Overexpression of OsTIP1;2 confers arsenite tolerance in rice and reduces root-to-shoot translocation of arsenic.

Tonoplast Intrinsic Proteins (TIPs) are vital in transporting water and solutes across vacuolar membrane. The role of TIPs in the arsenic stress response is largely undefined. Rice shows sensitivity to the arsenite [As[III]] stress and its accumulation at high concentrations in grains poses severe health hazards. In this study, functional characterization of OsTIP1;2 from Oryza sativa indica cultivar Pusa Basmati-1 (PB-1) was done under the As[III] stress. Overexpression of OsTIP1;2 in PB-1 rice conferred tolerance to As[III] treatment measured in terms of enhanced shoot growth, biomass, and shoot/root ratio of overexpression (OE) lines compared to the wild-type (WT) plants. Moreover, seed priming with the IRW100 yeast cells (deficient in vacuolar membrane As[III] transporter YCF1) expressing OsTIP1;2 further increased As[III] stress tolerance of both WT and OE plants. The dithizone assay showed that WT plants accumulated high arsenic in shoots, while OE lines accumulated more arsenic in roots than shoots thereby limiting the translocation of arsenic to shoot. The activity of enzymatic and non-enzymatic antioxidants also increased in the OE lines on exposure to As[III]. The tissue-specific localization showed OsTIP1;2 promoter activity in root and root hairs, indicating its possible root-specific function. After As[III] treatment in hydroponic medium, the arsenic translocation factor (TF) for WT was around 0.8, while that of OE lines was around 0.2. Moreover, the arsenic content in the grains of OE lines reduced significantly compared to WT plants.

Removal of perfluoroalkyl acids (PFAAs) from aqueous solution by water hyacinth (Eichhornia crassipes): Uptake, accumulation, and translocation.

Although Eichhornia crassipes, commonly known as water hyacinth, has been widely used in wastewater treatment, further investigations are still needed to explore the removal efficiency of perfluoroalkyl acids (PFAAs) from the aqueous environment using this floating aquatic plant. In this study, a hydroponic experiment was conducted to assess accumulation, bioconcentration factors (BCFs), translocation factors (TFs), and removal rates of eight PFAAs by water hyacinth. The obtained results indicated that all PFAAs, including five perfluoroalkyl carboxylic acids (PFCAs) with chain lengths C4-C8 and three perfluoroalkyl sulfonic acids (PFSAs) with C4, C6, and C8, were readily accumulated in water hyacinth. Throughout the duration of the experiment, there was a noticeable increase in PFAA concentrations and BCF values for different plant parts. For the root, PFAAs with more carbon numbers showed a higher uptake than the shorter homologues, with PFSAs being more readily accumulated compared to PFCAs with the same carbon number in the molecules. In contrast, the levels of long-chain PFAAs were comparatively lower than those of short-chain substances in the stem and leaf. Notably, PFAAs with less carbon numbers, like PFPeA, PFBA, and PFBS, showed a remarkable translocation from the root to the stem and leaf with TFs >1. For the whole plant, no significant correlation was found between BCFs and organic carbon-water partition coefficients (Koc), octanol-water partition coefficients (Kow), membrane-water distribution coefficients (Dmw), or protein-water distribution coefficients (Dpw). The removal rates of PFAAs ranged from 40.3 to 63.5 % throughout the three weeks of the experiment while the removal efficiencies varied from 48.9 % for PFHxS to 82.6 % for PFPeA in the last week.

Bioaccumulation efficacy and physio-morphological adaptations in response to iron and aluminium contamination of Indian camphorweed (Pluchea indica L.) using different growth substrates.

The aim of this study was to assess the removal capability of Fe/Al contamination of Indian camphorweed (Pluchea indica; hereafter, P. indica) using different growth substrates (100% sand, gardening soil, vermiculite, and zeolite). In addition, the study aimed at observing the physio-morphological adaptation strategies of P. indica under excess Fe/Al levels in a controlled greenhouse environment. After a 4-week treatment, P. indica plants under excess Fe in the 100% sand substrate exhibited signs of decay and eventually death. In contrast, the growth performances of P. indica under gardening soil substrate remained sustained even when exposed to Fe/Al stress. Under zeolite substrate, Fe in the root tissues was 23.1 and 34.7 mg g-1 DW after 1 and 4 weeks of incubation, respectively. In addition, Al in the root tissues also increased to 1.54 mg g-1 DW after 1 week and 1.59 mg g-1 DW after 4 weeks, when subjected to 20 mM Al treatment. Zeolite was observed to be a promising substrate to regulate the uptake of Fe (3.31 mg plant-1) and Al (0.51 mg plant-1) by the root tissues. The restriction of Fe and Al in the root and a low translocation to the leaf organ was indicated by a low translocation factor (< 1.0). High Fe concentrations in the root and leaf tissues negatively affected root elongation, and the net photosynthetic rate decreased by > 40% compared to positive control. Gas exchange parameters and leaf temperature were found the most sensitive to Fe/Al stress. Moreover, the limited transpiration rate under Fe/Al stress caused an increase of the leaf temperature and crop stress index. The findings suggest that P. indica grown using zeolite substrate may serve as a good model system for constructed wetlands, storing excess Al in the root tissues without any significant growth inhibition.

Synergistic effects of vermicompost and mycorrhizal inoculation on arsenic tolerance and phytostabilization in safflower (Carthamus tinctorius L.).

Arsenic (As) is a hazardous metalloid, and mycorrhizal inoculation and vermicompost amendment can influence As bioremediation. However, the studies concerning the sole and joint effects of arbuscular mycorrhizal fungi (AMF) and vermicompost on the phytoremediation efficacy are limited. In the present study at first, the impact of various levels of vermicompost (0, 2, 4, and 8% w/w) was investigated on As mobility in soil and safflower (Carthamus tinctorius L.) plants grown in soils of spiked with 0, 40, and 80 mg kg-1 As. Results revealed that with increasing dose of vermicompost, bioavailable As in soil decreased which resulted in a lower bioaccumulation factor and translocation factor (TF) and led to a significant increase of tolerance index (TI) and total chlorophyll content in plants. The highest effect on TI and total As accumulation per plant was obtained in the dosage of 8% vermicompost. Therefore, in the second experiment, the sole and joint effects of 8% vermicompost and inoculation with Rhizophagus intraradices were assessed on the tolerance and accumulation of As in safflower. The addition of vermicompost aggravated mycorrhizal colonization but did not significantly influence mycorrhizal dependency under As stress. The joint effects of AMF and vermicompost improved the dry weight of roots and shoots, increased P concentration and P:As ratio in shoots, reduced malondialdehyde content, and moderated ascorbate peroxidase activity in leaves of As-stressed plants. Interestingly, co-application of AMF and vermicompost more than their sole usage decreased As concentration in shoots and TF and more strongly increased total As accumulation per plant. These findings suggest that mycorrhizal inoculation and vermicompost have a synergistic effect on As tolerance and phytostabilization efficacy of safflower plants, and their combined application may be a new option to remediate As-contaminated soils.

Predicting Cd accumulation in rice and identifying nonlinear effects of soil nutrient elements based on machine learning methods.

The spatial mismatch of Cd content in soil and rice causes difficulties in environmental management for paddy soil. To investigate the influence of soil environment on the accumulation of Cd in rice grain, we conducted a paired field sampling in the middle of the Xiangjiang River basin, examining the relationships between soil properties, soil nutrient elements, Cd content, plant uptake factor (PUFCd), and translocation factors in different rice organs (root, shoot, and grain). The total soil Cd (CdT) and available Cd (CdA) contents and PUFCd showed large spatial variability with ranges of 0.31-6.19 mg/kg, 0.03-3.07 mg/kg, and 0.02-3.51, respectively. Soil pH, CdT, CdA, and the contents of soil nutrient elements (Mg, Mn, Ca, P, Si, and B) were linearly correlated with grain Cd content (Cdg) and PUFCd. The decision tree analysis identified nonlinear effects of Si, Zn and Fe on rice Cd accumulation, which suggested that low Si and high Zn led to high Cdg, and low Si and Fe caused high PUFCd. Using the soil nutrient elements as predictor variables, random forest models successfully predicted the Cdg and PUFCd and performed better than multiple linear regressions. It suggested the impacts of soil nutrient elements on rice Cd accumulation should receive more attention.

Stem cutting: A novel introduction site for transporting water-insoluble particles into tomato (Solanum lycopersicum) seedlings.

The introduction of exogenous particles into plants has promising applications in agriculture and biotechnology. Nanoparticles can be transported into plants through foliar application or root uptake. However, both methods have limitations in terms of the size of the particles (<40 nm) that can be transported due to the barriers of the cell wall and cuticle. In the present study, we proposed a novel method to deliver particles of up to 110 nm into plants by cutting the stem of tomato seedlings. We demonstrated for the first time, using water-insoluble silica colloids, that not only nanoparticles but also submicron particles can be transported toward the leaves when the plant stem is used as the entry point of particles. Thirty-five-day-old tomato seedlings were used as the target plants. When the cut stem seedlings were immersed in the colloidal particle suspension for up to 24 h, significant particle accumulation was observed in the nodes and leaves. The relatively low particle concentrations (10 mg/L) allowed effective transport throughout the plants. Silica particles with average diameters of 10 nm and 110 nm were both well transported and moved through the stem. Even after the particles entered the plant, adventitious roots were formed, resulting in the formation of whole plants with roots, stems, and leaves. This method can be applied not only to tomatoes but also to other food crops for various applications in plant biotechnology.

Uptake, accumulation and toxicity of short chain chlorinated paraffins to wheat (Triticum aestivum L.).

Short chain chlorinated paraffins (SCCPs) are ubiquitous persistent organic pollutants. They have been widely detected in plant-based foods and might cause adverse impacts on humans. Nevertheless, uptake and accumulation mechanisms of SCCPs in plants remain unclear. In this study, the soil culture data indicated that SCCPs were strongly absorbed by roots (root concentration factor, RCF>1) yet limited translocated to shoots (translocation factor<1). The uptake mechanism was explored by hydroponic exposure, showing that hydrophobicity and molecular size influenced the root uptake and translocation of SCCPs. RCFs were significantly correlated with logKow values and molecular weights in a parabolic curve relationship. Besides, it was extremely difficult for SCCPs to translocate from shoots back to roots via phloem. An active energy-dependent process was proposed to be involved in the root uptake of SCCPs, which was supported by the uptake inhibition by the low temperature and metabolic inhibitor. Though SCCPs at environmentally relevant concentrations had no negative impacts on root morphology and chlorophyll contents, it caused obvious changes in cellular ultrastructure of root tip cells and induced a significant increase in superoxide dismutase activity. This information may be beneficial to moderate crop contamination by SCCPs, and to remedy soils polluted by SCCPs with plants.

[Interaction and Transport Characteristics of Lead and Cadmium in Different Soil-wheat Systems].

In this study, four groups of lead(Pb) and cadmium(Cd) combined treatments with different concentration ratios were set up in Hailun black soil, Xianning brown-red soil, and Changwu Heilu soil, and wheat(Zhengmai 9023) was planted for a five-month pot experiment to analyze the Pb-Cd interaction behavior on heavy metal bioaccumulation in wheat under three soil-wheat systems. The low pH brown-red soil had the highest water-soluble Cd and Pb contents with significant Pb-Cd interactions in the soil, whereas the black soil with high organic matter and Heilu soil with high calcium carbonate content exhibited lower Cd and Pb activities. Among the three soils, wheat height and dry weight showed the poorest growth performance in the Heilu soil, but the wheat height increased by 2.68-8.49 cm compared with that in the control under the Pb-Cd combined treatment, whereas Pb-Cd interaction had the least effect on wheat height and dry weight in black soil and inhibited the growth of wheat in the brown-red soil. In the transport process of Cd or Pb in wheat, Pb-Cd interaction showed quite different effects in the three soil-wheat systems. Under the 125 mg·kg-1 and 250 mg·kg-1 Pb treatments, the Pb content in wheat grain planted in brown-red soil significantly increased by 73.2% and 19.1% with the addition of Cd, respectively, and therefore there was a synergistic effect between Pb and Cd. Under the 0.3 mg·kg-1 and 0.6 mg·kg-1 Cd treatments, the Cd content in wheat grains planted in black soil decreased by 51% and 33% with the addition of Pb, respectively; therefore, there was an antagonist effect between Pb and Cd. In the Heilu soil, a synergistic effect of Cd on Pb transport in wheat leaves was only observed under high Pb treatment. Therefore, pH and organic matter content were the key factors that determined the interaction behavior of Pb and Cd. The wheat food security risk of Pb and Cd combined pollution was higher than that of single metal pollution in acidic brown-red soil and lower in high organic matter black soil, whereas the interaction of Pb and Cd had little impact on the wheat food security risk of alkaline Heilu soil.

Comparative assessment of two biodegradable chelants, S,S-ethylenediamine disuccinic acid and nitrilotriacetic acid, in facilitating Cd remediation by lesser swine cress (Coronopus didymus, Brassicaceae).

Chemically assisted phytoremediation is suggested as an effective approach to amplify the metal-remediating potential of hyperaccumulators. The current study assessed the efficiency of two biodegradable chelants (S,S-ethylenediamine disuccinic acid, EDDS; nitrilotriacetic acid, NTA) in enhancing the remediation of Cd by Coronopus didymus (Brassicaceae). C. didymus growing in Cd-contaminated soil (35-175 mg kg-1 soil) showed increased growth and biomass due to the hormesis effect, and chelant supplementation further increased growth, biomass, and Cd accumulation. A significant interaction with chelants and different Cd concentrations was observed, except for Cd content in roots and Cd content in leaves, which exhibited a non-significant interaction with chelant addition. The effect of the NTA amendment on the root dry biomass and shoot dry biomass was more pronounced than EDDS at all the Cd treatments. Upon addition of EDDS and NTA, bio-concentration factor values were enhanced by ~184-205 and ~ 199-208, respectively. The tolerance index of root and shoot increased over the control upon the addition of chelants, with NTA being better than EDDS. With chelant supplementation, bio-accumulation coefficient values were in the order Cd35 + NTA (~163%) > Cd105 + NTA (~137%) > Cd35 + EDDS (~89%) > Cd175 + NTA (~85%) > Cd105 + EDDS (~62%) > Cd175 + EDDS (~40%). The translocation factor correlated positively (r ≥ 0.8) with tolerance index and Cd accumulation in different plant parts. The study demonstrated that chelant supplementation enhanced Cd-remediation efficiency in C. didymus as depicted by improved plant growth and metal accumulation, and NTA was more effective than EDDS in reclaiming Cd.

Iron (Fe) toxicity, uptake, translocation, and physio-morphological responses in Catharanthus roseus.

Iron (Fe) toxicity in plant species depends on the availability of Fe in the soil, uptake ability by the root system, and translocation rate to other parts of the plant. The aim of this study was to assess Fe uptake by root tissues of Catharanthus roseus, translocation rate to leaf tissues, and the impairment of plant physio-morphological characteristics. Fe uptake by the roots (~ 700 µg g-1 DW) of C. roseus was observed during the early exposure period (1 week), and translocation factor from root to shoot was fluctuated as an independent strategy. A high level of Fe content in the root tissues significantly inhibited root length and root dry weight. Under acidic pH condition, an enrichment of Fe in the shoots (~ 400 µg g-1 DW) led to increase in leaf temperature (> 2.5 °C compared to control) and crop stress index (> 0.6), resulting in stomatal closure, subsequently decreasing CO2 assimilation rate and H2O transpiration rate. An increment of CSI in Fe-stressed plants was negatively related to stomatal conductance, indicating stomatal closure with an increase in Fe in the leaf tissues. High Fe levels in the leaf tissues directly induced toxic symptoms including leaf bronzing, leaf spotting, leaf necrosis, leaf chlorosis, and leaf senescence in C. roseus plants. In summary, C. roseus was identified as a good candidate plant for Fe phytoextraction, depending on Fe bioaccumulation, therefore 50 mM Fe treatment was designated as an excess Fe to cause the growth inhibition, especially in the prolonged Fe incubation periods. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-023-01379-5.

[Effects of Exogenous Plant Hormone Spraying on the Phytoremediation by Bidens pilosa L. in Cadmium-contaminated Soil].

To explore the effect of exogenous plant hormone spraying on the absorption of heavy metals by hyperaccumulated plants, Bidens pilosa L. was selected as the tested plant owing to the large biomass, short growth cycle, and high accumulation efficiency. Here, the effect of foliar spraying 6-benzylaminopurine (6-BA), salicylic acid (SA), and 24-epi-brassinosteroid (24-EBR) on the remediation of cadmium (Cd)-contaminated soil by B. pilosa L. was examined. The results showed:① the efficiency of the remediation in Cd-contaminated soil by B. pilosa L. was effectively enhanced after the spraying of all three kinds of exogenous plant hormones with appropriate concentrations. The spraying of the three exogenous plant hormones could promote the cadmium concentration in the leaves of B. pilosa L. to increase by 4.21%, 31.79%, and 14.89%; promote the translocation factor (TF) to increase by 9.67%, 18.83%, and 17.85%; promote the phytoextraction rates (PR) to increase by 15.36%, 32.33%, and 64.38%, respectively. ② The growth of B. pilosa L. was significantly promoted after the spraying of the three kinds of exogenous plant hormones with appropriate concentrations. The spraying of the three exogenous plant hormones could promote plant growth under cadmium stress, and the dry weight of the plant root, stem, and leaf was increased by 37.53%, 74.50%, and 104.02%, respectively. ③ The photosynthesis of B. pilosa L. was significantly enhanced after the spraying of the three kinds of exogenous plant hormones with appropriate concentrations. The chlorophyll concentration of the plant was significantly increased after foliar spraying with plant hormones, and the concentration of chlorophyll a was increased by 79.31%, 92.27%, and 51.12%; the photochemical quenching coefficient (qP) was increased by 11.32%, 89.16%, and 78.43%; and the non-photochemical quenching coefficient (NPQ) was increased by 51.71%, 241.12%, and 27.85%, respectively, after foliar spraying with appropriate concentrations of 6-BA, SA, and 24-EBR. ④ The antioxidant capacity of B. pilosa L. was significantly strengthened after the spraying of the three kinds of exogenous plant hormones with appropriate concentrations. The malondialdehyde (MDA) concentration of the plant was reduced by 62.41%, 68.67%, and 46.76% after the application of 6-BA, SA, and 24-EBR, respectively. Meanwhile, superoxide dismutase (SOD) was increased by 68.33%, 10.28%, and 6.17%, and catalase (CAT) was increased by 31.43%, 37.87%, and 37.31%, respectively. Generally, the spraying of exogenous 6-BA, SA, and 24-EBR with the appropriate concentration under Cd stress could significantly increase the biomass of B. pilosa L. and promote the accumulation of heavy metals in the plant, improve the photosynthetic ability of the plant, reduce the oxidative damage of the plant under heavy metal stress, enhance the antioxidant capacity, and improve the absorption and tolerance of plants to Cd. It also could promote the transfer of Cd from roots to shoots, improve the phytoextraction rates of Cd from the plant, and effectively strengthen the phytoremediation efficiency. Among them, 30 mg·L-1 SA foliar spraying had the best effect.

Metal tolerance and Cd phytoremoval ability in Pisum sativum grown in spiked nutrient solution.

In the presented study, the effects of cadmium (Cd) stress and silicon (Si) supplementation on the pea plant (Pisum sativum L.) were investigated. The tendency to accumulate cadmium in the relevant morphological parts of the plant (roots and shoots respectively)-bioaccumulation, the transfer of this element in the plant (translocation) and the physiological parameters of the plant through indicators of oxidative stress were determined. Model studies were carried out at pH values 6.0 and 5.0 plant growth conditions in the hydroponic cultivation. It was shown that Cd accumulates mostly in plant roots at both pH levels. However, the Cd content is higher in the plants grown at lower pH. The Cd translocation factor was below 1.0, which indicates that the pea is an excluder plant. The contamination of the plant growth environment with Cd causes the increased antioxidant stress by the growing parameters of the total phenolic content (TPC), polyphenol oxidase activity (PPO), the malondialdehyde (MDA) and lipid peroxidation (LP). The results obtained showed that the supplementation with Si reduces these parameters, thus lowering the oxidative stress of the plant. Moreover, supplementation with Si leads to a lower content of Cd in the roots and reduces bioaccumulation of Cd in shoots and roots of pea plants.

Effect of sludge amelioration on yield, accumulation and translocation of heavy metals in soybean grown in acid and alkaline soils.

A greenhouse pot experiment was conducted with seven different levels of sludge (0, 5, 10, 20, 40, 80, 160 g kg-1) to assess the potential impact of sludge application on soybean (Glycine max (L.) Merr.) productivity, metal accumulation and translocation, and physico-chemical changes in acid and alkaline soils. The outcomes revealed that the application of sludge @ 5.0 to 160 g kg-1 resulted in a significant (p < 0.05) increase in seed and straw yield in both acid and alkaline soils compared to control. All the assessed heavy metals in soybean were within permissible ranges and did not exceed the phytotoxic limit, except for Fe, Zn, and Cu in the roots from the application of sewage sludge. The values of bioaccumulation factor (BFroot/soil) and translocation factor i.e., TFstraw/root and TFseed/straw were < 1.0 for Ni, Pb and Cr. Overall, for all the sludge application doses the soil pH was observed to increase in the acid soil and decline in alkaline soil when compared to the control. All the investigated heavy metals (Fe, Mn, Zn, Cu, Ni, Cd, Pb, and Cr) in the different plant tissues (root, straw and seed) of soybean were correlated with the soil variables. The study finds that sludge can be a potential organic fertilizer and function as an eco-friendly technique for the recycling of nutrients in the soil while keeping a check on the heavy metals' availability to plants.

Uptake and Enantiomeric Selectivity of ß-Blockers in Lettuce (Lactuca sativa L.) and Tomato (Lycopersicon esculentum M.) in Soil-Pot Culture.

The uptake and translocation of ß-blockers in lettuce (Lactuca sativa L.) and tomato (Lycopersicon esculentum M.) were investigated by carrying out a 70-day soil-pot cultivation. The root uptake parameters of ß-blockers in lettuce decreased in the order of atenolol (ATE) > sotalol (SOT) > propranolol (PRO) with root bioconcentration factors (BCFsroot/soil) of 0.158, 0.136, and 0.096, respectively, which were positively correlated with their water solubility. The BCFroot/soil of ß-blockers in tomato was higher than those in lettuce. ATE and PRO were prone to migrate to the aerial parts of tomato with translocation factors of 3.31 and 4.11, respectively. In tomato fruits, the enantiomeric profile of PRO and ATE shifted to that dominated by the more toxic enantiomer, i.e., (S)-PRO and (R)-ATE. The enantiomeric selectivity of ß-blockers in the edible parts of lettuce and tomato indicated the potential ecotoxicity of these pharmaceuticals for plants and the human exposure risk via vegetable intake.

Concentration-dependent mechanisms of fluoranthene uptake by ryegrass.

Fluoranthene (Flu) uptake by plants is affected by plant growth and environmental concentration. Although plant growth processes, including substance synthesis and antioxidant enzyme activities, have been reported to regulate Flu uptake, their contributions have been poorly evaluated. Moreover, the effect of Flu concentration is little known. Here, low concentrations (0, 1, 5, and 10 mg/L) and high concentrations (20, 30, and 40 mg/L) of Flu were set to compare the changes in Flu uptake by ryegrass (Lolium multiflorum Lam.). Indices of plant growth (biomass, root length, root area, root tip number, and photosynthesis and transpiration rates), substance synthesis (indole acetic acid [IAA] content), and antioxidant enzyme activities (superoxide dismutase [SOD], peroxidase [POD], and catalase [CAT]) were recorded to unravel the mechanism of Flu uptake. Findings suggested that the Langmuir model fitted Flu uptake by ryegrass well. Flu absorption capacity in the root was stronger than that that in the leaf. Flu bioconcentration and translocation factors increased then reduced with the increase in Flu concentration and reached the maximum value under 5 mg/L Flu treatment. Plant growth and IAA content had the same pattern as before bioconcentration factor (BCF). SOD and POD activities increased then decreased with Flu concentration and reached their highest levels under 30 and 20 mg/L Flu treatments, respectively, whereas CAT activity decreased continuously and reached its lowest level under 40 mg/L Flu treatment. Variance partitioning analysis indicated that IAA content had the greatest significant effect on Flu uptake under low-concentration Flu treatments, whereas antioxidant enzyme activities had the greatest significant effect on Flu uptake under high-concentration Flu treatments. Revealing the concentration-dependent mechanisms of Flu uptake could provide a basis for regulating pollutant accumulation in plants.

Metal uptake and translocation by Chinese brake fern (Pteris vittata) and diversity of rhizosphere microbial communities under single and combined arsenic and cadmium stress.

Chinese brake fern (Pteris vittata) can increase tolerance to arsenic (As) and cadmium (Cd) toxicity by regulating rhizosphere microbial diversity. However, effects of combined As-Cd stress on microbial diversity and plant uptake and transport remain poorly understood. Therefore, effects of different concentrations of As and Cd on Pteris vittata (P. vittata) metal uptake and translocation and rhizosphere microbial diversity were examined in a pot experiment. The results indicated that As primarily accumulated aboveground in P. vittata (bioconcentration factor (BCF) ≤ 51.3; translocation factor (TF) ≈ 4), whereas Cd primarily accumulated belowground (BCF ≤ 39.1; TF < 1). Under single As, single Cd, and As-Cd combined stress, the most dominant bacteria and fungi were Burkholderia-Caballeronia-P (6.62-27.92%) and Boeremia (4.61-30.42%), Massilia (8.07-11.51%) and Trichoderma (4.47-22.20%), and Bradyrhizobium (2.24-10.38%) and Boeremia (3.16-45.69%), respectively, and their abundance ratios had a significant impact on the efficiency of P. vittata for As and Cd accumulation. However, with increasing As and Cd concentrations, abundances of plant pathogenic bacteria such as Fusarium and Chaetomium (the highest abundances were 18.08% and 23.72%, respectively) increased, indicating that As and Cd concentrations reduced P. vittata resistance to pathogens. At high soil concentrations of As-Cd, although plant As and Cd contents increased and microbial diversity was highest, enrichment efficiency and transportability of As and Cd decreased substantially. Therefore, pollution intensity should be considered when evaluating P. vittata suitability for phytoremediation of combined As-Cd contaminated soils.

Phytoremediation of copper-contaminated soils by drip or sprinkling irrigation coupled with intercropping.

Intercropping improves the phytoremediation of soil trace metal contamination. Dripping irrigation could further promote the phytoremediation of trace metals by influencing their speciation and total amount in soil. However, there is currently insufficient information elucidating this synergistic effect. In this study, the combined effect of drip irrigation and intercropping on the phytoremediation of Cu-contaminated soil was testified by investigating the changes of Cu spatial distribution and speciation in soil irrigated by dripping or sprinkling methods, as well as Cu bioconcentration factor and translocation factor by plants. Results showed that after a 30-day drip irrigation, the Cu level in soils near the drip outlet decreased by 4.7% and that in Triticum aestivum L. (T. aestivum) roots intercropped with Helianthus annuus L. (H. annuus) and Zea mays L. (Z. mays) dropped by 53.2% and 25.1%, respectively, relative to sprinkler irrigation. Meanwhile, the total Cu and exchangeable Cu levels in soils 6 cm away from the drip outlet increased by 10.8% and 20.4% after 30 days of drip irrigation, leading to 41.1% and 40.0% increases of Cu content in remediation plants H. annuus and Z. mays seedlings as compared to the values by sprinkler irrigation. Therefore, the drip irrigation enhanced the effect of intercropping on Cu phytoremediation.

Foliar spraying with a mixture of transpiration inhibitor-rhamnolipid reduces the Cd content in rice grains.

A field experiment was conducted to investigate the effectiveness and mechanisms of foliar spraying of transpiration inhibitor (TI) and different amounts of rhamnolipid (Rh) on the Cd content in rice grain. The contact angle of TI on the rice leaves was significantly reduced when it was combined with one critical micelle concentration of Rh. The Cd concentration in the rice grain in the presence of TI, TI + 0.5Rh, TI + 1Rh, and TI + 2Rh significantly decreased by 30.8 %, 41.7 %, 49.4 %, and 37.7 % respectively, compared with the control treatment. Specifically, the Cd content with TI + 1Rh was as low as 0.182 ± 0.009 mg/kg, which meets the national food safety requirements (< 0.2 mg/kg). The rice yield and plant biomass of TI + 1Rh were highest compared to the other treatments, possibly because of the alleviation of oxidative stress due to Cd. The hydroxyl and carboxyl concentrations in the soluble components in the leaf cells for the TI + 1Rh treatment were the highest compared to the other treatments. Our results demonstrated that the foliar spraying of TI + 1Rh is an efficient method to reduce Cd accumulation in rice grain. It holds potential for the future development of safe food production in soils polluted with Cd.

Comparative efficacy of Parthenium hysterophorus (L.) derived biochar and iron doped zinc oxide nanoparticle on heavy metals (HMs) mobility and its uptake by Triticum aestivum (L.) in chromite mining contaminated soils.

In this study we investigated the efficacy of a novel material parthenium weed (Parthenium hysterophorus L.) biochar (PBC), iron doped zinc oxide nanoparticles (nFe-ZnO), and biochar modified with nFe-ZnO (Fe-ZnO@BC) to adsorb heavy metals (HMs) and reduce their uptake by wheat (Triticum aestivum L.) in a highly chromite mining contaminated soil. The co-application of the applied soil conditioners exhibited a positive effect on the immobilization and restricted the HMs uptake below their threshold levels in shoot content of wheat. The maximum adsorption capacity was because of large surface area, cation exchange capacity, surface precipitation, and complexation of the soil conditioners. The scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) showed porous smooth structure of parthenium weed derived biochar that helped in HMs adsorption, increase the efficiency of soil fertilizers and nutrients retention which help in the enhancement soil condition. Under different application rates the highest translocation factor (TFHMs) was obtained at 2 g nFe-ZnO rate followed the descending order: Mn > Cr > Cu > Ni > Pb. The overall TFHMs was found <1.0 indicating that low content of HMs accumulation in roots from soil slight transferred to shoot, thus satisfying the remediation requirements.

Wheat is considered as an important staple food which is grown in a chromite mining contaminated soil containing toxic HMs releasing from weathering of mafic and ultramafic rocks in the study area. The present research work is significantly beneficial in identifying the efficiency of treatment technologies to immobilize toxic HMs in soil. Parthenium weed derived biochar and biochar modified with nFe-ZnO (Fe-ZnO@BC) reduce the HMs uptake by wheat plant.

Silver nanoparticles strengthen Zea mays against toxic metal-related phytotoxicity via enhanced metal phytostabilization and improved antioxidant responses.

This study investigated the phytostabilization and plant-promoting abilities of silver nanoparticles (AgNPs). Twelve Zea mays seeds were planted in water and AgNPs (10, 15 and 20 mg mL-1) irrigated soil for 21 days on soil containing 0.32 ± 0.01, 3.77 ± 0.03, 3.64 ± 0.02, 69.91 ± 9.44 and 13.17 ± 0.11 mg kg-1 of As, Cr, Pb, Mn and Cu, respectively. In soil treated with AgNPs, the metal contents were reduced by 75%, 69%, 62%, 86%, and 76%. The different AgNPs concentrations significantly reduced accumulation of As, Cr, Pb, Mn, and Cu in Z. mays roots by 80%, 40%, 79%, 57%, and 70%, respectively. There were also reductions in shoots by 100%, 76%, 85%, 64%, and 80%. Translocation factor, bio-extraction factor and bioconcentration factor demonstrated a phytoremediation mechanism based on phytostabilization. Shoots, roots, and vigor index improved by 4%, 16%, and 9%, respectively in Z. mays grown with AgNPs. Also, AgNPs increased antioxidant activity, carotenoids, chlorophyll a and chlorophyll b by 9%, 56%, 64%, and 63%, respectively, while decreasing malondialdehyde contents in Z. mays by 35.67%. This study discovered that AgNPs improved the phytostabilization of toxic metals while also contributing to Z. mays' health-promoting properties.

Enhanced phytoremediation strategies, which use nanoparticles to boost and facilitate the phytoremediation capacity of plants, are being recommended due to the limitations of traditional phytoremediation employing hyperaccumulating plants alone. Nanoparticles enhance phytoremediation potentials by directly reducing phytoavailable pollutants and promoting plant growth. Silver nanoparticles (AgNPs) are recognized as possessing the ability to enhance the phytoremediation of heavy metals HMs by converting them to a less toxic form and immobilizing the remaining phytoavailable HMs. This is in addition to their potential to modify plant biochemical and physiological properties to counteract HM toxicity.