Publications by authors named "Tingqiang Li"

78 Publications

Exposure of cerium oxide nanoparticles to the hyperaccumulator Sedum alfredii decreases the uptake of cadmium via the apoplastic pathway.

J Hazard Mater 2021 Apr 26;417:125955. Epub 2021 Apr 26.

Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China; National Demonstration Center for Experimental Environment and Resources Education, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Hangzhou 310058, China. Electronic address:

Cadmium (Cd) is harmful to the environment and threatens human health. With the increasing use of cerium oxide nanoparticles (CeONPs) in extensive industries, investigating the combination of CeONPs and plants has attracted research interests for phytoremediation. Here, we explored the effects of CeONPs on Cd uptake, transport and the consequent Cd accumulation in Sedum alfredii. Exposure of 50 or 500 mg L CeONPs alone had no apparent damaging effects on plant growth. However, upon Cd condition, the consistent CeONPs decreased Cd concentrations in the roots and shoots by up to 37%. Furthermore, the application of a metabolic inhibitor revealed that CeONPs mainly decreased the Cd uptake in roots by the apoplastic pathway. Simultaneously, CeONPs accelerated the development of Casparian strips (CSs) and suberin, which was further proven by the elevated expression levels of genes associated with their formation, SaCASP, SaGPAT5, SaKCS20 and SaCYP86A1. Compared to CeONPs added alone, the concurrent Cd decreased the Ce contents in the roots and altered its translocation from root to shoot. Taken together, both CeONPs and Cd influence the interactional uptake of both chemicals in roots of S. alfredii mainly via the apoplastic pathway which is primarily regulated by the development of CSs and suberin.
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http://dx.doi.org/10.1016/j.jhazmat.2021.125955DOI Listing
April 2021

Loss of organic carbon in suburban soil upon urbanization of Chengdu megacity, China.

Sci Total Environ 2021 Sep 21;785:147209. Epub 2021 Apr 21.

College of Resources, Sichuan Agricultural University, Chengdu 611130, China. Electronic address:

Urbanization is progressing rapidly. It can affect soils ecosystem services directly through land management and indirectly through changes in the socioeconomic environment, which eventually leads to an increase in emissions of greenhouse gases. Soil carbon (C) sequestration plays an important role in offsetting the anthropogenic C emissions. However, there is limited knowledge of how urbanization affects the soil C especially that in suburban. In this study, we studied changes in easily oxidizable organic C (EOC) and total organic C (TOC) of suburban soils (0-100 cm) in the rapid urbanising megacity Chengdu, China. The EOC stock and TOC stock decreased from the outer-suburb to the inner-suburb by 17.8-28.2% and 5.4-13.5%, respectively; particularly, the inner-suburb EOC decreased by 31.4-38.6% during the past 10 years. The quotient of EOC/TOC in the soil profile, reflecting the stability of soil C, declined from the outer-suburb (0.78) to the inner-suburb (0.20). Factors that influenced the EOC and TOC included the changes in economics (economic density, industrialization), farmland (cultivated area, farmland structure), urbanization (city size, population growth) and traffic flow. Among which, economic density growth was the primarily driver of the loss in TOC, explaining 31.6% of the variation in soil surface TOC and 16.0% of the variation in subsoil TOC; changes in farmland and urban expansion were the main factors contributing to the loss of subsoil EOC, with 40.4% explanatory ability. In addition, traffic flow also has contribution to the subsoil EOC loss. We concluded that the increasing soil C loss with decreasing distance from the city centre has a continuous contribution to C emission, and the C loss will persist until the suburbs are fully urbanized. The large losses of EOC and TOC caused by urbanization, and their contribution to global warming, necessitate their consideration in future appraisals of climate change and urban planning projects.
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http://dx.doi.org/10.1016/j.scitotenv.2021.147209DOI Listing
September 2021

The influence of elevated CO on bacterial community structure and its co-occurrence network in soils polluted with CrO nanoparticles.

Sci Total Environ 2021 Jul 13;779:146430. Epub 2021 Mar 13.

Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Hangzhou 310058, China; National Demonstration Center for Experimental Environment and Resources Education, Zhejiang University, Hangzhou 310058, China. Electronic address:

Elevated CO (eCO) and nanoparticles release are considered among the most noteworthy global concerns as they may impose negative effects on human health and ecosystem functioning. A mechanistic understanding of their combined impacts on soil microbiota is essential due to the profound eCO effect on soil biogeochemical processes. In this study, the impacts of CrO nanoparticles (nano-CrO) on the activity, structure and co-occurrence networks of bacterial communities under ambient and eCO were compared between a clay loam and a sandy loam soil. We showed that eCO substantially mitigated nano-CrO toxicity, with microbial biomass, enzyme activity and bacterial alpha-diversity in clay loam soil were much higher than those in sandy loam soil. Nano-CrO addition caused an increase in alpha-diversity except for clay loam soil samples under eCO. 16S rRNA gene profiling data found eCO remarkably reduced community divergences induced by nano-CrO more efficiently in clay loam soil (P < 0.05). Network analyses revealed more complex co-occurrence network architectures in clay loam soil than in sandy loam soil, however, nano-CrO decreased but eCO increased modularity and network complexity. Rising CO favoured the growth of oligotrophic (Acidobacteriaceae, Bryobacteraceae) rather than the copiotrophic bacteria (Sphingomonadaceae, Caulobacteraceae, Bacteroidaceae), which may contribute to community recovery and increase available carbon utilization efficiency. Our results suggested that the degree to which eCO mitigates nano-CrO toxicity is soil dependent, which could be related to the variation in clay and organic matter content, resilience of the resistant bacterial taxa, and microbial network complexity in distinct soils.
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http://dx.doi.org/10.1016/j.scitotenv.2021.146430DOI Listing
July 2021

Silicon alleviates salt stress-induced potassium deficiency by promoting potassium uptake and translocation in rice (Oryza sativa L.).

J Plant Physiol 2021 Mar-Apr;258-259:153379. Epub 2021 Feb 10.

Ministry of Education Key Laboratory of Environment Remediation and Ecological Health, College of Environmental & Resource Sciences, Zhejiang University, Hangzhou, 310058, China. Electronic address:

Under salt stress, plants suffer from potassium (K) deficiency caused by excess salts in growth substrate. Silicon (Si) can promote K status in many plant species under salt stress, however, the underlying mechanisms remain unclear. In this study, we assessed the effects of Si on K homeostasis in rice under salt stress and investigated the mechanisms behind using two low-Si rice mutants (lsi1 and lsi2) and their wild types (WTs). After five days' treatment with Si, plant growth was improved and salt stress-induced K deficiency was alleviated in WTs but not in mutants. Simultaneously, Si significantly enhanced K accumulation content, K uptake index and shoot K distribution rate in WTs but not in mutants. Besides, Si enhanced K concentration in xylem sap in WTs but not in mutants. Scanning ion-selected electrode technique (SIET) analysis showed net K influx rate was raised by Si addition under salt stress in WTs but not in mutants. Moreover, Si up-regulated the expression of genes responsible for K uptake (OsAKT1 and OsHAK1) and xylem loading (OsSKOR) in WTs but not in mutants. Overall, our results strongly indicate that Si can improve K uptake and translocation by up-regulating the expression of relevant genes, thereby promoting K status and alleviating salt stress in rice.
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http://dx.doi.org/10.1016/j.jplph.2021.153379DOI Listing
June 2021

Abscisic acid-mediated modifications in water transport continuum are involved in cadmium hyperaccumulation in Sedum alfredii.

Chemosphere 2021 Apr 16;268:129339. Epub 2020 Dec 16.

College of Resources, Sichuan Agricultural University, Chengdu, 611130, China. Electronic address:

Abscisic acid (ABA) play a crucial role in plant acclimation to heavy-metals stresses. Nevertheless, the effects of ABA on long-distance transport and its consequences for cadmium (Cd) accumulation are insufficiently understood. Here, we investigated the effects of ABA on the development of the whole-plant water transport pathway and implications for Cd uptake and transport to the shoot of Sedum alfredii. Exposure to Cd stimulated the production of endogenous ABA levels in the non-hyperaccumulating ecotype (NHE), but not in the hyperaccumulating ecotype (HE). Increased ABA levels in NHE significantly reduced aquaporin expressions in roots, the number of xylem vessel in stem, dimensions and densities of stomata in leaves, but induced leaf osmotic adjustment. Furthermore, the ABA-driven modifications in NHE plants showed typically higher sensitivity to ABA content in leaves compared to HE, illustrating ecotype-specific responses to ABA level. In NHE, the ABA-mediated modifications primarily affected the xylem transport of Cd ions and, at the cost of considerable water delivery limitations, significantly reduced delivery of Cd ions to shoots. In contrast, maintenance of low ABA levels in HE failed to t limit transpiration rates and maximized Cd accumulation in shoots. Our results demonstrated that ABA regulates Cd hyperaccumulation of S. alfredii through specific modifications in the water transport continuum.
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http://dx.doi.org/10.1016/j.chemosphere.2020.129339DOI Listing
April 2021

Ethylene-mediated apoplastic barriers development involved in cadmium accumulation in root of hyperaccumulator Sedum alfredii.

J Hazard Mater 2021 02 19;403:123729. Epub 2020 Aug 19.

Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmentaland Resource Sciences, Zhejiang University, Hangzhou, 310058, China; Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Hangzhou, 310058, China; National Demonstration Center for Experimental Environment and Resources Education, Zhejiang University, Hangzhou, 310058, China. Electronic address:

Ethylene is an important phytohormone for plant adaptation to heavy metal stress. However, the effects of ethylene on radial apoplastic transport of Cd remain elusive. This study investigated the role of ethylene on apoplastic barriers development and consequences for Cd uptake in Sedum alfredii. In response to Cd, endogenous ethylene production in hyperaccumulating ecotype (HE) roots was decreased due to the down-regulated expressions of ethylene biosynthesis genes, while the opposite result was observed in non-hyperaccumulating ecotype (NHE). Interestingly, the ethylene emission in HE was always higher than that in NHE, regardless of Cd concentrations. Results of exogenous application of ethylene biosynthesis precursor/inhibitor indicate that ethylene with high level would delay the formation of apoplastic barriers in HE through restraining phenylalanine ammonia lyase activity and gene expressions related to lignin/suberin biosynthesis. Simultaneously, correlation analyses suggest that Cd-induced apoplastic barriers formation may be also regulated by ethylene signaling. By using an apoplastic bypass tracer and scanning ion-selected electrode, we observed that the delayed deposition of apoplastic barriers significantly promoted Cd influx in roots. Taken together, high endogenous ethylene in HE postponed the formation of apoplastic barriers and thus promoted the Cd accumulation in the apoplast of roots.
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http://dx.doi.org/10.1016/j.jhazmat.2020.123729DOI Listing
February 2021

Root silicon deposition and its resultant reduction of sodium bypass flow is modulated by OsLsi1 and OsLsi2 in rice.

Plant Physiol Biochem 2021 Jan 17;158:219-227. Epub 2020 Nov 17.

Ministry of Education Key Laboratory of Environment Remediation and Ecological Health, College of Environmental & Resource Sciences, Zhejiang University, Hangzhou, 310058, China. Electronic address:

Silicon (Si) can alleviate salt stress by decreasing Na bypass flow in rice (Oryza sativa L.), however, the mechanisms underpinning remain veiled. In this study, we investigated the roles of OsLsi1 and OsLsi2 in Si-induced reduction of bypass flow and its resultant alleviation of salt stress by using lsi1 and lsi2 mutants (defective in OsLsi1 and OsLsi2, respectively) and their wild types (WTs). Under salt stress, Si promoted plant growth and decreased root-to-shoot Na translocation in WTs, but not in mutants. Simultaneously, quantitative estimation and fluorescent visualization of trisodium-8-hydroxy-1,3,6-pyrenetrisulphonic (PTS, an apoplastic tracer) showed Si reduced bypass flow in WTs, but not in mutants. Energy-dispersive X-ray microanalysis (EDX) showed Si was deposited at root endodermis in WTs, but not in mutants. Moreover, results obtained from root split experiment using lsi1 WT showed down-regulated expression of Si transport genes (OsLsi1 and OsLsi2) in root accelerated Si deposition at root endodermis. In summary, our results reveal that Si deposition at root endodermis and its resultant reduction of Na bypass flow is modulated by OsLsi1 and OsLsi2 and regulated by the expression of OsLsi1 and OsLsi2, implying that root Si deposition could be an active and physiologically-regulated process in rice.
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http://dx.doi.org/10.1016/j.plaphy.2020.11.015DOI Listing
January 2021

A review on the thermal treatment of heavy metal hyperaccumulator: Fates of heavy metals and generation of products.

J Hazard Mater 2021 03 3;405:123832. Epub 2020 Sep 3.

School of Environmental Science and Engineering/ Tianjin Key Lab of Biomass Waste Utilization, Tianjin University, Tianjin 300072, China. Electronic address:

Phytoremediation is perceived as a promising technique for remediation of heavy metal (HM) contaminated soils, while the harvested HM-enriched hyperaccumulator biomass should be appropriately disposed. Recently, various thermal treatments of hyperaccumulator have drawn increasing attention. After thermal treatment, the hyperaccumulator was converted to bio-oil, bio-gas, biochar, or ash in accordance with the corresponding conditions, and the HMs were separated, immobilized, or trapped. The migration and transformation of HMs during the thermochemical conversion processes are critical for the safe disposal and further utilization of HM hyperaccumulator. This paper provides a systematic review on the migration and transformation of typical HMs (Cd, Ni, Mn, As, and Zn) in hyperaccumulator during various thermochemical conversion processes, and special emphasis is given to the production and application of targeted products (e.g. biochar, hydrochar, bio-oil, and syngas). Besides, future challenges and perspectives in the thermal treatment of hyperaccumulator are presented as well. The distribution and speciation of HMs were influenced by thermal technique type and reaction conditions, thereby affecting the utilization of the derived products. This review suggests that speciation and availability of HMs in hyperaccumulator are tunable by varying treatment techniques and reaction conditions. This information should be useful for the selective conversion of hyperaccumulator into green and valuable products.
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http://dx.doi.org/10.1016/j.jhazmat.2020.123832DOI Listing
March 2021

The effects and health risk assessment of cauliflower co-cropping with Sedum alfredii in cadmium contaminated vegetable field.

Environ Pollut 2021 Jan 23;268(Pt B):115869. Epub 2020 Oct 23.

MOE Key Laboratory of Environment Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, People's Republic of China. Electronic address:

Phytoremediation coupled with co-cropping is assumed to be good for safety utilization and remediation of heavy metal contaminated farmland, which can ensure farmers' income without increasing health risks for human. In this study, the effects on plant cadmium (Cd) accumulation and health risk of consuming the vegetable plant were compared between monoculture and co-cropping of cauliflower (Brassica oleracea) with two ecotypes of Sedum alfredii in a moderately (0.82 mg kg) Cd contaminated greenhouse vegetable field. The results showed that co-cropping with S. alfredii raised Cd concentration in edible part of cauliflower with slightly growth promotion. The health risk of consuming cauliflower to different groups of people have been evaluated by calculating Hazard Quotient (HQ) and all HQ value were less than 1.0, which indicated that eating co-cropped cauliflower would not cause health risks to adults and children. Besides, the Cd concentration of hyperaccumulating ecotype (HE) of S. alfredii was 27.3 mg kg in monoculture and it increased to 51.2 mg kg after co-cropping with cauliflower, suggesting that the co-cropping system promoted HE Cd absorption capacity. Therefore, the "Phytoextraction Coupled with Agro-safe-production" (PCA) model of cauliflower and HE can serve as an alternative sustainable strategy in the Cd moderate polluted greenhouse.
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http://dx.doi.org/10.1016/j.envpol.2020.115869DOI Listing
January 2021

Coordination between root cell wall thickening and pectin modification is involved in cadmium accumulation in Sedum alfredii.

Environ Pollut 2021 Jan 18;268(Pt A):115665. Epub 2020 Sep 18.

Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China; Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Hangzhou, 310058, China; National Demonstration Center for Experimental Environment and Resources Education, Zhejiang University, Hangzhou, 310058, China. Electronic address:

Root cell wall (RCW) modification is a widespread important defense strategy of plant to cope with trace metals. However, mechanisms underlying its remolding in cadmium (Cd) accumulation are still lacking in hyperaccumulators. In this study, changes of RCW structures and components between nonhyperaccumulating ecotype (NHE) and hyperaccumulating ecotype (HE) of Sedum alfredii were investigated simultaneously. Under 25 μM Cd treatment, RCW thickness of NHE is nearly 2 folds than that of HE and the thickened cell wall of NHE was enriched in low-methylated pectin, leading to more Cd trapped in roots tightly. In the opposite, large amounts of high-methylated pectin were assembled around RCW of HE with Cd supply, in this way, HE S. alfredii decreased its root fixation of Cd and enhanced Cd migration into xylem. TEM and AFM results further confirmed that thickened cell wall was caused by the increased amounts of cellulose and lignin while root tip lignification was resulted from variations of sinapyl (S) and guaiacyl (G) monomers. Overall, thickened cell wall and methylated pectin have synchronicity in spatial location of roots, and their coordination contributed to Cd accumulation in S. alfredii.
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http://dx.doi.org/10.1016/j.envpol.2020.115665DOI Listing
January 2021

A comparative study of root cadmium radial transport in seedlings of two wheat (Triticum aestivum L.) genotypes differing in grain cadmium accumulation.

Environ Pollut 2020 Nov 17;266(Pt 3):115235. Epub 2020 Jul 17.

Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China; National Demonstration Center for Experimental Environment and Resources Education, Zhejiang University, Hangzhou, 310058, China. Electronic address:

The radial transport of cadmium (Cd) is essential for Cd influx in roots. The role of radial transport pathway on the Cd translocation from root to shoot among wheat genotypes are still poorly understood. This study explored the role of apoplastic and symplastic pathway on root Cd uptake and root-to-shoot translocation in Zhenmai 10 (ZM10, high Cd in grains) and Aikang 58 (AK58, low Cd in grains). Under Cd treatment, the deposition of Casparian strips (CSs) and suberin lamellae (SL) initiated closer to the root apex in ZM10 than that in AK58, which resulted in the lower Cd concentration in apoplastic fluid of ZM10. Simultaneously, Cd-induced expression levels of genes related to Cd uptake in roots were significantly higher in AK58 by contrast with ZM10, contributing to the symplastic Cd accumulation in AK58 root. Moreover, the addition of metabolic inhibitor CCCP noticeably decreased the Cd accumulation in root of both genotypes. Intriguingly, compared to ZM10, greater amounts of Cd were sequestrated in the cell walls and vacuoles in roots of AK58, limiting the translocation of Cd from root to shoot. Furthermore, the elevated TaHMA2 expression in ZM10 indicates that ZM10 had a higher capacity of xylem loading Cd than AK58. All of these results herein suggest that the radial transport is significant for Cd accumulation in roots, but it cannot explain the difference in root-to-shoot translocation of Cd in wheat genotypes with contrast Cd accumulation in grains.
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http://dx.doi.org/10.1016/j.envpol.2020.115235DOI Listing
November 2020

Growth and Photosynthetic Inhibition of Cerium Oxide Nanoparticles on Soybean (Glycine max).

Bull Environ Contam Toxicol 2020 Jul 28;105(1):119-126. Epub 2020 May 28.

Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China.

Cerium oxide nanoparticles (CeO NPs) are widely used in industries and have caused environmental problems. However, the phytotoxicity induced by CeO NPs lacks detailed information on phytotoxicity. In this research, the effect of CeO NPs on soybean plants (Glycine max) was studied. Scanning electron microscopy with the energy dispersion spectroscopy was used to characterize the NPs form in soybean. The growth of the root was increased, whereas the growth of shoot was inhibited. Besides, Chlorophyll Fluorescence Imager (CF Imager) showed that chlorophyll synthesis was inhibited: the maximum quantum yield of Photosystem II complex (PSII) (Fv/Fm) and photochemical quenching (qP) decreased. Moreover, transmission electron microscopy revealed that the chloroplast thylakoid structure was changed, and thus reduced the energy conversion in the Calvin cycle from C5 to C3. Our work suggests that CeO NPs will cause growth changes as well as irreversible damage to soybean plants. Our findings will provide evidence for estimation of plant toxicity induced by CeO NPs.
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http://dx.doi.org/10.1007/s00128-020-02892-zDOI Listing
July 2020

Gross NO Production Process, Not Consumption, Determines the Temperature Sensitivity of Net NO Emission in Arable Soil Subject to Different Long-Term Fertilization Practices.

Front Microbiol 2020 28;11:745. Epub 2020 Apr 28.

Key Laboratory of Environment Remediation and Ecological Health, Ministry of Education, College of Environmental & Resource Sciences, Zhejiang University, Hangzhou, China.

Chronic amendment of agricultural soil with synthetic nitrogen fertilization and/or livestock manure has been demonstrated to enhance the feedback intensity of net NO emission to temperature variation (i.e., temperature sensitivity, TS). Yet few studies have explored the relevance of changes in underlying gross NO production and consumption processes toward explaining this phenomenon, in particular for the latter. Furthermore, the microbe-based mechanisms associated with the variation of NO consumption process remain largely unexplored. To address this knowledge gap, a temperature- (15, 25, and 35°C) and moisture-controlled (50% water holding capacity) microcosm incubation experiment was established using an arable soil subject to long-term addition of synthetic fertilizer (NPK), a mixture of synthetic fertilizer with livestock manure (MNPK), or with no fertilizer treatment (CT). Over the incubation time period, the CH inhibition method was adopted to monitor reaction rates of gross NO production and consumption; the population sizes and community structures of I- and II-NO reducers were analyzed using quantitative PCR (Q-PCR) and terminal restriction fragment length polymorphism (T-RFLP). The results indicated that only NPK significantly increased the TS of net NO emission, and gross NO consumption process consistently occurred under all treatment combinations (temperature and fertilization) at each sampling time point. The responses of gross NO production and consumption processes to temperature elevation exhibited fertilization- and sampling time-dependent pattern, and the higher net NO production TS in the NPK treatment was underlain by its higher TS of gross production process and insensitivity of gross consumption process to temperature. The size and structure of II-NO reducers, as well as the community structure of I-NO reducers, were positively correlated with variation of gross NO production and consumption rates across all fertilization regimes. II-NO reducer abundance was less responsive to temperature change, and its community structure less susceptible to fertilization, as compared with I-NO reducers. Overall, our results demonstrate that the TS of the gross NO production process, not gross consumption, is the key step regulating the TS of net NO production, and both I- and II-NO clades are likely active NO reducers in the tested soil.
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http://dx.doi.org/10.3389/fmicb.2020.00745DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7198778PMC
April 2020

Low calcium-induced delay in development of root apoplastic barriers enhances Cd uptake and accumulation in Sedum alfredii.

Sci Total Environ 2020 Jun 7;723:137810. Epub 2020 Mar 7.

Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China; National Demonstration Center for Experimental Environment and Resources Education, Zhejiang University, Hangzhou 310058, China. Electronic address:

Mineral nutrients play an important role in heavy metal uptake and accumulation in plant. However, the effects of calcium (Ca) supply level on apoplastic transport in roots and consequences for uptake of cadmium (Cd) in hyperaccumulators are poorly understood. Here, we investigated how Ca regulated the development of apoplastic barriers in the roots of two ecotypes of Sedum alfredii and assessed its effects on Cd uptake. Results of correlation analysis indicated that Ca content was positively correlated with the development of Casparian strips (CSs) and suberin lamellae (SL) in the absence or presence of Cd. Simultaneously, low Ca supply was proven to delay the formation of endodermis CSs and suberin accumulation by decreasing the relative expressions of genes associated with CSs localization and lignin/suberin synthesis. Moreover, Cd in apoplastic fluid and cell walls (regarding the apoplastic transport) and symplastic fractions were elevated by low Ca supply. Contrary to high Ca supply, the expression levels of genes related to Cd influx and xylem loading were increased upon low Ca addition in roots of both ecotypes. All the results above suggested that low Ca supply promotes root Cd uptake via apoplastic pathway by delaying apoplastic barriers development and also regulating Cd transport to the xylem in S. alfredii.
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http://dx.doi.org/10.1016/j.scitotenv.2020.137810DOI Listing
June 2020

Identification of wheat (Triticum aestivum L.) genotypes for food safety on two different cadmium contaminated soils.

Environ Sci Pollut Res Int 2020 Mar 31;27(8):7943-7956. Epub 2019 Dec 31.

Key Laboratory of Environmental Remediation and Ecosystem Health, Ministry of Education (MOE), College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, People's Republic of China.

Over the last decade, human population has been facing great challenges in ensuring appropriate supply of food free from cadmium (Cd) contamination. Selection of genetically low-Cd wheat (Triticum aestivum L.) genotypes, with a large biomass and high accumulation of Cd in straw but low-Cd concentration in grains, is an inventive approach of phytoremediation while keeping agricultural production in moderately contaminated soils. In this study, variations in Cd uptake and translocation among the 30 wheat genotypes in two different sites were investigated in field experiments. Significant differences in grain Cd concentration were observed between the two sites, with averaged values of 0.048 and 0.053 mg kg DW, respectively. Based on straw Cd accumulation, grain Cd concentration, and TF, Bainong207 and Aikang58 for site A and Huaimai23 and Yannong21 for site B are promising candidates of low-Cd genotypes, which have considerable potential in achieving phytoremediation while keeping agricultural production on moderately or slightly Cd-polluted soil. The results indicate that it is possible to select the optimal low-Cd genotypes of wheat for different soil types by taking consideration of the effect of soil-wheat genotype interaction on grain Cd concentration.
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http://dx.doi.org/10.1007/s11356-019-07261-wDOI Listing
March 2020

Ochrobactrum intermedium and saponin assisted phytoremediation of Cd and B[a]P co-contaminated soil by Cd-hyperaccumulator Sedum alfredii.

Chemosphere 2020 Apr 6;245:125547. Epub 2019 Dec 6.

College of Resources, Sichuan Agricultural University, Chengdu, 611130, China. Electronic address:

Pot-culture experiments were conducted to investigate the potential of microorganism-saponin assisted phytoremediation of cadmium (Cd) and benzo(a)pyrene (B[a]P) co-contaminated soil using Cd-hyperaccumulator Sedum alfredii. Results showed that B[a]P-degrading bacterium (Ochrobactrum intermedium B[a]P-16) inoculation significantly increased root (by 22.1-24.1%) and shoot (by 20.5-23.4%) biomass of S. alfredii, whereas the application of saponin had no effect on the growth of S. alfredii. The saponin solution at 2 g L extracted more Cd and B[a]P than water, saponin enhanced Cd and B[a]P bioavailability in soil and thus promoted their uptake and accumulation in S. alfredii. The activity of B[a]P-16, dehydrogenase and polyphenol oxidase in co-contaminated soil was promoted by growing S. alfredii, and the application of B[a]P-16 and saponins caused a significant (P < 0.05) increase in both enzyme activities. The maximum B[a]P removal rate (82.0%) and Cd phytoextraction rate (19.5%) were obtained by co-application of S. alfredii with B[a]P-16 and saponin. The B[a]P-16 and plant promoted biodegradation were the predominant contributors towards removal of B[a]P from soil. A significant (P < 0.05) synergistic effect of B[a]P-16 and saponin on B[a]P and Cd removal efficiency was observed in this study. It is suggested that planting S. alfredii with application of B[a]P-16 and saponin would be an effective method for phytoremediation of soil co-contaminated with Cd and PAHs.
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http://dx.doi.org/10.1016/j.chemosphere.2019.125547DOI Listing
April 2020

Cd-induced difference in root characteristics along root apex contributes to variation in Cd uptake and accumulation between two contrasting ecotypes of Sedum alfredii.

Chemosphere 2020 Mar 8;243:125290. Epub 2019 Nov 8.

College of Resources, Sichuan Agricultural University, Chengdu, 611130, China. Electronic address:

The root apex is the most active part for water and ions uptake, however, longitudinal alterations in root characteristics along root apex and consequences for metal uptake in hyperaccumulator are poorly understood. Here, we compared cadmium (Cd)-induced longitudinal alterations in root apex of two ecotypes of Sedum alfredii and assess their effects on Cd uptake. Under Cd treatment, cell death began from epidermis to the stele in non-hyperaccumulating ecotype (NHE) over time, and the number of dead cells was significantly higher than that in hyperaccumulating ecotype (HE). Cd-induced the presence of border-like cells (BLCs) surrounding the root tip of NHE prevented Cd from entering roots, however, almost no BLCs were observed in the root tip of in HE. Besides, Cd-treated NHE exhibited 76% and 52% decrease in the proportions of meristematic and elongation zone, respectively, resulting in lower Cd influx and less intensive Cd-fluorescence in these zones, as compared with HE. In the differentiation zone, Cd induced earlier initiation of root hairs (RHs), lower RHs-density, shorter RHs-length, thicker RHs-radius and less trichoblasts in NHE than those in HE. These remarkable variations led to less Cd influx and lower intensity of Cd-fluorescence in RHs of NHE than those of HE. Furthermore, decline in cell wall thickness under Cd exposure resulted in less cell-wall-bond Cd in the cell wall of HE. Therefore, Cd-induced alterations in root characteristics alongside root apex contributed to the difference in Cd uptake and accumulation between two ecotypes of S. alfredii.
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http://dx.doi.org/10.1016/j.chemosphere.2019.125290DOI Listing
March 2020

Bioavailability and cytotoxicity of Cerium- (IV), Copper- (II), and Zinc oxide nanoparticles to human intestinal and liver cells through food.

Sci Total Environ 2020 Feb 3;702:134700. Epub 2019 Nov 3.

Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, China. Electronic address:

Anthropogenic nanoparticles (NPs) are emitted to the environment and may be present in vegetables for human consumption. However, the toxicity of NPs exposure through food lack systematical investigations. In order to propose a systematical study, lettuce grown in a Cerium- (IV), Copper- (II) and Zinc oxide NP contaminated environment were digested. This digestate was used to culture human intestine cells (i.e. epithelial colorectal adenocarcinoma cells, Caco-2). The basolateral juice produced by the intestinal cells was then used to culture normal human liver (HL-7702) cells. Bioavailability and biotoxicity of the NPs in the vitro models were assessed. NPs were found to be taken up from the environment by vegetables, and may thus be transferred to humans through oral exposure. Bioavailability and the effect of their concentration in the digestate medium differed in regards to NP materials. The levels of NPs found in the digestate were detrimental to intestine cells, while the liver cells exposed to lower concentrations of NP in the bodily fluid showed no statically significant change in cell necrosis. A closer assessment of the detrimental effect of the studied NPs to Caco-2 cells revealed that the damage was mainly related to the solubility of the NPs. This may partly be due to that the more soluble NP material (ZnO > CuO > CeO) render higher metal ion release and thus higher bioavailability. This appeared to cause more cell death, and even lead to local intestinal inflammation. Although no liver cells died, there was an increase of ROS level, causing ROS-related DNA damage prior to cell necrosis. The findings in this study enhances our understanding of the relative detrimental effect of different types of NPs, and the mechanisms causing their biotoxicity in human cells through food.
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http://dx.doi.org/10.1016/j.scitotenv.2019.134700DOI Listing
February 2020

Unique root exudate tartaric acid enhanced cadmium mobilization and uptake in Cd-hyperaccumulator Sedum alfredii.

J Hazard Mater 2020 02 6;383:121177. Epub 2019 Sep 6.

College of Resources, Sichuan Agricultural University, Chengdu 611130, China. Electronic address:

Low molecular weight organic acids (LMWOA) involved in heavy metal tolerance, translocation, and accumulation in plants. However, underlying mechanism of LMWOA secretion in metal mobilization and uptake in hyperaccumulator still need to be identified. In this study, a C labeling rhizobox was designed to investigate the composition and distribution of LMWOA in the rhizosphere of S. alfredii. The result showed that about 2.30%, 2.25% and 2.35% of the assimilated C was incorporated into oxalic acid, malic acid, and tartaric acid in rhizosphere of S. alfredii after CO assimilation, respectively. Oxalic acid, malic acid, and tartaric acid were the predominant LMWOA in rhizosphere soil solution of hyperaccumulating ecotype (HE) S. alfredii, however, almost no tartaric acid was detected for non-hyperaccumulating ecotype (NHE). Tartaric acid was identified as the unique root exudate from HE S. alfredii which was mainly distributed within the range of rhizosphere 0-6 mm. Tartaric acid significantly increased the solubility of four Cd minerals. HE S. alfredii treated with tartrate + CdCO had higher Cd contents and larger biomass than CdCO treatment. Cadmium accumulation in HE S. alfredii was promoted by the exudation of tartaric acid, which was highly efficient in Cd solubilization due to the formation of soluble Cd-tartrate complexes.
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http://dx.doi.org/10.1016/j.jhazmat.2019.121177DOI Listing
February 2020

Reduction of NO emission by biochar and/or 3,4-dimethylpyrazole phosphate (DMPP) is closely linked to soil ammonia oxidizing bacteria and nosZI-NO reducer populations.

Sci Total Environ 2019 Dec 31;694:133658. Epub 2019 Jul 31.

Ministry of Education Key Laboratory of Environment Remediation and Ecological Health, College of Environmental & Resource Sciences, Zhejiang University, Hangzhou 310058, China. Electronic address:

Biochar has been demonstrated to reduce nitrous oxide (NO) emissions from soils, but its effect is highly soil-dependent. In particular, in soils with strong nitrification potential, biochar addition may increase NO emissions. Thus, in soils with strong nitrification potential, the combination of biochar with the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) may be more effective in reducing NO emissions than biochar alone. However, the combined use of biochar and DMPP on soil NO emissions is relatively unexplored, and underlying microbial mechanisms of how biochar and/or DMPP amendment affect NO emissions is still largely unknown. Here, a 30-day incubation experiment was established with four treatments: CK (control), BC (biochar), DMPP, and BD (biochar and DMPP), all at agronomically recommended rates, and N cycling assessed following addition of urea. Treatment of soil with BC, DMPP and BD reduced NO emissions (compared with urea alone) by 59.1%, 95.5% and 74.1%, respectively. Quantification of N cycling genes (amoA, nirS, nirK, and nosZ) indicated that biochar stimulated growth of ammonia oxidizing archaea (AOA) and bacteria (AOB), while DMPP alone inhibited the activity and growth of AOB. In the BD treatment, DMPP was absorbed onto biochar reducing its efficacy in inhibiting AOB growth. The response patterns of nirS/nirK nitrite-reducing denitrifiers to biochar and/or DMPP addition varied among clades. Notably, biochar and/or DMPP increased the abundance of nosZI and nosZII-NO reducers, but nosZI-clade taxa were more closely associated with reducing NO emission than nosZII taxa. Overall, our findings proved that the dynamics of AOB and nosZI-NO reducers resulting from the addition of biochar and/or DMPP played a key role in governing soil NO emissions.
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http://dx.doi.org/10.1016/j.scitotenv.2019.133658DOI Listing
December 2019

Enhancement of phytoextraction of Pb by compounded activation agent derived from fruit residue.

Int J Phytoremediation 2019 11;21(14):1449-1456. Epub 2019 Jul 11.

College of Environmental and Resource Sciences, Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, Zhejiang University, Hangzhou, China.

Chelate-assisted phytoextraction is an attractive strategy to remove toxic metals from soil. However, there is lack of an effective and sustainable chelating agent. In this study, 11 kinds of fruit residue were extracted and selected to combine with N, N-bis (carboxymethyl) glutamic acid (GLDA) (0.7%) and tea saponin (4%) for the compounded activation agent (CAA), and its enhancement on Pb phytoextraction by was further evaluated by pot experiment. Among 11 fruit residue extracts, lemon residue showed the highest ability (34.7%) to extract Pb from soil. Through combining with GLDA (0.7%) and tea saponin (4%) at the optimal volume ratio of 15:2.5:2.5, the CAA removed Pb most effectively (57.1%) from soil and increased the solubility of three Pb mineral (PbS, PbCO and PbSO) by 8.7-56.4 times. In pot experiment, the addition of high dosage (15 mL) CAA increased the biomass of by 52% and doubled the Pb accumulation. In addition, CAA-assisted phytoextraction also increased both water-soluble and acid-soluble Pb in soil, while reduced the proportion of the immobile Pb (oxidizable and residual). Generally, the compounded activation agent derived from lemon residue could be considered as-a promising enhancer for Pb phytoextraction.
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http://dx.doi.org/10.1080/15226514.2019.1633266DOI Listing
November 2019

Role of Vertical Transmission of Shoot Endophytes in Root-Associated Microbiome Assembly and Heavy Metal Hyperaccumulation in Sedum alfredii.

Environ Sci Technol 2019 06 7;53(12):6954-6963. Epub 2019 Jun 7.

Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences , Zhejiang University , Hangzhou 310058 , China.

The transmission mode of shoot-associated endophytes in hyperaccumulators and their roles in root microbiome assembly and heavy metal accumulation remain unclear. Using 16S rRNA gene profiling, we investigated the vertical transmission of shoot-associated endophytes in relation to growth and Cd/Zn accumulation of Sedum alfredii ( Crassulaceae). Endophytes were transmitted from shoot cuttings to the rhizocompartment of new plants in both sterilized (γ-irradiated) and native soils. Vertical transmission was far more efficient in the sterile soil, and the transmitted endophytes have become a dominant component of the newly established root-associated microbiome. Based on 16S rRNA genes, the vertically transmitted taxa were identified as the families of Streptomycetaceae, Nocardioidaceae, Pseudonocardiaceae, and Rhizobiaceae. Abundances of Streptomycetaceae, Nocardioidaceae, and Pseudonocardiaceae were strongly correlated with increased shoot biomass and total Cd/Zn accumulation. Inoculation of S. alfredii with the synthetic bacterial community sharing the same phylogenetic relatedness with the vertically transmitted endophytes resulted in significant improvements in plant biomass, root morphology, and Cd/Zn accumulation. Our results demonstrate that successful vertical transmission of endophytes from shoots of S. alfredii to its rhizocompartments is possible, particularly in soils with attenuated microbiomes. Furthermore, the endophyte-derived microbiome plays an important role in metal hyperaccumulation.
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http://dx.doi.org/10.1021/acs.est.9b01093DOI Listing
June 2019

Simultaneous remediation of sediments contaminated with sulfamethoxazole and cadmium using magnesium-modified biochar derived from Thalia dealbata.

Sci Total Environ 2019 Apr 27;659:1448-1456. Epub 2018 Dec 27.

Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310029, China. Electronic address:

In situ remediation and assessment of sediments contaminated with both antibiotics and heavy metals remains a technological challenge. In this study, MgCl-modified biochar (BCM) was obtained at 500 °C through slow pyrolysis of Thalia dealbata and used for remediation of sediments contaminated by sulfamethoxazole (SMX) and Cd. The BCM showed greater surface area (110.6 m g) than pristine biochar (BC, 7.1 m g). The SMX sorption data were well described by Freundlich model while Langmuir model was better for the Cd sorption data. The addition of 5.0% BCM significantly increased the sorption of SMX (by 50.8-58.6%) and Cd (by 24.2-25.6%) on sediments in both single and binary systems as compared with 5.0% BC. SMX sorption in sediments was significantly improved by addition of Cd, whereas SMX has no influence on Cd sorption on sediments. The addition of BCM distinctly decreased both SMX (by 51.4-87.2%) and Cd concentrations (by 56.2-91.3%) in overlying water, as well as in TCLP extracts (by 55.6-86.1% and 58.2-91.9% for SMX and Cd, respectively), as compared with sediments without biochar. Both germination rate and root length of pakchoi increased with increasing doses of BCM in contaminated sediments, 5.0% BCM showed greater promotion on pakchoi growth than 5.0% BC. Overall, BCM in the sediments does not only decrease the bioavailability of SMX and Cd, but it also diminishes the phytotoxicity, and thereby shows great application potential for in situ remediation of sediments polluted with antibiotics and heavy metals.
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http://dx.doi.org/10.1016/j.scitotenv.2018.12.361DOI Listing
April 2019

Assessment of potential dietary toxicity and arsenic accumulation in two contrasting rice genotypes: Effect of soil amendments.

Chemosphere 2019 Jun 2;225:104-114. Epub 2019 Mar 2.

Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China.

High concentration of arsenic (As) in rice is a serious problem worldwide. Pot experiments were conducted to assess the potential dietary toxicity of arsenic and effect of various soil amendments on arsenic accumulation in rice grains. Two basmati rice genotypes were used to conduct pot experiments using various levels of arsenic (10, 25, 50 and 100 mg kg soil). In addition, plants were exposed to soil collected from a well documented arsenic contaminated site. Contrasting results for growth, yield and grain arsenic concentration were obtained for basmati-385 (Bas-385), exhibiting tolerance (56% yield improvement at 10 mg As kg), while genotype BR-1 showed 18% yield decline under same conditions. Furthermore, application of soil amendments such as iron (Fe), phosphate (PO) and farmyard manure (FYM) at 50 mg kg, 80 kg ha and 10 t ha, respectively improved the plant height and biomass in both genotypes. Accumulation of arsenic in rice grain followed a linear trend in BR-1 whereas a parabolic relationship was observed in Bas-385. Both genotypes exhibited a positive response to iron sulfate amendment with significant reduction in grain arsenic concentrations. Regression analysis gave soil arsenic threshold values of 12 mg kg in Bas-385 and 10 mg kg in BR-1 for potential dietary toxicity. This study suggests that genotype Bas-385 can be used for safe rice production in areas with soil arsenic contamination up to 12 mg kg and that appropriate dose of iron sulfate for soil amendment can be used effectively to reduce translocation of arsenic to rice grain.
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http://dx.doi.org/10.1016/j.chemosphere.2019.02.202DOI Listing
June 2019

Successive phytoextraction alters ammonia oxidation and associated microbial communities in heavy metal contaminated agricultural soils.

Sci Total Environ 2019 May 25;664:616-625. Epub 2019 Jan 25.

Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China. Electronic address:

Phytoextraction is an attractive strategy for remediation of soils contaminated by heavy metal (HM), yet the effects of this practice on biochemical processes involved in soil nutrient cycling remain unknown. Here we investigated the impact of successive phytoextraction with a Cd/Zn co-hyperaccumulator Sedum alfredii (Crassulaceae) on potential nitrification rates (PNRs), abundance and composition of nitrifying communities and functional genes associated with nitrification using archaeal and bacterial 16S rRNA gene profiling and quantitative real-time PCR. The PNRs in rhizosphere were significantly (P < 0.05) lower than in the unplanted soils, and decreased markedly with planting time. The decrease of PNR was more paralleled by changes in numbers of copy and transcript of archaeal amoA gene than the bacterial counterpart. Phylogenetic analysis revealed that phytoextraction induced shifts in community structure of soil group 1.1b lineage-dominated ammonia-oxidizing archaea (AOA), Nitrosospira cluster 3-like ammonia-oxidizing bacteria (AOB) and Nitrospira-like nitrite-oxidizing bacteria (NOB). A strong positive correlation was observed between amoA gene transcript numbers and PNRs, whereas root exudates showed negative effect on PNR. This effect was further corroborated by incubation test with the concentrated root exudates of S. alfredii. Partial least squares path model demonstrated that PNR was predominantly controlled by number of AOA amoA gene transcripts which were strongly influenced by root exudation and HM level in soil. Our result reveals that successive phytoextraction of agricultural soil contaminated by HMs using S. alfredii could inhibit ammonia oxidation and thereby reduce nitrogen loss.
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http://dx.doi.org/10.1016/j.scitotenv.2019.01.315DOI Listing
May 2019

Abscisic acid-mediated modifications of radial apoplastic transport pathway play a key role in cadmium uptake in hyperaccumulator Sedum alfredii.

Plant Cell Environ 2019 05 19;42(5):1425-1440. Epub 2019 Jan 19.

Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China.

Abscisic acid (ABA) is a key phytohormone underlying plant resistance to toxic metals. However, regulatory effects of ABA on apoplastic transport in roots and consequences for uptake of metal ions are poorly understood. Here, we demonstrate how ABA regulates development of apoplastic barriers in roots of two ecotypes of Sedum alfredii and assess effects on cadmium (Cd) uptake. Under Cd treatment, increased endogenous ABA level was detected in roots of nonhyperaccumulating ecotype (NHE) due to up-regulated expressions of ABA biosynthesis genes (SaABA2, SaNCED), but no change was observed in hyperaccumulating ecotype (HE). Simultaneously, endodermal Casparian strips (CSs) and suberin lamellae (SL) were deposited closer to root tips of NHE compared with HE. Interestingly, the vessel-to-CSs overlap was identified as an ABA-driven anatomical trait. Results of correlation analyses and exogenous applications of ABA/Abamine indicate that ABA regulates development of both types of apoplastic barriers through promoting activities of phenylalanine ammonialyase, peroxidase, and expressions of suberin-related genes (SaCYP86A1, SaGPAT5, and SaKCS20). Using scanning ion-selected electrode technique and PTS tracer confirmed that ABA-promoted deposition of CSs and SL significantly reduced Cd entrance into root stele. Therefore, maintenance of low ABA levels in HE minimized deposition of apoplastic barriers and allowed maximization of Cd uptake via apoplastic pathway.
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http://dx.doi.org/10.1111/pce.13506DOI Listing
May 2019

Current status of agricultural soil pollution by heavy metals in China: A meta-analysis.

Sci Total Environ 2019 Feb 15;651(Pt 2):3034-3042. Epub 2018 Oct 15.

Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China. Electronic address:

In the last decades, agricultural soil pollution by heavy metals has been extensively investigated in China. However, nearly all studies were field monitoring in small regions and/or with limited samples, which may not represent soil pollution situation at the national scale. In this paper, attempt was made to provide a comprehensive report about heavy metal pollution in China based on meta-analysis of reviewed data. Given the characteristics of field monitoring studies, the weighted mean values based on "sampling number", "study area", and "standard deviation" were calculated to represent national mean values. In addition, subgroup analysis and cumulative meta-analysis were applied to explore the spatial and temporal variations as well as the influence of cropping systems. 336 articles published from 2005 to 2017 were reviewed in the analysis. Eight heavy metals (cadmium (Cd), chromium (Cr), mercury (Hg), lead (Pb), arsenic (As), copper (Cu), zinc (Zn) and nickel (Ni)) were analyzed. The contents of Cd and Hg were increased compared to background values, while, other six elements showed no significant accumulation. Little pollution was found in normal farmland, which was far from obvious anthropogenic emissions, but Cd and Hg in mining & smelting areas and industrial areas continued to accumulate significantly. Moreover, the accumulation had slowed down or decreased since 2012, which might be due to reduced use of coals, non-ferrous metals and agro-chemicals. Heavy metal contents were generally higher in southwest and south coastal areas but lower in northwest regions, whereas vegetable and paddy fields had higher concentrations than upland and other land use. This study provides information on soil pollution caused by heavy metals and its affected regions and cropping systems on a national scale. It can be useful for developing heavy metal pollution control and management strategies in China.
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http://dx.doi.org/10.1016/j.scitotenv.2018.10.185DOI Listing
February 2019

Effects of elevated CO and endophytic bacterium on photosynthetic characteristics and cadmium accumulation in Sedum alfredii.

Sci Total Environ 2018 Dec 22;643:357-366. Epub 2018 Jun 22.

Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China. Electronic address:

Elevated CO and use of endophytic microorganisms have been considered as efficient and novel ways to improve phytoextraction efficiency. However, the interactive effects of elevated CO and endophytes on hyperaccumulator is poorly understood. In this study, a hydroponics experiment was conducted to investigate the combined effect of elevated CO (eCO) and inoculation with endophyte SaMR12 (ES) on the photosynthetic characteristics and cadmium (Cd) accumulation in hyperaccumulator Sedum alfredii. The results showed that eCO × ES interaction promoted the growth of S. alfredii, shoot and root biomass net increment were increased by 264.7 and 392.3%, respectively, as compared with plants grown in ambient CO (aCO). The interaction of eCO and ES significantly (P < 0.05) increased chlorophyll content (53.2%), Pn (111.6%), Pn (59.8%), AQY (65.1%), and Lsp (28.8%), but reduced Gs, Tr, Rd, and Lcp. Increased photosynthetic efficiency was associated with higher activities of rubisco, Ca-ATPase, and Mg-ATPase, and linked with over-expression of two photosystem related genes (SaPsbS and SaLhcb2). PS II activities were significantly (P < 0.05) enhanced with Fv/Fm and Φ(II) increased by 12.3 and 13.0%, respectively, compared with plants grown in aCO. In addition, the net uptake of Cd in the shoot and root tissue of S. alfredii grown in eCO × ES treatment was increased by 260.7 and 434.9%, respectively, due to increased expression of SaHMA2 and SaCAX2 Cd transporter genes. Our results suggest that eCO × ES can promote the growth of S. alfredii due to increased photosynthetic efficiency, and improve Cd accumulation and showed considerable potential of improving the phytoextraction ability of Cd by S. alfredii.
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http://dx.doi.org/10.1016/j.scitotenv.2018.06.131DOI Listing
December 2018

The contrasting effects of N-(n-butyl) thiophosphoric triamide (NBPT) on NO emissions in arable soils differing in pH are underlain by complex microbial mechanisms.

Sci Total Environ 2018 Nov 9;642:155-167. Epub 2018 Jun 9.

Ministry of Education Key Laboratory of Environment Remediation and Ecological Health, College of Environmental & Resource Sciences, Zhejiang University, Hangzhou 310058, China. Electronic address:

The urease inhibitor, N-(n-butyl) thiophosphoric triamide (NBPT), has been proposed to reduce synthetic fertilizer-N losses, including nitrous oxide (NO) emissions from agricultural soils. However, the response of NO emission to NBPT amendment is inconsistent across soils and associated microbial mechanisms remain largely unknown. Here we performed a meta-analysis of the effects of NBPT on NO emissions and found NBPT significantly reduced NO emissions in alkaline soils whereas no obvious effects exhibited in acid soils. Based on the finding of meta-analysis that pH was a key modifier in regulating the effect of NBPT on NO emissions, we selected two arable soils differing in pH and conducted a microcosm study. In conjunction with measurement of NO emission, community structure and abundance of functional guilds were assessed using T-RFLP and qPCR. Our results showed NBPT retarded urea hydrolysis and inhibited nitrification, but stimulated NO emission in alkaline soil, whereas it exhibited no remarkable effects in acid soil, thereby only partly confirming the results of meta-analysis. Abundances of AOB and ureC-containing bacteria decreased, while abundance of AOA increased in both soils with NBPT addition. For acid soil, NO emissions were significantly correlated with both abundances and community structures of AOA and ureC-containing bacteria, as well as abundance of AOB; for alkaline soil, abundances and community structures of AOB were correlated with NO emission, as well as community structures of ureC-containing bacteria and archaea, indicating an inconsistent response pattern of community traits of NO emissions-related functional guilds to NBPT between alkaline soil and acid soil. Our findings suggest that (i) efficacy of NBPT in NO emission was mainly influenced by soil pH and (ii) variable effects of NBPT on NO emission might originate not only from the direct effect of NBPT on community traits of urease-positive microbes, but from the indirect effect on ammonia oxidizers.
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http://dx.doi.org/10.1016/j.scitotenv.2018.05.356DOI Listing
November 2018

Endophytic bacterium Buttiauxella sp. SaSR13 improves plant growth and cadmium accumulation of hyperaccumulator Sedum alfredii.

Environ Sci Pollut Res Int 2018 Aug 23;25(22):21844-21854. Epub 2018 May 23.

Ministry of Education Key Laboratory of Environmental Remediation and Ecological Health, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou, 310058, China.

Inoculation with endophytic bacterium has been considered as a prospective application to improve the efficiency of phytoextraction. In this study, the effect of Buttiauxella sp. SaSR13 (SaSR13), a novel endophytic bacterium isolated from the root of hyperaccumulator Sedum alfredii, on plant growth and cadmium (Cd) accumulation in S. alfredii was investigated. Laser scanning confocal microscopic (LSCM) images showed that SaSR13 was mainly colonized in the root elongation and mature zones. The inoculation with SaSR13 to Cd-treated plants significantly enhanced plant growth (by 39 and 42% for shoot and root biomass, respectively), chlorophyll contents (by 38%), and Cd concentration in the shoot and root (by 32 and 22%, respectively). SaSR13 stimulated the development of roots (increased root length, surface area, and root tips number) due to an increase in the indole-3-acid (IAA) concentrations and a decrease in the concentrations of superoxide anion (O) in plants grown under Cd stress. Furthermore, inoculation with SaSR13 enhanced the release of root exudates, especially malic acid and oxalic acid, which might have facilitated the uptake of Cd by S. alfredii. It is suggested that inoculation with endophytic bacterium SaSR13 is a promising bioaugmentation method to enhance the Cd phytoextraction efficiency by S. alfredii.
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http://dx.doi.org/10.1007/s11356-018-2322-6DOI Listing
August 2018