共查询到20条相似文献,搜索用时 31 毫秒
1.
Wen Min Huang Hui Shao Si Ning Zhou Qin Zhou Wen Long Fu Ting Zhang Hong Sheng Jiang Wei Li Brigitte Gontero Stephen C. Maberly 《Photosynthesis research》2018,138(2):219-232
The freshwater macrophyte, Ottelia alismoides, is a bicarbonate user performing C4 photosynthesis in the light, and crassulacean acid metabolism (CAM) when acclimated to low CO2. The regulation of the three mechanisms by CO2 concentration was studied in juvenile and mature leaves. For mature leaves, the ratios of phosphoenolpyruvate carboxylase (PEPC) to ribulose-bisphosphate carboxylase/oxygenase (Rubisco) are in the range of that of C4 plants regardless of CO2 concentration (1.5–2.5 at low CO2, 1.8–3.4 at high CO2). In contrast, results for juvenile leaves suggest that C4 is facultative and only present under low CO2. pH-drift experiments showed that both juvenile and mature leaves can use bicarbonate irrespective of CO2 concentration, but mature leaves have a significantly greater carbon-extracting ability than juvenile leaves at low CO2. At high CO2, neither juvenile nor mature leaves perform CAM as indicated by lack of diurnal acid fluctuation. However, CAM was present at low CO2, though the fluctuation of titratable acidity in juvenile leaves (15–17 µequiv g?1 FW) was slightly but significantly lower than in mature leaves (19–25 µequiv g?1 FW), implying that the capacity to perform CAM increases as leaves mature. The increased CAM activity is associated with elevated PEPC activity and large diel changes in starch content. These results show that in O. alismoides, carbon-dioxide concentrating mechanisms are more effective in mature compared to juvenile leaves, and C4 is facultative in juvenile leaves but constitutive in mature leaves. 相似文献
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3.
The net photosynthetic rate (P N), the sample room CO2 concentration (CO2S) and the intercellular CO2 concentration (C i) in response to PAR, of C3 (wheat and bean) and C4 (maize and three-colored amaranth) plants were measured. Results showed that photorespiration (R p) of wheat and bean could not occur at 2 % O2. At 2 % O2 and 0 μmol mol?1 CO2, P N can be used to estimate the rate of mitochondrial respiration in the light (R d). The R d decreased with increasing PAR, and ranged between 3.20 and 2.09 μmol CO2 m?2 s?1 in wheat. The trend was similar for bean (between 2.95 and 1.70 μmol CO2 m?2 s?1), maize (between 2.27 and 0.62 μmol CO2 m?2 s?1) and three-colored amaranth (between 1.37 and 0.49 μmol CO2 m?2 s?1). The widely observed phenomenon of R d being lower than R n can be attributed to refixation, rather than light inhibition. For all plants tested, CO2 recovery rates increased with increasing light intensity from 32 to 55 % (wheat), 29 to 59 % (bean), 54 to 87 % (maize) and 72 to 90 % (three-colored amaranth) at 50 and 2,000 μmol m?2 s?1, respectively. 相似文献
4.
We evaluated the nighttime CO2 flux (ecosystem respiration) on Rishiri Island, located at the northern tip of Hokkaido, Japan, from 2009 to 2011, by using the relationship between atmospheric 222Rn and CO2 concentrations. The annual mean CO2 flux was 1.8 μmol m?2 s?1, with a maximum monthly mean in July (4.6 ± 2.6 μmol m?2 s?1) and a broad minimum from December to March (0.33 ± 0.29 μmol m?2 s?1). The annual mean was comparable to fluxes at the JapanFlux sites in northern Japan. During the season of snow cover (mid-December to early April), the CO2 flux was low (0.45 ± 0.43 μmol m?2 s?1). Total annual respiration was estimated at 679 ± 174 g cm?2, about 8 % of which occurred during the season of snow cover. 相似文献
5.
Ruchi Singh Sanjay Ranjan Sanjeeva Nayaka Uday V. Pathre Pramod A. Shirke 《Acta Physiologiae Plantarum》2013,35(5):1605-1615
Stereocaulon foliolosum a fruticose type of lichen under its natural habitat is subjected to low temperature, high light conditions and frequent moisture stress due its rocky substratum. To understand as to how this lichen copes up with these stresses, we studied the reflectance properties, light utilization capacity and the desiccation tolerance under laboratory conditions. S. foliolosum showed light saturation point for photosynthesis at 390 μmol CO2 m?2 s?1 and the light compensation point for photosynthesis at 64 μmol CO2 m?2 s?1. Our experiments show that S. foliolosum has a low absorptivity (30–35 %) towards the incident light. The maximum rates of net photosynthesis and apparent electron transport observed were 1.9 μmol CO2 m?2 s?1 and 45 μmol e? m?2 s?1, respectively. The lichen recovers immediately after photoinhibition under low light conditions. S. foliolosum on subjecting to desiccation results in the decrease of light absorptivity and the reflectance properties associated with water status of the thalli show a change. During desiccation, a simultaneous decrease in photosynthesis, dark respiration and quenching in the fluorescence properties was observed. However, all the observed changes show a rapid recovery on rewetting the lichen. Our study shows that desiccation does not have a severe or long-term impact on S. foliolosum and the lichen is also well adapted to confront high light intensities. 相似文献
6.
Do short-term fluctuations in CO2 concentrations at elevated CO2 levels affect net CO2 uptake rates of plants? When exposed to 600 μl CO2 l?1, net CO2 uptake rates in shoots or leaves of seedlings of two tropical C3 tree species, teak (Tectona grandis L. f.) and barrigon [Pseudobombax septenatum (Jacq.) Dug.], increased by 28 and 52% respectively. In the presence of oscillations with half-cycles of 20 s, amplitude of ca. 170 μl CO2 l?1 and mean of 600 μl CO2 l?1, the stimulation in net CO2 uptake by the two species was reduced to 19 and 36%, respectively, i.e. the CO2 stimulation in photosynthesis associated with a change in exposure from 370 to 600 μl CO2 l?1 was reduced by a third in both species. Similar reductions in CO2-stimulated net CO2 uptake were observed in T. grandis exposed to 40-s oscillations. Rates of CO2 efflux in the dark by whole shoots of T. grandis decreased by 4.8% upon exposure of plants grown at 370 μl CO2 l?1 to 600 μl CO2 l?1. The potential implications of the observations on CO2 oscillations and dark respiration are discussed in the context of free-air CO2 enrichment (FACE) systems in which short-term fluctuations of CO2 concentration are a common feature. 相似文献
7.
Raquel Pedrosa Bezerra Marcelo Chuei Matsudo Sunao Sato Attilio Converti João Carlos Monteiro de Carvalho 《Bioenergy Research》2013,6(3):1118-1125
To reduce CO2 emissions from alcoholic fermentation, Arthrospira platensis was cultivated in tubular photobioreactor using either urea or nitrate as nitrogen sources at different light intensities (60 μmol m?2 s?1?≤?I?≤?240 μmol m?2 s?1). The type of carbon source (pure CO2 or CO2 from fermentation) did not show any appreciable influence on the main cultivation parameters, whereas substitution of nitrate for urea increased the nitrogen-to-cell conversion factor (Y X/N ), and the maximum cell concentration (X m ) and productivity (P X ) increased with I. As a result, the best performance using gaseous emissions from alcoholic fermentation (X m ?=?2,960?±?35 g m?3, P X ?=?425?±?5.9 g m?3 day?1 and Y X/N ?=?15?±?0.2 g g?1) was obtained at I?=?120 μmol m?2 s?1 using urea as nitrogen source. The results obtained in this work demonstrate that the combined use of effluents rich in urea and carbon dioxide could be exploited in large-scale cyanobacteria cultivations to reduce not only the production costs of these photosynthetic microorganisms but also the environmental impact associated to the release of greenhouse emissions. 相似文献
8.
Indigenous broadleaf plantations are increasingly developing as a prospective silvicultural management approach for substituting in place of large pure conifer plantations in subtropical China. However, little information is known about the effects of tree species conversion on soil-atmosphere greenhouse gas (GHG) exchanges. Four adjacent monospecific plantations were selected in subtropical China to examine the effects of tree species on soil-atmosphere exchanges of N2O, CH4 and CO2. One coniferous plantation was composed of Pinus massoniana (PM), and the three broadleaf plantations were Castanopsis hystrix (CH), Michelia macclurei (MM) and Mytilaria laosensis (ML). We found that mean soil N2O and CO2 emissions in the PM plantation were 4.34 μg N m?2?h?1 and 43.25 mg C m?2?h?1, respectively, lower than those in the broadleaf plantations (>5.25 μg N m?2?h?1 and >56.38 mg C m?2?h?1). The PM plantation soil had higher mean CH4 uptake (39.03 μg C m?2?h?1) than the broadleaf plantation soils (<32.67 μg C m?2?h?1). Variations in soil N2O emissions among tree species could be primarily explained by the differences in litter C:N ratio and soil total N stock. Differences in soil CH4 uptake among tree species could be mostly attributed to the differences in mean soil CO2 flux and water filled pore space (WFPS). Litter C:N ratio could largely account for variations in soil CO2 emissions among tree species. This study confirms that there is no GHG benefit of converting PM plantation to broadleaf plantations in subtropical China. Therefore, the future strategy of tree species selection for substituting in place of large coniferous plantations in subtropical China needs to consider the potential effects of tree species on soil-atmosphere GHG exchanges. 相似文献
9.
M. Oviya V. Sukumaran Sib Sankar Giri 《World journal of microbiology & biotechnology》2013,29(10):1813-1820
The present investigation entails the immobilisation and characterisation of Escherichia coli MO1-derived carbonic anhydrase (CA) and its influence on the transformation of CO2 to CaCO3. CA was purified from MO1 using a combination of Sephadex G-75 and DEAE cellulose column chromatography, resulting in 4.64-fold purification. The purified CA was immobilised in chitosan-alginate polyelectrolyte complex (C-A PEC) with an immobilisation potential of 94.5 %. Both the immobilised and free forms of the enzyme were most active and stable at pH 8.2 and at 37 °C. The K m and V max of the immobilised enzyme were found to be 19.12 mM and 416.66 μmol min?1 mg?1, respectively; whereas, the K m and V max of free enzyme were 18.26 mM and 434.78 μmol min?1 mg?1, respectively. The presence of metal ions such as Cu2+, Fe2+, and Mg2+ stimulated the enzyme activity. Immobilised CA showed higher storage stability and maintained its catalytic efficiency after repeated operational cycles. Furthermore, both forms of the enzyme were tested for targeted application of the carbonation reaction to convert CO2 to CaCO3. The amounts of CaCO3 precipitated over free and immobilised CA were 267 and 253 mg/mg of enzyme, respectively. The results of this study show that immobilised CA in chitosan-alginate beads can be useful for CO2 sequestration by the biomimetic route. 相似文献
10.
Ling Lian Xiaowei Wang Yongsheng Zhu Wei He Qiuhua Cai Huaan Xie Muqing Zhang Jianfu Zhang 《Molecular biology reports》2014,41(4):2189-2197
Phosphoenolpyruvate carboxylase (PEPC) is known to play a key role in the initial fixation of CO2 in C4 photosynthesis. The PEPC gene from sugarcane (a C4 plant) was introduced into indica rice (Hang2), a process mediated by Agrobacterium tumefaciens. Integration patterns and copy numbers of the gene was confirmed by DNA blot analysis. RT-PCR and western blotting results showed that the PEPC gene was expressed at both the mRNA and protein levels in the transgenic lines. Real-time PCR results indicated that expression of the sugarcane PEPC gene occurred mostly in green tissues and changed under high temperature and drought stress. All transgenic lines showed higher PEPC enzyme activities compared to the untransformed controls, with the highest activity (11.1 times higher than the controls) being observed in the transgenic line, T34. The transgenic lines also exhibited higher photosynthetic rates. The highest photosynthetic rate was observed in the transgenic line, T54 (22.3 μmol m?2 s?1; 24.6 % higher than that in non-transgenic plants) under high-temperature conditions. Furthermore, the filled grain and total grain numbers for transgenic lines were higher than those for non-transgenic plants, but the grain filling (%) and 1,000-grain weights of all transgenic lines remained unchanged. We concluded that over-expression of the PEPC gene from sugarcane in indica rice (Hang2) resulted in higher PEPC enzyme activities and higher photosynthesis rates under high-temperature conditions. 相似文献
11.
Daniel L. Warner Samuel Villarreal Kelsey McWilliams Shreeram Inamdar Rodrigo Vargas 《Ecosystems》2017,20(6):1205-1216
Forest soils and canopies are major components of ecosystem CO2 and CH4 fluxes. In contrast, less is known about coarse woody debris and living tree stems, both of which function as active surfaces for CO2 and CH4 fluxes. We measured CO2 and CH4 fluxes from soils, coarse woody debris, and tree stems over the growing season in an upland temperate forest. Soils were CO2 sources (4.58 ± 2.46 µmol m?2 s?1, mean ± 1 SD) and net sinks of CH4 (?2.17 ± 1.60 nmol m?2 s?1). Coarse woody debris was a CO2 source (4.23 ± 3.42 µmol m?2 s?1) and net CH4 sink, but with large uncertainty (?0.27 ± 1.04 nmol m?2 s?1) and with substantial differences depending on wood decay status. Stems were CO2 sources (1.93 ± 1.63 µmol m?2 s?1), but also net CH4 sources (up to 0.98 nmol m?2 s?1), with a mean of 0.11 ± 0.21 nmol m?2 s?1 and significant differences depending on tree species. Stems of N. sylvatica, F. grandifolia, and L. tulipifera consistently emitted CH4, whereas stems of A. rubrum, B. lenta, and Q. spp. were intermittent sources. Coarse woody debris and stems accounted for 35% of total measured CO2 fluxes, whereas CH4 emissions from living stems offset net soil and CWD CH4 uptake by 3.5%. Our results demonstrate the importance of CH4 emissions from living stems in upland forests and the need to consider multiple forest components to understand and interpret ecosystem CO2 and CH4 dynamics. 相似文献
12.
In the early nineties, Undaria pinnatifida has been accidentally introduced to Nuevo Gulf (Patagonia, Argentina) where the environmental conditions would have favored its expansion. The effect of the secondary treated sewage discharge from Puerto Madryn city into Nueva Bay (located in the western extreme of Nuevo Gulf) is one of the probable factors to be taken into account. Laboratory cultures of this macroalgae were conducted in seawater enriched with the effluent. The nutrients (ammonium, nitrate and phosphate) uptake kinetics was studied at constant temperature and radiation (16?°C and 50 μE m?2 s?1 respectively). Uptake kinetics of both inorganic forms of nitrogen were described by the Michaelis–Menten model during the surge phase (ammonium: V max sur: 218.1 μmol h?1 g?1, K s sur: 476.5 μM and nitrate V max sur: 10.7 μmol h?1 g?1, K s sur: 6.1 μM) and during the assimilation phase (ammonium: V max ass: 135.6 μmol h?1 g?1, K s ass: 407.2 μM and nitrate V max ass: 1.9 μmol h?1 g?1, K s ass: 2.2 μM), with ammonium rates always higher than those of nitrate. Even though a net phosphate disappearance was observed in all treatments, uptake kinetics of this ion could not be properly estimated by the employed methodology. 相似文献
13.
Takashi Nishimura Osamu Yamaguchi Nobuyuki Takatani Shin-ichi Maeda Tatsuo Omata 《Photosynthesis research》2014,121(2-3):151-157
The carboxylase activities of crude carboxysome preparations obtained from the wild-type Synechococcus elongatus strain PCC 7942 strain and the mutant defective in the carboxysomal carbonic anhydrase (CA) were compared. The carboxylation reaction required high concentrations of bicarbonate and was not even saturated at 50 mM bicarbonate. With the initial concentrations of 50 mM and 25 mM for bicarbonate and ribulose-1,5-bisphosphate (RuBP), respectively, the initial rate of RuBP carboxylation by the mutant carboxysome (0.22 μmol mg?1 protein min?1) was only 30 % of that observed for the wild-type carboxysomes (0.71 μmol mg?1 protein min?1), indicating the importance of the presence of CA in efficient catalysis by ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). While the mutant defective in the ccmLMNO genes, which lacks the carboxysome structure, could grow under aeration with 2 % (v/v) CO2 in air, the mutant defective in ccaA as well as ccmLMNO required 5 % (v/v) CO2 for growth, indicating that the cytoplasmically localized CcaA helped utilization of CO2 by the cytoplasmically localized Rubisco by counteracting the action of the CO2 hydration mechanism. The results predict that overexpression of Rubisco would hardly enhance CO2 fixation by the cyanobacterium at CO2 levels lower than 5 %, unless Rubisco is properly organized into carboxysomes. 相似文献
14.
Yuki Watanabe Gregory N. Nishihara Shigemitsu Tokunaga Ryuta Terada 《Journal of applied phycology》2014,26(6):2405-2415
Phenology, irradiance, and temperature characteristics of an edible brown alga, Undaria pinnatifida (Laminariales), were examined from the southernmost natural population in Japan, both by culturing gametophytes and examining the photosynthetic activity of sporophytes using dissolved oxygen sensors and pulse amplitude-modulated chlorophyll fluorometer (IMAGING-PAM). Our surveys confirmed that sporophytes were present between winter and early summer, but absent by July. IMAGING-PAM experiments were used to measure maximum effective quantum yield (ΦII at 0 μmol photons m?2 s?1) for each of 14 temperatures (8–36 °C). Oxygen production was also determined over a coarser temperature gradient. Net photosynthesis and ΦII (at 0 μmol photons m?2 s?1) were observed to be temperature-dependent; the maximum ΦII was estimated to be 0.67, occurred at 21.2 °C, and was nearly identical to the optimal temperature of the net photosynthetic rate (21.7 °C). A net photosynthesis–irradiance (P–E) model revealed that saturation irradiance (E k) was 119.5 μmol photons m?1 s?1, and the compensation irradiance (E c) was 17.4 μmol photons m?1 s?1. Culture experiments on the gametophytes revealed that most individuals could not survive temperatures over 28 °C and that growth rates were severely inhibited. Based on our observations, temperatures greater than 20 °C are likely to influence photosynthetic activity and gametophyte survival, and therefore, it is possible that this species might become locally extinct if seawater temperatures in this region continue to rise. 相似文献
15.
Seasonal variability of methane in the rivers and lagoons of Ivory Coast (West Africa) 总被引:2,自引:0,他引:2
We report a data-set of dissolved methane (CH4) in three rivers (Comoé, Bia and Tanoé) and five lagoons (Grand-Lahou, Ebrié, Potou, Aby and Tendo) of Ivory Coast (West Africa), during the four main climatic seasons (high dry season, high rainy season, low dry season and low rainy season). The surface waters of the three rivers were over-saturated in CH4 with respect to atmospheric equilibrium (2221–38719%), and the seasonal variability of CH4 seemed to be largely controlled by dilution during the flooding period. The strong correlation of CH4 concentrations with the partial pressure of CO2 (pCO2) and dissolved silicate (DSi) confirm the dominance of a continental sources (from soils) for both CO2 and CH4 in these rivers. Diffusive air–water CH4 fluxes ranged between 25 and 1187 μmol m?2 day?1, and annual integrated values were 288 ± 107, 155 ± 38, and 241 ± 91 μmol m?2 day?1 in the Comoé, Bia and Tanoé rivers, respectively. In the five lagoons, surface waters were also over-saturated in CH4 (ranging from 1496 to 51843%). Diffusive air–water CH4 fluxes ranged between 20 and 2403 μmol m?2 day?1, and annual integrated values were 78 ± 34, 338 ± 217, 227 ± 79, 330 ± 153 and 326 ± 181 μmol m?2 day?1 in the Grand-Lahou, Ebrié, Potou, Aby and Tendo lagoons, respectively. The largest CH4 over-saturations were observed in the Tendo and Aby lagoons that are permanently stratified systems (unlike the other three lagoons), leading to anoxic bottom waters favorable for a large CH4 production. In addition, these two stratified lagoons showed low pCO2 values due to high primary production, which suggests an efficient transfer of organic matter across the pycnocline. As a result, the stratified Tendo and Aby lagoons were respectively, a low source of CO2 to the atmosphere and a sink of atmospheric CO2 while the other three well-mixed lagoons were strong sources of CO2 to the atmosphere but less over-saturated in CH4. 相似文献
16.
Christine E. Edwards Monia S. H. Haselhorst Autumn M. McKnite Brent E. Ewers David G. Williams Cynthia Weinig 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2009,119(6):991-1004
Growth chambers allow measurement of phenotypic differences among genotypes under controlled environment conditions. However, unintended variation in growth chamber air CO2 concentration ([CO2]) may affect the expression of diverse phenotypic traits, and genotypes may differ in their response to variation in [CO2]. We monitored [CO2] and quantified phenotypic responses of 22 Brassica rapa genotypes in growth chambers with either standard or enhanced venting. [CO2] in chambers with standard venting dropped to 280 μmol mol?1 during the period of maximum canopy development, ~80 μmol mol?1 lower than in chambers with enhanced venting. The stable carbon isotope ratio of CO2 in chamber air (δ13Cair) was negatively correlated with [CO2], suggesting that photosynthesis caused observed [CO2] decreases. Significant genotype × chamber-venting interactions were detected for 12 of 20 traits, likely due to differences in the extent to which [CO2] changed in relation to genotypes’ phenology or differential sensitivity of genotypes to low [CO2]. One trait, 13C discrimination (δ13C), was particularly influenced by unaccounted-for fluctuations in δ13Cair and [CO2]. Observed responses to [CO2] suggest that genetic variance components estimated in poorly vented growth chambers may be influenced by the expression of genes involved in CO2 stress responses; genotypic values estimated in these chambers may likewise be misleading such that some mapped quantitative trait loci may regulate responses to CO2 stress rather than a response to the environmental factor of interest. These results underscore the importance of monitoring, and where possible, controlling [CO2]. 相似文献
17.
John A. Arnone III Johann G. Zaller Gabriela Hofer Bernhard Schmid Christian Körner 《Oecologia》2013,171(3):613-622
Earthworms are among the world’s most important ecosystem engineers because of their effects on soil fertility and plant productivity. Their dependence on plants for carbon, however, means that any changes in plant community structure or function caused by rising atmospheric CO2 or loss of plant species diversity could affect earthworm activity, which may feed back on plant communities. Production of surface casts measured during three consecutive years in field experimental plots (n = 24, 1.2 m2) planted with local calcareous grassland species that varied in plant species richness (diversity levels: high, 31 species; medium, 12; low, 5) and were exposed to ambient (356 μl CO2 l?1) or elevated (600 μl CO2 l?1) CO2 was only consistently stimulated in high diversity plots exposed to elevated CO2 (+120 %, 31 spp: 603 ± 52 under ambient CO2 vs. 1,325 ± 204 g cast dwt. m?2 year?1 under elevated CO2 in 1996; +77 %, 940 ± 44 vs. 1,663 ± 204 g cast dwt. m?2 year?1 in 1998). Reductions in plant diversity had little effect on cast production in ecosystems maintained at ambient CO2, but the stimulatory effect of elevated CO2 on cast production disappeared when plant species diversity was decreased to 12 and 5 species. High diversity plots were also the only communities that included plant species that an earlier field study showed to be among the most responsive to elevated CO2 and to be most preferred by earthworms to deposit casts near. Further, the +87 % CO2-induced increase in cast production measured over the 3 years corresponded to a parallel increase in cumulative total nitrogen of 5.7 g N m?2 and would help explain the large stimulation of aboveground plant biomass production observed in high-diversity communities under elevated CO2. The results of this study demonstrate how the loss of plant species from communities can alter responses of major soil heterotrophs and consequently ecosystem biogeochemistry. 相似文献
18.
Mi-Hee Woo Young-Hyo Chang Hoi-Seon Lee Pyo June Pak Joong-Su Kim Namhyun Chung 《The protein journal》2014,33(1):110-117
A novel gene encoding thermostable endoglucanase was identified in Xanthomonas sp. EC102 from soil. The gene had 1,458 base pairs of open reading frame, which encode a 52-kDa protein of 486 amino acid residues. Sequence of the amino acid residues was similar with the endoglucanase from Xanthomonas campestris pv. campestris ATCC33913 (GenBank Accession No. NP_638867.1) (94 % identity). The endoglucanase was overexpressed in Escherichia coli BL21 and purified. Temperature for the highest enzymatic activity was 70 °C and pH optima was pH 5.5. The specific activity of the endoglucanase toward carboxymethylcellulose (CMC) was approximately 2 μmol min?1 mg?1, V max for CMC was 1.44 μmol mg?1 min?1, and K m values was 25.6 mg mL?1. The EC102 endoglucanase was stable at temperatures up to 60 °C, and it was activated by 0.1 mM of Mn2+ and Co2+. This is the first report about thermostable endoglucanase from Xanthomonas sp. 相似文献
19.
Localized permafrost disturbances such as active layer detachments (ALDs) are increasing in frequency and severity across the Canadian Arctic impacting terrestrial ecosystem functioning. However, the contribution of permafrost disturbance-carbon feedbacks to the carbon (C) balance of Arctic ecosystems is poorly understood. Here, we explore the short-term impact of active layer detachments (ALDs) on carbon dioxide (CO2) exchange in a High Arctic semi-desert ecosystem by comparing midday C exchange between undisturbed areas, moderately disturbed areas (intact islands of vegetation within an ALD), and highly disturbed areas (non-vegetated areas due to ALD). Midday C exchange was measured using a static chamber method between June 23 and August 8 during the 2009 and 2010 growing seasons. Results show that areas of high disturbance had significantly reduced gross ecosystem exchange and ecosystem respiration (R E) compared to control and moderately disturbed areas. Moderately disturbed areas showed significantly enhanced net ecosystem exchange compared to areas of high disturbance, but were not significantly different from control areas. Disturbance did not significantly impact soil thermal, physical or chemical properties. According to average midday fluxes, ALDs as a whole (moderately disturbed areas: ?1.942 μmol m?2 s?1+ highly disturbed areas: 2.969 μmol m?2 s?1) were a small CO2 source of 1.027 μmol m?2 s?1 which did not differ significantly from average midday fluxes in control areas 1.219 μmol m?2 s?1. The findings of this study provide evidence that the short-term impacts of ALDs on midday, net C exchange and soil properties in a High Arctic semi-desert are minimal. 相似文献
20.
Danielle Prévost Annick Bertrand Christine Juge François P. Chalifour 《Plant and Soil》2010,331(1-2):115-127
High CO2 has been shown to increase plant growth and to affect symbiotic activity in many legumes species, including soybean (Glycine max [L.] Merr.). In order to assess the interaction between elevated CO2 and rhizobial symbionts on soybean growth and nodulation, we combined the effects of CO2 with those of different bradyrhizobial strains and methods of inoculation. Soybean seeds were sown in agricultural soil in pots and inoculated with three strains of Bradyrhizobium japonicum (5Sc2 and 12NS14 indigenous to Quebec soils, and 532c, a reference strain), the inoculum being either applied directly to the seed or incorporated into the soil. Plants were grown in growth chambers (22/17ºC) for 6 weeks, under either near ambient (400 μmol mol?1) or elevated (800 μmol mol?1) concentrations of CO2. Elevated CO2 increased mass (63%) and number (50%) of soybean nodules, particularly medium and large, allowed a deeper nodule development, and increased shoot dry weight (+30%), shoot C uptake (+33%) and shoot N uptake (+78%), compared to ambient CO2. The two indigenous strains induced more medium and large nodules under elevated CO2 than the reference strain and showed the greatest increases in shoot dry weight. Soil inoculation induced higher number of small nodules than seed inoculation, specifically for the two indigenous strains, but did not affect plant growth parameters. We conclude that soybean yield enhancements due to elevated CO2 are associated with the production of large and medium-size nodules and a deep nodulation, that the two indigenous strains better respond to elevated CO2 than the reference strain, and that the method of inoculation has little influence on this response. 相似文献