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1.

Background and Aims

Metal (e.g. Cd and Pb) pollution in agricultural soils and crops have aroused considerable attention in recent years. This study aimed to evaluate the effects of ROL and Fe plaque on Cd and Pb accumulation and distribution in the rice plant.

Methods

A rhizobag experiment was employed to investigate the correlations among radial oxygen loss (ROL), Fe plaque formation and uptake and distribution of Cd and Pb in 25 rice cultivars.

Results

Large differences between the cultivars were found in rates of ROL (1.55 to 6.88 mmol O2 kg?1 root d.w. h?1), Fe plaque formation (Fe: 6,117–48,167 mg kg?1; Mn: 127–1,089 mg kg?1), heavy metals in shoot (Cd: 0.13–0.35 mg kg?1; Pb: 4.8–8.1 mg kg?1) and root tissues (Cd: 1.1–3.5 mg kg?1; Pb: 45–199 mg kg?1), and in Fe plaque (Cd: 0.54–2.6 mg kg?1; Pb: 102–708 mg kg?1). Rates of ROL were positively correlated with Fe plaque formation and metal deposition on root surfaces, but negatively correlated with metal transfer factors of root/plaque and distributions in shoot and root tissues.

Conclusions

ROL-induced Fe plaque promotes metal deposition on to root surfaces, leading to a limitation of Cd and Pb transfer and distribution in rice plant tissues.  相似文献   

2.
Abelmoschus manihot, an ornamental plant, was examined for phytoremediation purposes in accordance with the ability to accumulate cadmium and physiological mechanisms of cadmium tolerance. A net photosynthetic rate (A N) glasshouse experiment for 60 days was conducted to investigate the influence of different cadmium amounts (0–100 mg kg?1) on the growth, biomass, photosynthetic performance, reactive oxygen species (ROS) production, antioxidative enzyme activities, Cd uptake and accumulation of A. manihot. Exposure to cadmium enhanced plant growth even at 100 mg kg?1, without showing symptoms of visible damage. The cadmium concentration of shoots (stems or leaves) and roots was more than the critical value of 100 mg kg?1 and reached 126.17, 185.26 and 210.24 mg kg?1, respectively. BCF values of A. manihot plants exceeded the reference value 1.0 for all the Cd treatments, and TF values were greater than 1 at 15–60 mg kg?1 Cd treatment. The results also showed that cadmium concentrations of 60 mg kg?1 or less induced a significant enhancement in plant net photosynthetic rate (A N), stomatal conductance (G s), transpiration rate (T r), photosynthetic pigments and F v/F m. These parameters were slightly decreased at the higher concentration (100 mg kg?1). The ROS production (O2 ?, H2O2) and antioxidative response including SOD, CAT and POD were significantly enhanced by increasing cadmium. These results suggest that A. manihot can be considered as a Cd-hyperaccumulator and the hormetic effects may be taken into consideration in remediation of Cd contamination soil.  相似文献   

3.

Background and aims

Much attention has focused on the effects of tropospheric ozone (O3) on terrestrial ecosystems and plant growth. Since O3 pollution is currently an issue in China and many parts of the world, understanding the effects of elevated O3 on soil carbon (C) and nitrogen (N) sequestration is essential for efforts to predict C and N cycles in terrestrial ecosystems under predicted increases in O3. Thus the main objective of this study was to determine whether an increases in atmospheric O3 concentration influenced soil organic C (SOC) and N sequestration.

Methods

A free-air O3 enrichment (O3-FACE) experiment was started in 2007 and used continuous O3 exposure from March to November each year during crop growth stage in a rice (Oryza sativa L.)—wheat (Triticum aestivum L.) rotation field in the Jiangsu Province, China. We investigated differences in SOC and N and soil aggregate composition in both elevated and ambient O3 conditions.

Results

Elevated atmospheric O3 (18–80 nmol mol?1 or 50 % above the ambient) decreased the SOC and N concentration in the 0–20 cm soil layer after 5 years. Elevated O3 significantly decreased the SOC concentration by 17 % and 5.6 % in the 0–3 cm and the 10–20 cm layers, respectively. Elevated O3 significantly decreased the N concentration by 8.2–27.8 % in three layers at the 20 cm depth. In addition, elevated O3 influenced the formation and transformation of soil aggregates and the distribution of SOC and N in the aggregates across soil layer classes. Elevated O3 significantly decreased the macro-sized aggregate fraction (16.8 %) and associated C and N (0.5 g kg?1 and 0.32 g kg?1, respectively), and significantly increased the silt+ clay-sized aggregate fraction (61 %) and associated C (1.7 g kg?1) in the 0–3 cm layer. Elevated O3 significantly decreased the macro-sized aggregate fraction (9.6 %) and associated C and N (1.4 g kg?1 and 0.35 g kg?1, respectively), and significantly increased the silt+ clay-sized aggregate fraction (41.8 %) and decreased the corresponding associated N (0.14 g kg?1) in the 3–10 cm layer. Elevated O3 did not significantly effect the formation and transformation of aggregates in the 10–20 cm layer, yet it did significantly increase the C concentration in the macro-sized fraction (1 g kg?1) and decrease the N concentration in the macro- and micro-sized fractions (0.24 g kg?1 and 0.16 g kg?1, respectively).

Conclusion

Long-term exposure to elevated atmospheric O3 negatively affected the physical structure of the soil and impaired soil C and N sequestration.  相似文献   

4.
The aim of this work was to investigate the effect of silicon (Si) on phenolic exudation of plant roots and cadmium (Cd) bioavailability in rhizospheres. For this purpose, pot experiments with two cypress varieties, Juniperus chinensis and Platycladus orientalis, each subjected to 100 mg kg?1 Cd and/or 400 mg kg?1 Si for 220 days, were conducted using a rhizobag technique. The results showed that P. orientalis accumulated a higher amount of Cd, hence caused higher growth inhibition on the leaves compared with J. chinensis. Si alleviated the growth inhibition induced by Cd toxicity on both varieties, but the mechanisms involved were species specific. For J. chinensis, Si did not affect the root exudation but enhanced the Cd retention of the roots by strengthening the exodermis tissues, restraining Cd translocation from the roots to the shoots. For P. orientalis, Si exposure significantly elevated the phenolic exudation (for example, ferulic acid, catechin, and gallic acid) of the roots, which caused greater Cd mobility in the rhizosphere and enhancement of Cd accumulation in the shoots compared with Cd treatment alone. These results suggest that Cd-chelating with the Si-induced phenolics in the rhizosphere is involved in the Cd detoxification in P. orientalis.  相似文献   

5.
Fluxes of dissolved organic carbon (DOC) and nitrogen (DON) may play an important role for losses of C and N from the soils of forest ecosystems, especially under conditions of high precipitation. We studied DOC and DON fluxes and concentrations in relation to precipitation intensity in a subtropical montane Chamaecyparis obtusa var. formosana forest in Taiwan. Our objective was, to quantify DOC and DON fluxes and to understand the role of high precipitation for DOC and DON export in this ecosystem. From 2005 to 2008 we sampled bulk precipitation, throughfall, forest floor percolates and seepage (60 cm) and analyzed DOC, DON and mineral N concentrations. Average DOC fluxes in the soil were extremely high (962 and 478 kg C ha?1 year?1 in forest floor percolates and seepage, respectively) while DON fluxes were similar to other (sub)tropical ecosystems (16 and 8 kg N ha?1 year?1, respectively). Total N fluxes in the soil were dominated by DON. Dissolved organic C and N concentrations in forest floor percolates were independent of the water flux. No dilution effect was visible. Instead, the pool size of potentially soluble DOC and DON was variable as indicated by different DOC and DON concentrations in forest floor percolates at similar precipitation amounts. Therefore, we hypothesized, that these pools are not likely to be depleted in the long term. The relationship between water fluxes in bulk precipitation and DOC and DON fluxes in forest floor percolates was positive (DOC r = 0.908, DON r = 0.842, respectively, Spearman rank correlation). We concluded, that precipitation is an important driver for DOC and DON losses from this subtropical montane forest and that these DOC losses play an important role in the soil C cycle of this ecosystem. Moreover, we found that the linear relationship between bulk precipitation and DOC and DON fluxes in forest floor percolates of temperate ecosystems does not hold when incorporating additional data on these fluxes from (subtropical) ecosystems.  相似文献   

6.

Aims

This study analyzed the extent to which root exudates diffuse from the root surface towards the soil depending on topsoil and subsoil properties and the effect of arbuscular mycorrhizal fungal hyphae on root-derived C distribution in the rhizosphere.

Methods

Alfalfa was grown in three-compartment pots. Nylon gauze prevented either roots alone or roots and arbuscular mycorrhizal fungal hyphae from penetrating into the rhizosphere compartments. 14CO2 pulse labeling enabled the measurement of 14C-labeled exudates in dissolved (DOC) and total organic carbon (TOC) in the rhizosphere, distributed either by diffusion alone or by diffusion, root hair and hyphal transport.

Results

Root exudation and microbial decomposition of exudates was higher in the rhizosphere with topsoil compared to subsoil properties. Exudates extended over 28 mm (DOC) and 20 mm (TOC). Different soil properties and mycorrhization, likely caused by the low arbuscular mycorrhizal colonization of roots (13?±?4 % (topsoil properties) and 18?±?5 % (subsoil properties)), had no effect.

Conclusions

Higher microbial decomposition compensated for higher root exudation into the rhizosphere with topsoil properties, which resulted in equal exudate extent when compared to the rhizosphere with subsoil properties. Higher 14C activity used for labeling compared with previous studies enabled the detection of low exudate concentrations at longer distances from the root surface.  相似文献   

7.

Background and aims

The selective inoculation of specific hydrocarbon-degrading microbes into the plant rhizosphere offers a useful means for remediating hydrocarbon-contaminated soils. The effect of inoculating a seed-borne filamentous fungus (Lewia sp.) on hydrocarbon removal by Festuca arundinacea and its growth was studied on perlite (model soil) and soil, both spiked with hydrocarbons.

Methods

A hydrocarbon mixture (1,500 mg kg?1) of two polycyclic aromatic hydrocarbons (PAH), phenanthrene and pyrene, blended with hexadecane (1.0:0.5:0.5 weight) was used. Greenhouse experiments were carried out for 45 days. Inoculated and non-inoculated plants were grown in dark cylindrical glass pots containing perlite or soil.

Results

Inoculation with Lewia sp. stimulated (100 %) root growth in spiked perlite. Inoculated plants showed higher phenanthrene removal (100 %) compared to non-inoculated plants in perlite and soil. Pyrene removal by inoculated plants was 37-fold higher than that by non-inoculated plants in perlite; in soil, pyrene removal by inoculated plants (97.9 %) differed significantly from that of non-inoculated plants (91.4 %). Accumulation of pyrene in roots (530.9 mg kg?1 of dry roots) was promoted in perlite.

Conclusions

Our results demonstrate that Lewia sp. (endophytic fungus) improved the efficiency of PAH removal by F. arundinacea, on both perlite and soil, stimulating pyrene accumulation in roots.  相似文献   

8.

Background and aims

Although the role of microbial iron respiration in tidal marshes has been recognized for decades, the effect of rhizosphere processes on dissimilatory ferric iron reduction (FeR) is poorly known. Herein, we examined the FeR surrounding the root zone of three tidal marsh plants.

Methods

Using in situ rhizoboxes, we accurately separated rhizobox soil as one rhizosphere zone, and three bulk soil zones. Dissimilatory and sulfidic-mediated FeR were quantified by accumulation of non-sulfidic Fe(II) and Fe sulfides over time, respectively.

Results

The rates of dissimilatory FeR attained 42.5 μmol Fe g?1 d?1 in the rhizosphere, and logarithmically declined by up to 19.1 μmol Fe g?1 d?1 in the outer bulk soil. The rates of sulfidic-mediated FeR were less than 2 μmol Fe g?1 d?1 among all zones. Poorly crystalline Fe(III), DOC and DON, porewater Fe2+, and SO42? were all enriched in the rhizosphere, whereas non-sulfidic Fe(II) and Fe sulfides gradually accumulated away from the roots. Iron reducers (Geobacter, Bacillus, Shewanella, and Clostridium) had higher populations in the rhizosphere than in the bulk soil. Higher rates of dissimilatory FeR were observed in the Phragmites australis and Spartina alterniflora rhizoboxes than in the Cyperus malaccensis rhizoboxes.

Conclusions

The radial change pattern of dissimilatory FeR rates were determined by allocation of poorly crystalline Fe(III) and dissolved organic carbon. The interspecies difference of rhizosphere dissimilatory FeR was associated with the root porosity and aerenchyma of the tidal marsh plants.
  相似文献   

9.
This study examined the effects of molybdenum (Mo) and boron (B) on the rhizosphere microorganisms and the soil enzyme activities of soybean. The soybeans were treated with seven different Mo and B supplements (control: without Mo and B) Mo1 (0.0185 g kg?1), B1 (0.08 g kg?1), Mo1 + B1 (0.0185 + 0.08 g kg?1), Mo2 (0.185 g kg?1), B2 (0.3 g kg?1) and Mo2 + B2 (0.185 + 0.3 g kg?1) throughout the plants’ four growth stages. The results showed that Mo, B, and combined Mo and B treatments increased the soil microbial populations, stimulated the rhizosphere metabolisms, and improved the soil enzyme activities. These stimulatory effects varied in intensity among the treatment groups. The Mo and B combination treatments were more beneficial for the soybean rhizosphere soil than that of Mo-only or the B-only treatments, which suggests that the two elements have complementary functions in the biological processes of the soybean rhizosphere.  相似文献   

10.

Background and aims

The impact of salinity on microbes has been studied extensively but little is known about the response of soil microbial activity and biomass to increasing salinity in rhizosphere compared to bulk (non-rhizosphere) soil.

Methods

Barley was grown for 5 weeks in non-saline loamy sand to which salt (NaCl) was added. The electrical conductivity in the saturated extract (ECe) was 1, 13 and 19 dS m?1 for non-saline and two saline soils. Pots without plants were prepared in the same manner and placed next to those with plants. The water content in all pots was maintained at 75 % of water-holding capacity by weight. After 5 weeks the planted and unplanted pots were harvested to collect rhizosphere and bulk soil, respectively. The collected soil was then used for an incubation experiment. The EC levels in the pot experiment (EC1, EC13 and EC19, referred to as original) were either maintained or increased by adding NaCl to adjust the EC to 13, 19, 31 and 44 dS m?1. CO2 release was measured continuously for 20 days, microbial biomass C (MBC) was measured at the start and the end of the incubation experiment.

Results

In general, cumulative respiration and microbial biomass C concentration in rhizosphere and bulk soil decreased to a similar extent with increasing adjusted EC. However, compared to the treatments where the EC was maintained, the percentage decrease in cumulative respiration when the EC was increased to EC44 was smaller in rhizosphere than in bulk soil.

Conclusion

Overall, the reduction of cumulative respiration with increasing salinity did not differ between rhizophere and bulk soil. But microbes in rhizosphere soil were more tolerant to high EC than those in bulk soil which could be due to the greater substrate availability in the rhizosphere even after the soil was removed from the roots.  相似文献   

11.
A two-year in-situ phytoremediation trial was launched in Shenyang Zhangshi (Sewage) Irrigation Area (SZIA). The phytoremediation efficiency of Solanum nigrum L. was determined, by both monitoring the change of soil Cadmium level in the upper 20 cm of soil, and calculating the plant uptake of soil Cd. After two years experimental, by monitoring the soil Cd concentrations, The Cd concentrations decreased on average from 2.75 mg kg?1to 2.45 mg kg?1 in the first year and from 2.33 mg kg?1 to 1.53 mg kg?1 in the second year, amounting to a decrease by a factor of 10.6% in the first year and 12% in the second year. After two years phytoremediation by S. nigrum, Cd concentrations of the seven experimental plots with S. nigrum growth decreased from 2.75 mg kg?1 to 1.53 mg kg?1, a decrease by a factor of 24.9%. And the soil Cd concentration decreased only 2.1% and 1.7% in the bared experimental plot. And the calculating of Cd uptake by S. nigrum shown that, the plants uptake 4.46% and 5.18% of the total soil Cd in 2008 and 2009, while the soil Cd concentrations decreased by a factor of 10.6% in 2008 and 12.1% in 2009.  相似文献   

12.

Aims

The current study aimed to assess the potential of peanut (Arachis hypogaea L.) for bioenergy production via phytoextraction in cadmium (Cd) -contaminated soils and screen appropriate cultivars for this approach.

Methods

A life-cycle pot experiment was conducted to determine the biomass, seed yield, oil content and Cd accumulation of seven peanut cultivars under Cd concentration gradients of 0, 2, and 4 mg kg?1.

Results

Peanut exhibits genotypic variations in Cd tolerance, seed production, oil content, and Cd accumulation. Exposure of plants to 2 and 4 mg kg?1 Cd did not inhibit shoot biomass, seed yield, and oil content for most of the cultivars tested. There are large amounts of Cd accumulated in the shoots. Although the seed Cd concentration of peanut was relatively high, the Cd concentration in seed oils was very low (0.04-0.08 mg kg?1). Among the cultivars, Qishan 208 showed significant Cd tolerance, high shoot biomass, high pod and seed yield, high seed oil content, considerable shoot Cd concentration, and the largest translocation factor and total Cd in shoots.

Conclusions

The cultivation of peanut in Cd-contaminated farmland was confirmed to be feasible for bioenergy production via phytoextraction, and Qishan 208 is a good candidate for this approach.  相似文献   

13.

Aims

Responses of typical wetland plant Acorus tatarinowii to diesel stress were investigated to provide basis of ecological monitoring system and phytoremediation for diesel-contaminated wetland.

Methods

Greenhouse experiments were established to determine the germinability of seedlings, hydrogen peroxide in leaves, and DNA damage in roots exposed to a range of potentially phytotoxic diesel.

Results

The presence of diesel did not benefit the growth of A. tatarinowii. The germination ratio and germination rate decreased with the increase of diesel concentration, both the lowest value appeared when the concentration of diesel was 10,000 mg?kg?1. The lowest diesel concentration (2,000 mg?kg?1) in the soil significantly reduced the length, average diameter, and projected area of root, especially on the stress of the higher diesel concentration (4,000, 8,000, and 10,000 mg?kg?1). Furthermore, H2O2 concentration in leaves rose with the increasing concentration of diesel. However, no DNA oxidative damage to root was observed in our experiment.

Conclusions

Diesel exposure significantly inhabited the seed germination, root elongation, and seedlings growth of A. tatarinowii. Diesel stress caused the accumulation of H2O2 in the leaves of A. tatarinowii.  相似文献   

14.
To ultimately determine whether different levels of soil nitrogen (N) deposition can modify the detrimental effects of cadmium (Cd), the seedlings of Toxicodendron vernicifluum (Strokes) F. A. Barkley were exposed to soil Cd stress (0, 5 and 15 mg kg?1 dry soil), N deposition (0, 13 and 40 mg kg?1 dry soil) and their combinations. Soil Cd stress caused damage in plant growth, photosynthesis and other physiological indexes, and in the ultrastructure of mesophyll cells. The effects of N deposition on growth, lipid peroxidation and enzyme activities depended on the relative amounts of N supplied. The combination of low N deposition and Cd stress was positive to plant growth, photosynthesis and enzyme activities, and it caused lower levels of Cd accumulation and lipid peroxidation compared with the effect of Cd stress alone. The combination of high N deposition and Cd stress led to a higher Cd accumulation and lipid peroxidation, and to lower enzyme activities, as compared with the effect of Cd stress alone. T. vernicifluum was found to be sensitive to soil Cd stress. Soil Cd had detrimental effects on T. vernicifluum seedlings, but the tolerance of T. vernicifluum to Cd increased under low N deposition.  相似文献   

15.
Cadmium (Cd) pollution around the world is a serious issue demanding acceptable solutions, one of which is phytoremediation that is both cost-effective and eco-friendly. Removal of Cd from contaminated water using plants with high growth rates and sufficient Cd accumulation abilities could be an appropriate choice. Here, we investigated a potential Cd accumulator, Wolffia, a rootless duckweed with high growth rate. Cd uptake, accumulation, tolerance, and phytofiltration ability by Wolffia globosa were examined. Furthermore, the effects of arsenic (As) on Cd uptake and phytofiltration by W. globosa were also studied. Cd uptake kinetics showed a linear pattern and a hyperbolic pattern without a plateau in lower (0–2 μM) and higher (0–200 μM) Cd concentration ranges, respectively, suggesting rapid Cd uptake by W. globosa. Cd accumulation ability by W. globosa was higher at Cd concentrations < 10 μM than at >10 μM. All the five species of Wolffia exposed to 1 μM Cd for 5 days accumulated > 500 mg Cd kg?1 DW. Ten gram fresh W. globosa could diminish almost all the Cd (2 μM) in a 200 mL solution. This enormous accumulation ability was mostly due to passive adsorption of Cd by the apoplast. Arsenic had no significant effect on Cd uptake and phytofiltration. The fresh fronds also showed a great As extracting ability. The results indicated that Wolffia is a strong Cd accumulator and has great Cd phytoremediation potential. Therefore, this plant can be used in fresh aquatic environments co-contaminated by low-levels of Cd and As.

Supplemental materials are available for this article. Go to the publisher's online edition of International Journal of Phytoremediation to view the supplemental file.  相似文献   

16.
A long-term experiment was conducted to investigate the alleviative effects of silicon (Si) on cadmium (Cd) toxicity in garlic plants grown in pots. Cd and Si were introduced into soil before sowing. Cd was added at a rate of 20 mg kg?1 soil, and Si was applied at two rates: 50 mg SiO2 kg?1 (Si1) and 500 mg SiO2 kg?1 (Si2). There were totally six treatments consisting of CT (control, no added Cd or Si), Si1, Si2, Cd, Cd + Si1, and Cd + Si2. The results showed that Si addition did not affect the growth of garlic plants under control conditions. Under Cd stress, the plant growth and PSII quantum efficiency were inhibited, and they were significantly improved in the presence of added Si. Added Si at Si1 level did not change the soil pH and Cd availability, while it increased Cd accumulation in both shoot and bulb, and improved Cd tolerance. Si added at Si2 level increased the soil pH and decreased Cd availability, and decreased Cd accumulation in different parts of the plant. Added Si had no effect on the activities of soil catalase, urease or invertase regardless of Cd presence. The results suggest that Si could increase Cd tolerance of garlic plants, and the tolerance increase was attributed to not only decreased Cd availability but also in planta detoxification mechanism. There is no evidence indicating that Si-mediated increase of Cd tolerance is related to improved soil microorganism environment as observed in biotic stress conditions.  相似文献   

17.

Background and aims

Wetlands are important carbon sinks across the planet. However, soil carbon sequestration in tropical freshwater wetlands has been studied less than its counterpart in temperate wetlands. We compared carbon stocks and carbon sequestration in freshwater wetlands with various geomorphic features (estuarine, perilacustrine and depressional) and various plant communities (marshes and swamps) on the tropical coastal plain of the Gulf of Mexico in the state of Veracruz, Mexico. These swamps are dominated by Ficus insipida, Pachira aquatic and Annona glabra and the marshes by Typha domingensis, Thalia geniculata, Cyperus giganteus, and Pontederia sagittata.

Methods

The soil carbon concentration and bulk density were measured every 2 cm along 80 cm soil profiles in five swamps and five marshes. Short-term sediment accretion rates were measured during a year using horizontal makers in three of the five swamps and marshes, the carbon sequestration was calculated using the accretion rates, and the bulk density and the percentage of organic carbon in the surficial layer was measured.

Results

The average carbon concentration ranged from 50 to 150 gC kg?1 in the marshes and 50 to 225 gC kg?1 in the swamps. When the wetlands were grouped according to their geomorphic features, no significant differences in the carbon stock (P?=?0.095) were found (estuarine (25.50?±?2.26 kgC m?2), perilacustrine (28.33?±?2.74 kgC m?2) and depressional wetlands (34.93?±?4.56 kgC m?2)). However, the carbon stock was significantly higher (P?=?0.030) in the swamps (34.96?±?1.3 kgC m?2) than in the marshes (25.85?±?1.19 kgC m?2). The average sediment accretion rates were 1.55?±?0.09 cm yr?1 in the swamps and 0.84?±?0.02 cm yr?1 in the marshes with significant differences (P?=?0.040). The rate of carbon sequestration was higher (P?=?0.001) in swamp soils (0.92?±?0.12 kgC m?2 yr?1) than marsh soils (0.31?±?0.08 kgC m?2 yr?1). Differences in the rates of carbon sequestration associated with geomorphic features were found between the swamp ecosystems (P?<?0.05); i.e., higher values were found in the swamps than in the marshes in perilacustrine and estuarine wetlands (P?<?0.05). However, no significant differences (P?=?0.324) in carbon sequestration rates were found between the marsh and swamp areas of the depressional site.

Conclusions

Swamp soils are more important contributors to the carbon stock and sequestration than are marsh soils, resulting in a reduction in global warming, which suggests that the plant community is an important factor that needs to be considered in global carbon budgets and projects of restoration and conservation of wetlands.  相似文献   

18.

Background and aims

Sufficient soil phosphorus (P) is important for achieving optimal crop production, but excessive soil P levels may create a risk of P losses and associated eutrophication of surface waters. The aim of this study was to determine critical soil P levels for achieving optimal crop yields and minimal P losses in common soil types and dominant cropping systems in China.

Methods

Four long-term experiment sites were selected in China. The critical level of soil Olsen-P for crop yield was determined using the linear-plateau model. The relationships between the soil total P, Olsen-P and CaCl2-P were evaluated using two-segment linear model to determine the soil P fertility rate and leaching change-point.

Results

The critical levels of soil Olsen-P for optimal crop yield ranged from 10.9 mg kg?1 to 21.4 mg kg?1, above which crop yield response less to the increasing of soil Olsen-P. The P leaching change-points of Olsen-P ranged from 39.9 mg kg?1 to 90.2 mg kg?1, above which soil CaCl2-P greatly increasing with increasing soil Olsen-P. Similar change-point was found between soil total P and Olsen-P. Overall, the change-point ranged from 4.6 mg kg?1 to 71.8 mg kg?1 among all the four sites. These change-points were highly affected by crop specie, soil type, pH and soil organic matter content.

Conclusions

The three response curves could be used to access the soil Olsen-P status for crop yield, soil P fertility rate and soil P leaching risk for a sustainable soil P management in field.  相似文献   

19.
A study quantifying the interactive effects of cadmium (Cd) and carbon nanotubes (CNTs) on plant growth and Cd accumulation of pot-cultured Spartina alterniflora was conducted. The experiment consisted of two Cd levels (50, 200 mg kg?1) as well as two CNTs levels (800, 2,400 mg kg?1). As expected, CNTs alleviated higher Cd stress (200 mg kg?1) due to restored shoot growth reduction, retrieved water content and resumed plant height. Furthermore, CNTs mitigated the deleterious effects of Cd stress through improving K+ and Ca2+ contents, while reducing Na+/K+ and Na+/Ca2+ ratios, regardless of the level of Cd stress. The proline contents in combined Cd and CNTs treatments were lower than Cd alone, suggesting that CNTs could reduce production of organic solutes under Cd stress. The results also showed higher Cd accumulation in roots than shoots, and both were improved by CNTs, except inhibition in roots under higher Cd stress (200 mg kg?1). It appears that CNTs may not significantly affect negative Cd effects on growth of S. alterniflora, but improve total Cd accumulation under lower Cd stress (50 mg kg?1). However, under higher Cd stress (200 mg kg?1), CNTs restored the reduced plant growth, improved and reduced Cd accumulation in shoots and roots, respectively. Therefore, the effects of CNTs on plant growth and Cd accumulation are different, and levels of Cd stress should be considered when evaluating the combined application of CNTs and S. alterniflora on phytoremediation of Cd pollution.  相似文献   

20.
Phytoextraction of Risk Elements by Willow and Poplar Trees   总被引:1,自引:0,他引:1  
To characterize the phytoextraction efficiency of two clones of willow trees (Salix x smithiana Willd., Salix rubens) and two clones of poplar trees (Populus nigra x maximowiczii, Populus nigra Wolterson) were planted in contaminated soil (0.4–2.0 mg Cd.kg?1, 78–313 mg Zn.kg?1, 21.3–118 mg Cu.kg?1). Field experiment was carried out in Czech Republic. The study investigated their ability to accumulate heavy metals (Cd, Zn, and Cu) in harvestable plant parts. The poplars produced higher amount of biomass than willows. Both Salix clones accumulated higher amount of Cd, Zn and Cu in their biomass (maximum 6.8 mg Cd.kg?1, 909 mg Zn.kg?1, and 17.7 mg Cu.kg?1) compared to Populus clones (maximum 2.06 mg Cd.kg?1, 463 mg Zn.kg?1, and 11.8 mg Cu.kg?1). There were no significant differences between clones of individual species. BCs for Cd and Zn were greater than 1 (the highest in willow leaves). BCs values of Cu were very low. These results indicate that Salix is more suitable plant for phytoextraction of Cd and Zn than Populus. The Cu phytoextraction potential of Salix and Populus trees was not confirmed in this experiment due to low soil availability of this element.  相似文献   

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