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The levels of soils pollutants such as lead (Pb) and cadmium (Cd) have significantly increased recently resulting in ecological disturbances and threatening crop production. Various amendments have been employed to enhance the tolerance of crops to withstand Cd and Pb stresses. However, the role of combined application of potassium (K) and of salicylic acid (SA) for Cd and Pb stress mitigation and phytoremediation by quinoa (Chenopodium quinoa Willd) has not been comprehended well. In the present study, the effect of 10 mM K and 0.1 mM SA was tested on the quinoa plants subjected to 250 μM Pb and/or 100 μM Cd. The Pb and Cd treatments were applied separately or together. Phytotoxicity induced by Pb and Cd resulted in drastic decrease (>60%) in chlorophyll contents, stomatal conductance, and plant biomass. The collective treatment of Pb and Cd induced an increase in the concentration of hydrogen peroxide (13-fold) and lipid peroxidation (16-fold) that resulted in a 61% reduction in membrane stability. The application of 10 mM K and/or 0.1 mM SA was remarkable in mitigating the adverse effect of Pb and Cd. The reduction in plant biomass was 17% when 10 mM K and 0.1 mM SA were applied together under the combined treatment of both the metals. The simultaneous application of K and SA effectively mitigated oxidative stress by enhancing the activities of superoxide dismutase, peroxidase, ascorbate peroxidase, and catalase by 12, 10, 7 and 10-folds respectively. The positive effect of K and SA on these attributes resulted in a remarkable reduction in metal accumulation and translocation and lipid peroxidation. The stressed plants supplemented with K and SA exhibited a significant improvement in the membrane stability index, chlorophyll content, and stomatal conductance. This study concluded that the combined application of K and SA could be a good approach for reducing Pb and Cd phytotoxicity in quinoa and enhancing their phytostabilization potential in the contaminated soils., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)

Cadmium (Cd) and lead (Pb) are among the most toxic heavy metals affecting human health and crop yield. Suaeda maritima (L.) Dumort is an obligate halophyte that is well adapted to saline soil. The inbuilt salinity tolerance mechanisms of halophytes help them to survive in heavy metal-contaminated rhizospheric soil. In the present study, growth and ionomic responses, reactive oxygen species (ROS) accumulation, modulations of phytochelatins, antioxidative defense, and metabolomic responses were studied in S. maritima imposed to Cd and Pb stresses with an aim to elucidate Cd and Pb tolerance mechanisms and phytoremediation potential of this halophyte. Our results showed a reduction of biomass in S. maritima, which may serve as an energy conservation strategy for survival under heavy metal stress. The increased accumulation of ROS with concomitant higher expression of various antioxidative enzymes suggests the efficient scavenging of ROS. The metabolite profiling revealed significant up-regulation of sugars, sugar alcohols, amino acids, polyphenols, and organic acids under Cd and Pb stresses suggesting their possible role in osmotic balance, ionic homeostasis, ROS scavenging, and signal transduction for stress tolerance. In S. maritima, the translocation factors (Tf) are <1 in both Cd and Pb treatments, which indicates that this halophyte has high phytostabilization potential for Cd and Pb in roots and through restricted translocation of heavy metal ions to the aboveground part. The findings of this study offer comprehensive information on Cd and Pb tolerance mechanisms in S. maritima and suggest that this halophyte can detoxify the HMs through physiological, ionic, antioxidative, and metabolic regulations., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Masson SAS. All rights reserved.)

Camelthorn (Alhagi maurorum Medik) is a desert plant that can withstand a variety of abiotic challenges, including water stress and harsh weather, making it potentially useful for cleaning cadmium (Cd) from contaminated soils. The current study aims to determine the degree of plant tolerance to Cd toxicity and the possibility of using it in the phytoremediation of Cd-contaminated soils. Camelthorn plants were cultivated in soil polluted with Cd at doses of 0, 25, 50, 100, and 200 mg kg -1 . The growth, nutrient uptake, Cd concentrations, and some biochemical compounds were determined to study the response of camelthorn plants to Cd stress. Exposure of camelthorn plants to 200 mg kg -1 of Cd inhabited the synthesis of leaf-chlorophyll by 49% compared to the control and reduced the concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), iron (Fe), and zinc (Zn) by 43, 36, 43, 50, 67, and 36%, respectively. Camelthorn plants can tolerate up to 11 mg kg -1 of available soil Cd, 65 mg kg -1 in the root, and 22 mg kg -1 in the shoot before experiencing Cd toxicity. Camelthorn plants increased the levels of carbohydrates, total phenols, and proline compounds that were used in the scavenging of reactive oxygen species (ROS). Moreover, the plants increased the activity of antioxidant enzymes, i.e., superoxide dismutase (SOD) and peroxidase (POD), to mitigate the oxidative stress caused by Cd toxicity. The root-shoot transfer (TF) of Cd varied between 0.27 to 0.48, while the bioaccumulation factor (BAF) varied between 1.2 and 2.32. Camelthorn plants have a BAF value higher than 1 and a TF value lower than 1. Camelthorn plants accumulate Cd in the roots with low root-shoot transfer and are suitable for phytostabilization technology. Camelthorn plants have a potent antioxidant defense against the toxicity of Cd, and this finding is a good tool in the remediation of Cd-contaminated soil., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Miscanthus has good tolerance to heavy metals (HMs) and has received increasing attention in studies of HM-contaminated soil remediation. In this study, four Miscanthus cultivars (M. lutarioriparius Xiangnadi NO4, M. sinensis Xiangmang NO1, M. lutarioriparius × M. sinensis hybrid Xiangzamang NO1, and M. floridulus Wujiemang NO1) that grow in China were studied. Their tolerance and enrichment abilities in soils containing 50 mg kg -1 cadmium (Cd) and the structure and function of their rhizosphere bacterial communities during the remediation process were analyzed. The results exhibiting a tolerance index (TI) higher than 75 in roots and the aboveground parts (TI > 60, indicating highly tolerant plants) indicated that all four Miscanthus cultivars were tolerant to high Cd concentrations. Moreover, Cd was mainly enriched in roots, the translocation ability from roots to aboveground parts was weak, and the four cultivars exhibited phytostabilization ability in Cd-contaminated soils. High-throughput sequencing (HTS) analysis showed that the Miscanthus rhizosphere bacterial community comprised 33 phyla and 446 genera, including plant growth-promoting rhizobacteria (PGPRs), such as Bacillus, Sphingomonas, and Mesorhizobium. The addition of Cd affected the Miscanthus rhizosphere bacterial community and reduced community diversity. Phylogenetic molecular ecological networks (pMENs) indicated that Cd addition reduced interactions between Miscanthus rhizosphere bacteria and thereby led to a simpler network structure, increased the number of negative-correlation links, enhanced the competition between rhizosphere bacterial species, reduced the number of key bacteria, and changed the composition of those bacteria. PICRUSt functional predictive analysis indicated that Cd stress reduced soil bacterial functions in the Miscanthus rhizosphere. The results of this study provide a basis for the remediation of Cd-contaminated soils by Miscanthus and provide a reference for the subsequent regulation of Miscanthus remediation efficiency by PGPRs or key bacteria., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The herbal plant Salvia sclarea L. (clary sage) is classified to cadmium (Cd) accumulators and considered as a potential plant for phytoremediation of heavy metal polluted soil. However, the effect of Cd only treatment on the function of the photosynthetic apparatus of S. sclarea, as well as the mechanisms involved in Cd tolerance have not yet been studied in detail. This study was conducted to examine the integrative responses of S. sclarea plants exposed to a high Cd supply (100 µM) for 3 and 8 days by investigating element nutrient uptake, oxidative stress markers, pigment composition, photosynthetic performance and leaf structure. Measurements of the functional activities of photosystem I (PSI, by P700 photooxidation), photosystem II (PSII, by chlorophyll fluorescence parameters), the oxygen-evolving complex (oxygen evolution by Joliot- and Clark-type electrodes), as well as the leaf pigment and phenolic contents, were used to evaluate the protective mechanisms of the photosynthetic apparatus under Cd stress. Data suggested that the molecular mechanisms included in the photosynthetic tolerance to Cd toxicity involve strongly increased phenolic and anthocyanin contents, as well as an increased non-photochemical quenching and accelerated cyclic electron transport around PSI up to 61%, which protect the function of the photosynthetic apparatus under stress. Furthermore, the tolerance of S. sclarea to Cd stress is also associated with increased accumulation of Fe in leaves by 25%. All the above, clearly suggest that S. sclarea plants employ several different mechanisms to protect the function of the photosynthetic apparatus against Cd stress, which are discussed here., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

The environmental and health impacts caused by phosphogypsum (PG) make it necessary to carefully manage these wastes. Bioaugmentation of a PG-compost mix with Bacillus cereus was associated with Trifolium pratense or Helianthus annuus for the phytoextraction of metal trace elements (MTE). In hydroponics, MTE concentrations in sunflower shoots are higher than in clover; however, as opposed to clover, it regulates their accumulation. The MTE accumulation levels by plants cultivated in pots with the PG-compost mix are much lower than in hydroponics due to lower concentration in available MTE. The bacteria-plant coupling has served to raise MTE concentrations, especially for rare earth elements (REE), i.e., Ce, La, Nd, Y, in the AP of sunflower, by factors of 4.4, 38.3, 3.4 and 21, respectively, compared to non-bioaugmented control. The translocation factor was also increased for all MTE and is ranged between 1.1 for Sr and 6.8 for Y. Moreover, the presence of bacteria raises plant biomass by a factor of 3.7 for shoots and 2.9 for the roots as regards clover. Results showed that in addition to phytoextraction of REE elements, all providing the promise of some kind of economic opportunity, the dispersion of PG stockpiles dust and erosion should be reduced., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Phytoremediation is one of the most cost-effective and environmentally friendly ways to reduce adverse effects of cadmium (Cd) and lead (Pb) in the environment. The present study was conducted to investigate the bioaccumulation factor (BF) and translocation factor (TF) of Cd and Pb in muskweed (Myagrum perfoliatum) and foxtail sophora (Sophora alopecuroides). The impact of contamination on some growth responses of plants and soil biological indicators was also evaluated. A non-contaminated soil sample was divided into several subsamples: one subsample was left as control (without contamination) and the others were separately contaminated with three levels of Cd (3, 5, and 10 mg kg -1 ) and Pb (100, 300, and 600 mg kg -1 ). Pot experiments were performed under greenhouse conditions. The BF values of Cd were greater than 1 at all contamination levels indicating the potential of muskweed and foxtail sophora for the uptake and phytostabilization of Cd. The only TF > 1 was obtained for Cd in muskweed grown at the highest Cd contamination level. The TF values of Pb were much lower than those obtained for Cd indicating that Cd was more translocated from root to aerial parts of muskweed and foxtail sophora compared to Pb. The highest contamination levels of Cd and Pb did not significantly affect growth responses of muskweed and foxtail sophora. Furthermore, the cultivation of muskweed and foxtail sophora reduced the impact of Cd and Pb contamination on biological indicators including carbon mineralization ratio (CMR), substrate-induced respiration (SIR), microbial biomass carbon (MBC), and metabolic quotient (qCO 2 )., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Cadmium is a phytotoxic metal which threatens the global food safety owing to its higher retention rates and non-biodegradable nature. Optimal study of microbe-assisted bioremediation is a potential way to minimize the adversities of Cd on plants. Current study was aimed to isolate, identify and characterize Cd tolerant PGPBs from industrially contaminated soil and to evaluate the potential of plant-microbe synergy for the growth augmentation and Cd remediation. The Acinetobacter sp. SG-5, identified through 16S rRNA gene sequence analysis, was able to tolerate 1000 mg/l of applied Cd stress and ability of in vitro indole-3-acetic acid production, phosphate solubilization, as well as 1-aminocyclopropane-1-carboxylic acid deaminase activity. A Petri plate experiment was designed to investigate the impact of Acinetobacter sp. SG-5 on applied Cd toxicity (0, 6, 12, 18, 24, 30 μM) in maize cultivars (3062-Cd tolerant, 31P41-Cd susceptible). Results revealed that non-inoculated maize plants were drastically affected with applied Cd treatments for growth, antioxidants and mineral ions acquisition predominantly in susceptible cultivar (31P41). PGPB inoculation positively influenced the maize growth by enhanced anti-oxidative potential coupled with optimum level of nutrients (K, Ca, Mg, Zn). Analysis of morpho-physio-biochemical traits after PGPB application revealed that substantial Cd tolerance was acquired by susceptible cv. 31P41 than tolerant cv. 3062 under applied Cd regimes. Research outcomes may be important for understanding the growth responses of Cd susceptible and tolerant maize cultivars under Acinetobacter sp. SG-5 inoculation and likely to provide efficient approaches to reduce Cd retention in edible plant parts and/or Cd bioremediation., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

Marigold (Calendula calypso) is a multipurpose ornamental plant, but its cadmium (Cd) tolerance and phytoremediation potential is unknown. The proposed study was carried out to unravel Cd partitioning, physiological and oxidative stress responses of C. calypso grown under Cd stress. Plants were grown for four months in pots having different soil Cd levels: 0, 25, 50, 75, and 100 mg kg -1 soil. Plant growth, biomass, photosynthetic pigments, leaf water contents, stomatal conductance, and membrane stability index were not decreased at 25 mg kg -1 Cd. At higher levels of Cd stress, activities of antioxidant enzymes (SOD, APX, CAT, POD) increased to mitigate H 2 O 2 and lipid peroxidation. Cadmium uptake in plants increased with increasing soil Cd levels, and roots accumulated a greater portion of Cd, followed by shoots and flowers, respectively. On the basis of Cd accumulation and its tolerance, it was determined that C. calypso can be successfully grown for phytostabilization of Cd contaminated soils.

Phytoremediation has been employed as a cost-effective technique to remove the cadmium (Cd) from soil and water in several ecosystems. However, little is known about whether intercropping the remediating plants with rice (Oryza sativa) crop could reduce Cd accumulation in rice grains. We conducted greenhouse pot and concrete pond trials to explore the effects of intercropping alligator flag (Thalia dealbata, Marantaceae) on soil Cd remediation, paddy soil and microbial properties, and rice production. Our results suggest that intercropping with alligator flag significantly decreased Cd absorption, transportation, and accumulation from the soil to the rice grains (under 0.2 mg kg -1 at a soil Cd content below 2.50 mg kg -1 ). This decrease was due to the lowered Cd availability and higher soil pH in the rice-alligator flag intercropping system. Although planting alligator flag resulted in the reduction of soil NH 4 -N and NO 3 -N, Cd content in the rhizosphere was the main factor restricting microbial biomass, species, and community composition. Alligator flag could tolerate higher Cd contamination, and accumulate and stabilize more Cd in its tissues than rice. Our study suggests that alligator flag intercropped with rice has potential as a phytostabilization plant to produce rice safely for human consumption in moderately Cd-contaminated soils., (Copyright © 2020 Elsevier B.V. All rights reserved.)

In-situ remediation of heavy-metal-contaminated soil in farmland using phytostabilization combined with soil amendments is a low-cost and effective technology for soil pollution remediation. In this study, coconut shell biochar (CB, 0.1% and 0.5%), organic fertilizer (OF, 3.0%), and Fe-Si-Ca material (IS, 3.0%) were used to enhance the phytostabilization effect of ramie ( Boehmeria nivea L.) on Cd and Pb in highly polluted soils collected at Dabaoshan (DB) and Yangshuo (YS) mine sites. Results showed that simultaneous application of CB, OF, and IS amendments (0.1% CB + 3.0% OF + 3.0% IS and 0.5% CB + 3.0% OF + 3.0% IS, DB-T5 and DB-T6) could significantly increase soil pH, reduce the concentrations of CaCl 2 -extractable Cd and Pb, and increase the contents of Ca, P, S, and Si in DB soil. Under these two treatments, the growth of ramie was significantly improved, its photosynthesis was enhanced, and its levels of Cd and Pb were reduced, in comparison with the control (DB-CK). After applying DB-T5 and DB-T6, the concentrations of Cd and Pb in roots were decreased by 97.7-100% and 64.6-77.9%, while in shoots they were decreased by up to 100% and 92.9-100%, respectively. In YS-T4 (0.5% CB + 3.0% OF), the concentrations of Cd and Pb in roots were decreased by 39.5% and 46.0%, and in shoots they were decreased by 44.7% and 88.3%. We posit that phytostabilization using ramie and amendments could reduce the Cd and Pb bioavailability in the soil mainly through rhizosphere immobilization and plant absorption. In summary, this study suggests that the use of tolerant plant ramie and simultaneous application of coconut shell biochar, organic fertilizer, and Fe-Si-Ca materials is an effective stabilization strategy that can reduce Cd and Pb availabilities in soil. Ultimately, this strategy may reduce the exposure risk of crops to heavy metal pollution in farmland.

Phytostabilization aided by soil amendments has been advocated in areas contaminated by trace metals. In this study, the effects of indigenous weed (Setaria pumila), energy plant (Pennisetum sinese), cadmium (Cd)-hyperaccumulator (Sedum plumbizincicola), and copper (Cu)-tolerant plant (Elsholtzia splendens) on the bioavailability and mobility of Cu and Cd in polluted soil were evaluated after phytostabilization aided by limestone (0.1% wt) over four years. The four plants combined with limestone significantly increased soil pH and decreased Cu and Cd fractions extracted by NH 4 OAc and diffusive gradients in thin films (DGT) than the untreated soils, respectively. P. sinese treatments decreased DGT-extractable Cu and Cd by 52.1% and 40.5% than S. pumila treatments, respectively. S. plumbizincicola and E. splendens treatments increased acid-soluble fraction of Cu and decreased residual fraction of Cu compared with S. pumila treatments. P. sinese treatments had the lowest phytotoxicity (inhibitoryrates, superoxide dismutase, peroxidase and catalase activities) among all treatments. Moreover, EDTA kinetic extraction showed that S. plumbizincicola and E. splendens treatments increased the mobility of Cu and Cd by increasing labile and less labile fractions of Cu and Cd compared with P. sinese treatments. Present results suggest that P. sinese is recommended as the remediation plant for phytoremediation aided by amendments., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Cell wall acts as a major metal sink in plant roots, while a few studies focused on root cell wall binding in plants for the phytostabilization of multi-metal contaminated soils. A pot experiment was performed to characterize root cell wall properties of the mining ecotype (ME) and non-mining ecotype (NME) of Athyrium wardii (Hook.) in response to Cd and Pb. The cell wall was found to be the major sink for Cd (41.3-54.3%) and Pb (71.4-73.8%) accumulation in roots of the ME when exposed to Cd and/or Pb. The ME showed more Cd and Pb accumulation in root cell walls when exposed to Cd and Pb simultaneously, compared with those exposed to single Cd or Pb as well as the NME, suggesting some modifications for cell walls. The uronic acid contents of pectin and hemicellulose 1 (HC1) in root cell walls of the ME increased significantly when exposed to Cd and Pb simultaneously, suggesting enhanced cell wall binding capacity, thus resulting in more Cd and Pb bound to pectin and HC1. In particular, pectin was found to be the predominant binding site for Cd and Pb. Greater pectin methylesterase activity along with a lower degree of methylesterification were observed in the cell walls of the ME when exposed to Cd and Pb simultaneously. Furthermore, the ME present more O-H, N-H, C-OH, C-O-C, C-C and/or Ar-H in root cell walls when exposed to Cd and Pb simultaneously. These changes of root cell wall properties of the ME lead to enhanced cell wall binding ability in response to the co-contamination of Cd and Pb, thus could be considered a key process for enhanced Cd and Pb accumulation in roots of the ME when exposed to Cd and Pb simultaneously., Competing Interests: Declaration of competing interest The authors declare no conflict of interests., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Contamination of soil with salinity and Cd negatively affects growth and productivity of plants. The proposed study has been planned to explore the effects of salinity on Cd uptake, tolerance and phytoremediation potential of conocarpus (Conocarpus erectus L.). One-month-old uniform plants of conocarpus were exposed to 0, 8.9, 44.5, 89 and 178 µM Cd alone or in combination with 0, 100 and 200 mM NaCl in Hoagland's nutrient solution. Results revealed that shoot and root biomasses, leaf water content and pigment content decreased more in response to combination of Cd and salinity compared to Cd alone. The Na + and Cl - concentrations in shoot and root were not affected by Cd alone, but increased in Cd + salinity treatments. The K + concentration decreased by Cd alone as well as Cd combination with salinity. Plant Cd uptake increased in the presence of salinity but its translocation from root to shoot remained unaffected. Exposure of plants to Cd alone and Cd + salinity caused oxidative stress via overproduction of H 2 O 2 and inducing lipid peroxidation. The activities of antioxidant enzymes such as SOD, CAT, POD and APX increased to mitigate this oxidative stress. It is concluded that the tolerance of conocarpus against Cd stress is decreased in the presence of salinity due to increased uptake of toxic ions and intensification of oxidative stress. Moreover, the Cd uptake behavior of this tree indicates its suitability for phytostabilization of Cd contaminated saline and non-saline soils., (Copyright © 2018 Elsevier Inc. All rights reserved.)

The synergistic effects of arbuscular mycorrhizal fungi (AMF) inoculation and biochar application on plant growth and heavy metal uptake remain unclear. A pot experiment was carried out to investigate the influence of AMF inoculation, biochar and cadmium (Cd) addition on the growth, nutrient and cadmium uptake of Medicago sativa, as well as soil biological and chemical characteristics. In comparison to the non-Cd pollution treatment, Cd addition significantly decreased mycorrhizal colonization, biomass, and N, P, Ca and Mg contents of shoots and roots in the absence of biochar. Biochar amendment did not increase mycorrhizal colonization at either Cd levels. Regardless of the biochar amendment, AMF inoculation significantly promoted contents of N and P in plant shoots grown in the Cd-contaminated soils. Nevertheless, in the presence of Cd pollution, biochar dramatically elevated the biomass and N, P, K and Ca contents of plant tissues in both AMF inoculation treatments. Biochar addition significantly reduced soil DTPA-extracted Cd. The treatments with AMF inoculation and biochar amendment showed the lowest shoot Cd concentrations and contents, highest plant tissue N and P contents in the Cd addition group. These results suggested that combined use of AMF inoculation and biochar amendment had significant synergistic effects not only on nutrient uptake but also on the reduction in cadmium uptake of alfalfa grown in Cd-polluted soil., (Copyright © 2018 Elsevier B.V. All rights reserved.)

In recent years, ornamental plants have come under investigation as phytoremediation agents. In addition to reducing contaminant concentrations in soil, such plants support local economies by serving social (e.g., religious) and decorative purposes. Greenhouse studies investigated the phytostabilization potential of soil cadmium (Cd) by five cultivars of marigold (Tagetes erecta), a common ornamental flower in Asia. The effects of organic (cattle manure and pig manure) and inorganic (leonardite and Osmocote®) amendments in supporting plant growth and enhancing Cd uptake were also examined. Marigold cultivars Babuda and Sunshine grown in soil supplemented with pig manure produced the greatest biomass and experienced greatest Cd accumulation and flower production. In all treatments, plant parts accumulated Cd in the following order: root > shoot ≈ flower. Furthermore, Babuda and Sunshine cultivars had a high phytostabilization potential as evidenced by translocation factors < 1 and bioconcentration factors > 1 for roots. It is proposed that Babuda and Sunshine marigold cultivars be applied toward Cd phytostabilization while enhancing local economies as an ornamental species.

Artificial soil on railway rock-cut slopes may be considerably contaminated with cadmium (Cd) and lead (Pb), which may migrate to nearby croplands and pose substantial risks to human and animal health. We investigate the influence of three types of revegetation modes - herbs (HS); herbs and shrubs (HSS); and herbs, shrubs, and trees (HSTS) - on the transportation of these heavy metals in soils. Six representative rock-cut slopes were chosen, and the vegetation, pollutant concentration, phytostabilization, and simulated rainfall were investigated. The results indicated that Cd posed a considerable ecological risk, while Pb posed a low ecological risk in the artificial soil. The erosion of artificial soil on the slopes played a primary role in the migration of Cd and Pb, because 87-91% of Cd and 85-89% of Pb was lost in sediments. Revegetation modes significantly affected the transportation of Cd and Pb. HSTS controlled a lot of Cd in their dominant plants among the three revegetation modes. HSTS not only decreased enrichment factor (EF) and ecological risk (E r ) values of Cd in the soils, but also decreased runoff, sediment and cumulative migrated Cd and Pb. The relationships among multi-factors were analyzed by stepwise mediation effect test and the results indicated that root weight density, aboveground biomass and immobilization of dominant plants for Cd and Pb were important direct factors which influenced the transportation of Cd and Pb. Overall, HSTS has proven to be beneficial in controlling the migration of Cd and Pb to croplands near the slopes and reducing their environmental risk. These results can offer a tested and implementable solution for mitigating the risks posed by these pollutants around the quickly expanding railways in the study region., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Interactions between heavy metals in soil could affect soil heavy metal availability and plant uptake. Thus, in this study, Cd and Pb accumulation as well as plant growth of the mining ecotype (ME) and non-mining ecotype (NME) of Athyrium wardii (Hook.) in response to the exposure of Cd and Pb was investigated by a pot experiment. Although the exposure of Cd in combination with Pb further inhibited the growth of the two ecotypes in comparison with the exposure of single Cd or Pb, the ME presented lower biomass decline for the whole plant (22.0%-70.0%) than the NME among most treatments. The presence of Pb promoted Cd accumulation both in above-ground and under-ground parts of the ME. Cd concentrations in under-ground parts of the ME decreased when exposed to higher concentrations of Pb (> 600 mg kg -1 ). Meanwhile, the presence of Cd inhibited Pb accumulation in above-ground parts of the ME and promoted Pb accumulation in under-ground parts of the ME. Pb concentrations in under-ground parts of the ME decreased when soil Cd concentrations were more than 25 mg kg -1 . The partial correlation analysis further demonstrated that the interactions between Cd and Pb stimulated Cd accumulation both in above-ground and under-ground parts of the ME and Pb accumulation in under-ground parts of the ME, while inhibited Pb accumulation in above-ground parts of the ME, showing great benefit for Pb phytostabilization by the ME. Among treatments, the bioaccumulation coefficients for Cd and Pb of the ME, varying from 2.71-31.05 and 20.09-78.06, were much higher than those of the NME. The translocation factors for Cd and Pb of the ME, varying from 0.26-0.52 and 0.01-0.10, were lower than those of the NME. These results indicate that the ME presented greater potential for the phytostabilization of soil contamination with Cd and Pb, especially for Pb.

The effects of Cd stress on the growth and Cd accumulation of Bougainvillea spectabilis Willd. as an ornamental plant and the related mechanisms were investigated in the study. We studied the impact of Cd on the plant ultrastructure, examined the cellular distribution of Cd, explored the Cd chemical forms and transformation, and determined the organic acid secretion in the plants. The results showed that B. spectabilis could grow well in the Cd treatment groups, and the roots could accumulate high concentration of Cd. The soluble fraction (primarily in the vacuole) as the form of citrate in leaves of B. spectabilis was the major compartment for Cd storage. The citric acid secreted by B. spectabilis played an important role in the detoxification of Cd, as well as the growth of plants and Cd accumulation. As an ornamental plant, B. spectabilis has the potential to be used in the phytostabilization of Cd-contaminated soils and can beautify the environment at the same time.

Cadmium (Cd) may be toxic to aquatic plants even at modest concentrations, and excessive quantities of zinc (Zn) decrease plant performance. The Cd and Zn phytoremediation potential of several aquatic plant species (Thalia geniculate, Cyperus alternifolius, Canna indica, Eichhornia crassipes, Pistia stratiotes) and one grass species (Vetiveria zizanioides) was evaluated in hydroponic experiments. Vetiveria zizanioides, E. crassipes, and P. stratiotes experienced reduced growth performance in the presence of Cd as determined from biomass production, survival rate, and crown root number (CN); however, they accumulated high quantities of metals in their tissues, particularly in roots. Root accumulation is considered a key characteristic of so-called excluder species. In this study, only E. crassipes and P. stratiotes had bioconcentration factors and translocation factors (> 1000 and < 1, respectively) suitable for high phytostabilization of Cd. Furthermore, V. zizanioides and P. stratiotes showed the highest percent metal uptake from solution and removal capacity for Zn (~70% and ~2 mg d -1  g -1 , respectively). Emergent aquatic species (particularly C. alternifolius and T. geniculate) adapted and lived well in Cd- and Zn-contaminated solution and took up high quantities of Cd and Zn in roots, and are therefore considered strong excluders. Beneficial uses of such species in contaminated wetlands include stabilizing toxic metals and limiting erosion. Plant tissue can be applied to other uses, including as a biomass fuel. In field situations, the candidate species may work best when grown together, since each plant genotype possesses a different potential to control Cd and Zn.

In a greenhouse experiment, five ornamental plants, Osmanthus fragrans (OF), Ligustrum vicaryi L. (LV), Cinnamomum camphora (CC), Loropetalum chinense var. rubrum (LC), and Euonymus japonicas cv. Aureo-mar (EJ), were studied for the ability to phytostabilization for Cd-contaminated soil. The results showed that these five ornamental plants can grow normally when the soil Cd content is less than 24.6 mg·kg -1 . Cd was mainly deposited in the roots of OF, LV, LC and EJ which have grown in Cd-contaminated soils, and the maximum Cd contents reached 15.76, 19.09, 20.59 and 32.91 mg·kg -1 , respectively. For CC, Cd was mainly distributed in the shoots and the maximum Cd content in stems and leaves were 12.5 and 10.71 mg·kg -1 , however, the total amount of Cd in stems and leaves was similar with the other ornamental plants. The enzymatic activities in Cd-contaminated soil were benefited from the five tested ornamental plants remediation. Soil urease and sucrase activities were improved, while dehydrogenase activity was depressed. Meanwhile, the soil microbial community was slightly influenced when soil Cd content is less than 24.6 mg·kg -1 under five ornamental plants remediation. The results further suggested that ornamental plants could be promising candidates for phytostabilization of Cd-contaminated soil.

Plant growth promoting bacteria (PGPB) may help to reduce the toxicity of heavy metals on plants growing in polluted soils. In this work, Sulla coronaria inoculated with four Cd resistant bacteria (two Pseudomonas spp. and two Rhizobium sullae) were cultivated in hydroponic conditions treated by Cd; long time treatment 50 µM CdCl 2 for 30 days and short time treatment; 100 µM CdCl 2 for 7 days. Results showed that inoculation with Cd resistant PGPB enhanced plant biomass, thus shoot and root dry weights of control plants were enhanced by 148 and 35% respectively after 7 days. Co-inoculation of plants treated with 50 and 100 µM Cd increased plant biomasses as compared to Cd-treated and uninoculated plants. Cadmium treatment induced lipid peroxidation in plant tissues measured through MDA content in short 7 days 100 µM treatment. Antioxidant enzyme studies showed that inoculation of control plants enhanced APX, SOD and CAT activities after 30 days in shoots and SOD, APX, SOD, GPOX in roots. Application of 50 µM CdCl 2 stimulated all enzymes in shoots and decreased SOD and CAT activities in roots. Moreover, 100 µM of CdCl 2 increased SOD, APX, CAT and GPOX activities in shoots and increased significantly CAT activity in roots. Metal accumulation depended on Cd concentration, plant organ and time of treatment. Furthermore, the inoculation enhanced Cd uptake in roots by 20% in all treatments. The cultivation of this symbiosis in Cd contaminated soil or in heavy metal hydroponically treated medium, showed that inoculation improved plant biomass and increased Cd uptake especially in roots. Therefore, the present study established that co-inoculation of S. coronaria by a specific consortium of heavy metal resistant PGPB formed a symbiotic system useful for soil phytostabilization.

Heavy metal pollution in mangrove wetlands has become a growing matter of concern as it serves as sink and source for toxic heavy metals including cadmium (Cd). The present study evaluates the phytostabilization potential of a halophyte, Acanthus ilicifolius L., toward Cd under hydroponic culture conditions. Accumulation, translocation, and effects of Cd on the antioxidant system of A. ilicifolius were studied. Results indicated that A. ilicifolius accumulated Cd mainly in roots (96.4%) as compared to stem (1.4%) and leaves (0.6%) and the accumulated Cd is retained in root rather than being translocated to shoots as indicated by TF < 0.26. Moreover, malondialdehyde (MDA) content increased upon Cd treatment, which is further detoxified by the enzymatic and nonenzymatic antioxidant mechanism. Antioxidants like proline, ascorbate, and amino acid recorded an increased accumulation in the Cd-treated plants followed by the upregulation of antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (GPX), and ascorbate peroxidase (APX). Therefore, the rate of sugar accumulation was found to be decreased in plants treated with Cd as compared to the control plants. Thus, having relatively high BCF root (69.3) and low TF shoot (0.26) values, A. ilicifolius can be suggested as a potential candidate for phytostabilization of Cd in mangrove wetlands.

A hydroponic culture experiment was performed to investigate the effects of endophytic Bacillus megaterium H3 on the plant biomass, Cd accumulation and tolerance of hybrid pennisetum, and the mechanisms involved in the different levels of Cd-contaminated aquatic environments. Strain H3 significantly increased the plant growth (ranging from 13 to 71 %) and total Cd uptake (ranging from 41 to 160 %) but decreased Cd translocation factors of hybrid pennisetum treated with 0-20 μM Cd compared with the controls. Furthermore, most of Cd (71-77 %) was accumulated in the roots of the bacterial-inoculated hybrid pennisetum. Notably, strain H3 could significantly increase the production of oxalic and propanedioic acids (ranging from 18 to 188 %) but decrease the production of phytochelatins of hybrid pennisetum compared to the controls under different levels of Cd stress. The live bacterial-induced increase in organic acid production and decrease in phytochelatins production by hybrid pennisetum might be responsible for the increased plant growth, root Cd accumulation, and Cd toxicity alleviation of the plant under different levels of Cd stress. The results highlight that hybrid pennisetum plus endophytic B. megaterium H3 may be utilized for biomass production and Cd phytostabilization of the plant in the different levels of Cd-contaminated aquatic environments.

Soil contamination by cadmium (Cd) poses a serious environmental and public health concern. Phytoremediation, i.e., the use of plants to remove contaminants from soil, has been proposed for treatment of Cd-contaminated ecosystems. In this study, we demonstrated the potential of Vetiveria zizanioides, commonly known as vetiver, to serve as an effective phytoremediation agent. Two ecotypes, i.e., India and Sri Lanka, were grown in greenhouse pots and in the field. Soils were amended with cow manure, pig manure, bat manure, and an organic fertilizer. Among all amendments, pig manure performed best in both greenhouse and field studies in terms of increasing total V. zizanioides biomass production in both ecotypes. In both greenhouse and in the field, tissue of the Sri Lanka ecotype had higher Cd concentrations than did the India ecotype. In the greenhouse, the presence of Cd did not affect total biomass production or root dry weight. The Sri Lanka ecotype had 2.7 times greater adventitious root numbers and 3.6 times greater Cd accumulation in roots than did the India ecotype. In the field study, the Sri Lanka ecotype offers potential as an excluder species, as it accumulated Cd primarily in roots, with translocation factor values <1 and a bioconcentration coefficient for roots >1 for all experiments except for the pig manure amendment. In addition, the highest Cd concentration in the Sri Lanka ecotype root (71.3 mg kg(-1)) was consistent with highest Cd uptake (10.4 mg plant(-1)) in the cow manure treatment. The India ecotype contained lower root Cd concentrations, and Cd accumulation was slightly higher in shoots compared to roots, with translocation factor (TF) values >1. The India ecotype was therefore not considered as an excluder in the Cd-contaminated soil. With the use of excluder species combined with application of organic amendments, soil contamination by Cd may be treated by alternative remediation methods such as phytostabilization.

The application of organic amendments into heavy metal contaminated soil is considered as an environmentally friendly technique to promote the potential of phytoremediation. A pot experiment was carried out to evaluate the effect of humic substances on growth, cadmium (Cd) accumulation and phytostabilization potential of the mining ecotype (ME) and the corresponding non-mining ecotype (NME) of Athyrium wardii (Hook.) grown in Cd-contaminated soils. The addition of the humic substances demonstrated great promotion for the growth and Cd uptake of ME. Both plant biomass and Cd concentration significantly increased with the increasing application of the humic substances up to 100 g kg(-1), beyond which no significant change of underground part biomass and Cd concentrations in underground part of A. wardii was observed. The maximum Cd concentration in underground part of ME was 180 mg kg(-1) when 150 g kg(-1) humic substances were applied. The ME showed greater Cd accumulation capability in underground part (0.47-0.68 mg plant(-1)) than that of NME (0.27-0.45 mg plant(-1)). Increasing bioaccumulation coefficient (BCF) values of A. wardii was observed with increasing application of the humic substances. The BCF values of ME were higher than those of NME. However, the use of the humic substances exhibited little impact on translocation factors (TFs) of ME, and the TF values of ME were less than NME. Furthermore, the application of the humic substances improved the remediation factors (RFs) of A. wardii. The RF values in underground part of ME ranging from 0.73 to 0.91 % were apparently higher than those of NME. These results indicated that the humic substances can be a potential candidate for enhancing the phytostabilization of A. wardii grown in Cd-contaminated soils.

The synergistic activity between plants and microorganisms may contribute to the implementation of proactive management strategies in the stabilization of contaminated sites, although heavy metals, such as cadmium (Cd), are potentially toxic to them. The aim of this study was to evaluate the degree of tolerance to Cd contamination (supplying twice 40 mg kg(-1) of Cd) in poplar cuttings [clone I-214, P. × euramericana (Dode) Guinier] inoculated or not with two concentrations of Serratia marcescens strain (1 × 10(7) CFU/g and 2 × 10(7) CFU/g of potting mix). The response of the plant-bacteria system to excess Cd was investigated with special reference to the structural traits of plants and the functional efficiency of bacteria. Bacterial colonization and substrate components were previously assessed in order to define the best solution for formulating the experimental plant growth media. The tested plant-bacteria association, especially when bacteria were provided in double concentration, stimulated specific tolerance mechanisms to Cd through the promotion of the poplar growth. Inoculated plants produced larger leaves and increased stem diameter, while roots grew longer and wider in Cd-treated plants. The effect of bacterial inoculum on plant growth traits and metal partitioning in plant organs was assessed in order to define the potential of this poplar clone to be a suitable candidate for phytostabilization of Cd-contaminated soil. The final effect of the inoculation with bacteria, which alleviated the metal load and Cd phytotoxicity due to their bioaccumulation ability, suggests promising phytostabilization potential of these plant-bacteria associations.

Miscanthus sacchariflorus (Maxim.) Benth. is a metallophyte suitable for the phytoremediation of mine wastes. The tolerance and accumulation of M. sacchariflorus to cadmium was studied by pot experiments. The results showed that O2·- generation rate, plasma membrane permeability and MDA content of M. sacchariflorus leaves increased with increasing Cd concentrations in soil, but significant effect was only observed when Cd concentrations were ≥50 mg·kg(-1). SOD and POD activities increased initially but decreased later on, whereas CAT activity only increased significantly at higher Cd concentrations, 50-100 mg·kg(-1). The content of photosynthetic pigment and growth of M. sacchariflorus were both not significantly affected when Cd concentration was ≤25 mg·kg(-1). In contrast, both parameters were significantly affected when Cd concentration was ≥50 mg·kg(-1). M. sacchariflorus could accumulate much Cd, but most of the Cd assimilated was retained in the belowground part, suggesting that M. sacchariflorus has poor ability to translocate Cd to the aboveground part. Our results suggested that although M. sacchariflorus was not a hyper-accumulator, it has a strong capacity to tolerate and stabilize the Cd. Therefore, M. sacchariflorus has a certain potential in the phytostabilization of Cd-contaminated soils.

A finite element code was used for investigating the effect of some relevant characteristics of a phytoremediation project (crop type and density, presence of an irrigation system, soil capping and root depth). The evolution of the plume of contamination of Cd2+, Pb2+, and Zn2+ was simulated taking into account reactive transport and root processes. The plant contaminant uptake model was previously calibrated using data from greenhouse experiments. The simulations adopted pedological and climatological data representative of a sub-tropical environment. Although the results obtained were specific for the proposed scenario, it was observed that, for more mobile contaminants, poor water conditions favor stabilization but inhibit plant extraction. Otherwise an irrigation system that decreases crop water stress had an opposite effect. For less mobile contaminants, the remediation process did not have appreciable advantages. Despite its simplifying assumptions, particularly about contaminant sorption in the soil and plant system, the numerical analysis provided useful insight for the phytoextraction process important in view of field experiments.

Abstract\nNOVELTY STATEMENTHeavy metals and petroleum oil are the two most important contaminants in the environment. Currently, phytoremediation is regarded as an effective and affordable solution that allows the attenuation of toxic pollutants through the use of plants. Not many studies are carried out regarding the use of aromatic plants capable of remediating soil that is co-contaminated by heavy metal and petroleum hydrocarbons. A pot experiment was conducted to investigate the influence of cadmium-resistant PGPR Micrococcus luteus on the phytoremediation efficiency of Ocimum gratissimum in Cd and petroleum co-contaminated soil. The plants were harvested after 60 days of treatment and their growth and biomass were determined. The accumulation of Cd in plant shoots and roots was determined. The residual petroleum hydrocarbon concentration during the 60 days of the phytoremediation experiment was determined using GC-FID. O. gratissimum with M. luteus showed the highest Cd accumulation (14.05 mg kg−1) and the highest reduction of TPH (46.64%). M. luteus ameliorated contaminant toxicity and promoted biomass production of O. gratissimum. These results demonstrated that O. gratissimum in combination with M. luteus can be efficiently used to remediate Cd and petroleum-co-contaminated soils.The influence of cadmium-resistant PGPR, Micrococcus luteus, on the petroleum biodegradation efficiency of Ocimum gratissimum in Cd and petroleum-co-contaminated soil was found. M. luteus at the rhizosphere of O. gratissimum showed Cd-resistant capacity while reducing TPH at the highest removal efficiency within 60 days. [ABSTRACT FROM AUTHOR]

Human activities can cause enormous damage to agricultural soils through the accumulation of toxic metals in the soil. The identification of plants capable of accumulating relatively large amounts of these compounds in plant tissues with the aim of reducing or limiting soil toxicity is of great interest. Two independent pot experiments were conducted to evaluate the phytoremediation potential of different varieties of oat (Avena sativa L.) grown in soil contaminated with cadmium (Cd, 50 mg kg-1s soil). Eight varieties were cultivated for 21 days in Cd- contaminated soil. Five varieties of oat were exposed to Cd at the third leaf stage, followed one week later by exposure to oat powdery mildew (Blumeria graminis f. sp. avenae) for 35 days. In general, the tested varieties accumulated more Cd in the roots than in the shoots and showed a high tolerance to Cd. Metal accumulation in shoots was lower after 21 days of cultivation (8.30-17.27 mg Cd kg-1) than after 42 days (13.72-35.20 mg Cd kg-1) and was the highest in tissues of plants infected with B. graminis (48.17-96.20 mg kg-1). In conclusion, our results indicate a good phytostabilization and remediation potential of oat (varieties Racoon and Vaclav) for soil contaminated with cadmium. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) is one of the most common toxic heavy metal elements in soil pollution, which can be continuously enriched in the food chain and eventually threaten human health. Phytoremediation, which is using plants to transfer heavy metal elements from soils, is a promising solution for the remediation of heavy metal-contaminated soils. In this study, we evaluated whether Cunninghamia lanceolata (Lambert) Hooker (Chinese fir), a widely planted timber tree worldwide, had the potential to remediate Cd-contaminated soils through 90 days pot of experiments with different Cd concentration soils (0, 5, 10, 20, 50, 100 mg kg−1). C. lanceolata did not show obvious toxic symptoms in Cd-contaminated soils, although Cd inhibited plant growth and decreased net photosynthetic rate slightly. The activities of antioxidant enzymes increased significantly under Cd stress, indicating that C. lanceolata had a strong self-regulation ability and can tolerate Cd stress. The Cd bioconcentration factor (Cd concentration in plant divided by Cd concentration in soil) of C. lanceolata were greater than 1 at all Cd concentrations, indicating that C. lanceolata had a strong ability to absorb Cd, although Cd was mainly accumulated in roots. Our results indicated that C. lanceolata had a strong tolerance and phytostabilization ability of Cd. Considering the wide distribution worldwide, large biomass, and rapid growth of C. lanceolata, it could be a promising candidate for phytoremediation of Cd-contaminated soils. [ABSTRACT FROM AUTHOR]

Parsley is known in Lebanese diet for its nutraceutical properties and health benefits. However, the rising heavy metal contamination in irrigation water and agricultural soil affects crop production and safety. This study aims to assess parsley consumption in Lebanese population using a web-based food frequency survey, to measure cadmium accumulation and its effect on the physiology of parsley. Parsley was grown in soil for 9 weeks and exposed to different CdCl2 concentrations (0, 0.5, 2, 20, and 200 ppm). After harvesting, chlorophyll, sugar, and amino acid contents in parsley leaves were evaluated, and cadmium content was measured in soil, root, and shoot using inductively coupled plasma mass spectrometry. Estimated average daily consumption of parsley was 19.175 g/day. Cadmium content in parsley increased with increased cadmium soil concentration with higher increase in roots (47.648 ± 1.6 mg/kg) than shoots (1.522 ± 0.01 mg/kg) in the soil treated with 200 mg/kg of CdCl2. The study revealed that cadmium causes significant decrease in total fresh and shoot fresh weights and in chlorophylls a, b, and total chlorophyll. Cadmium-treated plants showed a significant increase in total sugar and amino acid contents suggesting the induction of a potential stress on the plant. Values of the bioconcentration factor and the translocation factor in parsley indicate the plant's capacity to accumulate cadmium. The target hazard quotient had a value < 1 suggesting plant cadmium remediation through phytostabilization, concentrating the metal in roots. Potentially, parsley remains safe for consumption with low risk to human health when grown in cadmium-polluted soils. [ABSTRACT FROM AUTHOR]

Green remediation of severely contaminated soils around mining sites can be achieved using suitable woody plants such as Quercus species, but their phytoremediation potential has not been well evaluated yet. Six Quercus species, which were popular in ecological restoration and landscape application in east China, were selected and evaluated for their phytoremediation potential of metal polluted soil using a pot experiment that lasted for 150 d. The results suggested that Quercus species exhibited high tolerance to multi-metal contamination of Cu (9839 mg · kg−1), Cd (8.5 mg · kg−1), and Zn (562 mg · kg−1) with a tolerance index (TI) ranging from 0.52 to 1.21. Three Quercus (Q. pagoda, Q. acutissima, and Q. nuttallii) showed relatively higher tolerance with TIs of 1.08, 1.09, and 1.21, respectively. Above-ground tissues accounted for most of the total biomass in T1 (mixture of clean and polluted soil, 50%) and T2 (100% polluted soil) treatments for most species. The Cu contents in plant tissues were in the order of root > leaf > stem, whereas Zn exhibited the order of leaf > stem > root, and Cd showed divergent mobility within the Quercus species. All the Quercus species exhibited higher capacity for Zn phytoextraction with translocation factor (TF) over 1 and Cu/Cd phytostabilization with TFs lower than 1. The analytic hierarchy process-entropy weight model indicated that Q. virginiana and Q. acutissima were two excellent species with evident phytoremediation capacity of Cu, Cd, and Zn co-contaminated soil. Taken together, Quercus species showed great potential for phytoremediation of soils severely polluted by Cu, Cd, and Zn around historic mining sites. Application of Quercus species is a green remediation option with low-maintenance cost and prospective economic benefit for phytomanagement of historic mining sites. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) contamination and soil salinity are the main environmental issues reducing crop productivity. This study aimed to examine the combined effects of salinity (NaCl) and Cd on the physiological and biochemical attributes of quinoa (Chenopodium quinoa Willd.). For this purpose, 30-day-old plants of quinoa genotype "Puno" were transplanted in Hoagland's nutrient solution containing diverse concentrations of Cd: 0, 50, 100, 200 µM Cd, and salinity: 0, 150, and 300 mM NaCl. Results demonstrated that plant growth, stomatal conductance, and pigment contents were significantly lower at all Cd concentrations than the control plants. Quinoa plants exhibited improved growth and tolerance against Cd when grown at a lower level of salinity (150 mM NaCl) combined with Cd. In contrast, the elevated concentration of salinity (300 mM NaCl) combined with Cd reduced shoot and root growth of experimental plants more than 50%. Combined application of salinity and Cd increased Na (25-fold), while lessened the Cd (twofold) and K (1.5-fold) uptake. A blend of high concentrations of Na and Cd caused overproduction of H2O2 (eightfold higher than control) contents and triggered lipid peroxidation. The activities of antioxidant enzymes: ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) were 13, 12, 7 and ninefold higher than control to mitigate the oxidative stress. Due to restricted root to shoot translocation, and greater tolerance potential against Cd, the quinoa genotype, Puno, is suitable for phytostabilization of Cd in saline soils. [ABSTRACT FROM AUTHOR]

An anatomical study of adventitious roots of three Salix clones, ‘B-44’, ‘SV068’ and ‘SM4041’, treated with 3 and 6 mg Cd kg-1 dry weight in soil was performed in a greenhouse experiment. The aim was to analyze the anatomical characteristics of roots in response to pollution by cadmium and to assess the potential application of anatomical and hydraulic characteristics in the selection of the most suitable Salix clones for phytostabilization of pollutants in soils. Anatomical parameters measured in this study included root cross-sectional area, root diameter, the proportion of periderm, secondary phloem (cortex) and wood (secondary and primary xylem), and parameters of the vessels (lumen area, diameter and frequency). Based on the measurements of individual vessel lumens and the number of vessels, the theoretical hydraulic conductivity (kh) of roots was calculated. The effects of applied Cd concentrations on root traits were studied in clones and control plants. Following treatments with both Cd concentrations, plants of clone ‘B-44’ had the highest values of most parameters and significantly higher kh in comparison with control samples due to the significantly larger root cross-sectional area and lumen area of vessels. It was concluded that these characteristics can serve for effective evaluation and selection of studied clones for remediation of sites contaminated with cadmium.

Abandoned lead and zinc (Pb/Zn) mining wastes represent a serious environmental hazard because heavy metals (e.g., Pb and Cd) are continuously released into the environment, threatening ecological and human health. This study was devoted to investigate the stability of Pb and Cd in the soil at an abandoned Pb/Zn mine site after landscape restoration by five-year monitoring. Chemical extraction was applied to measure the distribution of metals. The results showed that the bioavailability of Pb and Cd in soil increased, during the accumulation of soil organic matter of about seven g/kg, and that the soil pH value decreased from 4.82 to 4.44. Soil organic matter and soil pH significantly affected the distribution of metals. Long-term afforestation can lead to continuous soil acidification. There was a significant negative correlation between the carbonate-bound state distribution and soil pH. With the decrease in pH, the decomposition of carbonates was promoted, and relative abundances of Pb and Cd in the distribution associated with the fulvic and humic complex of organic matter increased by 0.54% and 3.17%, respectively. Pb and Cd showed different migration behavior in pine. Compared with Cd, Pb was more concentrated in roots. These results have important implications for the long-term sustainable management of forests formed by the phytostabilization of contaminated soil.

An anatomical study of adventitious roots of three Salix clones, 'B-44', 'SV068' and 'SM4041', treated with 3 and 6 mg Cd kg-1 dry weight in soil was performed in a greenhouse experiment. The aim was to analyze the anatomical characteristics of roots in response to pollution by cadmium and to assess the potential application of anatomical and hydraulic characteristics in the selection of the most suitable Salix clones for phytostabilization of pollutants in soils. Anatomical parameters measured in this study included root cross-sectional area, root diameter, the proportion of periderm, secondary phloem (cortex) and wood (secondary and primary xylem), and parameters of the vessels (lumen area, diameter and frequency). Based on the measurements of individual vessel lumens and the number of vessels, the theoretical hydraulic conductivity (kh) of roots was calculated. The effects of applied Cd concentrations on root traits were studied in clones and control plants. Following treatments with both Cd concentrations, plants of clone 'B-44' had the highest values of most parameters and significantly higher kh in comparison with control samples due to the significantly larger root cross-sectional area and lumen area of vessels. It was concluded that these characteristics can serve for effective evaluation and selection of studied clones for remediation of sites contaminated with cadmium. [ABSTRACT FROM AUTHOR]

A hydroponic experiment in NaCl tolerant mangrove, Bruguiera cylindrica plantlets was done to investigate the interactive effects of CdCl2+NaCl as well as the individual effects of CdCl2. CdCl2 alone results in enhanced level of cell membrane lipid peroxidation, damaging normal structure, and function of the membrane and there by leading to reduction of membrane stability index and thus severely promoting the electrolyte leakage than the combined treatment of CdCl2+NaCl. Antioxidants greatly contribute to cope with the stress by scavenging ROS and were more prominent in individual stress than combined stress. B. cylindrica can be categorized as a highly tolerant mangrove species with a Tolerance Index (TI) of above 60% toward CdCl2+NaCl (TI is 70 and 75% in leaf and root). But TI was only 63 and 67% in leaf and root, respectively, on exposure to CdCl2 alone indicating that this plant is less tolerant to Cd alone. The existence of B. cylindrica depends on the heavy metals being introduced into the mangrove ecosystem and imparts a combination stress along with NaCl. In this regard, B. cylindrica survives up to 0.20 mM CdCl2 along with NaCl. Thus, the high NaCl tolerance mechanisms in this mangrove species could be equally efficient in imparting tolerance toward high concentration of Cd along with NaCl and exhibits phytostabilization in polluted coastal wetlands. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) and lead (Pb) contaminated soils have increased recently, resulting in limited crop productivity. The ameliorative role of potassium (K) and silicon (Si) is well established in plants under heavy metals stress; however, their combined role under the co-contamination of Cd and Pb is not well understood. We hypothesized that the synergistic application of K and Si would be more effective than their sole treatment for increasing the Pb and Cd tolerance and phytostabilization potential of quinoa (Chenopodium quinoa Willd.). In the current study, quinoa genotype 'Puno' was exposed to different concentrations of Cd (0, 200 µM), Pb (0, 500 µM) and their combination with or without 10 mM K and 1.0 mM Si supplementation. The results revealed that the combined stress of Cd and Pb was more detrimental than their separate application to plant biomass (66% less than the control), chlorophyll content and stomatal conductance. Higher accumulation of Pb and Cd led to a limited uptake of K and Si in quinoa plants. The supplementation of metal-stressed plants with 10 mM K and 1.0 mM Si, particularly in combination, caused a significant increase in the growth, stomatal conductance and pigment content of plants. The combined stress of Cd and Pb resulted in an overproduction of H2O2 (11-fold) and TBARS (13-fold) and a decrease in membrane stability (59%). Oxidative stress induced by metals was lessened by 8-fold, 9-fold, 7-fold and 11-fold increases in SOD, CAT, APX and POD activities, respectively, under the combined application of K and Si. It is concluded that the exogenous supply of K and Si in combination is very promising for increasing Cd and Pb tolerance and the phytostabilization potential of quinoa. [ABSTRACT FROM AUTHOR]

The remediation of potentially toxic element-polluted soils can be accomplished through the use of microbial and plant-assisted bioremediation. A total of 32 bacteria were isolated from soil samples contaminated with potentially toxic elements. The isolated bacterial strain DG-20 showed high tolerance to cadmium (up to 18 mM) and also showed bioaccumulative Cd removal properties, as demonstrated by atomic absorption spectroscopy studies. By sequencing the 16S rRNA gene, this strain was identified as Curtobacterium oceanosedimentum. Under stress and normal conditions, isolate DG-20 also produced a wide range of plant growth promoting traits, including ammonia production (51–73 µg/mL) and IAA production (116–183 µg/mL), alongside siderophore production and phosphate solubilization. Additionally, pot experiments were conducted to determine whether the strain could promote Chili growth when Cd salts are present. Over the control, bacterial colonization increased root and shoot lengths significantly up to 58% and 60%, respectively. Following inoculation with the Cd-tolerant strain, the plants also increased in both fresh and dry weight. In both the control and inoculated plants, Cd was accumulated more in roots than in shoots, indicating that Chili was phytostabilizing Cd levels. Besides improving the plant attributes, Cd-tolerant bacteria were also found to increase the amount of total chlorophyll, proline, total phenol, and ascorbic acid in the soil when added to the soil. These results suggest that the inoculant provides protection to plants from negative effects. The results of the present study predict that the combined properties of the tested strain in terms of Cd tolerance and plant growth promotion can be exploited for the purpose of the bioremediation of Cd, and for the improvement of Chili cultivation in soils contaminated with Cd. [ABSTRACT FROM AUTHOR]

Pennisetum grasses (P. purpureum Schumach. 'Purple', P. alopecuroides (L.) Spreng. 'Liren' and P. alopecuroides (L.) Spreng. 'Changsui'), and a cadmium (Cd) hyperaccumulator (Thlaspi caerulescens J.Presl & C.Presl), were grown in soil with four Cd addition levels of 0, 2, 20 and 200 mg/kg. Toxicity symptoms were not observed although growth of all plants decreased as Cd addition increased. Shoot bioconcentration factor (BCFS), the translocation factor (TF) and shoot accumulation of Cd for most plants first increased and then declined as Cd concentrations increased. In contrast, the root bioconcentration factor (BCFR) for T. caerulescens declined and root Cd accumulation for T. caerulescens and two P. alopecuroides cultivars increased consistently as Cd levels increased. P. purpureum had the largest biomass with shoot Cd accumulation similar to that of T. caerulescens, despite lower foliar Cd concentration. Although shoot Cd concentrations of two P. alopecuroides cultivars were lower than for P. purpureum, root Cd concentrations were greater. P. purpureum had Cd BCFS and TF (> 1) at 2- and 20-mg/kg Cd addition treatments, similar to T. caerulescens. P. alopecuroides cultivars had Cd BCFR (> 1) and TF (< 1) at all Cd levels. Roots did not affect rhizosphere pH. However, concentrations of acid extractable Cd in rhizosphere soil were lower than those of corresponding non-rhizosphere soil at all Cd levels for T. caerulescens and P. purpureum; T. caerulescens and P. purpureum did not affect less bioavailable Cd fractions. Concentrations of acid extractable Cd in the rhizosphere of the P. alopecuroides cultivars were not reduced at any Cd level. Differences in Cd accumulation among the three Pennisetum grasses were mainly attributable to root biomass and Cd TFs rather than rhizosphere Cd mobility. [ABSTRACT FROM AUTHOR]

Phytoremediation techniques to clean heavy metal pollution soil depend on identifying plant species that can act as phytoremediators. One important approach to screening potential phytoremediators is to evaluate characteristics of heavy metal accumulation. In this study, we performed firsthand analysis of Cd tolerance and accumulation characteristics of three Sansevieria trifasciata cultivars by pot experiment. Plant growth results showed that all three S. trifasciata cultivars can tolerate 50 mg kg−1 soil Cd concentration. After growth under 50 mg kg−1 soil Cd concentration for 4 months, the Cd bioconcentration factors in the shoots of S. ‘Trifasciata’, S. trifasciata ‘Laurentii’, and S. trifasciata ‘Silver Hahnii’ were 1.26, 1.30, and 1.19, while those in the roots were 12.53, 11.43, and 5.45, respectively. This result reveals the considerably low translocation factors of 0.10, 0.12, and 0.22 for S. ‘Trifasciata’, S. trifasciata ‘Laurentii’, and S. trifasciata ‘Silver Hahnii’, respectively. These results suggest that all three S. trifasciata cultivars had high Cd absorption capacities but low Cd translocation capacities. In combination with total Cd accumulation distribution and plant growth characteristics, S. trifasciata can be designed as a phytostabilizer in Cd-contaminated soils in its cultivation regions. Meanwhile, the mechanism of high Cd tolerance and accumulation characteristics in the roots of S. trifasciata should be explored. This study provides new resources for dealing with Cd-contaminated soils and exploring Cd tolerance and accumulation mechanisms in plants.

The aim of the present research was to determine the accumulation, distribution and tolerance of sunflower plants to cadmium (Cd) contaminated soils. The research consisted of two pot experiments under greenhouse conditions. In Experiment 1, concentrations of 0, 10, 15, 20, and 25 mg Cd kg-1 soil were tested and the height, dry matter production and Cd concentration in root, stem, leaf, and inflorescence were evaluated at 84 DAS (day after sowing). In Experiment 2, the concentration was 20 mg Cd kg-1 soil and the concentration of Cd in the same organs was evaluated at 35, 49, 63, 75, and 84 DAS. Cadmium doses had no effect on plant height or dry matter production, the tolerance index (TI) being equivalent to 1, which demonstrated its high tolerance for this metal. In general, it was found that increasing doses of Cd in the soil increased Cd concentration in the plant. Independent of the time of evaluation, the root concentrated more Cd due to a low translocation towards the aerial zone. The bioconcentration factor (BCF) was greater than 1 under the different doses of Cd. As for the translocation factor (TF), it was less than 1 in both experiments. According to the TF and BCF values found, sunflower would behave as a phytostabilizer below 25 mg Cd kg-1 soil. [ABSTRACT FROM AUTHOR]

Soils contaminated by potentially toxic elements (PTEs) as a result of anthropogenic activities such as mining are a problem due to the adverse effects on human and environmental health, making it necessary to seek sustainable strategies to remediate contaminated areas. The objective of this study was to evaluate the species Clidemia sericea D. Don for the phytoremediation of soils contaminated with PTEs (Hg, Pb, and Cd) from gold mining activities. The study was conducted for three months, with soils from a gold mining area in northern Colombia, and seeds of C. sericea, under a completely randomized experimental design with one factor (concentration of PTEs in soil) and four levels (control (T0), low (T1), medium (T2), and high (T3)), each treatment in triplicate, for a total of twelve experimental units. Phytotoxic effects on plants, bioconcentration (BCF), and translocation (TF) factors were determined. The results obtained for the tissues differed in order of metal accumulation, with the root showing the highest concentration of metals. The highest values of bioconcentration (BCF > 1) were presented for Hg at T3 and Cd in the four treatments; and of translocation (TF > 1) for Hg and Pb at T0 and T1; however, for Pb, the TF indicates that it is transferable, but it is not considered for phytoextraction. Thus, C. sericea demonstrated its potential as a phytostabilizer of Hg and Cd in mining soils, strengthening as a wild species with results of resistance to the stress of the PTEs evaluated, presenting similar behavior and little phytotoxic affectation on the growth and development of each of the plants in the different treatments.

Willow species (Salix L.) are a useful tool for assessing phytostabilization of the sites polluted by heavy metals. Phytostabilization potential of two willow genotypes (Salix alba L. clone '68/53/1' and Salix nigra Marshall clone '0408') has been evaluated in a 45-day hydroponic experiment, using stem cuttings (diameter 12 to 14 mm, length 20 cm) exposed to two concentrations (10−4 M and 10−5 M) of individually applied Cd, Ni, and Pb. Metals were diluted in 25% Hoagland's solution, in forms of CdCl2·H2O, NiSO4·6H2O, and Pb-EDTA. The control group of cuttings was grown in 25% Hoagland's solution without heavy metals. High Cd concentrations in willow roots, 8637 mg/kg (clone '68/53/1') and 6728 mg/kg of dry weight (clone '0408'), have indicated a high phytostabilization potential. However, detailed analyses of cross-sectional area of the root cortex and the central cylinder revealed that the excess concentration of Cd led to a significant reduction of measured anatomical rootʼs traits of clone '68/53/1' in comparison with the control samples. Excessive concentration of Ni and Pb in nutrient solution increased the values of quantitatively measured rootʼs traits of clone '0408', implying stimulatory effects of the applied concentrations. Concentration of 10−4 M of each metal had more negative effects on the rootsʼ anatomical traits, notably on parenchymal and exodermal cells and vessels. Deposits of metals were observed in root tissues. Clone '0408' demonstrated an increased tolerance to heavy metals, which could potentially make this clone useful in phytostabilization. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the effects of cadmium (Cd) toxicity on accumulation, growth, physiological responses, and biochemical characters in summer savory (Satureja hortensis L.). Plants were subjected to different levels of Cd concentrations including 0 (control), 2.5, 5, and 15 mg L−1 in the growing medium. Cd exposure led to a significant increase in root and shoot Cd content. Calculation of bioaccumulation factor, translocation factor, and transfer coefficient revealed that Cd mostly accumulated in roots of S. hortensis and root to shoot transport was effectively restricted. Cd toxicity negatively affected plant growth and significantly reduced chlorophyll content. Contrarily, proline, soluble and reducing carbohydrates, anthocyanin content, and the activity of antioxidant enzymes significantly increased as a result of Cd exposure. Cd application led to a significant increase in essential oil content of S. hortensis. GC-MS analysis revealed that percentage main constitute of S. hortensi, carvacrol, which determines the quality of oil increased under the highest Cd treatment. Based on our findings, S. hortensis can be considered an invaluable alternative crop for mildly Cd-contaminated soils. Besides, due to the high potential of Cd accumulation in the root, S. hortensis may offer a feasible tool for phytostabilization purposes. [ABSTRACT FROM AUTHOR]

• Developing adventitious roots and aerenchyma of the flooded Salix genotypes was responsible for tolerance to both flooding and Cd stresses. • The non-flooded Salix genotypes displayed good Cd phytoextraction potentials, whereas the flooded genotypes showed Cd phytostabilization traits. • Flooding tended to decrease Cd phytoavailability. • Selecting Salix genotypes with high Cd accumulation and high tolerance to both flooding and Cd improved phytoremediation efficiency. The willow (Salix spp.) is a promising candidate coping with global climate warming and environment pollution. In this study, differences in plant growth, Cd uptake and accumulation, and extractable Cd in the rhizosphere between flooded and non-flooded (well-drained) Salix genotypes were investigated using a pot experiment in the rainshelt. All Salix genotypes grew well under well-drained conditions. In contrast, the flooded Salix genotypes developed hypertrophied lenticels, adventitious roots and aerenchyma, and decreased aboveground biomass production compared with the corresponding non-flooded genotypes, varying with genotypes and Cd levels in the medium. The non-flooded Salix genotypes had high Cd accumulation in aerial tissues with high leaf Cd bioconcentration factors (BCF) and translocation factors (TFs) relative to genotypes, displaying good Cd phytoextraction potentials. The flooded Salix genotypes dramatically decreased Cd accumulation in aerial tissues with low Cd BCFs and TFs, and large amounts of Cd accumulated in roots compared to the non-flooded genotypes, showing Cd phytostabilization traits. The extractable Cd in rhizosphere changed with genotypes and treatments, and comparatively, EDTA-extractable Cd could reflect well Cd phytoavailability to the willows in the soil. It was concluded that flooding tended to shift from phytoextraction to phytostabilization for Cd by willows during whole growing season. [ABSTRACT FROM AUTHOR]