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921.
Bonding Form Analysis of Metals and Sulfur Fractionation in Methanol‐Grown Anaerobic Granular Sludge
This study investigates the metal and sulfur bonding form distribution in mesophilic (30 °C, pH 7) methanol‐grown anaerobic granular sludge from upflow anaerobic sludge bed reactors operating at an organic loading rate of 3.8 g CH3OH‐COD/L d. This was achieved by applying a modified Tessier sequential extraction scheme to investigate the metal bonding forms and a sequential extraction scheme for sulfur and simultaneously extracted metals to granular sludge samples of the reactors after 0, 22, 35 and 43 days of operation. Metals were also determined in the sulfur extracts. Co and Ni predominated in their oxidizable bonding forms, which increased together with the pseudo‐total content during reactor operation. An omission of Co and Ni from the influent led to only a minor decline of the pseudo‐total content in the sludge, mainly from the acid‐soluble fraction. The ratio of simultaneously extracted metals (Co, Fe, Mn, Ni) to acid‐volatile sulfides was lower than 1, indicating that the sludge contained sufficient sulfide to bind the metals as metal monosulfides. The bioavailability of metals in the methanol‐grown anaerobic granular sludge investigated is therefore mainly controlled by sulfide formation/dissolution. 相似文献
922.
Guangqi Zhou Jianhua Yin Haijiang Chen Yijie Hua Linlin Sun Haichun Gao 《The ISME journal》2013,7(9):1752-1763
Shewanella species are a group of facultative Gram-negative microorganisms with remarkable respiration abilities that allow the use of a diverse array of terminal electron acceptors (EA). Like most bacteria, S. oneidensis possesses multiple terminal oxidases, including two heme-copper oxidases (caa3- and cbb3-type) and a bd-type quinol oxidase. As aerobic respiration is energetically favored, mechanisms underlying the fact that these microorganisms thrive in redox-stratified environments remain vastly unexplored. In this work, we discovered that the cbb3-type oxidase is the predominant system for respiration of oxygen (O2), especially when O2 is abundant. Under microaerobic conditions, the bd-type quinol oxidase has a significant role in addition to the cbb3-type oxidase. In contrast, multiple lines of evidence suggest that under test conditions the caa3-type oxidase, an analog to the mitochondrial enzyme, has no physiological significance, likely because of its extremely low expression. In addition, expression of both cbb3- and bd-type oxidases is under direct control of Crp (cAMP receptor protein) but not the well-established redox regulator Fnr (fumarate nitrate regulator) of canonical systems typified in Escherichia coli. These data, collectively, suggest that adaptation of S. oneidensis to redox-stratified environments is likely due to functional loss of the caa3-type oxidase and switch of the regulatory system for respiration. 相似文献
923.
Abstract Over the past 150 years the amount of CO2 in the atmosphere has been increasing, largely as a result of land-use change and anthropogenic emissions from the burning of fossil fuels. It is estimated that the atmospheric [CO2] will reach 70 Pa by the end of the 21st Century. The most important consequence of this rise in [CO2] is warming the surface temperature of the Earth by 0.4 – 0.6°C per decade throughout the 21st Century. Increasing [CO2] along with associated changes in temperature will most likely alter the structure and function of agro-ecosystems, affecting their productivity and their role as stable sinks to CO2 sequestration. Both CO2 and temperature are key variables affecting plant growth, development and functions. Moreover, because of the future scenario of higher temperature and evaporative demand, drought occurrences will be increased in frequency, intensity, and erratic pattern. The combination of elevated temperatures and the increased incidence of environmental stress will probably constitute the greatest risk caused by climate change to the agro-ecosystems in arid or semiarid areas of the world. The purpose of this paper is to review the exchange of carbon driving the main ecophysiological processes of plants in response to climate change and environmental stresses. Drought and salinity first affect the acquisition of CO2 by increasing stomatal and mesophyll resistances, and only after cause irreversible damages to the biochemical apparatus. Heat stress denatures thylakoid membranes, but this action may be counteracted by the synthesis of many isoprenoids in the chloroplasts from carbon freshly fixed by photosynthesis. There is rising concern about the impact of environmental stress on tree growth with this future scenario of global climate change. The combination of elevated temperatures and the increased incidence of environmental stress (particularly drought and salinity) will probably constitute the greatest risk caused by global climate change to the forest ecosystems in arid or semiarid areas of the world. 相似文献
924.
925.
锡林河流域一个原生草原群落的碳素平衡研究 总被引:10,自引:0,他引:10
野外调查与历史资料相结合 ,对内蒙古锡林河流域一个永久试验样地内的羊草 (Leymuschinensis (Trin .)Tzvel.)草原群落 (原生草原群落 )的碳素贮量、主要流量和周转速度等进行了估计。结果表明 :1 )该群落中地上部净初级生产的碳素固定量的多年平均值为 79.8gC·m-2 ·a-1 ,根系碳素输入量的多年平均值为 31 1 .9gC·m-2 ·a-1 ,碳素输入总量为 391 .7gC·m-2 ·a-1 ;2 )土壤净呼吸量为 34 6 .9gC·m-2 ·a-1 ,动物 (昆虫 )采食量 1 4 .7gC·m-2·a-1 ,地上立枯阶段的淋溶与光化学分解损失为 3 .2gC·m-2 ·a-1 ,碳素输出总量为 36 4 .8gC·m-2 ·a-1 ;3)该群落中碳素输入略大于输出 ,净积累速率为 2 6 .9gC·m-2 ·a-1 ,0 - 30cm土壤中的碳素周转速率为 6 .2 % ,周转时间为1 6年。 相似文献
926.
Luká 《植物学报(英文版)》2006,48(7):814-822
Cultivars of maize (Zea mays L.) with different sensitivity to drought were exposed to 0.3 mol/L sorbitol (-1.4 MPa water potential) for 24 h. Exposure to water deficiency significantly reduced the growth of both shoots (coleoptile and hypocotyl) and roots. Shoot growth was inhibited more than the growth of roots. Osmotic stress enhanced accumulation of soluble sugars. Electrolyte leakage, a cell injury index, was slightly increased after 0.3 mol/L sorbitoh Respiration was measured in the presence and absence of 2,6-dlchloro-phenol indophenoh 2,6-Dichloro-phenol indophenol did not influence respiration rates, because statistically equal results were observed under both conditions. Total respiration (VT) decreased after osmoticum treatment. There were no significant differences in the VT among the cultlvars analysed. The decrease In VT was caused by a decline In the activities and capacities of both cytochrome (Vcyt, Vcyt) and alternative pathway (Valt, Valt) of respiration. A high residual respiration (Vres) was observed, up to 27% of total uninhibited respiration. The result of uncoupler use clearly indicated that coupling was maintained after 24 h of osmotic stress. The recovery of the respiration rate was comparable with that of non-stressed control rates. According to these observations, no possible mltochondrial damage is expected. Water deficiency did not induce a stimulation of the alternative oxidase, so we assume that the stimulation of the alternative pathway is not related to drought stress resistance; rather, the function of the alternative pathway is to balance carbon metabolism and electron transport in a response to a changing environment. 相似文献
927.
Insects that are small or exhibit low metabolic rates are considered to not require active ventilation to augment diffusive gas exchange. Some pupae with low metabolic rates exhibit abdominal pumping, a behaviour that is known to drive tracheal ventilation in the adults of many species. However, previous work on pupae suggests that abdominal pumping may serve a non-respiratory role. To study the role of abdominal pumping in pupa of the beetle Zophobas morio, we visualized tracheal dynamics with X-rays while simultaneously measuring haemolymph pressure, abdominal movement, and CO2 emission. Pupae exhibited frequent tracheal compressions that were coincident with both abdominal pumping and pulsation of pressure in the haemolymph. However, more than 63% of abdominal pumping events occurred without any tracheal collapse and hence ventilation, suggesting that the major function of the abdominal pump is not respiratory. In addition, this study shows that the kinematics of abdominal pumping can be used to infer the status of the spiracles and internal behaviour of the tracheal system. 相似文献
928.
J. I. Garcia-Plazaola J. M. Becerril C. Arrese-Igor C. Gonzalez-Murua P. M. Aparicio-Tejo 《Plant and Soil》1993,157(2):207-213
The ability of Rhizobium meliloti cells to denitrify in soils under several conditions was tested. All the strains tested were able to remove large amounts of N-NO3
- from soils. Both water filled pore space above 36% and temperatures above 20°C greatly increased nitrogen losses. However, even with optimal conditions for denitrification and the highest rhizobial populations found in agricultural soils, the contribution of Rhizobium to the total denitrification was virtually negligible as compared to other soil microorganisms.To whom correspondence should be addressed 相似文献
929.
We investigated the effects of elevated soil temperature and atmospheric CO2 on soil CO2 efflux (SCE) during the third and fourth years of study. We hypothesized that elevated temperature would stimulate SCE, and elevated CO2 would also stimulate SCE with the stimulation being greater at higher temperatures. The study was conducted in sun-lit controlled-environment chambers using Douglas-fir (Pseudotsuga menziesii) seedlings grown in reconstructed litter-soil systems. We used a randomized design with two soil temperature and two atmospheric CO2 treatments. The SCE was measured every 4 wk for 18 months. Neither elevated temperature nor CO2 stimulated SCE. Elevated CO2 increased the temperature sensitivity of SCE. During the winter, the relationship between SCE and soil moisture was negative but it was positive during the summer. The seasonal patterns in SCE were associated with seasonal changes in photosynthesis and above-ground plant growth. SCE acclimatized in the high-temperature treatment, probably because of a loss of labile soil carbon. Elevated CO2 treatment increased the temperature sensitivity of SCE, probably through an increase in substrate availability. 相似文献
930.
Under slow flow conditions,daily rates of canopy photosynthesis of marine macrophytes were insensitive to model choice and flow‐rate 下载免费PDF全文
Gregory N. Nishihara Chizuru Yamada Ryutaro Kimura Ryuta Terada 《Phycological Research》2015,63(4):307-317
Water motion drives the flux of suspended and dissolved material (e.g., nutrients, gametes, and dissolved oxygen) to and from macrophyte canopies, and is one of the most important mechanisms that can regulate the growth, survival, and persistence of marine macrophytes populations. At small spatial scales (e.g., lamina or leaves and individuals), increasing flow‐rates have been demonstrated to enhance physiological processes, especially photosynthesis rates, and we expected a similar response at the canopy scale. We conducted seven experiments over 25 days using a pair of open‐air flow‐chambers under natural light, temperature, and seawater conditions. In the four marine macrophyte (Sargassum piluliferum, S. siliquastrum, S. thunbergii, and Zostera marina) canopies examined, an increase in flow‐rate did not enhance photosynthesis rates. The odds that daily gross photosynthesis rates increase with a decrease in flow‐rates was 1.77 to 1. We also examined if two non‐linear equations and one linear equation, often used to describe the relationship between photosynthesis to photosynthetic photon flux density (PPFD), biased estimates of the daily rates of photosynthesis and respiration. It was revealed that the functional form of the equation strongly influenced photosynthesis and respiration rate estimates at short time scales (i.e., minutes), however, daily rates were insensitive to the type of equation used to model the relationship between photosynthesis and PPFD. We suggest that the predominance of photosynthesis rates occurring in under‐saturating PPFD conditions (> 40 % of daylight hours) may be one of the reasons for this insensitivity. 相似文献