The traditional culture-dependent plate counting and culture-independent small-subunit-ribosomal RNA gene-targeted molecular techniques, Single-Strand Conformation Polymorphism (SSCP) and ter-minal Restriction Fragmen...The traditional culture-dependent plate counting and culture-independent small-subunit-ribosomal RNA gene-targeted molecular techniques, Single-Strand Conformation Polymorphism (SSCP) and ter-minal Restriction Fragment Length Polymorphism (tRFLP) combined with 16S rDNA clone library were adopted to investigate the impacts of secretion from Camptotheca acuminata (abbreviated to Ca) roots on the quantities and structure of eukaryotic microbes and bacteria in the rhizosphere, and the possi-bility that Ca controls exotic invasive plant Eupatorium adenophorum (Ea). The counting results indi-cated that the number of bacteria increased in turn in rhizospheres of Ea, Ca-Ea mixed culture and Ca, while that of eukaryotic microbes decreased. PCR-SSCP profiles showed eukaryotic microbial bands (corresponding to biodiversity) in rhizosphere of Ea were more complex than those of Ca and CE. Meristolohmannia sp., Termitomyces sp. and Rhodophyllus sp. were the dominant populations in the rhizosphere of Ca. Bacterial terminal restriction fragments (TRFs) profiles showed no difference among three kinds of rhizospheres, and the sequences of the 16S rDNA clone library from Ca rhizospheres were distributed in 10 known phyla, in which phylum Proteobacteria were the absolute dominant group and accounted for 24.71% of the cloned sequences (δ-Proteobacteria accounted for up to 17.65%), and phyla Acidobacteria and Bacteroidetes accounted for 16.47% and 10.59% of the cloned sequences, respectively. In addition, high performance liquid chromatography detected a trace amount of camp-tothecin and hydroxycamptothecin in the rhizospheric soil of Ca and CE, but examined neither camp-tothecin nor hydroxycamptothecin in rhizospheric soil of Ea. Therefore, invasion and diffusion of Ea evidently depended on distinguishing the eukaryotic community structure, but not on that of the bac-terial pattern. Ca was able to alter the eukaryotic community structure of invasive Ea by secreting camptothecin and hydroxycamptothecin into rhizospheres, and may bene展开更多
Biological control agents and soil amendments have been applied to control tobacco bacterial wilt, but the mechanism is not well-known. In the present study, a field experiment was performed to investigate the soil ph...Biological control agents and soil amendments have been applied to control tobacco bacterial wilt, but the mechanism is not well-known. In the present study, a field experiment was performed to investigate the soil physicochemical properties, disease index (DI) and disease incidence of tobacco bacterial wilt, and rhizosphere microbial community. The results show that the control efficacy of single application of antagonistic bacteria and calcium cyanamide was 46.43% and 51.92%, respectively. While the combined control efficacy of antagonistic bacteria and calcium cyanamide was 65.79%. Besides, the combined application of antagonistic bacteria and calcium cyanamide could increase soil pH, total N alkaline N, and exchangeable Ca, which were negatively associated with the microbial diversity, soil-borne pathogenic microorganisms, and incidence of tobacco bacterial wilt. Additionally, the combination of antagonistic bacteria and calcium cyanamide can improve the proportion of some antagonistic microbial species, and these antagonistic microbial species were inversely associated with the DI of tobacco bacterial wilt. In conclusion: The integrated measure may influence soil microbial communities through enhancing soil physicochemical properties and rebuild healthy soil microbial community structure to mitigate tobacco bacterial wilt. The current study presented valuable insights into the mechanisms enhancing soil health in the integrated measure.展开更多
A pot experiment was conducted to investigate the biodegradation dynamics and related microbial ecophysiological responses to butachlor addition in a riparian soil planted with different plants such as Phragmites aust...A pot experiment was conducted to investigate the biodegradation dynamics and related microbial ecophysiological responses to butachlor addition in a riparian soil planted with different plants such as Phragmites australis,Zizania aquatica,and Acorus calamus.The results showed that there were significant differences in microbial degradation dynamics of butachlor in the rhizosphere soils among the three riparian plants.A.calamus displays a significantly higher degradation efficiency of butachlor in the rhizosphere soils,as compared with Z.aquatica and P.australis.Half-life time of butachlor degradation in the rhizospheric soils of P.australis,Z.aquatica,and A.calamus were 7.5,9.8 and 5.4 days,respectively.Residual butachlor concentration in A.calamus rhizosphere soil was 35.2% and 21.7% lower than that in Z.aquatica and P.australis rhizosphere soils,respectively,indicating that A.calamus showed a greater improvement effect on biodegradation of butachlor in rhizosphere soils than the other two riparian plant.In general,microbial biomass and biochemical activities in rhizosphere soils were depressed by butachlor addition,despite the riparian plant types.However,rhizospheric soil microbial ecophysiological responses to butachlor addition significantly （P 0.05） differed between riparian plant species.Compared to Z.aquatica and P.australis,A.calamus showed significantly larger microbial number,higher enzyme activities and soil respiration rates in the rhizosphere soils.The results indicated that A.calamus have a better alleviative effect on inhibition of microbial growth due to butachlor addition and can be used as a suitable riparian plant for detoxifying and remediating butachlor contamination from agricultural nonpoint pollution.展开更多
To have a preliminary insight into biosafety of genetically transformed hybrid triploid poplars （Populus tomentosa × P bolleana）× P. tomentosa with the cowpea trypsin inhibitor （CpTD gene, two layers of r...To have a preliminary insight into biosafety of genetically transformed hybrid triploid poplars （Populus tomentosa × P bolleana）× P. tomentosa with the cowpea trypsin inhibitor （CpTD gene, two layers of rhizospheric soil （from 0 to 20cm deep and from 20 to 40cm deep, respectively） were collected for microorganism culture, counting assay and PCR analysis to assess the potential impact of transgenic poplars on non-target microorganism population and transgene dispersal. When the same soil layer of suspension stock solution was diluted at both 1：1000 and 1：10000 rates, there were no significant differences in bacterium colony numbers between the inoculation plates of both transgenic and non-transgenic poplars. The uniform results were revealed for both soil layer suspension solutions of identical poplars at both dilution rates except for non-transgenic poplars at 1：10000 dilution rates from the same type of soil. No significant variation in morphology of both Gram-positive and Gram-negative bacteria was observed under the microscope. The potential transgene dispersal from root exudates or fallen leaves to non-target microbes was repudiated by PCR analysis, in which no CpTI gene specific DNA band was amplified for 15 sites of transgenic rhizospheric soil samples. It can be concluded that transgenic poplar with the CpTI gene has no severe impact on rhizospheric microorganisms and is tentatively safe to surrounding soil micro-ecosystem.展开更多
<p align="justify"> <span style="font-family:Verdana;">Soil salinization is one of the major causes of land degradation. In Senegal, this phenomenon continues to grow, making soils unsu...<p align="justify"> <span style="font-family:Verdana;">Soil salinization is one of the major causes of land degradation. In Senegal, this phenomenon continues to grow, making soils unsuitable for agriculture. To rehabilitate salty lands, one of the recommended strategies is the use of salt-tolerant plants. Among them, plants of </span><i><i><span style="font-family:Verdana;">Casuarinaceae</span></i></i><span style="font-family:Verdana;"> family form a relationship with symbiotic microorganisms such as arbuscular mycorrhizal fungi and nitrogen fixing bacteria. It has been shown that symbiotic microorganisms play an important role in the establishment of tolerant plants in saline conditions (Djighaly </span><i><i><span style="font-family:Verdana;">et al</span></i></i><span style="font-family:Verdana;">., 2018). They improve plant performance and reduce transplant shock under salt stress conditions (Diagne </span><i><i><span style="font-family:Verdana;">et al</span></i></i><span style="font-family:Verdana;">., 2014). These microorganisms can be used as biofertilizers. However, inocula containing symbiotic microorganisms are either too expensive or unavailable in many developing countries. The aim of this study is to test alternatively affordable and low-tech solutions to promote symbiotic interactions such as Casuarina crushed nodule, Casuarina rhizosphere soil and Casuarina leaves compost that may contain symbiotic microorganisms and also nutrients such as N and phosphorus. Two species of Casuarina (</span><i><i><span style="font-family:Verdana;">Casuarina equisetifolia</span></i></i><span style="font-family:Verdana;"> L. and </span><i><i><span style="font-family:Verdana;">Casuarina obesa</span></i></i><span style="font-family:Verdana;"> Miq.) were grown in the greenhouse on sterile soil to which an amendment was added (Casuarina crushed nodules, Casuarina Rhizospheric soil or Casuarina leaves compost). Plants were subjected to saline stress. After four months of cultivation, they were harvested and morphological a展开更多
The contamination of arsenic (As) and other heavy metal (HMs) in soil causes serious health hazard to the ecosystem. In this work, the contamination of As and other heavy metals (i.e. Ti, V, Cr, Mn, Fe, Ni, Cu, Zn and...The contamination of arsenic (As) and other heavy metal (HMs) in soil causes serious health hazard to the ecosystem. In this work, the contamination of As and other heavy metals (i.e. Ti, V, Cr, Mn, Fe, Ni, Cu, Zn and Pb) in rhizospheric soil of 14 plants of the severely As contaminated area of Central India is described. Among them, high content of As in the rhizospheric soils was observed, ranging from 0.22 to 4.60 g/kg with mean value of 1.6 ± 0.7 g/kg. The concentration variation, enrichment indices and toxicities of the metals in the soil are described.展开更多
Biosurfactants are biomolecules produced by microorganisms, low in toxicity, biodegradable, and relatively easy to synthesize using renewable waste substrates. Biosurfactants are of great importance with a wide and ve...Biosurfactants are biomolecules produced by microorganisms, low in toxicity, biodegradable, and relatively easy to synthesize using renewable waste substrates. Biosurfactants are of great importance with a wide and versatile range of applications, including the bioremediation of contaminated sites. Plants may accumulate soil potentially toxic elements(PTEs), and the accumulation efficacy may be further enhanced by the biosurfactants produced by rhizospheric microorganisms. Occasionally, the growth of bacteria slows down in adverse conditions, such as highly contaminated soils with PTEs. In this context,the plant's phytoextraction capacity could be improved by the addition of metal-tolerant bacteria that produce biosurfactants. Several sources, categories,and bioavailability of PTEs in soil are reported in this article, with the focus on the cost-effective and sustainable soil remediation technologies, where biosurfactants are used as a remediation method. How rhizobacterial biosurfactants can improve PTE recovery capabilities of plants is discussed, and the molecular mechanisms in bacterial genomes that support the production of important biosurfactants are listed. The status and cost of commercial biosurfactant production in the international market are also presented.展开更多
Oyster shell soil conditioner had significant influence on soil and rhizospheric microorganisms in their biomass,respiratory intensity and nutritional requirement. It could stimulate growth of soil and rhizospheric mi...Oyster shell soil conditioner had significant influence on soil and rhizospheric microorganisms in their biomass,respiratory intensity and nutritional requirement. It could stimulate growth of soil and rhizospheric microorganisms, especially nitrogen-fixers, and intensify soil respiration in proportion to the dose and fertilizing time of the conditioner, leading to the increase in the number of nitrogen fixing bacteria and the decrease in the number of bacteria with special nutrition demands.展开更多
In order to promote the development and application of environmental-friendly,efficient and safe beneficial Bacillus sp.preparations,the paper summarizes and systematically elaborates the colonization of Bacillus sp.i...In order to promote the development and application of environmental-friendly,efficient and safe beneficial Bacillus sp.preparations,the paper summarizes and systematically elaborates the colonization of Bacillus sp.in host plants and the mechanism of synergistic effect on disease prevention of host plants,further reviews the application of rhizospheric Bacillus sp.in promoting the growth of agricultural and forestry crops and controlling plant diseases,and prospects the scientific issues and application of plant rhizospheric Bacillus sp.in the future.展开更多
Studies on mechanisms and efficiencies of wastewater treatment with constructed wetland,mainly from developed countries,conducted mainly in the past 2 decades are reviewed.The mechanisms of wastewater treatment by wet...Studies on mechanisms and efficiencies of wastewater treatment with constructed wetland,mainly from developed countries,conducted mainly in the past 2 decades are reviewed.The mechanisms of wastewater treatment by wetlands are extremely complicated,including a series of physical,chemical,and bio chemical processes,such as special and non special adsorption,exchange,sedimentation,assimilation,decomposition,volatilization,and so on.There are lots of components,e.g.plants,soils,and microorganisms,in wetlands making contributions to water quality improvement.Of all plants in constructed wetlands, Phragmites communis is used most widely and frequently.But wetlands covered by this single species are inferior to those covered by many species including it and other plants with reference to removal efficiency of nutrients and pollutants.In order to consummate theories about constructed wetlands for wastewater treatment,and to further improve removal efficiencies of pollutants and wetland ecosystem health,the following research fields are suggested to consolidate or further conduct in the future:① deeper and more systemic research on mechanisms of wastewater purification by wetlands;② studies on sustainable development of constructed wetland;③ experimentation on the suitability of local and indigenous wetland macrophytes for removal of nutrients and heavy metals from different types of wastewater;④ exploration for better constructing,maintaining,and using measures to maximize the wastewater treatment efficiency;⑤ controlling disease vectors and animal pests,and preventing them from jeopardizing human health and lives;and ⑥ ascertaining reasons producing noxious and odorous gases and then trying to control them effectively.展开更多
基金the Excellent Young Teacher’s Innovation Foundation of Northeast Forestry University to Yang FengJian,the Key Research Fund of Ministry of Educa-tion of China (Grant No.104191) the Forestry Noxious Plant Investigation Fund of State Forestry Administration of China to Zu YuanGang
文摘The traditional culture-dependent plate counting and culture-independent small-subunit-ribosomal RNA gene-targeted molecular techniques, Single-Strand Conformation Polymorphism (SSCP) and ter-minal Restriction Fragment Length Polymorphism (tRFLP) combined with 16S rDNA clone library were adopted to investigate the impacts of secretion from Camptotheca acuminata (abbreviated to Ca) roots on the quantities and structure of eukaryotic microbes and bacteria in the rhizosphere, and the possi-bility that Ca controls exotic invasive plant Eupatorium adenophorum (Ea). The counting results indi-cated that the number of bacteria increased in turn in rhizospheres of Ea, Ca-Ea mixed culture and Ca, while that of eukaryotic microbes decreased. PCR-SSCP profiles showed eukaryotic microbial bands (corresponding to biodiversity) in rhizosphere of Ea were more complex than those of Ca and CE. Meristolohmannia sp., Termitomyces sp. and Rhodophyllus sp. were the dominant populations in the rhizosphere of Ca. Bacterial terminal restriction fragments (TRFs) profiles showed no difference among three kinds of rhizospheres, and the sequences of the 16S rDNA clone library from Ca rhizospheres were distributed in 10 known phyla, in which phylum Proteobacteria were the absolute dominant group and accounted for 24.71% of the cloned sequences (δ-Proteobacteria accounted for up to 17.65%), and phyla Acidobacteria and Bacteroidetes accounted for 16.47% and 10.59% of the cloned sequences, respectively. In addition, high performance liquid chromatography detected a trace amount of camp-tothecin and hydroxycamptothecin in the rhizospheric soil of Ca and CE, but examined neither camp-tothecin nor hydroxycamptothecin in rhizospheric soil of Ea. Therefore, invasion and diffusion of Ea evidently depended on distinguishing the eukaryotic community structure, but not on that of the bac-terial pattern. Ca was able to alter the eukaryotic community structure of invasive Ea by secreting camptothecin and hydroxycamptothecin into rhizospheres, and may bene
文摘Biological control agents and soil amendments have been applied to control tobacco bacterial wilt, but the mechanism is not well-known. In the present study, a field experiment was performed to investigate the soil physicochemical properties, disease index (DI) and disease incidence of tobacco bacterial wilt, and rhizosphere microbial community. The results show that the control efficacy of single application of antagonistic bacteria and calcium cyanamide was 46.43% and 51.92%, respectively. While the combined control efficacy of antagonistic bacteria and calcium cyanamide was 65.79%. Besides, the combined application of antagonistic bacteria and calcium cyanamide could increase soil pH, total N alkaline N, and exchangeable Ca, which were negatively associated with the microbial diversity, soil-borne pathogenic microorganisms, and incidence of tobacco bacterial wilt. Additionally, the combination of antagonistic bacteria and calcium cyanamide can improve the proportion of some antagonistic microbial species, and these antagonistic microbial species were inversely associated with the DI of tobacco bacterial wilt. In conclusion: The integrated measure may influence soil microbial communities through enhancing soil physicochemical properties and rebuild healthy soil microbial community structure to mitigate tobacco bacterial wilt. The current study presented valuable insights into the mechanisms enhancing soil health in the integrated measure.
基金supported by the Foundation of the State Key Laboratory of Pollution Control and Resource Reuse of China (No.PCRY09005)the National Special Item on Water Resource and Environment (No.2008ZX07316-4)the Key Project in the National Science & Technology Pillar Program (No.2009BAC62B00)
文摘A pot experiment was conducted to investigate the biodegradation dynamics and related microbial ecophysiological responses to butachlor addition in a riparian soil planted with different plants such as Phragmites australis,Zizania aquatica,and Acorus calamus.The results showed that there were significant differences in microbial degradation dynamics of butachlor in the rhizosphere soils among the three riparian plants.A.calamus displays a significantly higher degradation efficiency of butachlor in the rhizosphere soils,as compared with Z.aquatica and P.australis.Half-life time of butachlor degradation in the rhizospheric soils of P.australis,Z.aquatica,and A.calamus were 7.5,9.8 and 5.4 days,respectively.Residual butachlor concentration in A.calamus rhizosphere soil was 35.2% and 21.7% lower than that in Z.aquatica and P.australis rhizosphere soils,respectively,indicating that A.calamus showed a greater improvement effect on biodegradation of butachlor in rhizosphere soils than the other two riparian plant.In general,microbial biomass and biochemical activities in rhizosphere soils were depressed by butachlor addition,despite the riparian plant types.However,rhizospheric soil microbial ecophysiological responses to butachlor addition significantly （P 0.05） differed between riparian plant species.Compared to Z.aquatica and P.australis,A.calamus showed significantly larger microbial number,higher enzyme activities and soil respiration rates in the rhizosphere soils.The results indicated that A.calamus have a better alleviative effect on inhibition of microbial growth due to butachlor addition and can be used as a suitable riparian plant for detoxifying and remediating butachlor contamination from agricultural nonpoint pollution.
文摘To have a preliminary insight into biosafety of genetically transformed hybrid triploid poplars （Populus tomentosa × P bolleana）× P. tomentosa with the cowpea trypsin inhibitor （CpTD gene, two layers of rhizospheric soil （from 0 to 20cm deep and from 20 to 40cm deep, respectively） were collected for microorganism culture, counting assay and PCR analysis to assess the potential impact of transgenic poplars on non-target microorganism population and transgene dispersal. When the same soil layer of suspension stock solution was diluted at both 1：1000 and 1：10000 rates, there were no significant differences in bacterium colony numbers between the inoculation plates of both transgenic and non-transgenic poplars. The uniform results were revealed for both soil layer suspension solutions of identical poplars at both dilution rates except for non-transgenic poplars at 1：10000 dilution rates from the same type of soil. No significant variation in morphology of both Gram-positive and Gram-negative bacteria was observed under the microscope. The potential transgene dispersal from root exudates or fallen leaves to non-target microbes was repudiated by PCR analysis, in which no CpTI gene specific DNA band was amplified for 15 sites of transgenic rhizospheric soil samples. It can be concluded that transgenic poplar with the CpTI gene has no severe impact on rhizospheric microorganisms and is tentatively safe to surrounding soil micro-ecosystem.
文摘<p align="justify"> <span style="font-family:Verdana;">Soil salinization is one of the major causes of land degradation. In Senegal, this phenomenon continues to grow, making soils unsuitable for agriculture. To rehabilitate salty lands, one of the recommended strategies is the use of salt-tolerant plants. Among them, plants of </span><i><i><span style="font-family:Verdana;">Casuarinaceae</span></i></i><span style="font-family:Verdana;"> family form a relationship with symbiotic microorganisms such as arbuscular mycorrhizal fungi and nitrogen fixing bacteria. It has been shown that symbiotic microorganisms play an important role in the establishment of tolerant plants in saline conditions (Djighaly </span><i><i><span style="font-family:Verdana;">et al</span></i></i><span style="font-family:Verdana;">., 2018). They improve plant performance and reduce transplant shock under salt stress conditions (Diagne </span><i><i><span style="font-family:Verdana;">et al</span></i></i><span style="font-family:Verdana;">., 2014). These microorganisms can be used as biofertilizers. However, inocula containing symbiotic microorganisms are either too expensive or unavailable in many developing countries. The aim of this study is to test alternatively affordable and low-tech solutions to promote symbiotic interactions such as Casuarina crushed nodule, Casuarina rhizosphere soil and Casuarina leaves compost that may contain symbiotic microorganisms and also nutrients such as N and phosphorus. Two species of Casuarina (</span><i><i><span style="font-family:Verdana;">Casuarina equisetifolia</span></i></i><span style="font-family:Verdana;"> L. and </span><i><i><span style="font-family:Verdana;">Casuarina obesa</span></i></i><span style="font-family:Verdana;"> Miq.) were grown in the greenhouse on sterile soil to which an amendment was added (Casuarina crushed nodules, Casuarina Rhizospheric soil or Casuarina leaves compost). Plants were subjected to saline stress. After four months of cultivation, they were harvested and morphological a
文摘The contamination of arsenic (As) and other heavy metal (HMs) in soil causes serious health hazard to the ecosystem. In this work, the contamination of As and other heavy metals (i.e. Ti, V, Cr, Mn, Fe, Ni, Cu, Zn and Pb) in rhizospheric soil of 14 plants of the severely As contaminated area of Central India is described. Among them, high content of As in the rhizospheric soils was observed, ranging from 0.22 to 4.60 g/kg with mean value of 1.6 ± 0.7 g/kg. The concentration variation, enrichment indices and toxicities of the metals in the soil are described.
基金Dr. Dolikajytoti SHARMA from Gauhati University, India for the technical supportNanda Nath Saikia College, India for supporting this work。
文摘Biosurfactants are biomolecules produced by microorganisms, low in toxicity, biodegradable, and relatively easy to synthesize using renewable waste substrates. Biosurfactants are of great importance with a wide and versatile range of applications, including the bioremediation of contaminated sites. Plants may accumulate soil potentially toxic elements(PTEs), and the accumulation efficacy may be further enhanced by the biosurfactants produced by rhizospheric microorganisms. Occasionally, the growth of bacteria slows down in adverse conditions, such as highly contaminated soils with PTEs. In this context,the plant's phytoextraction capacity could be improved by the addition of metal-tolerant bacteria that produce biosurfactants. Several sources, categories,and bioavailability of PTEs in soil are reported in this article, with the focus on the cost-effective and sustainable soil remediation technologies, where biosurfactants are used as a remediation method. How rhizobacterial biosurfactants can improve PTE recovery capabilities of plants is discussed, and the molecular mechanisms in bacterial genomes that support the production of important biosurfactants are listed. The status and cost of commercial biosurfactant production in the international market are also presented.
基金support from the 863 National High-Technology Program of China(819-07-10).
文摘Oyster shell soil conditioner had significant influence on soil and rhizospheric microorganisms in their biomass,respiratory intensity and nutritional requirement. It could stimulate growth of soil and rhizospheric microorganisms, especially nitrogen-fixers, and intensify soil respiration in proportion to the dose and fertilizing time of the conditioner, leading to the increase in the number of nitrogen fixing bacteria and the decrease in the number of bacteria with special nutrition demands.
基金Supported by Innovation Incentive Project of Qiqihar Science and Technology Bureau (CNYGG-2021029)Special Program of "Agricultural Science and Technology Innovation Leapfrogging Project" of Heilongjiang Academy of Agricultural Sciences "Green and Efficient Prevention and Control Technology of Main Insect Pests in Facility Vegetables"(HNK2019CX10-18)。
文摘In order to promote the development and application of environmental-friendly,efficient and safe beneficial Bacillus sp.preparations,the paper summarizes and systematically elaborates the colonization of Bacillus sp.in host plants and the mechanism of synergistic effect on disease prevention of host plants,further reviews the application of rhizospheric Bacillus sp.in promoting the growth of agricultural and forestry crops and controlling plant diseases,and prospects the scientific issues and application of plant rhizospheric Bacillus sp.in the future.
文摘Studies on mechanisms and efficiencies of wastewater treatment with constructed wetland,mainly from developed countries,conducted mainly in the past 2 decades are reviewed.The mechanisms of wastewater treatment by wetlands are extremely complicated,including a series of physical,chemical,and bio chemical processes,such as special and non special adsorption,exchange,sedimentation,assimilation,decomposition,volatilization,and so on.There are lots of components,e.g.plants,soils,and microorganisms,in wetlands making contributions to water quality improvement.Of all plants in constructed wetlands, Phragmites communis is used most widely and frequently.But wetlands covered by this single species are inferior to those covered by many species including it and other plants with reference to removal efficiency of nutrients and pollutants.In order to consummate theories about constructed wetlands for wastewater treatment,and to further improve removal efficiencies of pollutants and wetland ecosystem health,the following research fields are suggested to consolidate or further conduct in the future:① deeper and more systemic research on mechanisms of wastewater purification by wetlands;② studies on sustainable development of constructed wetland;③ experimentation on the suitability of local and indigenous wetland macrophytes for removal of nutrients and heavy metals from different types of wastewater;④ exploration for better constructing,maintaining,and using measures to maximize the wastewater treatment efficiency;⑤ controlling disease vectors and animal pests,and preventing them from jeopardizing human health and lives;and ⑥ ascertaining reasons producing noxious and odorous gases and then trying to control them effectively.
