Conjoint analysis of physio-biochemical, transcriptomic, and metabolomic reveals the response characteristics of solanum nigrum L. to cadmium stress.

Cadmium (Cd) is a nonessential element in plants and has adverse effects on the growth and development of plants. However, the molecular mechanisms of Cd phytotoxicity, tolerance and accumulation in hyperaccumulators Solanum nigrum L. has not been well understood. Here, physiology, transcriptome, and metabolome analyses were conducted to investigate the influence on the S. nigrum under 0, 25, 50, 75 and 100 µM Cd concentrations for 7 days. Pot experiments demonstrated that compared with the control, Cd treatment significantly inhibited the biomass, promoted the Cd accumulation and translocation, and disturbed the balance of mineral nutrient metabolism in S. nigrum, particularly at 100 µM Cd level. Moreover, the photosynthetic pigments contents were severely decreased, while the content of total protein, proline, malondialdehyde (MDA), H2O2, and antioxidant enzyme activities generally increased first and then slightly declined with increasing Cd concentrations, in both leaves and roots. Furthermore, combined with the previous transcriptomic data, numerous crucial coding-genes related to mineral nutrients and Cd ion transport, and the antioxidant enzymes biosynthesis were identified, and their expression pattern was regulated under different Cd stress. Simultaneously, metabolomic analyses revealed that Cd treatment significantly changed the expression level of many metabolites related to amino acid, lipid, carbohydrate, and nucleotide metabolism. Metabolic pathway analysis also showed that S. nigrum roots activated some differentially expressed metabolites (DEMs) involved in energy metabolism, which may enhance the energy supply for detoxification. Importantly, central common metabolism pathways of DEGs and DEMs, including the "TCA cycle", "glutathione metabolic pathway" and "glyoxylate and dicarboxylate metabolism" were screened using conjoint transcriptomics and metabolomics analysis. Our results provide some novel evidences on the physiological and molecular mechanisms of Cd tolerance in hyperaccumulator S. nigrum plants.

Bioactivities and chemical profiling comparison and metabolomic variations of polyphenolics and steroidal glycoalkaloids in different parts of Solanum nigrum L.

INTRODUCTION: Solanum nigrum L. is a traditional medicinal herb and edible plant. Many studies provide evidence that S. nigrum L. is a nutritious vegetable. Polyphenols and steroidal glycoalkaloids are the main components. OBJECTIVES: This study aimed to systemically evaluate the phytochemical profile, quantification, and bioactivities of polyphenolics and glycoalkaloids in different parts of S. nigrum L. RESULTS: Total polyphenols (TPC) and total glycoalkaloids (TGK) were determined using the Folin-Ciocalteu and acid dye colorimetric methods, respectively. A total of 55 polyphenolic constituents (including 22 phenolic acids and 33 flavonoids) and 24 steroidal glycoalkaloids were identified from different parts using ultrahigh-performance liquid chromatography Q-exactive high-resolution mass spectrometry (UHPLC-QE-HRMS), of which 40 polyphenols (including 15 phenolic acids and 25 flavonoids) and one steroidal glycoalkaloid were characterised for the first time in S. nigrum L. Moreover, typical polyphenols and glycoalkaloids were determined using HPLC-UV and HPLC-evaporative light-scattering detector (ELSD), respectively. In addition, the TPC and TGK and their typical constituents were compared in different anatomical parts. Finally, the antioxidant capacities of polyphenolic extracts from different parts of S. nigrum L. were evaluated by ·OH, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and ferric-reducing antioxidant power (FRAP) assay in vitro. In addition, the antitumour effects of TGK from different parts of S. nigrum L. on the proliferation of PC-3 cells were investigated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Polyphenolic and glycoalkaloid extracts from different parts of S. nigrum L. showed different antioxidant and cytotoxic capacities in vitro. CONCLUSION: This is the first study to systematically differentiate between polyphenolic and glycoalkaloid profiles from different parts of S. nigrum L.

Molecular Characterization and Pathogenicity of an Infectious cDNA Clone of Youcai Mosaic Virus on Solanum nigrum.

Virus infections cause devastative economic losses for various plant species, and early diagnosis and prevention are the most effective strategies to avoid the losses. Exploring virus genomic evolution and constructing virus infectious cDNA clones is essential to achieve a deeper understanding of the interaction between host plant and virus. Therefore, this work aims to guide people to better prevent, control, and utilize the youcai mosaic virus (YoMV). Here, the YoMV was found to infect the Solanum nigrum under natural conditions. Then, an infectious cDNA clone of YoMV was successfully constructed using triple-shuttling vector-based yeast recombination. Furthermore, we established phylogenetic trees based on the complete genomic sequences, the replicase gene, movement protein gene, and coat protein gene using the corresponding deposited sequences in NCBI. Simultaneously, the evolutionary relationship of the YoMV discovered on S. nigrum to others was determined and analyzed. Moreover, the constructed cDNA infectious clone of YoMV from S. nigrum could systematically infect the Nicotiana benthamiana and S. nigrum by agrobacterium-mediated infiltration. Our investigation supplied a reverse genetic tool for YoMV study, which will also contribute to in-depth study and profound understanding of the interaction between YoMV and host plant.

Effects of N, N-bis (carboxymethyl)-L-glutamic acid and polyaspartic acid on the phytoremediation of cadmium in contaminated soil at the presence of pyrene: Biochemical properties and transcriptome analysis.

Chelator-assisted phytoremediation is an efficacious method for promoting the removal efficiency of heavy metals (HMs). The effects of N, N-bis(carboxymethyl)-L-glutamic acid (GLDA) and polyaspartic acid (PASP) on Cd uptake and pyrene removal by Solanum nigrum L. (S. nigrum) were compared in this study. Using GLDA or PASP, the removal efficiency of pyrene was over 98%. And PASP observably raised the accumulation and transport of Cd by S. nigrum compared with GLDA. Meanwhile, both GLDA and PASP markedly increased soil dehydrogenase activities (DHA) and microbial activities. DHA and microbial activities in the PASP treatment group were 1.05 and 1.06 folds of those in the GLDA treatment group, respectively. Transcriptome analysis revealed that 1206 and 1684 differentially expressed genes (DEGs) were recognized in the GLDA treatment group and PASP treatment group, respectively. Most of the DEGs found in the PASP treatment group were involved in the metabolism of carbohydrates, the biosynthesis of brassinosteroid and flavonoid, and they were up-regulated. The DEGs related to Cd transport were screened, and ABCG3, ABCC4, ABCG9 and Nramp5 were found to be relevant with the reduction of Cd stress in S. nigrum by PASP. Furthermore, with PASP treated, transcription factors (TFs) related to HMs such as WRKY, bHLH, AP2/ERF, MYB were down-regulated, while more MYB and bZIP TFs were up-regulated. These TFs associated with plant stress resistance would work together to induce oxidative stress. The above results indicated that PASP was more conducive for phytoremediation of Cd-pyrene co-contaminated soil than GLDA.

Analysis of steroidal glycoalkaloids and their metabolites in Solanum nigrum fruits based on liquid chromatography-tandem mass spectrometry and molecular networking.

Solanum nigrum fruit is like a treasure house for anticancer drugs because of its steroidal alkaloids. However, the clinical treatment of cancer mainly uses immature fruits, which can cause a toxic reaction if eaten directly, while mature fruits are eaten as fruit. In order to clarify the reasons for the differences in pharmacodynamics and toxicity between them, we studied the composition and metabolism of steroidal alkaloids in fruits of different maturities based on liquid chromatography-tandem mass spectrometry and molecular networking. As a result, 114 steroidal glycoalkaloids were identified. During fruit ripening, the aglycones of steroidal alkaloids mainly undergo hydroxylation and carboxylation, and the sugar side chains mainly undergo acylation and glycosylation reactions. Furthermore, 219 steroidal alkaloids were identified in a metabolism experiment in rats. Metabolic processes include deglycosylation, redox, sulfuric acid binding, acetyl binding, and glucuronic acid-binding. Steroidal alkaloids in mature fruits have high molecular weight and polarity, which are difficult to absorb, and most of them are excreted through feces and urine, which may be the reason for their poor efficacy. This study lays a foundation for research on the biosynthesis of steroidal alkaloids and provides potential candidates for the discovery of new steroidal alkaloid anticancer drugs.

Total steroidal saponins from black nightshade (Solanum nigrum L.) overcome tumor multidrug resistance by inducing autophagy-mediated cell death in vivo and in vitro.

Multiple drug resistance (MDR) often occurs after prolonged chemotherapy, leading to refractory tumors and cancer recurrence. In this study, we demonstrated that the total steroidal saponins from Solanum nigrum L. (SN) had broad-spectrum cytotoxic activity against various human leukemia cancer cell lines, especially in adriamycin (ADR)-sensitive and resistant K562 cell lines. Moreover, SN could effectively inhibit the expression of ABC transporter in K562/ADR cells in vivo and in vitro. In vivo, by establishing K562/ADR xenograft tumor model, we demonstrated that SN might overcome drug resistance and inhibit the proliferation of tumors by regulating autophagy. In vitro, the increased LC3 puncta, the expression of LC3-II and Beclin-1, and the decreased expression of p62/SQSTM1 in SN-treated K562/ADR and K562 cells demonstrated autophagy induced by SN. Moreover, using the autophagy inhibitors or transfecting the ATG5 shRNA, we confirmed that autophagy induced by SN was a key factor in overcoming MDR thereby promoting cell death in K562/ADR cells. More importantly, SN-induced autophagy through the mTOR signaling pathway to overcome drug resistance and ultimately induced autophagy-mediated cell death in K562/ADR cells. Taken together, our findings suggest that SN has the potential to treat multidrug-resistant leukemia.

Foliar application of lanthanum promotes growth and phytoremediation potential Solanum nigrum L.

The hormetic effect of rare earth elements (REEs) has been found in a variety of crops and has been promoting crop growth for decades. Spraying leaves with REEs can enhance the endocytosis of plant roots. The non-selectivity of endocytosis is conducive to the direct absorption of environmental pollutants. The hyperaccumulator Solanum nigrum L. (S. nigrum), as a plant with high biomass and heavy metal tolerance, is a good candidate for phytoremediation. La(III), as a typical light REE, also has an obvious hormetic effect on S. nigrum. At 10 µM La(III), the biomass of S. nigrum reached the maximum, which was 89% greater than the control, and La(III) concentration was much lower than the previously reported optimum of 56 µM for general plants. In the present study, enhanced endocytosis after foliar spraying of La(III) was firstly observed in the root cell of hyperaccumulation plants, and La(III) increased the biomass of S. nigrum by improving the photosynthetic system, and promoting nutrient uptake and root development. The antioxidant defense system improved by La(III) contributed to the tolerance of S. nigrum to heavy metals. Applying a reasonable range of La(III) is beneficial to improving S. nigrum growth and tolerance of heavy metals. Compared with spraying deionized water, the translocation factor and bioaccumulation factor value of S. nigrum to cadmium increased by 15% and 21% respectively when spraying 10 µM La(III). Our findings provide a reference for improving hyperaccumulator plant growth and biomass, which improves phytoremediation efficiency.

Anti-Colorectal Cancer Activity of Solasonin from Solanum nigrum L. via Histone Deacetylases-Mediated p53 Acetylation Pathway.

(1) Background: Solanum nigrum L. is a plant of the genus Solanum in the family Solanaceae and is commonly used to treat tumors. Solasonin (SS) is a steroidal alkaloid extracted from Solanum nigrum L. that has anti-colorectal cancer (CRC) activity. (2) Methods: Column chromatography, semi-preparative HPLC and cellular activity screening were used to isolate potential anti-CRC active compounds in Solanum nigrum L., and structure identification using 1H-NMR and 13C-NMR techniques. Expression levels of HDAC in CRC were mined in the UALCAN database. The in vitro effects of SS on SW620 cell line and its mechanism were examined via Western blot, EdU staining, flow cytometry and immunofluorescence. CRC xenograft model and IHC staining were mainly used to evaluate the role of SS in vivo. (3) Results: The results showed that SS was the most potent anti-CRC component in Solanum nigrum L., which induced apoptosis and cell cycle arrest in the SW620 cell line. HDAC was highly expressed in CRC. The treatment of SW620 cell line with SS resulted in a significant downregulation of HDAC, an increase in the level of P53 acetylation and a subsequent increase in the level of P21. The in vivo validation results showed that SS could effectively inhibit CRC growth, which was associated with the downregulation of HDAC. (4) Conclusions: SS treatment for CRC mainly works through the induction of apoptosis and cycle arrest, and its mechanism of action is mainly related to HDAC-induced P53 acetylation, and the HDAC/P53 signaling pathway may be a potential pathway for the treatment of CRC.

Attenuation of CFA-induced arthritis through regulation of inflammatory cytokines and antioxidant mechanisms by Solanum nigrum L. leaves extracts.

Solanum nigrum L. is a popular traditional medicine for various inflammatory conditions including rheumatism and joint pain. The current study aimed to evaluate the anti-arthritic mechanism of Solanum nigrum L. Four extracts were prepared using n-hexane, methanol, chloroform, and water. The anti-nociceptive and anti-inflammatory activity was carried out with 100, 200, and 300 mg/kg body wt. PO of each extract by the hot plate and carrageenan-induced paw oedema methods, respectively. The anti-arthritic study was performed with chloroform and aqueous extracts (300 mg/kg) in complete Freund's adjuvant (CFA)-induced arthritis. Paw size (mm), ankle joint diameter (mm), and latency time (sec) were recorded on day 0 and every 4th day till 28 days. The hematological, inflammatory, and oxidative biomarkers were estimated. Results showed that significant analgesia (p < 0.05) and reduction in paw inflammation were achieved with all extracts. The highest percent inhibition in Carrageenan-induced inflammation was achieved with 300 mg/kg of chloroform (72.19%) and aqueous (71.30%) extracts, respectively. In the CFA model, both extracts showed a significant reduction in paw size and ankle joint diameter (p < 0.05). The RT-qPCR analysis revealed the upregulation of interleukin-4 and interleukin-10, and down-expression of interleukin-1ß, interleukin-6, tumor necrosis factor-α, cycloxygenase-2, nuclear factor-κB, prostaglandin E synthase 2, and interferon-γ. A significant increase in superoxide dismutase, catalase, and glutathione levels was observed. Hence, it is concluded that Solanum nigrum L. leaf extracts regulate the expression of inflammatory markers and improve oxidative stress resulting in the attenuation of CFA-induced arthritis.

Citric Acid and Poly-glutamic Acid Promote the Phytoextraction of Cadmium and Lead in Solanum nigrum L. Grown in Compound Cd-Pb Contaminated Soils.

Phytoextraction is an efficient strategy for remediating heavy metal-contaminated soil. Chelators can improve the bioavailability of heavy metals and increase phytoextraction efficiency. However, traditional chelators have gradually been replaced due to secondary pollution. In this study, a typical organic acid (citric acid, CA) and a novel biodegradable chelator (poly-glutamic acid, PGA), were investigated using pot experiments to compare the phytoextraction efficiency of Solanum nigrum L. (a Cd (hyper)accumulator) for cadmium (Cd) and lead (Pb) in contaminated soil. The results showed CA and PGA significantly improved plant growth, and total Cd and Pb amounts of S. nigrum, both CA and PGA significantly increased the shoot Cd and Pb concentrations. However, only PGA significantly increased the root Pb concentration. CA and PGA application promoted the bioavailability of Cd and Pb in rhizosphere soils and their translocations from roots to shoots in S. nigrum. Both CA and PGA increased the phytoextraction efficiency of Cd and Pb in S. nigrum plants, and the PGA for Cd and Pb phytoextraction was more effective than CA. Our findings demonstrate that the biodegradable chelator PGA has great potential for enhancing phytoextraction from compound Cd-Pb contaminated soils, suggesting that biodegradable chelator-assisted phytoextraction with (hyper)accumulator is strongly recommended in severely contaminated sites.

Exogenous melatonin improves cadmium tolerance in Solanum nigrum L. without affecting its remediation potential.

Although Solanum nigrum L. is a phytoremediator for different metals, its growth and physiology are still influenced by toxic levels of cadmium (Cd). Thus, the development of eco-friendly strategies to enhance its tolerance, maintaining remediation potential is of special interest. The present work aimed to evaluate the effects of exogenous application of melatonin (MT) in the physiological and biochemical responses of S. nigrum and remediation potential exposed to Cd. After 30 days of exposure, the results revealed that Cd-mediated inhibitory effects on biomass and photosynthetic pigment synthesis were efficiently mitigated upon application of melatonin, without affecting Cd accumulation. Higher levels of Cd were found in roots, regardless of the pretreatment with the melatonin. Foliar application of melatonin, however, induced distinctive effects, lowering malondialdehyde (MDA), relative electrical conductivity (REL), and proline levels in shoots. These changes contributed to improvements in the water status, photosynthetic pigment synthesis, and biomass production of S. nigrum under Cd stresses. Overall, our results indicate a protective effect of melatonin on S. nigrum response to excess Cd, contributing to a better tolerance and growth rate, without disturbing its phytoremediation potential.Novelty statementAlthough Solanum nigrum L. is a phytoremediator for different metals, its growth and physiology are still influenced by toxic levels of cadmium. This study evaluated the potential of melatonin to boost S. nigrum defence against Cd toward a better growth rate and remediation potential.

The effects of different electrode materials on seed germination of Solanum nigrum L. and its Cd accumulation in soil.

The effects of different electrode on Solanum nigrum L. seed germination were determined. The result showed that germination percentage (GP) of seeds in treatment T2 (titanium electrode) was 26.6% higher than in control (CK, without electric field). High potassium and calcium concentrations were beneficial for seed enzymatic activity in treatment T2, which could partly explain the increase in GP. Cd accumulation (µg/pot) in S. nigrum treated with any electric field was significantly higher (p<0.05) than in CK without electric field. Specifically, Cd accumulation under the treatment T3 (stainless steel electrode) was the highest both in roots and shoots; this accumulation in shoots and roots were 74.7 % and 67.4 % higher for stainless steel than in CK. This increase must have been associated with a higher Cd concentration in plants and did not exert a significant effect on the biomass. In particular, Cd concentrations in roots and shoots under stainless steel treatment were both significantly higher than in CK (p<0.05), which had to be related to the higher available Cd concentration in the soil in the middle region. Furthermore, it could be attributed to altered soil pH and other soil properties. Moreover, none of the biomasses were significantly affected (p<0.05) by different electrode materials compared to CK.

The potential of medicinal plant extracts in improving the phytoremediation capacity of Solanum nigrum L. for heavy metal contaminated soil.

This study focused on the effects of eight medicinal plant extracts on Solanum nigrum L. potential to accumulate Cd and Pb from soil. These medicinal plants were common and relatively cheap. The eight 10% water extracts were made from the peel of Citrus reticulata Blanco (PCR), fruit of Phyllanthus emblica L. (FPE), root of Pueraria Lobata (Willd.) Ohwi (RPL), rhizome of Polygonatum sibiricum Red (RPS), root of Astragalus propinquus Schischkin (RAP), bud of Hemerocallis citrina Baroni (BHC), seed of Nelumbo nucifera Gaertn (SNN) and fruit of Prunus mume (Sieb.) Sieb.etZuce (FPM). The results showed that among all exposures, the treatment with FPE resulted in the significant increase (p < 0.05) of Cd and Pb concentration in shoots and roots of S. nigrum by 32.5% and 65.2% for Cd, and 38.7% and 39.6% for Pb. The biomasses of S. nigrum in all plant extract treatments were not significantly changed (p < 0.05) compared to the control (CK). The Cd and Pb extraction rates of S. nigrum in FPE treatment were increased respectively by 60.5% and 40.5% compared to CK. Though the treatment with EDTA significantly improved (p < 0.05) the concentration of Cd and Pb of S. nigrum, the Cd and Pb masses (ug plant-1) of S. nigrum did not show any significant difference compared to the CK due to the significant decrease in the shoot (20.4%) and root (22.0%) biomasses. The chelative role of FPE might be relation with its higher polyphenolic compounds. However, not sure if the contents of polyphenolic compounds was the only differences between FPE and other additives. Thus, some unknown organic matters might also play active role. This study provided valuable information on improving the phytoremediation potential of hyperaccumulator.

Biosorption capacity of Mucor circinelloides bioaugmented with Solanum nigrum L. for the cleanup of lead, cadmium and arsenic.

The biosorption and bioaugmentation performances of Mucor circinelloides were investigated under different contact time, initial metal(loid) concentration and species. The microbe-plant interaction appeared synergistic with enhancing plant growth and alleviating oxidative damages induced by lead, cadmium and arsenic. The bioaugmentation with M. circinelloides led to significant immobilization on lead, cadmium and arsenic as indicated by the decreases of metal(loid) transfer and bioavailability in plant-microbe aqueous system. Lead, cadmium and arsenic were mainly allocated on cell wall and a few parts entered into intercellular system, suggesting cell wall adsorption and intracellular bioaccumulation served as the main mechanisms of M. circinelloides. The adsorption kinetics and isotherms on lead, cadmium and arsenic were fitted well with the pseudo-second-order and Langmuir models, with the maximum adsorption capacities of 500, 15.4 and 29.4 mg·g-1 fungal biomass at pH 6.0 and 25 â„ƒ. The optimum initial concentration and contact time were 300-10-20 mg·L-1 and 2 h. This study provides a basis for M. circinelloides as a promising adsorbent and bioaugmented agent for the cleanup of soil/aqueous environment contaminated with lead, cadmium and arsenic.

Enhanced biomass and cadmium accumulation by three cadmium-tolerant plant species following cold plasma seed treatment.

Cold plasma seed treatment can promote plant growth and enhance the resistance of agricultural crops to adverse stress. However, the effects of plasma seed treatment on the growth and phytoextraction response of plants to cadmium (Cd) remain poorly documented. Here, we have investigated the feasibility of using plasma seed treatment to enhance the biomass and Cd accumulation of three Cd-tolerant species, namely Bidens pilosa L, Solanum nigrum L. and Trifolium repens L, under different plasma treatment conditions. Possible enhancement mechanisms are also proposed according to the levels of organic acids in the roots and the Cd fractions in rhizosphere soil following different plasma treatment conditions. The optimum plasma power was 100 W (B. pilosa) or 500 W (S. nigrum and T. repens). The optimum plasma exposure time for all three species was 60 s. Plasma seed treatment under the optimum treatment conditions enhanced plant dry biomass by ~17.3-45.0% and Cd accumulation by 8.8-54.4% across all three species compared to the controls. Furthermore, the phytoremediation efficiencies, bioaccumulation factors and transfer factors of the three species also increased significantly after seed plasma treatment. The promotion of plasma treatment on the biomass and Cd accumulation of three species might be due to increased exudation of organic acids from the roots into the rhizosphere soil, thus increasing the concentrations of acid-soluble Cd to form Cd-organic acid complexes that facilitated the uptake and translocation of Cd by the plants. Results of this study revealed that cold plasma seed treatment is an environmentally friendly, economical and efficient means to develop the application of phytoremediation for Cd-contaminated soils.

Effect of Wheat-Solanum nigrum L. intercropping on Cd accumulation by plants and soil bacterial community under Cd contaminated soil.

Using accumulators for intercropping in agricultural production can change the heavy metal concentration in the target plants. This study aims to investigate how intercropping wheat (Triticum aestivum L.) and Solanum nigrum L. affects soil bacterial community and cadmium (Cd) absorption in response to Cd-contaminated soil. We compared the concentrations and accumulations of Cd by plants, the activities of soil enzymes and the bacterial community structures of rhizosphere soil in monoculture and intercropping system. Principal component analysis (PCA) ordinations showed that soil bacterial communities were significantly separated by MW and IW, which illustrated intercropping with Solanum nigrum L. impacted the bacterial community structure of wheat. Firstly, the results showed that the biomass of shoots and roots in intercropped wheat (IW) were significantly decreased by 16.19% and 29.38% compared with monoculture wheat (MW) after 60 days after transplanting (DAT). Secondly, the Cd concentration and accumulation of shoots in IW was higher than MW. The Cd accumulation of IW shoots and roots were increased 12.87% and 0.98%, respectively after 60 days DAT. Besides, the enzymes activity [catalase (CAT), urease (UA) and alkaline phosphatase (ALP)] of IW were decreased 35%, 6% and 21%, respectively after 60 days DAT. Finally, the diversity indexes [Abundance-based Coverage Estimator (ACE), Chao and InvSimpson] of IW were lower than MW. These results indicated that intercropping with Solanum nigrum L. inhibited the wheat growth and decreased the bacterial community diversity in wheat rhizosphere, increased the Cd concentration and accumulation in plant tissues of wheat. Therefore, intercropping Solanum nigrum L. and wheat with Cd-contaminated soil might increase the risk of excessive Cd in wheat.

Promotion of growth and phytoextraction of cadmium and lead in Solanum nigrum L. mediated by plant-growth-promoting rhizobacteria.

Plant growth-promoting rhizobacteria (PGPR) are a specific category of microbes that improve plant growth and promote greater tolerance to metal stress through their interactions with plant roots. We evaluated the effects of phytoremediation combining the cadmium accumulator Solanum nigrum L. and two Cd- and Pb-resistant bacteria isolates. To understand the interaction between PGPR and their host plant, we conducted greenhouse experiments with inoculation treatments at Nanjing Agricultural University (Jiangsu Province, China), in June 2018. Two Cd- and Pb-resistant PGPR with various growth-promoting properties were isolated from heavy metal-contaminated soil. 16S rRNA analyses indicated that the two isolates were Bacillus genus, and they were named QX8 and QX13. Pot experiments demonstrated that inoculation may improve the rhizosphere soil environment and promote absorption of Fe and P by plants. Inoculation with QX8 and QX13 also enhanced the dry weight of shoots (1.36- and 1.7-fold, respectively) and roots (1.42- and 1.96-fold) of plants growing in Cd- and Pb-contaminated soil, and significantly increased total Cd (1.28-1.81 fold) and Pb (1.08-1.55 fold) content in aerial organs, compared to non-inoculated controls. We also detected increases of 23% and 22% in the acid phosphatase activity of rhizosphere soils inoculated with QX8 and QX13, respectively. However, we did not detect significant differences between inoculated and non-inoculated treatments in Cd and Pb concentrations in plants and available Cd and Pb content in rhizosphere soils. We demonstrated that PGPR-assisted phytoremediation is a promising technique for remediating heavy metal-contaminated soils, with the potential to enhance phytoremediation efficiency and improve soil quality.

Potential of enhancing the phytoremediation efficiency of Solanum nigrum L. by earthworms.

Contamination of the soil by Cadmium (Cd) is emerged as a critical environmental problem in China due to current urbanization and industrial activities that hinder the sustainable future development of agriculture. In this study, a system combined by earthworm and Solanum nigrum L. (S. nigurm) was designed for remediation of Cadmium from contaminated soils. The present study revealed that application of earthworm enhanced the biomass of S. nigrum by 61.71%, maxim; the Cd concentrations in the aboveground part of S. nigrum enhanced 35.8% when 50 g earthworm was added into each pot; the addition of earthworm also have some effect on the bio-concentration factor (BF) of S. nigrum while no effect was detected on the bio-transfer factor (TF). In addition, considering the accumulation of Cd by earthworm, the total amount of Cd extracted by the combined system enhanced 57.7% at least and 264.6% at the most, compared to the Cd extraction amount of S. nigrum alone. Generally, according to this study, the earthworm-S. nigrum system has the potential to be used for the remediation of Cd contaminated soils.

Phytoremediation of multi-metal contaminated mine tailings with Solanum nigrum L. and biochar/attapulgite amendments.

A greenhouse experiment was conducted to investigate an enhanced phytoremediation technique for multi-metal contaminated mine tailings by Solanum nigrum L. and using biochar/attapulgite as soil amendments. The 10% attapulgite (MA2) and 10% biochar (MB2) were recommended as the optimum chemical proportions for amendment materials. Plant length and fresh weight in the MA2/MB2-applied treatments were significantly higher than that in the non-amended treatment, indicating MA2 and MB2 amendments could alleviate metal phytotoxicity. Metal uptake in plant leaves was lower with MA2 and MB2 application than that in the non-amended treatment. However, metal uptake in plant roots was significantly increased with MA2 and MB2 application from the fifth month, suggesting that MA2 and MB2 had significant enhancement on metal stabilization. Temporal variation of metal translocation in soil-to-plant system showed that the function of MA2 and MB2 reached the plateau nearly in the seventh month. The removal rates of metals were higher after the application of MA2 than MB2, and by the following order: Cu (39.6%) > Zn (35.0%) > Cd (34.1%) > Hg (32.1%) > Pb (31.8%) > Mn (19.1%). The synergistic effect between S. nigrum L. and MA2/MB2 appeared to be particularly effective in terms of metal phytostabilization, and MA2 was superior to MB2.

Strengthening role and the mechanism of optimum nitrogen addition in relation to Solanum nigrum L. Cd hyperaccumulation in soil.

Solanum nigrum L. has a high potential for the remediation of Cd-contaminated soil, and nitrogen fertilizer supply is an effective method to further improve its phytoremediation potential. The soil pot culture experiment was used to explore 4 kinds of nitrogen fertilizers the best fertilizer addition concentrations and their strengthening mechanisms. The results showed that S. nigrum biomass increased with increasing N doses until 800 mg kg-1, where the biomass reached maximum and no longer improved (p < 0.05). However, Cd concentration accumulated by S. nigrum and the extractable Cd concentration in soil did not show a significant decrease (p < 0.05). In this experiment, when N fertilizer was added at 800 mg kg-1 (NH4HCO3, NH4Cl, (NH4)2SO4 and CH4N2O fertilizers), the biomass of the aboveground S. nigrum parts improved to the maximum under (NH4)2SO4 and CH4N2O treatments, i.e. 5.86 g pot-1 and 5.83 g pot-1, increased by 5.92- and 5.89-fold, respectively (p < 0.05), compared to the controls without N fertilizers addition. At the same time, Cd phytoaccumulation in plants was elevated to 128.40 µg pot-1 and 129.14 µg pot-1, increased by 6.20- and 6.24-fold, respectively (p < 0.05), compared to control with no fertilizer added. The results of this experiment demonstrated that Cd phytoextraction capacity (µg pot-1) was the strongest under (NH4)2SO4 and CH4N2O treatments at N content of 800 mg kg-1, when plant nutrient recovery reached the maximum, and these 2 types of nitrogen fertilizers could be utilized to remediate Cd-contaminated soil in field experiments or even in practice.