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61.
NMR imaging of root water distribution in intact Vicia faba L plants in elevated atmospheric CO2 总被引:1,自引:1,他引:0
The effect of elevated atmospheric CO2 on water distribution in the intact roots of Vicia faba L. bean seedlings grown in natural soil was studied noninvasively with proton (1H) nuclear magnetic resonance (NMR) imaging. Exposure of 24-d-old plants to atmospheric CO2-enriched air at 650 cm3 m?3 produced significant increases in water imaged in upper roots, hypogeal cotyledons and lower stems in response to a short-term drying-stress cycle. Above ground, drying produced negligible stem shrinkage and stomatal resistance was unchanged. In contrast, the same drying cycle caused significant depletion of water imaged in the same upper root structures in control plants subject to ambient CO2 (350 m3 m?3), and stem shrinkage and increased stomatal resistance. The results suggest that inhibition of transpiration caused by elevated CO2 does not necessarily result in attenuation of water transport from lower root structures. Inhibition of water loss from upper roots and lower stem in elevated CO2 environments may be a mitigating factor in assessing deleterious effects of greenhouse changes on crops during periods of dry climate. 相似文献
62.
Natural CO2 springs in Italy: a resource for examining long-term response of vegetation to rising atmospheric CO2 concentrations 总被引:2,自引:1,他引:1
It is estimated that more than 100 geothermal CO2 springs exist in central-western Italy. Eight springs were selected in which the atmospheric CO2 concentrations were consistently observed to be above the current atmospheric average of 354μmol mol-1. CO2 concentration measurements at some of the springs are reported. The springs are described, and their major topographic and vegetational features are reported. Preliminary observations made on natural vegetation growing around the gas vents are then illustrated. An azonal pattern of vegetation distribution occurs around every CO2 spring regardless of soil type and phytoclimatic areas. This is composed of pioneer populations of a Northern Eurasiatic species (Agrostis canina L.) which is often associated with Scirpus lacustris L. The potential of these sites for studying the long-term response of vegetation to rising atmospheric CO2 concentrations is discussed. 相似文献
63.
The electron donor (component B) to the methyl coenzyme M methylreductase system from Methanosarcina thermophila was isolated as the 7-methyl derivative and characterized. Gas chromatography-mass spectrometry and 1H NMR analyses identified this derivative as 7-methylthioheptanoylthreonine phosphate (CH3-S-HTP), indicating that the original component B had the same structure (HS-HTP) as previously determined for component B from Methanobacterium thermoautotrophicum. The heterodisulfide of HS-HTP and coenzyme M (HS-CoM, 2-mercaptoethanesulfonate) was enzymatically reduced in cell extracts using electrons supplied by either H2 or CO, confirming that HS-HTP was a functional molecule in M. thermophila. 相似文献
64.
Jennifer D. Watts Mary Farina John S. Kimball Luke D. Schiferl Zhihua Liu Kyle A. Arndt Donatella Zona Ashley Ballantyne Eugénie S. Euskirchen Frans-Jan W. Parmentier Manuel Helbig Oliver Sonnentag Torbern Tagesson Janne Rinne Hiroki Ikawa Masahito Ueyama Hideki Kobayashi Torsten Sachs Daniel F. Nadeau John Kochendorfer Marcin Jackowicz-Korczynski Anna Virkkala Mika Aurela Roisin Commane Brendan Byrne Leah Birch Matthew S. Johnson Nima Madani Brendan Rogers Jinyang Du Arthur Endsley Kathleen Savage Ben Poulter Zhen Zhang Lori M. Bruhwiler Charles E. Miller Scott Goetz Walter C. Oechel 《Global Change Biology》2023,29(7):1870-1889
Arctic-boreal landscapes are experiencing profound warming, along with changes in ecosystem moisture status and disturbance from fire. This region is of global importance in terms of carbon feedbacks to climate, yet the sign (sink or source) and magnitude of the Arctic-boreal carbon budget within recent years remains highly uncertain. Here, we provide new estimates of recent (2003–2015) vegetation gross primary productivity (GPP), ecosystem respiration (Reco), net ecosystem CO2 exchange (NEE; Reco − GPP), and terrestrial methane (CH4) emissions for the Arctic-boreal zone using a satellite data-driven process-model for northern ecosystems (TCFM-Arctic), calibrated and evaluated using measurements from >60 tower eddy covariance (EC) sites. We used TCFM-Arctic to obtain daily 1-km2 flux estimates and annual carbon budgets for the pan-Arctic-boreal region. Across the domain, the model indicated an overall average NEE sink of −850 Tg CO2-C year−1. Eurasian boreal zones, especially those in Siberia, contributed to a majority of the net sink. In contrast, the tundra biome was relatively carbon neutral (ranging from small sink to source). Regional CH4 emissions from tundra and boreal wetlands (not accounting for aquatic CH4) were estimated at 35 Tg CH4-C year−1. Accounting for additional emissions from open water aquatic bodies and from fire, using available estimates from the literature, reduced the total regional NEE sink by 21% and shifted many far northern tundra landscapes, and some boreal forests, to a net carbon source. This assessment, based on in situ observations and models, improves our understanding of the high-latitude carbon status and also indicates a continued need for integrated site-to-regional assessments to monitor the vulnerability of these ecosystems to climate change. 相似文献
65.
Global change may have profound effects on soil nitrogen (N) cycling that can induce positive feedback to climate change through increased nitrous oxide (N2O) emissions mediated by nitrification and denitrification. We conducted a meta-analysis of the effects of elevated CO2 on nitrification and denitrification based on 879 observations from 58 publications and 46 independent elevated CO2 experiments in terrestrial ecosystems. We investigated the effects of elevated CO2 alone or combined with elevated temperature, increased precipitation, drought, and N addition. We assessed the response to elevated CO2 of gross and potential nitrification, potential denitrification, and abundances of related functional genes (archaeal amoA, bacterial amoA, nirK, nirS, and nosZ). Elevated CO2 increased potential nitrification (+28%) and the abundance of bacterial amoA functional gene (+62%) in cropland ecosystems. Elevated CO2 increased potential denitrification when combined with N addition and higher precipitation (+116%). Elevated CO2 also increased the abundance of nirK (+25%) and nirS (+27%) functional genes in terrestrial ecosystems and of nosZ (+32%) functional gene in cropland ecosystems. The increase in the abundance of nosZ under elevated CO2 was larger at elevated temperature and high N (+62%). Four out of 14 two-way interactions tested between elevated CO2 and elevated temperature, elevated CO2 and increased precipitation, and elevated CO2 and N addition were marginally significant and mostly synergistic. The effects of elevated CO2 on potential nitrification and abundances of bacterial amoA and nirS functional genes increased with mean annual temperature and mean annual precipitation. Our meta-analysis thus suggests that warming and increased precipitation in large areas of the world could reinforce positive responses of nitrification and denitrification to elevated CO2 and urges the need for more investigations in the tropical zone and on interactive effects among multiple global change factors, as we may largely underestimate the effects of global change on soil N2O emissions. 相似文献
66.
Prem Pritam Aditya P. Sarnaik Pramod P. Wangikar 《Biotechnology and bioengineering》2023,120(8):2363-2370
With multiple applications in food, pharmaceutical, and chemical industries as antioxidant or nonmetabolizable sweetener; the bioproduction of d -mannitol is gaining global attention, especially with photosynthetic organisms as hosts. Considering the sustainability prospects, the current work encompasses metabolic engineering of a widely used cyanobacterial strain, Synechococcus elongatus PCC 7942, and two newly isolated fast-growing cyanobacterial strains; S. elongatus PCC 11801 and S. elongatus PCC 11802, for mannitol production. We engineered these strains with a two-step pathway by cloning genes for mannitol-1-phosphate dehydrogenase (mtlD) and mannitol-1-phosphatase (mlp), where the mtlD expression was under the control of different promoters from PCC 7942, namely, Prbc225, PcpcB300, PcpcBm1, PrbcLm17, and PrbcLm15. The strains were tested under the “switch conditions,” where the growth conditions were switched after the first 3 days, thereby resulting in differential promoter activity. Among the engineered strains of PCC 11801 and PCC 11802, the strains possessing Prbc225-mtlD module produced relatively high mannitol titers of 401 ± 18 mg/L and 537 ± 18 mg/L, respectively. The highest mannitol titer of 701 ± 15 mg/L (productivity 60 mg/L.d, yield 895 µM/OD730) was exhibited by the engineered strain of PCC 7942 expressing PcpcB300-mtlD module. It is by far the highest obtained mannitol yield from the engineered cyanobacteria. 相似文献
67.
The application of cellulose-based stationary phases for chiral separations has been extended to open tubular column chromatography. Efficient columns were obtained by coating the capillaries with mixtures of chiral cellulose materials and conventional achiral stationary phases for gas chromatography. In this study, various siloxane and polyethylene glycol polymers were used as achiral components and mixed with different substituted benzoylcellulose derivatives as chiral components. Systematic investigations were carried out to determine the optimal ratio for the components of the stationary phase. Depending on the chromatographic mode—gas chromatography (GC) or supercritical fluid chromatography (SFC)—the stationary phases were found to behave differently. The applicability of the technique was demonstrated by the resolution of various racemic compounds. © 1993 Wiley-Liss, Inc. 相似文献
68.
An anaerobic granular sludge was enriched to utilize H2/CO2 in a continuous gas-fed up-flow anaerobic sludge reactor by applying operating conditions expected to produce acetic acid, butyric acid, and ethanol. Three stages of fermentation were found: Stage I with acetic acid accumulation with the highest concentration of 35 mM along with a pH decrease from initial 6 to 4.5. In Stage II, H2/CO2 was replaced by 100% H2 to induce solventogenesis, whereas butyric acid was produced with the highest concentration of 2.5 mM. At stage III with 10 µM tungsten (W) addition, iso-valeric acid, valeric acid, and caproic acid were produced at pH 4.5–5.0. In the batch tests inoculated with the enriched sludge taken from the bioreactor (day 70), however, methane production occurred at pH 6. Exogenous 15 mM acetate addition enhanced both the H2 and CO2 consumption rate compared to exogenous 10, 30, and 45 mM acetate by the enriched sludge. Exogenous acetate was failed to be converted to ethanol using H2 as electron donor by the enriched acetogens. 相似文献
69.
L. Romo-Parada L.-P. Vézina P. M. Charest F. Castaigne C. Willemot 《Physiologia plantarum》1991,83(4):664-674
Differences in mitochondrial membrane composition and ultrastructure were studied after storage of cauliflower ( Brassica oleracea , L., Botrytis group) for 5 days at 25°C in air or under controlled atmospheres: 3% O2 , 21% O2 + 15% CO2 or 3% O2 + 15% CO2 . In air, postharvest senescence involved a 20% decrease in mitochondrial phospholipid content. A large reduction in the relative abundance of phosphati-dylcholine (PC) and in the degree of unsaturation of PC and phosphatidyl ethanolamine (PE) was observed. However, the degree of unsaturation increased in cardiolipin (CL). Storage under 3% O2 did not prevent phospholipid breakdown. Low O2 prevented the relative decrease in PC observed during storage in air and the loss of linoleic acid from PC, but not from PE. This relative protection offered by the low O2 atmosphere was lost under 3% O2 + 15% CO2 . The high CO2 atmospheres caused twice as much loss in phospholipids as that observed during storage in air. Extensive loss of mitochondrial protein, a marked decrease in phospholipid to protein ratio, and electron micrograph observations suggest structural alterations in the presence of high CO2 . 相似文献
70.
J. W. Moon D. A. Bailey Jr. E. Fallahi R. G. Jensen G. Zhu 《Physiologia plantarum》1990,80(4):612-618
The relationships between increasing nitrogen fertilization and growth, maximum CO2 assimilation and the initial slope of the CO2 response curve were studied in 2 ecotypes of wild strawberry, Fragaria chiloensis (L.) Duchn. Nitrogen accumulation of CA11, an ecotype from a low-nutrient dune site, was greater at all nitrogen concentrations than that of RCP37, an ecotype from a higher-nutrient strand site. Maximum CO2 assimilation, total Rubisco activity, dry weight, and initiation of leaves and crowns were higher in CAI1 than RCP37 as nitrogen treatment was increased from 0 to 200 mg l-1 , whereas these parameters were lower in CAl1 when fertilized at 300 mg T1 , but not in RCP37. The mean leaf area of CA11 was greater than RCP37 when grown with no supplemental nitrogen, but mean leaf area of the 2 lines was similar under nitrogen fertilization. Maximum CO2 assimilation and carboxylation efficiency increased with increasing leaf nitrogen in both clones. At equivalent concentrations of leaf nitrogen, RCP37 had higher CO2 assimilation and carboxylation efficiency than CA11 and the difference between the 2 clones increased as ieaf nitrogen increased. Thus, RCP37 had a higher photosynthetic nitrogen use efficiency than CA11. However, at a given applied nitrogen level, CA11 allocated more nitrogen to a unit of leaf area so that photosynthetic rates were higher than RCP37, except at the highest application of 300 mg l-1 . The high nitrogen accumulation capacity and resource allocation to fruiting structures (crowns) in CA11 leads us to suggest that this clone may possess genes that could increase fruit yield in cultivated strawberry. 相似文献