Ni Uptake Research Articles

Desert dust improves the photophysiology of heat-stressed corals beyond iron

Desert dust is an important source of essential metals for marine primary productivity, especially in oligotrophic systems surrounded by deserts, such as the Red Sea. However, there are very few studies on the effects of dust on reef-building corals and none on the response of corals to heat stress. We therefore supplied dust to two coral species (Stylophora pistillata and Turbinaria reniformis) kept under control conditions (26 °C) or heat stress (32 °C). Since dust releases large amounts of iron (Fe) in seawater, among other metals, the direct effect of different forms of Fe enrichment on coral photosynthesis was also tested. First, our results show that the desert dust altered the coral metallome by increasing the content of metals that are important for coral physiology (e.g. lithium (up to 5-fold), manganese (up to 4-fold in S. pistillata), iron (up to 3-fold in S. pistillata), magnesium (up to 1.3-fold), molybdenum (up to 1.5-fold in S. pistillata)). Overall, metal enrichment improved the photosynthetic performance of corals, especially under thermal stress (e.g. Pgross (up to 2-fold), Pnet (up to 10-fold), chlorophyll (up to 1.5-fold), symbionts (up to 1.6-fold)). However, Fe exposure (ferric chloride or ferric citrate) did not directly improve photosynthesis, suggesting that it is the combination of metals released by the dust, the so-called “metal cocktail effect”, that has a positive impact on coral photophysiology. Dust also led to a decrease in Ni uptake (up to 1.4-fold in the symbionts), likely related to the nitrogen metabolism. Finally, we found that the isotopic signature of metals such as iron, zinc and copper is a good indicator of heat stress and dust exposure in corals. In conclusion, desert dust can increase coral resistance to bleaching by supplying corals with essential metals.

Co-application of silicon and biochar affected anatomical and biochemical properties of corn leaf (Zea mays L.) under soil nickel toxicity

Soil pollution with heavy metals is a threat to crop production. Practically, application of silicon (Si) with biochar can be a cost-effective approach to immobilize metals in contaminated soils. Investigation of the anatomical and biochemical changes of corn leaf is important for describing the mechanisms of Si and biochar soil application in alleviating the negative effects of nickel (Ni) toxicity. A factorial pot experiment was conducted to investigate the effect of Si (0, 250 and 500 mg Si kg-1 soil) in combination with rice husk biochar (RHB) or sheep manure biochar (SMB) prepared at two pyrolysis temperatures (300 and 500 °C) on anatomical and biochemical properties of corn leaves in a Ni-polluted soil. The length, width, area and weight of third-leaf, and metaxylem and protoxylem of midrib improved by application of Si250 with RHB more than SMB. At Si250, RHB300 and RHB500 improved the stomatal area by 31.7 and 27.7% compared to control (without biochar), respectively. The leaf membrane stability index was increased by increasing Si application level and reached 69% in RHB300. In contrast to total chlorophyll, the highest carotenoid content, catalase and peroxidase was obtained by control (without Si and biochar) followed by SMB. At Si250, the highest relative water content (RWC) was observed in RHB300 by 34.8% increase. Also, RHB300 had the highest total dry matter, with increases of 82.2, 120.0 and 83.1% at Si0, Si250 and Si500, respectively. By increasing the Si level and biochar application, the shoot Ni decreased between 42.1 to 133.3%. Combined application of Si250 with RHB300 resulted in the highest dry matter through improving the leaf dimensions, metaxylem and protoxylem areas of midrib, membrane stability index, total chlorophyll, and RWC, while Ni uptake was reduced.

Individual and combinatorial application of nanosilica and carbon nanoparticles alleviate nickel stress in barley (Hordeum vulgare L.): Impacts on gene expression, AsA − GSH cycle, cellular fractionation, and proline metabolism

Nanotechnology is grabbing great attention all over the world because of its stimulating use in numerous fields, and the nanosilica (nSi) and carbon nanoparticles (CNPs) application has been examined in various studies. Conversely, the nSi and CNPs combinatorial use is a new method and researched in limited literature. For this purpose, a pot experiment was conducted to examine various growth and biochemical parameters in barley (Hordeum vulgare L.) under the toxic concentration of nickel (Ni) i.e., 200 mg kg−1 which were primed with combined application of two NPs of nSi at 3 mM and CNPs i.e., 200 μM respectively. The results showed that the Ni toxicity in the soil showed a significantly (P < 0.05) declined in the growth, gas exchange attributes, sugars, AsA-GSH cycle, cellular fractionation, proline metabolism in H. vulgare. However, Ni toxicity significantly (P < 0.05) increased oxidative stress biomarkers, enzymatic and nonenzymatic antioxidants including their gene expression in H. vulgare. Although, the application of nSi and CNPs showed a significant (P < 0.05) increase in the plant growth and biomass, gas exchange characteristics, enzymatic and non-enzymatic compounds and their gene expression and also decreased the oxidative stress, and Ni uptake. In addition, individual or combined application of nSi and CNPs enhanced the cellular fractionation and decreases the proline metabolism and AsA−GSH cycle in H. vulgare. These results open new insights for sustainable agriculture practices and hold immense promise in addressing the pressing challenges of heavy metal contamination in agricultural soils.

The role of the carapace in the accumulation of metals from seawater in the green crab (Carcinus maenas): Studies with radio-labeled calcium, zinc, and nickel

The role of the carapace in the uptake and storage of newly accumulated metals was investigated in the green crab exposed to environmentally relevant concentrations of calcium ([Ca] = 389 mg L−1 or 9.7 mmol L−1), zinc ([Zn] = 82 μg L−1 or 1.25 μmol L−1), and nickel ([Ni] = 8.2 μg L−1 or 0.14 μmol L−1) in 12 °C seawater, using radio-tracers (45Ca, 65Zn, 63Ni). After 24-h exposure, carapace exhibited the highest concentration of newly accumulated Ca, whereas carapace and gills exhibited the highest concentrations of both newly accumulated Zn and Ni relative to other tissues. For all three metals, the carapace accounted for >85 % of the total body burden. Acute temperature changes (to 2 °C and 22 °C) revealed the highest overall temperature coefficient Q10 (2.15) for Ca uptake into the carapace, intermediate Q10 for Ni (1.87) and lowest Q10 (1.45) for Zn. New Ca uptake into the carapace continued linearly with time for 24 h, new Zn uptake gradually deviated from linearity, whereas Ni uptake reached a plateau by 6 h. Attachment of a rubber membrane to the dorsal carapace, thereby shielding about 20 % of the total crab surface area from the external water, eliminated both new Zn and Ni incorporation into the shielded carapace, whereas 36 % of new Ca incorporation persisted. When recently euthanized crabs were exposed, new Zn uptake into the carapace remained unchanged, whereas Ca and Ni uptake were reduced by 89 % and 71 %, respectively. We conclude that the carapace is a very important uptake and storage site for all three metals. All of the uptake of new Zn and new Ni, and most of the uptake of new Ca into this tissue comes directly from the external water. For Zn, the mechanism involves only physicochemical processes, whereas for Ca and Ni, life-dependent processes make the major contribution.

Heavy metals immobilization and bioavailability in multi-metal contaminated soil under ryegrass cultivation as affected by ZnO and MnO2 nanoparticle-modified biochar

Pollution by heavy metals (HMs) has become a global problem for agriculture and the environment. In this study, the effects of pristine biochar and biochar modified with manganese dioxide (BC@MnO2) and zinc oxide (BC@ZnO) nanoparticles on the immobilization and bioavailability of Pb, Cd, Zn, and Ni in soil under ryegrass (Lolium perenne L.) cultivation were investigated. The results of SEM–EDX, FTIR, and XRD showed that ZnO and MnO2 nanoparticles were successfully loaded onto biochar. The results showed that BC, BC@MnO2 and BC@ZnO treatments significantly increased shoots and roots dry weight of ryegrass compared to the control. The maximum dry weight of root and shoot (1.365 g pot−1 and 4.163 g pot−1, respectively) was reached at 1% BC@MnO2. The HMs uptake by ryegrass roots and shoots decreased significantly after addition of amendments. The lowest Pb, Cd, Zn and Ni uptake in the plant shoot (13.176, 24.92, 32.407, and 53.88 µg pot−1, respectively) was obtained in the 1% BC@MnO2 treatment. Modified biochar was more successful in reducing HMs uptake by ryegrass and improving plant growth than pristine biochar and can therefore be used as an efficient and cost effective amendment for the remediation of HMs contaminated soils. The lowest HMs translocation (TF) and bioconcentration factors were related to the 1% BC@MnO2 treatment. Therefore, BC@MnO2 was the most successful treatment for HMs immobilization in soil. Also, a comparison of the TF values of plant showed that ryegrass had a good ability to accumulate all studied HMs in its roots, and it is a suitable plant for HMs phytostabilization.

Biogeochemical Fluxes of Nickel in the Global Oceans Inferred From a Diagnostic Model

AbstractNickel (Ni) is a micronutrient that plays a role in nitrogen uptake and fixation in the modern ocean and may have affected rates of methanogenesis on geological timescales. Here, we present the results of a diagnostic model of global ocean Ni fluxes which addresses key questions about marine Ni cycling. Sparsely available observations of Ni concentration are first extrapolated into a global gridded climatology using tracers with better observational coverage such as macronutrients, and testing three different machine learning techniques. The physical transport of Ni is then estimated using the ocean circulation inverse model (OCIM2), revealing regions of net convergence or divergence. These diagnostics are not based on any assumption about Ni biogeochemical cycling, but their spatial patterns can be used to infer where biogeochemical processes such as biological Ni uptake and regeneration take place. Although Ni and silicate (Si) have similar concentration patterns in the ocean, we find that the spatial pattern of Ni uptake in the surface ocean is similar to phosphate (P) uptake but not to silicate (Si) uptake. This suggests that their similar distributions arise from different biogeochemical mechanisms, consistent with other evidence showing that Ni is not incorporated into diatom frustules. We find that Ni:P ratios at uptake do not decrease as Ni concentrations approach 2 nM, which challenges the hypothesis of a ∼2 nM pool of non‐bioavailable Ni in the surface ocean. Finally, we find that the net regeneration of Ni occurs deeper in the ocean than for P, though not as deeply as for Si.

Nickelophilic root foraging by the nickel hyperaccumulator, Streptanthus polygaloides subsp. undulatus (Brassicaceae)

AbstractRoot foraging may allow hyperaccumulator plants to enhance element accumulation. This study compared root proliferation of two annual serpentine endemics: Streptanthus polygaloides (Ni hyperaccumulator) and Streptanthus insignis (nonhyperaccumulator). In a greenhouse experiment, pots were divided by a sealed partition, Ni‐amended soil (800 mg kg −1) in one half, unamended soil in the other. Seeds were germinated over the partition, allowing roots to explore both soils. After 5 months, roots from each side of each pot were harvested, washed, dried, and weighed. Streptanthus polygaloides root biomass was significantly (twofold) greater in Ni‐amended soil whereas S. insignis root biomass was similar in the two soils. In a lab experiment, seedlings were grown in vertical agar‐filled petri dishes to determine if Ni affected seedling root growth. Seedlings were placed on either side of a central filter paper strip soaked in either NiCl2 solution or deionized water. Growth direction of the primary root (toward, away, neutral) and lateral root numbers and lengths were recorded. For seedlings, primary root direction and lateral root numbers/lengths were significantly increased toward Ni‐soaked filter paper only for S. polygaloides. We conclude that S. polygaloides exhibited positive root foraging responses. These may enhance Ni uptake and we suggest the term “nickelophilic root foraging” be applied to this behavior.

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.

Nickel uptake in leafy greens from contaminated soil: an investigation into phytoavailability and health risk assessment using in vitro digestion model.

Nickel (Ni) is a toxic metal that not only pollutes the environment but also causes harmful impacts on plant growth and human health. Therefore, it is crucial to assess the relationship between the phytoavailability of Ni in soil and its accumulation in edible and non-edible parts of vegetables. A pot experiment was conducted to investigate Ni uptake in three different leafy vegetables, spinach (Spinacia oleracea L.), lettuce (Lactuca sativa L.), and fenugreek (Trigonella foenum-graecum L.), grown in soil artificially contaminated with Ni at three different treatment levels (100mgkg-1, 200mgkg-1, and 300mgkg-1). The potential dietary toxicity of these vegetables in humans was examined by using an in vitro digestion model. The lowest and highest chlorophyll contents were detected in lettuce at 300mgkg-1 of Ni concentration and in control plants of spinach. Their values were 34.16 ± 3.01 (SPAD unit) and 53 ± 3.7673 (SPAD unit), respectively. Among the three vegetables, lettuce and spinach at 300mgkg-1 exhibited the highest accumulation of Ni, with 43mgkg-1 in edible parts and 182mgkg-1 in non-edible parts. Furthermore, health risk index (HRI) values were found to be > 1 for lettuce and fenugreek at Ni concentrations of 200 and 300mgkg-1 for both children and adults. The average bioaccessibility of Ni in lettuce, fenugreek, and spinach during the gastrointestinal phase was 32-23%, 24-10%, and 45-37%, respectively, at a Ni concentration of 300mgkg-1. All three vegetables grown on Ni-contaminated soil may potentially contribute to food chain toxicity. The HRI values being > 1 suggest that these vegetables are unsafe for consumption. Monitoring of Ni concentration in leafy vegetables is essential to minimize human health risks associated with food chain contamination.

A comparison of nickel and zinc uptake and translocation in three species of Brassicaceae: The Ni hyperaccumulator Odontarrhena corsica and two non‐hyperaccumulators, Aurinia saxatilis and Lobularia maritima

AbstractThe uptake and translocation of nickel (Ni) and zinc (Zn) were compared in hydroponics in three species of Brassicaceae, Lobularia maritima, Aurinia saxatilis, and Odontarrhena corsica at 2 and 10 μM Ni or Zn in the nutrient solution. Odontarrhena corsica, which is a known hyperaccumulator of Ni, but not of Zn, accumulated significantly more Ni in its roots and shoots than did L. maritima and A. saxatilis, which are both non‐hyperaccumulators. The Ni translocation factor and Ni uptake were by far the highest in O. corsica, compared to L. maritima and A. saxatilis. The Zn translocation factor was significantly higher in L. maritima than in A. saxatilis and O. corsica. In the 10‐μM Zn treatment, the Zn uptake was strongly and significantly higher in O. corsica than in L. maritima and A. saxatilis. Aurinia saxatilis is clearly an excluder, with low uptake and translocation, both for Ni and Zn. Of all the species, L. maritima showed by far the highest Zn translocation levels, both at 2 and 10 μM Zn in the nutrient solution (TF = ±0.4, compared to ±0.1 in A. saxatilis and O. corsica). Also its Ni translocation approached hyperaccumulator‐like level (TF = ±1), though only in the 10‐μM Ni treatment and still much lower than in O. corsica.

Co-exposure to tire wear particles and nickel inhibits mung bean yield by reducing nutrient uptake.

Soil and terrestrial contamination with microplastics and nanoplastics has been discussed extensively, while tire wear particles (TWPs) have been largely overlooked. We investigated the root-surface interactions and growth response of mung bean (Vigna radiata L.) plants exposed to tire wear particles (TWPs) (0.05, 0.1, and 0.25% w/w) and nickel sulfate (50 and 100 mg kg-1 NiSO4) alone and in co-exposure scenarios for the full life cycle (105 days) under soil conditions. The results show that TWPs adhered to the root surface and reduced the water and nutrient uptake by the plant, particularly at higher concentrations of TWPs (0.25% w/w), without any observed organic contaminant accumulation in the root tissue. TWPs alone at 0.01, 0.1, and 0.25% (w/w) decreased mung bean yield by 11, 28, and 52%, respectively. Co-exposure to TWPs at 0.01, 0.1 and 0.25% w/w with 100 mg kg-1 NiSO4 decreased yield by 73, 79 and 88%, respectively. However, co-exposure to TWPs at 0.01 and 0.1% w/w with 50 mg kg-1 NiSO4 enhanced the yield by 32% and 7%, respectively. These changes in yield and nutritional aspects appear to be linked to Ni's regulatory influence on mineral homeostasis. Moreover, exposure to NiSO4 at 100 mg kg-1 increased Ni uptake in the root, shoot, and grain by 9, 26, and 20-fold, respectively as compared to the unamended control; this corresponded to increased antioxidant enzyme activity (10-127%) as compared to the control. TWPs caused blockages, significantly reducing plant yield and altering nutrient dynamics, highlighting emerging risks to plant health.

Olivine avoidance behaviour by marine gastropods (Littorina littorea L.) and amphipods (Gammarus locusta L.) within the context of ocean alkalinity enhancement

Gigaton scale atmospheric carbon dioxide (CO2) removal (CDR) is needed to keep global warming below 1.5 °C. Coastal enhanced olivine weathering is a CDR technique that could be implemented in coastal management programmes, but its CO2 sequestration potential and environmental safety remain uncertain. Large scale olivine spreading would change the surficial sediment characteristics, which could potentially reduce habitat suitability and ultimately result in community composition changes. To test this hypothesis, we investigated the avoidance response of the marine gastropod Littorina littorea (Linnaeus, 1758) and marine amphipod Gammarus locusta (Linnaeus, 1758) to relatively coarse (83 – 332 µm) olivine and olivine-sediment mixtures during short-term choice experiments. Pure olivine was significantly avoided by both species, while no significant avoidance was observed for sediment with 3% or 30% w/w olivine. For L. littorea, aversion of the light green colour of pure olivine (i.e. positive scototaxis) was the main reason for avoidance. Moreover, olivine was not significantly avoided when it was 7.5 cm (45%) closer to a food source/darker microhabitat (Ulva sp.) compared to natural sediment. It is inferred that the amphipod G. locusta avoided pure olivine to reduce Ni and Cr exposure. Yet, a significant increase in whole body Ni concentrations was observed after 79 h of exposure in the 30% and 100% w/w olivine treatments compared to the sediment control, likely as a result of waterborne Ni uptake. Overall, our results are significant for ecological risk assessment of coastal enhanced olivine weathering as they show that L. littorea and G. locusta will not avoid sediments with up to 30% w/w relatively coarse olivine added and that the degree of olivine avoidance is dependent on local environmental factors (e.g. food or shelter availability).

Applicability of the sigmoid model to estimate heavy metal uptake in maize and sorghum as affected by organic acids.

Although assisted phytoremediation using chemical treatments is a suitable technique for the removal of heavy metals (HMs), the estimation of this process using simple models is also crucial. For this purpose, a greenhouse trial was designed to evaluate the effectiveness of citric, oxalic, and tartaric acid on Cd, Pb, Ni, and Zn phytoremediation by maize and sorghum and to estimate this process using sigmoid HMs uptake model. Results showed that mean values of root and shoot dry weight and metals uptake, translocation factor (TF) of Pb and Zn, and uptake efficiency (UE) of Cd in maize were higher than sorghum but the TF of Cd and the phytoextraction efficiency (PEE) and UE of Pb in sorghum were higher than maize. Citric, oxalic, and tartaric acid significantly increased the UE of Pb by 17.7%, 22.5%, and 32.5%, respectively. Tartaric acid significantly increased the mean values of shoot dry weight, shoot Cd, Pb, and Ni uptake, and PEE of Pb and Ni, but decreased TF of Zn. The R2, NRMSE, and KM values indicated the ability of sigmoid HM uptake model in estimating HMs uptake in maize and sorghum treated with organic acids. Thus, tartaric acid was more effective than citric and oxalic acids to enhance phytoremediation potential. Sigmoid HM uptake model is suitable to estimate the HMs uptake in plants treated with organic acids at different growth stages.

Phytoremediation technology for recovery of Ni by Acacia plants in association with Bacillus amyloliquefaciens isolated from E-waste contaminated site

Electronic waste (e-waste) illegally disposal in Thailand is becoming more widespread. A sustainable metal recovery technology is needed. A phytotechnology called “phytomining” of metals such as nickel (Ni) is a promising technology providing a sustainable solution to the growing e-waste problems. This study investigated the ability of Acacia species in association with e-waste site isolated, plant growth-promoting rhizobacteria (PGPR), Bacillus amyloliquefaciens. Acacia mangium accumulated higher Ni in their tissues when Ni concentrations in soil were lower than 200 mg kg−1. The inoculation of PGPR B. amyloliquefaciens enhanced Ni uptake and accumulation in the leaves, stem, and root. The results showed that the highest Ni concentration was found in the root ash (825.50 mg kg−1) when inoculated plants were grown in soil containing 600 mg kg−1 Ni. Hence, the Ni recovery process and mass balance were performed on root ashes. The highest Ni recovery was 91.3% from the acid (H2SO4) leachate of the ash of inoculated plant treated with 600 mg kg−1 Ni. This demonstrates the feasibility of PGPR-assisted phytomining from Ni-contaminated soil. Phytomining of Ni from any e-waste contaminated sites using Acacia mangium in combination with B. amyloliquefaciens can promote plant growth and improve the uptake of Ni.

Adsorption characteristics of nickel (II) from aqueous solutions by Zeolite Scony Mobile-5 (ZSM-5) incorporated in sodium alginate beads

Nickel, a prevalent metal in the ecosystem, is released into the environment through various anthropogenic activities, leading to adverse effects. This research explored utilizing zeolite scony mobile-5 (ZSM-5) nanoparticles encapsulated in sodium alginate (SA) for nickel (II) removal from aqueous solutions. The adsorption characteristics of SA/ZSM-5 were examined concerning contact duration, initial metal ion concentration, pH level, temperature, and sorbent dosage. The findings revealed that a rising pH reduced Ni (II) uptake by the sorbent while increasing the Ni (II) concentration from 25 to 100 mg L−1 led to a decrease in removal percentage from 91 to 80% under optimal conditions. Furthermore, as sorbent dosage increased from 4 to 16 g L−1, uptake capacity declined from 9.972 to 1.55 mg g−1. Concurrently, SA/ZSM-5 beads' Ni (II) sorption capacity decreased from 96.12 to 59.14% with a temperature increase ranging from 25 to 55 °C. The Ni (II) sorption data on SA/ZSM-5 beads are aptly represented by Langmuir and Freundlich equilibrium isotherm models. Moreover, a second-order kinetic model characterizes the adsorption kinetics of Ni (II) on the SA/ZSM-5 beads. A negative free energy change (ΔG°) demonstrates that the process is both viable and spontaneous. The negative enthalpy values indicate an exothermic nature at the solid–liquid interface while negative entropy values suggest a decrease in randomness. In conclusion, this novel adsorbent exhibits promise for removing nickel from aqueous solutions and could potentially be employed in small-scale industries under similar conditions.

Histological and ionomics assessment to elucidate tolerance mechanisms of nickel-tolerant and sensitive cultivars of bread wheat (Triticum aestivum L.)

Recent literature has raised concerns over crop safety due to nickel (Ni) contamination of irrigation water and agricultural soil in Pakistan. Consequently, wheat crop has suffered in terms of nutrient disbalance and yield reduction. Therefore, it is important to screen tolerant wheat cultivars against Ni toxicity with the ability to accumulate low concentration in grains. In this regard, two wheat cultivars (SKD-1 and Borlaug-16) were exposed to Ni stress (100 mg/L) in a pot experiment for 21 days. In the present study, trace elements (As, Cr, Cu, Cd, Mn, Hg, Ni, Pb, and Zn) and mineral nutrients (Ca, Fe, K, Mg, Na, and P) were tested by ICP-OES. To understand tolerance mechanisms, wheat tissues were tested for morphological parameters, anatomical alteration, oxidative stress, and antioxidant capacity. The translocation of Ni was higher in SKD-1 (0.62) compared to Borlaug-16 (0.45) due to low Ni accumulation in roots of Borlaug-16. In the roots of Borlaug-16, trace elements (Cr, Cu, Mn, Pb, and Zn) were comparatively higher than SKD-1. On the contrary, nutrients (Ca, Fe, Mg, Na, and P) were higher in leaves of SKD-1. Under Ni stress, the root anatomy of Borlaug-16 exhibited a marked increase in the cellular thickness of the cortex by 130.38% and stele by 46.2%. Conversely, the bundle sheath cell thickness rose by 68.36% in the SKD-1. In terms of leaf anatomy, Borlaug-16 showed enhanced thickness in the xylem by 13.01% and bundle sheath cells by 84.95%. Meanwhile, the upper epidermis and phloem of SKD-1 registered thickness increases of 21.80% and 24.47% under Ni stress. Oxidative stress (MDA and H2O2) was comparatively highly induced in SKD-1 tissues compared to Borlaug-16. On the other hand, antioxidants (SOD, CAT, and APX) were comparatively higher in root and leaf tissues of Borlaug-16. The lower Ni uptake, less cellular damage, and high antioxidant capacity of Borlaug-16 makes it more tolerant to Ni stress. Such findings will pave the way towards sustainable crop production.

Methanogens acquire and bioaccumulate nickel during reductive dissolution of nickelian pyrite.

Nickel (Ni) is a key component of the active site metallocofactors of numerous enzymes required for methanogenesis, including [NiFe]-hydrogenase, carbon monoxide dehydrogenase, and methyl CoM reductase, leading to a high demand for Ni among methanogens. However, methanogens often inhabit euxinic environments that favor the sequestration of nickel as metal-sulfide minerals, such as nickelian pyrite [(Ni,Fe)S2], that have low solubilities and that are not considered bioavailable. Recently, however, several different model methanogens (Methanosarcina barkeri, Methanococcus voltae, Methanococcus maripaludis) were shown to reductively dissolve pyrite (FeS2) and to utilize dissolution products to meet iron and sulfur biosynthetic demands. Here, using M. barkeri Fusaro, and laboratory-synthesized (Ni,Fe)S2 that was physically isolated from cells using dialysis membranes, we show that trace nickel (<20 nM) abiotically solubilized from the mineral can support methanogenesis and limited growth, roughly fivefold less than the minimum concentration known to support methanogenesis. Furthermore, when provided direct contact with (Ni,Fe)S2, M. barkeri promoted the reductive dissolution of (Ni,Fe)S2 and assimilated solubilized nickel, iron, and sulfur as its sole source of these elements. Cells that reductively dissolved (Ni,Fe)S2 bioaccumulated approximately fourfold more nickel than those grown with soluble nickel and sulfide but had similar metabolic coupling efficiencies. While the mechanism for Ni uptake in archaeal methanogens is not known, homologs of the bacterial Nik uptake system were shown to be ubiquitous across methanogen genomes. Collectively, these observations indicate that (Ni,Fe)S2 is bioavailable in anoxic environments and that methanogens can convert this mineral into nickel-, iron-, and sulfur-containing metalloenzymes to support methanogenesis and growth. IMPORTANCE Nickel is an essential metal, and its availability has changed dramatically over Earth history due to shifts in the predominant type of volcanism in the late Archean that limited its availability and an increase in euxinic conditions in the early Proterozoic that favored its precipitation as nickel sulfide minerals. Observations presented herein indicate that the methanogen, Methanosarcina barkeri, can acquire nickel at low concentration (<20 nM) from soluble and mineral sources. Furthermore, M. barkeri was shown to actively reduce nickelian pyrite; use dissolution products to meet their iron, sulfur, and nickel demands; and bioaccumulate nickel. These data help to explain how M. barkeri (and possibly other methanogens and anaerobes) can acquire nickel in contemporary and past anoxic or euxinic environments.

The effects of temperature on nickel bioaccumulation and toxicity in the freshwater snail Lymnaea stagnalis

It is well known that temperature can have important effects on the toxicity of metals (and other contaminants) to aquatic organisms. To date, research has mostly focused on thermal effects on acute metal toxicity, and there is a data gap on thermal effects on chronic metal toxicity to sensitive organisms that are particularly relevant to environmental risk assessment. This latter research is especially needed in the context of increased global temperature and heat waves frequency associated with climate change. We investigated temperature effects on chronic nickel (Ni) bioaccumulation and toxicity to the metal-sensitive freshwater snail Lymnaea stagnalis. In the laboratory, we conducted a series of experiments with juvenile snails that were pre-acclimated to different temperatures since their embryonic stage. We found that temperature and nickel separately had strong effects on juvenile growth rate and survival. Rising temperature from 18 to 26 °C had no noticeable effect on Ni-induced growth inhibition and Ni bioaccumulation in juvenile L. stagnalis exposed over 40 days to 0, 30 and 60 μg L−1 of dissolved Ni. These results agreed with estimates of Ni uptake and elimination rates (ku and ke), which were either unaffected by temperature or increased by similar factors from 18 to 26 °C. On the other hand, a temperature increase from 18 to 26 °C appeared to exacerbate Ni lethality to juvenile snails in the 40-day toxicity test. This exacerbation might have been due to a combination of factors, including detrimental changes in metabolically available Ni pools and/or to sensitization of the organism under sub-optimal temperatures. Overall, our study shows that thermal effects on metal chronic toxicity are complex, with effects that can be response-specific and not directly related to metal toxicokinetic.

Metal Accumulation and Tolerance of Energy Willow to Copper and Nickel under Simulated Drought Conditions

The aim of this study was to determine the effect of drought on the accumulation and tolerance of energy willow (Salix viminalis L. var. ‘Gigantea’) to copper (Cu) and nickel (Ni) in the context of phytoremediation potential of the plant and biomass production under adverse water conditions. Drought was simulated with polyethylene glycol (PEG-6000. 5%), and metals were added at a concentration of 1 mM. Plants were cultivated in greenhouse conditions for 21 days according to the experimental variants: control, Cu, Ni, PEG, PEG + Cu and PEG + Ni. The results indicate high toxicity of Cu (chlorosis, necrosis, decrease in biomass, plant dehydration, increase in the content of proline and phenolic compounds), and PEG + Cu co-treatment increased the toxicity of the metal. Ni applied at the same concentration did not cause toxicity symptoms. The willow exhibits the ability to accumulate Ni, and mutual application of PEG + Ni increased Ni uptake to new shoots. Cu caused elevated accumulation of proline and phenolics in leaves accompanied with a decreased carbon and nitrogen content in roots in favor of young shoots. Both metals and drought led to disruption in the content of mineral nutrients (Ca, Mg, Fe). Due to high tolerance to Ni and drought, S. viminalis var. ‘Gigantea’ bears high potential for biomass production on Ni-polluted sites with accompanying metal uptake increased under water deficit.

The Content, Uptake and Bioaccumulation Factor of Copper and Nickel in Grass Depending on Zinc Application and Organic Fertilization

Different content of Zn in the soil and organic fertilization can affect micronutrient uptake by plants. A pot experiment was carried out to determine the impact of increasing Zn application rates, i.e., 200, 400 and 600 Zn mg·kg−1, in combination with bovine and chicken manures and mushroom substrate on Cu and Ni content, uptake and bioaccumulation factor in cocksfoot (Dactylis glomerata L.). Control objects without Zn and organic fertilizers and after application of only different Zn doses and only organic fertilizers were also tested. Application of Zn at 400 and 600 mg·kg−1 significantly decreased the content, uptake and value of bioaccumulation factor of Cu in the grass. Different Zn doses were not found to influence the content and bioaccumulation factor of Ni in cocksfoot, but application at 200 Zn mg·kg−1 increased Ni uptake. Chicken manure increased the content and bioaccumulation factor of Cu and Ni in the test plant, and all the organic fertilizers increased their uptake. Cocksfoot showed no tendency to excessive bioaccumulation of Cu and Ni.