[Objective]To study endopeptidases in Spirodela polyrrhiza half-fronds during senescence and their characters. [Method]Changes in endopeptidase isoenzymes of the Spirodela polyrrhiza half-fronds during senescence were...[Objective]To study endopeptidases in Spirodela polyrrhiza half-fronds during senescence and their characters. [Method]Changes in endopeptidase isoenzymes of the Spirodela polyrrhiza half-fronds during senescence were detected by gelatin-SDS-PAGE electrophoresis,and their types were analyzed with protease inhibitors. [Result]Six endopeptidases were detected in the Spirodela polyrrhiza half-fronds during senescence. Among them,HEP1,HEP2,HEP4 and HEP6 （high molecular-weight endoprotease） were senescence-related endopeptidases. [Conclusion]The metalloendopeptidase plays significant roles at the early stage of senescence,and the cysteine endopeptidase are the most abundant at the late stage of senescence.展开更多
Plants are essential components of all ecosystems and play a critical role in environmental fate of nanoparticles. However, the toxicological impacts of nanoparticles on plants are not well documented. Titanium dioxid...Plants are essential components of all ecosystems and play a critical role in environmental fate of nanoparticles. However, the toxicological impacts of nanoparticles on plants are not well documented. Titanium dioxide nanoparticles（TiO2-NPs） are produced worldwide in large quantities for a wide range of purposes. In the present study, the uptake of TiO2-NPs by the aquatic plant Spirodela polyrrhiza and the consequent effects on the plant were evaluated.Initially, structural and morphological characteristics of the used TiO2-NPs were determined using XRD, SEM, TEM and BET techniques. As a result, an anatase structure with the average crystalline size of 8 nm was confirmed for the synthesized TiO2-NPs. Subsequently, entrance of TiO2-NPSto plant roots was verified by fluorescence microscopic images. Activity of a number of antioxidant enzymes, as well as, changes in growth parameters and photosynthetic pigment contents as physiological indices were assessed to investigate the effects of TiO2-NPs on S. polyrrhiza. The increasing concentration of TiO2-NPs led to the significant decrease in all of the growth parameters and changes in antioxidant enzyme activities. The activity of superoxide dismutase enhanced significantly by the increasing concentration of TiO2-NPs. Enhancement of superoxide dismutase activity could be explained as promoting antioxidant system to scavenging the reactive oxygen species. In contrast, the activity of peroxidase was notably decreased in the treated plants. Reduced peroxidase activity could be attributed to either direct effect of these particles on the molecular structure of the enzyme or plant defense system damage due to reactive oxygen species.展开更多
This study investigates arsenic （As） accumulation and tolerance of duckweed Spirodela polyrhiza L. and its potential for As phytofiltration. S. polyrhiza was able to survive in high concentration of As（V） solution...This study investigates arsenic （As） accumulation and tolerance of duckweed Spirodela polyrhiza L. and its potential for As phytofiltration. S. polyrhiza was able to survive in high concentration of As（V） solution. The EC 50 values （± SE） based on the external As（V） were （181.66 ± 20.12） μmol/L. It accumulated （999 ± 95） mg As/kg dw when exposed in 320 μmol/L As（V） solution for one week, and was able to take up appropriately 400 mg As/kg dw in tissues without a significant biomass loss. The EC 50 values （the effective concentration of As（V） in the nutrient solution that caused a 50% inhibition on biomass production） was （866 ± 68） mg/kg dw for the tissues, indicating that S. polyrhiza had a high capability of As accumulation and tolerance. The uptake kinetic parameters V max was （55.33 ± 2.24） nmol/（g dw·min） and K m was （0.144 ± 0.011） mmol/L. Within 72 hr, S. polyrhiza decreased As concentration in the solution from 190 to 113 ng/mL with a removal rate of 41%. The study suggested that this floating aquatic plant has some potential for As phytofiltration in contaminated water bodies or paddy soils.展开更多
Removal experiments of phenol, aniline, 2,4-dichlorophenol, nonylphenol and bisphenol A （BPA） using Spirodela polyrrhiza- bacterial associations revealed that all compounds but BPA underwent accelerated removal. The...Removal experiments of phenol, aniline, 2,4-dichlorophenol, nonylphenol and bisphenol A （BPA） using Spirodela polyrrhiza- bacterial associations revealed that all compounds but BPA underwent accelerated removal. The mechanisms differed depending on the substrates. It was found that S. polyrrhiza has a great ability to release phenolic compound-rich root exudates, and the exudates seem to stimulate bacterial degradation of a variety of aromatic compounds.展开更多
We investigated the biodegradation of 2-nitrophenol （2-NP）, 4-nitrophenol （4-NP）, and 2,4-dinitrophenol （2,4-DNP） in the rhizosphere of Spirodela polyrrhiza plants by conducting degradation experiments with thre...We investigated the biodegradation of 2-nitrophenol （2-NP）, 4-nitrophenol （4-NP）, and 2,4-dinitrophenol （2,4-DNP） in the rhizosphere of Spirodela polyrrhiza plants by conducting degradation experiments with three river water samples supplemented with each nitrophenol （NP）. We then isolated NP-degrading bacteria both from the S. polyrrhiza roots and from the river water. In the river water samples, removal of the three NP was accelerated in the presence of S. polyrrhiza plants. The three NPs persisted in an autoclaved solution with sterile plants suggests that NP removal was accelerated largely by bacterial NP biodegradation rather than by adsorption and uptake by the plants. We isolated 8 strains of NP-degrading bacteria： 6 strains from the S. polyrrhiza roots and 2 strains from river water without the plants. The 2-NP- and 2,4-DNP-degrading bacteria were isolated only from the S. polyrrhiza roots. The 4-NP- degrading bacteria different from those isolated from the river water samples were also found on S. polyrrhiza roots. The 2-NP- and 4-NP-degrading strains isolated from the roots utilized the corresponding NP （0.5 mmol/L） as the sole carbon and energy source. The 2,4-DNP-degrading strains isolated from the roots showed substantial 2,4-DNP-degrading activity, but the presence of other carbon and energy sources was required for their growth. The isolated NP-degrading bacteria from the roots must have contributed to the accelerated degradation of the three NPs in the rhizosphere of S. polyrrhiza. Our results suggested that rhizoremediation with S. polyrrhiza may be effective for NP-contaminated surface water.展开更多
Here, we compared the intrinsic characteristics of 3-day-(newly germinated;<span><span style="font-family:Verdana;">“young”) and 8-week-old (“mature”) fronds of the aquatic plant </span>...Here, we compared the intrinsic characteristics of 3-day-(newly germinated;<span><span style="font-family:Verdana;">“young”) and 8-week-old (“mature”) fronds of the aquatic plant </span><i><span style="font-family:Verdana;">Spirodela</span></i><span style="font-family:Verdana;"> <i>polyrhiza</i></span> </span><span style="font-family:Verdana;">and their sensitivity to paraquat, a toxic herbicide. Endpoints measured were frond area and fresh weight, root length, chlorophyll</span><i><span style="font-family:Verdana;"> a</span></i><span style="font-family:Verdana;"> and</span><i><span style="font-family:Verdana;"> b </span></i><span style="font-family:Verdana;">contents, and chlorophyll</span><i><span style="font-family:Verdana;"> a</span></i><span style="font-family:Verdana;"> fluorescence. Significant differences were detected in the intrinsic physiological traits between young and mature fronds. Young fronds showed higher root length, chlorophyll contents, maximum quantum yield (</span><i><span style="font-family:Verdana;">F</span><sub><span style="font-family:Verdana;">v</span></sub></i><span style="font-family:Verdana;">/</span><i><span style="font-family:Verdana;">F</span><sub><span style="font-family:Verdana;">m</span></sub></i><span style="font-family:Verdana;">), maximal relative electron transport rate (rETR</span><sub><span style="font-family:Verdana;">max</span></sub><span style="font-family:Verdana;">) and saturating photon flux density (PFD), whereas mature fronds exhibited greater frond area and fresh weight. After a 72 h exposure to paraquat, root length and rETR</span><sub><span style="font-family:Verdana;">max</span></sub><span style="font-family:Verdana;"> were identified as the most sensitive endpoints of paraquat toxicity for both frond types, with EC</span><sub><span style="font-family:Verdana;">50</span></sub><span style="font-family:Verdana;"> values of 0.66 and 0.76 μg<span style="font-size:6.5pt;font-family:"background:yellow;">·</span>L</span><sup><span style="font-family:Verdana;">-1</span></sup><span style="font-family:Verdana;"> for young fronds, respectively, and 5.53 and 2.28 μg<span style="font-size:6.5pt;font-family:"background:yellow;">·</span>L</span><sup><span style="font-family:Verdana;">-1</span></sup><span style="font-family:Verdana;"> for mature fronds, respectively. Young fronds of </span><i><span style="font-family:Verdana;">S.</span></i><span style="font-family:Verdana;"> <i>polyrhiza</i></span><span style="font-family:Verdana;"> showed significantly higher sensitivity to paraquat than mature fronds. A survey of other studies on paraquat toxicity to </span><i><span style="font-family:Verdana;">Lemna</span></i><span style="font-family:Verdana;"> species revealed that EC</span><sub><span style="font-family:Verdana;">50</span></sub><span style="font-family:Verdana;"> values of paraquat-induced inhibition of root regrowth and rETR</span><sub><span style="font-family:Verdana;">max</span></sub><span style="font-family:Verdana;"> in both stages were the lowest, indicating that these two endpoints were the most sensitive to paraquat. In addition, EC</span><sub><span style="font-family:Verdana;">50</span></sub><span style="font-family:Verdana;"> values of both endpoints of mature fronds of </span><i><span style="font-family:Verdana;">S.</span></i><span style="font-family:Verdana;"> <i>polyrhiza </i></span><span style="font-family:Verdana;">appear to be similar to the current allowable concentrations in drinking water set by the World Health Organization (WHO), indicating that these values may have application for the assessment of toxicity risk of paraquat in aquatic ecosystems.</span>展开更多
基金Supported by New Century Excellent Talents Project of the Ministry of Education (2006)Talents Introduction Fund of Tianjin University of Science and Technology (20060432 and 20080216)~~
文摘[Objective]To study endopeptidases in Spirodela polyrrhiza half-fronds during senescence and their characters. [Method]Changes in endopeptidase isoenzymes of the Spirodela polyrrhiza half-fronds during senescence were detected by gelatin-SDS-PAGE electrophoresis,and their types were analyzed with protease inhibitors. [Result]Six endopeptidases were detected in the Spirodela polyrrhiza half-fronds during senescence. Among them,HEP1,HEP2,HEP4 and HEP6 （high molecular-weight endoprotease） were senescence-related endopeptidases. [Conclusion]The metalloendopeptidase plays significant roles at the early stage of senescence,and the cysteine endopeptidase are the most abundant at the late stage of senescence.
文摘Plants are essential components of all ecosystems and play a critical role in environmental fate of nanoparticles. However, the toxicological impacts of nanoparticles on plants are not well documented. Titanium dioxide nanoparticles（TiO2-NPs） are produced worldwide in large quantities for a wide range of purposes. In the present study, the uptake of TiO2-NPs by the aquatic plant Spirodela polyrrhiza and the consequent effects on the plant were evaluated.Initially, structural and morphological characteristics of the used TiO2-NPs were determined using XRD, SEM, TEM and BET techniques. As a result, an anatase structure with the average crystalline size of 8 nm was confirmed for the synthesized TiO2-NPs. Subsequently, entrance of TiO2-NPSto plant roots was verified by fluorescence microscopic images. Activity of a number of antioxidant enzymes, as well as, changes in growth parameters and photosynthetic pigment contents as physiological indices were assessed to investigate the effects of TiO2-NPs on S. polyrrhiza. The increasing concentration of TiO2-NPs led to the significant decrease in all of the growth parameters and changes in antioxidant enzyme activities. The activity of superoxide dismutase enhanced significantly by the increasing concentration of TiO2-NPs. Enhancement of superoxide dismutase activity could be explained as promoting antioxidant system to scavenging the reactive oxygen species. In contrast, the activity of peroxidase was notably decreased in the treated plants. Reduced peroxidase activity could be attributed to either direct effect of these particles on the molecular structure of the enzyme or plant defense system damage due to reactive oxygen species.
基金supported by the Chinese Academy of Sciences(No.KZCX1-YW-06-03)the National Natural Science Foundation of China(No.20720102042)
文摘This study investigates arsenic （As） accumulation and tolerance of duckweed Spirodela polyrhiza L. and its potential for As phytofiltration. S. polyrhiza was able to survive in high concentration of As（V） solution. The EC 50 values （± SE） based on the external As（V） were （181.66 ± 20.12） μmol/L. It accumulated （999 ± 95） mg As/kg dw when exposed in 320 μmol/L As（V） solution for one week, and was able to take up appropriately 400 mg As/kg dw in tissues without a significant biomass loss. The EC 50 values （the effective concentration of As（V） in the nutrient solution that caused a 50% inhibition on biomass production） was （866 ± 68） mg/kg dw for the tissues, indicating that S. polyrhiza had a high capability of As accumulation and tolerance. The uptake kinetic parameters V max was （55.33 ± 2.24） nmol/（g dw·min） and K m was （0.144 ± 0.011） mmol/L. Within 72 hr, S. polyrhiza decreased As concentration in the solution from 190 to 113 ng/mL with a removal rate of 41%. The study suggested that this floating aquatic plant has some potential for As phytofiltration in contaminated water bodies or paddy soils.
基金supported in part by a Grant-in-Aid for Encouragement of Young Scientists A (No.21681010) from the Ministry of Education,Culture,Sports,Science and Technology of Japansupported in part by a Grant-in-Aid for Encouragement of Young Scientists B (No.19710060) from the Ministry of Education,Culture,Sports,Science and Technology of Japan
文摘Removal experiments of phenol, aniline, 2,4-dichlorophenol, nonylphenol and bisphenol A （BPA） using Spirodela polyrrhiza- bacterial associations revealed that all compounds but BPA underwent accelerated removal. The mechanisms differed depending on the substrates. It was found that S. polyrrhiza has a great ability to release phenolic compound-rich root exudates, and the exudates seem to stimulate bacterial degradation of a variety of aromatic compounds.
基金supported by Japan Science and Technology Agency (JST)the National Natural Science Foundation of China (NSFC) Project as the Japan-China Joint Research Program on Science and Technology (S&T) for Environmental Conservation and Construction of a Society with Less Environmental Burden with the research theme of Development of remediation technique for water environmental pollution using microorganisms and aquatic plants with purification ability-enhanced rhizosphere
文摘We investigated the biodegradation of 2-nitrophenol （2-NP）, 4-nitrophenol （4-NP）, and 2,4-dinitrophenol （2,4-DNP） in the rhizosphere of Spirodela polyrrhiza plants by conducting degradation experiments with three river water samples supplemented with each nitrophenol （NP）. We then isolated NP-degrading bacteria both from the S. polyrrhiza roots and from the river water. In the river water samples, removal of the three NP was accelerated in the presence of S. polyrrhiza plants. The three NPs persisted in an autoclaved solution with sterile plants suggests that NP removal was accelerated largely by bacterial NP biodegradation rather than by adsorption and uptake by the plants. We isolated 8 strains of NP-degrading bacteria： 6 strains from the S. polyrrhiza roots and 2 strains from river water without the plants. The 2-NP- and 2,4-DNP-degrading bacteria were isolated only from the S. polyrrhiza roots. The 4-NP- degrading bacteria different from those isolated from the river water samples were also found on S. polyrrhiza roots. The 2-NP- and 4-NP-degrading strains isolated from the roots utilized the corresponding NP （0.5 mmol/L） as the sole carbon and energy source. The 2,4-DNP-degrading strains isolated from the roots showed substantial 2,4-DNP-degrading activity, but the presence of other carbon and energy sources was required for their growth. The isolated NP-degrading bacteria from the roots must have contributed to the accelerated degradation of the three NPs in the rhizosphere of S. polyrrhiza. Our results suggested that rhizoremediation with S. polyrrhiza may be effective for NP-contaminated surface water.
文摘Here, we compared the intrinsic characteristics of 3-day-(newly germinated;<span><span style="font-family:Verdana;">“young”) and 8-week-old (“mature”) fronds of the aquatic plant </span><i><span style="font-family:Verdana;">Spirodela</span></i><span style="font-family:Verdana;"> <i>polyrhiza</i></span> </span><span style="font-family:Verdana;">and their sensitivity to paraquat, a toxic herbicide. Endpoints measured were frond area and fresh weight, root length, chlorophyll</span><i><span style="font-family:Verdana;"> a</span></i><span style="font-family:Verdana;"> and</span><i><span style="font-family:Verdana;"> b </span></i><span style="font-family:Verdana;">contents, and chlorophyll</span><i><span style="font-family:Verdana;"> a</span></i><span style="font-family:Verdana;"> fluorescence. Significant differences were detected in the intrinsic physiological traits between young and mature fronds. Young fronds showed higher root length, chlorophyll contents, maximum quantum yield (</span><i><span style="font-family:Verdana;">F</span><sub><span style="font-family:Verdana;">v</span></sub></i><span style="font-family:Verdana;">/</span><i><span style="font-family:Verdana;">F</span><sub><span style="font-family:Verdana;">m</span></sub></i><span style="font-family:Verdana;">), maximal relative electron transport rate (rETR</span><sub><span style="font-family:Verdana;">max</span></sub><span style="font-family:Verdana;">) and saturating photon flux density (PFD), whereas mature fronds exhibited greater frond area and fresh weight. After a 72 h exposure to paraquat, root length and rETR</span><sub><span style="font-family:Verdana;">max</span></sub><span style="font-family:Verdana;"> were identified as the most sensitive endpoints of paraquat toxicity for both frond types, with EC</span><sub><span style="font-family:Verdana;">50</span></sub><span style="font-family:Verdana;"> values of 0.66 and 0.76 μg<span style="font-size:6.5pt;font-family:"background:yellow;">·</span>L</span><sup><span style="font-family:Verdana;">-1</span></sup><span style="font-family:Verdana;"> for young fronds, respectively, and 5.53 and 2.28 μg<span style="font-size:6.5pt;font-family:"background:yellow;">·</span>L</span><sup><span style="font-family:Verdana;">-1</span></sup><span style="font-family:Verdana;"> for mature fronds, respectively. Young fronds of </span><i><span style="font-family:Verdana;">S.</span></i><span style="font-family:Verdana;"> <i>polyrhiza</i></span><span style="font-family:Verdana;"> showed significantly higher sensitivity to paraquat than mature fronds. A survey of other studies on paraquat toxicity to </span><i><span style="font-family:Verdana;">Lemna</span></i><span style="font-family:Verdana;"> species revealed that EC</span><sub><span style="font-family:Verdana;">50</span></sub><span style="font-family:Verdana;"> values of paraquat-induced inhibition of root regrowth and rETR</span><sub><span style="font-family:Verdana;">max</span></sub><span style="font-family:Verdana;"> in both stages were the lowest, indicating that these two endpoints were the most sensitive to paraquat. In addition, EC</span><sub><span style="font-family:Verdana;">50</span></sub><span style="font-family:Verdana;"> values of both endpoints of mature fronds of </span><i><span style="font-family:Verdana;">S.</span></i><span style="font-family:Verdana;"> <i>polyrhiza </i></span><span style="font-family:Verdana;">appear to be similar to the current allowable concentrations in drinking water set by the World Health Organization (WHO), indicating that these values may have application for the assessment of toxicity risk of paraquat in aquatic ecosystems.</span>
