Ni Supply Research Articles

Unravelling the fate of foliar-applied nickel in soybean: a comprehensive investigation

Background and aimsNickel (Ni) deficiency has been reported to occur in soybean (Glycine max) grown on leached tropical soils in Brazil. We aimed to determine whether an internal or external Ni supply can compensate for low Ni within the seed by assessing whether the amount of Ni in the seed whether the foliar-application of aqueous NiSO4 influenced the uptake of Ni by the leaf, the nutritional status of the plant, urease activity and growth.MethodsWe used Ni-depleted seeds (<0.35 μg Ni per g) and Ni-sufficient seeds (11.1 μg Ni g−1) for hydroponic experiments. Seedlings were grown either with or without an external Ni supply (0 or 0.85 μM Ni in nutrient solution) and either with or without an internal Ni supply (with or cotyledons removed). In addition, we used synchrotron-based micro-X-ray fluorescence analysis to examine the distribution of foliar-applied Ni (50 and 100 mg L-1).Key resultsLeaf Ni concentration and urease activity were both enhanced by increasing either the internal (cotyledon seed store) or external (solution) Ni supply. In addition, plants derived from Ni-depleted seed that received external Ni supply had 9.2% higher biomass relative to plants derived from Ni-sufficient seeds which received Ni. When foliar-applied, Ni accumulated in the pedicles of the trichomes within 15 minutes of application, and then moved to the vascular bundles before dispersing further into tissues within 3 hours.ConclusionsTrichomes are an important pathway for foliar Ni absorption in soybean, but there are still major knowledge gaps our understanding of the physiological function of trichomes in the uptake of metal ions from foliar micro-nutrient treatments.

Physiological and Biochemical Responses of Pepper (Capsicum annuum L.) Seedlings to Nickel Toxicity.

Globally, heavy metal pollution of soil has remained a problem for food security and human health, having a significant impact on crop productivity. In agricultural environments, nickel (Ni) is becoming a hazardous element. The present study was performed to characterize the toxicity symptoms of Ni in pepper seedlings exposed to different concentrations of Ni. Four-week-old pepper seedlings were grown under hydroponic conditions using seven Ni concentrations (0, 10, 20, 30, 50, 75, and 100 mg L–1 NiCl2. 6H2O). The Ni toxicity showed symptoms, such as chlorosis of young leaves. Excess Ni reduced growth and biomass production, root morphology, gas exchange elements, pigment molecules, and photosystem function. The growth tolerance index (GTI) was reduced by 88-, 75-, 60-, 45-, 30-, and 19% in plants against 10, 20, 30, 50, 75, and 100 mg L–1 Ni, respectively. Higher Ni concentrations enhanced antioxidant enzyme activity, ROS accumulation, membrane integrity [malondialdehyde (MDA) and electrolyte leakage (EL)], and metabolites (proline, soluble sugars, total phenols, and flavonoids) in pepper leaves. Furthermore, increased Ni supply enhanced the Ni content in pepper’s leaves and roots, but declined nitrogen (N), potassium (K), and phosphorus (P) levels dramatically. The translocation of Ni from root to shoot increased from 0.339 to 0.715 after being treated with 10–100 mg L–1 Ni. The uptake of Ni in roots was reported to be higher than that in shoots. Generally, all Ni levels had a detrimental impact on enzyme activity and led to cell death in pepper seedlings. However, the present investigation revealed that Ni ≥ 30 mg L–1 lead to a deleterious impact on pepper seedlings. In the future, research is needed to further explore the mechanism and gene expression involved in cell death caused by Ni toxicity in pepper plants.

Intermetallic compound formation and growth behavior at the interface between indium and Au/Ni(V) metallization

Pure indium (In) solder is promising as the thermal interface material (TIM) for efficient heat dissipation and as the Pb-free solder for cryogenic joining applications. In this study, liquid/solid and solid/solid reactions between In and Au/Ni(V) surface finish on a Si chip are investigated to explore the formation of intermetallic compounds (IMCs) formed at the In/Au/Ni(V) interface and their growth kinetics. Two IMCs, (Ni,Au)28In72 and Ni-V-In, are formed at the interface in the liquid/solid and solid/solid reactions performed at 220–260 °C and 100–150 °C, respectively. The growth of the (Ni,Au)28In72 crystalline phase follows the parabolic law and the underlying Ni-V-In amorphous phase is formed as a result of phase transformation from original Ni(V) due to outward diffusion of Ni and inward diffusion of In. This phase transformation proceeds at a faster rate in the liquid/solid reaction. The Ni supply is exhausted once the Ni(V) is completely transformed into the Ni-V-In phase, accelerating the ripening reaction of (Ni,Au)28In72 and its spallation into the molten In matrix.

Hazardous Impact of Nickel in Alteration of Antioxidative Mechanism and Inhibition of Growth and Biomass Yield in Rice (Oryza sativa L.)

Many anthropogenic activities (smelters, mines and municipal waste) enhance the heavy metal toxicity in soil and water and it is gradually accumulated in plants, and finally through food chain it reaches to human beings. To investigate hazardous impact of excess nickel on growth, biomass, yield and metabolism of rice (Oryza sativa L) the plants were grown in refined sand at 0.0001mM (control), 0.05, 0.10, 0.20, 0.40, and 0.50 mM nickel (Ni) supply. After 16 days of treatment the excess supply of Ni(&gt;0.50mM) reduced biomass, photosynthetic pigments (both chlorophyll a and b), Hill reaction activity, water soluble proteins, activity of catalase (CAT), and enhanced the activity of peroxidase (POX), ribonuclease and acid phosphatase in rice leaves. The antioxidative regulation was inhibited through CAT, although increased activity of POX supported the plants in overcoming the toxic effect of nickel. At 112 days (70 days after Ni treatment) the accumulation of iron in shoot and root was reduced. Phosphorus was significantly increased in both shoot and root. Sulphur accumulation was increased in panicle, leaves, shoot and root. Nickel accumulation in different plant parts was increased many fold (as in leaves it was increased about 25 times, in stem 18 times and in roots it was 17 times) in 0.50 mM Ni supply in comparision to control. Rice appeared very prone to nickel toxicity as Ni supply beyond 0.050 mM resulted into complete loss of economic yield due to inhibited flowering and poor panicle numbers.

Global continental volcanism controlled the evolution of the oceanic nickel reservoir

Wanning nickel (Ni) abundances in the Neoarchean may have led to a decline in marine methanogenic bacteria due to the loss of a key micronutrient, causing a collapse in atmospheric methane levels and the subsequent rise of atmospheric oxygen – the Great Oxidation Event ∼2.5 Ga. However, this hypothesis currently lacks geological evidence that corroborates the processes that led to a decline in the supply of Ni to the oceans at that time. Here we investigate temporal variations of Ni concentrations in the likely source rocks – various volcanic lithologies - spanning the past 3.5 Byr. By applying a spatially gridded resampling to geochemical data from a global compilation of ∼96,000 continental volcanic rocks, we show that komatiites and basaltic-andesitic rocks largely controlled Ni fluxes to the Earth's surface during the Archean but had a waning influence thereafter due to the secular cooling of the mantle. A new compilation of marine shales (397 samples) and an updated compilation of banded iron formations (2037 samples) further confirms a declining clastic and dissolved supply of terrestrial Ni, respectively. Interestingly, we further observed a stable marine Ni concentration for the last 2 Byr. To explain this unexpected trend, we provide a computational model of mantle melting demonstrating that increasing melting pressures likely inhibited a further decline of Ni concentration in volcanic rocks and led to this relative consistency in Ni supply.

Biochemical and physiological responses of soybean [Glycine max (L.) Merrill] to nickel toxicity

ABSTRACT Nickel (Ni) was the latest element to have its nutritional essentiality recognized for plants (Brown et al. 1987). It is a component of various enzymes, including glyoxalases (family I), hydrogenases, superoxide dismutase and urease (Chen et al. 2009). Inadequate Ni supply promotes changes in the plant metabolism, including processes related to nitrogen metabolism, such as amino acids, urea and ureides metabolisms (Rodriguez-Jimenez et al. 2016; Bai et al. 2006). Legumes that are dependent on N2 fixation (e.g., soybean) have their process impaired by Ni deficiency, because this element is an essential catalytic cofactor of [NiFe]-hydrogenase, an enzyme found in some symbiotic bacteria that recycles the H2 produced by a side reaction of nitrogenase in root nodules formed by the plant-bacteria association (Cammack 1995; Bagyinka 2014). Moreover, Ni has shown the potential to control soybean diseases, such as powdery mildew (Barcelos et al. 2018) and Asian soybean rust (Einhardt et al. 2020a; 2020b).

Amorphization and intermetallic nucleation in early-stage interfacial diffusion during Sn-solder/Ni solid-state bonding

As low-temperature interconnection processes for integrated circuit packaging increase in demand, a deeper understanding of the solid-state diffusion behavior between the bonding metals forming chip-to-chip joints is needed for process development and evaluation. In this study, by using a special electrodeposited Ni microcone layer to bond with solder at a solid state temperature of 200 °C, the role of early-stage interfacial diffusion in the formation of bonding could be interpreted. High-resolution microscopic observation revealed different diffusion products at different locations of the contacting solder and Ni microcones, which indicated the sequential formation of an amorphous layer and intermetallic compound (IMC) grains upon initial contact. The morphology and composition of the IMC grains formed at the solid-state contact interface were also influenced by the contact compactness and solder composition, owing to the distinct Ni supply conditions. A low bonding temperature of 100 °C resulted in poor interfacial adhesion and no visible product of diffusion, which corroborated that the interfacial diffusion product, even with a thickness on nanometer scale, can be an effective indicator of bimetal bonding for the low-temperature interconnection process.

Effect of Site Specific Nitrogen Management on Seed Nitrogen—A Driving Factor of Winter Oilseed Rape (Brassica napus L.) Yield

It has been assumed that the management of both soil and fertilizer N in winter oilseed rape (WOSR) is crucial for N accumulation in seeds (Nse) and yield. This hypothesis was evaluated based on field experiments conducted in 2008/09, 2009/10, 2010/11 seasons, each year at two sites, differing in soil fertility, including indigenous N (Ni) supply. The experimental factors consisted of two N fertilizers: N and NS, and four Nf rates: 0, 80, 120, 160 kg ha−1. Yield, as governed by site × Nf rate interaction, responded linearly to Nse at harvest. The maximum Nse (Nsemax), as evaluated by N input (Nin = Ni + Nf) to WOSR at spring regrowth, varied from 95 to 153 kg ha−1, and determined 80% of yield variability. The basic reason of site diversity in Nsemax was Ni efficiency, ranging from 46% to 70%, respectively. The second cause of Nse variability was a shortage of N supply from + 9.5 soil to −8.8 kg ha−1 to the growing seeds during the seed filling period (SFP). This N pool supports the N concentration in seeds, resulting in both seed density and a seed weight increase, finally leading to a yield increase.

Cellular oxidative damage and impairment on the photosynthetic apparatus caused by Asian Soybean Rust on soybeans are alleviated by nickel

One of the most severe diseases affecting soybean is the Asian Soybean Rust (ASR) caused by Phakopsora pachyrhizi H. Sydow & P. Sydow. The oxidative damage in cellular constituents and the disruption in the photosynthetic apparatus are the major negative effects of ASR on soybean plants. Considering the importance of nickel (Ni) on plant metabolism, this study evaluated the effect of foliar Ni-supply on ASR control, reactive oxygen species (ROS) accumulation, activities of antioxidant enzymes, parameters related to photosynthesis, and sugars levels on soybean plants. ASR severity decreased by 34% due to Ni supply. Infected and Ni-supplied (+ Ni) plants showed lower malondialdehyde level and superoxide (O2−) and hydrogen peroxide (H2O2) accumulation in contrast to infected leaf tissues of non-Ni-supplied (− Ni) plants. The antioxidant enzymes activities were inefficient to avoid the high ROS accumulation for − Ni inoculated plants. The photosynthetic pigments, maximum photochemical efficiency of photosystem II (PSII), effective yield of PSII, electron transport rate, rate of net carbon assimilation, stomatal conductance to water vapor, and transpiration rate values were higher and the yield for other non-regulated losses and internal CO2 concentration values were lower for + Ni inoculated plants compared to − Ni inoculated plants. High ROS production and the greater damage to the photosynthetic apparatus caused by P. pachyrhizi infection on − Ni plants affected the synthesis of the sugars. The infection also decreased the plant’s energetic reserves faster in − Ni plants compared to + Ni plants. In conclusion, the cellular oxidative damage and the impairment on the photosynthetic apparatus of soybean plants caused by P. pachyrhizi infection were alleviated by supplying Ni foliarly.

Soybean seed chemical composition as influenced by Bradyrhizobium inoculation in soils with elevated nickel concentrations

Symbiotic nitrogen-fixing bacteria, rhizobia, besides their intrinsic ability to fix atmospheric nitrogen (N), may influence other element concentrations in leguminous plants. Adequate nickel (Ni) supply is of special importance for growth and N status of soybean, due to the role Ni holds as an enzyme component involved in N metabolism. However, high soil Ni availability also represents risks. Therefore, the objective of the study was to evaluate the effects of rhizobium inoculation on yield and the chemical composition (N, C, S, P, K, Ca, Mg, Cu, Fe, Mn, Zn, Ni) of soybean seeds produced on two soils with elevated total Ni concentrations (59 and 106 mg kg−1 of soil). The genetic characterisation of investigated rhizobial strains and screening for plant growth promoting traits were also performed. The field experiments included 9 treatments where soybean seeds were inoculated with different single rhizobial strains, a treatment with mineral fertilizer application, as well as a non-inoculated control (Ø). Most of the strains belonged to the genus Bradyrhizobium and produce the plant hormone indole-3-acetic acid. Bradyrhizobium inoculations significantly increased the soybean seed yield (up to 125%) and N%, and decreased Ni (up to 48%), P, Fe, Cu and Zn seed concentrations compared to the control Ø, depending on the strain and location. Soybean seed Ni concentrations were significantly influenced by treatment, location and their interaction and varied from 6.28 to 22.25 mg kg−1. There were no significant differences in C, S, Ca, Mg concentrations between treatments. Uptake of all nutrients by seeds in inoculated treatments was generally increased or similar, compared to the control Ø. Concentrations and uptake of Ni in inoculated treatments in both locations were significantly decreased compared to mineral fertilization. The study showed that inoculation with Bradyrhizobium strains effective in nitrogen fixation, together with yield increase may reduce the Ni concentrations in soybean seeds in organic cultivation systems of soybean.

H2 accumulation and N2 fixation variation by Ni limitation in Cyanothece

AbstractNi is an essential cofactor in NiFe‐uptake hydrogenase, an enzyme regulating H2 metabolism in diazotrophic cyanobacteria, the major H2 producers in the surface ocean globally. Here, we investigated the effect of Ni supply on H2 production and N2 fixation by using a model marine cyanobacterial diazotroph, Cyanothece. By mediating total dissolved Ni concentrations from 100 to 0.03 nmol L−1 in a trace metal‐defined culture medium, we demonstrated that Ni deficiency results in H2 accumulation, coupled with decreasing Ni quotas, growth rates, and occasionally relatively low N2 fixation rates. These results indicate that Ni deficiency limits the growth of the Cyanothece to some extent, considerably decreases H2 uptake by hydrogenase and leads to H2 accumulation and N2 fixation variation in the diazotroph. The findings show that Ni availability is a critical factor on controlling H2 production and N2 fixation in marine diazotrophic cyanobacteria. The information of Ni bioavailability for diazotrophic cyanobacteria is thus essential to evaluate the importance of Ni for H2 cycling and N2 fixation in oceanic surface waters.

Hidden Nickel Deficiency? Nickel Fertilization via Soil Improves Nitrogen Metabolism and Grain Yield in Soybean Genotypes.

Nickel (Ni)—a component of urease and hydrogenase—was the latest nutrient to be recognized as an essential element for plants. However, to date there are no records of Ni deficiency for annual species cultivated under field conditions, possibly because of the non-appearance of obvious and distinctive symptoms, i.e., a hidden (or latent) deficiency. Soybean, a crop cultivated on soils poor in extractable Ni, has a high dependence on biological nitrogen fixation (BNF), in which Ni plays a key role. Thus, we hypothesized that Ni fertilization in soybean genotypes results in a better nitrogen physiological function and in higher grain production due to the hidden deficiency of this micronutrient. To verify this hypothesis, two simultaneous experiments were carried out, under greenhouse and field conditions, with Ni supply of 0.0 or 0.5 mg of Ni kg−1 of soil. For this, we used 15 soybean genotypes and two soybean isogenic lines (urease positive, Eu3; urease activity-null, eu3-a, formerly eu3-e1). Plants were evaluated for yield, Ni and N concentration, photosynthesis, and N metabolism. Nickel fertilization resulted in greater grain yield in some genotypes, indicating the hidden deficiency of Ni in both conditions. Yield gains of up to 2.9 g per plant in greenhouse and up to 1,502 kg ha−1 in field conditions were associated with a promoted N metabolism, namely, leaf N concentration, ammonia, ureides, urea, and urease activity, which separated the genotypes into groups of Ni responsiveness. Nickel supply also positively affected photosynthesis in the genotypes, never causing detrimental effects, except for the eu3-a mutant, which due to the absence of ureolytic activity accumulated excess urea in leaves and had reduced yield. In summary, the effect of Ni on the plants was positive and the extent of this effect was controlled by genotype-environment interaction. The application of 0.5 mg kg−1 of Ni resulted in safe levels of this element in grains for human health consumption. Including Ni applications in fertilization programs may provide significant yield benefits in soybean production on low Ni soil. This might also be the case for other annual crops, especially legumes.

Interactive effects of spectral quality and trace metal availability on the growth of Trichodesmium and Symbiodinium.

Light and trace metals are critical growth factors for algae but how the interdependence of light quality and metal availability affects algal growth remains largely unknown. Our previous studies have demonstrated the importance of Ni and Fe on the growth of Trichodesmium and Symbiodinium, respectively, two important marine primary producers inhabiting environments with high light intensities. Here, we investigated the effects of light quality and intensity with availability of either Ni or Fe on their growth. For Trichodesmium, we found that specific growth rates for high Ni treatments were all significantly higher than in corresponding low Ni treatments with varying light quality and intensity. The inhibitory effect of low intensity red light was also countered by sufficient Ni supply. For Symbiodinium, we found that growth rates and biomass were reduced by 75% under low intensity red light and the stress can only be partially relieved by sufficient Fe supply. The results show that trace metal availability plays an important role in relieving the stress induced by low red light condition for both Trichodesmium and Symbiodinium although the cyanobacterium performs better in this growth condition. The difference may be attributed to the presence of phycocyanin, a unique pigment attuned to absorption of red light, in Trichodesmium. Our study shows that the concerted effects of light intensity and quality compounded with trace metal availability may influence the growth of photosynthetic organisms in the ocean.

Nickel Availability in Soil as Influenced by Liming and Its Role in Soybean Nitrogen Metabolism.

Nickel (Ni) availability in soil varies as a function of pH. Plants require Ni in small quantities for normal development, especially in legumes due its role in nitrogen (N) metabolism. This study investigated the effect of soil base saturation, and Ni amendments on Ni uptake, N accumulation in the leaves and grains, as well as to evaluate organic acids changes in soybean. In addition, two N assimilation enzymes were assayed: nitrate reductase (NR) and Ni-dependent urease. Soybean plants inoculated with Bradyrhizobium japonicum were cultivated in soil-filled pots under two base-cation saturation (BCS) ratios (50 and 70%) and five Ni rates – 0.0; 0.1; 0.5; 1.0; and 10.0 mg dm-3 Ni. At flowering (R1 developmental stage), plants for each condition were evaluated for organic acids (oxalic, malonic, succinic, malic, tartaric, fumaric, oxaloacetic, citric and lactic) levels as well as the activities of urease and NR. At the end of the growth period (R7 developmental stage – grain maturity), grain N and Ni accumulations were determined. The available soil-Ni in rhizosphere extracted by DTPA increased with Ni rates, notably in BCS50. The highest concentrations of organic acid and N occurred in BCS70 and 0.5 mg dm-3 of Ni. There were no significant differences for urease activity taken on plants grown at BSC50 for Ni rates, except for the control treatment, while plants cultivated at soil BCS70 increased the urease activity up to 0.5 mg dm-3 of Ni. In addition, the highest values for urease activities were reached from the 0.5 mg dm-3 of Ni rate for both BCS treatments. The NR activity was not affected by any treatment indicating good biological nitrogen fixation (BNF) for all plants. The reddish color of the nodules increased with Ni rates in both BCS50 and 70, also confirms the good BNF due to Ni availability. The optimal development of soybean occurs in BCS70, but requires an extra Ni supply for the production of organic acids and for increased N-shoot and grain accumulation.

低合金焼結金属歯車の疲労強度

Most widely used high strength sintered steel is the diffusion bonded Fe-4Ni-0.5Mo-1.5Cu alloy (Distaloy®AE). Recently volatility of Ni ingot price and supply issue forced the industry to consider using much leaner alloy. This paper describes the load bearing capacity of surface-rolled sintered metal gears made of a newly developed diffusion bonded Fe-0.5Ni-0.5Mo (Distaloy®AQ). Sintered metal gears were surface-rolled, and then case-carburized. The effects of surface rolling on surface properties were examined by measuring the porosities and hardness near the surfaces of the gears. Bending fatigue tests and running tests for the surface-rolled sintered metal gears were carried out. The effects of the surface-rolling on the load bearing capacity of sintered metal gears were determined, and the results were compared with the results for case-carburized wrought steel gears.

Implication of citrate, malate and histidine in the accumulation and transport of nickel in Mesembryanthemum crystallinum and Brassica juncea

Citrate, malate and histidine have been involved in many processes including metal tolerance and accumulation in plants. These molecules have been frequently reported to be the potential nickel chelators, which most likely facilitate metal transport through xylem. In this context, we assess here, the relationship between organics acids and histidine content and nickel accumulation in Mesembryanthemum crystallinum and Brassica juncea grown in hydroponic media added with 25, 50 and 100µM NiCl2. Results showed that M. crystallinum is relatively more tolerant to Ni toxicity than B. juncea. For both species, xylem transport rate of Ni increased with increasing Ni supply. A positive correlation was established between nickel and citrate concentrations in the xylem sap. In the shoot of B. juncea, citric and malic acids concentrations were significantly higher than in the shoot of M. crystallinum. Also, the shoots and roots of B. juncea accumulated much more histidine. In contrast, a higher root citrate concentration was observed in M. crystallinum. These findings suggest a specific involvement of malic and citric acid in Ni translocation and accumulation in M. crystallinum and B. juncea. The high citrate and histidine accumulation especially at 100µM NiCl2, in the roots of M. crystallinum might be among the important factors associated with the tolerance of this halophyte to toxic Ni levels.

Evaluation of Toxicity Level of Nickel on Growth, Photosynthetic Efficiency, Antioxidative Enzyme, and Its Accumulation in Cauliflower

A study was conducted to determine the toxicity level of nickel using cauliflower (Brassica oleracea L. var. botrytis) cv. Snowball grown in refined sand with complete nutrient solution for 79 days. At day 80, plants were separated into three lots. One lot was treated as the control (0.0001 mM Ni) while other two lots were supplied with excess nickel (Ni) at 0.1 and 0.5 mM. The toxicity symptoms of Ni appeared as chlorosis of young leaves. No curd was formed at 0.5 mM Ni supply. Excess Ni decreased biomass, chlorophyll, Hill reaction activity, and carbohydrate fraction, and enzyme activities of catalase, peroxidase, and acid phosphatase in leaves. Excess Ni increased concentration of starch, phenol, and nonprotein nitrogen and decreased protein nitrogen in leaves. Increase in Ni supply increased Ni concentration in all parts of cauliflower, whereas the concentration of phosphorus, sulfur, iron, and manganese decreased significantly.

Geochemical evolution of the banded iron formations of the Voronezh Crystalline Massif in the early Precambrian: Sources of matter and geochronological constraints

The banded iron formations (BIFs) of the Voronezh Crystalline Massif occur at three stratigraphic levels: Mesoarchean, Neoarchean, and Paleoproterozoic. In comparison with Paleoproterozoic BIFs, the Archean BIFs are enriched in TiO2, Al2O3, Cr, Ni, and REEs. All the BIFs are characterized by positive Eu anomalies, absence of Ce anomalies, and predominance of HREEs over LREEs. The Paleoproterozoic BIFs show no evidence of clastic or hydrothermal contamination. The low Ni/Fe ratios indicate that the BIFs are younger than 2.7 Ga and their formation was followed by a sharp drop of the level of the mantle Ni supply. On the other hand, very low (<1 ppm) U contents indicate the upper age of iron accumulation—no later than the Great Oxidation Event of ~2.47 Ga.

Fate of nickel and calcium in seedlings of the hyperaccumulator Berkheya coddii during germination

Little is known about Ni storage in seeds of hyperaccumulating plants and its possible role in the first stages of plant development. The aim of this study was to determine Ni distribution in seeds and seedlings during germination and to test its role during germination with and without an external Ni supply. Field-harvested seeds from the South African Ni-hyperaccumulator Berkheya coddii Roessler were germinated either in Ni-free deionised water or in ultramafic soil. Sections of seeds and seedlings were analyzed using micro-proton induced X-ray emission (micro-PIXE) in order to localise Ni and other elements. Results show that high amounts of Ni were stored within the seeds. In germinating seeds, Ni was located in different parts: the lower epidermis, margins of cotyledons, and the pericarp in the micropylar area. The Ni and Ca were not mobilised during germination sensu stricto. Emergence of the first leaf seemed to trigger the translocation of Ni and Ca within the seedling. Besides, no effect of Ni supply from soil on its redistribution could be established for the germination stage.

Remediation of Nickel-Contaminated Soil by Brassica juncea L. cv. T-59 and Effect of the Metal on Some Metabolic Aspects of the Plant

ABSTRACTAmong four cultivars of Brassica juncea L., viz., TM-4, TM-2, RH-30, and T-59, cv. T-59 was relatively more tolerant to nickel (Ni) toxicity based on the growth parameters, seedling vigor index, and metal tolerance index. Nickel application inhibited the activity of the nitrate-assimilating enzyme nitrate reductase in the roots, stem, and leaves, whereas the total organic nitrogen, proline, and activity of a polyamine-metabolizing enzyme, diamine oxidase, increased in this tolerant cultivar (T-59). It accumulated a good amount of Ni from the soil in its root and shoot (i.e., 6.0–6.51 μg Ni g−1 dry weight) during 2 months of cultivation with an 8.0 mM Ni supply in the soil. The data presented in this paper indicate that Ni tolerance and its removal by Indian mustard from subtropical Indian soil is cultivar dependent, possibly due to different genetic and physiological adaptations of the cultivars.