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1.
关于氮素对高大气CO2浓度下C3植物光合作用适应现象的调节机理已有较为深入的研究, 但对其光合作用适应现象的光合能量转化和分配机制缺乏系统分析。该文以大气CO2浓度和施氮量为处理手段, 通过测定小麦(Triticum aestivum)抽穗期叶片的光合作用-胞间CO2浓度响应曲线以及荧光动力学参数来测算光合电子传递速率和分配去向, 研究了长期高大气CO2浓度下小麦叶片光合电子传递和分配对施氮量的响应。结果表明, 与正常大气CO2浓度处理相比, 高大气CO2浓度下小麦叶片较多的激发能以热量的形式耗散, 增施氮素可使更多的激发能向光化学反应方向的分配, 降低光合能量的热耗散速率; 大气CO2浓度升高后小麦叶片光化学淬灭系数无明显变化, 高氮叶片的非光化学猝灭降低而低氮叶片明显升高, 施氮促进PSII反应中心的开放比例, 降低光能的热耗散; 高大气CO2浓度下高氮叶片通过PSII反应中心的光合电子传递速率(JF)较高, 而且参与光呼吸的非环式电子流速率(J0)显著降低, 较正常大气CO2浓度处理的高氮叶片下降了88.40%, 光合速率增加46.47%; 高大气CO2浓度下小麦叶片JF-J0升高而J0/JF显著下降, 光呼吸耗能被抑制, 更多的光合电子分配至光合还原过程。因此, 大气CO2浓度增高条件下, 小麦叶片激发能的热耗散速率增加, 但增施氮素后小麦叶片PSII反应中心开放比例提高, 光化学速率增加, 进入PSII反应中心的电子流速率明显升高, 光呼吸作用被抑制, 光合电子较多地进入光化学过程, 这可能是高氮条件下光合作用适应性下调被缓解的一个原因。 相似文献
2.
Susan Waldron Irene A. Watson‐Craik Allan J. Hall Anthony E. Fallick 《Geomicrobiology journal》2013,30(3):157-169
Anaerobic bacterial degradation of landfill waste produces a globally significant source of the greenhouse gas methane. Stable isotopic measurements of methane [δI3C(CH4) and δD(CH4)] can often fingerprint different sources of methane (natural vs. anthro‐pogenic) and help identify the bacterial processes involved in methane production. Landfill microbial communities are complex and diverse, and hence so too is the biogeochem‐istry of methane formation. To investigate the influence of (l) the methane formation pathway (acetoclastic methanogenesis and CO2 reduction), and (2) SD of water on the stable isotopic composition of landfill methane, two model butyrate‐degrading landfill systems were established. The systems were inoculated with domestic refuse from a landfill and incubated in the laboratory for 92 days. Both systems were identical except δD of water initially added to system 2 was 118% heavier than system 1. Between days 39 and 72 the systems were resupplemented with butyrate. Production of CH4 and CO2 and changes in volatile fatty acid concentration confirmed that active methanogenic populations had been established. CH4 became 13C enriched in both incubations with time. Interpreting changes in acetate, butyrate, and propionate concentration during incubation is complicated, but these observations and other information suggest that the dominant methanogenic substrate changed front CO2/H2 to acetate as the experiment progressed. This is also consistent with the observed 13C enrichment of CH4, as 13C discrimination during methane production from acetate is less than from CO2. In contrast, δD(CH4) remained relatively constant, suggesting that this measurement may not provide a reliable basis for distinguishing between CH4 from CO2 reduction and acetoclastic methanogenesis, as has previously been suggested. 相似文献
3.
《Journal of Plant Interactions》2013,8(1):74-84
Abstract The concentration and composition of free amino acids and carbohydrates in the phloem sap of wheat and oilseed rape (OSR) and the effects on the performance of aphids (Rhopalosiphum padi and Myzus persicae) were determined under atmospheric carbon dioxide (CO2) enrichment. The analysis of phloem sap showed that carbohydrates and amino acid levels of the host plants were significantly affected by elevated CO2 level. Among carbohydrate concentrations in the phloem sap, significant increases were observed in fructose and glucose in spring wheat under CO2 enrichment, whereas no changes were observed in OSR. These changes in plant chemistry affected the performance of herbivorous insects (i.e. aphids) in varying ways, positively affecting the relative growth rate (RGR) of R. padi in spring wheat and negatively affecting the RGR of M. persicae on OSR. 相似文献
4.
Jian-Guo Huang Yves Bergeron Bernhard Denneler Frank Berninger Jacques Tardif 《植物科学评论》2007,26(5-6):265-283
The CO 2 fertilization hypothesis stipulates that rising atmospheric CO 2 has a positive effect on tree growth due to increasing availability of carbon. The objective of this paper is to compare the recent literature related to both field CO 2 -enriched experiments with trees and empirical dendrochronological studies detecting CO 2 fertilization effects in tree-rings. This will allow evaluation of tree growth responses to atmospheric CO 2 enrichment by combining evidence from both ecophysiology and tree-ring research. Based on considerable experimental evidence of direct CO 2 fertilization effect (increased photosynthesis, water use efficiency, and above- and belowground biomass), and predications from the interactions of enriched CO 2 with temperature, nitrogen and drought, we propose that warm, moderately drought-stressed ecosystems with an ample nitrogen supply might be the most CO 2 responsive ecosystems. Empirical tree-ring studies took the following three viewpoints on detecting CO 2 fertilization effect in tree-rings: 1) finding evidence of CO 2 fertilization effect in tree-rings, 2) attributing growth enhancement to favorable climate rather than atmospheric CO 2 enrichment, and 3) considering that tree growth enhancement might be caused by synergistic effects of several factors such as favorable climate change, CO 2 fertilization, and anthropogenic atmospheric deposition (e.g., nitrogen). At temperature-limiting sites such as high elevations, nonfindings of CO 2 fertilization evidence could be ascribed to the following possibilities: 1) cold temperatures, a short season of cambial division, and nitrogen deficiency that preclude a direct CO 2 response, 2) old trees past half of their maximum life expectancy and consequently only a small increase in biomass increment due to CO 2 fertilization effect might be diminished, 3) the elimination of age/size-related trends by statistical detrending of tree-ring series that might remove some long-term CO 2 -related trends in tree-rings, and 4) carbon partitioning and growth within a plant that is species-specific. Our review supports the atmospheric CO 2 fertilization effect hypothesis, at least in trees growing in semi-arid or arid conditions because the drought-stressed trees could benefit from increased water use efficiency to enhance growth. 相似文献
5.
A. Lintunen L. Lindfors P. Kolari E. Juurola E. Nikinmaa T. H?ltt? 《Annals of botany》2014,114(8):1711-1718
MethodsCO2 efflux measurements were conducted during freezing experiments for saplings of three Scots pine (Pinus sylvestris) and three Norway spruce (Picea abies) trees under laboratory conditions, and the magnitudes of the freezing-related bursts of CO2 released from the stems were analysed using a previously published mechanistic model of CO2 production, storage, diffusion and efflux from a tree stem. The freezing-related bursts of CO2 released from a mature Scots pine tree growing in field conditions were also measured and analysed.ConclusionsAll gases dissolved in the xylem sap are not trapped within the ice in the stem during freezing, as has previously been assumed, thus adding a new dimension to the understanding of winter embolism formation. The conduit water volume not only determines the volume of bubbles formed during freezing, but also the efficiency of gas efflux out of the conduit during the freezing process. 相似文献
6.
Susanne von Caemmerer 《Planta》1989,178(4):463-474
A model of leaf, photosynthesis has been developed for C3–C4 intermediate species found in the generaPanicum, Moricandia, Parthenium andMollugo where no functional C4 pathway has been identified. Model assumptions are a functional C3 cycle in both mesophyll and bundle-sheath cells and that glycine formed in the mesophyll, as a consequence of the oxygenase activity of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco, EC 4.1.1.39), diffuses to the bundle sheath, where most of the photorespiratory CO2 is released. The model describes the observed gas-exchange characteristics of these C3–C4 intermediates, such as low CO2-compensation points () at an O2 pressure of 200 mbar, a curvilinear response of to changing O2 pressures, and typical responses of CO2-assimilation rate to intercellular CO2 pressure. The model predicts that bundle-sheath CO2 concentration is highest at low mesophyll CO2 pressures and decreases as mesophyll CO2 pressure increases. A partitioning of 5–15% of the total leaf Rubisco into the bundle-sheath cells and a bundlesheath conductance similar to that proposed for C4 species best mimics the gas-exchange results. The model predicts C3-like carbon-isotope discrimination for photosynthesis at atmospheric levels of CO2, but at low CO2 pressures it predicts a higher discrimination than is typically found during C3 photosynthesis at lower CO2 pressures.Abbreviations and symbols PEP
phosphoenolpyruvate
- Rubisco
ribulose-1,5-bisphosphate carboxylase-oxygenase (EC 4.1.1.39)
- RuBP
ribulose-1,5-bisphosphate
-
p(CO2)
partial pressure of CO2
-
p(O2)
partial pressure of O2. See also p. 471 相似文献
7.
Mauro Centritto 《Plant biosystems》2013,147(1):31-37
ABSTRACT Birch (Betula pendula Roth.) seedlings were kept for two growing seasons under ambient (~350 µmol mol-1) and elevated (~700 µmol mol-1) [CO2]. The present study was designed to examine the effects of [CO2] and pot size on growth and carbon allocation under conditions of non-limiting water and nutrient supply, in order to separate the effects of source-sink interaction from the effects of nutrient deficiency. The manipulation of the source-sink relations had a strong influence on the growth response to elevated [CO2]. When the rooting volume was inadequate, it resulted in a source-sink imbalance which constrained growth under elevated [CO2]. When root exploration was unconstrained, total dry mass was significantly increased (by about 24%) under elevated [CO2]. However, the allometric relationships in allocation pattern and in morphogenetic development were not affected by either [CO2] or pot treatments when the saplings were of the same size. Thus, by constraining dry mass production, small sinks affected the magnitude of the growth responses to elevated [CO2], but did not affect the plant allocation pattern and allometric relationships when nutrient supply was non-limiting. However, by slowing down growth, sink restrictions counteract the speed-up of ontogeny which is the main effect of elevated [CO2] on tree growth. 相似文献
8.
Remarkably, bathing in hot springs containing high concentrations of carbon dioxide (CO2) influences cardiovascular function more than bathing in fresh water. The CO2-enriched water in hot springs generally contains many salts, whose interactions remain unknown. We separately evaluated the
actions of individual factors in CO2-enriched water and confirmed that CO2 and NaCl have combined effects on blood pressure fluctuations in anesthetized rats. Animals equipped with sensor probes to
monitor body temperature, skin blood flow and arterial blood pressure were immersed in bathwater (35°C) containing CO2 with NaCl, KCl or sucrose. The effects of these factors on cardiovascular function were evaluated using power-spectral analysis
of fluctuations in blood pressure and heart rate. Compared with immersion in tap water, heart rate and skin vascular resistance
were reduced during immersion in CO2-enriched water irrespective of the presence of other components. In terms of the very low frequency range (0.02–0.195 Hz),
the power of blood pressure fluctuation during immersion was significantly reduced when the CO2-enriched water contained more than 1.5% NaCl but was not influenced by other components of similar osmotic pressure and the
same specific gravity. The results indicated that the coexistence of CO2 and sodium ions in bathwater reduce blood pressure fluctuations, and suggested that this combination effect of CO2 and salt contributes to the sedative effect on human cardiovascular functions while bathing in CO2-hot springs. 相似文献
9.
Ingrid Zondervan Björn RostUlf Riebesell 《Journal of experimental marine biology and ecology》2002,272(1):55-70
We compared the effect of CO2 concentration ([CO2], ranging from ∼5 to ∼34 μmol l−1) at four different photon flux densities (PFD=15, 30, 80 and 150 μmol m−2 s−1) and two light/dark (L/D) cycles (16/8 and 24/0 h) on the coccolithophore Emiliania huxleyi. With increasing [CO2], a decrease in the particulate inorganic carbon to particulate organic carbon (PIC/POC) ratio was observed at all light intensities and L/D cycles tested. The individual response in cellular PIC and POC to [CO2] depended strongly on the PFD. POC production increased with rising [CO2], irrespective of the light intensity, and PIC production decreased with increasing [CO2] at a PFD of 150 μmol m−2 s−1, whereas below this light level it was unaffected by [CO2]. Cell growth rate decreased with decreasing PFD, but was largely independent of ambient [CO2]. The diurnal variation in PIC and POC content, monitored over a 38-h period (16/8 h L/D, PFD=150 μmol m−2 s−1), exceeded the difference in carbon content between cells grown at high (∼29 μmol l−1) and low (∼4 μmol l−1) [CO2]. However, consistent with the results described above, cellular POC content was higher and PIC content lower at high [CO2], compared to the values at low [CO2], and the offset was observed throughout the day. It is suggested that the observed sensitivity of POC production for ambient [CO2] may be of importance in regulating species-specific primary production and species composition. 相似文献
10.
Summary Red algae have the highest known selectivity factor (Srel) for CO2 over O2 of ribulose bisphosphate carboxylase-oxygenase (RUBISCO). This allows the prediction that a red alga relying on diffusive supply of CO2 to RUBISCO from air-equilibrated solution should have less O2 inhibition of photosynthesis than would an otherwise similar non-red alga with a lower Srel of RUBISCO. Furthermore, RUBISCO shows an increased Srel values at low temperatures. The prediction that O 2inhibition of photosynthesis should be small for marine red algae relying on diffusive CO2 entry growing in the North Sea with an annual temperature range of 4–16°C was tested in O2 electrode experiments at 12°C. Phycodrys rubens and Plocamium cartilagineum, which rely on diffusive CO2 entry showed, as predicted, only a small inhibition at lower inorganic C concentrations. Palmaria palmata, which has a CO2 concentrating mechanism, had the expected negligible O 2 inhibition of photosynthesis at any inorganic C concentration except (non-significantly) for saturating inorganic C. 相似文献
11.
Numerous studies focus on the measurement of conductances for CO2 transfer in plants and especially on their regulatory effects on photosynthesis. Measurement accuracy is strongly dependent on the model used and on the knowledge of the flow of photochemical energy generated by light in chloroplasts. The only accurate and precise method to quantify the linear electron flux (responsible for the production of reductive energy) is the direct measurement of O2 evolution, by 18O2 labelling and mass spectrometry. The sharing of this energy between the carboxylation (P) and the oxygenation of photorespiration (PR) depends on the plant specificity factor (Sp) and on the corresponding atmospheric concentrations of CO2 and O2 ( André, 2013). The concept of plant specificity factor simplifies the equations of the model. It gives a new expression of the effect of the conductance (g) between atmosphere and chloroplasts. Its quantitative effect on photosynthesis is easy to understand because it intervenes in the ratio of the plant specificity factor (Sp) to the specificity of Rubisco (Sr). Using this ‘simple’ model with the data of 18O2 experiments, the calculation of conductance variations in response to CO2 and light was carried out. 相似文献
12.
Kenji Kanemoto Yumiko Yamashita Tomoko Ozawa Naomi Imanishi Nguyen Tran Nguyen Ryuichi Suwa Pravat Kumar Mohapatra Syunsuke Kanai Reda E. Moghaieb Junki Ito Hany El-Shemy Kounosuke Fujita 《Plant science》2009,177(5):398-403
Physiological processes that modulate photosynthetic acclimation to rising atmospheric CO2 concentration are subjects of intense discussion recently. Apparently, the down-regulation of photosynthesis under elevated CO2 is not understood clearly. In the present study, the response of soybean (Glycine max L.) to CO2 enrichment was examined in terms of nitrogen partitioning and water relation. The plants grown under potted conditions without combined N application were exposed to either ambient air (38 Pa CO2) or CO2 enrichment (100 Pa CO2) for short (6 days) and long (27 days). Plant biomass, apparent photosynthetic rate, transpiration rate and 15N uptake and partitioning were measured consecutively after elevated CO2 treatment. Long-term exposure reduced photosynthetic rate, stomatal conductance and transpiration rate. In contrast, short-term exposure increased biomass production of soybean due to increase in dry weight of leaves. Leaf N concentration tended to decrease with CO2 enrichment, however such difference was not true for stem and roots.A close correlation was observed between transpiration rate and 15N partitioned into leaves, suggesting that transpiration plays an important role on nitrogen partitioning to leaves. In conclusion existence of a feed back mechanism for photosynthetic acclimation has been proposed. Down-regulation of photosynthetic activity under CO2 enrichment is caused by decreasing leaf N concentration, and reduced rate of transpiration owing to decreased stomatal conductance is partially responsible for poor N translocation. 相似文献
13.
Anatoly Zyakun Seth Nii-Annang Gabriele Franke Thomas Fischer Franz Buegger Oliver Dilly 《Geomicrobiology journal》2013,30(6):570-584
The dynamics of microbial degradation of exogenous contaminants, n-hexadecane and its primary microbial oxidized metabolite, n-hexadecanoic (palmitic) acid, was studied for topsoils, under agricultural management and beech forest on the basis the changes in O2 uptake, CO2 evolution and its associated carbon isotopic signature, the respiratory quotient (RQ) and the priming effect (PE) of substrates. Soil microbial communities in agricultural soil responded to the n-hexadecane addition more rapidly compared to those of forest soil, with lag-periods of about 23 ± 10 and 68 ± 13 hours, respectively. Insignificant difference in the lag-period duration was detected for agricultural (tlag = 30 ± 13 h) and forest (tlag = 30 ± 14 h) soils treated with n-hexadecanoic (palmitic) acid. These results demonstrate that the soil microbiota has different metabolic activities for using n-hexadecane as a reductive hydrocarbon and n-hexadecanoic acid as a partly oxidized hydrocarbon. The corresponding δ13C of respired CO2 after the addition of the hydrocarbon contaminants to soils indicates a shift in microbial activity towards the consumption of exogenous substrates with a more complete degradation of n-hexadecane in the agricultural soil, for which some initial contents of hydrocarbons are inherent. It is supposed that the observed deviation of RQ from theoretically calculated value under microbial substrate mineralization is determined by difference in the time (Δti) of registration of CO2 production and O2 consumption. Positive priming effect (PE) of n-hexadecane and negative PE of n-hexadecanoic (palmitic) acid were detected in agricultural and forest soils. It is suggested that positive PE of n-hexadecane is conditioned by the induction of microbial enzymes that perform hydroxylation/oxygenation of stable SOM compounds mineralized by soil microbiota to CO2. The microbial metabolism coupled with oxidative decarboxylation of n-hexadecanoic acid is considered as one of the most probable causes of the revealed negative PE value. 相似文献
14.
AbstractCarbonic anhydrase (CA) is the most effective CO2 hydratase catalyst, but the poor storage stability and repeatability of CA limit its development. Therefore, CA was immobilized on the epoxy magnetic composite microspheres to enhance the CO2 absorption into N-methyldiethanolamine (MDEA) aqueous solution in this work. In the presence of immobilized CA, the CO2 absorption rate of MDEA solution (10?wt%) (0.63?mmol·min?1) was greatly improved by almost 40%, and their reaction equilibrium time was shortened from 150?min to 90?min compared with that into MDEA solution. The results indicated that the absorption of CO2 into MDEA solution had been significantly enhanced by using CA. After the 7th reuse recycle, the activity of the immobilized CA was still closed to its initial value at 313.15?K. Moreover, enzyme catalytic kinetics of immobilized CA was investigated using the p-nitrophenyl acetate (p-NPA) as substrate. The values of Michaelis–Menten constant (Km) and the maximum velocity (Vmax) of the immobilized CA were calculated to be 27.61?mmol/L and 20.14?×?10?3?mmol·min?1·mL?1, respectively. Besides, the kinetics of CO2 reaction into MDEA with or without CA were also compared. The results showed that CO2 absorption into CA/MDEA aqueous solution obeyed the pseudo first order regime and the second order kinetics rate constant (k2) was calculated to be 929?m3·kmol?1·s?1, which was twice higher than that of MDEA aqueous solution without immobilized CA (k2=414 m3·kmol?1·s?1) at 313.15?K. 相似文献
15.
Z.-J. Mao Y.-J. Wang X.-W. Wang P. Yu. Voronin 《Russian Journal of Plant Physiology》2005,52(2):171-175
Two-year old birch (Betula platyphylla Suk.) seedlings were grown in climatic chambers for 7 weeks under various conditions: (1) ambient CO2 concentration (350 ppm) and an ordinary nitrogen content in soil (2 mM NH4NO3); (2) ambient CO2 concentration and a high nitrogen rate (16 mM NH4NO3); (3) doubled CO2 concentration (700 ppm) and ordinary nitrogen content, and (4) doubled CO2 concentration and a high nitrogen rate. Doubled CO2 concentration in combination with the high nitrogen rate activated mostly seedling growth, e.g., stem thickening and leaf initiation. In this treatment, the maximum rate of apparent photosynthesis (A
max) was twice as high as in control seedlings. At doubled CO2 concentration and ordinary nitrogen content, we observed the phenomenon of stomata absence from the upper leaf surface and doubling their number on the lower surface, whereas, at doubled CO2 concentration and a high nitrogen rate, stomata partition was essentially similar as in control leaves. The conclusion is that, when the balance between CO2 concentration and nitrogen rate is shifted, doubled CO2 concentration exerts a morphotropic effect on differentiation of young epidermal tissue.Translated from Fiziologiya Rastenii, Vol. 52, No. 2, 2005, pp. 198–202.Original Russian Text Copyright © 2005 by Mao, Y.-J. Wang, X.-W. Wang, Voronin.This revised version was published online in April 2005 with a corrected cover date. 相似文献
16.
能源活动CO2排放不同核算方法比较和减排策略选择 总被引:1,自引:0,他引:1
能源活动CO2排放是温室气体排放的最重要部分,这部分CO2排放量的核算是温室气体清单编制和减排方案制定的关键和基础。采用直接法、电热终端法和隐含终端法核算了2009年中国能源消费的CO2排放量,对不同核算法的CO2排放部门分布、部门排放强度进行了比较,明确不同核算方法的差异和适用范围。采用电热终端法的核算结果定量分析了各产业部门和工业行业的经济增长和排放强度变化对中国能源活动CO2排放增长的影响。结果表明,中国2009年隐含终端CO2排放量为65.6亿t,略高于直接和电热终端CO2排放量62.2亿t。3种核算方法的CO2排放部门分布和排放强度有明显的差异:电、热力生产与供应业的直接排放占比为45.2%,而电热终端CO2排放仅占4.5%;制造业的直接法、电热终端法和隐含终端法核算的CO2排放占比分别为35.3% 、61.1%和65.5%,是终端能源消费CO2排放最主要的部门;制造业、电热力生产与供应业和交通运输业的电热终端CO2排放强度分别为2.166、1.72和1.622 t CO2/万元GDP,是排放强度较高的部门。在产业部门中,制造业的色金属冶炼及压延加工业、非金属矿物制品业等5个行业以9.8%的经济增长贡献,排放了52.4%的CO2,是产业结构调整、技术和工程减排的重点;服务业以7.2%的CO2排放,贡献了38.4%的经济增长,应作为中国低碳经济优先发展的产业。 相似文献
17.
AbstractBiogas from anaerobic digestion of biological wastes is a renewable energy resource that mainly contains CH4, CO2, trace amounts of H2S and a fraction of H2O vapour. In order to transfer biogas into biomethane to meet the standards for use as vehicle fuel or for injection in the natural gas grid, removing H2S from biogas in advance is necessary. In addition, biogas is usually saturated with water vapour. It is significant to study the effect of the presence of H2O on the biogas separation performance. Adsorption of H2S/CO2/CH4 and H2O/CO2/CH4 ternary mixtures using single-walled carbon nanotubes (SWCNT) were investigated via the Grand Canonical Monte Carlo (GCMC) method. We studied the effects of carbon nanotube diameter, –COOH modification, temperature and pressure on H2S adsorption. The results indicate that the presence of hydrophilic –COOH groups does affect the separation of H2S/CO2/CH4 mixtures. Temperature swing adsorption is more suitable than pressure swing adsorption for the separation of H2S/CO2/CH4 mixtures. The effect of water vapour on the separation of CO2/CH4 was also investigated. The result shows that the presence of H2O has little effect on the selectivity of CO2/CH4 in pristine CNT, but the selectivity of CO2/CH4 with the presence of H2O is markedly enhanced after modification in –COOH modified SWCNT with specific modification degree. It is expected that this work could provide some useful information for biogas upgrading. 相似文献
18.
The structures and stabilities of eleven N13
+ and N13
– isomers have been investigated with second-order Møller–Plesset (MP2) and density functional theory (DFT) methods. Five N13
+ isomers and six N13
– isomers are all reasonable local minima on their potential energy hypersurfaces. The most stable N13
+ cation is structure C-2 with C2v symmetry, which contains a pentazole ring and two N4 open chains. It is different from those of the N7
+ and N9
+ clusters, but similar to the N11
+ cluster. Meanwhile, the most stable N13
– structure A-2 is composed of a pentazole ring and a six-membered ring connected by two nitrogen atoms. It is not only different from those of the N7
– and N9
– clusters, but also from the N11
– cluster. The decomposition pathways of structures C-2 and A-2 were investigated at the B3LYP/(aug)-cc-pVDZ level. From the barrier heights of the structures C-2 and A-2 decomposition processes, it is suggested that C-2 is difficult to observe experimentally and A-2 may be observed as a short-lived species.
Figure Optimized geometrical parameters of N13
+ isomer C-2
相似文献
19.
Some relationships between the biochemistry of photosynthesis and the gas exchange of leaves 总被引:84,自引:2,他引:82
A series of experiments is presented investigating short term and long term changes of the nature of the response of rate of CO2 assimilation to intercellular p(CO2). The relationships between CO2 assimilation rate and biochemical components of leaf photosynthesis, such as ribulose-bisphosphate (RuP2) carboxylase-oxygenase activity and electron transport capacity are examined and related to current theory of CO2 assimilation in leaves of C3 species. It was found that the response of the rate of CO2 assimilation to irradiance, partial pressure of O2, p(O2), and temperature was different at low and high intercellular p(CO2), suggesting that CO2 assimilation rate is governed by different processes at low and high intercellular p(CO2). In longer term changes in CO2 assimilation rate, induced by different growth conditions, the initial slope of the response of CO2 assimilation rate to intercellular p(CO2) could be correlated to in vitro measurements of RuP2 carboxylase activity. Also, CO2 assimilation rate at high p(CO2) could be correlated to in vitro measurements of electron transport rate. These results are consistent with the hypothesis that CO2 assimilation rate is limited by the RuP2 saturated rate of the RuP2 carboxylase-oxygenase at low intercellular p(CO2) and by the rate allowed by RuP2 regeneration capacity at high intercellular p(CO2). 相似文献
20.
Does carbon partitioning in ectomycorrhizal pine seedlings under elevated CO2 vary with fungal species? 总被引:1,自引:1,他引:0
Enhanced soil respiration in response to elevated atmospheric CO2 has been demonstrated, and ectomycorrhizal (ECM) fungi are of particular interest since they partition host-derived photoassimilates
belowground. Although a strong response of ECM fungi to elevated CO2 has been shown, little is still known about the functional diversity among species. We studied carbon (C) partitioning in
mycorrhizal Scots pine seedlings in response to short-term CO2 enrichment, using seven ECM species with different ecological strategies. Mycorrhizal associations were synthesised and seedlings
grown in large Petri dishes containing peat:vermiculite and nutrient solution for 10–15 weeks, after which half of the microcosms
were exposed to elevated CO2 treatment (710 ppm) for 15 days and the other half were kept in ambient CO2 treatment. Partitioning of C was quantified by pulse labelling the seedlings with 14CO2 and examining the distribution of labelled assimilates in shoot, root and extraradical mycelial compartments by destructive
harvest and liquid scintillation counting. Fungal biomass was determined with PLFA analysis. The respiratory loss of 14CO2 was on average greater in the elevated CO2 treatment for most species compared to the ambient CO2 treatment. More label was retrieved in the shoots in the ambient CO2 treatment compared to elevated CO2 (significant for P. involutus and P. fallax). Greater amounts of label were found in the extraradical mycelial compartment in all species (except P. involutus) in elevated CO2 compared to ambient CO2 (significant for L. bicolor, P. byssinum, P. fallax and R. roseolus). Fungal biomass production increased significantly with elevated CO2 for two species (H. velutipes and A. muscaria); three species (P. fallax, P. involutus and R. roseolus) showed a similar but non-significant trend, whereas L. bicolor and P. byssinum produced less biomass in elevated CO2 compared to ambient CO2. When 14C in the mycelial compartment and respiration was expressed per unit fungal PLFA the difference between CO2 treatments disappeared. We demonstrated that different ECM fungal isolates respond differently in C partitioning in response
to CO2 enrichment. These results suggest that under certain growth conditions, when nutrients are not limiting, ECM fungi respond
rapidly to increasing C-availability through changed biomass production and respiration. 相似文献