Silicon and selenium alleviate cadmium toxicity in Artemisia selengensis Turcz by regulating the plant-rhizosphere.

Soil cadmium (Cd) pollution has emerged as a pressing concern due to its deleterious impacts on both plant physiology and human well-being. Silicon (Si) is renowned for its ability to mitigate excessive Cd accumulation within plant cells and reduce the mobility of Cd in soil, whereas Selenium (Se) augments plant antioxidant capabilities and promotes rhizosphere microbial activity. However, research focusing on the simultaneous utilization of Si and Se to ameliorate plant Cd toxicity through multiple mechanisms within the plant-rhizosphere remains comparatively limited. This study combined hydroponic and pot experiments to investigate the effects of the combined application of Si and Se on Cd absorption and accumulation, as well as the growth and rhizosphere of A. selengensis Turcz under Cd stress. The results revealed that a strong synergistic effect was observed between both Si and Se. The combination of Si and Se significantly increased the activity and content of enzymes and non-enzyme antioxidants within A. selengensis Turcz, reduced Cd accumulation and inhibiting its translocation from roots to shoots. Moreover, Si and Se application improved the levels of reducing sugar, soluble protein, and vitamin C, while reducing nitrite content and Cd bioavailability. Furthermore, the experimental results showed that the combination of Si and Se not only increased the abundance of core rhizosphere microorganisms, but also stimulated the activity of soil enzymes, which effectively limited the migration of Cd in the soil. These findings provided valuable insights into the effective mitigation of soil Cd toxicity to plants and also the potential applications in improving plant quality and safety.

Co-foliar application of zinc and nano-silicon to rice helps in reducing cadmium exposure risk: Investigations through in-vitro digestion with human cell line bioavailability assay.

Foliar application of zinc (Zn) or silicon nanoparticles (Si-NPs) may exert regulatory effects on cadmium (Cd) accumulation in rice grains, however, their impact on Cd bioavailability during human rice consumption remains elusive. This study comprehensively investigated the application of Zn with or without Si-NPs in reducing Cd accumulation in rice grains as well to exactly evaluate the potential risk of Cd exposure resulting from the rice consumption by employing field experiment as well laboratory bioaccessibility and bioavailability assay. Sole Zn (ZnSO4) or in combination with Si (ZnSO4 +Si and ZnO+Si) efficiently lowered the Cd concentration in rice grains. However, the impact of bioaccessible (0.1215-0.1623 mg kg-1) and bioavailable Cd (0.0245-0.0393 mg kg-1) during simulated human rice consumption depicted inconsistent trend. The straw HCl-extractable fraction of Cd (FHCl-Cd) exhibited a significant correlation with total, bioaccessible, and bioavailable Cd in grains, indicating the critical role of FHCl-Cd in Cd accumulation and translocation from grains to human. Additionally, foliar spraying of Zn+Si raised the nutritional value of rice grains, leading to increased protein content and reduced phytic acid concentration. Overall, this study demonstrates the potential of foliar application of ZnSO4 +Si in mitigating the Cd levels in rice grains and associated health risks upon consumption.

Seed nano-priming with multiple nanoparticles enhanced the growth parameters of lettuce and mitigated cadmium (Cd) bio-toxicity: An advanced technique for remediation of Cd contaminated environments.

Seed nano-priming can be used as an advanced technology for enhancing seed germination, plant growth, and crop productivity; however, the potential role of seed nano-priming in ameliorative cadmium (Cd) bio-toxicity under Cd stress has not yet been sufficiently investigated. Therefore, in this study we investigated the beneficial impacts of seed priming with low (L) and high (H) concentrations of nanoparticles including nSiO2 (50/100 mg L-1), nTiO2 (20/60 mg L-1), nZnO (50/100 mg L-1), nFe3O4 (100/200 mg L-1), nCuO (50/100 mg L-1), and nCeO2 (50/100 mg L-1) on lettuce growth and antioxidant enzyme activities aiming to assess their efficacy for enhancing plant growth and reducing Cd phytotoxicity. The results showed a significant increase in plant growth, biomass production, antioxidant enzyme activities, and photosynthetic efficiency in lettuce treated with nano-primed nSiH + Cd (100 mg L-1), nTiH + Cd (60 mg L-1), and nZnL + Cd (50 mg L-1) under Cd stress. Moreover, nano-priming effectively reduced the accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA) in lettuce shoots. Interestingly, nano-primed nSiH + Cd, nTiH + Cd, and nZnL + Cd demonstrated efficient reduction of Cd uptake, less translocation factor of Cd with high tolerance index, ultimately reducing toxicity by stabilizing the root morphology and superior accumulation of critical nutrients (K, Mg, Ca, Fe, and Zn). Thus, this study provides the first evidence of alleviating Cd toxicity in lettuce by using multiple nanoparticles via priming strategy. The findings highlight the potential of nanoparticles (Si, Zn, and Ti) as stress mitigation agents for improved crop growth and yield in Cd contaminated areas, thereby offering a promising and advanced approach for remediation of Cd contaminated environments.

Effect of foliar application of nanoparticles on growth, physiology, and antioxidant enzyme activities of lettuce (Lactuca sativa L.) plants under cadmium toxicity.

Nanotechnology has attracted the interest of scientists due to its wide range of application specifically in agriculture. Nanoparticles (NPs) may act as a promising materials to alleviate cadmium (Cd) stress in plants. This study aims to assess the impact of multiple nanoparticles including nSiO2 (50 mg L-1:100 mg L-1), nTiO2 (20 mg L-1:60 mg L-1), nZnO (50 mg L-1:100 mg L-1), nFe3O4 (100 mg L-1:200 mg L-1), nCuO (50 mg L-1:100 mg L-1), and nCeO2 (50 mg L-1:100 mg L-1) in combination with CdCl2 (5 µM) to mitigate Cd toxicity in lettuce through foliar application in hydroponic solution. Current findings indicate that foliar application of nSiL + Cd (50 mg L-1), nZnL + Cd (50 mg L-1), and nTiL + Cd (20 mg L-1) is more effective in improving growth, biomass, root architecture, and elevated photosynthetic efficiency, which might be attributed to the increasing uptake of essential micronutrient (K, Mg, Ca, Fe, Zn) under Cd stress. Similarly, treatment with nanoparticles leads to reduced accumulation of ROS and MDA in lettuce, while enhancing the SOD, POD, CAT, and APX activities. The results showed that nanoparticles have high tolerance against Cd as depicted by the inhibition in Cd accumulation by 3.2-58% and 10-72% in roots as well as edible parts of lettuce, respectively. In addition, Cd alone reduces the morphological traits, antioxidant enzyme activity, and photosynthetic activity, while increasing the ROS, MDA, and Cd accumulation in lettuce. This comprehensive study suggests the role of nanoparticles in reducing Cd toxicity in lettuce, signifying their importance as stress mitigation agents. However, long-term pot, priming, and field trials are needed to identify the optimal nanoparticle for the lettuce under variable environmental conditions.

Cadmium mobility and health risk assessment in the soil-rice-human system using in vitro biaccessibility and in vivo bioavailability assay: Two year field experiment.

Humans are mainly exposed to cadmium (Cd) due to the rice consumption, however there exist considerable differences across rice cultivars in terms of Cd absorption and accumulation in the grains, and subsequent release after digestion (bioaccessibility), as well as uptake by Caco-2 cells of humans (bioavailability). This study comprised of field and lab simulation trials where in the field, firstly 39 mid-rice cultivars were screened for their phytoremediation potential coupled with safe production in relation to uptake and translocation of Cd. Lower Cd concentrations (˂0.2 mg kg-1) in polished rice of 74 % cultivars were ascribed to the increased root to straw translocation indicating that straw may acquire higher accumulation of Cd. Furthermore, the ionomic profile demonstrated that the spatial distribution of metals in different rice organs corresponds to the plant growth morphology. In the second year, in vitro-in vivo assay model was employed to assess the bioaccessibility and bioavailability of Cd in polished rice and to further estimate the daily Cd intake by humans through rice grains. The results of bioaccessibility and bioavailability assays and daily estimated Cd intake presented the corresponding values of 39.02-59.76 %, 8.69-24.26 %, and 0.0185-0.9713 µg kg-1 body weight day-1, respectively. There exists a strong connection between total Cd and bioaccessible Cd to humans (R2 = 0.94, P < 0.01). Polynomial fitting (R2 = 0.91, P < 0.01) showed a better statistically significant correlation between total Cd contents and bioavailable levels, suggesting that in vitro-in vivo assays should be considered in future studies. The results of field experiments and in vitro-in vivo assays recommended the Tianyouhuazhan (MR-29), Heliangyou1hao (MR-17), and Yongyou15 (MR-1) as suitable mid-rice cultivars for the phytoremediation of slightly Cd contaminated soils coupled with rice agro-production due to their high nutritional value and low total and bioavailable Cd for human.

The involvement of nitric oxide and ethylene on the formation of endodermal barriers in response to Cd in hyperaccumulator Sedum alfredii.

Nitric oxide (NO) and ethylene are both important signaling molecules which participate in numerous plant development processes and environmental stress resistance. Here, we investigate whether and how NO interacts with ethylene during the development of endodermal barriers that have major consequences for the apoplastic uptake of cadmium (Cd) in the hyperaccumulator Sedum alfredii. In response to Cd, an increased NO accumulation, while a decrease in ethylene production was observed in the roots of S. alfredii. Exogenous supplementation of NO donor SNP (sodium nitroprusside) decreased the ethylene production in roots, while NO scavenger cPTIO (2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) had the opposite effect. The exogenous addition of NO affected the ethylene production through regulating the expression of genes related to ethylene synthesis. However, upon exogenous ethylene addition, roots retained their NO accumulation. The abovementioned results suggest that ethylene is downstream of the NO signaling pathway in S. alfredii. Regardless of Cd, addition of SNP promoted the deposition of endodermal barriers via regulating the genes related to Casparian strips deposition and suberization. Correlation analyses indicate that NO positively modifies the formation of endodermal barriers via the NO-ethylene signaling pathway, Cd-induced NO accumulation interferes with the synthesis of ethylene, leading to a deposition of endodermal barriers in S. alfredii.

Positive effects of applying endophytic bacteria in eggplant-Sedum intercropping system on Cd phytoremediation and vegetable production in cadmium polluted greenhouse.

The combination of intercropping and phytoremediation in the remediation of cadmium contaminated soil is an emerging model in recent years, but the results of previous studies are inconsistent. In the field experiment, eggplant was intercropped with hyperaccumulator Sedum alfredii Hance (inoculated or not inoculated with endophytic bacteria) to study the effects of intercropping on vegetable safety production, phytoremediation efficiency of hyperaccumulator and variation of soil available nutrients. The results showed that the intercropping treatment had a negative effect on the growth of eggplant and Sedum, but endophyte SaMR12 alleviated the inhibition of intercropping on plant growth. Intercropping treatment increases the Cd concentration in edible part of eggplant to 1.34 mg/kg compared with eggplant monoculture (1.19 mg/kg). While the application of SaMR12 reduces the Cd concentration of eggplant fruit to 0.95 mg/kg and significantly promotes the Cd uptake by Sedum. What's more surprising is that compared with eggplant monocropping, the content of soil available nitrogen, phosphorus and potassium in the treatment of intercropping with inoculated Sedum increased significantly. And according to the correlation analysis of various indexes of plants and soil, the Cd content of eggplant is negatively correlated with the available phosphorus and potassium in the soil, while the Cd content of Sedum is positively correlated with it, which suggested that the application of phosphorus and potassium fertilizers in this experimental site was beneficial to reduce Cd content in eggplant and improve Cd phytoextraction of Sedum. Therefore, in the daily production of moderately Cd-contaminated soil, intercropping eggplant with Sedum inoculated with endophytic bacteria is an excellent Phytoextraction Coupled with Agro-safe-production (PCA) pattern.

Integrated glycolysis and pyrolysis process for multiple utilization and cadmium collection of hyperaccumulator Sedum alfredii.

Phytoremediation is a cost-effective and environmentally-friendly method to treat cadmium (Cd) contaminated soils, however, there is still a lack of safe disposal methods of harvested hyperaccumulators. In this study, by integrating glycolysis and pyrolysis, we investigated the possibility of bioproduct production and Cd collection from the hyperaccumulator Sedum alfredii. By means of acid-alkali pretreatment, the degree of cellulose polymerization was reduced by 36.24% while the surface accessibility was increased by 115.80%, resulting in a bioethanol yield of 9.29%. Meanwhile, 99.22% of total Cd of biomass could be reclaimed by collecting H2SO4-pretreatment waste. The saccharification residue was subsequently modified by NaOH-pretreatment-filtrate and converted into biochar at 500 °C which possessed a maximum Cd2+ sorption capacity of 60.52 mg g-1 based on the Langmuir model. Furthermore, sustainability analysis indicated that the economic input of this process is acceptable when considering its good environmental benefits. Taken together, our study provides a strategy for simultaneous bioethanol and biochar production during Cd collection from the hyperaccumulator S. alfredii, which could be a promising alternative for the suitable treatment of metal-enriched plants.

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

Cadmium (Cd) is harmful to the environment and threatens human health. With the increasing use of cerium oxide nanoparticles (CeO2NPs) in extensive industries, investigating the combination of CeO2NPs and plants has attracted research interests for phytoremediation. Here, we explored the effects of CeO2NPs on Cd uptake, transport and the consequent Cd accumulation in Sedum alfredii. Exposure of 50 or 500 mg L-1 CeO2NPs alone had no apparent damaging effects on plant growth. However, upon Cd condition, the consistent CeO2NPs decreased Cd concentrations in the roots and shoots by up to 37%. Furthermore, the application of a metabolic inhibitor revealed that CeO2NPs mainly decreased the Cd uptake in roots by the apoplastic pathway. Simultaneously, CeO2NPs 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 CeO2NPs added alone, the concurrent Cd decreased the Ce contents in the roots and altered its translocation from root to shoot. Taken together, both CeO2NPs 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.

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

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.

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

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.

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

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.

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

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-1) 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-1 in monoculture and it increased to 51.2 mg kg-1 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.

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

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.

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

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-1 DW, respectively. Based on straw Cd accumulation, grain Cd concentration, and TFrs, 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.

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

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 13C 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 13C was incorporated into oxalic acid, malic acid, and tartaric acid in rhizosphere of S. alfredii after 13CO2 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 + CdCO3 had higher Cd contents and larger biomass than CdCO3 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.

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

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 > CeO2) 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.

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

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-1 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.

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

In situ remediation and assessment of sediments contaminated with both antibiotics and heavy metals remains a technological challenge. In this study, MgCl2-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 m2 g-1) than pristine biochar (BC, 7.1 m2 g-1). The SMX sorption data were well described by Freundlich model while Langmuir model was better for the Cd2+ 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 Cd2+, 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.

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

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.