Nickel Accumulation Research Articles

Effects of Vanadium and Nickel on Morphological Characteristics and on Vanadium and Nickel Uptake by Shoots of Mojito (Mentha × villosa) and Lavender (Lavandula anqustifolia)

Vanadium and Nickel may enter the human food chain through medicinal and culinary plants which in great doses are toxic to human, so it is important to determine their potential toxicity and health risk. Therefore, the objective of this work was to study the effects of Vanadium and Nickel on morphological characteristics and on Vanadium and Nickel uptake by shoots of mojito (Mentha × vilosa) and lavender (Lavandula anqustifolia). A completely randomized block design with five Vanadium treatments (0, 5, 10, 20, 40 mg V L-1) and five replications per treatment and another one with five Nickel treatments (0, 5, 10, 20 and 40 mg Ni L-1) and five replications per treatment for mojito and lavender were conducted in pots. No visible toxic or inhibitory symptoms were observed on the plants due to the increasing amounts of Vanadium or Nickel. Shoot dry matter and root dry matter of mojito and lavender decreased with increasing Vanadium rates. Vanadium uptake by shoots of mojito and lavender increased linearly with increasing Vanadium rates. Nickel uptake by shoots of lavender increased linearly with increasing rates of Nickel. Mojito is a Nickel accumulator.

Weathering processes and crystal chemistry of Ni-bearing minerals in saprock horizons of New Caledonia ophiolite

This paper proposes a detailed study of the formation of the main Ni ore that is today mined in the saprock horizon of New Caledonia ophiolite. More specifically, this study aims at, i) characterizing the nature and the crystal chemistry of the main Ni-bearing phases, and ii) better understanding the weathering processes that lead to such nickel enrichment in these horizons. The study focuses on a boulder (~20 cm in diameter) sampled in the saprock facies of the Koniambo massif, reflecting the early stages of peridotite bedrock weathering. This boulder is explored with a large panel of techniques, from the centimeter to the nanometer scale, including micro-imaging and X-ray absorption spectroscopy at the Ni and Fe K-edges. A characterization along the cross section reveals important heterogeneities in textures, and a large concentration of nickel in the outer part through an intense and connected Ni-phyllosilicate network that develop at the expense of the primary lizardite network. The inner part is preserved from the weathering by supergene fluids. Primary lizardite initially contains about 0.4 wt% NiO, similarly to surrounding olivine and pyroxene. In the outer part, the main Ni-bearing phases are identified as polygonal serpentine (up to ~5 wt% NiO) and two successive generations of talc-like minerals that contain ~20 to 36 wt% NiO. In these two minerals, nickel is very likely to form nano-clusters in the octahedral layers. The Fe3+/Fetotal ratios in serpentine minerals increases regularly from ~0.5 in primary lizardite, to ~0.95 in polygonal serpentine, traducing increasing local oxygen fugacity with increasing weathering degree.From molecular modeling, we propose that the large excess of water systematically observed for these Ni-rich minerals can be explained by nanometer sized crystals, which potentially require many additional hydrogen bonds (i.e., mainly silanol groups) to passivate crystal edges and preserve electro-neutrality. On the other hand, the main driving force leading to important nickel accumulation in the saprock horizon is likely to be the strong pH gradient present at all scales in the regolith profile, including at the boulder scale, which have major effects on the hydroxide solubility. As the pH decreases in the phyllosilicate network, we observe, i) the weathering and oxidation of the primary lizardite network, ii) the formation of a newly formed lizardite, iii) the formation of Ni-rich polygonal serpentine, iv) the formation of successive generations of Ni-rich talc-like minerals.

Nickel accumulation, localisation and the biochemical responses in Eclipta prostrata (L.) L

ABSTRACTThe objective of the study was to examine the growth, accumulation and biochemical responses in Eclipta prostrata (L.) L., at increasing levels of nickel in soil after 30 days of treatment. Accumulation of nickel in different parts of the plant was found in a concentration-dependent manner, and the uptake was significantly higher in roots than in shoots. Lipid peroxidation was significantly increased in the metal-exposed plant, compared with the control. The plant exhibited a significant decrease in its pigment content at Ni treatment levels from 100 mg/kg onwards. Compared with the control, a significant increase was observed in the metal exposed plant in its non-enzymatic antioxidants such as proline, flavonoid and phenolic compounds, as well as in the activity of enzymatic antioxidants like superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase. The present study revealed the mechanism adopted by E. prostrata in alleviating nickel-induced oxidative damage. Transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR) provided supporting evidence for the uptake of heavy metals, localisation and binding or interaction of nickel in the leaf. Thus, the plant appears to have the potential as a tolerant nickel phytoremediator species for application in decontamination of moderately polluted soils.

Seasonal variation in heavy metal accumulation in plants at coal mine sites and possible health risk

Human health challenges in recent times have been attributed to consumption of food contaminated with heavy metals. Coal mining is an anthropogenic activity that releases heavy metals into the environment. This study, therefore, assessed accumulation of heavy metals (lead (Pb), cadmium (Cd), nickel (Ni), arsenic (As) and iron (Fe)) in plant species in the vicinity of Akwuke and Iva coal mine in Coal city, Enugu State. The results indicate that the highest concentration of Ni (9.02 ± 0.03 mg/kg), As (0.005 ± 0.001 mg/kg) and Cd (2.16 ± 0.07 mg/kg) was accumulated in Alchornea cordifolia while the concentration of Pb (10.37 ± 0.52 mg/kg) was highest in Andropogon gayanus and Fe (231.00 ± 1.41 mg/kg) was highest in Irvingia gabonensis. The values of Ni (9.02 ± 0.03 mg/kg), As (0.005 ± 0.00 mg/kg), Pb (10.37 ± 0.32 mg/kg), Cd (2.02 ± 0.03 mg/kg), and Fe (46.00 ± 1.41 mg/kg) accumulated in A. cordifolia, A. gayanus, D. guinense, and M. indica in wet season were significantly (P < 0.05) higher than their corresponding values (5.04 ± 0.07, 8.96 ± 0.01 and 0.003 ± 0.001 mg/kg, 1.87 ± 0.07 mg/kg, and 33.45 ± 0.21 mg/kg) in dry season, respectively. Alchornea cordifolia, Andropogon gayanus and Irvingia gabonensis consumed by animals and local inhabitants in the vicinity of the two mined sites could expose them to high levels of Pb, Ni and Cd, thus posing a serious health risk to the local people.

Effect of nickel uptake on selected growth parameters of Amaranthus viridis L.

Nickel is an essential element for normal physiological functions in plants. At higher doses (>50 mg/kg, as per WHO) it is toxic to plants and humans, which can bring about oxidative stress affecting the physiological functions of plants and is also considered carcinogenic to human beings. To manage nickel pollution in environment, proper chemical or phytoremediation techniques are required. In this regard nickel accumulator plants would offer a cost effective and environmental friendly phytoremediation method. In the present study, the nickel phyto-accumulation potential of Amaranthus viridis from soil was evaluated to check the tolerance level and the impact on selected morphological parameters like total biomass, plant height, root length and number of leaves. Nickel uptake by A. viridis was studied from Ni contaminated soil amended with20, 40, 60, 80 mg/Kg of Ni exposure under controlled conditions. Toxic effects and tolerance of the plant to toxic doses of nickel was evaluated by correlating the uptake per gram of biomass with various parameters of plant like its height, biomass, root length and, number of leaves. Supply dependent maximum nickel uptake of 108 µg/gm and corresponding decrease in growth parameters were recorded up to 60 mg/Kg exposure. This study indicates the uptake of nickel by A. viridis increases with increase in supply up to 60mg/kg and beyond 60 mg/kg, the uptake decreases. The study also shows uptake of nickel per gram of biomass has a significant negative correlation mainly with parameters like plant height (R= -0.71 at 0.05 level of significance) and total biomass (R = -0.83 at 0.05 level of significance) where as other parameters like length of root and number of leavers are not significantly affected (P>0.05) with uptake of nickel per gram of biomass.

Evaluation of the protective role of exogenous growth regulators against Ni toxicity in woody shrub Daphne jasminea

Main conclusionThe results provide a significant verification of the activity of exogenously applied phytohormones: gibberellic acid, jasmonic acid, and brassinolide in the modulation of the plant’s response to nickel treatment.The study investigated nickel accumulation and its toxicity to Daphne jasminea shoots cultured in vitro with or without exogenous supplementation with phytohormones: gibberellic acid (GA3), jasmonic acid (JA), and brassinolide (BL). The aim was to verify the modulatory effect of exogenous plant growth regulators (PGRs) on plant reaction to Ni excess. The combined action of Ni and PGRs was evaluated at the anatomical, ultrastructural, and biochemical levels. Nickel toxicity was manifested in decreased biomass accretion and growth tolerance index (83–53.6%), attributed to enhanced synthesis of growth inhibitors, mainly abscisic acid. As a defence reaction, endogenous gibberellins accumulated. Exogenous GA3 ameliorated the plant reaction to Ni stress, inducing proliferation and growth rate. Ni tolerance in the presence of GA3 was attributed to peroxisomal reactions that stimulated the synthesis of endogenous JA. In contrast, the application of BL caused enhanced Ni accumulation. Plants suffered from pronounced stress due to massive oxidation. The defence strategy of plants subjected to Ni and BL involved cell wall rearrangements. Exogenous JA stimulated the synthesis of active auxins and salicylic acid, contributing to enhanced mitotic activity within explants. However, JA disturbed the integrity of chloroplasts and lamellar compartments. Our study revealed that an action of exogenous PGRs may either enhance tolerance to Ni or increase metal toxicity in D. jasminea. Particularly in in vitro culture, where explants are subjected to external phytohormonal stimuli, the combined effects of supplemental PGRs may enhance stress and substantially affect plant development. Our results provide a significant verification of exogenous PGRs activity in the modulation of plant response to nickel.

Nickel toxicity in wood frog tadpoles: Bioaccumulation and sublethal effects on body condition, food consumption, activity, and chemosensory function.

Nickel (Ni) concentrations in aquatic ecosystems can be amplified by anthropogenic activities including resource extraction. Compared with fish and invertebrates, knowledge of Ni toxicity in amphibians is limited, especially for northern species. We examined the effect of Ni on wood frog (Lithobates sylvaticus) tadpoles, the species with the widest and most northern distribution of any anuran in North America. Wood frog tadpoles were exposed to a Ni concentration gradient (0.02-5.5 mg/L of Ni at 164 mg/L as CaCO3 water hardness) for 8 d and examined for lethality, Ni bioaccumulation, and several sublethal endpoints including body condition, food consumption, activity, and chemosensory function. Nickel induced a sublethal effect on body condition (8-d 10 and 20% effect concentrations [EC10 and EC20] of 1.07 ± 0.38 and 2.44 ± 0.51 mg/L of Ni ± standard error [SE], respectively) but not on food consumption, activity, or chemosensory function. Nickel accumulation in tadpole tissues was positively related to an increase in aqueous Ni concentration but was not lethal. Both the acute and chronic US Environmental Protection Agency water quality guideline concentrations for Ni (0.71 and 0.08 mg/L at 164 mg/L as CaCO3 water hardness, respectively) were protective against lethal and sublethal effects in wood frog tadpoles. In the present study, wood frog tadpoles were protected by current water quality guidelines for Ni and are likely not as useful as other taxa for environmental effects monitoring for this particular metal. Environ Toxicol Chem 2018;37:2458-2466. © 2018 SETAC.

Lead and Nickel Accumulation in Brassica juncea arawali Growing in Contaminated Soil

Lead and Nickel Accumulation in Brassica juncea arawali Growing in Contaminated Soil

Coarse particulate matter (PM2.5\u201310) in Los Angeles Basin air induces expression of inflammation and cancer biomarkers in rat brains

Air pollution is linked to brain inflammation, which accelerates tumorigenesis and neurodegeneration. The molecular mechanisms that connect air pollution with brain pathology are largely unknown but seem to depend on the chemical composition of airborne particulate matter (PM). We sourced ambient PM from Riverside, California, and selectively exposed rats to coarse (PM2.5–10: 2.5–10 µm), fine (PM<2.5: <2.5 µm), or ultrafine particles (UFPM: <0.15 µm). We characterized each PM type via atomic emission spectroscopy and detected nickel, cobalt and zinc within them. We then exposed rats separately to each PM type for short (2 weeks), intermediate (1–3 months) and long durations (1 year). All three metals accumulated in rat brains during intermediate-length PM exposures. Via RNAseq analysis we then determined that intermediate-length PM2.5–10 exposures triggered the expression of the early growth response gene 2 (EGR2), genes encoding inflammatory cytokine pathways (IL13-Rα1 and IL-16) and the oncogene RAC1. Gene upregulation occurred only in brains of rats exposed to PM2.5–10 and correlated with cerebral nickel accumulation. We hypothesize that the expression of inflammation and oncogenesis-related genes is triggered by the combinatorial exposure to certain metals and toxins in Los Angeles Basin PM2.5–10.

Evaluation of health risk to humans in consumption of wheat grown in nickel-contaminated soils

In this research, accumulation and distribution of nickel in root, leaves and stem and grains of wheat were studied to assess the health of wheat grain for human consumption. A greenhouse experiment was conducted based on randomized complete block design with three replications. Wheat was grown under two nickel concentrations in soil (0.0 and 100 mg kg-1). At maturity, wheat was divided into its parts (root, leaves and stem, grain) and nickel concentrations were measured in plant parts. Results indicated that the highest nickel (132.8 mg kg-1 plant tissue) was accumulated in roots which was 12 times more than nickel accumulated in shoots, suggesting that no actual remediation was occurred by wheat. Under high concentrations of nickel, wheat grains are not suitable for human consumption, because health risk index was achieved 130.27 and 169.40 for adults and children, respectively. However, because wheat was able to grow under high concentrations of nickel, this plant can be considered as a tolerant plant to nickel stress. Further research is needed to determine the ultimate limit of nickel concentrations in soils where the accumulation of nickel in the grains is not such a high amount that it threatens human health.

Profiling of proteasome activity in Alyssum species on serpentine soils in Turkey reveals possible insight into nickel tolerance and accumulation

In crops and most plants, nickel induces oxidative stress resulting in oxidized and misfolded proteins. Proteasomes maintain cellular homeostasis during stress by removing these damaged proteins. Although mild stress tolerance is mediated by proteasomal proteolysis of misfolded and oxidized proteins, previous studies have observed that severe nickel stress decreases proteasome activity in nickel-sensitive plants. Whether or not proteasome function is impaired in nickel-tolerant plants is not know. Therefore, we tested the hypothesis that proteasome activity is elevated in nickel-tolerant Alyssum species capable of accumulating nickel to unusually high levels. Our field studies examined Alyssum sibiricum and Alyssum caricum, a moderate nickel accumulator and hyper-accumulator respectively, growing on their native serpentine soil in Turkey. A. sibiricum had higher proteasome activity on serpentine soil compared to non-serpentine soil; these plants also had elevated levels of nickel accumulation and higher proteasome activity compared to other low accumulating plants in the genus Festuca or Astragalus. In A. caricum, proteasome activity was very weakly correlated with nickel soil bioavailability or accumulation in leaf tissue, suggesting that proteasome function was not impaired in plants that accumulated the highest concentration of nickel. We discuss if maintained proteasome activity might underpin nickel tolerance and the unique ecophysiology of nickel hyper-accumulation in plants.

Nickel Accumulation in Soybean and Melastoma on Contaminated Soil

Nickel Accumulation in Soybean and Melastoma on Contaminated Soil

Effects of a mixture of ligands on metal accumulation in diffusive gradients in thin films (DGT)

Environmental contextThe availability of trace metals to aquatic organisms is influenced by the natural ligands present in water. We investigate the influence of the composition of the system on the availability of metal cations as nutritive or toxic species. The focus is on clarifying whether availability measured in single-ligand systems with diffusive gradients in thin film devices can be used to predict accumulation in mixtures. AbstractNatural waters contain mixtures of ligands, which collectively affect the availability of trace metals. The individual contribution of each complex to the overall metal flux received by a sensor can be described in terms of its lability degree. The question arises as to whether the mixture entails specific non-additive effects, i.e. to what extent is it possible to predict the collective behaviour of the mixture from the values of the lability degree of each single ligand system (SLS). For this reason, a series of experiments with diffusion gradients in thin films (DGT) devices were carried out to measure nickel accumulation from synthetic media comprising either nitrilotriacetic acid (NTA), ethylenediamine (EN) or mixtures of both ligands. The results were compared with numerical simulations. It is shown that NiNTA becomes more inert in the mixture than in the SLS that contains the same concentration of free Ni and NiNTA, whereas the opposite is true for the Ni bound to EN, which becomes more labile in the mixture than in the SLS. This unprecedented behaviour arises when one of the ligands (NTA, forming strong and partially labile complexes) is present under non-excess conditions. As NiNTA and NiEN have an opposite influence on the lability degree of each other, the sum of partial fluxes calculated from the lability degrees obtained in SLSs yields a reasonable estimate of DGT performance in the mixture. Experimental accumulations in the mixture are just slightly below the predicted values, with errors lower than 11 % when NTA concentrations vary from 20 to 100 % of the total Ni concentration.

Use of zeolite to neutralise nickel in a soil environment

Nickel is a heavy metal which is a stable soil pollutant which is difficult to remediate. An attempt to reduce its impact on the environment can be made by changing its solubility. The right level of hydrogen ions and the content of mineral and organic colloids are crucial in this regard. Therefore, methods to neutralise heavy metals in soil are sought. There are no reports in the literature on the possibility of using minerals in the detoxication of a soil environment contaminated with metals. It is important to fill the gap in research on the effect of zeolites on the microbiological, biochemical and physicochemical properties of soils under pressure from heavy metals. Therefore, a pot experiment was conducted on two soils which examined the effect of various levels of contamination of soil with nickel on the activity of soil enzymes, physical and chemical properties and growth and development of plants. An alleviating effect of zeolite Bio.Zeo.S.01 on the negative impact of nickel on the soil and a plant (oats) was examined. The enzyme activity and the oat yield were found to be significantly and negatively affected by an excess of nickel in the soil, regardless of the soil type. The metal was accumulated more in the oat roots than in the above-ground parts. An addition of zeolite decreased the level of accumulation of nickel in oats grown only on sandy-silty loam. Zeolite Bio.Zeo.S.01 used in the study only slightly alleviated the negative effect of nickel on the biochemical properties of soil. Therefore, its usability in the remediation of soil contaminated with nickel is small.

СРЕДНИЕ ХАРАКТЕРНЫЕ КОНЦЕНТРАЦИИ ТОКСИКАНТОВ В ДОННЫХ ОТЛОЖЕНИЯХ ДЕЛЬТЫ ВОЛГИ И СЕВЕРНОГО КАСПИЯ

The general test object in the assessment of pollution degree of water ecosystems are bottom sediments. There are different attempts to norming, having regional status in default of standards of the contents of preferred toxicants in the bottom sediments of water objects at the present time in Russia. In this work scientists used the approach permitting to characterize the pollution degree, using comparison between absolute values of toxicant concentrations, that are most prevailing in the Volga-Caspian basin, and these toxicant concentrations are calculated for each kind of the main type of sediments. For the calculation scientists used longstanding body of data on the content of oil products, zinc, copper, plumbum, cadmium, nickel, manganese and ferrum in the water courses of the Volga Delta and western part of the Northern Caspian. Conducted typification of the grounds with separation of the main types of river and sea sediments was accompanied by averaging out values of toxicant concentrations. There was identified an increase of the content of all toxicants in 2.8-9.8 times when transferring from coarse particle fractions to finely divided fractions for freshwater grounds. In the same time, besides dispersion, the presence of shell material played an important role in the accumulation of oil products, nickel and manganese. In the Northern-Caspian bottom sediments lessening of particle size caused the raise of toxicant concentrations, especially in the presence of silty fractions. Moreover, the growing concentration of several pollutants - nickel, plumbum, and cadmium - was observed in shelly grounds or with impurity of sand. According to the results of comparative analysis of the data on the toxicant content with average specific values in the bottom sediments of watercourses of the Volga delta and the Caspian Sea in 2016, there were singled out the locations most affected by pollution.

Nickel hyperaccumulation mechanisms: a review on the current state of knowledge

Hyperaccumulator plants are unusual plants that accumulate particular metals or metalloids, such as nickel, zinc, cadmium and arsenic, in their living tissues to concentrations that are hundreds to thousands of times greater than what is normal for most plants. The hyperaccumulation phenomenon is rare (exhibited by less than 0.2% of all angiosperms), with most of the ~500 hyperaccumulator species known globally for nickel. This review highlights the contemporary understanding of nickel hyperaccumulation processes, which include root uptake and sequestration, xylem loading and transport, leaf compartmentation and phloem translocation processes. Hyperaccumulator plants have evolved highly efficient physiological mechanisms for taking up nickel in their roots followed by rapid translocation and sequestration into the aerial shoots. The uptake of nickel is mainly involved with low affinity transport systems, presumably from the ZIP family. The presence of high concentrations of histidine prevents nickel sequestration in roots. Nickel is efficiently loaded into the xylem, where it mainly presents as Ni2+. The leaf is the main storage organ, which sequestrates nickel in non-active sites, e.g. vacuoles and apoplast. Recent studies show that phloem translocates high levels of nickel, which has a strong impact on nickel accumulation in young growing tissues.

Senecio conrathii N.E.Br. (Asteraceae), a new hyperaccumulator of nickel from serpentinite outcrops of the Barberton Greenstone Belt, South Africa

AbstractFive nickel hyperaccumulators belonging to the Asteraceae are known from ultramafic outcrops in South Africa. Phytoremediation applications of the known hyperaccumulators in the Asteraceae, such as the indigenous Berkheya coddii Roessler, are well reported and necessitate further exploration to find additional species with such traits. This study targeted the most frequently occurring species of the Asteraceae on eight randomly selected serpentinite outcrops of the Barberton Greenstone Belt. Twenty species were sampled, including 12 that were tested for nickel accumulation for the first time. Although the majority of the species were excluders, the known hyperaccumulators Berkheya nivea N.E.Br. and B. zeyheri (Sond. &amp; Harv.) Oliv. &amp; Hiern subsp. rehmannii (Thell.) Roessler var. rogersiana (Thell.) Roessler hyperaccumulated nickel in the leaves at expected levels. A new hyperaccumulator of nickel was discovered, Senecio conrathii N.E.Br., which accumulated the element in its leaves at 1695 ± 637 µg g−1 on soil with a total and exchangeable nickel content of 503 mg kg−1 and 0.095 µg g−1, respectively. This makes it the third known species in the Senecioneae of South Africa to hyperaccumulate nickel after Senecio anomalochrous Hilliard and Senecio coronatus (Thunb.) Harv., albeit it being a weak accumulator compared with the latter. Seven tribes in the Asteraceae have now been screened for hyperaccumulation in South Africa, with hyperaccumulators only recorded for the Arctoteae and Senecioneae. This suggests that further exploration for hyperaccumulators should focus on these tribes as they comprise all six species (of 68 Asteraceae taxa screened thus far) to hyperaccumulate nickel.

Problem of pollution of soils heavy metals

An important environmental issue today is the accumulation of toxic their metals in soils. On the basis of analyzed literary sources shown to be the most polluted territory of our state is the urbanized square of the central and the south-eastern regions. Among metal-pollutants of the soil are the most widespread and toxic nets, zinc, copper, cadmium, nickel and aluminum. Mobility and bioavailability heavy metals and aluminum is directly proportional to the acidity of the soil.Taking into account the potential hazard of toxic metals for living organisms The urgent task of scientists is to assess the biological risk these substances. The article analyzes the accumulation of lead compounds (Pb) and nickel (Ni) soil fields adjacent to the highway Kyiv-Odessa, on different distances from the source of pollution.

Effect of nickel addition on the wettability and reactivity of tin on copper substrate

The wettability of a copper substrate by Sn—Ni alloy and the interfacial active properties of nickel were investigated. We determined the contact angle as a function of holding time in the Sn—Ni/Cu system at low Ni concentration. The contact angle of Sn can be decreased from 30° to 25° by adding 0.1 wt% Ni to Sn. We observed accumulation of the nickel at the solid—liquid interface. We assume that the nickel accumulation is caused by the interfacial active property of the nickel in an Sn—Ni/Cu system.

Accumulation of cobalt and nickel in tissues of Clethra barbinervis in a metal dosing trial

This study reveals the accumulation properties of Co from viewpoints of the analogy with Ni and also the variation of the other essential micro elements in the Co accumulator tree, Clethra barbinervis. Seedlings of C. barbinervis were grown in single and mixed treatments in the rhizosphere containing Co, Ni, or both at three different concentrations (5, 50, and 500 μM). In roots, stems, and leaves, the concentrations of Cu, Fe, Mn, and Zn, together with Co and Ni, were determined. Biomass was reduced in plants treated with 500 μM Ni, but not when treated with Co. The Co concentration in leaves was higher than those in other tissues, and the maximum Co accumulation in leaves was 2012 μg g−1. Accumulation of Co competed with Zn transport and stimulated Cu transport. Our results indicate that C. barbinervis is a Co hyperaccumulator and is more tolerant to Co than to Ni. The Co hyperaccumulation capacity is likely achieved by Zn transport systems involved in root to shoot translocation, and Co accumulation has some competitive and facilitative interactions with the other heavy metals.