glycine max L., nodulated soya bean plants, 13CO2 assimilation, carbon dynamics  相似文献   

7.
Well-nodulated soya bean (Glycine max L.) plants were allowedto assimilate 13CO2 for 10 h in the light, under steady-stateconditions in which CO2 concentration and 13C abundance wereboth strictly controlled at constant levels. The respiratoryevolution of 13CO2 from roots and nodules and 13C incorporationinto various metabolic fractions were measured during the 13CO2feeding and subsequent 48 h chase period. CO2 respired from nodules was much more rapidly labelled with13C than that from roots. The level of labelling (percentageof carbon currently assimilated during the 13COM2 feeding period)of CO2 respired from nodules reached a maximum of about 87 percent after 4 h of steady-state l3CO2 assimilation and thereafterremained fairly constant. The absolute amount of labelled carbonevolved by the respiration of the nodules during the 10 h 13CO2feeding period was 1·5-fold that of root respiration.These results demonstrated that the currently assimilated (labelled)carbon was preferentially used to support nodule respiration,while root respiration relied considerably on earlier (non-labelled)carbon reserved in the roots. Sucrose pools were mostly composed of currently assimilatedcarbon in all tissues of the plants, since the levels of labellingaccounted for 86–91 per cent at the end of the 13CO2 feeding.In the nodules, the kinetics and levels of sucrose labellingwere in fairly good agreement with those of respired CO2, whilein the roots, the level of labelling of respired CO2 was significantlylower than that of sucrose. Succinate and malate were highly labelled in both roots andnodules but they were labelled much more slowly than sucroseand respired CO2. The kinetics and levels of labelling of theseKrebs cycle intermediates resembled those of major amino acidswhich are derived directly from Krebs cycle intermediates. Itis suggested that large fractions of organic acids in noduleswere physically separate from the respiration site. Glycine max L., Soya bean, 13CO2 assimilation, respiratory evolution of 13CO2, carbon metabolism in root nodules  相似文献   

8.
We hypothesized that changes in plant growth resulting from atmospheric CO2 and O3 enrichment would alter the flow of C through soil food webs and that this effect would vary with tree species. To test this idea, we traced the course of C through the soil microbial community using soils from the free-air CO2 and O3 enrichment site in Rhinelander, Wisconsin. We added either 13C-labeled cellobiose or 13C-labeled N-acetylglucosamine to soils collected beneath ecologically distinct temperate trees exposed for 3 years to factorial CO2 (ambient and 200 µl l-1 above ambient) and O3 (ambient and 20 µl l-1 above ambient) treatments. For both labeled substrates, recovery of 13C in microbial respiration increased beneath plants grown under elevated CO2 by 29% compared to ambient; elevated O3 eliminated this effect. Production of 13C-CO2 from soils beneath aspen (Populus tremuloides Michx.) and aspen-birch (Betula papyrifera Marsh.) was greater than that beneath aspen-maple (Acer saccharum Marsh.). Phospholipid fatty acid analyses (13C-PLFAs) indicated that the microbial community beneath plants exposed to elevated CO2 metabolized more 13C-cellobiose, compared to the microbial community beneath plants exposed to the ambient condition. Recovery of 13C in PLFAs was an order of magnitude greater for N-acetylglucosamine-amended soil compared to cellobiose-amended soil, indicating that substrate type influenced microbial metabolism and soil C cycling. We found that elevated CO2 increased fungal activity and microbial metabolism of cellobiose, and that microbial processes under early-successional aspen and birch species were more strongly affected by CO2 and O3 enrichment than those under late-successional maple.  相似文献   

9.
The effect of exposure of kidney bean primary leaves to NO2and O3, alone or in combination, on the fate of 13CO2 assimilatedby photosynthesis was examined by 13C-NMR. There were more than70 peaks appearing in the 13C-NMR spectra for substances extractedfrom leaves with 80% ethanol. The 16 relatively well resolvedpeaks corresponded to signals from three sugars, two organicacids and four amino acids. These signals were used to estimatepool sizes and l3C incorporation. Exposures to NO2 and O3 increased the amounts of sucrose andfructose, but not the incorporation of the 13C label during10 min photosynthesis from 13CO2. This suggests the presenceof photo-synthetically inactive pools of sucrose and fructose.Amounts of glycine and serine, and 13C incorporation into them,were increased by the exposure to the pollutants. The incorporationof 13C into alanine was stimulated by exposure to NO2, but notby exposure to O3 alone. The present study shows that with only simple procedures ofsample preparations 13C-NMR provides information on the productsof photosynthesis in leaves stressed by the two air pollutants. Key words: NO2, O3, Phaseolus vulgaris, CO2 assimilation, 13C-NMR  相似文献   

10.
Haloxylon aphyllum and H. persicum of Chenopodiaceae are dominantplants in the continental deserts of the Asian Irano-Turanianregion. The photosynthetic organs, assimilating shoots and leaf-likecotyledons of these two species were studied to characterizetheir photosynthetic types. 13C/12C isotope ratios, the cellularanatomy of as similating organs, primary photosynthetic products,and activities of carbon metabolism enzymes, RUBP carboxylase,PEP carboxylase, malic enzymes, and aspartate aminotransferase,indicate different pathways of CO2 fixation in the photosyntheticorgans. Assimilating shoots had attributes of the C4 photosynthesisentirely, while cotyledons lack Kranz-anatomy and incorporatedCO2 via C3 photosynthesis. Cotyledons and seeds had lower  相似文献   

11.
Refixation of respiratory CO2 in the ears of C3 cereals   总被引:6,自引:0,他引:6  
The spatial arrangement of tissues within the ears of cereals,and gas exchange measurements on intact ears of barley and durumwheat suggest that respiratory CO2 associated with grain-fillingprocesses, may be refixed close to its site of evolution. Apparentrefixation of respiratory CO2 in intact ears was compared withthat in flag leaves, by feeding both organs with 14C-labelledsucrose and trapping 14CO2 released by respiration. Apparentrefixation in the ears was twice that measured in flag leafblades of durum wheat genotype Durelle. In ears, the capacityof refixation of respiratory CO2 at 210 mmol mol–1 O2ranged from 55% in barley genotype Roxana to 75% in barley genotypeHatif, and 60% in duwm wheat genotype Bidi 17. A low O2 concentrationincreased refixation of respiratory CO2 by up to 90%, 92% and82%, respectively. The occurrence of CO2 refixation in the field,in a set of 12 barley genotypes grown under irrigated and rainfedMediterranean field conditions, was consistent with observedcarbon isotope ratios (  相似文献   

12.
The stomatal characteristics, length and dry weight as well as stable carbon isotope composition (i13C) of needles and tree rings of Qinghai spruce (Picea crassifolia) at different altitudes in the Qilian mountains were investigated. The results showed that stomatal density, distribution pattern on epidermis, and length and dry weight of needles all increased with altitude below 3,000 m. In contrast, these parameters all decreased with increasing altitude above 3,000 m. Furthermore an assay of tree rings showed that near 3,000 m in altitude was the optimum zone for growth and development of Qinghai spruce. Although atmospheric CO2 concentration influences stomatal density, the effects of many environmental factors, such as temperature, light and rainfall, could obscure the effects of changes in atmospheric CO2 concentration on stomatal density at altitudes higher than the optimum for growth. The correlation of stomatal density with atmospheric CO2 concentration and i13C of Qinghai spruce needles was significant below 3,000 m, but was insignificant above 3,000 m altitude. The i13C value of needles, however, was negatively correlated with atmospheric CO2 concentrations. Therefore, the influence of altitude should be considered in research on plant physiological ecology and the relationship of stomatal density with i13C value or atmospheric CO2 concentration.  相似文献   

13.
A. Ekblad  P. H?gberg 《Oecologia》2001,127(3):305-308
Soil respiration from a boreal mixed coniferous forest showed large seasonal variation in natural abundance of 13C, ranging from -21.6‰ to -26.5‰. We tested if weather conditions could explain this variation in '13C of respired CO2, and found that the air relative humidity 1-4 days before the days of CO2 sampling best explained the variation. This suggested that high '13C values were caused by effects of air humidity on isotope fractionation during photosynthesis and that it took 1-4 days for the C from canopy photosynthesis of 20-25 m trees to become available for root/rhizosphere respiration. We calculated that these new photoassimilates could account for at least 65% of total soil respiration.  相似文献   

14.
Dark fixation of 14CO2 was followed in potato disks under varyingsalt treatments at 0° C and 25° C. It is shown thatthe specific activity of the 14CO2 supplied is heavily dilutedby endogenously produced CO2 and that the apparently greaterfixation of 14CO2, at 0° C as compared with that at 25 °C is due to the lower respiration rate at 0° C, with consequentlyless dilution of the 14CO2. supplied. At 25° C organic acidformation in response to different salt treatments fulfils thecommon expectation, 14CO2 fixation increasing in the presenceof K2SO4 and decreasing in CaCl2 relative to that in KCl. Therole of organic acids in maintaining ionic balance within thecell at 25° C is thereby indicated but at 0° C organicacid adjustments did not follow the normal pattern. At 25°C but not at o° C increasing external concentration of KCIresulted in an increased level of 14CO2 fixation.  相似文献   

15.
The initial products of 14CO2 assimilation were determined understeady state illumination of leaves of Flaveria trinervia, aC4 dicot of the NADP-mialic enzyme subgroup. Leaf age influencedthe partitioning of 14CO2 between the C4 cycle and the reductivepentose phosphate (RPP) pathway. An estimated 10 to 12%of theCO2 entered the RPP pathway directly in leaves about 20% fullyexpanded, whereas CO2 was apparently fixed entirely throughthe C4 pathway in leaves 75% or more expanded. This partitioningpattern was attributed to the bundle sheath compartment in youngleaves having a relatively high conductance to CO2 (i.e., beingsomewhat leaky). Of the initially labelled C4 acids, the proportion that wasmalate, relative to aspartate, increased continuously duringleaf expansion (from 60 : 40 to 87 : 13 at full expansion).Concurrently, there was an increase in the whole leaf activityof NADP malate dehydrogenase and a decrease in the activitiesof aspartate and alanine aminotransferases. Low chlorophylla/b values were observed in young leaves, which may coincidewith an enhanced capacity for non-cyclic electron transportin the bundle sheath chloroplasts of such tissue. Both enhancedaspartate metabolism and direct fixation of CO2 in the bundlesheath could provide a greater sink for utilization of photochemicallyderived NADPH in the bundle sheath of young leaves. Such metabolicchanges are discussed in relation to a possible decrease inCO2 conductance of the bundle sheath during leaf development. (Received March 4, 1986; Accepted June 25, 1986)  相似文献   

16.
A study was made of the incorporation of 14C by intact leavesof Coffea arabica (cultivars Mundo Novo, Catuai, 1130–13,and H 6586–2) and Coffea canephora (cultivar Guarini)supplied with gas mixtures containing 14CO2 under controlledconditions. Samples of the leaves were combusted and the 14Cin the CO2 produced measured using a liquid scintillation counter.The results were used to estimate photosynthetic rates. Theeffects of changing the partial pressures of O2 and CO2 on thephotosynthetic rate were studied and estimates made of the CO2compensation point and photorespiration. The data obtained show differences between the mean net photosyntheticrates of the C. arabica cultivars (6·14 mg CO2 dm–2h–1) and the mean rate for the C. canephora cultivar (3·96mg CO2 dm–2 h–1). The cultivar of the latter speciesphotorespired more rapidly than the cultivar Catuai of C. arabica.Rates of photosynthesis in coffee measured using the 14CO2 methodwere similar to rates obtained by others using an infrared gasanalyser. The 14CO2 method proved to be reliable for photosyntheticmeasurements and the apparatus is suitable for use in fieldconditions.  相似文献   

17.
Kouchi, H., Akao, S. and Yoneyama, T. 1986. Respiratory utilizationof 13C-labelled photosynthate in nodulated root systems of soybeanplants.—J. exp. Bot. 37: 985–993. An improved method for the measurement of respiratory utilizationof current photosynthate in the nodulated root system of water-culturedsoybean (Glycine max L.) plants was developed using a steady-state13CO2 labelling technique. Well-nodulated plants at the latevegetative stage were allowed to assimilate 13CO2 for 10 h incontinuous light at a constant CO2 concentration with a constant13C abundance. The respiratory evolution of 13CO2 from rootsand nodules was measured continuously throughout the periodof 13CO2 assimilation and during a subsequent 36 h chase periodby using a differential infrared 13CO2 analyser. The plantswere grown with nitrogen-free or (15 mmol dm–3)-containing culture solution for 3 d before13CO2 assimilation. In plants grown without , nodule respiration averaged 69% of the total respiration of the undergroundparts over the full experimental period and the CO2 respiredreached an apparent isotopic equilibrium at 80–85% labellingafter initiating 13CO2 assimilation. By contrast, the CO2 respiredfrom the roots did not reach an isotopic equilibrium and labellingwas only 56% at the end of exposure to 13CO2 These findingsdemonstrated that nodule respiration is strongly dependent onrecently assimilated carbon compared with root respiration. Plants supplied with in the culture solution showed a decreased rate of nodule respirationand a slightly increased rate of root respiration. The extentsand time courses of labelling of respired CO2 from both theroots and nodules were similar in the presence and absence of except that the maximum level of labelling of CO2 derived from nodule respiration in plantswith was significantly higher (about 91%) than for plants growing without . Key words: Soybean (Glycine max L.), nodule respiration, 13CO2, assimilation, carbon partitioning  相似文献   

18.
KOUCHI  H.; YONEYAMA  T. 《Annals of botany》1984,53(6):883-896
Nodulated soya bean (Glycine max L.) plants at the early floweringstage were allowed to assimilate 13CO2 under steady-state conditions,with a constant 13C abundance, for 8 h in the light. The plantswere either harvested immediately or 2 d after the end of the13CO2 feeding, divided into young leaves (including flower buds),mature leaves, stems+petioles, roots and nodules; the 13C abundancein soluble carbohydrates, organic acids, amino acids, starchand poly-ß-hydroxybutyric acid was determined witha gas chromatography-mass spectrometry. The rapid turnover of 13C in the sucrose pools observed in allorgans of the plants showed that sucrose was the principal materialin the translocation stream of primary products of photosynthesis.At the end of the 13CO2 exposure, sucrose in the mature leavesas the major source organs and in the stems+petioles was labelledwith currently assimilated carbon to about 75 per cent, whereasa much higher labelling of sucrose was found in the roots andin the nodules. This suggests the existence of two or more compartmentedpools of sucrose in mature leaves and also in stems+petioles. The relative labelling patterns of individual organic acidsand amino acids were similar in various plant organs. However,the rapid turnover of succinate and glycine was characteristicof nodules. Treatment with a high concentration of nitrate inthe nutrient media increased the turnover rate of amino acidcarbon in shoot organs and roots, while it markedly decreasedthe labelling of amino acids in nodules. The cyclitols, exceptfor D-pinitol, were significantly labelled with assimilated13C in mature leaves, but in nodules, the labelling was verymuch less. In the nodules, which were actively fixing atmospheric nitrogen,a large proportion (80–90 per cent) of currently assimilatedcarbon was found as sucrose and starch at the end of the 13CO2feeding. This was also true of the roots. On the other hand,in young growing leaves, the distribution of currently assimilatedcarbon into sucrose, starch and other soluble compounds wasmuch less. This suggests that a large amount of carbon assimilatedby and translocated to young leaves was used to make up structuralmaterials, mainly protein and cell wall polymers synthesis,during the light period. Glycine max L., soya bean, 13CO2 assimilation, carbon metabolism in nodules  相似文献   

19.
This study investigated how CO2and temperature affect dry weight(d.wt) accumulation, total nonstructural carbohydrate (TNC)concentration, and partitioning of C and N among organs of twoimportant grasses of the shortgrass steppe,Pascopyrum smithiiRydb. (C3) andBouteloua gracilis(H.B.K.) Lag. ex Steud. (C4).Treatment combinations comprised two temperatures (20 and 35°C)at two concentrations of CO2(380 and 750 µmol mol-1),and two additional temperatures of 25 and 30°C at 750 µmolmol-1CO2. Plants were maintained under favourable nutrient andsoil moisture and harvested following 21, 35, and 49d of treatment.CO2-induced growth enhancements were greatest at temperaturesconsidered favourable for growth of these grasses. Comparedto growth at 380 µmol mol-1CO2, final d.wt of CO2-enrichedP.smithiiincreased 84% at 20°C, but only 4% at 35°C. Finald.wt ofB. graciliswas unaffected by CO2at 20°C, but wasenhanced by 28% at 35°C. Root:shoot ratios remained relativelyconstant across CO2levels, but increased inP. smithiiwith reductionin temperature. These partitioning results were adequately explainedby the theory of balanced root and shoot activity. Favourablegrowth temperatures led to CO2-induced accumulations of TNCin leaves of both species, and in stems ofP. smithii, whichgenerally reflected responses of above-ground d.wt partitioningto CO2. However, CO2-induced decreases in plant tissue N concentrationswere more evident forP. smithii. Roots of CO2-enrichedP. smithiihadgreater total N content at 20°C, an allocation of N below-groundthat may be an especially important adaptation for C3plants.Tissue N contents ofB. graciliswere unaffected by CO2. Resultssuggest CO2enrichment may lead to reduced N requirements forgrowth in C3plants and lower shoot N concentration, especiallyat favourable growth temperatures. Acclimation to CO2; blue grama; Bouteloua gracilis ; carbohydrate; climate change; global change; grass; growth; growth temperature optima; nitrogen; N uptake; Pascopyrum smithii; western wheatgrass  相似文献   

20.
Single, seed-grown plants of ryegrass (Lolium perenne L. cv.Melle) were grown for 49 d from the early seedling stage ingrowth cabinets at a day/night temperature of 20/15 C, witha 12 h photoperiod, and a CO2 concentration of either 340 or680µI 1–1 CO2. Following complete acclimation tothe environmental regimes, leaf and whole plant CO2 effluxesand influxes were measured using infra-red gas analysis techniques.Elevated CO2 increased rates of photosynthesis of young, fullyexpanded leaves by 35–46% and of whole plants by morethan 50%. For both leaves and whole plants acclimation to 680µI–1 CO2 reduced rates of photosynthesis in bothCO2 regimes, compared with plants acclimated to 340µll–1. There was no significant effect of CO2 regime onrespiration rates of either leaves or whole plants, althoughleaves developed in elevated CO2 exhibited generally lower ratesthan those developed in 340µI I–1 CO2. Initially the seedling plants in elevated CO2 grew faster thantheir counterparts in 340µI I–1 CO2, but this effectquickly petered out and final plant weights differed by onlyc. 10%. Since the total area of expanded and unexpanded laminaewas unaffected by CO2 regime, specific leaf area was persistently13–40% lower in elevated CO2 while, similarly, root/shootratio was also reduced throughout the experiment. Elevated CO2reduced tissue nitrogen contents of expanded leaves, but hadno effect on the nitrogen contents of unexpanded leaves, sheathsor roots. The lack of a pronounced effect of elevated CO2 on plant growthwas primarily due to the fact that CO2 concentration did notinfluence tiller (branch) numbers. In the absence of an effecton tiller numbers, any possible weight increment was restrictedto the c. 2.5 leaves of each tiller. The reason for the lackof an effect on tillering is not known. Key words: Lolium perenne, ryegrass, elevated CO2, photosynthesis, respiration, growth, development  相似文献   

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