Phytoremediation Purposes Research Articles

Exogenous Melatonin Enhances Cd Tolerance and Phytoremediation Efficiency by Ameliorating Cd-Induced Stress in Oilseed Crops: A Review

Heavy metal pollution is of increasing global concern as it adversely impacts different spheres including pedosphere, hydrosphere, biosphere, and humansphere. Cadmium (Cd) contamination of agriculture soil has become a thoughtful challenge across the globe due to uncontrolled anthropogenic activities, limiting agricultural productivity and disturbing eco-environment sustainability. Sustainable mitigation strategies are, therefore, required for effective Cd decontamination. Biostimulation is a promising method to improve and stimulate life processes of plants in general and oilseed crops in particular, without posing threats to eco-environment sustainability and safer food production. Melatonin (N-acetyl-5-methoxytryptamine), a recognized pleiotropic molecule, has emerged as a research highlight regarding its role as an effective natural plant growth promoter, a broad spectrum antioxidant, and more specifically an efficient biostimulator to improve Cd-induced tolerance of plants for phytoremediation purposes and simultaneous biofuel production. This review provides a novel insight to understand the multifunctional role of melatonin in improving Cd phytoremediation capacity together with reducing phytotoxicity in oilseed crops, which was not previously assessed. Among oilseed crops, Brassicaceae spp. have unique stress adaptive mechanisms with exceptionally high Cd accumulating capabilities, apart from the diverse agri-horticultural importance. Interestingly, the discovery of dynamic approaches regarding melatonin application helped to better understand the basic mechanisms involved in melatonin-mediated responses against Cd stress in oilseed crops. Our review will provide a useful basis for the development of alternative strategies to genetically engineer low-Cd-content oilseed crops, with the aim of improving eco-friendly crop production and ensuring food safety. Furthermore, future researches will be supposed to provide more genetic evidences about Cd-induced melatonin regulation in higher plants.

Lead phytoremediation potentials of four aquatic macrophytes under hydroponic cultivation

Lead (Pb) is a major toxicological concern of the present day that demands immediate attention. The use of aquatic macrophytes with high Pb tolerance and accumulation may be a very convenient and economically viable solution for remediating Pb. We examined the ability of Salvinia cucullata, Alternanthera sessilis, Lemna minor, and Pistia stratiotes to remove 0.12 mM, 0.24 mM, 0.36 mM, and 0.48 mM Pb for 96-h under hydroponic cultivation system. The plants accumulated variable amounts of Pb: S. cucullata > A. sessilis > P. stratiotes > L. minor, with low mobility of Pb from root to shoot. Lead uptake kinetics were monitored up to 96-h. After 96-h, the uptake efficiency for S. cucullata (98–99%), A. sessilis (79–96%), L. minor (45–79%), and P. stratiotes (40–76%) was noted. For S. cucullata and A. sessilis, an extremely high uptake rate was seen within the initial 24-h of trials, followed by slower uptake till 96-h. P. stratiotes and L. minor worked best at 0.12 mM Pb. Pb-Phytotoxicity became prominent at 0.48 mM exposure with biomass loss and morphological changes. The plants had a quick growth rate, extensive root system, high biomass yield, and the ability to tolerate and accumulate Pb that made them suitable for phytoremediation purposes. NOVELTY STATEMENT: Lead phytoremediation potential of four aquatic macrophytes found in Indian waters was evaluated. These macrophytes, often considered as weeds, could be used for phytoremediation purposes that would turn out to be a sustainable means of the utilization of natural resources in developing countries like India. In this study, not only metal accumulation by plants but also the lead uptake kinetics at several time intervals and valuable growth attributes were estimated to establish the suitability of these plants as probable lead phytoremediators. Two of the plant species, Salvinia cucullata, and Alternanthera sessilis, showed excellent Pb accumulation capacities that had not been reported earlier, to the best of our knowledge. The work is all the more significant as there have been needs for identifying Pb-phytoremediators well suited to native climate and growth conditions that could take up large amounts of metal from the substratum.

Evaluation of Furcraea foetida (L.)Haw. for phytoremediation of cadmium contaminated soils.

In the present study, we evaluated Furcraea foetida for the phytoremediation of cadmium (Cd)-contaminated soils. We selected F. foetida because it is a drought-resistant plant, produces high biomass, and needs minimum maintenance. It belongs to the leaf fiber group of plants and therefore has economic importance. Since it is a non-edible crop, there is no danger of food chain contamination. Despite possessing these ideal characteristics, surprisingly, to date, the plant is underutilized for phytoremediation purposes. Therefore, to evaluate the phytoremediation potential of the plant, we exposed it to five levels of cadmium (0, 25, 50, 100, and 200 mg Cd kg-1 soil) and studied its influence on growth, dry matter production, uptake, and translocation efficiency. The plant showed good tolerance to Cd 200 mg kg-1 soil without exhibiting any visible toxicity symptoms. The metal mainly accumulated in the roots (233 μg g-1dw), followed by leaf (51 μg g-1 dw). The bioconcentration factor was > 1, but the translocation factor was < 1. The plant was not classified as a hyperaccumulator of Cd; however, because of its high uptake (897 μ g-1 plant) and translocation efficiency (78%), we concluded that the plant could be utilized for phytoextraction of Cd from soils with low to moderately contaminated soils.

Trace Element Levels in Native Plant Species around the Industrial Site of Puchuncaví-Ventanas (Central Chile): Evaluation of the Phytoremediation Potential

The present work investigates the uptake of selected trace elements (Cu, Sb, As, Pb, Cd, Zn, Cr, Mn, Ni, V, and Co) from soil and their accumulation in the biomass samples (leaves and flowers) of three selected native plants (namely Oenothera picensis, OP; Sphaeralcea velutina, SV; and Argemone subfusiformis, AS) around an industrial area (Puchuncaví-Ventanas) located in the Puchuncaví valley, in the central region of Chile. Primary emission sources in the area come from a copper refinery, coal-fired power plants, and a set of 14 other different industrial facilities. Trace element measurements in the native plants of this area and the ability to transfer of these pollutants from soil to plants (transfer factor) have been assessed in order to identify the potential use of these plant species for phytoremediation. Preliminary results showed a high concentration of trace elements in the OP, SV, and AS samples. The concentration of these elements in the plants was found to be inversely correlated to the distance of the primary emission sources. Moreover, the high concentrations of trace elements such as Cu, As, Cr and V, upon the toxic limits in the native plant species, suggest the need for continuous monitoring of the region. The OP species was identified as the plant with the highest capacity for trace elements accumulation, which also showed higher accumulation potential in whole aerial parts than in leaves. Transfer factor values suggested that these native plants had phytoremediation potential for the elements Cu, Pb, As, Ni, and Cr. This study provides preliminary baseline information on the trace element compositions of important native plants and soil in the Puchuncaví-Ventanas area for phytoremediation purposes.

High-Affinity Sulfate Transporter Sultr1;2 Is a Major Transporter for Cr(VI) Uptake in Plants.

Chromate (Cr[VI]) is a highly phytotoxic contaminant that is ubiquitous in soils. However, how Cr(VI) is taken up by plant roots remains largely unknown. Here, we show that the high-affinity sulfate transporter Sultr1;2 is responsible for Cr(VI) uptake by the roots of Arabidopsis thaliana. Sultr1;2 showed a much higher transport activity for Cr(VI) than Sultr1;1 when expressed in yeast cells. Knockdown of Sultr1;2 expression in Arabidopsis markedly reduced the Cr(VI) uptake rate, whereas knockout of Sultr1;1 had no or little effect. A double-knockout mutant (DKO) of the two genes lost the ability of Cr(VI) uptake almost completely. The Sultr1;2 knockdown mutant or DKO plants displayed higher resistance to Cr(VI) under normal sulfate conditions as a consequence of the lower tissue Cr accumulation. Overexpression of Sultr1;2 substantially increased Cr(VI) uptake with shoot Cr concentration being 1.6-2.0 times higher than that in the wild-type. These results indicate that Sultr1;2 is a major transporter responsible for Cr(VI) uptake in Arabidopsis, while Sultr1;1 plays a negligible role. Taken together, our study has identified a major transporter for Cr(VI) uptake in plants, providing potential strategies for engineering plants with low Cr accumulation and consequently enhanced Cr(VI) resistance and also plants with enhanced accumulation of Cr for the purpose of phytoremediation.

Uptake, accumulation, and translocation of Zn, Cu, Pb, Cd, Ni, and Cr by P. australis seedlings in an urban dredged sediment mesocosm: Impact of seedling origin and initial trace metal content

The study presents results from 6 months of phytoremediation of sediments dredged from three urban retention tanks carried out in a mesocosm setup with the use of P. australis. Two kinds of P. australis seedlings were considered: seedlings originating from natural (uncontaminated - Suncont) and anthropogenically changed environments (contaminated – Scont); this distinction was reflected in the baseline concentrations of trace metals inside their tissues. The potentially toxic elements (PTEs) considered in this study were as follows: Zn, Cu, Cd, Ni, Cr, and Pb. The aim of the study was to compare the uptake, accumulation, and translocation properties of seedlings with different initial trace metal contents. The PTE concentrations were analyzed in sediments as well as in belowground and aboveground parts of plants in the middle (3rd month) and at the end of the investigation period using inductively coupled plasma mass spectrometry (ICP-MS), and the accumulation of PTEs in plant tissues was calculated. Phytoextraction efficiency was evaluated using the bioconcentration factor (BF) and translocation factor (TF). Plant morphology was assessed with scanning electron microscopy (SEM) to document plant stress due to PTE exposure. The results of our study indicated that P. australis seedlings originating from sites differing in the initial trace metal content exhibited different behavior when grown on sediments dredged from urban retention tanks. Suncont seedlings with low initial metal contents tended to adapt to the dredged sediments and showed phytoextraction ability, while Scont seedlings originating from sites with initial high contents of trace metals acted as phytoexcluders and tended to release PTEs from their tissues into the sediments. The morphological and structural effects caused by metal toxicity were observed in growth limitation, root tissue disturbance, root hair number decrease, and structural alterations in the epidermis and endodermis. Therefore, the Suncont seedlings presented better properties and adaptability for phytoremediation purposes.

Tolerance and phytoremediation potential of grass species native to South American grasslands to copper-contaminated soils

Grass species native to South American can have mechanisms to tolerate copper (Cu) excess, which improves their use to phytoremediate Cu-contaminated soils . The aims of the present study are to assess the tolerance of grass species native to South American grasslands to copper-contaminated soils, as well as their adaptive responses under high Cu-stressed condition and to identify native grass species presenting the highest potential to be used for phytoremediation purposes. Soil samples were air-dried and their acidity, phosphorus and potassium levels were corrected, and the samples were incubated. Three Cu levels were used in the experiment: natural (Dose 0), with added of 40 mg kg−1 of Cu and with added of 80 mg kg−1 of Cu. Three Axonopus affinis, Paspalum notatum and Paspalum plicatulum seedlings were transferred to 5-L pots filled with soil in August and grown for 121 days. Soil solution was collected during cultivation with the aid of Rhizon lysimeters. Main concentrations of cations and anions, dissolved organic carbon and pH in the soil solution were analyzed and the ionic speciation was carried out. Cu toxicity impaired the growth of grass species native to South America, since Cu excess led to both changes in root morphology and nutritional unbalance. Among all assessed native species, Paspalum plicatulum was the one presenting the greatest potential to phytostabilize in Cu-contaminated soils, since it mainly accumulates Cu absorbed in the roots; therefore, its intercropping with grapevines is can be beneficial in Cu-contaminated soils.

Heavy metal contents in soils and native flora inventory at mining environmental liabilities in the Peruvian Andes

Inadequate waste management in Mining Environmental Liabilities (MEL) represents a risk for the environment and human health and generates social problems. The aim of this article is twofold: i) to evaluate the environmental quality of soils from a geo-ecological perspective; and ii) to inventory native flora around two MEL in the Hualgayoc district in the Peruvian Andes. Soil samples collected for topsoil (upper 30 cm; i.e., soil arable layer) and subsoil (30–60 cm) were classified as Gleyic Cambisols and showed extremely acid pH (3.50–4.19 in site #1 and 2.74–4.02 in site #2). The mineralogical composition of soils is dominated by illite, kaolinite, quartz, and jarosite. The concentrations of six potentially toxic elements (Pb, Zn, As, Cu, Ag, and Cd) were determined. High concentrations of Pb (4683 mg kg−1), Zn (724.2 mg kg−1), Cu (511.6 mg kg−1), Ag (33.4 mg kg−1), and As (3611 mg kg−1) exceeded the maximum permissible limits for agricultural soils according to Peruvian and Canadian regulations. Applied geochemical indexes classified some of the soils as extremely polluted and therefore the studied MEL represent a very high ecological risk. Twenty-two species of native flora belonging to 12 family species were inventoried in such contaminated sites thus having the potential to be used for phytoremediation purposes.

Physiological and molecular mechanisms of metal accumulation in hyperaccumulator plants.

Most of the heavy metals (HMs), and metals/metalloids are released into the nature either by natural phenomenon or anthropogenic activities. Being sessile organisms, plants are constantly exposed to HMs in the environment. The metal non-hyperaccumulating plants are susceptible to excess metal concentrations. They tend to sequester metals in their root vacuoles by forming complexes with metal ligands, as a detoxification strategy. In contrast, the metal-hyperaccumulating plants have adaptive intrinsic regulatory mechanisms to hyperaccumulate or sequester excess amounts of HMs into their above-ground tissues rather than accumulating them in roots. They have unique abilities to successfully carry out normal physiological functions without showing any visible stress symptoms unlike metal non-hyperaccumulators. The unique abilities of accumulating excess metals in hyperaccumulators partly owes to constitutive overexpression of metal transporters and ability to quickly translocate HMs from root to shoot. Various metal ligands also play key roles in metal hyperaccumulating plants. These metal hyperaccumulating plants can be used in metal contaminated sites to clean-up soils. Exploiting the knowledge of natural populations of metal hyperaccumulators complemented with cutting-edge biotechnological tools can be useful in the future. The present review highlights the recent developments in physiological and molecular mechanisms of metal accumulation of hyperaccumulator plants in the lights of metal ligands and transporters. The contrasting mechanisms of metal accumulation between hyperaccumulators and non-hyperaccumulators are thoroughly compared. Moreover, uses of different metal hyperaccumulators for phytoremediation purposes are also discussed in detail.

Potential use of grapevine cv Askari for heavy metal phytoremediation purposes at greenhouse scale.

Grapevine varieties possess desirable characteristics for phytoremediation purposes. We investigated the potential of grapevine cv Askari in phytoremediation of heavy metal (HM) pollutions. In total 80 grapevine seedlings were exposed to four levels of HM stress (mild, low, moderate, and severe) in greenhouse condition during two growing years (2018 and 2019). The HM concentrations (Zn, Cu, Cd, Cr, and Pb) were subsequently determined in the soils, roots, and grapevine aboveground parts (AGPs), and then phytoextraction and phytostabilization potential assessment indices, i.e., biological absorption coefficient (BAC), bioconcentration factor (BCF), and translocation factor (TF), were calculated. Results led to ranking of the cumulative concentration order of the HMs, i.e.: soils (3476.6) > AGPs (1418.8) > roots (562.2) mg/kg-DW. The mean concentrations ranking order of studied HMs were in soil: Cu (1184.8) > Pb (865.5) > Cd (803.2) > Cr (623.0) > Zn (277.9) mg/kg-DW; roots, Cu (242.0) > Cd (239.5) > Zn (188.8) > Pb (63.5) > Cr (17.2) mg/kg-DW; and AGP environments, Cu (910.2) > Cd (322.9) > Zn (160.3) > Pb (152.9) > Cr (25.3) mg/kg-DW. Principal component analysis results demonstrated the same distribution pattern for the studied HMs between soil, root, and AGP environments, and the highest correlation coefficients were found for Cu, Zn, and Cd. Based on the obtained results (Cu-BAC (> 1), Zn-BCF (> 1), Zn-TF (< 1), Cu-AGP mean concentrations (> 1000 mg/kg-DW), and Cd-AGP mean concentrations (> 100 mg/kg-DW)), it can be concluded that grapevine cv Askari possesses potentials for phytoremediation purposes of Cu, Zn, and Cd. These results were acquired in a greenhouse environment and under controlled conditions; we suggest that the phytoremediation potential of this grapevine variety be assessed in a contaminated vineyard environment as well.

Role of Salvinia molesta in biodecolorization of methyl orange dye from water

In the present study, the potential of Salvinia molesta for biodecolorization of methyl orange (MO) dye from water was examined. Six glass vessels were filled with 4 L of water contaminated with MO with three concentrations (5, 15, and 25 mg/L), three with plants and another three without plant as contaminant control. The influence of operational parameters, including initial dye concentration, pH, temperature, and plant growth, on the efficacy of the biodecolorization process by S. molesta was determined. Temperature and pH was in the range of 25–26 °C and 6.3 to 7.3, respectively. Phytotransformation was monitored after 10 days through Fourier transform infrared (FTIR) spectroscopy, and a significant variation in the peak positions was demonstrated when compared to the control plant spectrum, indicating the adsorption of MO. The highest biodecolorization was 42% in a 5 mg/L MO dye concentration at pH 7.3 and at 27 °C. According to the FTIR results, a potential method for the biodecolourization of MO dye by S. molesta was proven. Salvinia molesta can be successfully used for upcoming eco-friendly phytoremediation purposes for dye removal.

Garden pansy (Viola × wittrockiana Gams.) - a good candidate for the revitalisation of polluted areas

In the current studies, heavy metal tolerance level, accumulation efficiency and sexual reproduction were determined in Viola × wittrockiana, a non-metallophytic ornamental cultivar in comparison to V. tricolor, a metallophyte, after zinc (Zn) or lead (Pb) treatment (0, 10, 100 and 1 000 ppm) in pot experiments. The seed germination frequency that was not reduced in comparison to the control, the effective Zn absorption from the soil and exclusion strategy for Pb, as well as the regular sexual reproduction of V. × wittrockiana treated with heavy metals all indicate the tolerance of this plant to heavy metals. The lack of a seed set under experimental conditions of V. × wittrockiana was due to the absence of pollinators, rather than the negative impact of heavy metals, as pollen viability and ovule development were normal under the treatments. The results indicate that V. × wittrockiana represents similar tolerance to Viola metallophytes and could be considered as a good material for the reclamation of polluted areas. The exceptional tolerance to heavy metals, the ability to initiate new generations in heavy-metal-burdened soil, which are additionally coupled with the unique beauty, make the garden pansy a good candidate to be potentially used in the future for phytoremediation purposes.

Application of biochar, compost and ZVI nanoparticles for the remediation of As, Cu, Pb and Zn polluted soil.

Here we tested the capacity of zero valent iron nanoparticles (nZVI) combined with two organic amendments, namely, compost and biochar, to immobilize metal(oid)s such as As, Cu, Pb, and Zn. In addition, the effects of the amendments on the development of Brassica juncea L., a plant widely used for phytoremediation purposes, were also examined. To perform the experiments, pots containing polluted soil were treated with nZVI, compost-biochar, or a blend of compost-biochar-nZVI. Metal(oid)s availability and soil properties were evaluated after 15 and 75 days, and the height and weight of the plants were measured to determine development. The compost-biochar amendment showed excellent capacity to immobilize metals, but As availability was considerably increased. However, the addition of nZVI to the mixture corrected this effect considerably. In addition, soil treatment with nZVI alone led to a slight increase in Cu availability, which was not observed for the mixture with organic amendments. With respect to soil properties, the CEC and pH were enhanced by the compost-biochar amendment, thereby favoring plant growth. Nevertheless, the nanoparticles reduced the concentration of available P, which impaired plant growth to a certain extent. In conclusion, Fe-based nanoparticles combined with organic amendments emerge as powerful approaches to remediate soils contaminated by metals and metalloids.

Changes of root microbial populations of natively grown plants during natural attenuation of V-Ti magnetite tailings.

Mine tailings contain dangerously high levels of toxic metals which pose a constant threat to local ecosystems. Few naturally grown native plants can colonize tailings site and the existence of their root-associated microbial populations is poorly understood. The objective of this study was to give further insights into the interactions between native plants and their microbiota during natural attenuation of abandoned V-Ti magnetite mine tailings. In the present work, we first examined the native plants' potential for phytoremediation using plant/soil analytical methods and then investigated the root microbial communities and their inferred functions using 16S rRNA-based metagenomics. It was found that in V-Ti magnetite mine tailings the two dominant plants Bothriochloa ischaemum and Typha angustifolia were able to increase available nitrogen in the rhizosphere soil by 23.3% and 53.7% respectively. The translocation factors (TF) for both plants indicated that B. ischaemum was able to accumulate Pb (TF=1.212), while T. angustifolia was an accumulator of Mn (TF=2.502). The microbial community structure was more complex in the soil associated with T. angustifolia than with B. ischaemum. The presence of both plants significantly reduced the population of Acinetobacter. Specifically, B. ischaemum enriched Massilia, Opitutus and Hydrogenophaga species while T. angustifolia significantly increased rhizobia species. Multivariate analyses revealed that among all tested soil variables Fe and total organic carbon (TOC) could be the key factors in shaping the microbial structure. The putative functional analysis indicated that soil sample of B. ischaemum was abundant with nitrate/nitrite reduction-related functions while that of T. angustifolia was rich in nitrogen fixing functions. The results indicate that these native plants host a diverse range of soil microbes, whose community structure can be shaped by plant types and soil variables. It is also possible that these plants can be used to improve soil nitrogen content and serve as bioaccumulators for Pb or Mn for phytoremediation purposes.

HEAVY METAL ACCUMULATION IN DIFFERENT PARTS OF TREES GROWN ON SEWAGE SLUDGE

Sewage sludge is a rest product deriving from the wastewater treatment plants. It is rich in nutrients and essential elements. Therefore sludge on-land utilisation can create an added value by recovering energy from biomass produced on marginal lands. However, widespread on-land recycling of sewage sludge might be limited due to high heavy metal content. Health organisations show an increasing concern about the risks posed to the environment and human health as many countries worldwide already are facing the heavy metal contamination problem. In the scientific literature it can be found, that high total heavy metal content is not directly related to an intensive metal uptake by plants. In this study samples were collected from three woody plant species (black locust, silver birch and aspen) growing directly on the sewage sludge in a storage site near Kaunas, Lithuania. Heavy metal content was detected separately in the leaves, stems and roots. It was determined that nearly all analysed heavy metals (lead, chromium, nickel, copper and zinc) were accumulated within normal range despite high total concentrations in the growing media, and only cadmium was accumulated at elevated concentration. Based on bioaccumulation factor, aspen could be considered as a Cd-accumulator and used for phytoremediation purposes.

Assaying the use of sodium thiosulphate as a biostimulant and its effect on cadmium accumulation and tolerance in Brassica oleracea plants.

An optimal uptake of mineral elements is crucial to ensure both crop yield and quality. The use of biostimulants is taking relevance to improve the nutrition of crops. Sulphur (S) is one of the elements with great potential within biostimulants. Furthermore, soil contamination by heavy metals such as cadmium (Cd) has become a serious environmental problem. Different studies have suggested the use of thiosulphate (TS) as a biostimulant and to increase the phytoremediation capacity of plants. Therefore, in the present study, we use a crop plant with high S requirements such as Brassica oleracea, to test whether TS serves as a biostimulant and whether affects Cd accumulation and tolerance. B. oleracea plants were grown with two different TS doses (2mM and 4mM), under Cd toxicity, and with the combination of Cd toxicity and both TS doses. Parameters of biomass, mineral elements accumulation, and stress tolerance were analyzed. The results showed that TS reduced biomass of B. oleracea plants. The application of 2mMTS increased Cd accumulation whereas the 4mM dose reduced it. On the other hand, TS incremented micronutrient accumulation on plants subjected to Cd toxicity and increased Zn contents. Besides, the application of 2mM to Cd-stressed plants enhanced photosynthesis performance and reduced oxidative stress. Finally, TS increased the antioxidant capacity of B. oleracea plants. Briefly, although TS can not be used as a biostimulant it could be used for Cd phytoremediation purposes and to enhance Zn accumulation in B. oleracea plants.

A novel plasma membrane-based NRAMP transporter contributes to Cd and Zn hyperaccumulation in Sedum alfredii Hance

Sedum alfredii is a native Chinese plant species that belongs to the group of metal hyperaccumulators and can accumulate significant amounts of Cd and Zn in the shoot without detrimental effects on its growth and metabolism. Understanding the molecular basis of this process may be essential for both phytoremediation of contaminated soils and developing heavy metal-resistant crop species. In this work, we have focused on NRAMP (Natural Resistance-Associated Macrophage Protein) family proteins transporters as potential candidates conferring superior hyperaccumulating ability in this species and undertaken its functional characterization. The bioinformatic analysis showed that SaNRAMP1 from S. alfredii showed very low similarity to all the NRAMP proteins from Arabidopsis thaliana. SaNRAMP1 was highly expressed in the young tissues of the shoots of hyperaccumulating ecotype of S. alfredii. Fluorescence imaging and functional studies revealed that SaNRAMP1 was localized at the plasma membrane and could transport not only Cd and Mn but also Zn. The latter trait makes it rather different from most reported NRAMP transporters. Overexpressing of SaNRAMP1 in tobacco significantly increased Cd, Zn, Mn concentration in the shoot. Taken together, our data suggest that SaNRAMP1 is a novel NRAMP protein that plays a significant role in Cd and Zn accumulation in S. alfredii. The above findings may be essential for understanding the mechanisms of metal hyperaccumulation in plants and used to both improve heavy metal tolerance in cash crops and use the potential of hyperaccumulating species for phytoremediation purposes.

A review of the performance of woody and herbaceous ornamental plants for phytoremediation in urban areas

Abstract: Urban and periurban areas are often contaminated by several pollutants. Phytoremediation is considered to be an effective and eco-friendly strategy for the restoration of these contaminated lands. For this purpose, the exploitation of ornamental plants could be an additional option, due to their positive impact on the landscape. In this paper, we reviewed a selection of species which have been proposed for utilization in phytoremediation. Several tree species have been introduced in the past into urban environments for parks, gardens and avenues, with a selection studied for their capacity to absorb, tolerate, and translocate contaminants. Shrubby and herbaceous species are also commonly exploited for their ornamental features and are now studied for phytoremediation purposes. The responses of several effective species to the presence of heavy metals or dangerous organic compounds in the growth substrate are examined in this paper.

The Response of Two Halophytic Species to Crude Oil-Contaminated Soil in the Northern Western Region of Egypt

A site that covers over 20 acres of coastal saline depression in the western Mediterranean coastal desert of Egypt (El-Hamra station, the main crude oil pipeline terminal in Alamein) is contaminated with petroleum. This area, prior to contamination by crude oil was dominated by different common halophytes. Atriplex halimus (L) and Arthrocnemum macrostachyum (Moric.) are now the most dominant species growing in this site. These species adapt themselves through different growth parameters, physiological and biochemical changes. Crude oil affects significantly on soil fertility and increasing pH (8.4). Importance value (IV), height and canopy diameter of the two studied species exhibited an increase in the polluted site. Organic metabolites such as fatty acids, antioxidant compounds and protein fractions in shoots of studied species which collected from the oil-contaminated and non-contaminated sites were examined. Fatty acid fractions exhibited the opposite performance especially the content of saturated C: 16 (palmitic), mono and di-unsaturated C18:1 (oleic) and C18:2 (linoleic) fatty acids as well as poly-unsaturated C18: 3 and C20: 3 (Omega -3 fatty acids). Antioxidant activity and most examined phenolic compounds were increased in A. macrostachyum which grow in a contaminated site. Protein fractions in A.halimus attained with enormous variations therefore, a Genomic Templet Stability (GTS %) was lower than in A. macrostachyum under contamination. The biochemical and behavioral responses to oil pollution varied with the two different species may be according to the genetic make-up of individuals, which make the two studied species useful and effective tools for phytoremediation purposes.

Hexachlorocyclohexane phytoremediation using Eucalyptus dunnii of a contaminated site in Argentina

In 1996, a diagnostic study performed in a 16-ha field located in Buenos Aires Province (Argentina), where a chemical industry produced 1,2,3,4,5,6-hexachlorocyclohexane (HCH) from 1960 to 1978, showed contamination with HCH ranging from 10 to 20,000 mg kg−1 dry soil (706.4 mg kg−1 average). For remediation purposes, a forestation plan was put into practice in 1997 employing approximately 12,300 Eucalyptus dunnii seedlings which by 2016 where fully grown into trees that formed a forest where local fauna can be found. Midterm analysis done in 2005, when E. dunnii trees had developed into 8–10 m high trees, indicated that HCH was incorporated into leaves and logs and soil phytoremediation was progressing. Final quantitation analysis of HCH in soil performed in 2016 demonstrated that the 97.2% of the field area was effectively decontaminated with 98.1% overall average efficiency. Thus, this work is the first global example of a successful employment of E. dunnii trees for HCH phytoremediation purposes at field scale. These results may encourage other researchers to test the ability of E. dunnii to phytoremediate soils contaminated with other chlorinated compounds like polychlorinated biphenyls (PCBs), polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs).