Enhancement of cadmium uptake by Amaranthus caudatus, an ornamental plant, using tea saponin

Removal of heavy metals using Iris species: A potential approach for reclamation of heavy metal-polluted sites and environmental beautification

Globally, the number of heavy metal (HM)-polluted sites has increased rapidly in recent years, posing a serious threat to agricultural productivity, human health, and environmental safety. Hence, it is necessary to remediate HM-polluted sites to increase cultivatable lands for agricultural productivity, prevent hazardous effects to human health, and promote environmental safety. Removal of HMs using plants (phytoremediation) is a promising method as it is eco-friendly. Recently, ornamental plants have been widely used in phytoremediation programs as they can simultaneously eliminate HMs and are aesthetically pleasing. Among the ornamental plants, Iris species are frequently used; however, their role in HM remediation has not been reviewed yet. Here, the importance of Iris species in the ornamental industry and their different commercial aspects are briefly described. Additionally, the mechanisms of how the plant species absorb and transport the HMs to the above-ground tissues and tolerate HM stress are highlighted. The variation in HM remediation efficiency depending on the plant species, HM type and concentration, use of certain supplements, and experimental conditions are also discussed. Iris species are able to remove other hazards as well, such as pesticides, pharmaceutical compounds, and industrial wastes, from polluted soils or waste-water. Owing to the valuable information presented in this review, we expect more applications of the species in reclaiming polluted sites and beautifying the environment.

Assessment of tea saponin and citric acid-assisted phytoextraction of Pb-contaminated soil by Salvia virgata Jacq

The present study, investigated the influence of the natural tea saponin (TS) obtained by microwave-assisted extraction and citric acid (CA) by commercially enhancing lead ion (Pb(II)) uptake by Salvia virgata Jacq. The Pb(II) tolerance was compared, and the growth of plants and Pb(II) accumulation characteristics of S. virgata with chemical agents TS and CA were studied for their phytoextraction potential of Pb(II) from artificially contaminated soil of 0-100 mg kg^-1 different concentrations under pot conditions. The different morphophysiological parameters of S. virgata such as growth, biomass, chlorophylls, and carotenoids were significantly changed under different Pb(II) stress and TS and CA concentrations. To evaluate the removal efficiency of the studied plant, the bioconcentration factor (BCF) or enrichment coefficient (EC), translocation factor (TF), and tolerance index (TI) values were also calculated and compared with the control. Phytotoxic effects were observed at 100 mg kg^-1; added Pb(II) treatments caused significant decreases of 33.05% in the biomass of S. virgata compared to the control. All the obtained results showed that the concentrations of Pb(II) being compared revealed a highest uptake (286 ± 5.2 mg kg^-1) of 100 mg kg^-1. The concentration of available Pb(II)-assisted TS and CA increased by 9.1-28.4% compared to the control. Based on these findings, S. virgata might be cultivated and used as a hyperaccumulator in the removal of Pb(II) from the contaminated soils, and appropriate application of TS and CA can enhance phytoremediation of Pb(II)-contaminated soil by other hyperaccumulator plants.

Positive Effects and Optimal Ranges of Tea Saponins on Phytoremediation of Cadmium-Contaminated Soil

Confirming positive effects and offering optimal ranges of tea saponins on improving the efficiency of phytoremediation on cadmium is a prerequisite for applying tea saponins in field remediation. Existing studies qualitatively tested the feasibility of tea saponins on promoting the absorption of cadmium by hyperaccumulators in pots experiments, while this study investigated the effects of tea saponins on increasing the proportion of cadmium available fraction in contaminated soil quantitatively and confirmed tea saponins promoted the absorption by Portulaca oleracea in cadmium-contaminated water by independent soil experiments and hydroponic experiments. The results showed that for acquiring a higher proportion of cadmium available fraction, the concentration of tea saponins was negatively correlated with the concentration of cadmium contained in the soil, and the optimal treatment time of tea saponins was between 3–9 days depending on the cadmium concentration in contaminated soil. Using tea saponins could enhance the absorption of cadmium by Portulaca oleracea in a relatively short time to decrease the concentration of cadmium left in the contaminated water. The above findings help to deepen the understanding of tea saponins’ effects and use ranges on phytoremediation of cadmium both in soil and water and conduce studies on phytoremediation of other heavy-metal-contaminated soil and water with the help of tea saponins.

A review on application of phytoremediation technique for eradication of synthetic dyes by using ornamental plants

Phytoremediation emerges as an innovative and eco-friendly technique to remediate textile dyes with the use of various categories of plants. In recent years, ornamental plants emerge as more attractive and effective substitute in comparison to edible plants for phytoremediation. Regardless of aesthetic value, some ornamental plants can be grown to remediate the sites contaminated with dyes, heavy metals, pesticides, or other organic compounds. In this review, we focus on pioneer research on synthetic dye removal using ornamental plants and evaluate the phytoremediation capability of ornamental plants for treatment of textile effluent. This paper also emphasized specific ornamental plants having high accumulation and tolerance ability for removal of dyes. The mechanisms explored for the phytoremediation of dyes by ornamental plants have also been explained. This review will also be helpful for researchers for exploring more new ornamental plants in phytoremediation technique.

Ornamental Plant Efficiency for Heavy Metals Phytoextraction from Contaminated Soils Amended with Organic Materials

Accumulation of heavy metals (HMs) by ornamental plants (OPs) from contaminated agriculture soils is a unique technique that can efficiently reduce the metal load in the food chain. Amaranthus tricolor L. has attractive characteristics acquiring a higher growth rate and large biomass when grown at heavy metal contaminated soils. Site-specific detailed information is not available on the use of A. tricolor plant in metal phytoremediation from the polluted sites. The study aimed to enhance the uptake of HMs (Pb, Zn, and Cu) via amending poultry litter extract (PLE), vinasse sugarcane (VSC), and humic acid (HA) as natural mobilized organic materials compared to ethylene diamine tetraacetic acid (EDTA), as a common mobilized chemical agent by A. tricolor plant. The studied soils collected from Helwan, El-Gabal El-Asfar (Cairo Governorate), Arab El-Madabeg (Assiut Governorate), Egypt, and study have been conducted under pot condition. Our results revealed all organic materials in all studied soils, except EDTA in EL-Gabal El-Asfar soil, significantly increased the dry weight of the A. tricolor plant compared to the control treatment. The uptake of Pb and Zn significantly (p > 0.05) increased due to applying all organic materials to the studied soils. HA application caused the highest uptake as shown in Pb concentration by more than 5 times in Helwan soil and EDTA by 65% in El-Gabal El-Asfar soil while VSC increased it by 110% in El-Madabeg soil. Also, an increase in Zn concentration due to EDTA application was 58, 42, and 56% for Helwan, El-Gabal El-Asfar, and El-Madabeg soil, respectively. In all studied soils, the application of organic materials increased the remediation factor (RF) than the control. El-Madabeg soil treated with vinasse sugarcane gave the highest RF values; 6.40, 3.26, and 4.02% for Pb, Zn, and Cu, respectively, than the control. Thus, we identified A. tricolor as a successful ornamental candidate that, along with organic mobilization amendments, most efficiently develop soil health, reduce metal toxicity, and recommend remediation of heavy metal-contaminated soils. Additionally, long-term application of organic mobilization amendments and continued growth of A. tricolor under field conditions could be recommended for future directions to confirm the results.

Ornamental plants for the phytoremediation of heavy metals: Present knowledge and future perspectives

Environmental matrices are polluted with the plethora of contaminants, and among these, the concerns related to heavy metals (HMs) are also included. Due to the low cost in a long-term application and environmental friendliness, the use of biological remediation has gained significant attention in recent decades. The use of ornamental plants (OPs) in the field of phytoremediation is scarcely reported, and the impacts of HMs on OPs have also not been investigated in great depth. The OPs mediated HMs remediation can simultaneously remove contaminants and bring improvement in aesthetics of the site. The biomass of OPs produced after such activities can be used and sold as pot plants, cut flowers, essential oils, perfumes, air fresheners production, metal phytomining, and feedstock in silk production. The OPs also present a lower risk of HMs bioaccumulation compared to crop plants. This review focuses on the current knowledge of HMs toxicity to OPs, their applicability advantages, methods to improve the tolerance of OPs with incremented HMs uptake, challenges in the field, and future application perspectives. The case studies realted to practical application of OPs, from China, Iran, India, Oman, Pakistan, and Turkey, were also discussed. This work fetches the inter-disciplinary features and understanding for the sustainable treatment of HMs in a new novel way, to which no previous review has focused.

Effect of enhancers on the phytoremediation of soils polluted by pyrene and Ni using Sudan grass (Sorghum sudanense (Piper) Stapf.)

Remediation of heavy metal and polycyclic aromatic hydrocarbon (PAH)-co-contaminated soils has drawn much more attention; phytoremediation is an often-used technique. Sudan grass (Sorghum sudanense (Piper) Stapf.) with developed root system and strong PAHs and heavy metal tolerance is a potential choice for phytoremediation. In this study, the application of tea saponin (TS) (1 g kg^-1 soil) and nitrilotriacetic acid (NTA) (1 g kg^-1 soil) was to improve the removal efficiency of Ni and pyrene. TS and NTA had no obvious effects on the growth and soluble proteins of Sudan grass. Ni concentration in root was higher than that in the shoot. The addition of TS and NTA increased the Ni concentration in the root by 25.98% in Ni-contaminated treatment. Pyrene was mainly accumulated in the shoot of Sudan grass. Pyrene concentration in shoot increased by 20.14% with TS-NTA in pyrene-contaminated treatment and increased by 31.97% in Ni-contaminated treatment. TS and NTA had significantly improved dissolved organic matter and soil microbial activity. Microbial activity increased by 16.75%, 18.07%, and 23.364% in pyrene-contaminated, Ni-contaminated, and pyrene and Ni-co-contaminated treatment, respectively. This study showed that phytoremediation of pyrene and Ni-co-contaminated soil by Sudan grass could be enhanced by the application of TS-NTA and the interaction between pyrene and Ni impacted the accumulation of Ni and pyrene in Sudan grass.

Cadmium uptake from soil and transport by leafy vegetables: A meta-analysis

Cadmium (Cd) pollution in soil is a serious problem affecting environmental safety and human health, and the majority of Cd in human body comes from edible vegetables, especially leafy vegetables. Therefore, it is necessary to understand the absorption and transport of Cd soil by leafy vegetables. In this study, the meta-analysis method was firstly employed to study the relationship of Cd in leafy vegetables and soil systems. The results showed that different kinds of leafy vegetables have different abilities of Cd accumulation (measured by bioconcentration factor (BCF)) and transportation (measured by translocation factor (TF)): Brassica juncea (BCF = 5.10) and Brassica pekinensis (BCF = 1.90) had significantly higher ability to absorb cadmium in soil among the 19 studied species, Brassica pekinensis (TF = 2.52), Coriandrum sativum (TF = 2.18) had significantly higher cadmium transport capacity than other 11 species. To further clarify the influence of the three main factors of soil pH, Cd content and leafy vegetable species on the Cd enrichment ability of leafy vegetables, the regression equation was obtained by meta-regression analysis. BCF is affected by species, soil pH, soil cadmium content in the order from high to low. It was found that the estimated range of SOM for safe production of leafy vegetables is 20-30 g/kg. It could also be observed that soil cation exchange capacity (CEC) had a negative correlation with BCF, while soil salinity had a strong positive correlation with BCF. This study can provide a reliable reference for leafy vegetable security production in the Cd polluted field and aids in selecting species suitable for avoiding the absorption of heavy metals from polluted soil.

Ochrobactrum intermedium and saponin assisted phytoremediation of Cd and B[a]P co-contaminated soil by Cd-hyperaccumulator Sedum alfredii

Pot-culture experiments were conducted to investigate the potential of microorganism-saponin assisted phytoremediation of cadmium (Cd) and benzo(a)pyrene (B[a]P) co-contaminated soil using Cd-hyperaccumulator Sedum alfredii. Results showed that B[a]P-degrading bacterium (Ochrobactrum intermedium B[a]P-16) inoculation significantly increased root (by 22.1-24.1%) and shoot (by 20.5-23.4%) biomass of S. alfredii, whereas the application of saponin had no effect on the growth of S. alfredii. The saponin solution at 2 g L^-1 extracted more Cd and B[a]P than water, saponin enhanced Cd and B[a]P bioavailability in soil and thus promoted their uptake and accumulation in S. alfredii. The activity of B[a]P-16, dehydrogenase and polyphenol oxidase in co-contaminated soil was promoted by growing S. alfredii, and the application of B[a]P-16 and saponins caused a significant (P < 0.05) increase in both enzyme activities. The maximum B[a]P removal rate (82.0%) and Cd phytoextraction rate (19.5%) were obtained by co-application of S. alfredii with B[a]P-16 and saponin. The B[a]P-16 and plant promoted biodegradation were the predominant contributors towards removal of B[a]P from soil. A significant (P < 0.05) synergistic effect of B[a]P-16 and saponin on B[a]P and Cd removal efficiency was observed in this study. It is suggested that planting S. alfredii with application of B[a]P-16 and saponin would be an effective method for phytoremediation of soil co-contaminated with Cd and PAHs.

Enhancement of phytoextraction by Taiwanese chenopod and Napier grass by soapnut saponin and EDDS additions

Employment of biosurfactants and biodegradable chelants could further promote sustainability of soil and groundwater remediation tasks. Biosurfactant (soapnut saponin) and biodegrading chelants (ethylenediamine-N,N'-disuccinic acid (EDDS)) were employed to enhance the phytoextraction by native Taiwanese chenopod (Chenopodium formosanum Koidz.), Napier grass (Pennisetum purpureum) cultivar Taishi No. 4, and soapwort (Saponaria officinalis). Ethylene diamine tetraacetic acid (EDTA) was also employed as the control. Contaminated soils as silty clay loam texture was collected from a defunct rice paddy, containing chromium (Cr), cadium (Cd), and copper (Cu). Addition of both soapnut saponin and EDDS proportionally increased bioaccumulation factors (BCFs) of aboveground biomass for all three plants. Taiwanese chenopod demonstrated the best BCF values among three plants, with BCF increased from 0.76 to 2.6 and 1.3 for Cu under the presence of the highest dosages of EDDS and saponin. Plant aboveground biomass did exhibit negative correlation toward biomass metal concentrations. Presence of saponin did exhibit the least negative slopes among the correlations of all three additives for three plants. Taiwanese chenopod did exhibit the least negative slopes among the correlations of all three additives for three plants. Above observations suggested that saponin may have some protection for plants, especially for Napier grass. Taiwanese chenopod could possess more tolerance toward heavy metals than Napier grass does.

Simultaneous Determination and Quantification of Triterpene Saponins from Camellia sinensis Seeds Using UPLC-PDA-QTOF-MS/MS

Saponins in the Camellia sinensis seeds have a broad spectrum of biological properties and application potentials. However, up to now, no chromatographic methods have been developed to provide full fingerprinting and quality assurance for these saponins. This research aimed to develop a novel method to tentatively identify and quantify saponins in C. sinensis seeds by ultra-high-performance liquid chromatography coupled with photo-diode array detector and quadrupole time-of-flight mass spectrometry (UPLC-PDA-QTOF-MS/MS), and compare it with the classic vanillin-sulfuric acid assay. Fifty-one triterpene saponins, including six potentially new compounds, were simultaneously detected by UPLC-PDA-MS/MS, and their chemical structures were speculated according to the retention behavior and fragmentation pattern. The total saponin content in the crude extract and the purified saponin fraction of C. sinensis seeds were quantified to be 19.57 ± 0.05% (wt %) and 41.68 ± 0.09% (wt %) respectively by UPLC-PDA at 210 nm, while the corresponding values were determined to be 43.11 ± 3.17% (wt %) and 56.60 ± 5.79% (wt %) respectively by the vanillin-sulfuric acid assay. The developed UPLC-PDA -MS/MS method could determine specified saponins, and is more reliable for quantifying the C. sinensis seed saponins than the classic spectrophotometric method. It is of great significance for the future investigations and applications of these saponins.

Phytoextraction of heavy metals from contaminated soil, water and atmosphere using ornamental plants: mechanisms and efficiency improvement strategies

Accumulation of heavy metals (HMs) in soil, water and air is one of the major environmental concerns worldwide, which mainly occurs due to anthropogenic activities such as industrialization, urbanization, and mining. Conventional remediation strategies involving physical or chemical techniques are not cost-effective and/or eco-friendly, reinforcing the necessity for development of novel approaches. Phytoextraction has attracted considerable attention over the past decades and generally refers to use of plants for cleaning up environmental pollutants such as HMs. Compared to other plant types such as edible crops and medicinal plants, ornamental plants (OPs) seem to be a more viable option as they offer several advantages including cleaning up the HMs pollution, beautification of the environment, by-product generation and related economic benefits, and not generally being involved in the food/feed chain or other direct human applications. Phytoextraction ability of OPs involve diverse detoxification pathways such as enzymatic and non-enzymatic (secondary metabolites) antioxidative responses, distribution and deposition of HMs in the cell walls, vacuoles and metabolically inactive tissues, and chelation of HMs by a ligand such as phytochelatins followed by the sequestration of the metal-ligand complex into the vacuoles. The phytoextraction efficiency of OPs can be improved through chemical, microbial, soil amending, and genetic approaches, which primarily target bioavailability, uptake, and sequestration of HMs. In this review, we explore the phytoextraction potential of OPs for remediation of HMs-polluted environments, underpinning mechanisms, efficiency improvement strategies, and highlight the potential future research directions.

Effects of landscape plant species and concentration of sewage sludge compost on plant growth, nutrient uptake, and heavy metal removal

Landscape plants have great potentials in heavy metals (HMs) removal as sewage sludge compost (SSC) is increasingly used in urban forestry. We hypothesize that woody plants might perform better in HMs phytoremediation because they have greater biomass and deeper roots than herbaceous plants. We tested the differences in growth responses and HMs phytoremediation among several herbaceous and woody species growing under different SSC concentrations through pot experiments. The mixing percentage of SSC with soil at 0%, 15%, 30%, 60, and 100% were used as growth substrate for three woody (Ficus altissima Bl., Neolamarckia cadamba (Roxb.) Bosser, and Bischofia javanica Bl.) and two herbaceous (Alocasia macrorrhiza (L.) G. Don and Dianella ensifolia (L.) DC) plants. Results showed that the biomass, relative growth rate, and nutrient uptake for all plants increased significantly at each SSC concentration compared to the control; woody plants had higher biomass and nutrient use efficiency than herbaceous plants. All plants growing in SSC-amended soils accumulated appreciable amounts of HMs and reduced the contents of HMs present in the substrates. The woody plants were generally more effective than herbaceous plants in potentials of HMs phytoextraction, but A. macrorrhiza showed higher bioconcentration and translocation of Cu and Zn and D. ensifolia had higher bioconcentration and translocation of Cd than woody plants. The optimal application concentrations were 30% or less for woody plants and 15% for herbaceous plants for plant growth and ecological risk control, respectively. Intercropping suitable woody and herbaceous landscape plants in urban forestry might have promising potentials to minimize the ecological risks in the phytoremediation of SSC.

Optimization of tea-leaf saponins water extraction and relationships between their contents and tea (Camellia sinensis) tree varieties

Resulting from the year-on-year increase in tea plantations and the saturated consumption of tea leaves, the relative overcapacity in China's tea-leaf production appears. Discovering the new utilization of tea leaves is helpful to alleviate this phenomenon. The feasibility of extracting saponins from aged tea leaves was investigated and confirmed; three major variables in water extraction were optimized by Box-Behnken designs. The significant variable found in Box-Behnken designs, liquid-solid ratio, was went through single-variable experiments for a more accurate optimization. Seventy-five ml/g, 1 hr, and 80°C were optimal values and tea-leaf saponins yield of tea tree variety Longjing 43 reached 12.19% ± 0.0030% after optimizations, higher than the yield of tea-seed saponins from Camellia oleifera seed meals using the same extraction method (water extraction based on optimizations). According to correlation analyses, tea tree's leaf type and germination stage affected tea-leaf saponins contents positively, indicating tea trees with larger leaves and later germination stage would have a higher content of tea-leaf saponins with a higher yield of tea-leaf saponins under the same extraction method.

Development of a Rapid and Simple Method for Preparing Tea-Leaf Saponins and Investigation on Their Surface Tension Differences Compared with Tea-Seed Saponins

The relative overcapacity in China's tea-leaf production and the potential application of tea-leaf saponins in soil remediation encouraged in-depth developments and comprehensive utilizations of tea-leaf resources. Through variables optimizations using Box⁻Behnken designs for ultrasonic power, temperature as well as ultrasonic treatment time in ultrasonic-assisted water extraction and single-variable experiments for acetone-extraction solution ratio in acetone precipitation, a rapid and simple method was developed for preparing tea-leaf saponins. Tea-leaf saponins with the concentration of 3.832 ± 0.055 mg/mL and the purity of 76.5% ± 1.13% were acquired under the optimal values of 78 w, 60 °C, 20 min and 0.1 ratio of acetone-extraction solution. Both Fourier transform-infrared (FT-IR) spectra and ultraviolet (UV) spectra revealed slight composition differences between tea-leaf saponins and tea-seed saponins, while these differences were not reflected in the critical micelle concentration (CMC) and the surface tension of tea-leaf saponins and tea-seed saponins, indicating there was no need to distinguish them at the CMC. Further research attention on where tea-leaf saponins were in low concentrations is deserved to discover whether they had differences in comparison with tea-seed saponins, which was beneficial to apply them in the phytoremediation of contaminated soils.

Tea saponins: effective natural surfactants beneficial for soil remediation, from preparation to application

Tea saponins, found in Camellia plants, are natural non-ionic surfactants that offer obvious beneficial effects in soil remediation. Most tea saponins are extracted from the Camellia oleifera seed meal, with the leaves and flowers of Camellia sinensis as potential sources. Water extraction and ultrasound-assisted water extraction combined with acetone precipitation are recommended for the industrial extraction and purification of tea saponins, considering multiple factors. The detailed physical, chemical and biochemical properties of tea saponins need to be clarified, especially whether tea saponins with slightly different structures from distinct sources have different soil remediation properties. Applied in leaching remediation, phytoremediation and microbial remediation, tea saponins desorb heavy metals from contaminated soil as well as enhancing their bioavailability. Tea saponins improve the accumulation of pollutants by hyperaccumulators as well as the degradation of organic pollutants by microorganisms. Currently the mechanisms of tea saponins are not clear, although they are proven to be effective natural surfactants for the remediation of contaminated soils. This review enriches our understanding of tea saponins from various aspects and encourages further studies of industrial extraction and purification, and the field remediation mechanisms of tea saponins, making better use of Camellia plants and contributing to environmental protection.

Role of Burkholderia cepacia CS8 in Cd-stress alleviation and phytoremediation by Catharanthus roseus

The current study was performed to assess the effect of Burkholderia cepacia CS8 on the phytoremediation of cadmium (Cd) by Catharanthus roseus grown in Cd-contaminated soil. The plants cultivated in Cd amended soil showed reduced growth, dry mass, gas-exchange capacity, and chlorophyll contents. Furthermore, the plants exhibited elevated levels of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) under Cd stress. The bacterized plants showed higher shoot length, root length; fresh and dry weight. The improved stress tolerance in inoculated plants was attributed to the reduced quantity of MDA and H₂O₂, enhanced synthesis of protein, proline, phenols, flavonoids, and improved activity of antioxidant enzymes including peroxidase, superoxide dismutase, ascorbate peroxidase, and catalase. Similarly, the 1-aminocyclopropane-1-carboxylate deaminase activity, phosphate solubilization, auxin, and siderophore production capability of B. cepacia CS8 improved growth and stress alleviation in treated plants. The bacterial inoculation enhanced the amount of water extractable Cd from soil. Furthermore, the inoculated plants showed higher bioconcentration factor and translocation factor. The current study exhibits that B. cepacia CS8 improves stress alleviation and phytoextraction potential of C. roseus plants growing under Cd stress.

Saponins from seeds of Genus Camellia: Phytochemistry and bioactivity

Camellia seeds have been traditionally used as oil raw materials in Asia, and are known for a wide spectrum of applications. Oleanane-type triterpene saponins are the major specialised metabolites in Camellia seeds, and more than seventy saponins have been isolated and characterized. These natural compounds have caught much attention due to their various biological and pharmacological activities, including modulation of gastrointestinal system, anti-cancer, anti-inflammation, anti-microorganism, antioxidation, neuroprotection, hypolipidemic effects, foaming and detergence, as well as helping the accumulation of pollutants by plants. These compounds have a promising application in medicine, agriculture, industry and environmental protection. The present paper summarized the information from current publications on Camellia seed saponins, with a focus on the advances made in chemical structures, determination methods, bioactivities and toxicity. We hope this article will stimulate further investigations on these compounds.

Application of Bacillus megaterium MCR-8 improved phytoextraction and stress alleviation of nickel in Vinca rosea

The current research was performed to evaluate the effect of Bacillus megaterium MCR-8 on mitigation of nickel (Ni) stress in Vinca rosea grown on Ni-contaminated soil (50, 100, and 200 mg Ni kg^-1 soil). The treated plants exhibited reduced growth, biomass, gas exchange capacity, and chlorophyll (Chl) content under Ni stress. The inoculated plants growing in Ni-contaminated media exhibited relatively higher growth, total soluble protein, and proline contents. Similarly, bacterial inoculation improved the activity of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) under Ni stress. The Ni stress alleviation in inoculated plants was attributed to the reduced level of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂), enhanced synthesis of protein, proline, phenols, and flavonides in conjunction with improved activity of antioxidant enzymes. The growth-promoting characteristics of microbe such as 1-aminocyclopropane-1-carboxylate deaminase (ACCD) and phosphate solubilization activity, siderophore, and auxin production capability also improved the growth and stress mitigation in inoculated plants. Furthermore, the inoculated plants exhibited higher value for bioconcentration factor (BCF), translocation factor (TF), and resulted in higher loss of Ni content from soil. The current results exhibited the beneficial role of B. megaterium MCR-8 regarding stress alleviation and Ni phytoextraction by V. rosea.