Pb Translocation Research Articles

Photosystem modulation and extracellular silicification in green microalgae: Key strategies for lead tolerance and removal

The escalating contamination caused by lead ions (Pb2⁺) and its harmful effects on all life forms has raised global concerns. Certain microalgae thrive in metal mining sites characterized by low pH and high concentrations of Pb2⁺, which are usually prohibitive for many microorganisms. Little is known about the mechanisms underlying the adaptation of such microalgae to these hostile conditions. In this study, we elucidated the adaptive strategies of the green microalga Micractinium belenophorum strain AUMW, isolated from a lead mining site, and its application for the removal of Pb+2. Results revealed that strain AUMW can efficiently tolerate up to 200 ppm of Pb+2 in an F/2 medium. Further experimental variables were optimized through response surface methodology (RSM), and 99.6 % removal of Pb2⁺ was achieved. Novel adaptive responses of strain AUMW to high levels of Pb2⁺ include: (i) activation of metal-protective response by modulation of quantum yield (Fv/Fm) and non-photochemical quenching (NPQ) of photosystem II; (ii) extracellular silicification encapsulated cells of strain AUMW and altered cell morphology from oval to hexagonal; (iii) silicification prevented intracellular translocation of Pb+2; (iv) silicification boosted adsorption of Pb+2, thus enhanced its removal. This study offers new insights into the protective role of silicification in green microalgae and its potential for the removal of metals from metal-polluted sites, waste from energy storage battery industries, and spent batteries. It also provides a solid base to explore the genetic and metabolic pathways involved in the adaptation of strain AUMW to elevated levels of Pb+2.

Heavy metal toxicity induced by sewage water treatment in three different vegetables (lettuce, spinach and cabbage) was alleviated by brassinosteroid and silicon supplementation

Purpose: Heavy metal stress due to the application of sewage water is considered a leading factor for constrained plant growth. Therefore, Current study was performed in the field to investigate the interactive influence of two irrigation sources (canal and sewage) and exogenous application of brassinosteroid (BRs) and silicon (Si) at different rates on growth, photosynthetic and physiological attributes of three leafy vegetables (lettuce, cabbage, and spinach). Methods: Three treatments were applied such as control, BRs and Si with three replications under split plot factorial design. Results: The results indicated that all the growth parameters including fresh biomass of plants and roots, dry biomass of plant and root, leaf area (LA), photosynthetic traits, chlorophyll contents, water use efficiency (WUE), activity of antioxidant enzymes; superoxide dismutase (SOD), peroxidase (POD), Catalase (CAT), ascorbate peroxidase (APX) and uptake of silicon except Cd and Pb contents were improved significantly with the foliar spray of BRs and Si over control treatment under both types of irrigation sources. However maximum improvement in leafy vegetables was recorded when the foliar spray of BRs and Si were applied under canal water irrigation. Conclusions: The foliar application of BRs and Si was proved as an ameliorating strategy for improving tolerance mechanisms associated with heavy metal stress. The major restoring mechanism was the restricted translocation of Cd and Pb leading to better growth and physiology under sewage water. Thus the application of BRs and Si reduced the detrimental effect of Cd and Pb led to improve the growth and physiological traits of leafy vegetables under irrigation with sewage water.

Deciphering the enhanced translocation of Pb, Ni and Cd from artificially polluted soil to Chrysopogon zizanioides augmented with Bacillus xiamenensis VITMSJ3.

The online version contains supplementary material available at 10.1007/s13205-024-04001-x.

Physiological responses of young cacao trees to soil water deficiency as affected by Pb pollution and Fe availability

Plants are subject to various abiotic stresses such as water shortage and exposure to heavy metals, such as Pb in soil. These types of stress trigger a series of plant responses, ranging from a decrease in leaf gas exchange, an increase in lipid peroxidation, and even changes in the chemical composition of leaves and roots. As an essential micronutrient, Fe is involved in several physiological and biochemical processes in plants, such as photosynthetic activity, directly participating in chlorophyll synthesis and electron transport, being necessary for the maintenance of the structure and functioning of chloroplasts. The main objective of this work was to evaluate the action of Fe in mitigating Pb toxicity in young plants of the CCN 51 cacao genotype, subjected to water deficit in the soil, through photosynthetic responses and analysis of the chemical composition of different parts of the plant. Plants were grown with Pb (2 mmol Pb kg-1 soil) and different equimolar doses of Pb+Fe in the soil (2+0.5, 2+1, 2+1.5 and 2+2 mmol kg−1 soil), maintaining constant the Pb dose, whose soil was subjected to water deficit, with gradual reduction of water content, or its moisture was maintained near to field capacity, making a total of 12 treatments, together with the control treatment (without addition of Pb and Fe in soil). It was observed that the greater Fe absorbing, by the root system, mitigated the Pb toxicity. Fe application, in adequate dose in soil (2 mmol Pb kg-1 soil + 0.5 mmol Fe kg−1 soil), mitigated the toxic effects caused by Pb and water deficit in the plants, through the greater Fe taking up and translocation for the shoot in Pb detriment. Greater Pb translocation and accumulation in the leaves caused damage to leaf gas exchange and to the accumulation of carbohydrates in leaves. Fe and Pb applied in soil competed with each other for root absorbing regardless of soil water conditions.

Investigation of Heavy Metal Concentrations and Accumulation Capacities of Naturally Growing Species in Old Garbage Area

In underdeveloped and/or developing countries, garbage is often randomly piled up in open areas. This method has been used to dispose of garbage/solid waste in Turkey for many years. Although pollution is not at the forefront in Bingöl province, the area located in the city center of the city has been used as a wild garbage storage area for approximately 18 years. Since the garbage in the area poses a danger to people and the environment, this area has become inactive with the establishment of a new solid waste disposal facility in the city. There are plants that have adapted to this area, which has been empty for about ten years. In this study, it was tried to determine in what proportions and organs the plant species distributed in the area accumulate heavy metals that may have come from garbage leachate. Plants identified in the field; Alyssum simplex, Cirsium libanoticum, Descurainia sophia, Fumaria asepala, Fumaria officinalis, Matricaria chamomilla, Papaver dubium, Scrophularia canina, Trifolium repens and Ziziphora capitata species. Fe, Cr, As, Cd and Pb concentrations (mg kg-1) of these species were measured in root, stem, leaf and flower organs and translocation factors (TF) were calculated for these species. In conclusion; Alyssum simplex, Cirsium libanoticum and Fumaria asepala for Fe, Cirsium libanoticum, Fumaria asepala, Fumaria officinalis and Matricaria chamomilla Cr and As, Cirsium libanoticum, Papaver dubium and Scrophularia canina for Cd and all other species except Alyssum simplex and Scrophularia canina for Pb translocation factors (TF) were found to be greater than 1 (TF>1). The accumulation potential of these species is thought to be promising so that they can be evaluated in phytoremediation.

Enhancing Phytoextraction Potential of Brassica napus for Contaminated Dredged Sediment Using Nitrogen Fertilizers and Organic Acids.

Dredged sediment contaminated with heavy metals can be remediated through phytoremediation. The main challenge in phytoremediation is the limited availability of heavy metals for plant uptake, particularly in multi-contaminated soil or sediment. This study aimed to assess the effect of the nitrogen fertilizers (ammonium nitrate (AN), ammonium sulfate (AS), and urea (UR)), organic acids (oxalic (OA) and malic (MA) acids), and their combined addition to sediment on enhancing the bioavailability and phytoremediation efficiency of heavy metals. The sediment dredged from Begej Canal (Serbia) had high levels of Cr, Cd, Cu, and Pb and was used in pot experiments to cultivate energy crop rapeseed (Brassica napus), which is known for its tolerance to heavy metals. The highest accumulation and translocation of Cu, Cd, and Pb were observed in the treatment with AN at a dose of 150 mg N/kg (AN150), in which shoot biomass was also the highest. The application of OA and MA increased heavy metal uptake but resulted in the lowest biomass production. A combination of MA with N fertilizers showed high uptake and accumulation of Cr and Cu.

Impact of coconut-fiber biochar on lead translocation, accumulation, and detoxification mechanisms in a soil–rice system under elevated lead stress

Biochar, an environmentally friendly material, was found to passivate lead (Pb) in contaminated soil effectively. This study utilized spectroscopic investigations and partial least squares path modeling (PLS-PM) analysis to examine the impact of coconut-fiber biochar (CFB) on the translocation, accumulation, and detoxification mechanisms of Pb in soil-rice systems. The results demonstrated a significant decrease (p < 0.05) in bioavailable Pb concentration in paddy soils with CFB amendment, as well as reduced Pb concentrations in rice roots, shoots, and brown rice. Synchrotron-based micro X-ray fluorescence analyses revealed that CFB application inhibited the migration of Pb to the rhizospheric soil region, leading to reduced Pb uptake by rice roots. Additionally, the CFB treatment decreased Pb concentrations in the cellular protoplasm of both roots and shoots, and enhanced the activity of antioxidant enzymes in rice plants, improving their Pb stress tolerance. PLS-PM analyses quantified the effects of CFB on the accumulation and detoxification pathways of Pb in the soil–rice system. Understanding how biochar influences the immobilization and detoxification of Pb in soil–rice systems could provide valuable insights for strategically using biochar to address hazardous elements in complex agricultural settings.

Evaluation of accumulation and translocation of Pb and Cr in Vigna unguiculata by hydroponic phytoremediation model and assess it genetic stability

In this study, the phytoremediation (accumulation and translocation) competence of Pb and Cr by Vigna unguiculata under metal supplemented hydrophonic medium was investigated. Moreover, analyzed the genomic DNA stability of V. unguiculata under different dosages of Pb and Cr was analyzed through RAPD analysis. To assess the phytoextraction along with tolerance of V. unguiculata under Pb and Cr metal stress circumstances, a number of investigations were performed. The dosages of these metals reached maximum values (Pd: root 4685.8 ± 8.57 mg kg−1 & shoot 956.63 ± 3.9 mg kg−1, and Cr: root 5157.62 ± 11.56 mg kg−1 & 1243.51 ± 10.2 mg kg−1) in plant tissues in 1500 mg L−1 treatment. The Bioconcentration factors (BCF) for Pb as well as Cr demonstrated that V. unguiculata possess phytoextraction competence and the translocation factors (TCF) revealed that these metals were slightly translocated. This study indicates that, V. unguiculatais more appropriate for the phytoremediation of Pb and Cr polluted soil. However, the total soluble protein (TSP) and RAPD analysis revealed the occurrent of metal toxicity on TSP and plant genomic DNA. As a result of these findings, this V. unguiculata may be used for phytoremediation purposes; however, cultivation for edible purposes should be avoided in metal-contaminated soil because it adsorbs toxic metals that can spread to the food web while using this plant yield.

Response of growth and Pb accumulation characteristics of plants with intercropping Arabis alpina-Zea mays to exogenous oxalic acid

In order to study the effects of oxalic acids on plant growth and Pb accumulation in different parts of the plants of intercropping Arabis alpina and Zea mays, pot experiment was conducted to investigate the changes of oxalic acid contents of the plants and Pb accumulation through exogenous oxalic acid addition (0, 5, 25 and 50 mmol kg−1). The results showed the root biomass of intercropped A. alpina and total biomass of Z. mays increased by 3.22 folds and 2.97 folds with 5 mmol kg−1 oxalic acid treatment. The oxalic acid contents of shoots and root secretions decreased by 86.5% and 44.3%, respectively. The BCF (bio-accumulation factor) and TF (translocation factor) of intercropping A. alpina reduced under 25 − 50 mmol kg−1 oxalic acid treatments. There were relationships between exogenous oxalic acid treatment concentrations and oxalic acid contents of A. alpina shoots, Z. mays root secretions. The Pb contents of shoots of A. alpina and Z. mays were related to exogenous oxalic acid additions and oxalic acid contents of shoots. In general, 5 mmol kg−1 oxalic acid treatment, that can improve plant growth of intercropped A. alpina and Z. mays, which Pb translocation and accumulation of A. alpina were promoted, whereas Pb accumulation of A. alpina was inhibited with 25 − 50 mmol kg−1 concentrations addition. This study will provide a basis for promoting the application of phytoremediation techniques and efficient crop production in heavy metal contaminated areas.

Uptake and translocation of lead and cadmium in wild-found plant species from Bekasi and Karawang, West Java, for phytoremediation

Environmental degradation due to lead (Pb) and cadmium (Cd) pollution has been increasing. One of the alternative cost-effective green technologies to clean up heavy metal contamination is phytoremediation. This research aims to determine the potential of wild-found plants that could be used as Pb and Cd bioaccumulators. Plant species in this study were collected from heavy metal-contaminated soil in Bekasi and Karawang, West Java. Five species, namely Saccharum spontaneum, Acorus calamus, Ipomoea fistulosa, Ludwigia hyssopifolia, and Eichhornia crassipes, were studied for Pb accumulation capacity. Furthermore, five plant species, namely Limnocharis flava, Colocasia esculenta, Ipomoea fistulosa, Commelina benghalensis, and Eichhornia crassipes, were studied for their Cd accumulation capacity. The experiment was done in a greenhouse for eight weeks. Pb and Cd concentration were analyzed using atomic absorption spectrometry (AAS) to determine the uptake and translocation of Pb or Cd. I. fistulosa accumulated the highest amount of Pb, with a growth rate of up to 27.07 g week−1, a bioconcentration factor (BCF) of 1.46, and a translocation factor (TF) of 0.87 upon 300 mg kg−1 Pb treatment. C. esculenta showed considerable Cd bioaccumulation, as indicated by a BCF of 0.95 and a TF of 0.65, accompanied by sustained relative biomass increase (124.9%) and the highest growth rate (36.96 g week−1) among tested plant species upon 75 mg kg−1 Cd treatment. With their capacities for bioaccumulating Pb and Cd, respectively, I. fistulosa and C. esculenta were identified as potential accumulator species for phytoremediation in heavy metal-contaminated sites such as former mining lands, landfills, and highly polluted agricultural lands.

Analysis of the Physiological Response and Reactive Oxygen Species in Castor Oil Plant (Ricinus Communis) in the Phytoremediation Processes with Plant Growth Promoter Bacteria (PGPB).

In the phytoremediation processes of mine tailings with Ricinus communis inoculated with PGPB, it was found that the Serratia K120 bacterium favors the translocation of Al, As, Cu, Pb, Cr, Cd, and Mn to the aerial part of the plant, with a significant difference (p < 0.05) concerning for the control. The bioaccumulation factor (BF) was > 1 in Al with all the bacteria, Pb, Serratia K120, Fe, Pantoea 113, Cu, Pb, Cd, Mn in Serratia MC119 and Serratia K120, Fe and As in Serratia K120 and Pantoea 134, indicating that Ricinus communis inoculated with PGPB functions as a hyper accumulating plant. The PGPB help to reduce the stress in the plants generated by the heavy metals, decreasing the H2O2, and increasing the activity of the enzymes SOD, CAT, APX, POX, and GR, for which the bacteria Serratia K120 and Pantoea 113 can be used as bioinoculants to favor phytoremediation processes.

Heavy metals and metalloids accumulation in common beans (Phaseolus vulgaris L.): A review

Heavy metals (HMs) and metalloids (Ms) such as arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb) represent serious environmental threats due to their wide abundance and high toxicity. Contamination of water and soils by HMs and Ms from natural or anthropogenic sources is of great concern in agricultural production due to their toxic effects on plants, adversely affecting food safety and plant growth. The uptake of HMs and Ms by Phaseolus vulgaris L. plants depends on several factors including soil properties such as pH, phosphate, and organic matter. High concentrations of HMs and Ms could be toxic to plants due to the increased generation of reactive oxygen species (ROS) such as (O2•-), (•OH), (H2O2), and (1O2), and oxidative stress due to an imbalance between ROS generation and antioxidant enzyme activity. To minimize the effects of ROS, plants have developed a complex defense mechanism based on the activity of antioxidant enzymes such as SOD, CAT, GPX, and phytohormones, especially salicylic acid (SA) that can reduce the toxicity of HMs and Ms. This review focuses on evaluating the accumulation and translocation of As, Cd, Hg, and Pb in Phaseolus vulgaris L. plants and on their possible effects on the growth of Phaseolus vulgaris L. in soil contaminated with these elements. The factors that affect the uptake of HMs and Ms by bean plants, and the defense mechanisms under oxidative stress caused by the presence of As, Cd, Hg, and Pb are also discussed. Furthermore, future research on mitigating HMs and Ms toxicity in Phaseolus vulgaris L. plants is highlighted

Potentially harmful elements pollute soil and vegetation around the Atrevida mine (Tarragona, NE Spain)

Mining activity is one of the main sources to pollute soil, water and plants. An analysis of soil and plant samples around the Atrevida mining area in Catalonia (NE Spain) was preformed to determine potentially harmful elements (PHEs). Soil and plant samples were taken at eight locations around the mining area. The topsoil (0–15 cm) samples were analysed for physico-chemical properties by standard methods, by ICP-MS for Cd, Co, Cr, Cu, Fe, Ni, Pb and Zn, and were microwave-digested. Plant, root and shoot samples were digested separately, and heavy metals were analysed by AAS. Translocation factor (TF), biological concentration factor (BCF) and biological accumulation factor (BAF) were determined to assess the tolerance strategies developed by native species and to evaluate their potential for phytoremediation purposes. Soil pH was generally acid (5.48–6.72), with high soil organic matter (SOM) content and a sandy loamy or loamy texture. According to the agricultural soil values in southern Europe, our PHEs concentrations exceeded the toxicity thresholds. The highest root content of the most studied PHEs appeared in Thymus vulgaris L. and Festuca ovina L., while Biscutella laevigata L. accumulated more PHEs in shoots. The TF values were > 1 in B. laevigata L., but BAF obtained < 1, except Pb. B. laevigata L., and can be considered potentially useful for phytoremediation for having the capacity to restrict the accumulation of large PHEs amounts in roots and Pb translocation to shoots.

Mechanisms of lead uptake and accumulation in wheat grains based on atmospheric deposition-soil sources

Lead (Pb) accumulation in wheat grains depends on two aspects: i) Pb uptake by the roots and shoots, and ii) the translocation of organ Pb into the grain. However, the underlying mechanism of the uptake and transport of Pb in wheat remains unclear. This study explored this mechanism by establishing field leaf-cutting comparison treatments. Interestingly, as the organ with the highest Pb concentration, only 20.40 % of the root's relative contribution to grain Pb. The relative contributions of the spike, flag leaf, second leaf, and third leaf to grain Pb were 33.13 %, 23.57 %, 13.21 %, and 9.69 %, respectively, which was opposite to their Pb concentration distribution trends. According to Pb isotope analysis, it was found leaf-cutting treatments reduced the proportion of atmospheric Pb in grain, and grain Pb predominantly comes from atmospheric deposition (79.60 %). Furthermore, from the bottom to the top, the concentration of Pb in internodes decreased gradually, and the proportions of Pb originating from soil in the nodes also decreased, revealing that wheat nodes hindered the translocation of Pb from roots and leaves to the grain. Therefore, the hindering effect of nodes on the migration of soil Pb in wheat resulted in atmospheric Pb having a more convenient pathway to the grain than soil Pb, and further leading grain Pb accumulation primarily depended on the contribution of the flag leaf and spike.

Imaging the distribution of nutrient elements and the uptake of toxic metals in industrial hemp and white mustard with laser-induced breakdown spectroscopy

Considering the quickly growing cannabis farming industry worldwide, it is important to do research on the ability of hemp to grow in heavy metal-contaminated soil. Hemp is a hyperaccumulator of heavy metals such as Cadmium (Cd) and Lead (Pb) and it can grow in soils with high concentrations of heavy metals. To gain more insight into the uptake and translocation of Cd and Pb in Cannabis sativa L., we exposed three-day old seedlings to solutions of varying concentrations of Cd and Pb for three days. Subsequently, we performed toxicology studies and analysed the localization and total uptake of heavy metals as well as essential and trace elements using Laser-Induced Breakdown Spectroscopy (LIBS) and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). We subsequently conducted a toxicity test and LIBS bioimaging on the reference plant Sinapis alba L. A low concentration of 20 μM of CdCl2 and PbCl2 was toxic for S. alba, while for C. sativa a concentration of 500 μM of CdCl2 and 50 μM of PbCl2 decreased the growth of the plants. According to the 2D bioimaging LIBS maps, heavy metals in all concentrations accumulated mostly in roots, translocation to stem and leaves was not observed. These results were confirmed by ICP-OES. Additionally, we were able to do bioimaging of important elements (e.g., Ca, Cu, Mg and Sr) in the plants. Based on the data from LIBS and ICP-OES, we were able to create a calibration curve for Pb. There, the Pb intensities distributed over a number of pixels in LIBS maps were correlated to concentration values from the ICP-OES.

Effects of chromium and lead mixture on pea's growth, ultrastructure, translocation and their accumulation in organs

Soil heavy metals have led to an increased risk to environment and food. In current decades, a large number of studies have focused on plant strategies for controlling water level, avoiding oxidative stress and maintaining essential functions to better elucidate the physiological and morphological changes in plants go through for their survival in a variety of environments. As a result, many terrestrial ecosystems (natural and agricultural) would be significantly impacted through effects of chromium and lead with some potentially collapsing owing to plant extinction. K2Cr2O7 and Pb(NO3)2 were added to soil to grow pea seedlings to examine the adsorption, translocation and accumulation of Cr and Pb in root, stem and leaf of pea and effects on the pea growth and distribution. Results showed that depending on the concentrations of Cr and Pb, the stem height of the pea was decreased by 3.5–25.4%, while the root length of the pea was reduced by 22.3–47.6%. Cr and Pb mixed pollution induced the granular callose that accumulated and attached to vessel wall in xylem. The morphology of pea's root, stem and leaf surface and cross section and EDS via scan electronic microscopy were altered. The results uncovered new toxic mechanism and newly understanding of toxicity of Cr and Pb to pea.

The function and community structure of arbuscular mycorrhizal fungi in ecological floating beds used for remediation of Pb contaminated wastewater

Arbuscular mycorrhizal fungi (AMF) have been demonstrated to be ubiquitous in aquatic ecosystems. However, their distributions and ecological functions are rarely studied. To date, a few studies have combined sewage treatment facilities with AMF to improve removal efficiency, but appropriate and highly tolerant AMF strains have not been explored, and the purification mechanisms remain unclear. In this study, three ecological floating-bed (EFB) installations inoculated with different AMF inocula (mine AMF inoculum, commercial AMF inoculum and non-AMF inoculated) were constructed to investigate their removal efficiency for Pb-contaminated wastewater. The AMF community structure shifts in the roots of Canna indica inhabiting EFBs during the three phases (pot culture phase, hydroponic phase and hydroponic phase with Pb stress) were tracked utilizing quantitative real-time polymerase chain reaction and Illumina sequencing techniques. Furthermore, transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) were used to detect the Pb location in mycorrhizal structures. The results showed that AMF could promote host plant growth and enhance the Pb removal efficiency of the EFBs. The higher the AMF abundance, the better the effect of the AMF on Pb purification by EFBs. Both flooding and Pb stress decreased the AMF diversity but did not significantly inhibit the abundance. The three inoculation treatments showed different community compositions with different dominant AMF taxa in different phases, and an uncultured Paraglomus species (Paraglomus sp. LC516188.1) was found to be the most dominant (99.65 %) AMF in the hydroponic phase with Pb stress. The TEM and EDS analysis results showed that the Paraglomus sp. could accumulate Pb in plant roots through their fungal structures (intercellular mycelium, intracellular mycelium, etc.), which alleviated the toxic effect of Pb on plant cells and limited Pb translocation. The new findings provide a theoretical basis for the application of AMF in plant-based bioremediation of wastewater and polluted waterbodies.

Phyto-exclusion of Pb and Cd by different genotypes of Andrographis paniculata (Burm. F.) nees: A novel approach for safe cultivation

Pb and Cd are ubiquitous heavy metals (HMs) in the environment and their accumulation in medicinal herbs poses a serious threat due to health hazards. The genetic selection of high-yielding and low Pb and Cd accumulating genotypes known as phtyoexclusion is a cost-effective and promising phytotechnology. In the present study, phtyoexclusion method was used for the selection of low Pb and Cd accumulating genotypes of Andrographis paniculata (Burm.F.) Nees with minimum alteration in their pharmacological important constituents in three application rates of Pb and Cd. The performance of genotypes of A. paniculata was evaluated by uptake and translocation of Pb and Cd, biomass yield, shoot-to-root ratio, metabolite content, oxidative enzymes, and mineral content for their safe production and commercial viability. The bio-concentration factor (BCF) and translocation factor (TF) of Pb among the genotypes ranged from 0.09-3.6 and 0.006–0.045, respectively. However, variations in BCF and TF of Cd were 0.05–3.36 and 0.001–0.150 respectively. The differential expression of the metal accumulation in genotypes of A. paniculata was majorly associated with ionomics and biomass. Four genotypes of A. paniculata were screened out and were divided in the three categories. One, genotypes that accumulated Pb and Cd below the prescribed limits with high productivity and tolerance could be used for safer herb production. In the second category, genotypes having high accumulation in roots and low translocation could be used for phytostabilization of the soil. The above-ground material of the plant can be used for the extraction of pure constituents. The third one is genotypes with high accumulators and low productivity. • Fifteen genotypes of A. paniculata were screened for Pb and Cd accumulation. • Four genotypes demostrated the phytoexcluder potential for Pb and Cd. • Biomass and mineral contents were the main drivers for low accumulating genotypes. • Some high accumulating genotypes can be good candidate for phytostabilization.

The fate of secondary metabolites in plants growing on Cd-, As-, and Pb-contaminated soils-a comprehensive review.

The study used scattered literature to summarize the effects of excess Cd, As, and Pb from contaminated soils on plant secondary metabolites/bioactive compounds (non-nutrient organic substances). Hence, we provided a systematic overview involving the sources and forms of Cd, As, and Pb in soils, plant uptake, mechanisms governing the interaction of these risk elements during the formation of secondary metabolites, and subsequent effects. The biogeochemical characteristics of soils are directly responsible for the mobility and bioavailability of risk elements, which include pH, redox potential, dissolved organic carbon, clay content, Fe/Mn/Al oxides, and microbial transformations. The radial risk element flow in plant systems is restricted by the apoplastic barrier (e.g., Casparian strip) and chelation (phytochelatins and vacuole sequestration) in roots. However, bioaccumulation is primarily a function of risk element concentration and plant genotype. The translocation of risk elements to the shoot via the xylem and phloem is well-mediated by transporter proteins. Besides the dysfunction of growth, photosynthesis, and respiration, excess Cd, As, and Pb in plants trigger the production of secondary metabolites with antioxidant properties to counteract the toxic effects. Eventually, this affects the quantity and quality of secondary metabolites (including phenolics, flavonoids, and terpenes) and adversely influences their antioxidant, antiinflammatory, antidiabetic, anticoagulant, and lipid-lowering properties. The mechanisms governing the translocation of Cd, As, and Pb are vital for regulating risk element accumulation in plants and subsequent effects on secondary metabolites.

Assisted Phytostabilization of Mine-Tailings with Prosopis laevigata (Fabaceae) and Biochar.

Phytoremediation is a cost-effective technique to remediate heavy metal (HM) polluted sites. However, the toxic effects of HM can limit plant establishment and development, reducing phytoremediation effectiveness. Therefore, the addition of organic amendments to mine wastes, such as biochar, improves the establishment of plants and reduces the bioavailability of toxic HM and its subsequent absorption by plants. Prosopis laevigata can establish naturally in mine tailings and accumulate different HM; however, these individuals show morphological and genetic damage. In this study, the effect of biochar on HM bioaccumulation in roots and aerial tissues, HM translocation, morphological characters and plant growth were evaluated, after three and six months of exposure. Plants grown on mine tailings with biochar presented significantly higher values for most of the evaluated characters, in respect to plants that grew on mine tailing substrate. Biochar addition reduced the bioaccumulation and translocation of Cu, Pb, and Cd, while it favored the translocation of essential metals such as Fe and Mn. The addition of biochar from agro-industrial residues to mine tailings improves the establishment of plants with potential to phytoextract and phytostabilize metals from polluted soils. Using biochar and heavy metal accumulating plants constitutes an assisted phytostabilization strategy with great potential for HM polluted sites such as Cd and Pb.