Evaluation of hyperaccumulation potentials to cadmium (Cd) in six ornamental species (compositae)

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

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

Effects of Cadmium Stress on Carbon Sequestration and Oxygen Release Characteristics in A Landscaping Hyperaccumulator-Lonicera japonica Thunb

The carbon sequestration and oxygen release of landscape plants are dominant ecological service functions, which can play an important role in reducing greenhouse gases, improving the urban heat island effect and achieving carbon peaking and carbon neutrality. In the present study, we are choosing Lonicera japonica Thunb. as a model plant to show the effects of Cd stress on growth, photosynthesis, carbon sequestration and oxygen release characteristics. Under 5 mg kg^-1 of Cd treatment, the dry weight of roots and shoots biomass and the net photosynthetic rate (P_N) in L. japonica had a significant increase, and with the increase in Cd treatment concentration, the dry weight of roots and shoots biomass and P_N in the plant began to decrease. When the Cd treatment concentration was up to 125 mg kg^-1, the dry weight of root and shoots biomass and P_N in the plant decreased by 5.29%, 1.94% and 2.06%, and they had no significant decrease compared with the control, indicating that the plant still had a good ability for growth and photoenergy utilization even under high concentrations of Cd stress. The carbon sequestration and oxygen release functions in terms of diurnal assimilation amounts (P), carbon sequestration per unit leaf area (W_CO2), oxygen release per unit leaf area (W_O2), carbon sequestration per unit land area (P_CO2) and oxygen release per unit land area (P_O2) in L. japonica had a similar change trend with the photosynthesis responses under different concentrations of Cd treatments, which indicated that L. japonica as a landscaping Cd-hyperaccumulator, has a good ability for carbon sequestration and oxygen release even under high concentrations of Cd stress. The present study will provide a useful guideline for effectively developing the ecological service functions of landscaping hyperaccumulators under urban Cd-contaminated environment.

GC-MS analysis of aqueous extract of Nymphaea lotus and ameliorative potential of its biosynthesized gold nanoparticles against cadmium-induced kidney damage in rats

Plants possess compounds serving as reducing agents for green synthesis of gold nanoparticles (AuNPs), which is currently considered for biomedical application. Exposure to cadmium (Cd) can affect the functional integrity of the several organs such as kidney and liver. Nymphaea lotus (NL) is known for its several medicinal properties, including its protective role against tissue damages. This study investigated the bioactive compounds in NL using gas chromatography-mass spectroscopy (GC-MS) and ameliorative potential of its biosynthesized AuNPs (NL-AuNPs) against Cd-induced nephrotoxicity in rats. The presence of bioactive compounds in N. lotus was investigated by GC-MS in aqueous extract of NL. Gold nanoparticles were synthesized using aqueous extract of NL. Thirty rats were grouped into six (n = 5). Group 1 served as control, while group 2, 3, 4 and 5 received CdCl₂ (10 mg/kg) orally for five days. Thereafter, groups 3, 4, and 5, respectively, received silymarin (75 mg/kg), 5 and 10 mg/kg NL-AuNPs, orally for 14 days, while group 6 received 10 mg/kg NL-AuNPs only. Rats were sacrificed after treatment, and biochemical parameters and kidney histopathology were evaluated. Bioactive compounds of pharmacological importance identified include pyrogallol, oxacyclohexadecan-2-one, 22-Desoxycarpesterol, 7,22-Ergostadienol, β-sitosterol and Dihydro-β-agarofuran. Cadmium caused nephrotoxicity in rats, as evidenced by significant (p < 0.05) increase in the levels of kidney function markers (serum urea and creatinine) and inflammatory markers (Interleukin-6 (IL-6) and Nuclear Factor-κB (NF-κB)) when compared with control. These changes were significantly (p < 0.05) ameliorated by the spherically-synthesized NL-AuNPs (25-30 nm) with the 5 mg/kg NL-AuNPs more potent against kidney damage induced by Cd in rats but high doses of NL-AuNPs (≥10 mg/kg) could be suggested toxic. NL possess phytochemicals capable of reducing gold salts to nanoparticle form, and doses up to 5 mg/kg could be considered safe for the treatment of renal damage occasioned by cadmium.

Heavy Metals, Their Phytotoxicity, and the Role of Phenolic Antioxidants in Plant Stress Responses with Focus on Cadmium: Review

The current state of heavy metal (HM) environmental pollution problems was considered in the review: the effects of HMs on the vital activity of plants and the functioning of their antioxidant system, including phenolic antioxidants. The latter performs an important function in the distribution and binding of metals, as well as HM detoxification in the plant organism. Much attention was focused on cadmium (Cd) ions as one of the most toxic elements for plants. The data on the accumulation of HMs, including Cd in the soil, the entry into plants, and the effect on their various physiological and biochemical processes (photosynthesis, respiration, transpiration, and water regime) were analyzed. Some aspects of HMs, including Cd, inactivation in plant tissues, and cell compartments, are considered, as well as the functioning of various metabolic pathways at the stage of the stress reaction of plant cells under the action of pollutants. The data on the effect of HMs on the antioxidant system of plants, the accumulation of low molecular weight phenolic bioantioxidants, and their role as ligand inactivators were summarized. The issues of polyphenol biosynthesis regulation under cadmium stress were considered. Understanding the physiological and biochemical role of low molecular antioxidants of phenolic nature under metal-induced stress is important in assessing the effect/aftereffect of Cd on various plant objects-the producers of these secondary metabolites are widely used for the health saving of the world's population. This review reflects the latest achievements in the field of studying the influence of HMs, including Cd, on various physiological and biochemical processes of the plant organism and enriches our knowledge about the multifunctional role of polyphenols, as one of the most common secondary metabolites, in the formation of plant resistance and adaptation.

Characterisation of the complete mitochondrial genome of Taraxacum mongolicum revealed five repeat-mediated recombinations

We reported the mitochondrial genome of Taraxacum mongolicum for the first time. Five pairs of repeats that can mediate recombination were validated, leading to multiple conformations of genome. Taraxacum mongolicum belongs to the Asteraceae family and has important pharmaceutical value. To explore the possible interaction between the organelle genomes, we assembled the complete mitochondrial genome (mitogenome) of T. mongolicum using Illumina and Oxford Nanopore sequencing data. This genome corresponded to a circular molecule 304,467 bp long. It encodes 52 unique genes including 31 protein-coding, 3 ribosomal RNA (rRNA) and 18 transfer RNA (tRNA) genes. In addition to the single circular conformation, the existence of alternative conformations mediated by five repetitive sequences in the mitogenome was identified and validated. Recombination mediated by the inverted repeats resulted in two conformations. Conversely, recombination mediated by the two direct repeats broke one large circular molecule into two subgenomic circular molecules. Furthermore, we identified 12 homologous fragments by comparing the sequences of mitogenome and plastome, including eight complete tRNA genes. Lastly, we identified a total of 278 RNA-editing sites in protein-coding sequences based on RNA-seq data. Among them, cox1 and nad5 gene has the most sites (21), followed by the nad2 gene with 19 sites. We successfully validated 213 predicted RNA-editing sites using PCR amplification and Sanger sequencing. This project reported the first mitogenome of T. mongolicum and demonstrated its multiple conformations generated by repeat-mediated recombination. This genome could provide critical information for the molecular breeding of T. mongolicum, and also be used as a reference genome for other species of the genus Taraxacum.

Hormesis Responses of Growth and Photosynthetic Characteristics in Lonicera japonica Thunb. to Cadmium Stress: Whether Electric Field Can Improve or Not?

"Hormesis" is considered a dose-response phenomenon mainly observed at hyperaccumulator plants under heavy metals stress. In this study, the effects of electric fields on hormesis responses in Lonicera japonica Thunb. under cadmium (Cd) treatments were investigated by assessing the plant growth and photosynthetic characteristics. Under Cd treatments without electric fields, the parameters of plant growth and photosynthetic characteristics increased significantly when exposed to 5 mg L^-1 Cd, and decreased slightly when exposed to 25 mg L^-1 Cd, showing an inverted U-shaped trend, which confirmed that low concentration Cd has a hormesis effect on L. japonica. Under electric fields, different voltages significantly promoted the inverted U-shaped trend of the hormesis effect on the plant, especially by 2 V cm^-1 voltage. Under 2 V cm^-1 voltage, the dry weight of the root and leaf biomass exposed to 5 mg L^-1 Cd increased significantly by 38.38% and 42.14%, and the photosynthetic pigment contents and photosynthetic parameters were also increased significantly relative to the control, indicating that a suitable electric field provides better improvements for the hormesis responses of the plant under Cd treatments. The synergistic benefits of the 5 mg L^-1 Cd and 2 V cm^-1 electric field in terms of the enhanced hormesis responses of growth and photosynthetic characteristics could contribute to the promoted application of electro-phytotechnology.

Effects of different water conditions on the cadmium hyperaccumulation efficiency of Rorippa sylvestris (L.) Besser and Rorippa amphibia Besser

Increasing the translocation and accumulation of cadmium (Cd) in Cd hyperaccumulator is an important technology to improve the phytoremediation efficiency of Cd-contaminated soil. In order to investigate the effects of different water conditions on the growth and Cd accumulation ability of Cd hyperaccumulators Rorippa sylvestris (L.) Besser and Rorippa amphibia Besser in Cd-polluted soil, clone seedlings of them were transplanted into pots filled with 50 mg kg^-1 Cd-contaminated soil and cultured with water conditions of soil relative water content (RWC) 35%, 55%, 75%, 95%, and flooding respectively. The results showed the following: with the increase of RWC, the height of R. sylvestris and R. amphibia increased gradually, the dry biomass of shoot and whole plant increased and reached the maximum in 95% and then decreased in flooding; the Cd concentrations in shoots of R. sylvestris and R. amphibia were more than 100 mg kg^-1 except for 35% and flooding; Cd bioconcentration factors (BCFs) of R. amphibia reached the maximum of 3.8870 in 75% and R. sylvestris reached the maximum of 3.2330 in 95%; sufficient water resulted in the decrease of photosynthetic rate due to more Cd accumulation. However, under flooding condition, because of the decrease of Cd bioavailability in soil, the accumulation of Cd in shoots declined and the net photosynthetic rate (P_n) enhanced slightly.

Growth Response, Enrichment Effect, and Physiological Response of Different Garden Plants under Combined Stress of Polycyclic Aromatic Hydrocarbons and Heavy Metals

The combined pollution of heavy metals and polycyclic aromatic hydrocarbons is very common in China and needs urgent addressal. The use of resistant garden plants for phytoremediation accounts for both ecological restoration and ornamental value and has great application potential. In this study, cadmium (Cd) and pyrene (Pyr) were used as contaminants, and the growth responses, enrichment characteristics, and physiological responses of common garden plants were studied using greenhouse pot experiments. The Cd-Pyr compound stress affected the growth responses of plants. Chinese Pennisetum and lotus exhibited the best Cd-Pyr removal effect: the removal rates of Cd were 68.91% and 60.25%, respectively, and those of Pyr were 77.52% and 63.74%, respectively. Compound stress promoted the protective enzymes of ryegrass, lotus, and Chinese Pennisetum. Malondialdehyde (MDA) content in the leaves of the five plants was higher than that in the control group, whereas the chlorophyll and carotenoid content were lower. Overall, the order of resistance of the five garden plants tested under Cd-Pyr compound stress was: Chinese Pennisetum, lotus > ryegrass > Hemerocallis, Purple Coneflower.

Development of phytoremediator screening strategy and exploration of Pennisetum aided chromium phytoremediation mechanisms in soil

Screening of chromium (Cr) phytoremediators (i.e., hyperaccumulator plants and accumulation plants) is essential for the phytoremediation of Cr-contaminated soils but less tackled previously. In this study, we proposed a stepwise strategy for screening Cr phytoremediators and explored tolerance mechanism of the screened species. To achieve effective screening of Cr phytoremediators, seed germination, hydroponic, and pot experiment were performed sequentially, and an improved indicator system was established accordingly. Pennisetum was selected from nine plants, with its high growth rate and Cr remediation efficiency successfully demonstrated in the field. Antioxidant enzymes (i.e., superoxide dismutase (SOD) and catalase (CAT)) and photosynthesis under Cr stress were monitored for tracking the tolerance mechanism. Results showed that the enhanced SOD and CAT contributed to the strong tolerance of Pennisetum to Cr. The SOD and CAT were positively correlated with net photosynthetic rate (Pn), resulting in a phenomenon that Cr had no significant effect on Pn of Pennisetum even at 400 mg kg^-1. The research findings helped obtain powerful Cr phytoremediators, deepen our understanding of the tolerance mechanisms associated with phytoremediation, and eventually facilitate effective Cr removal in soil.

Changes in Metal Distribution, Vegetative Growth, Reactive Oxygen and Nutrient Absorption of Tagetes patula under Soil Cadmium Stress

Phytoremediation with hyperaccumulator plants has been recognized as a potential way for the clearing of cadmium (Cd)-contaminated soil. In this study, hyperaccumulator Tagetes patula was treated with seven concentrations of Cd, ranging from 0 to 300 mg kg−1. The Cd enrichment and nutrient contents in different organs during different growth phases were investigated. Under Cd concentrations ≤75 mg kg-1, the morphological growth of T. patula did not change significantly regardless of growth stage. However, when Cd concentration exceeded 150 mg kg−1, the morphological growth was remarkedly inhibited. The root/shoot ratio remained unchanged except for at 300 mg kg−1. In addition, Cd negatively influenced the flowering process at the concentration of 300 mg kg−1. Cd content increased significantly in Cd-treated plants. Nitrogen absorption was increased under Cd treatments, and phosphorus content was also increased under concentration ≤150 mg·kg−1. However, the potassium content in the flower was decreased under 300 mg kg−1. Furthermore, the contents of H2O2, O2− and malondialdehyde were increased during the seedling phase, especially when Cd concentration was ≥150 mg kg−1. In summary, T. patula showed a strong ability to tolerate Cd, and such ability might be explained by nutrient absorption and reactive oxygen clearness.

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.

Phytoremediation by ornamental plants: a beautiful and ecological alternative

Phytoremediation is an eco-friendly and economical technology in which plants are used for the removal of contaminants presents in the urban and rural environment. One of the challenges of the technique is the proper destination of the biomass of plants. In this context, the use of ornamental plants in areas under contamination treatment improves landscape, serving as a tourist option and source of income with high added value. In addition to their high stress tolerance, rapid growth, high biomass production, and good root development, ornamental species are not intended for animal and human food consumption, avoiding the introduction of contaminants into the food web in addition to improving the environments with aesthetic value. Furthermore, ornamental plants provide multiple ecosystem services, and promote human well-being, while contributing to the conservation of biodiversity. In this review, we summarized the main uses of ornamental plants in phytoremediation of contaminated soil, air, and water. We discuss the potential use of ornamental plants in constructed buffer strips aiming to mitigate the contamination of agricultural lands occurring in the vicinity of sources of contaminants. Moreover, we underlie the ecological and health benefits of the use of ornamental plants in urban and rural landscape projects. This study is expected to draw attention to a promising decontamination technology combined with the beautification of urban and rural areas as well as a possible alternative source of income and diversification in horticultural production.

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.

Effect of soil cadmium on root organic acid secretion by forage crops

The two forage species used in New Zealand pastoral agricultural systems, chicory (Cichorium intybus) and plantain (Plantago lanceolata) show differential ability to absorb and translocate cadmium (Cd) from roots to shoots. Chicory can accumulate Cd from even low Cd soils to levels that might exceed regulatory guidelines for Cd in fodder crops and food. Chicory and plantain were grown in soil-filled rhizocolumns under increasing Cd levels (0 (Control), 0.4, 0.8 and 1.6 mg Cd/kg soil) for 60 days and showed variable secretion of oxalic, fumaric, malic and acetic acids as a function of Cd treatment. Plant roots secrete such Low Molecular Weight Organic Acids into the rhizosphere soil, which can influence Cd uptake. Chicory showed significantly (P < 0.05) lower secretion of fumaric acid, and higher secretion of acetic acid than plantain at all Cd treatments. We propose that the significant secretion differences between the two species can explain the significantly (P < 0.05) higher shoot Cd concentration in chicory for all Cd treatments. Understanding the mechanism for increased uptake in chicory may lead to breeding or genetic modification which yield low Cd uptake cultivars needed to mitigate the risk of Cd accumulation in pastoral agricultural food chains from this increasingly important fodder crop.

Effects of EDDS on the Cd uptake and growth of Tagetes patula L. and Phytolacca americana L. in Cd-contaminated alkaline soil in northern China

Phytoextraction has been considered an effective and environment-friendly method for removing heavy metals from contaminated soil. However, the efficiency, mechanism, and adaptability of phytoextraction by hyperaccumulators in Cd-polluted weakly alkaline soil have not been investigated in detail. In this study, pot experiments were conducted to evaluate the enhanced effects of S,S-ethylenediamine disuccinic acid (EDDS) on phytoextraction in alkaline soil by measuring the degradation kinetic characteristics of EDDS and Cd absorption dynamics of Tagetes patula L. (T. patula) and Phytolacca americana L. (P. americana) for a period of 55 days. Results showed that the half-life of EDDS varied from 4.20-7.07 days and 3.35-4.36 days for T. patula and P. americana, respectively. EDDS-activated Cd reached saturation at a low dosage (1 mM) and a single application of EDDS was found to be better than double applications. The activation of EDDS on Cd applied before 45 days of harvest was better than that before 15 days of harvest, and disappeared after a 35-day application. Correspondingly, the Cd concentration in P. americana and T. patula leaves increased significantly after 3 days of the EDDS application. However, T. patula had a biomass 2.57 times and Cd absorption capacity 10.06 times higher than P. americana. EDDS showed almost no influence on the stem and leaf biomass of T. patula; however, the root weight decreased by 9.44-71.77%. The Cd concentration in T. patula leaves of all the treatments was 1.00-1.81 times that of the control group. In comparison with other treatments, the EDDS application (3 mM) before 15 days of harvest extracted the highest amount of Cd (601.45 μg/pot) in T. patula shoots, reaching 1.40 times that in the control group. Therefore, T. patula might be a more suitable phytoremediator for Cd-polluted alkaline soil than P. americana; the most effective method was the EDDS application (3 mM) before 15 days of harvest.

Phytoremediation of alkaline soils co-contaminated with cadmium and tetracycline antibiotics using the ornamental hyperaccumulators Mirabilis jalapa L. and Tagetes patula L

The co-contamination of farmland soils with heavy metals and antibiotics from the application of livestock and poultry manures poses great threats to human health. Phytoremediation might be a good solution to this problem. A pot culture experiment was conducted to evaluate the remediation capacity of two ornamental hyperaccumulators, namely, Mirabilis jalapa L. and Tagetes patula L., in alkaline soils co-contaminated with cadmium (Cd) and tetracycline antibiotics (TCs). The growth of M. jalapa and T. patula was significantly influenced by the co-contaminated soil. In treatments with TCs alone, the growth of T. patula was promoted (p < 0.05), while that of M. jalapa was inhibited. In the C2T3 treatment with TCs and Cd combined, the biomass of T. patula and M. jalapa decreased by 42.27% and 56.15% in roots and by 22.24% and 32.27% for in shoots, respectively, compared with those in the same treatment without TCs. The addition of TCs increased the accumulation of Cd in treatments with less than 15.0 mg/kg Cd. In M. jalapa, the concentration of Cd increased by 4.64% and 39.69% in roots and by 30.33% and 71.71% in shoots, and that in T. patula increased by 74.66% and 11.03% in roots and by 15.36% and 17.58% in shoots, respectively, in two treatments with TCs compared with those in the treatments with Cd alone. However, the accumulated Cd amounts decreased from 36.25 to 31.91 μg/pot and increased from 201.33 to 229.26 μg/pot in C2T2 for M. jalapa and T. patula, respectively, compared with those in the treatments without TCs. The TC removal efficiencies of all treatments were above 99%, and the residual amounts of TC and OTC were higher than that of CTC. M. jalapa and T. patula are promising hyperaccumulators that can be used for the remediation of alkaline soil co-contaminated with Cd and TCs.

Hormesis in plants under Cd exposure: From toxic to beneficial element?

Tolerance level to cadmium (Cd) toxicity is generally associated with reductions of the internal Cd accumulation in living organisms. In plants, Cd exposure frequently triggers negative effects on their growth and productivity. However, an increased number of studies has reported the improved performance of some plant species (or their accessions/genotypes/varieties/cultivars/clones) to Cd exposure, despite Cd accumulation in their roots and shoots. These results indicate that plants have developed protective strategies to neutralize the side-effects from Cd toxicity or, more controversially, mechanisms that employ Cd as beneficial element. Here, we gathered information about Cd-induced hormetic effects on plants, and explored the potential mechanisms that allow them to have a better performance under Cd exposure. The promotion of plant development depends on both direct and indirect Cd-induced alterations in the metabolism of plants and their surround environment. In addition, the mechanisms behind the positive Cd-induced transgenerational effects were also discussed in the present paper.

Dandelion is more tolerant to cadmium than to nickel excess

Comparative accumulation of cadmium (Cd) and nickel (Ni) and the consequences for the metabolism of common weed dandelion (triploid ones of Taraxacum sect. Taraxacum) were studied here for the first time. Cd accumulated more in both shoots and roots (489 and 2486 μg/g DW) than Ni (165 and 858 μg/g DW) after 14 days of exposure and only root Ni content did not increase between 7 and 14 days of exposure. Surprisingly, though Ni was less accumulated than Cd, it had more negative impact on basic physiology (root dry biomass, shoot water content and chlorophyll amount). Ni also evoked more extensive depression of mineral nutrients (K, Ca, Mg, and Mn) in the shoots than Cd while root potassium content was elevated by both metals. Ni suppressed accumulation of total thiols but anatomical changes and ROS formation (detected by fluorescence microscopy of total ROS and lipid peroxidation) were induced more by Cd. Total soluble phenols, major (caftaric and cichoric) and minor (chlorogenic and caffeic) phenolic acids were elevated by both metals and rather increased with prolonged exposure in the shoots (14 versus 7 days). On the contrary, typically depletion of these metabolites was found in the roots after prolonged exposure to Ni, but not to Cd. Data showed distinct toxicity of Cd and Ni in dandelion. More expressive tolerance of dandelion to Cd than to Ni indicates its potential use for the remediation of Cd-contaminated environment.