Plant growth regulators and EDTA improve phytoremediation potential and antioxidant response of Dysphania ambrosioides (L.) Mosyakin & Clemants in a Cd-spiked soil

Exploring the synergistic effects of indole acetic acid (IAA) and compost in the phytostabilization of nickel (Ni) in cauliflower rhizosphere

Heavy metals (HMs) contamination, owing to their potential links to various chronic diseases, poses a global threat to agriculture, environment, and human health. Nickel (Ni) is an essential element however, at higher concentration, it is highly phytotoxic, and affects major plant functions. Beneficial roles of plant growth regulators (PGRs) and organic amendments in mitigating the adverse impacts of HM on plant growth has gained the attention of scientific community worldwide. Here, we performed a greenhouse study to investigate the effect of indole-3-acetic acid (IAA @ 10- 5 M) and compost (1% w/w) individually and in combination in sustaining cauliflower growth and yield under Ni stress. In our results, combined application proved significantly better than individual applications in alleviating the adverse effects of Ni on cauliflower as it increased various plant attributes such as plant height (49%), root length (76%), curd height and diameter (68 and 134%), leaf area (75%), transpiration rate (36%), stomatal conductance (104%), water use efficiency (143%), flavonoid and phenolic contents (212 and 133%), soluble sugars and protein contents (202 and 199%), SPAD value (78%), chlorophyll 'a and b' (219 and 208%), carotenoid (335%), and NPK uptake (191, 79 and 92%) as compared to the control. Co-application of IAA and compost reduced Ni-induced electrolyte leakage (64%) and improved the antioxidant activities, including APX (55%), CAT (30%), SOD (43%), POD (55%), while reducing MDA and H2O2 contents (77 and 52%) compared to the control. The combined application also reduced Ni uptake in roots, shoots, and curd by 51, 78 and 72% respectively along with an increased relative production index (78%) as compared to the control. Hence, synergistic application of IAA and compost can mitigate Ni induced adverse impacts on cauliflower growth by immobilizing it in the soil.

Synergistic interactions of assorted ameliorating agents to enhance the potential of heavy metal phytoremediation

Pollution by toxic heavy metals creates a significant impact on the biotic community of the ecosystem. Nowadays, a solution to this problem is an eco-friendly approach like phytoremediation, in which plants are used to ameliorate heavy metals. In addition, various amendments are used to enhance the potential of heavy metal phytoremediation. Symbiotic microorganisms such as phosphate-solubilizing bacteria (PSB), endophytes, mycorrhiza and plant growth-promoting rhizobacteria (PGPR) play a significant role in the improvement of heavy metal phytoremediation potential along with promoting the growth of plants that are grown in contaminated environments. Various chemical chelators (Indole 3-acetic acid, ethylene diamine tetra acetic acid, ethylene glycol tetra acetic acid, ethylenediamine-N, N-disuccinic acid and nitrilotri-acetic acid) and their combined action with other agents also contribute to heavy metal phytoremediation enhancement. With modern techniques, transgenic plants and microorganisms are developed to open up an alternative strategy for phytoremediation. Genomics, proteomics, transcriptomics and metabolomics are widely used novel approaches to develop competent phytoremediators. This review accounts for the synergistic interactions of the ameliorating agent's role in enhancing heavy metal phytoremediation, intending to highlight the importance of these various approaches in reducing heavy metal pollution.

The effect of exogenous plant growth regulators on elevated Cd phytoremediation by Solanum nigrum L. in contaminated soil

Maximizing amendment potential is an emphasis in the HM-contaminated field of phytoremediation by hyperaccumulators due to the low bioavailability of HMs in soils and small biomass yields of plants. This study investigated the influence of different types and concentrations of plant growth regulators on Cd phytoremediation by Solanum nigrum in contaminated soil. Our conclusions showed that the shoot Cd extractions (μg plant-1) and the root and shoot biomasses at all the treatments remarkedly increased compared with that of the CK (p < 0.05), while the Cd concentrations at root and aboveground parts by S. nigrum, the extractable Cd concentrations, and pH value of soils did not change significantly compared with the CK (p < 0.05). Furthermore, correlation analysis showed that the shoot Cd phytoaccumulation and the root and aboveground biomasses of S. nigrum were particularly dependent upon the application of CTK and GA3 concentration gradient (p < 0.05). Moreover, some related physicochemical indexes were determined for supervising the growth conditions of plants, and these results pointed out that after exogenous PGRs treatments, the chlorophyll content and antioxidative enzymes POD and SOD activities in vivo of plants clearly advanced, while the H2O2 and MDA contents and CAT apparently declined. These consequence demonstrated that the exogenous PGR addition prominently reinforced the Cd phytoextraction capacity of S. nigrum in contaminated soil by stimulating plant growth and increasing shoot yields.

Sources, impacts, factors affecting Cr uptake in plants, and mechanisms behind phytoremediation of Cr-contaminated soils

Chromium (Cr) is released into the environment through anthropogenic activities and has gained significant attention in the recent decade as environmental pollution. Its contamination has adverse effects on human health and the environment e.g. decreases soil fertility, alters microbial activity, and reduces plant growth. It can occur in different oxidation states, with Cr(VI) being the most toxic form. Cr contamination is a significant environmental and health issue, and phytoremediation offers a promising technology for remediating Cr-contaminated soils. Globally, over 400 hyperaccumulator plant species from 45 families have been identified which have the potential to remediate Cr-contaminated soils through phytoremediation. Phytoremediation can be achieved through various mechanisms, such as phytoextraction, phytovolatilization, phytodegradation, phytostabilization, phytostimulation, and rhizofiltration. Understanding the sources and impacts of Cr contamination, as well as the factors affecting Cr uptake in plants and remediation techniques such as phytoremediation and mechanisms behind it, is crucial for the development of effective phytoremediation strategies. Overall, phytoremediation offers a cost-effective and sustainable solution to the problem of Cr pollution. Further research is needed to identify plant species that are more efficient at accumulating Cr and to optimize phytoremediation methods for specific environmental conditions. With continued research and development, phytoremediation has the potential to become a widely adopted technique for the remediation of heavy metal-contaminated soils.

How does phosphorus influence Cd tolerance strategy in arbuscular mycorrhizal - Phragmites australis symbiotic system?

To clarify how phosphorus (P) influences arbuscular mycorrhizal fungi (AMF) interactions with host plants, we measured the effects of variation in environmental P levels and AMF colonization on photosynthesis, element absorption, ultrastructure, antioxidant capacity, and transcription mechanisms in Phragmites australis (P. australis) under cadmium (Cd) stress. AMF maintained photosynthetic stability, element balance, subcellular integrity and enhanced antioxidant capacity by upregulating antioxidant gene expression. Specifically, AMF overcame Cd-induced stomatal limitation, and mycorrhizal dependence peaked in the high Cd-moderate P treatment (156.08%). Antioxidants and compatible solutes responded to P-level changes: the primary driving forces of removing reactive oxygen species (ROS) and maintaining osmotic balance were superoxide dismutase, catalase, and sugars at limited P levels and total polyphenol, flavonoid, peroxidase, and proline at abundant P levels, we refer to this phenomenon as "functional link." AMF and phosphorus enhanced Cd tolerance in P. australis, but the regulation of AMF was P-dependent. Phosphorus prevented increases in total glutathione content and AMF-induced GSH/GSSG ratio (reduced to oxidized glutathione ratio) by inhibiting the expression of assimilatory sulfate reduction and glutathione reductase genes. The AMF-induced flavonoid synthesis pathway was regulated by P, and AMF activated Cd-tolerance mechanisms by inducing P-dependent signaling.

Plant Growth Regulators with a Balanced Supply of Nutrients Enhance the Phytoextraction Efficiency of Parthenium hysterophorus for Cadmium in Contaminated Soil

Heavy metal contamination in soil, such as cadmium (Cd), poses a serious threat to global food security and human health. It must be managed using environmentally friendly and cost-effective technologies. Plants with high resistance to Cd stress and high biomass production could be potential candidates for the phytoremediation of Cd-contaminated soils to improve Cd phytoextraction. In this regard, the present study was carried out to determine the effect of gibberellic acid (GA₃), indole acetic acid (IAA), and fertilizers (N, P, and K) on Parthenium hysterophorus growth and biomass production as well as Cd phytoextraction capabilities. A pot experiment was conducted with various combinations of PGRs and fertilizers, with treatments arranged in five replicates using a completely randomized design. After harvesting, each plant was divided into various parts such as stems, roots, and leaves, and different growth, physiological, and biochemical parameters were recorded. Results showed that under Cd stress, growth, physiological, and biochemical parameters were all significantly decreased. With the combined application of plant growth regulators (GA₃ and IAA) and nutrients, Cd stress was alleviated and all parameters significantly improved. In comparison to the control treatment, the combined application of N + P + K + GA₃ + IAA resulted in the highest fresh and dry biomass production of the root (12.31 and 5.11 g pot^-1), shoot (19. 69 and 6.99 g pot^-1), leaves (16.56 and 7.09 g pot^-1), and entire plant (48.56 and 19.19 g pot^-1). Similarly, the same treatment resulted in higher chlorophyll a and b and total chlorophyll contents under Cd stress, which were 2.19, 2.03, and 3.21 times higher than the control, which was Cd stress without any treatment. The combination of N + P + K + GA₃ + IAA also resulted in the highest proline and phenolic contents. In the case of different enzyme activities, the combined application of N + P + K + GA₃ + IAA under Cd stress led to a high increase in catalase (2.5 times), superoxide (3.5 times), and peroxidase (3.7 times) compared to the control. With the combined application of N+ P+ K + GA₃ + IAA, the maximum values of BCF (8.25), BAC (2.6), and RF (5.14%) were measured for phytoextraction potential. On the basis of these findings, it is concluded that P. hysterophorus has a high potential to grow, produce the most biomass, and act as a Cd hyperaccumulator in Cd-contaminated soil.

Synergistic impact of two autochthonous saprobic fungi (A. niger and T. pseudokoningii) on the growth, ionic contents, and metals uptake in Brassica juncea L. and Vigna radiata L. under tannery solid waste contaminated soil

Unrestricted disposal of tannery solid waste (TSW) into agricultural soils has resulted in the contamination of heavy metals (HMs) such as chromium (Cr) cadmium (Cd), Copper (Cu), and Zinc (Zn) along with the severe potential to degrade the environmental quality around the world. In the present study, a combined phyto- and myco-remediation strategy was evaluated to enhance the growth, ionic contents, and phytoextraction potential of Brassica juncea and Vigna radiata for HMs from TSW-contaminated soil. A pot experiment was conducted in the greenhouse using single or combined inoculation of Trichoderma pseudokoningii (Tp) and Aspergillus niger (An) in B. juncea and V. radiata under TSW-contaminated soil at different doses (0, 50, and 100%). The results showed that the growth parameters of both B. juncea and V. radiata were severely affected under 50 and 100% TSW treatment. The combined inoculation of both the fungal species ameliorated the positive impacts of 50 and 100% TSW application on growth and ionic contents accumulation in B. juncea and V. radiata. The combined application of An + Tp at 100% TSW enhanced the shoot length (87.8, 157.2%), root length (123.9, 120.6%), number of leaves (184.2, 175.0%), number of roots (104.7, 438.9%), and dry weight (179.4, 144.8%) of B. juncea and V. radiata, respectively as compared to control with any fungal treatment at 100% TSW. A single application of An at different doses of TSW enhanced the metal concentration in B. juncea, whereas Tp increased the concentration of the metals in V. radiata. The concentration of Cr in roots (196.2, 263.8%), shoots (342.4, 182.2%), Cu in roots (187.6, 137.0%), shoots (26.6, 76.0%), Cd in roots (245.2, 184.6%), shoots (142.1, 73.4%), Zn in roots (73.4, 57.5%), shoots (62.9, 57.6%), in B. juncea were increased by the application of An at 50 and 100% treatment levels of TSW, respectively compared to control (C). Moreover, the HMs (Cr, Cu, Cd, and Zn) uptake was also improved under 50 and 100% TSW with the combined inoculation of Tp + An in both B. juncea and V. radiata. In conclusion, the combined inoculation of Tp + An was more effective in metal removal from TSW-treated soil.NOVELTY STATEMENTLimited studies have been conducted on filamentous fungi systematically under metal-contaminated sites for their diversity, metal tolerance, and their potential in enhancing the phytoremediation potential of different crop plants.In the present study, single and/or combined inoculation of fungal strains was found effective in alleviating different metals stress in tannery solid waste contaminated soil by improving defense mechanisms and plant growth due to the association between fungal strains and plants.The combined application of both fungal strains had an additive effect in enhancing the bioaccumulation capacity of B. juncea and V. radiata compared to their single inoculation.

Utilization of Indole Acetic Acid with Leucadendron rubrum and Rhododendron pulchrum for the Phytoremediation of Heavy Metals in the Artificial Soil Made of Municipal Sewage Sludge

The development of phytoremediation by garden plants is an effective way to deal with the dilemma of municipal sewage sludge disposal. In this study, two ornamental plants were used as phytoremediation plants to rehabilitate heavy-metal-contaminated municipal sewage sludge in field experiments, and the role of exogenous phytohormone IAA was also tested. Ornamental plants Loropetalum chinense var. rubrum (L. rubrum) and Rhododendron pulchrum (R. pulchrum) adapted well to the artificial soil made of municipal sewage sludge, and the concentrations of Cu, Zn, Pb, and Ni were decreased by 7.29, 261, 20.2, and 11.9 mg kg−1, respectively, in the soil planted with L. rubrum, and 7.60, 308, 50.1, and 17.7 mg kg−1, respectively, in the soil planted with R. pulchrum, accounted for 11−37% of the total amounts and reached significant levels (p < 0.05), except Cd. The concentration of Pb in all parts of the two ornamental plants was increased, as well as most heavy metals in L. rubrum root. As a result, three months after transplant, the phyto-extraction amounts in L. rubrum were 397, 10.9, and 1330 μg for Ni, Cd, and Pb, respectively, increased by 233% to 279%. The phyto-extraction amount in R. pulchrum were 1510, 250, and 237 μg for Zn, Pb, and Cu, respectively, increased by 143% to 193%. These results indicated a potential to remediate heavy metals of the two ornamental plants, especially L. rubrum. The results of correlation analysis implied that the interaction of heavy metals in the plant itself played an important role in the uptake of heavy metals. This seemed to explain why applying IAA in the experiment had little effect on plant growth and phytoremediation of heavy metals. This study provided a green and feasible idea for the proper disposal of municipal sewage sludge.

Dissolved organic matter-assisted phytoremediation potential of cotton for Cd-contaminated soil: a relationship between dosage and phytoremediation efficiency

Dissolved organic matter (DOM) is a novel Cd-contaminated soils amendment for phytoremediation. However, the phytoremediation efficiency for different DOM doses has been insufficiently investigated. In this study, we investigated the effect of five DOM doses (v/w, 0%, 1%, 2%, 4% and 8%) on the phytoremediation efficiency of cotton in Cd-contaminated soil through pot experiment. The results showed that bioavailable Cd concentrations and organic matter in the soil increased with the increased of DOM dosage. The DOM dose increased the chlorophyll content, photosynthesis, and the total biomass of cotton. In addition, the DOM application increased the Cd content in cotton roots and changed the Cd uptake in cotton shoots, increasing shoot Cd extraction efficiency by 8.53-20%. Simultaneously, soil Cd phytoextraction efficiency significantly increased. Furthermore, applying a 1% DOM dose resulted in safeguarding fibre biomass and maximising the efficiency of shoot extraction. Redundancy analysis showed that the Mn content in leaves is critical for increasing cotton biomass, anti-oxidation competence and phytoremediation efficiency under 1% DOM dose. In conclusion, DOM enhanced cotton remediation in Cd-contaminated soils and applying DOM at 1% was a suitable choice for Cd-contaminated soils.

Use of Parthenium hysterophorus with synthetic chelator for enhanced uptake of cadmium and lead from contaminated soils-a step toward better public health

Parthenium hysterophorus L. is a vigorous plant species with cosmopolitan distribution. It can uptake considerable quantities of heavy metals from the soil and accrue these metals in its different tissue. The use of chelating agent i.e., Ethylenediaminetetraacetic acid (EDTA) can boost up metal uptake capacity. Pot experiment was performed to evaluate phytoextraction potential of P. hysterophorus for lead (Pb) and cadmium (Cd) with and without the aid of EDTA chelator. Shoot length, weight of root and shoot (both fresh and dry), leaves number, and chlorophyll contents of P. hysterophorus got reduced with an increase in metal uptake. The results revealed the highest concentration of Cd in shoot without and with EDTA was 283.6 and 300.1 mg kg^-1, correspondingly. Increase in Pb concentration was also boosted up by the EDTA from its maximum concentration in shoot 4.30-9.56 mg kg^-1. Generally, Pb and Cd concentrations were greater in shoots of P. hysterophorus than the roots regardless of EDTA in the treatments. EDTA also impacted positively the accumulation of essential ions K⁺, Na⁺, and Ca⁺² in P. hysterophorus. The capacity of P. hysterophorus to accumulate Pb and Cd found to be increased with EDTA in the soil. Bringing metals level in the soil in accordance to the WHO standards can improve the ecosystem as well as public health.

Engineered bacterium-binding protein promotes root recruitment of functional bacteria for enhanced cadmium removal from wastewater by phytoremediation

Functional bacteria promote the efficiency of phytoremediation by enhancing plant growth and participating in decontamination. However, their activity is frequently compromised by the weakness of their interaction with plant roots. In this study, we designed the artificial protein LcGC composed of a bacterium-binding domain, a GFP fluorescence reporter, and a carbohydrate-binding domain to function as a physical contact between functional bacteria and plant roots. This protein was then expressed in an engineered yeast cell factory and extracted to assess its effect on rhizosphere microbiome composition, plant growth, and cadmium removal in a simulated phytoremediation system containing the remediation plant Lemna minor and the functional heavy metal-capturing bacteria Cupriavidus taiwanensis and Pseudomonas putida. LcGC efficiently bound bacterial cell wall components and glucan, endowing it high efficiency to bind both functional bacteria and plant roots. Scanning microscopy and microbiome analysis revealed that LcGC enhanced root recruitment and colonization of functional bacteria on the root surfaces. Furthermore, LcGC with the aid of single C. taiwanensis or of C. taiwanensis and P. putida in combination promoted plant growth, enhanced tolerance to cadmium-induced oxidative stress, and consequently improved cadmium-removing capacity of the plants, with the percent of cadmium removal reaching up to 91% for LcGC plus C. taiwanensis, and to 96% for LcGC plus C. taiwanensis and P. putida on day 7. This study provided a physical contact-based strategy to enhance the interaction between functional microbes and plant roots for efficient phytoremediation.

Priming with EDTA, IAA and Fe Alleviates Pb Toxicity in Trigonella Foneum graecum L. growth: Phytochemicals and secondary metabolites

This study evaluated the effects of the exogenous application of ethylenediaminetetraacetic acid (EDTA), indole-3-acetic acid (IAA) and iron sulfate (FeSO₄) upon the phytochemical mechanisms of fenugreek grown under Pb-excess (2000 mg L^-1 PbCl₂). The results showed that chemical additives of EDTA and IAA as well as FeSO₄ improved fenugreek germination parameters. The radicle length and the amylase activity were significantly improved under IAA treatment compared to EDTA and FeSO₄. Exogenous FeSO₄ was more effective to improving growth parameters. Moreover, the decrease in hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) levels was noted under all chemical additives especially under IAA application. In addition, it was more effective than EDTA and Fe in increasing catalase, glutathione (GSH), ascorbate peroxidase (APX), flavonoids and phenols while the increment superoxide dismutase (SOD) production was more pronounced under EDTA addition to Pb than other chelators. HPLC analysis revealed that the gallic was the major phenol produced under all chelators addition especially with IAA. In addition, the syringic acid was only produced with exogenous IAA while the quercetin was only detected under EDTA addition. Our results exhibited a higher IAA efficiency than EDTA and FeSO₄ in mitigating Pb stress in fenugreek through up-regulated mechanisms of the antioxidant system for reducing reactive oxygen species (ROS) activities and enhancing special phenols.

Chemical Composition and In Vitro Anti-Wood-Decay Fungal Activities of Dysphania ambrosioides Leaf Essential Oil From Taiwan

We evaluated the leaf essential oil in whole or fractions of Dysphania ambrosioides with respect to their resistance to wood decay fungal activities in vitro of 4 fungi. The main ingredients with the greater anti-wood decay capability were also identified. Fresh leaves of D. ambrosioides were hydrodistillated in a Clevenger-type apparatus and the resulting oil characterized using GC-FID and GC-MS instruments. The essential oil was found to consist of α-terpinene (30.5%), p-cymene (17.3%), carvacrol (16.2%), and ascaridole (15.1%). The oil showed resistance to wood decay activity of Trametes versicolor, Phanerochaete chrysosporium, Phaeolus schweinitzii, and Lenzites sulphureu. The oil had excellent resistance to wood decay fungal activities, and the active compounds were shown to be carvacrol and ascaridole.

A critical review on the phytoremediation of heavy metals from environment: Performance and challenges

Phytoremediation is an effective, green and economical technique. Different types of phytoremediation methods can be used for the reduction of heavy metal contaminations, such as phytoextraction, phytovolatilization, phytostabilization and phytofiltration. The biomass of plants and the bioavailability of heavy metals in soil are the key factors affecting the efficiency of phytoremediation. It's worth noting that the low remediation efficiency and the lack of effective disposal methods for contaminated biomass have limited its development and application. At present, biological, physical, chemical, agronomic and genetic approaches have been used to enhance phytoremediation. Disposal methods of contaminated biomass usually include pyrolysis, incineration, composting and compaction. They are effective, but are costly and have security problems. Improper disposal of contaminated biomass can lead to leaching of heavy metals. The leaching possibility of different forms of heavy metal in plants is different. Hence, it has great significance to explore the different forms of heavy metals in plants which can help to explore appropriate disposal methods. According to the challenges of phytoremediation, we put forward some views and recommendations for the sustainable and rapid development of phytoremediation technology.

Phytoremediation of Cadmium Polluted Soils: Current Status and Approaches for Enhancing

Cadmium (Cd) is a heavy metal present in atmosphere, rocks, sediments, and soils without a known role in plants. It is relatively mobile and can easily enter from soil into groundwater and contaminate the food chain. Its presence in food in excess amounts may cause severe conditions in humans, therefore prevention of cadmium entering the food chain and its removal from contaminated soils are important steps in preserving public health. In the last several years, several approaches for Cd remediation have been proposed, such as the use of soil amendments or biological systems for reduction of Cd contamination. One of the approaches is phytoremediation, which involves the use of plants for soil clean-up. In this review we summarized current data on the use of different plants in phytoremediation of Cd as well as information about different approaches which have been used to enhance phytoremediation. This includes data on the increasing metal bioavailability in the soil, plant biomass, and plant accumulation capacity as well as seed priming as a promising novel approach for phytoremediation enhancing.