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1.
Medina VF Larson SL Agwaramgbo L Perez W 《International journal of phytoremediation》2002,4(2):143-156
Phytoremediation is an established technology for the treatment of explosives in water and soil. This study investigated the possibility of using slurried plants (or phytoslurries) to treat explosives (TNT and RDX). The degradation of TNT in solution using intact and slurried parrotfeather (Myriophyllum aquaticum), spinach (Spinicia oleracea), and mustard greens (Brassica juncea) was evaluated. Phytoslurries of parrotfeather and spinach removed the TNT faster than the intact plant. Conversely, the removal rate constants for slurried and intact mustard greens were about the same. A study using pressurized heating to destroy enzymatic activity in the phytoslurries was also conducted to compare removal from released plant chemicals to adsorptive removal. Aqueous phase removal of TNT by autoclaved spinach phytoslurry was compared with nonautoclaved spinach phytoslurry. The autoclaved phytoslurry did remove TNT, but not as completely as nonautoclaved slurry. This suggests that some removal is due to adsorption, but not all. Phytoslurries of mustard greens and parrotfeather had higher RDX removal rates compared with intact plant removal, but the rates for parrotfeather in either case were relatively low. Phytoslurries of spinach had relatively modest increases in RDX removal rates compared with intact plant. Studies were then conducted with phytoslurry/soil mixtures at two scales: 60 ml and 1.5 l. In both cases, phytoslurries of mustard greens and spinach removed TNT and RDX at higher levels than control slurries. 相似文献
2.
The Training Range Environmental Evaluation and Characterization System (TREECS?) computes the fate and transport of munitions constituents deposited on military firing/training ranges. TREECSTM was developed with two levels of capability, Tiers 1 and 2, where Tier 1 is for conservative screening assessments, and Tier 2 is for more accurate predictions. The models and associated processes for Tier 2 are described. Tier 2 was applied to ranges at Fort A.P. Hill, VA, for initial demonstration purposes. Observed field data were provided after model application and are compared to model-computed results. Although the comparison was not sufficient for model validation, it does demonstrate that the model leads to the same general conclusions that the field data provided. 相似文献
3.
Sylvie Rocheleau Ruxandra Cimpoia Louise Paquet Iris van Koppen Serge R. Guiot Jalal Hawari Guy Ampleman Sonia Thiboutot Geoffrey I. Sunahara 《Bioremediation Journal》1999,3(3):233-246
The ecotoxicological effects of four bioslurry reactors treating 2,4,6-trinitotoluene (TNT)- and 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX)-spiked soil were evaluated. A control bioslurry reactor was used to assess the endogenous toxicity of the bioslurry operation conditions. A battery of ecotoxicity tests was used: Microtox, green algae growth inhibition, bacterial genotoxicity and mutagenicity, and earthworm mortality and growth inhibition. Bioslurry soluble and solid phases were separated by centrifugation in order to identify toxicity and possible toxicants associated with each phase. Microtox toxicity values were initially very high in both bioslurry reactors spiked with TNT, in relation with TNT concentration. Initial toxicity was also detected by algal growth inhibition, earthworm lethality, genotoxicity and mutagenicity tests. An endogenous toxicity was detected in the control bioreactor using the Microtox and the SOS Chromotest. The soluble phase of the control bioslurry was genotoxic, suggesting that some potentially genotoxic agents were induced in the bioslurry samples. At the end of the bioremediation treatment, data showed that toxicity was reduced using all of the bioassays, except for earthworm lethality and growth inhibition tests in both RDX-spiked bioslurries. This study demonstrates the usefulness of a battery of toxicity tests to monitor bioremediation processes. 相似文献
4.
Cadmium and cadmium compounds are water soluble, mobile in most soils, bio-available, and tend to bio-accumulate. A pot culture experiment was conducted on contaminated soil to study the influence of lime and organic matter on the mobility of cadmium in spinach and its rhizosphere soil. Application of lime (50% and 100% lime requirement) and organic matter (0.5 and 1% by weight of soil) to soil decreased the availability of Cd to the soil and plant throughout the crop growth. The highest diethylene triamine penta-acetic acid (DTPA) extractable Cd was 10.84 mg kg?1 in the treatment OM0 L0 (No application of organic matter and lime) at 20 days after sowing of spinach. Likewise, the highest Cd concentration in spinach roots and shoots were 19.80 and 17.0 mg kg?1 in the treatment OM0 L0 at 20 days after sowing. The Cd concentration in spinach roots and shoots were decreased by 63.23 and 71.88%, respectively, in the treatment OM1 L100 (application of FYM at 1.0% by weight of soil and lime at 100% lime requirement) after 60 days of growth. The lowest concentrations of Cd in the soil and plant after the harvest of the crop were 2.88 and 4.27 mg kg?1, respectively, in the treatment OM1 L100 and resulted in 65.75 and 71.55% decrease over control (OM0 L0). The highest total chlorophyll content of leaves was 2.19 mg kg?1 of fresh weight in the treatment OM1 L100 at 40 days of crop growth. 相似文献
5.
The explosives TNT, HMX, and RDX are integral components of many munitions. The wastes from the manufacture and the use of these and other explosives has resulted in substantial contamination of water and soil. White rot fungi have been proposed for use in the bioremediation of contaminated soil and water. Strains of Phanerochaete chrysosporium and Pleurotus ostreatus adapted to grow on high concentrations of TNT were studied with regard to their ability to degrade TNT in liquid cultures. Both strains were able to cause extensive degradation of TNT. Field bioremediation studies using P. ostreatus were performed on site at the Yorktown Naval Weapons Station Yorktown (Yorktown, VA). In two plots, 6 cubic yards of soil contaminated with TNT, HMX, and RDX were blended with 3 cubic yards of a substrate mixture containing nutrients that promote the growth of fungi. In soil amended with growth substrate and P. ostreatus, concentrations of TNT, HMX and RDX were reduced from 194.0±50, 61±20 mg/kg and 118.0±30 to 3±4, 18±7 and 5±3?mg/kg, respectively, during a 62-day incubation period. Interestingly, in soil that was amended with this substrate mixture, but not with P. ostreatus, the concentrations of TNT, HMX, and RDX were also reduced substantially from 283±100, 67±20, and 144±50?mg/kg to 10±10, 34±20, and 12±10?mg/kg, respectively, during the same period. Thus, it appears that addition of amendments that enhance the growth and activity of indigenous microorganisms was sufficient to promote extensive degradation of these compounds in soil. 相似文献
6.
Mark E. Fuller Jean M. Lowey Charles E. Schaefer Robert J. Steffan 《Soil & Sediment Contamination》2005,14(4):373-385
There is increased interest in how to balance military preparedness and environmental protection at Department of Defense (DoD) facilities. This research evaluated a peat moss-based technology to enhance the adsorption and biodegradation of explosive residues at military testing and training ranges. The evaluation was performed using 30-cm-long soil columns operated under unsaturated flow conditions. The treatment materials were placed at the soil surface, and soil contaminated with 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) was spread over the surface. Simulated rainfall initiated dissolution and leaching of the explosive compounds, which was monitored at several depths within the columns. Peat moss plus soybean oil reduced the soluble concentrations of TNT, RDX and HMX detected at 10 cm depth by 100%, 60%, and 40%, respectively, compared to the no-treatment control column. Peat moss alone reduced TNT and HMX concentrations at 10 cm depth relative to the control, but exhibited higher soluble RDX concentrations by the end of the experiment. Concentrations of HMX and RDX were also reduced at 30 cm depth by the peat moss plus soybean oil treatments relative to those observed in the control column. These preliminary results demonstrate proof-of-concept of a low cost technology for reducing the contamination of groundwater with explosives at military test and training ranges. 相似文献
7.
Tizazu H. Mekonnen Paolo G. Mussone Natisha Stashko Phillip Y. Choi David C. Bressler 《Process Biochemistry》2013,48(5-6):885-892
The purpose of this study was to characterize proteinacious material recovered from cattle tissues known as specified risk materials (SRM) hydrolyzed according to two protocols approved by the Canadian Food Inspection Agency and Food and Drug Administration and to evaluate its potential for non-food/feed value-added applications. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), size exclusion high performance liquid chromatography (SEC-HPLC), and free amino acid determination methods were adopted to measure the extent of protein cleavage and the average molecular weight of hydrolyzates, and to identify the reactive functionalities available. Molecular weight analysis revealed that the alkaline hydrolysis protocol cleaved the proteins more severely than thermal hydrolysis. Both protocols narrowed the molecular weight distribution of the proteins and increased their solubility in water. Several active functional groups amenable to further chemical processing were identified in the protein hydrolyzates. In conclusion, this work demonstrated that both hydrolytic protocols can be adopted as pre-processing steps to produce safe and renewable proteinacious feedstock for industrial applications. 相似文献
8.
We hypothesized that biodegradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)—a widely used explosive contaminating
soil and groundwater—by Rhodococcus strain YH1 is controlled by the presence of external nitrogen sources. This strain is capable of degrading RDX while using
it as sole nitrogen source under aerobic conditions. Both inorganic and organic nitrogen sources were found to have a profound
impact on RDX-biodegradation activity. This effect was tested in growing and resting cells of strain YH1. Nitrate and nitrite
delayed the onset of RDX degradation by strain YH1, while ammonium inhibited it almost completely. In addition, 2,4,6-trinitrotoluene
(TNT) inhibited RDX degradation and growth of strain YH1. On the other hand, tetrahydrophthalamide did not influence biodegradation
or growth. Growth on RDX induced the expression of a cytochrome P-450 enzyme that is suggested to be involved in the first
step in the aerobic pathway of RDX degradation, as identified by SDS-PAGE analysis. Ammonium and nitrite strongly repressed
cytochrome P-450 expression. Our findings suggest that effective RDX bioremediation by strain YH1 requires the design of a
treatment scheme that includes initial removal of ammonium, nitrite, nitrate and TNT before RDX degradation can take place. 相似文献
9.
Lime treatment and its effects on the chemistry and biota of hardwater eutrophic lakes 总被引:1,自引:0,他引:1
Ellie E. Prepas Bernadette Pinel-Alloul Patricia A. Chambers Tom P. Murphy Sharon Reedyk Greg Sandland & Mark Serediak 《Freshwater Biology》2001,46(8):1049-1060
1. The main focus of this study was to investigate the effects of single and multiple moderate doses of lime (slaked lime, Ca(OH)2 , and/or calcite, CaCO3 ) on eutrophic hardwater lakes. This information would contribute to strategies to manage phytoplankton and macrophyte biomass in eutrophic lakes.
2. Water chemistry and biota were monitored for up to 7 years after initial lime treatment and results were compared with reference systems.
3. Complementary studies investigated the effect of lime on macrophytes in ponds, irrigation canals and microcosm experiments.
4. When water pH was kept within its natural range (≤ 10), single and multiple lime applications to lakes and ponds controlled macrophyte biomass, without negatively affecting invertebrate communities.
5. Single lime treatments at moderate dosages of lakes and ponds resulted in variable and mostly temporary changes in chlorophyll a (chl a ) and phosphorus (P) concentration. Although sediment P release was reduced in single-dose lakes during the first winter following treatment, reductions appeared temporary.
6. Multiple treatments of lakes and ponds were effective at reducing both chl a and P concentrations over longer periods. Mean winter P release rate was also reduced after initial treatment.
7. In laboratory studies, sediment cores were incubated with eight different treatments to assess P release. Redox-sensitive treatments were no more effective at lowering total P concentration in overlying water than some redox-insensitive treatments. Lime reduced total P concentrations, but was not as effective as treatments with alum.
8. The use of lime in managing macrophyte and phytoplankton biomass in shallow, hardwater lakes and ponds may be preferable over other treatments, because lime is economical and non-toxic as long as pH is kept within a natural range. 相似文献
2. Water chemistry and biota were monitored for up to 7 years after initial lime treatment and results were compared with reference systems.
3. Complementary studies investigated the effect of lime on macrophytes in ponds, irrigation canals and microcosm experiments.
4. When water pH was kept within its natural range (≤ 10), single and multiple lime applications to lakes and ponds controlled macrophyte biomass, without negatively affecting invertebrate communities.
5. Single lime treatments at moderate dosages of lakes and ponds resulted in variable and mostly temporary changes in chlorophyll a (chl a ) and phosphorus (P) concentration. Although sediment P release was reduced in single-dose lakes during the first winter following treatment, reductions appeared temporary.
6. Multiple treatments of lakes and ponds were effective at reducing both chl a and P concentrations over longer periods. Mean winter P release rate was also reduced after initial treatment.
7. In laboratory studies, sediment cores were incubated with eight different treatments to assess P release. Redox-sensitive treatments were no more effective at lowering total P concentration in overlying water than some redox-insensitive treatments. Lime reduced total P concentrations, but was not as effective as treatments with alum.
8. The use of lime in managing macrophyte and phytoplankton biomass in shallow, hardwater lakes and ponds may be preferable over other treatments, because lime is economical and non-toxic as long as pH is kept within a natural range. 相似文献
10.
Nancy George Sonica Sondhi Sanjeev Kumar Soni Naveen Gupta 《Indian journal of microbiology》2014,54(2):139-142
The objective of this work was to isolate a microorganism producing alkaline protease that can be used as an ecofriendly alternative to chemicals in dehairing process of leather manufacture. Alkaline protease producing bacterium Vibrio metschnikovii NG155 was isolated from soil samples of leather industry. The protease was highly effective in dehairing of goat skin, completely eliminating the use of lime and sulfide. Histological studies of the skin after dehairing showed that the enzyme did not damage the collagen layer and brought good fiber opening. Absence of collagenase activity was confirmed by reacting pure collagen with the enzyme and analyzing it on SDS PAGE, which showed no degradation of collagen. The enzyme was stable in a wide range of pH (7–11) and temperature (10–50 °C), which makes it suitable for industrial application. 相似文献
11.
Carbon source recovery from waste activated sludge by alkaline hydrolysis and gamma-ray irradiation for biological denitrification 总被引:3,自引:1,他引:3
The recovery of an organic carbon source from a waste activated sludge by using alkaline hydrolysis and radiation treatment was studied, and the feasibility of the solubilized sludge carbon source for a biological denitrification was also investigated. The effects of an alkaline treatment and gamma-ray irradiation on a biodegradability enhancement of the sludge were also studied. A modified continuous bioreactor for a denitrification (MLE reactor) was operated by using a synthetic wastewater for 47 days. Alkaline treatment of pH 10 and gamma-ray irradiation of 20 kGy were found to be the optimum carbon source recovery conditions. COD removal of 84% and T-N removal of 51% could be obtained by using the solubilized sludge carbon source through the MLE denitrification process. It can be concluded that the carbon source recovered from the waste activated sludge was successfully employed as an alternative carbon source for a biological denitrification. 相似文献
12.
Vladimir D. Kreslavski Galina K. Vasilyeva Steven D. Comfort Rhae A. Drijber Patrick J. Shea 《Bioremediation Journal》1999,3(1):59-67
Enhanced microbial activity and xenobiotic transformations take place in the rhizosphere. Degradation and binding of 2,4,6-trinitrotoluene (TNT) were determined in two rhizosphere soils (RS) and compared to respective unplanted control soils (CS). The rhizosphere soils were obtained after growing corn for 70 d in soils containing 2.8% (Soil A) or 5.9% (Soil B) organic matter. Aerobically agitated soil slurries (3:1, solution/soil) were prepared from RS and CS and amended with 75 mg TNT L-1 (14C-labeled). TNT degraded more rapidly and formed more un-extractable bound residue in RS than in CS. In Soil A, total extractable TNT decreased from 225 to 1.0 mg kg-1 in RS, whereas 11 mg kg-1 remained in CS after 15 d. Unextractable bound 14C residues accounted for 40% of the added 14C-TNT in RS and 28% in CS. The smaller differences in Soil B were attributed partially to the higher organic matter content. The predominant TNT degradation products were monoaminodinitrotoluenes (ADNT), which accumulated and disappeared more rapidly in RS than in CS, and hydroxylaminodinitrotoluenes (HADNT). When sterilized by γ-irradiation, no significant differences between RS and CS were observed in TNT loss or bound residue formation. More rapid TNT degradation and enhanced bound residue formation in the unsterilized RS was attributed to micro-bial-facilitated production and transformation of HADNT and ADNT, which are potential precursors to bound residue formation. If plants can be established on TNT-contaminated soil, these results indicate that the rhizosphere can accelerate reductive transformation of TNT and promote bound residue formation. 相似文献
13.
Isolation and Screening of Alkaline Lipase-producing Fungi
from Brazilian Savanna Soil 总被引:1,自引:0,他引:1
Gecernir Colen Roberto Gonçalves Junqueira Tasso Moraes-Santos 《World journal of microbiology & biotechnology》2006,22(8):881-885
Summary Fifty-nine lipase-producing fungal strains were isolated from Brazilian savanna soil by employing enrichment culture tecniques. An agar plate medium containing bile salts and olive oil emulsion was employed for isolating and growing fungi in primary screening assay. Twenty-one strains were selected by the ratio of the lipolytic halo radius and the colonies radius. Eleven strains were considered good producers under conditions of submerged liquid fermentation (shaken cultures) and solid-state fermentation. The most productive strain, identified as Colletotrichum gloesporioides, produced 27,700 U/l of lipase under optimized conditions and the crude lipase preparation was capable of hydrolysing a broad range of substrates including lard, natural oils and tributyrin. 相似文献
14.
Corey W. Radtke Dan M. Smith G. Scott Owen Francisco F. Roberto 《Bioremediation Journal》2002,6(2):191-204
Solid fragments of explosives in soil are common in explosives testing and training areas. In this study we initially sieved the upper 6 in of contaminated soil through a 3-mm mesh, and found 2,4,6-trinitrotoluene (TNT) fragments. These contributed to an estimated concentration of 1.7 kg per cubic yard soil, or for 2000 ppm TNT in the soil. Most of the fragments ranged 4 mm to 10 mm diameter in size, but explosives particles weighing up to 56 g (about 4 cm diameter) were frequently observed. An acetone pretreatment/composting system was then demonstrated at field scale. The amount of acetone required for a TNT-dissolving slurry process was controlled by the viscosity of the soil/acetone mix rather than the TNT dissolution rate. The amount needed was estimated at about 55 gallons acetone per cubic yard soil. Smaller, 5- to 10-mm-diameter fragments went into solution in less than 15 min at a mixer speed of 36 rpm, with a minimum of 2 g TNT going into solution per 30 min for the larger chunks. The slurries were then mixed with compost starting materials and composted in a vented 1 yd3 container. After 34 days incubation time TNT was below the site-specific regulatory threshold of 44 ppm. TNT metabolites and acetone were also below their regulatory thresholds established for the site. 相似文献
15.
Louis-B. Jugnia Danielle Beaumier Jennifer Holdner Serge Delisle Charles W. Greer Meghan Hendry 《Soil & Sediment Contamination》2017,26(7-8):722-735
Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a toxic, mobile groundwater contaminant common to military sites. Biodegradation of RDX is an alternative, cost effective and environmentally friendly remediation approach. The effects of carbon amendments (waste glycerol and cheese whey) used alone or with a potential electron shuttle (ammonium lignosulfonate) on RDX biodegradation were assessed. These substrates are readily available waste materials that can be used as nutrients to promote oxygen consumption, creating a more reducing environment. Nutrient amended batch assays were conducted using RDX spiked contaminated demolition range soil under anaerobic conditions. The amendments that improved RDX mineralization the most were subsequently tested in a scaled up repacked soil column study to verify if this strategy could be effectively implemented on-site. Microcosm results indicated that RDX mineralization by indigenous anaerobic microorganisms was enhanced the most by the low carbon amendment concentration. The use of ammonium lignosulfonate was not effective, exhibiting an inhibitory effect on RDX biodegradation that was stronger at higher concentrations. The soil column study showed that the low concentration of waste was the most promising treatment scenario. These results offer good prospects for the use of waste glycerol for in situ treatment of soils contaminated with energetic-materials, such as RDX. 相似文献
16.
Michael L. Adam Steve D. Comfort Tian C. Zhang Matthew C. Morley 《Bioremediation Journal》2005,9(1):9-19
Ground water beneath the U.S. Department of Energy (USDOE) Pantex Plant is contaminated with the high explosive RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine). The authors evaluated biodegradation as a remedial option by measuring RDX mineralization in Pantex aquifer microcosms spiked with 14C-labeled RDX (75 g soil, 15 ml of 5 mg RDX/L). Under anaerobic conditions and constant temperature (16°C), cumulative 14CO2 production ranged between 52% and 70% after 49 days, with nutrient-amended (C, N, P) microcosms yielding the greatest mineralization (70%). The authors also evaluated biodegradation as a secondary treatment for removing RDX degradates following oxidation by permanganate (KMnO4) or reduction by dithionite-reduced aquifer solids (i.e., redox barriers). Under this coupled abiotic/biotic scenario, we found that although unconsumed permanganate initially inhibited biodegradation, > 48% of the initial 14C-RDX was recovered as 14CO2 within 77 days. Following exposure to dithionite-reduced solids, RDX transformation products were also readily mineralized (> 47% in 98 days). When we seeded Pantex aquifer material into Ottawa Sand that had no prior exposure to RDX, mineralization increased 100%, indicating that the Pantex aquifer may have an adapted microbial community that could be exploited for remediation purposes. These results indicate that biodegradation effectively transformed and mineralized RDX in Pantex aquifer microcosms. Additionally, biodegradation may be an excellent secondary treatment for RDX degradates produced from in situ treatment with permanganate or redox barriers. 相似文献
17.
The objective of the research was to investigate the effect of biomass loading, alkali (NaOH) concentration and pre-treatment time on the yield of glucose obtained following alkaline pre-treatment and enzymatic hydrolysis of oilseed rape (OSR) straw. A maximum glucose yield of (440.6 ± 14.9) g glucose kg−1 biomass was obtained when OSR straw was pre-treated at a biomass loading of 50 g kg−1 and an alkali concentration of 0.63 mol dm−3 NaOH for 30 min. The energy efficiency of glucose extraction (0.39 kg glucose MJ−1 consumed) was highest when OSR straw was pre-treated at a biomass loading of 50 g kg−1 and an alkali concentration of 0.63 or 0.75 mol dm−3 for 30 min. The study demonstrated alkaline pre-treatment of OSR straw is superior to acid pre-treatment in terms of glucose yield and energy efficiency. 相似文献
18.
Marc-Olivier Turcotte-Savard 《Soil & Sediment Contamination》2019,28(3):245-257
The remediation efficiency of soils containing energetic materials (EM) is assessed using SW-846 USEPA Method 8330B. However, the extraction, which is performed by sonicating the soil samples in acetonitrile for several hours, could lead to additional degradation of EM during sample processing, and consequently, to an overestimation of remediation efficiency. To verify this, soil samples that were spiked with controlled amounts of EM were briefly exposed to remediation reagents, such as MuniRem® (a commercial sodium dithionite-based formulation) or hydrated lime, and analyzed using SW-846 USEPA Method 8330B. The most affected EM of this study was 2,4,6-trinitrotoluene (TNT), for which complete degradation was observed after exposure to hydrated lime or pH-buffered MuniRem®. Losses of 1,3,5-trinitro-1,3,5-triazinane (RDX) reached 30 ± 20% upon treatment with full pH-buffered MuniRem® and 90 ± 10% when exposed to lime. The concentrations of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) were near the method’s lower limit of quantification, and subjected to large errors, which prevented us from drawing any clear conclusions regarding its degradation under the studied experimental conditions. These results highlight the necessity of performing appropriate soil sample treatments to quench the remaining hydrated lime or sodium dithionite prior to the extraction and analysis steps with SW-846 USEPA Method 8330B. Quenching of remaining remediation reagents may possibly be also required for other remediation reagents and EM. 相似文献
19.
The effect of photosynthesis on N2O emission from soil was investigated by shading soybean (Gycline max. L) plant at flowering, pod-setting and grain-filling stages. The results showed that by stopping photosynthesis through shading the plants stimulated N2O emission significantly at flowering stage and pod-setting stage, and suppressed N2O emission dramatically at grain-filling stage. At flowering stage, soybean species seem to rely mainly on fertilizer N and shaded plants decreased the N uptake. Interaction between the relative increase in available N for N2O production by shading and the presence of root exudates promoted N transformation (nitrification/denitrification) and N2O emission. At pod-setting stage, the available soil nitrogen seems to be a critical limiting factor and without substantial release of symbiotically fixed N through plant roots, resulted in a weak effect of shading on N2O emission. At grain-filling stage, available N for N2O production was derived from symbiotically fixed N and was greatly affected by photosynthesis. These results indicated that the effect of soybean growth on N2O emission from soil varies with plant growth stages as available N for N2O production is mainly from fertilizer N and organic mineralization during the early growth of soybean plants, while N2O emission is controlled by the quantity and perhaps also the quality of root exudates, which is closely related with plant photosynthesis in the late season of soybean growth. 相似文献
20.
It is well accepted that sucrose (Suc) metabolism is involved in responses to environmental stresses in many plant species.
In the present study we showed that alkaline invertase (A-Inv) expression is up-regulated in wheat leaves after an osmotic
stress or a low-temperature treatment. We demonstrated that the increase of total alkaline/neutral Inv activity in wheat leaves
after a stress could be due to the induction of an A-Inv isoform. Also, we identified and functionally characterized the first
wheat cDNA sequence that codes for an A-Inv. The wheat leaf full-length sequence encoded a protein 70% similar to a neutral
Inv of Lolium temulentum; however, after functional characterization, it resulted to encode a protein that hydrolyzed Suc to hexoses with an optimum
pH of 8, and, consequently, the encoding sequence was named Ta-A-Inv. By RT-PCR assays we demonstrated that Ta-A-Inv expression is induced in response to osmotic and cold stress in mature primary wheat leaves. We propose that Ta-A-Inv activity
could play an important role associated with a more efficient cytosolic Suc hydrolysis during environmental stresses.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献