high temperatures and CO2
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Carbon dioxide capture and storage (CCS) is considered as one of the options for reducing CO2 emissions. CCS can be applied to large point sources of CO2, such as power plants and in large industrial processes. The CO2 capture is to produce a concentrated stream of highpressure CO2. The capture systems typically employ absorption of CO2 from flue gases with CO2 concentration up to 15 %. The oxygen-fuel systems use oxygen instead of air for fuel combustion to produce mainly water vapour and CO2 (more than 80 %); the water vapour is easily removed by cooling. In precombustion capture, the fuel is converted to CO2 (15-60 %) and H2 at high pressure; then CO2 is separated by adsorption or absorption. The emerging capture technologies require development of largescale membrane separation processes, novel absorption solvents and sorbents, membrane-absorbent systems, hightemperature oxygen transport membranes for oxygen production, oxyfuelling via chemical looping, combined reaction/ separation systems and new high-temperature materials.
BACKGROUND AND AIMS: Plants growing under elevated atmospheric CO2 concentrations often have reduced stomatal conductance and subsequently increased leaf temperature. This study therefore tested the hypothesis that under long-term elevated CO2 the temperature optima of photosynthetic processes will shift towards higher temperatures and the thermostability of the photosynthetic apparatus will increase. METHODS: The hypothesis was tested for saplings of broadleaved Fagus sylvatica and coniferous Picea abies exposed for 4-5 years to either ambient (AC; 385 µmol mol(-1)) or elevated (EC; 700 µmol mol(-1)) CO2 concentrations. Temperature response curves of photosynthetic processes were determined by gas-exchange and chlorophyll fluorescence techniques. KEY RESULTS: Initial assumptions of reduced light-saturated stomatal conductance and increased leaf temperatures for EC plants were confirmed. Temperature response curves revealed stimulation of light-saturated rates of CO2 assimilation (Amax) and a decline in photorespiration (RL) as a result of EC within a wide temperature range. However, these effects were negligible or reduced at low and high temperatures. Higher temperature optima (Topt) of Amax, Rubisco carboxylation rates (VCmax) and RL were found for EC saplings compared with AC saplings. However, the shifts in Topt of Amax were instantaneous, and disappeared when measured at identical CO2 concentrations. Higher values of Topt at elevated CO2 were attributed particularly to reduced photorespiration and prevailing limitation of photosynthesis by ribulose-1,5-bisphosphate (RuBP) regeneration. Temperature response curves of fluorescence parameters suggested a negligible effect of EC on enhancement of thermostability of photosystem II photochemistry. CONCLUSIONS: Elevated CO2 instantaneously increases temperature optima of Amax due to reduced photorespiration and limitation of photosynthesis by RuBP regeneration. However, this increase disappears when plants are exposed to identical CO2 concentrations. In addition, increased heat-stress tolerance of primary photochemistry in plants grown at elevated CO2 is unlikely. The hypothesis that long-term cultivation at elevated CO2 leads to acclimation of photosynthesis to higher temperatures is therefore rejected. Nevertheless, incorporating acclimation mechanisms into models simulating carbon flux between the atmosphere and vegetation is necessary.
- MeSH
- aklimatizace MeSH
- chlorofyl metabolismus MeSH
- fotosyntéza účinky léků fyziologie MeSH
- fotosystém II (proteinový komplex) metabolismus MeSH
- listy rostlin účinky léků fyziologie účinky záření MeSH
- oxid uhličitý farmakologie MeSH
- ribulosa-1,5-bisfosfát-karboxylasa metabolismus MeSH
- ribulosafosfáty MeSH
- semenáček účinky léků fyziologie účinky záření MeSH
- smrk účinky léků fyziologie účinky záření MeSH
- světlo MeSH
- teplota MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Diurnal courses of photosynthetic gas exchange parameters, chlorophyll a fluorescence characteristics and the de-epoxidation state of the xanthophyll cycle pigments (DEPS) were measured during the gradual acclimation of 4-year-old Norway spruce seedlings to different photosynthetic photon flux density (PPFD) and air temperature (T(air)) regimes, simulating cloudy days with moderate T(air) (LI, maximum PPFD 300 micromol m(-2)s(-1), T(air) range 15-25 degrees C), sunny days with moderate T(air) (HI, maximum PPFD 1000 micromol m(-2)s(-1), T(air) range 15-25 degrees C) and hot sunny days (HI-HT, maximum PPFD 1000 micromol m(-2)s(-1), T(air) range 20-35 degrees C). The plants were acclimated inside a growth chamber and each acclimation regime lasted for 13d. Acclimation to HI conditions led to a strong depression of the net CO(2) assimilation rates (A(N)), particularly during noon and afternoon periods. Exposure to the HI-HT regime led to a further decrease of A(N) even during the morning period. Insufficient stomatal conductance was found to be the main reason for depressed A(N) under HI and HI-HT conditions. Only slight changes of the maximum photosystem II (PSII) photochemical efficiency (F(V)/F(M)), in the range of 0.78-0.82, supported the resistance of the Norway spruce photosynthetic apparatus against PSII photoinhibition during acclimation to both HI and HI-HT conditions. The HI plants showed increased content of xanthophyll cycle pigments (VAZ) and enhanced efficiency of thermal energy dissipation within PSII (D) that closely correlated with the increased DEPS. In contrast, acclimation to the HI-HT regime resulted in a slight reduction of VAZ content and significantly diminished D and DEPS values during the entire day in comparison with HI plants. These results indicate a minor role of the xanthophyll cycle-mediated thermal dissipation in PSII photoprotection under elevated temperatures. The different contributions of the thermal dissipation and non-assimilatory electron transport pathways in PSII photoprotection during acclimation of the Norway spruce photosynthetic apparatus to excess irradiance and heat stresses are discussed.
- MeSH
- aklimatizace účinky záření MeSH
- chlorofyl metabolismus MeSH
- cirkadiánní rytmus účinky záření MeSH
- fotony MeSH
- fotosyntéza účinky záření MeSH
- fotosystém II (proteinový komplex) metabolismus MeSH
- oxid uhličitý metabolismus MeSH
- plyny metabolismus MeSH
- průduchy rostlin fyziologie účinky záření MeSH
- smrk fyziologie účinky záření MeSH
- světlo MeSH
- teplota MeSH
- xanthofyly metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Norsko MeSH
Cold acclimation modifies the photosynthetic machinery and enables plants to survive at sub-zero temperatures, whereas in warm habitats, many species suffer even at non-freezing temperatures. We have measured chlorophyll a fluorescence (ChlF) and CO2 assimilation to investigate the effects of cold acclimation, and of low temperatures, on a cold-sensitive Arabidopsis thaliana accession C24. Upon excitation with low intensity (40 µmol photons m- 2 s- 1) ~ 620 nm light, slow (minute range) ChlF transients, at ~ 22 °C, showed two waves in the SMT phase (S, semi steady-state; M, maximum; T, terminal steady-state), whereas CO2 assimilation showed a linear increase with time. Low-temperature treatment (down to - 1.5 °C) strongly modulated the SMT phase and stimulated a peak in the CO2 assimilation induction curve. We show that the SMT phase, at ~ 22 °C, was abolished when measured under high actinic irradiance, or when 3-(3, 4-dichlorophenyl)-1, 1- dimethylurea (DCMU, an inhibitor of electron flow) or methyl viologen (MV, a Photosystem I (PSI) electron acceptor) was added to the system. Our data suggest that stimulation of the SMT wave, at low temperatures, has multiple reasons, which may include changes in both photochemical and biochemical reactions leading to modulations in non-photochemical quenching (NPQ) of the excited state of Chl, "state transitions," as well as changes in the rate of cyclic electron flow through PSI. Further, we suggest that cold acclimation, in accession C24, promotes "state transition" and protects photosystems by preventing high excitation pressure during low-temperature exposure.
Biogas produced from organic wastes contains energetically usable methane and unavoidable amount of carbon dioxide. The exploitation of whole biogas energy is locally limited and utilization of the natural gas transport system requires CO2 removal or its conversion to methane. The biological conversion of CO2 and hydrogen to methane is well known reaction without the demand of high pressure and temperature and is carried out by hydrogenotrophic methanogens. Reducing equivalents to the biotransformation of carbon dioxide from biogas or other resources to biomethane can be supplied by external hydrogen. Discontinuous electricity production from wind and solar energy combined with fluctuating utilization cause serious storage problems that can be solved by power-to-gas strategy representing the production of storable hydrogen via the electrolysis of water. The possibility of subsequent repowering of the energy of hydrogen to the easily utilizable and transportable form is a biological conversion with CO2 to biomethane. Biomethanization of CO2 can take place directly in anaerobic digesters fed with organic substrates or in separate bioreactors. The major bottleneck in the process is gas-liquid mass transfer of H2 and the method of the effective input of hydrogen into the system. There are many studies with different bioreactors arrangements and a way of enrichment of hydrogenotrophic methanogens, but the system still has to be optimized for a higher efficiency. The aim of the paper is to gather and critically assess the state of a research and experience from laboratory, pilot and operational applications of carbon dioxide bioconversion and highlight further perspective fields of research.
- MeSH
- anaerobióza MeSH
- Archaea metabolismus fyziologie MeSH
- biopaliva MeSH
- bioreaktory mikrobiologie MeSH
- biotechnologie přístrojové vybavení metody MeSH
- fermentace MeSH
- methan metabolismus MeSH
- oxid uhličitý metabolismus MeSH
- průmyslová mikrobiologie metody MeSH
- vodík metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- přehledy MeSH
The effect of temperature on stomatal conductance (gs) and corresponding gas exchange parameters was studied in two tree species with contrasting leaf anatomy and ecophysiology-a broadleaf angiosperm, Populus deltoides x nigra (poplar), and a needle-leaf gymnosperm, Pinus taeda (loblolly pine). Experiments were conducted in growth chambers across a leaf temperature range of 19-48°C. Manipulations of temperature were done in well-watered and drought soil conditions and under ambient (400 ppm) and elevated (800 ppm) air CO2 concentrations. Increases in leaf temperature caused stomatal opening at both ambient and elevated [CO2]. The gs increased by 42% in poplar and by 40% in loblolly pine when leaf temperature increased from 30°C to 40°C at a vapour pressure difference of 1 kPa. Stomatal limitation to photosynthesis decreased in elevated temperature in loblolly pine but not in poplar. The ratio of net photosynthesis to gs depended on leaf temperature, especially at high temperatures. Evaporative cooling of transpiring leaves resulted in reductions in leaf temperature up to 9°C in well-watered poplar but only 1°C in drought-stressed poplar and in loblolly pine. As global mean temperatures rise and temperature extremes become more frequent and severe, understanding the effect of temperature on gs, and modelling that relationship, will become increasingly important.
Byla purifikována a charakterizována protease stabilni v organických rozpoštědlech. Její molekulová hmotnost byla stanovena pomocí SDS-PAGE a SEC na 26 kDa. Purifikovaná proteasa měla nejvyšší aktivitu při 70°C a její pH optimum bylo velmi široké (5,0 – 12.0). Po ošetření 5 mM EDTA a β-mercaptoethanolem zůstával enzym aktivní. Proteasa měla po hodinové inkubaci při 30°C v přítomnosti 20, 40 a 60 % (v/v) organických rozpouštědel, jako jsou například DMSO, DMF, aceton, ethanol, iso-propanol a toluen vyšší aktivitu a stabilitu. Proteolytická aktivita byla v přítomnosti Mn2+ iontů prokazatelně vyšší a v přítomnosti 5, 10 a 15 mM Pb2+, Zn2+, K+, Fe2+, Co2+, Cd2+, Mg2+, Ca2+, Fe3+ iontů po dobu 1h při 30°C si zachovávala více než 90 % aktivity.
In the present research, stable in organic solvent protease from a new thermophilic actinomycete isolate, was purified and characterized. The approximate molecular mass of 26 kDa was determined by SDS-PAGE and SEC. The purified protease showed maximum activity at 70°C and exhibited broad pH optimum (5.0 – 12.0). After treatment with 5 mM EDTA and β-mercaptoethanol the enzyme remained fully active. The protease showed an increased activity and stability in the presence of 20, 40 and 60 % (v/v) organic solvents such as DMSO, DMF, acetone, ethanol, iso-propanol and toluene when incubated for 1h at 30°C. The proteolytic activity was significantly enhanced in presence of Mn2+ and remained more than 90 % active in the presence of 5, 10 and 15 mM Pb2+, Zn2+, K+, Fe2+, Co2+, Cd2+, Mg2+, Ca2+, Fe3+ ions for 1h at 30°C. The kinetic constants were also determined.
The unicellular cyanobacterium Cyanothece sp. American Type Culture Collection (ATCC) 51142 is capable of performing oxygenic photosynthesis during the day and microoxic nitrogen fixation at night. These mutually exclusive processes are possible only by temporal separation by circadian clock or another cellular program. We report identification of a temperature-dependent ultradian metabolic rhythm that controls the alternating oxygenic and microoxic processes of Cyanothece sp. ATCC 51142 under continuous high irradiance and in high CO2 concentration. During the oxygenic photosynthesis phase, nitrate deficiency limited protein synthesis and CO2 assimilation was directed toward glycogen synthesis. The carbohydrate accumulation reduced overexcitation of the photosynthetic reactions until a respiration burst initiated a transition to microoxic N2 fixation. In contrast to the circadian clock, this ultradian period is strongly temperature-dependent: 17 h at 27 °C, which continuously decreased to 10 h at 39 °C. The cycle was expressed by an oscillatory modulation of net O2 evolution, CO2 uptake, pH, fluorescence emission, glycogen content, cell division, and culture optical density. The corresponding ultradian modulation was also observed in the transcription of nitrogenase-related nifB and nifH genes and in nitrogenase activities. We propose that the control by the newly identified metabolic cycle adds another rhythmic component to the circadian clock that reflects the true metabolic state depending on the actual temperature, irradiance, and CO2 availability.
- MeSH
- bakteriální proteiny genetika metabolismus MeSH
- bioreaktory mikrobiologie MeSH
- cirkadiánní rytmus genetika fyziologie MeSH
- Cyanothece genetika růst a vývoj metabolismus MeSH
- fixace dusíku genetika fyziologie MeSH
- fotosyntéza genetika fyziologie MeSH
- glykogen metabolismus MeSH
- koncentrace vodíkových iontů MeSH
- kyslík metabolismus MeSH
- oxid uhličitý metabolismus MeSH
- oxidoreduktasy genetika metabolismus MeSH
- polymerázová řetězová reakce s reverzní transkripcí MeSH
- regulace genové exprese u bakterií MeSH
- vývojová regulace genové exprese MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, U.S. Gov't, Non-P.H.S. MeSH
Wood formation consumes around 15% of the anthropogenic CO2 emissions per year and plays a critical role in long-term sequestration of carbon on Earth. However, the exogenous factors driving wood formation onset and the underlying cellular mechanisms are still poorly understood and quantified, and this hampers an effective assessment of terrestrial forest productivity and carbon budget under global warming. Here, we used an extensive collection of unique datasets of weekly xylem tissue formation (wood formation) from 21 coniferous species across the Northern Hemisphere (latitudes 23 to 67°N) to present a quantitative demonstration that the onset of wood formation in Northern Hemisphere conifers is primarily driven by photoperiod and mean annual temperature (MAT), and only secondarily by spring forcing, winter chilling, and moisture availability. Photoperiod interacts with MAT and plays the dominant role in regulating the onset of secondary meristem growth, contrary to its as-yet-unquantified role in affecting the springtime phenology of primary meristems. The unique relationships between exogenous factors and wood formation could help to predict how forest ecosystems respond and adapt to climate warming and could provide a better understanding of the feedback occurring between vegetation and climate that is mediated by phenology. Our study quantifies the role of major environmental drivers for incorporation into state-of-the-art Earth system models (ESMs), thereby providing an improved assessment of long-term and high-resolution observations of biogeochemical cycles across terrestrial biomes.
- MeSH
- biologické modely MeSH
- cévnaté rostliny genetika růst a vývoj MeSH
- dřevo růst a vývoj MeSH
- ekosystém MeSH
- fotoperioda MeSH
- globální oteplování MeSH
- klimatické změny MeSH
- lesy MeSH
- podnebí MeSH
- roční období MeSH
- stromy růst a vývoj MeSH
- teplota MeSH
- xylém růst a vývoj MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, U.S. Gov't, Non-P.H.S. MeSH
We have worked out a rapid 1-day test based on photosynthesis measurements to estimate suitable growth temperature of microalgae cultures. To verify the proposed procedure, several microalgae-Chlorella, Nostoc, Synechocystis, Scenedesmus, and Cylindrospermum-were cultured under controlled laboratory conditions (irradiance, temperature, mixing, CO2, and nutrient supply) to find the optima of photosynthetic activity using the range between 15 and 35 °C. These activities were recorded at each temperature step after 2 h of acclimation which should be sufficient as oxygen production and the PQ cycle are regulated by fast processes. Photosynthetic activity was measured using three techniques-oxygen production/respiration, saturating pulse analysis of fluorescence quenching, and fast fluorescence induction kinetics-to estimate the temperature optima which should correspond to high growth rate. We measured all variables that might have been directly related to growth-photosynthetic oxygen evolution, maximum photochemical yield of PSII, Fv/Fm, relative electron transport rate rETRmax, and the transients Vj and Vi determined by fast fluorescence induction curves. When the temperature optima for photosynthetic activity were verified in growth tests, we found good correlation. For most of tested microalgae strains, temperature around 30 °C was found to be the most suitable at this setting. We concluded that the developed test can be used as a rapid 1-day pre-screening to estimate a suitable growth temperature of microalgae strains before they are cultured in a pilot scale.
- MeSH
- Chlorella růst a vývoj metabolismus účinky záření MeSH
- fotosyntéza MeSH
- kinetika MeSH
- kultivační techniky metody MeSH
- kyslík metabolismus MeSH
- mikrořasy růst a vývoj metabolismus účinky záření MeSH
- Scenedesmus růst a vývoj metabolismus účinky záření MeSH
- sinice růst a vývoj metabolismus účinky záření MeSH
- světlo MeSH
- teplota MeSH
- Publikační typ
- časopisecké články MeSH
- hodnotící studie MeSH
