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1.
There is considerable interest in modeling isoprene emissions from terrestrial vegetation, because these emissions exert a principal control over the oxidative capacity of the troposphere. We used a unique field experiment that employs a continuous gradient in CO2 concentration from 240 to 520 ppmv to demonstrate that isoprene emissions in Eucalyptus globulus were enhanced at the lowest CO2 concentration, which was similar to the estimated CO2 concentrations during the last Glacial Maximum, compared with 380 ppmv, the current CO2 concentration. Leaves of Liquidambar styraciflua did not show an increase in isoprene emission at the lowest CO2 concentration. However, isoprene emission rates from both species were lower for trees grown at 520 ppmv CO2 compared with trees grown at 380 ppmv CO2. When grown in environmentally controlled chambers, trees of Populus deltoides and Populus tremuloides exhibited a 30–40% reduction in isoprene emission rate when grown at 800 ppmv CO2, compared with 400 ppmv CO2. P. tremuloides exhibited a 33% reduction when grown at 1200 ppmv CO2, compared with 600 ppmv CO2. We used current models of leaf isoprene emission to demonstrate that significant errors occur if the CO2 inhibition of isoprene is not taken into account. In order to alleviate these errors, we present a new model of isoprene emission that describes its response to changes in atmospheric CO2 concentration. The model logic is based on assumed competition between cytosolic and chloroplastic processes for pyruvate, one of the principal substrates of isoprene biosynthesis.  相似文献   

2.
Aims:  The objective of this study is to develop kinetic models based on batch experiments describing the growth, CO2 consumption, and H2 production of Anabaena variabilis ATCC 29413-UTM as functions of irradiance and CO2 concentration.
Methods and Results:  A parametric experimental study is performed for irradiances from 1120 to 16100 lux and for initial CO2 mole fractions from 0·03 to 0·20 in argon at pH 7·0 ± 0·4 with nitrate in the medium. Kinetic models are successfully developed based on the Monod model and on a novel scaling analysis employing the CO2 consumption half-time as the time scale.
Conclusions:  Monod models predict the growth, CO2 consumption and O2 production within 30%. Moreover, the CO2 consumption half-time is an appropriate time scale for analysing all experimental data. In addition, the optimum initial CO2 mole fraction is 0·05 for maximum growth and CO2 consumption rates. Finally, the saturation irradiance is determined to be 5170 lux for CO2 consumption and growth whereas, the maximum H2 production rate occurs around 10 000 lux.
Significance and Impact of the Study:  The study presents kinetic models predicting the growth, CO2 consumption and H2 production of A. variabilis . The experimental and scaling analysis methods can be generalized to other micro-organisms.  相似文献   

3.
The net ecosystem CO2 exchange (NEE) between a Mojave Desert ecosystem and the atmosphere was measured over the course of 2 years at the Mojave Global Change Facility (MGCF, Nevada, USA) using the eddy covariance method. The investigated desert ecosystem was a sink for CO2, taking up 102±67 and 110±70 g C m−2 during 2005 and 2006, respectively. A comprehensive uncertainty analysis showed that most of the uncertainty of the inferred sink strength was due to the need to account for the effects of air density fluctuations on CO2 densities measured with an open-path infrared gas analyser. In order to keep this uncertainty within acceptable bounds, highest standards with regard to maintenance of instrumentation and flux measurement postprocessing have to be met. Most of the variability in half-hourly NEE was explained by the amount of incident photosynthetically active radiation (PAR). On a seasonal scale, PAR and soil water content were the most important determinants of NEE. Precipitation events resulted in an initial pulse of CO2 to the atmosphere, temporarily reducing NEE or even causing it to switch sign. During summer, when soil moisture was low, a lag of 3–4 days was observed before the correlation between NEE and precipitation switched from positive to negative, as opposed to conditions of high soil water availability in spring, when this transition occurred within the same day the rain took place. Our results indicate that desert ecosystem CO2 exchange may be playing a much larger role in global carbon cycling and in modulating atmospheric CO2 levels than previously assumed – especially since arid and semiarid biomes make up >30% of Earth's land surface.  相似文献   

4.
Increased root exudation under elevated atmospheric CO2 and the contrasting environments in soil macro- and microaggregates could affect microbial growth strategies. We investigated the effect of elevated CO2 on the contribution of fast- ( r -strategists) and slow-growing ( K -strategists) microorganisms in soil macro- and microaggregates. We fractionated the bulk soil from the ambient and elevated (for 5 years) CO2 treatments of FACE-Hohenheim (Stuttgart) into large macro- (>2 mm), small macro- (0.25–2.00 mm), and microaggregates (<0.25 mm) using 'optimal moist' sieving. Microbial biomass (Cmic), the maximum specific growth rate (μ), growing microbial biomass (GMB) and lag-period ( t lag) were estimated by the kinetics of CO2 emission from bulk soil and aggregates amended with glucose and nutrients. Although Corg and Cmic were unaffected by elevated CO2, μ values were significantly higher under elevated than ambient CO2 for bulk soil, small macroaggregates, and microaggregates. Substrate-induced respiratory response increased with decreasing aggregate size under both CO2 treatments. Based on changes in μ, GMB and lag period, we conclude that elevated atmospheric CO2 stimulated the r- selected microorganisms, especially in soil microaggregates. Such an increase in r -selected microorganisms indicates acceleration of available C mineralization in soil, which may counterbalance the additional C input by roots in soils in a future elevated atmospheric CO2 environment.  相似文献   

5.
Abstract In this study we show a link between the respiratory method and state of hydration in an arid dwelling tenebrionid beetle ( Pimelia grandis ). Dehydrated beetles use discontinuous gas exchange cycles with a flutter period consisting of several discrete bursts of CO2 release, whereas beetles given access to food and water showed a form of continuous CO2 release. These data give support to the respiratory water conservation hypothesis for the discontinuous gas exchange cycle.  相似文献   

6.
Abstract. A portable apparatus has been constructed to measure simultaneously the quantum yield of CO2 assimilation, light absorption, chlorophyll fluorescence emission and water vapour exchange of attached intact leaves in the field. The core of the instrument is a light-integrating spherical leaf chamber which includes ports for a light source, photosynthetically active radiation sensor, fluorescence probes and gas inlet and outlet manifolds. Measurement of the quantum flux inside the empty chamber and with a leaf present allows determination of leaf absorptance. An open gas exchange system is employed using an infra-red analyser to measure leaf CO2 exchange. Using a DC white light source the quantum yield of CO2 assimilation based on absorbed light (φabs) may be determined rapidly in either ambient air or artificial gas mixtures. Inclusion of capacitance humidity probes into the gas inlet and outlet ports allows simultaneous determination of water vapour exchange and subsequent estimation of stomatal conductance to CO2 and intercellular CO2 concentration. Measurement of fluorescence emission by the sample leaf exposed to white light is achieved by a modulated fluorescence detection system. In addition to determination of the minimal, maximal and variable fluorescence levels, a further analysis allows the photochemical and non-photochemical components of fluorescence quenching, to be estimated. The theory and design of this apparatus is described in detail. The use of the apparatus in the field is demonstrated through a study of the photosynthetic performance of a maize and bean crop during the growing season and by analysis of the photosynthetic performance of crops subjected to nitrogen-stress and a herbicide treatment.  相似文献   

7.
Discontinuous gas exchange cycles (DGCs), active muscular ventilation, microcycles of repetitive openings, and heartbeats of diapausing adult Colorado potato beetle, Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae), were studied at low temperatures (0, 5, and 10 °C) using an electrolytic respirometer combined with an infrared actograph. The DGC of the adult constriction-flutter-open type was the main respiration mode in fully quiescent beetles at temperatures from 5 to 10 °C. The CO2 bursts were actively ventilated at temperatures above 5 °C. During the flutter period, a series of microcycles appeared, but no muscular contractions associated with the microcycles were detected. We identified this respiration mode as discontinuous suction ventilation.
The hydration condition of the beetles did not influence the frequency of the gas exchange cycles, but dehydrated beetles showed significantly longer flutter periods and shorter ventilation periods than hydrated beetles. The heartbeat frequencies were influenced by both temperature and hydration status.
We conclude from the results that DGCs are used at rest in adult L. decemlineata under various environmental conditions and also at low temperatures. Our results showed that DGCs are the main respiration mode of resting adult Colorado potato beetle irrespective of its hydration state and temperature. Our method resolves O2 uptake and subsequent CO2 release in flutter and ventilation periods and shows that diffusion is replaced by convection to reduce water loss in adult beetles.  相似文献   

8.
Abstract.  Metabolic rate variation with temperature, body mass, gender and feeding status is documented for Glossina morsitans centralis . Metabolic rate [mean ± SE; VCO2= 19.78 ± 3.11 μL CO2 h−1 in males (mean mass = 22.72 ± 1.41 mg) and 27.34 ± 3.86 μL CO2 h−1 in females (mean mass = 29.28 ± 1.96 mg) at 24 °C in fasted individuals] is strongly influenced by temperature, body mass and feeding status, but not by gender once the effects of body mass have been accounted for. A significant interaction between gender and feeding status is seen, similar to patterns of metabolic rate variation documented in Glossina morsitans morsitans . Synthesis of metabolic rate-temperature relationships in G. m. centralis , G. m. morsitans and Glossina pallidipes indicate that biting frequency as well as mortality risks associated with foraging will probably increase with temperature as a consequence of increasing metabolic demands, although there is little evidence for variation among species at present. Furthermore, metabolic rate–body mass relationships appear to be similarly invariant among these species. These data provide important physiological information for bottom-up modelling of tsetse fly population dynamics.  相似文献   

9.
Abstract. A controlled-environment chamber constructed from a standard chest freezer was used to grow and measure the CO2 exchange of small stands of lettuce ( Lactuca sativa L. ev. Ambassador). The chamber, with horizontal air flow, provided good control of air temperature ( c. 6 to 16°C), irradiance (0–300 μmol PAR m 2S1 and CO2 (350–1000 μmol mol−1). The photosynthetic response to changes in these variables was measured using an inexpensive CO2 dosing system which recorded the input rate required to maintain a constant concentration of CO2 (to ± 2.5%). Characteristis of the growth environment and the changes in response to temperature and irradiance are described.  相似文献   

10.
We present field observations of carbon isotope discrimination (Δ) and internal conductance of CO2 ( g i) collected using tunable diode laser spectroscopy (TDL). Δ ranged from 12.0 to 27.4‰ over diurnal periods with daily means from 16.3 ± 0.2‰ during drought to 19.0 ± 0.5‰ during monsoon conditions. We observed a large range in g i, with most estimates between 0.04 and 4.0  µ mol m−2 s−1 Pa−1. We tested the comprehensive Farquhar, O'Leary and Berry model of Δ (Δcomp), a simplified form of Δcompsimple) and a recently suggested amendment (Δrevised). Sensitivity analyses demonstrated that varying g i had a substantial effect on Δcomp, resulting in mean differences between observed Δ (Δobs) and Δcomp ranging from 0.04 to 9.6‰. First-order regressions adequately described the relationship between Δ and the ratio of substomatal to atmospheric CO2 partial pressure ( p i/ p a) on all 3 d, but second-order models better described the relationship in July and August. The three tested models each best predicted Δobs on different days. In June, Δsimple outperformed Δcomp and Δrevised, but incorporating g i and all non-photosynthetic fractionations improved model predictions in July and August.  相似文献   

11.
The effect of elevated [CO2] on wheat (Triticum aestivum L. Veery 10) productivity was examined by analysing radiation capture, canopy quantum yield, canopy carbon use efficiency, harvest index and daily C gain. Canopies were grown at either 330 or 1200 μ mol mol–1[CO2] in controlled environments, where root and shoot C fluxes were monitored continuously from emergence to harvest. A rapidly circulating hydroponic solution supplied nutrients, water and root zone oxygen. At harvest, dry mass predicted from gas exchange data was 102·8 ± 4·7% of the observed dry mass in six trials. Neither radiation capture efficiency nor carbon use efficiency were affected by elevated [CO2], but yield increased by 13% due to a sustained increase in canopy quantum yield. CO2 enrichment increased root mass, tiller number and seed mass. Harvest index and chlorophyll concentration were unchanged, but CO2 enrichment increased average life cycle net photosynthesis (13%, P < 0·05) and root respiration (24%, P < 0·05). These data indicate that plant communities adapt to CO2 enrichment through changes in C allocation. Elevated [CO2] increases sink strength in optimal environments, resulting in sustained increases in photosynthetic capacity, canopy quantum yield and daily C gain throughout the life cycle.  相似文献   

12.
Stomatal behaviour, photosynthesis and transpiration under rising CO2   总被引:2,自引:2,他引:0  

Definitions of the variables used and the units are given in Table 1

The literature reports enormous variation between species in the extent of stomatal responses to rising CO2. This paper attempts to provide a framework within which some of this diversity can be explained. We describe the role of stomata in the short-term response of leaf gas exchange to increases in ambient CO2 concentration by developing the recently proposed stomatal model of Jarvis & Davies (1998 ). In this model stomatal conductance is correlated with the functioning of the photosynthetic system so that the effects of increases in CO2 on stomata are experienced through changes in the rate of photosynthesis in a simple and mechanistically transparent way. This model also allows us to consider the effects of evaporative demand and soil moisture availability on stomatal responses to photosynthesis and therefore provides a means of considering these additional sources of variation. We emphasize that the relationship between the rate of photosynthesis and the internal CO2 concentration and also drought will have important effects on the relative gains to be achieved under rising CO2.  

  Table 1 . Abbreviations  相似文献   


13.
Abstract. Studies of the isoprene emission rate in response to changes in photon-flux density and CO2 partial pressure were conducted using a recently developed on-line isoprene analyser combined with a gas exchange system and chlorophyll fluorometer. Upon darkening, the isoprene emission rate from leaves of aspen ( Populus tremuloides Michaux.) began to decline immediately, demonstrating that the internal pool of isoprene, or its precursors, is small and that the instantaneous emission rate is tightly coupled to the rate of synthesis. A post-illumination burst of isoprene was observed within 5 min after darkening and lasted for 15–20 min in four isoprene-emitting species that were examined. In leaves of eucalyptus ( Eucalyptus globulus Labill.), the magnitude of the post-illumination burst was dependent on the photon-flux density that existed before darkening, but not on ambient CO2 partial pressure. The dependence of the post-illumination burst on photon-flux density paralleled that for the steady-state rate of isoprene emission. A step-wise increase in intercellular CO2 partial pressure from 24.5 to 60 Pa resulted in an immediate decrease in isoprene emission rate and non-photochemical fluorescence quenching, but an increase in CO2 assimilation rate. Given the several recent studies that link isoprene emission to chloroplastic processes, the results of this study indicate that the linkage is not dependent on the rate of CO2 flux through the reductive pentose phosphate pathway, but rather on more complex relationships involving metabolites not appreciably influenced by CO2 partial pressure.  相似文献   

14.
Calcite nucleation on the surface of cyanobacteria of the Synechococcus leopoliensis strain PCC 7942 was investigated to assess the influence of photosynthetic uptake of inorganic carbon and active ion exchange processes across the cell membrane on the nucleation and precipitation mechanisms. We performed long-term precipitation experiments at a constant CO2 level in ambient air by adding suspensions of previously washed cyanobacteria to solutions of NaHCO3/CaCl2 which were supersaturated with respect to calcite. Induction times between 4 and 110 h were measured over a range of saturation states, Ω, between 8 and 4. The kinetics of CaCO3 nucleation was compared between experiments: (i) with ongoing photosynthesis, (ii) with cells metabolizing but not undergoing photosynthetic uptake of inorganic carbon and (iii) in darkness without photosynthesis. No significant differences were observed between the three treatments. The results reveal that under low nutrient concentrations and permanent CO2 supply, photosynthetic uptake of inorganic carbon predominantly uses CO2 and consequently does not directly influence the nucleation process of CaCO3 at the surface of S. leopoliensis. Furthermore, ion exchange processes did not affect the kinetics, indicating a passive nucleation process wherein the cell surface or extracellular polymers provided preferential sites for mineral nucleation. The catalyzing effect of the cyanobacteria on calcite nucleation was equivalent to a ∼18% reduction in the specific interfacial free energy of the calcite nuclei. This result and the ubiquitous abundance of cyanobacteria suggest that this process may have an impact on local and global carbon cycling.  相似文献   

15.
Measurements of photosynthesis and respiration in plants   总被引:6,自引:1,他引:5  
Hunt S 《Physiologia plantarum》2003,117(3):314-325
Methods for measuring the rates of photosynthesis and respiration in plants are reviewed. Closed systems that involve manometric techniques, 14CO2 fixation, O2 electrodes and other methods for measuring dissolved and gas phase O2 are described. These methods typically provide time-integrated rate measurements, and limitations to their use are discussed. Open gas exchange systems that use infra-red CO2 gas analysers and differential O2 analysers for measuring instantaneous rates of CO2 and O2 exchange are described. Important features of the analysers, design features of gas exchange systems, and sources of potential error are considered. The analysis of chlorophyll fluorescence parameters for estimating the quantum yield for O2 evolution and CO2 fixation is described in relation to new fluorescence imaging systems for large scale screening of photosynthetic phenotypes, and the microimaging of individual chloroplasts.  相似文献   

16.
Nitric oxide (NO) is an endogenous signalling molecule implicated in a growing number of plant processes and has been recognised as a plant hormone. The present research employed spinach plant ( Spinacia oleracea cv. Huangjia) and closed growth chambers to investigate the effects of gaseous NO application on vegetable production in greenhouses. Treatment of low concentration of NO gas (ambient atmosphere with 200 nL L−1 NO gas) significantly increased the shoot biomass of the soil-cultivated plants as compared with the control treatment (ambient atmosphere). In addition, the NO treatment also increased the photosynthetic rate of leaves, indicating that the enhancement of photosynthesis is an important reason leading to more biomass accumulation induced by NO gas. Furthermore, the NO treatment decreased nitrate concentration but increased the concentrations of soluble sugar, protein, antioxidants (vitamin C, glutathione and flavonoids), and ferric reducing-antioxidant power (FRAP) in shoots of the plants grown in soil, suggesting that the gaseous NO treatment can not only increase vegetable production but also improve vegetable quality. In addition, the effects of the combined application of NO and CO2 (NO 200 nL L−1 and CO2 800 μL L−1) on shoot biomass was even greater than the effects of elevated CO2 (CO2 800 μL L−1) or the NO treatment alone, implying that gaseous NO treatment can be used in CO2-elevated greenhouses as an effective strategy in improving vegetable production.  相似文献   

17.
Ecosystem flux measurements using the eddy covariance (EC) technique were undertaken in 4 subsequent years during summer for a total of 562 days in an arctic wet tundra ecosystem, located near Cherskii, Far-Eastern Federal District, Russia. Methane (CH4) emissions were measured using permanent chambers. The experimental field is characterized by late thawing of permafrost soils in June and periodic spring floods. A stagnant water table below the grass canopy is fed by melting of the active layer of permafrost and by flood water. Following 3 years of EC measurements, the site was drained by building a 3 m wide drainage channel surrounding the EC tower to examine possible future effects of global change on the tundra tussock ecosystem. Cumulative summertime net carbon fluxes before experimental alteration were estimated to be about +15 g C m−2 (i.e. an ecosystem C loss) and +8 g C m−2 after draining the study site. When taking CH4 as another important greenhouse gas into account and considering the global warming potential (GWP) of CH4 vs. CO2, the ecosystem had a positive GWP during all summers. However CH4 emissions after drainage decreased significantly and therefore the carbon related greenhouse gas flux was much smaller than beforehand (475 ± 253 g C-CO2-e m−2 before drainage in 2003 vs. 23 ± 26 g C-CO2-e m−2 after drainage in 2005).  相似文献   

18.
A recognized invasive weed, Canada thistle ( Cirsium arvense L. Scop.) was grown at ambient and pre-ambient concentrations of atmospheric carbon dioxide [CO2] (373 and 287 μmol mol−1, respectively) at three levels of supplemental nitrogen (N) (3, 6 and 14.5 m M ) from seeding until flowering [77 days after sowing (DAS)]. The primary objective of the study was to determine if N supply limited the potential photosynthetic and growth response of this species to the increase in atmospheric [CO2] which occurred during the 20th century (i.e. approximately 290 to 370 μmol mol−1 CO2). Leaf photosynthesis increased both as a function of growth [CO2] and N supply during the first 46 DAS. Although by 46 DAS photosynthetic acclimation was observed relative to a common measurement CO2 concentration, there was no interaction with N supply. Both [CO2] and N increased biomass, relative growth rates and leaf area whereas root : shoot ratio was increased by CO2 and decreased by increasing N; however, N supply did not effect the relative response to [CO2] for any measured vegetative parameter up to 77 DAS. Due to the relative stimulation of shoot biomass, total above-ground N increased at elevated [CO2] for all levels of supplemental N, but nitrogen use efficiency (NUE) did not differ as a function of [CO2]. Overall, these data suggest that any potential response to increased atmospheric [CO2] in recent decades for this noxious weedy species was probably not limited by nitrogen supply.  相似文献   

19.
Abstract: Two populations of the psocid, Liposcelis bostrychophila Badonnel, were exposed to two CO2-enriched atmospheres (35% CO2 + 21% O2, and 55% CO2 + 21% O2, balance N2) for 30 generations. Controls were reared in normal atmospheres. The reserves of triacylglycerol and polysaccharides were evaluated in adults of the two experimental and the control populations in generations F15 and F30. The utilization rate of triacylglycerol and polysaccharides in the CO2-enriched atmospheres were also determined in generation F30. The results indicated that the reserves of triacylglycerol and polysaccharides increased significantly during selection for CO2 resistance; the higher the resistance level, the greater the reserves. Exposure of these populations to controlled atmosphere was associated with a steady utilization of the reserves. By contrast, the unselected population responded to controlled atmospheres by accelerated utilization of triacylglycerol and polysaccharides. Comparison of the utilization rates during CO2 exposure showed that triacylglycerol is the main energy source, and polysaccharides contribute to metabolic energy supply only to a small extent.  相似文献   

20.
Ecosystem CO2 and N2O exchanges between soils and the atmosphere play an important role in climate warming and global carbon and nitrogen cycling; however, it is still not clear whether the fluxes of these two greenhouse gases are correlated at the ecosystem scale. We collected 143 pairs of ecosystem CO2 and N2O exchanges between soils and the atmosphere measured simultaneously in eight ecosystems around the world and developed relationships between soil CO2 and N2O fluxes. Significant linear regressions of soil CO2 and N2O fluxes were found for all eight ecosystems; the highest slope occurred in rice paddies and the lowest in temperate grasslands. We also found the dominant role of growing season on the relationship of annual CO2 and N2O fluxes. No significant relationship between soil CO2 and N2O fluxes was found across all eight ecosystem types. The estimated annual global N2O emission based on our findings is 13.31 Tg N yr−1 with a range of 8.19–18.43 Tg N yr−1 for 1980–2000, of which cropland contributes nearly 30%. Our findings demonstrated that stoichiometric relationships may work on ecological functions at the ecosystem level. The relationship of soil N2O and CO2 fluxes developed here could be helpful in biogeochemical modeling and large-scale estimations of soil CO2 and N2O fluxes.  相似文献   

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