Fungal endophytes have been characterized as producers of phytohormones and potent promoters of plant growth. In this study, two fungal endophytes, Fusarium tricinctum RSF-4L and Alternaria alternata ...RSF-6L, were isolated from the leaves of Solanum nigrum. Culture filtrates (CFs) from each isolate were initially screened for indole compounds, and assayed for their ability to promote the growth of Dongjin rice plants. Nearly all plant growth attributes examined (i.e., chlorophyll content, root-shoot length, and biomass production) were significantly enhanced upon treatment with fungal CFs. Subsequently, gas chromatography/mass spectrometry analyses were utilized to confirm the presence of phytohormones in the CF of each fungal endophytic isolate. These analyses revealed that RSF-4L and RSF-6L produced 54 and 30 µg/mL indole acetic acid, respectively, within their respective cultures. These findings suggest that the endophytes isolated in this study synthesize bioactive compounds that could play important roles in promoting plant growth.
This study aimed to investigate the combined ecotoxicological effects of Cd, Pb, Zn, Hg and regulation mechanisms in Solanum nigrum L. In this work, the co-exposure of these four heavy metals ...hindered the transformation of Cd, Zn, and Hg (except Pb) from available to non-available chemical forms. Individual Cd, Pb, Zn and Hg induced the oxidative damages to S. nigrum L., while their combination further enhanced this ecological toxicity. By internal regulation, the ecological toxicity of metals to S. nigrum L. could be alleviated to a certain extent. Specifically, S. nigrum L. was a hyperaccumulator of Cd with BCF ＞1. Moreover, since BCFroot of Pb, Zn and Hg were all greater than BCFshoot, S. nigrum L. could accumulate Pb, Hg and Zn mainly in plant roots, which was beneficial for the detoxification of plants. Meanwhile, the immobilization by cell wall (the proportions of Cd, Pb, Zn and Hg in the cell wall were 54.46–84.92%, 38.33–49.25%, 48.38–56.19% and 45.97–63.47% in low metal concentration treatments) and the sequestration in vacuole (the proportions of Cd, Pb, Zn, and Hg in the soluble fractions are 50.99–59.00%, 41.05–45.46%, 37.54–61.04% and 33.47–61.35% in high metal concentration treatments) also act as important detoxification pathways. The external regulation was mainly the changes of soil microbial communities influenced by plants. Specifically, the richness and diversity of bacteria in rhizosphere soil were increased, and roots of S. nigrum L. recruited some potentially beneficial microbials. This study provided a theoretical basis and guidance for S. nigrum L. as a phytoremediation plant under combined heavy metal pollution.
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•Available forms of Cd, Zn and Hg increased in the combined pollution soil.•S. nigrum L. could fix Pb, Hg and Zn in plant roots through stabilization strategy.•Cell wall immobilization and vacuole sequestration act as detoxification pathways.•S. nigrum L. roots could recruit some potentially beneficial microbials.
Rare earth elements (REEs) are important to enhance agricultural productivity. The utilization of phytoremediation as a green technology for addressing heavy metal (HMs) contamination in soil and ...wastewater has gained significant attention. In our research, we conducted indoor hydroponic experiments to examine the impacts of lanthanum (La) on the growth and enrichment capacity of Solanum nigrum L. (S. nigrum). S. nigrum was cultivated in 10 mg·L−1 of cadmium (Cd), 25 mg·L−1 of lead (Pb), and a mixture of both (5 mg·L−1 Cd + 15 mg·L−1 Pb). Additionally, S. nigrum were subjected to foliar spray or hydroponic supplementation of La(III). The treatment with La(III) significantly increased total fresh weight by 17.82 % to 42.20 %, compared to the treatment without La(III). Furthermore, La(III) facilitated the endocytosis of roots and enhanced Cd2+ flux ranging from 15.64 % to 75.99 % when compared to the treatment without La(III). Foliar and hydroponic application of La(III) resulted in an increase in the translocation factors (TF) in plants of Cd and Pb compared to treatments without La(III). These findings can offer valuable insights into the potential of La(III) to enhance the phytoremediation of soil or wastewater polluted with compounds.
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•La(III)-induced endocytosis promoted non-selective uptake of cadmium and lead by Solanum nigrum L.•La(III) alleviated the damage of cadmium and lead to Solanum nigrum L.•Appropriate concentration of La(III) can improve the remediation efficiency of Solanum nigrum L. against cadmium and lead.
The isotopic fractionation could contribute to understanding the Cd accumulation mechanisms in plant species. However, there are few of systematical investigations with regards to the Cd isotope ...fractionation in hyperaccumulator plants. The Cd tolerant Ricinus communis and hyperaccumulator Solanum nigrum were cultivated in nutrient solutions with varying Cd and EDTA concentrations. Cd isotope ratios were determined in the solution, root, stem and leaf. The two investigated plants were systematically enriched in light isotopes relative to their solutions (Δ114/110Cdplant-solution = −0.64‰ to −0.29‰ for R. communis and −0.84‰ to −0.31‰ for S. nigrum). Cd isotopes were markedly fractionated among the plant tissues. For both plant species, an enrichment in light Cd isotopes from solution to root was noted, followed by a slight depletion in light Cd isotopes from root to shoot. Noticeably, the chelation process has caused lighter Cd isotope enrichment in the root of R. communis and S. nigrum. Further, the good fits between △114/110Cdroot-plant and ln Froot (or between △114/110Cdshoot-plant and ln Fshoot) indicate that Cd isotopic signatures can be used to study Cd transportation during the metabolic process of plants. This study suggests that knowledge of the Cd isotope ratios could also provide new tool for identifying the Cd-avoiding crop cultivars.
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•R. communis and S. nigrum were enriched in light isotopes relative to solutions.•Enrichment in light Cd isotopes from solution to root and heavy Cd isotopes from root to shoot.•Chelation process caused lighter Cd isotope enrichment in roots of R. communis and S. nigrum.•Cd isotopic signatures can be used to study Cd transportation during plants metabolic process.
The chelation process caused lighter Cd isotope enrichment in the root of R. communis and S. nigrum.
Plant litter decomposition is a natural pathway of heavy metal cycling in soil ecosystems, but the dynamics of heavy metal release during litter decomposition are relatively poorly understood. The ...purpose of this study was to investigate the effects of species, soil fauna and soil Cd addition on litter decomposition and Cd release dynamics. Therefore, we selected two plants, Solanum nigrum and S. lycopersicum with large differences in Cd accumulation capacity. First, they were enriched with Cd during the growing period and leaf litter was harvested after 6 months of pretreatment. Then, the decomposition of leaf litter was conducted with or without soil Cd and Eisenia fetida through lab pot tests. Our results showed that leaf litter Cd led to a significant decrease in litter decomposition rate (K value), with a maximum decrease of 32.1% in S. nigrum and 30.1% in S. lycopersicum. We observed that the presence of E. fetida significantly increased K value, but the effect was similar in the +leaf Cd treatment and the -leaf Cd treatment, both for S. nigrum and S. lycopersicum. Interestingly, the litter Cd concentration did not decrease during decomposition, but showed an increasing trend, especially for S. nigrum in the +soil Cd treatment. Moreover, the litter Cd remains was higher in the +soil Cd treatment compared to the -soil Cd treatment for both S. nigrum and S. lycopersicum, no matter whether with or without E. fetida. This result suggests that the Cd may be transferred from soil to litter, thus increasing the litter Cd remains. Overall, our study shows that leaf litter Cd slowed down the carbon cycling in ecosystems. In addition, the release of litter Cd has a lag, and the litter has a certain adsorption capacity for soil Cd, which intensifies the harm to the ecology during litter transfer.
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•The E. fetida alleviated the inhibition effect of leaf Cd on decomposition.•Soil Cd increased the leaf litter Cd remains, which slowed down the leaf Cd release.•Leaf Cd increased lignin and cellulose content and slowed down decomposition.•The lag of leaf Cd release increases the risk of Cd pollution after litter transfer.
Microorganism or chelate-assisted phytoextraction is an effective remediation tool for heavy metal polluted soil, but investigations into its impact on soil microbial activity are rarely reported. ...Consequently, cadmium (Cd)- and lead (Pb)-resistant fungi and citric acid (CA) were introduced to enhance phytoextraction by Solanum nigrum L. under varied Cd and Pb pollution levels in a greenhouse pot experiment. We then determined accumulation of Cd and Pb in S. nigrum and the soil enzyme activities of dehydrogenase, phosphatase, urease, catalase, sucrase, and amylase. Detrended canonical correspondence analysis (DCCA) was applied to assess the interactions between remediation strategies and soil enzyme activities. Results indicated that the addition of fungi, CA, or their combination enhanced the root biomass of S. nigrum, especially at the high-pollution level. The combined treatment of CA and fungi enhanced accumulation of Cd about 22–47 % and of Pb about 13–105 % in S. nigrum compared with the phytoextraction alone. However, S. nigrum was not shown to be a hyperaccumulator for Pb. Most enzyme activities were enhanced after remediation. The DCCA ordination graph showed increasing enzyme activity improvement by remediation in the order of phosphatase, amylase, catalase, dehydrogenase, and urease. Responses of soil enzyme activities were similar for both the addition of fungi and that of CA. In summary, results suggest that fungi and CA-assisted phytoextraction is a promising approach to restoring heavy metal polluted soil.
The efficacy of using plants to phytoremediate heavy metal (HM) contaminated soils can be improved using soil amendments. These amendments may both increase plant biomasses and HMs uptake. We aimed ...to determine the composite effect of ammonium sulfate ((NH4)2SO4) combined with the application of an aqueous stem-extracted bio-chelator (Bidens tripartita L) on the plant biomasses and cadmium (Cd) phytoextraction by Solanum nigrum L. The constant (NH4)2SO4 application mode plus bio-chelator additives collectively enhanced the shoot Cd extraction ability owing to the increased plant biomass and shoot Cd concentration by S. nigrum. The shoot Cd extraction and the soil Cd decreased concentration confirmed the optimal Cd phytoextraction pattern in K8 and K9 treatments (co-application of (NH4)2SO4 and twofold/threefold bio-chelators). Accordingly, Cd contamination risk in the soil (2 mg kg−1) could be completely eradicated (<0.2 mg kg−1) after three rounds of phytoremediation by S.nigrum based on K8 and K9 treatments through calculating soil Cd depletion. The microorganism counts and enzyme activities in rhizosphere soils at treatments with the combined soil additives apparently advanced. In general, co-application mode of (NH4)2SO4 and aqueous bio-chelator was likely to be a perfect substitute for conventional scavenger agents on account of its environmental friendliness and cost saving for field Cd contamination phytoremediation by S. nigrum.
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•◆Co-application of (NH4)2SO4 and bio-chelator was more effective than alone.•◆K8 and K9 treatments achieved the optimal Cd phytoextraction pattern.•◆The microorganism counts and enzyme activities advanced most for K8 and K9.•◆2 mg kg−1 Cd pollution could be removed after three rounds of phytoremediation.
A novel technology to obtain highly efficient biosorbent from the endophytes of a hyperaccumulator is reported. This technology is more convenient than the traditional method of obtaining biosorbents ...by experimentally screening many types of biomass by trial and error. Using this technology, endophytic fungus (EF) LSE10 was isolated from the cadmium hyperaccumulator
Solanum nigrum L
. It was identified as
Microsphaeropsis sp. When cultured in vitro, the biomass yield of this EF was more than twice that of none-endophytic fungus (NEF)
Rhizopus cohnii. Subsequently, it was used as a biosorbent for biosorption of cadmium from the aqueous solution. The results showed that the maximum biosorption capacity was 247.5
mg/g (2.2
mmol/g) which was much higher than those of other adsorbents, including biosorbents and activated carbon. Carboxyl, amino, sulphonate and hydroxyl groups on EF LSE10 surface were responsible for the biosorption of cadmium.
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.
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•Appropriate foliar dosage of La(III) promoted the growth and biomass of S. nigrum.•La(III) enhanced endocytosis in the root cells of S. nigrum.•Hydroponic experiments with Cd showed La treatment enhanced phytoremediation potential.
Hyperaccumulators are ideal plant species used for phytoremediation of soils contaminated by heavy metals. A full understanding of metal tolerance mechanisms of hyperaccumulators will facilitate ...enhancing their phytoremediation efficiency. However, how Cd affects N metabolism and which role plays the response of N metabolism to Cd toxicity in the tolerance of hyperaccumulators are still unknown. To clarify these questions, this study investigated the effects of various soil Cd levels on the concentrations of N forms and the activity of key enzymes involved in N metabolism in leaves of the Cd hyperaccumulator,
Solanum nigrum L. The results showed that its growth and all N metabolism indicators were normal at low Cd exposure (≤12
mg
kg
−1). At 24
mg
Cd
kg
−1 soil, nitrate assimilation indicators (nitrate concentration and activity of nitrate reductase) were reduced significantly, whereas most ammonia assimilation indicators (ammonium concentration and activity of glutamine synthetase) remained normal. However, when exposed to a higher Cd level (48
mg
kg
−1), growth and most N metabolism indicators were reduced significantly. Therefore, N metabolism in leaves of
S. nigrum could be tolerant of Cd toxicity to a certain extent (soil Cd concentration ≤12
mg
kg
−1), and this might be involved in the Cd-tolerance of this Cd-hyperaccumulator.
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