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1.
We investigated the differential responses of invasive alien Lemna minuta and native Lemna minor to nutrient loading as well as the mechanism of competition between the species. The role of nutrients, species identity, species influence in determining the outcome of competition between the species was estimated using the Relative Growth Rate Difference (RGRD) model. The two species differed in their response to nutrient loading. The native L. minor responded indifferently to nutrient loading. The species Relative Growth Rate (RGR) was 0.10 d−1, 0.11 d−1 and 0.09 d−1 in high, medium and low nutrients, respectively. On the other hand, the invasive L. minuta responded opportunistically to high nutrient availability and had an RGR of 0.13 d−1, 0.10 d−1 and 0.08 d−1 in high, medium and low nutrients, respectively. As a result, the invasive species was dominant in high nutrient availability but lost to the native species at low nutrient availability. The invader formed approximately 60% and less than 50% of the stand final total dry biomass in high and low nutrient availability, respectively. Species RGR were reduced by both intra- and interspecific competition but intraspecific effects were stronger than interspecific effects. On the overall, the species significantly differed in their constant RGR. These differences in RGR between the species (species identity) and the differential response to nutrient loading were the main determinant of change in final biomass composition of these species in mixture. Species influence (competition) only had a small influence on the outcome of competition between the species. The observed species response to nutrient loading could be targeted in management of the invasive species. Lowering nutrients can be proposed to reduce the impact of the invasive L. minuta.  相似文献   

2.
Industrial wastewater treatment comprises several processes to fulfill the discharge permits or to enable the reuse of wastewater. For tannery wastewater, constructed wetlands (CWs) may be an interesting treatment option. Two-stage series of horizontal subsurface flow CWs with Phragmites australis (UP series) and Typha latifolia (UT series) provided high removal of organics from tannery wastewater, up to 88% of biochemical oxygen demand (BOD5) (from an inlet of 420 to 1000 mg L−1) and 92% of chemical oxygen demand (COD) (from an inlet of 808 to 2449 mg L−1), and of other contaminants, such as nitrogen, operating at hydraulic retention times of 2, 5 and 7 days. No significant (P < 0.05) differences in performance were found between both the series. Overall mass removals of up to 1294 kg COD ha−1 d−1 and 529 kg BOD5 ha−1 d−1 were achieved for a loading ranging from 242 to 1925 kg COD ha−1 d−1 and from 126 to 900 kg BOD5 ha−1 d−1. Plants were resilient to the conditions imposed, however P. australis exceeded T. latifolia in terms of propagation.  相似文献   

3.
The degradation of an Ulva lactuca mat (0.2 kg dw m−2) was studied in a controlled flow-through mesocosm for 31 d. Sediment chambers without U. lactuca served as controls. Fluxes of ∑CO2, O2, inorganic nitrogen, and urea were determined during the incubation period in addition to sulfate reduction rates, POC and PON content, enumeration of specific bacterial populations and evaluation of the physiological state of the added U. lactuca thalli. After U. lactuca addition to the chambers, there was an immediate increase in the efflux of ∑CO2 from 11 to 27 mmol-C m−2 d−1 and a concomitant increase in O2 uptake from 11 to 23 mmol m−2 d−1. These effluxes remained elevated throughout the incubation period. In contrast, the NH4+ efflux increased from 0.1 to 1.8 mmol NH4+ m−2 d−1 during the first 3 d of incubation, followed by 6 d with a constant efflux rate, after which time it decreased gradually to 0.3 mmol NH4+ m−2 d−1 by the end of the experiment. In total, NH4+accounted for 83% of the total nitrogen efflux after addition of U. lactuca. During the 31 d incubation period there was a continuous colonization of the thalli by bacteria. Sulfate reducers associated with the thalli accounted for 3% of the carbon oxidation on day 31. The molar C:N ratio in mineralization products (the ratio between the efflux of ∑CO2 and NH4+ + NO2 + NO3) increased from 15 mol mol−1 at day 11 after U. lactuca addition to >80 mol mol−1 by the end of the incubation. Since the C:N ratio in the mineralization products was much higher than the original thallus material (8.9 mol mol−1) it is probable that a preferential incorporation of NH4+ into the increasing bacterial biomass occurred. The nitrogen for bacterial growth was most likely obtained from degradation of U. lactuca thalli as there was no stimulation of urea-N turnover in the sediment during incubation. The net increase in bacteria cell number in the 18-mm thick thallus layer was estimated to be 7.6 × 109 to 2.4 × 1010 bacterial cells cm−3. In contrast, the bacterial cell number remained constant in the −Ulva incubations.  相似文献   

4.
Previous estimations of nutrient mineralization in the water column by infaunal bivalves might have been overestimated because of underestimation of the uptake process by microphytobenthos in the field. We conducted field surveys of environmental conditions and quantitative sampling of Ruditapes philippinarum in a shallow lagoon system (Hichirippu Lagoon, eastern Hokkaido, Japan) in August 2006. We recorded the spatial distribution pattern and the molar ratio of dissolved inorganic nutrients to determine the limiting nutrients for microphytobenthos, to evaluate the input and output of nutrients at the entrance of the lagoon station, and to estimate potential nutrient mineralization by R. philippinarum. Our aim was to reevaluate the nutrient mineralization process by infaunal bivalve species. In this study, the mean standing stock of microphytobenthos inhabiting surface sediment (5 mm thick) on the tidal flats was 100 times higher than that of phytoplankton (1 m depth). Low N/P and high Si/N ratios (mean = 2.6 and 17.6, respectively) near the entrance of the lagoon compared to those of microphytobenthos (N:P:Si = 10.1:1:18) clearly suggest N deficiency. The flux of NH4-N coming into the lagoon was 3.4 kmolN d− 1, and the flux out was − 3.7 kmolN d− 1. Thus, assuming that there would have been no phytoplankton and microphytobenthos uptake during the day, 0.3 kmolN d− 1 of NH4-N was produced within the lagoon. However, the NH4-N mineralization rate of the clams has been estimated to be approximately 7.7 ± 6.8 kmolN d− 1. Thus, 96% (7.4 kmolN d− 1, i.e., 7.7 kmolN d− 1 minus 0.3 kmolN d− 1) of the NH4-N mineralized by the clam was consumed by microphytobenthos. In contrast, if all the NH4-N inflow (3.1 kmolN d− 1) was consumed by the microalgae before outflow, 52% (4.0 kmolN d− 1, i.e., 7.7 kmolN d− 1 minus 3.7 kmolN d− 1) of the NH4-N mineralized by the clams should have been consumed by microphytobenthos. Microphytobenthos on the tidal flats (11.3 ± 11.8 kmolN) used all of the surplus nutrients (between 4.0 and 7.4 kmolN d− 1), and the temporal division rate [=(NH4-N uptake)/(standing stock of microphytobenthos)] of microphytobenthos would have to be between 0.35 and 0.65 d− 1. Residual NH4-N (0.3 - 3.7 kmolN d− 1) was the water-column source and accounted for 12-148% of NH4-N in the water column near the entrance of the lagoon (2.5 ± 1.4 kmolN) per day. This is the first field-based observation with a quantitative evaluation of nutrient mineralization by infaunal bivalves and nutrient uptake by microphytobenthos.  相似文献   

5.
The present study employed simultaneously methods to investigate particle and solute transport and reaction rates in sandy sediments inhabited by two worms (2500 m− 2) with different feeding modes. Heteromastus filiformis is a head-down deposit-feeder and the main activities exerted by this worm are transport of particles as faecal pellets from subsurface to surface sediments and burrow ventilation. Marenzelleria viridis is a surface deposit-feeder that actively searches for food by burrowing near the sediment surface, producing a network of ventilated galleries in this zone. M. viridis exhibited 1.5 to 2.2 times higher particle mixing rates (Db = 3.3 to 4 × 10− 3 cm− 2 d− 1) compared to H. filiformis. In M. viridis treatments, continuous advection (eddy diffusion) was the major factor influencing solute transport resulting in apparent diffusion rates (Da = 2.2 cm− 2 d− 1), which were 3 times higher than molecular diffusion within the sediment. In H. filiformis inhabited sediments, the transport of solutes was discontinuous and driven by a surprisingly high nonlocal exchange (α = 1.1-1.3 d− 1), emphasizing its strong irrigation effects. Accordingly, the enhancement of solute fluxes was more pronounced for H. filiformis compared to M. viridis. Depth integrated TCO2 production derived from diagenetic modelling, which takes into account three reaction zones, is in good agreement with rates obtained from measured fluxes, indicating the applicability of both approaches to get reliable rates. However, the reaction rates showed that the presence of animals had a modest effect on microbial carbon oxidation. The results proved that transport conditions are deeply related to feeding modes. Exchange of solutes was the most important transport process by H. filiformis, while M. viridis affected both mixing and solute transport.  相似文献   

6.
Changes in photosynthetic pigment ratios showed that the Chlorophyll d-dominated oxyphotobacterium Acaryochloris marina was able to photoacclimate to different light regimes. Chl d per cell were higher in cultures grown under low irradiance and red or green light compared to those found when grown under high white light, but phycocyanin/Chl d and carotenoid/Chl d indices under the corresponding conditions were lower. Chl a, considered an accessory pigment in this organism, decreased respective to Chl d in low irradiance and low intensity non-white light sources. Blue diode PAM (Pulse Amplitude Modulation) fluorometry was able to be used to measure photosynthesis in Acaryochloris. Light response curves for Acaryochloris were created using both PAM and O2 electrode. A linear relationship was found between electron transport rate (ETR), measured using a PAM fluorometer, and oxygen evolution (net and gross photosynthesis). Gross photosynthesis and ETR were directly proportional to one another. The optimum light for white light (quartz halogen) was about 206 ± 51 μmol m− 2 s− 1 (PAR) (Photosynthetically Active Radiation), whereas for red light (red diodes) the optimum light was lower (109 ± 27 μmol m− 2 s− 1 (PAR)). The maximum mean gross photosynthetic rate of Acaryochloris was 73 ± 7 μmol mg Chl d− 1 h− 1. The gross photosynthesis/respiration ratio (Pg/R) of Acaryochloris under optimum conditions was about 4.02 ± 1.69. The implications of our findings will be discussed in relation to how photosynthesis is regulated in Acaryochloris.  相似文献   

7.
Glycerol was utilized by Cupriavidus necator DSM 545 for production of poly-3-hydroxybutyrate (PHB) in fed-batch fermentation. Maximal specific growth rates (0.12 and 0.3 h−1) and maximal specific non-growth PHB production rate (0.16 g g−1 h−1) were determined from two experiments (inocula from exponential and stationary phase). Saturation constants for nitrogen (0.107 and 0.016 g L−1), glycerol (0.05 g L−1), non-growth related PHB synthesis (0.011 g L−1) and nitrogen/PHB related inhibition constant (0.405 g L−1), were estimated. Five relations for specific growth rate were tested using mathematical models. In silico performed optimization procedures (varied glycerol/nitrogen ratio and feeding) has resulted in a PHB content of 70.9%, shorter cultivation time (23 h) and better PHB yield (0.347 g g−1). Initial concentration of biomass 16.8 g L−1 and glycerol concentration in broth between 3 and 5 g L−1 were decisive factors for increasing of productivity.  相似文献   

8.
This experimental study quantified and compared particle-mixing and solute transport by the polychaetes Marenzelleria neglecta (2 g ww, 3200 ind. m− 2) and Hediste diversicolor (2 g ww, 800 ind. m− 2) in Baltic Sea sediments. Particle tracers (luminophores) were added to the sediment surface and their vertical distribution in the sediment was measured after 10 d. The rate of particle mixing was quantified using a gallery-diffusion model calculating the biodiffusion coefficient Db and the non-local transport parameter r. Bioirrigation was measured by adding an inert solute tracer (bromide) to the overlying water 1, 1.5 and 2 d before the end of the experiment, and quantified by calculating the net bromide flux and fitting the bromide profiles to a 1D diffusion model providing an apparent biodiffusion coefficient Da. The two polychaete worms displayed similar particle-mixing and solute transport efficiencies (based on total biomass) despite different modes of bioturbation. However, H. diversicolor was a more efficient particle-reworker and M. neglecta a more efficient bioirrigator, on an individual level. H. diversicolor buried a higher percentage (13%) of luminophores below the top 0.5 cm surface layer than M. neglecta (6%). Db did not differ between the two species (2.4 × 10− 3 cm2 d− 1) indicating a similar rate of diffusive mixing of the top sediment, however, the non-local transport parameter r was 2.5 y− 1 for H. diversicolor and zero for M. neglecta, suggesting no significant particle-transport below the biodiffusive layer by M. neglecta. The average individual net bromide fluxes obtained were ca. 0.01 mL min− 1 for H. diversicolor and 0.003 mL min− 1 for M. neglecta, corresponding to an area-specific rate of ca. 12 L m− 2 d− 1 at the used densities. Da did not differ between the two polychaetes, suggesting a higher individual solute exchange efficiency of M. neglecta considering the much higher ventilation rates reported for H. diversicolor than for Marenzelleria sp. The ongoing colonization of Baltic Sea sediments by M. neglecta at high densities may thus lead to an enhanced soluble release of both nutrients and contaminants. These results add information to the understanding of the potential effects of the invasion of M. neglecta on sediment biogeochemistry when competing with and/or replacing native species.  相似文献   

9.
Colurella dicentra clones isolated from bay water in the Mississippi Gulf Coast were cultured with artificial seawater. Experiments were conducted to determine the effects of six algae species (Nannochloropsis oculata, Tetraselmis chuii, Chaetoceros gracilis, Rhodomonas salina, Isochrysis galbana, and Prorocentrum micans), six C. gracilis densities, and six N. oculata densities (25,000, 50,000, 100,000, 250,000, 500,000, and 1,000,000 cells ml− 1) on C. dicentra population growth. Algae type influenced rotifer production (p < 0.0001). C. gracilis treatment (9120 ± 3351SD) produced the highest number of rotifers followed by N. oculata (5760 ±2232SD). P. micans had the lowest number of rotifers, although not significantly different from numbers in T. chuii, R. salina, and I. galbana treatments (p > 0.05).The population growth rate (r) varied with algae species treatment. The highest values were recorded for C. gracilis treatment (0.22 to 0.26 d− 1), followed by N. oculata (0.21 to 0.24 d− 1), and the lowest for P. micans (− 0.19 to 0.14 d− 1). C. gracilis and N. oculata densities had significant effects (p < 0.0001) on C. dicentra population growth. The highest rotifer production was recorded at a C. gracilis density of 100,000 cells ml− 1, followed by 250,000 cells ml− 1 and 50,000 cells ml− 1. Algae densities of 500,000 cells ml− 1 and above produced the lowest rotifer numbers. Population growth rate (r) varied with C. gracilis densities. The highest values were observed for C. gracilis concentrations of 100,000 cells ml− 1 (0.17 to 0.19 d− 1), and the lowest for concentrations of 500,000 cells ml− 1 and above (− 0.19 to 0.09 d− 1). The 100,000 cells ml− 1N. oculata density gave the highest rotifer production followed by 50,000, 250,000, 25,000, and 500,000 cells ml− 1. Algae densities of 1,000,000 cells ml− 1 produced the lowest rotifer numbers. Population growth rate (r) varied with N. oculata densities, with the highest values obtained for algae densities of 100,000 cells ml− 1 (0.35 to 0.40 d− 1), and the lowest for concentrations of 1,000,000 cells ml− 1 (0.05 to 0.012 d− 1). This is the first report of C. dicentra in Mississippi Coastal waters, and perhaps the smallest marine rotifer species (93 by 49 μm) ever cultured successfully.  相似文献   

10.
Fluxes of oxygen, inorganic nitrogen (DIN) and denitrification (isotope pairing) were measured from January 1997 to February 1998 via intact cores incubation in a shallow brackish area within the eutrophic Valli di Comacchio (northern Adriatic coast, Italy). Rates were measured in the light and in the dark in sediments colonized by the rooted macrophyte Ruppia cirrhosa and in adjacent sediments with benthic microalgae. Ruppia biomass (25-414 g DW m− 2) exhibited a seasonal evolution whilst that of microphytobenthos (12-66 mg chl a m− 2) was more erratic. Net (NP) and gross (GP) primary productivity was 1.15 and 6.89 mol C m− 2y− 1 for bare and 25.4 and 51.7 mol C m− 2y− 1 for Ruppia vegetated sediments. Nitrogen pools in Ruppia standing stock varied from 43.6 to 631.4 (annual average 201.2) mmol N m− 2; the macrophyte N content was correlated with DIN concentration in the water column. Estimated N pool in microphytobenthos was one order of magnitude lower (from 2.4 to 14.5 mmol N m− 2, annual average 7.2). Theoretical DIN assimilation calculated from NP was 127.8 and 1112.6 mmol N m− 2y− 1 whilst that calculated from GP was 765 and 2282 mmol N m− 2y− 1 for microphytobenthos and Ruppia respectively. Measured annual fluxes of DIN were 974.6 and − 577 mmol N m− 2y− 1 in bare and Ruppia vegetated sediments meaning that the two sites were a source and sink for DIN and that from 25 to 50% of Ruppia annual DIN requirements came from the water column. During the period of this study total denitrification was lower in the macrophyte colonized (92.3 mmol N m− 2y− 1) compared to bare sediments (163.3 mmol N m− 2y− 1) as a probable consequence of higher competition between denitrifiers and phanerogams. At both sites the ratio between denitrification of water column nitrate (DW) and denitrification coupled to nitrification (DN) was >1.6 due to little oxygen penetration in reducing sediments (< 1.2 mm) and scarce nitrification activity. DW (0-35 µmol N m− 2h− 1) was significantly correlated with water column NO3−  (2-16 µM). Theoretical DIN assimilation to denitrification ratio varied from 12.0 to 24.8 for Ruppia vegetated and from 0.8 to 4.7 for unvegetated sediments.At Valle Smarlacca, Ruppia may influence nitrogen cycling by incorporating large DIN pools in biomass which is scattered in surrounding areas and fuels intense bacterial activity. With increasing anthropogenic nutrient input and insignificant organic matter export in the open sea the already severe eutrophic conditions are enhanced and may accelerate the decline of the macrophyte meadow.  相似文献   

11.
Previous work demonstrated that a mixture of NH4Cl and KNO3 as nitrogen source was beneficial to fed-batch Arthrospira (Spirulina) platensis cultivation, in terms of either lower costs or higher cell concentration. On the basis of those results, this study focused on the use of a cheaper nitrogen source mixture, namely (NH4)2SO4 plus NaNO3, varying the ammonium feeding time (T = 7-15 days), either controlling the pH by CO2 addition or not. A. platensis was cultivated in mini-tanks at 30 °C, 156 μmol photons m−2 s−1, and starting cell concentration of 400 mg L−1, on a modified Schlösser medium. T = 13 days under pH control were selected as optimum conditions, ensuring the best results in terms of biomass production (maximum cell concentration of 2911 mg L−1, cell productivity of 179 mg L−1 d−1 and specific growth rate of 0.77 d−1) and satisfactory protein and lipid contents (around 30% each).  相似文献   

12.
Absorbance difference spectroscopy and redox titrations have been applied to investigate the properties of photosystem I from the chlorophyll d containing cyanobacterium Acaryochloris marina. At room temperature, the (P740+ − P740) and (FA/B − FA/B) absorbance difference spectra were recorded in the range between 300 and 1000 nm while at cryogenic temperatures, (P740+A1 − P740A1) and (3P740 − P740) absorbance difference spectra have been measured. Spectroscopic and kinetic evidence is presented that the cofactors involved in the electron transfer from the reduced secondary electron acceptor, phylloquinone (A1), to the terminal electron acceptor and their structural arrangement are virtually identical to those of chlorophyll a containing photosystem I. The oxidation potential of the primary electron donor P740 of photosystem I has been reinvestigated. We find a midpoint potential of 450 ± 10 mV in photosystem I-enriched membrane fractions as well as in thylakoids which is very similar to that found for P700 in chlorophyll a dominated organisms. In addition, the extinction difference coefficient for the oxidation of the primary donor has been determined and a value of 45,000 ± 4000 M− 1 cm− 1 at 740 nm was obtained. Based on this value the ratio of P740 to chlorophyll is calculated to be 1:~ 200 chlorophyll d in thylakoid membranes. The consequences of our findings for the energetics in photosystem I of A. marina are discussed as well as the pigment stoichiometry and spectral characteristics of P740.  相似文献   

13.
The effect of pH-control modes on cell growth and exopolysaccharide production by Tremella fuciformis was evaluated in a 5-L bioreactor. The results show that the maximal dry cell weight (DCW) and exopolysaccharide production were 23.57 and 4.48 g L−1 in pH-stat fermentation, where the maximal specific growth rate (μmax) and specific production rate of exopolysaccharide (PP/X) were 1.03 and 0.24 d−1, respectively; under pH-shift cultivation, the maximal DCW and exopolysaccharide production were 30.57 and 3.90 g L−1, where the μmax and PP/X were 1.21 and 0.06 d−1. Unlike batch fermentation, maximal DCW and exopolysaccharide production merely reached 15.04 and 2.0 g L−1, where the μmax and PP/X were 0.86 and 0.05 d−1, respectively. These results suggest that a pH-stat strategy is a more efficient way of performing the fermentation process to increase exopolysaccharide production. Furthermore, this research has also proved that the three-stage pH-control mode is effective for cell growth.  相似文献   

14.
This study assesses the growth and morphological responses, nitrogen uptake and nutrient allocation in four aquatic macrophytes when supplied with different inorganic nitrogen treatments (1) NH4+, (2) NO3, or (3) both NH4+ and NO3. Two free-floating species (Salvinia cucullata Roxb. ex Bory and Ipomoea aquatica Forssk.) and two emergent species (Cyperus involucratus Rottb. and Vetiveria zizanioides (L.) Nash ex Small) were grown with these N treatments at equimolar concentrations (500 μM). Overall, the plants responded well to NH4+. Growth as RGR was highest in S. cucullata (0.12 ± 0.003 d−1) followed by I. aquatica (0.035 ± 0.002 d−1), C. involucratus (0.03 ± 0.002 d−1) and V. zizanioides (0.02 ± 0.003 d−1). The NH4+ uptake rate was significantly higher than the NO3 uptake rate. The free-floating species had higher nitrogen uptake rates than the emergent species. The N-uptake rate differed between plant species and seemed to be correlated to growth rate. All species had a high NO3 uptake rate when supplied with only NO3. It seems that the NO3 transporters in the plasma membrane of the root cells and nitrate reductase activity were induced by external NO3. Tissue mineral contents varied with species and tissue, but differences between treatments were generally small. We conclude, that the free-floating S. cucullata and I. aquatica are good candidate species for use in constructed wetland systems to remove N from polluted water. The rooted emergent plants can be used in subsurface flow constructed wetland systems as they grow well on any form of nitrogen and as they can develop a deep and dense root system.  相似文献   

15.
Fucogalactans from edible Agaricus bisporus (RFP-Ab) and wild Lactarius rufus (RFP-Lr) mushrooms were obtained on aqueous extraction followed by purification. RFP-Ab had Mw 43.8 × 104 g mol−1 and RFP-Lr Mw 1.4 × 104 g mol−1. RFP-Lr had a (1 → 6)-linked α-d-Galp main-chain partially substituted at O-2 by nonreducing end-units of α-l-Fucp (29%). While RFP-Ab had a similar main chain, it was partially substituted at O-2 by nonreducing end-units of α-l-Fucp (2.8%) and β-d-Galp (14.5%), and partially methylated at HO-3. Both RFP-Lr and RFP-Ab were tested in mice against polymicrobial sepsis. Lethality rate, myeloperoxidase (MPO) activity and cytokine levels were determined. It was observed a reduction in late mortality rate by 62.5% and 50%, respectively, prevention of neutrophil accumulation in ileum and decreasing in TNF-α and IL-1β serum levels.  相似文献   

16.
Glaucium flavum Crantz. is found in an anthropized coastal grassland at the joint estuary of the Tinto and Odiel rivers (SW Spain), growing under the influence of high levels of copper contamination derived from nearby petrochemical industries, with no obvious adverse affects on the performance of the plant. In addition, this species exhibits a series of ecological characteristics which may render it appropriate for use in the phytoremediation of contaminated areas. Nonetheless, the response of G. flavum to elevated copper concentrations has not been studied. A greenhouse experiment was conducted to investigate the effects of a range of Cu concentrations (0 to 47 mmol l−1) on the growth, reproduction and photosynthetic performance of G. flavum, by measuring relative growth rate, fruit and seed production, chlorophyll fluorescence parameters, gas exchange and photosynthetic pigment concentrations. We also determined total copper, nitrogen, phosphorous, sulphur, calcium and magnesium concentrations. G. flavum survived with concentrations of up to 730 mg Cu kg−1 DW in the leaves, when treated with 30 mmol Cu l−1 (2000 mg l−1). Quantum efficiency of PSII, net photosynthesis rate, as well as leaf Ca and Mg concentrations were all negatively affected by Cu concentrations greater than 9 mmol l−1 in the nutrient solution. Our results indicate that the reduction in photosynthetic performance may be attributed to the adverse effect of excess Cu on the photosynthetic apparatus of the plant, both directly, via a decrease in pigment concentrations, and indirectly, via interference of Cu with Ca ions of PSII. Growth and seed production were only slightly affected by leaf tissue concentrations as high as 230 mg Cu kg−1 dry mass, which suggests that this species could play an important role in phytoremediation of Cu-contaminated soils.  相似文献   

17.
The Iberian Peninsula encompasses more than 80% of the species richness of European aquatic ranunculi. The floristic diversity of the phytocoenosis characterised by aquatic Ranunculus and the main physical–chemical factors of the water were studied in 43 localities of the central Iberian Peninsula. Four aquatic Ranunculus communities are found in most of the aquatic environments. These are species-poor and have an uneven distribution: three species of Batrachium are heterophyllous and their communities are distributed in different aquatic ecosystems on silicated substrates; one species is homophyllous and its community occurs in various aquatic ecosystems with carbonated waters. In the Mediterranean climate, Ranunculus species are present in different habitats, as shown by the results of all the statistical analyses. Ranunculus trichophyllus communities occur in base-rich waters with a high buffering capacity (2273.44 ± 794.57 mg CaCO3 L−1) and a high concentration of cations (Ca2+, 121 ± 33.12 mg L−1; Mg2+, 71.64 ± 82.77 mg L−1), nitrates (2.89 ± 4.80 mg L−1), ammonium (2.19 ± 1.36 mg L−1) and sulphates (216.25 ± 218.54 mg L−1). Ranunculus penicillatus communities are found in flowing waters with a high concentration of phosphates (0.48 ± 0.6 mg L−1) and intermediate buffering capacity (683.66 ± 446.76 mg CaCO3 L−1). Both Ranunculus pseudofluitans and Ranunculus peltatus communities grow in waters with low buffering capacity (R. pseudofluitans, 385.91 ± 209.2 mg CaCO3 L−1; R. peltatus, 263.3 ± 180.36 mg CaCO3 L−1), and a low concentration of cations (R. pseudofluitans: Ca2+, 12.57 ± 9.42 mg L−1; Mg2+, 3.42 ± 1.67 mg L−1; R. peltatus: Ca2+, 15 ± 18.26 mg L−1; Mg2+, 6.26 ± 8.89 mg L−1) and nutrients (R. pseudofluitans: nitrates, 0.23 ± 0.2 mg L−1; phosphates, 0.09 ± 0.1 mg L−1; R. peltatus: nitrates, 0.19 ± 0.21 mg L−1; phosphates, 0.09 ± 0.12 mg L−1); the first in flowing waters, the latter in still waters.  相似文献   

18.
Two extracellular chitinases (designated as Chi-56 and Chi-64) produced by Massilia timonae were purified by ion-exchange chromatography, ammonium sulfate precipitation, and gel-filtration chromatography. The molecular mass of Chi-56 was 56 kDa as determined by both SDS-PAGE and gel-filtration chromatography. On the other hand, Chi-64 showed a molecular mass of 64 kDa by SDS-PAGE and 28 kDa by gel-filtration chromatography suggesting that its properties may be different from those of Chi-56. The optimum temperature, optimum pH, pI, Km, and Vmax of Chi-56 were 55 °C, pH 5.0, pH 8.5, 1.1 mg mL−1, and 0.59 μmol μg−1 h−1, respectively. For Chi-64, these values were 60 °C, pH 5.0, pH 8.5, 1.3 mg mL−1, and 1.36 μmol μg−1 h−1, respectively. Both enzymes were stimulated by Mn2+ and inhibited by Hg2+, and neither showed exochitinase activity. The N-terminal sequences of Chi-56 and Chi-64 were determined to be Q-T-P-T-Y-T-A-T-L and Q-A-D-F-P-A-P-A-E, respectively.  相似文献   

19.
The ability to cope with NH4+-N was studied in the littoral helophytes Phragmites australis and Glyceria maxima, species commonly occupying fertile habitats rich in NH4+ and often used in artificial wetlands. In the present study, Glyceria growth rate was reduced by 16% at 179 μM NH4+-N, and the biomass production was reduced by 47% at 3700 μM NH4+-N compared to NO3-N. Similar responses were not found in Phragmites. The amounts (mg g−1 dry wt) of starch and total non-structural carbohydrates (TNC) in rhizomes were significantly lower in NH4+ (8.9; 12.2 starch; 20.1; 41.9 TNC) compared to NO3 treated plants (28.0; 15.6 starch; 58.5; 56.3 TNC) in Phragmites and Glyceria, respectively. In addition, Glyceria showed lower amounts (mg g−1 dry wt) of soluble sugars, TNC, K+, and Mg2+ in roots under NH4+ (5.6; 14.3; 20.6; 1.9) compared to NO3 nutrition (11.6; 19.9; 37.9; 2.9, for soluble sugars, TNC, K+, and Mg2+, respectively), while root internal levels of NH4+ and Ca2+ (0.29; 4.6 mg g−1 dry wt, mean of both treatments) were only slightly affected. In Phragmites, no changes in soluble sugars, TNC, Ca2+, K+, and Mg2+ contents of roots (7.3; 14.9; 5.1; 17.3; 2.6 mg g−1 dry wt, means of both treatments) were found in response to treatments. The results, therefore, indicate a more pronounced tolerance towards high NH4+ supply in Phragmites compared to Glyceria, although the former may be susceptible to starch exhaustion in NH4+-N nutrition. In contrast, Glyceria's ability to colonize fertile habitats rich in NH4+ is probably related to the avoidance strategy due to shallow rooting or to the previously described ability to cope with high NH4+ levels when P availability is high and NO3 is also provided.  相似文献   

20.
The uptake kinetics of phosphate (Pi) by Myriophyllum spicatum was determined from adsorption and absorption under light and dark conditions. Pi uptake was light dependent and showed saturation following the Michaelis-Menten relation (in light: V = 16.91 × [Pi](1.335 + [Pi]), R2 = 0.90, p < 0.001; in the dark: V = 5.13 × [Pi](0.351 + [Pi]), R2 = 0.77, p < 0.001). Around 77% of the loss of Pi in the water column was absorbed into the tissue of M. spicatum, and only 23% was adsorbed on the surface of the plant shoots. Our study shows that M. spicatum shoots have a much higher affinity (in light: 3.9 μmol g−1 dw h−1 μM−1; in the dark: 3.7 μmol g−1 dw h−1 μM−1) and Vmax (maximum uptake rate, shoot light) for Pi uptake than many other aquatic macrophytes (in light: 0.002-0.23 μmol g−1 dw h−1 μM−1; in the dark: 0.002-0.19 μmol g−1 dw h−1 μM−1), which may provide a competitive advantage over other macrophytes across a wide range of Pi concentrations.  相似文献   

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