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1.
Schnitzler JP Graus M Kreuzwieser J Heizmann U Rennenberg H Wisthaler A Hansel A 《Plant physiology》2004,135(1):152-160
This study was performed to test if alternative carbon sources besides recently photosynthetically fixed CO2 are used for isoprene formation in the leaves of young poplar (Populus x canescens) trees. In a 13CO2 atmosphere under steady state conditions, only about 75% of isoprene became 13C labeled within minutes. A considerable part of the unlabeled carbon may be derived from xylem transported carbohydrates, as may be shown by feeding leaves with [U-13C]Glc. As a consequence of this treatment approximately 8% to 10% of the carbon emitted as isoprene was 13C labeled. In order to identify further carbon sources, poplar leaves were depleted of leaf internal carbon pools and the carbon pools were refilled with 13C labeled carbon by exposure to 13CO2. Results from this treatment showed that about 30% of isoprene carbon became 13C labeled, clearly suggesting that, in addition to xylem transported carbon and CO2, leaf internal carbon pools, e.g. starch, are used for isoprene formation. This use was even increased when net assimilation was reduced, for example by abscisic acid application. The data provide clear evidence of a dynamic exchange of carbon between different cellular precursors for isoprene biosynthesis, and an increasing importance of these alternative carbon pools under conditions of limited photosynthesis. Feeding [1,2-13C]Glc and [3-13C]Glc to leaves via the xylem suggested that alternative carbon sources are probably derived from cytosolic pyruvate/phosphoenolpyruvate equivalents and incorporated into isoprene according to the predicted cleavage of the 3-C position of pyruvate during the initial step of the plastidic deoxyxylulose-5-phosphate pathway. 相似文献
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The tropical African tree species Acacia nigrescens Oliv. was grown in environmentally controlled growth chambers at three CO2 concentrations representative of the Last Glacial Maximum (~180 ppmv), the present day (~380 ppmv), and likely mid‐21st century (~600 ppmv) CO2 concentrations. Isoprene (C5H8) emissions, per unit leaf area, were greater at lower‐than‐current CO2 levels and lower at higher‐than‐current CO2 levels relative to controls grown at 380 ppmv CO2. Changes in substrate availability and isoprene synthase (IspS) activity were identified as the mechanisms behind the observed leaf‐level emission response. In contrast, canopy‐scale emissions remained unaltered between the treatments as changes in leaf‐level emissions were offset by changes in biomass and leaf area. Substrate concentration and IspS activity‐CO2 responses were used in a biochemical model, coupled to existing isoprene emission algorithms, to model isoprene emissions from A. nigrescens grown for over 2 years at three different CO2 concentrations. The addition of the biochemical model allowed for the use of emission factors measured under present day CO2 concentrations across all three CO2 treatments. When isoprene emissions were measured from A. nigrescens in response to instantaneous changes in CO2 concentration, the biochemical model satisfactorily represented the observed response. Therefore, the effect of changes in atmospheric CO2 concentration on isoprene emission at any timescale can be modelled and predicted. 相似文献
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Zhihong Sun Ülo Niinemets Katja Hüve Steffen M. Noe Bahtijor Rasulov Lucian Copolovici Vivian Vislap 《Global Change Biology》2012,18(11):3423-3440
Controversial evidence of CO2‐responsiveness of isoprene emission has been reported in the literature with the response ranging from inhibition to enhancement, but the reasons for such differences are not understood. We studied isoprene emission characteristics of hybrid aspen (Populus tremula x P. tremuloides) grown under ambient (380 μmol mol?1) and elevated (780 μmol mol?1) [CO2] to test the hypothesis that growth [CO2] effects on isoprene emission are driven by modifications in substrate pool size, reflecting altered light use efficiency for isoprene synthesis. A novel in vivo method for estimation of the pool size of the immediate isoprene precursor, dimethylallyldiphosphate (DMADP) and the activity of isoprene synthase was used. Growth at elevated [CO2] resulted in greater leaf thickness, more advanced development of mesophyll and moderately increased photosynthetic capacity due to morphological “upregulation”, but isoprene emission rate under growth light and temperature was not significantly different among ambient‐ and elevated‐[CO2]‐grown plants independent of whether measured at 380 μmol mol?1 or 780 μmol mol?1 CO2. However, DMADP pool size was significantly less in elevated‐[CO2]‐grown plants, but this was compensated by increased isoprene synthase activity. Analysis of CO2 and light response curves of isoprene emission demonstrated that the [CO2] for maximum isoprene emission was shifted to lower [CO2] in elevated‐[CO2]‐grown plants. The light‐saturated isoprene emission rate (Imax,Q) was greater, but the quantum efficiency at given Imax,Q was less in elevated‐[CO2]‐grown plants, especially at higher CO2 measurement concentration, reflecting stronger DMADP limitation at lower light and higher [CO2]. These results collectively demonstrate important shifts in light and CO2‐responsiveness of isoprene emission in elevated‐[CO2]‐acclimated plants that need consideration in modeling isoprene emissions in future climates. 相似文献
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S. E. Petrović M. Škrinjar A. Bećarević I. F. Vujičić L. Banka 《Biotechnology letters》1990,12(4):299-304
Summary The aim of these investigations was to study the conditions for the production of extracellular lipases fromPenicillium
roqueforti S-86, which was isolated from a commercial sample of roqueforti chese type. As carbon sources there have been used the following compounds: 2% glucose, fructose and sucrosel 1% and 2% butterfat and 2% olive oil. Maximal amount of lipases was produced after six days of incubation grown in the medium with 2% of glucose, initial pH of medium 4.0 at 27°C. Cells ofPenicillium
roqueforti grown in the presence of bacto-peptone instead of (NH4)2SO4, as nitrogen source, synthesized maximum quantity of lipases after four days of incubation.The effect of temperature, pH, as well as mono, be and three valent cations: Na+, K+, Ca++, Mn++, Mg++ and Fe+++ on lipase activity was followed. 相似文献
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《BBA》1985,806(3):357-365
Removal of CO2 from pea leaves, which were either grown in a glasshouse at 15°C or in a controlled environment at 23°C, produced an initial increase in chlorophyll fluorescence emission followed by a slow decrease to steady state. From estimations of the redox state of Q, using a nondestructive in vivo technique, the contributions of photochemical and nonphotochemical quenching processes to these fluorescence transients were determined. The fluorescence changes observed on removal of CO2 from the two types of pea leaves were mainly attributable to changes in nonphotochemical quenching although markedly different changes in photochemical quenching were also observed. When leaves grown at 23°C were depleted of CO2, Q immediately became more reduced, whereas in leaves grown at 15°C Q, unexpectedly, became more oxidised. On return of CO2 to the leaves these phenomena were reversed, i.e., in leaves grown at 23°C Q became more oxidised and in the 15°C grown leaves Q became more reduced. Increased electron transport to O2 may account for the oxidation of Q on depletion of CO2 from 15°C grown leaves. The generation of fluorescence transients on removal and return of CO2 to the leaf required the presence of oxygen. The fast fluorescence kinetics observed on exposure of the leaf at steady state to a second saturating irradiation suggest that O2 may accept electrons directly from Photosystem II at a site between Q and B. 相似文献
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Guanghui Lin John Adams Blake Farnsworth Yongdan Wei Bruno D. V. Marino Joseph A. Berry 《Oecologia》1999,119(1):97-108
The ecosystem-level carbon uptake and respiration were measured under different CO2 concentrations in the tropical rainforest and the coastal desert of Biosphere 2, a large enclosed facility. When the mesocosms
were sealed and subjected to step-wise changes in atmospheric CO2 between daily means of 450 and 900 μmol mol−1, net ecosystem exchange (NEE) of CO2 was derived using the diurnal changes in atmospheric CO2 concentrations. The step-wise CO2 treatment was effectively replicated as indicated by the high repeatability of NEE measurements under similar CO2 concentrations over a 12-week period. In the rainforest mesocosm, daily NEE was increased significantly by the high CO2 treatments because of much higher enhancement of canopy CO2 assimilation relative to the increase in the nighttime ecosystem respiration under high CO2. Furthermore, the response of daytime NEE to increasing atmospheric CO2 in this mesocosm was not linear, with a saturation concentration of 750 μmol mol−1. In the desert mesocosm, a combination of a reduction in ecosystem respiration and a small increase in canopy CO2 assimilation in the high CO2 treatments also enhanced daily NEE. Although soil respiration was not affected by the short-term change in atmospheric CO2 in either mesocosm, plant dark respiration was increased significantly by the high CO2 treatments in the rainforest mesocosm while the opposite was found in the desert mesocosm. The high CO2 treatments increased the ecosystem light compensation points in both mesocosms. High CO2 significantly increased ecosystem radiation use efficiency in the rainforest mesocosm, but had a much smaller effect in the
desert mesocosm. The desert mesocosm showed much lower absolute response in NEE to atmospheric CO2 than the rainforest mesocosm, probably because of the presence of C4 plants. This study illustrates the importance of large-scale experimental research in the study of complex global change
issues.
Received: 30 October 1998 / Accepted: 2 December 1998 相似文献
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John Lussenhop Amy Treonis Peter S. Curtis James A. Teeri Christoph S. Vogel 《Oecologia》1998,113(2):247-251
We tested the hypotheses that increased belowground allocation of carbon by hybrid poplar saplings grown under elevated atmospheric
CO2 would increase mass or turnover of soil biota in bulk but not in rhizosphere soil. Hybrid poplar saplings (Populus×euramericana cv. Eugenei) were grown for 5 months in open-bottom root boxes at the University of Michigan Biological Station in northern,
lower Michigan. The experimental design was a randomized-block design with factorial combinations of high or low soil N and
ambient (34 Pa) or elevated (69 Pa) CO2 in five blocks. Rhizosphere microbial biomass carbon was 1.7 times greater in high-than in low-N soil, and did not respond
to elevated CO2. The density of protozoa did not respond to soil N but increased marginally (P < 0.06) under elevated CO2. Only in high-N soil did arbuscular mycorrhizal fungi and microarthropods respond to CO2. In high-N soil, arbuscular mycorrhizal root mass was twice as great, and extramatrical hyphae were 11% longer in elevated
than in ambient CO2 treatments. Microarthropod density and activity were determined in situ using minirhizotrons. Microarthropod density did
not change in response to elevated CO2, but in high-N soil, microarthropods were more strongly associated with fine roots under elevated than ambient treatments.
Overall, in contrast to the hypotheses, the strongest response to elevated atmospheric CO2 was in the rhizosphere where (1) unchanged microbial biomass and greater numbers of protozoa (P < 0.06) suggested faster bacterial turnover, (2) arbuscular mycorrhizal root length increased, and (3) the number of microarthropods
observed on fine roots rose.
Received: 18 March 1997 / Accepted: 5 August 1997 相似文献
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Effects of elevated CO(2) on soil microorganisms are known to be mediated by various interactions with plants, for which such effects are relatively poorly documented. In this review, we summarize and synthesize results from studies assessing impacts of elevated CO(2) on soil ecosystems, focusing primarily on plants and a variety the of microbial processes. The processes considered include changes in microbial biomass of C and N, microbial number, respiration rates, organic matter decomposition, soil enzyme activities, microbial community composition, and functional groups of bacteria mediating trace gas emission such as methane and nitrous oxide. Elevated CO(2) in atmosphere may enhance certain microbial processes such as CH(4) emission from wetlands due to enhanced carbon supply from plants. However, responses of extracellular enzyme activities and microbial community structure are still controversy, because interferences with other factors such as the types of plants, nutrient availabilitial in soil, soil types, analysis methods, and types of CO(2) fumigation systems are not fully understood. 相似文献
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Azospirillum brasilense Sp7 and two mutants were examined for 19 carbon metabolism enzymes. The results indicate that this nitrogen fixer uses the Entner-Doudoroff pathway for gluconate dissimilation, lacks a catabolic but has an anabolic Embden-Meyerhof-Parnas hexosephosphate pathway, has amphibolic triosephosphate enzymes, lacks a hexose monophosphate shunt, and has lactate dehydrogenase, malate dehydrogenase, and glycerokinase. The mutants are severely deficient in phosphoglycerate and pyruvate kinase and also have somewhat reduced levels of other carbon enzymes. 相似文献
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Because the precipitation of calcium carbonate results in the sequestering of carbon, it frequently has been thought that coral reefs functions as sinks of global atmospheric CO2. However, the precipitation of calcium carbonate is accompanied by a shift of pH that results in the release of CO2. This release of CO2 is less in buffered sea water than fresh water systems; nevertheless, coral reefs are sources, not sinks, of atmospheric carbon. Using estimated rates of coral reef carbonate production, we compute that coral reefs release 0.02 to 0.08 Gt C as CO2 annually. This is approximately 0.4% to 1.4% of the current anthropogenic CO2 production due to fossil fuel combustion. 相似文献
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Accelerated tree growth under elevatedatmospheric CO2 concentrations may influencenutrient cycling in forests by (i) increasingthe total leaf area, (ii) increasing the supplyof soluble carbohydrate in leaf tissue, and (iii) increasing nutrient-use efficiency. Here wereport the results of intensive sampling andlaboratory analyses of NH
4
+
, NO
3
–
, PO
4
3–
, H+, K+, Na+,Ca2+, Mg2+, Cl–, SO
4
2–
, and dissolved organic carbon (DOC) in throughfallprecipitation during the first 2.5+ years of the DukeUniversity Free-Air CO2 Enrichment (FACE)experiment. After two growing seasons, a largeincrease (i.e., 48%) in throughfall deposition of DOCand significant trends in throughfall volume and inthe deposition of NH
4
+
, NO
3
–
, H+, and K+ can be attributed to the elevatedCO2 treatment. The substantial increase indeposition of DOC is most likely associated withincreased availability of soluble C in plant foliage,whereas accelerated canopy growth may account forsignificant trends toward decreasing throughfallvolume, decreasing deposition of NH
4
+
,NO
3
–
, and H+, and increasing deposition of K+ under elevated CO2. Despiteconsiderable year-to-year variability, there wereseasonal trends in net deposition of NO
3
–
,H+, cations, and DOC associated with plant growthand leaf senescence. The altered chemical fluxes inthroughfall suggest that soil solution chemistry mayalso be substantially altered with continued increasesin atmospheric CO2 concentrations in the future. 相似文献
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CO2是光合作用的原料和底物,影响着光合作用的进程和光合产物的数量.利用Li-6400-40B同时测量大豆叶片在不同CO2浓度(300、400、500和600 μmol·mol-1)下的光合电子传递速率和光合作用对光的响应曲线,并用构建的光合作用对光响应机理模型拟合这些光响应曲线,获得大豆叶片一系列的光合参数、生理生态参数和捕光色素分子的物理参数.结果表明: 电子利用效率、最大电子传递速率和最大净光合速率随CO2浓度的升高而增加;光补偿点和暗呼吸速率随CO2浓度的升高而下降;光能利用效率和内禀(瞬时)水分利用效率随CO2浓度的升高而增加,不同CO2浓度下的最大光能利用效率和最大内禀(瞬时)水分利用效率之间存在显著差异,但不同CO2浓度下的最大羧化效率的差异不显著.CO2浓度的大小对光合作用中原初光反应存在一定程度的影响,即高CO2浓度有利于减小捕光色素分子处于最低激发态的最小平均寿命,以提高光能传递的速度及增加大豆光合电子流的利用效率. 相似文献
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Dynamics of soil CO2 efflux under varying atmospheric CO2 concentrations reveal dominance of slow processes
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《Global Change Biology》2017,23(9):3501-3512
We evaluated the effect on soil CO2 efflux (FCO2) of sudden changes in photosynthetic rates by altering CO2 concentration in plots subjected to +200 ppmv for 15 years. Five‐day intervals of exposure to elevated CO2 (eCO2) ranging 1.0–1.8 times ambient did not affect FCO2. FCO2 did not decrease until 4 months after termination of the long‐term eCO2 treatment, longer than the 10 days observed for decrease of FCO2 after experimental blocking of C flow to belowground, but shorter than the ~13 months it took for increase of FCO2 following the initiation of eCO2. The reduction of FCO2 upon termination of enrichment (~35%) cannot be explained by the reduction of leaf area (~15%) and associated carbohydrate production and allocation, suggesting a disproportionate contraction of the belowground ecosystem components; this was consistent with the reductions in base respiration and FCO2‐temperature sensitivity. These asymmetric responses pose a tractable challenge to process‐based models attempting to isolate the effect of individual processes on FCO2. 相似文献
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The responses of individual stomata to CO2 concentrations ranging from 0 to 900 μmol mol−1 air were analysed in Ipomoea pes-caprae L. Sweet (Convolvulaceae). The stomata were directly observed using a measurement system that permitted continuous observation of stomatal movement under controlled light and CO2 conditions. A CO2 concentration of 350 μmol mol−1 or higher induced stomatal closure, whereas concentrations below 350 μmol mol−1 did not. The time lag before stomatal closure decreased with increasing CO2 concentration, as did the steady-state aperture of the stomata after a change in CO2 concentration. However, the rate of stomatal closure increased with increasing CO2 concentration. Therefore, not only the stomatal closure rate but also the time from the CO2 concentration change to the beginning of stomatal closure changed with increasing CO2 concentration. These results suggest that atmospheric CO2 may be the stimulus for the closure of guard cells. No significant differences were observed between adaxial and abaxial stomata in terms of their responses to CO2 . However, heterogeneous responses were detected between neighbouring stomata on each leaf surface. 相似文献