The tolerance of Empetrum nigrum to copper and nickel

Comparative Physiological and Transcriptomics Profiling Provides Integrated Insight into Melatonin Mediated Salt and Copper Stress Tolerance in Selenicereus undatus L

Selenicereus undatus L., (pitaya) is an important tropical fruit crop, and faces significant challenges from soil salinity and heavy metal toxicity. This study explores the role of melatonin (M) in enhancing stress tolerance in pitaya against salinity (S) and copper (Cu) toxicity, both individually and in combination (SCu). SCu stress reduced plant biomass by ~54%, while melatonin application mitigated stress effects and increased plant growth by ~73.26% under SCuM compared to SCu treatment. Antioxidant activities were also modulated by stress. Transcriptomic analysis revealed 21 differentially expressed genes (DEGs) common across stress treatments and 13 DEGs specific to combined melatonin with stress treatments involved in stress signaling, secondary metabolite biosynthesis, and photosynthesis. A weighted gene co-expression network analysis (WGCNA) identified four gene modules (brown, dark green, dark grey, and grey) significantly associated with phenotypic traits. A protein-protein interaction (PPI) network analysis highlighted 14 hub genes per module, including GH3, JAZ, PAL, CCR, and POD, implicated in MAPK signaling, phenylpropanoid biosynthesis, and hormone signaling pathways. Integration of DESeq2 and WGCNA identified 12 key stress-responsive genes strongly correlated with phenotypic traits. This study provides insights into regulatory mechanisms underlying stress responses and highlights candidate genes for developing stress-resilient S. undatus through breeding programs.

Phytochemical Profiling and Bioactivity Assessment of Teucrium capitatum L. Essential Oil and Extracts: Experimental and In Silico Insights

Background:Teucrium capitatum L., a member of the Lamiaceae family, is widely used in traditional medicine for its therapeutic properties. This study aims to analyze the chemical composition of its essential oil and extracts, evaluate their antimicrobial and antioxidant activities, and investigate the interactions of their bioactive compounds with biological targets using in silico methods to better understand their mechanisms of action. Methods: Essential oil was extracted via hydrodistillation from leaves collected in Morocco, while phenolic compounds were obtained through Soxhlet and decoction extraction methods. Gas chromatography-mass spectrometry (GC-MS) was used for chemical profiling. Antimicrobial and antioxidant activities were assessed using standard methods, including DPPH, FRAP, and TAC assays. Molecular docking was conducted to explore interactions between major constituents and biological targets. Results: GC-MS analysis revealed significant bioactive components in the essential oil, such as β-pinene (24.5%), α-cadinol (17.02%), and shyobunol (12.13%). Extracts (hydro-ethanolic, hydro-methanolic, and aqueous via decoction) were rich in poliumoside (27.74%) and cirsimaritin (28.22%). The essential oil and extracts showed significant antimicrobial activity, particularly against Staphylococcus aureus, Escherichia coli, Candida albicans, and Aspergillus niger. Antioxidant assays confirmed strong activity. Molecular docking results supported strong interactions of major compounds with key biological targets. Conclusions: The high presence of phenolic and flavonoid compounds in Teucrium capitatum extracts contributes to their strong antimicrobial and antioxidant properties, supporting their potential for development as natural therapeutic agents.

An assessment of in vitro lead (Pb) bioaccumulation of Dianthus chinensis L. (Chinese pink)

Heavy metals (HM) also known as potentially toxic elements (PTEs), are well-known environmental pollutants, among which lead (Pb) is a widespread and hazardous soil contaminant. Its removal from soil sediments is often difficult to achieve. In this study, in vitro experiments were conducted to investigate the bioaccumulation capability of Dianthus chinensis L. in solid and liquid Murashige and Skoog (MS) medium supplemented with varying concentrations (0, 10, 100, and 200 µM) of Pb as lead nitrate [Pb(NO3)2] for 30 days. The objectives of the study were to assess the efficiency of the selected plant as a bio-accumulator in the in vitro system and to obtain data on morphological, biochemical, and molecular changes during Pb salt-induced stress. Significant growth patterns of initial growth promotion up to 100 µM lead nitrate supplemented medium were observed, with maximum shoot length and biomass production along with remarkable lead bioaccumulation. Molecular studies on in vitro raised plantlets confirm the high degree of genetic uniformity (98.3%) of the selected plants after a considerable duration (30 days) of Pb exposure. Biochemical parameters revealed significant stress effects, including a 284% reduction in total chlorophyll content, altered carotenoid, and proline level during the study. The experiment revealed the high tolerance capacity of D. chinensis to Pb salt and its bioaccumulation potential (397.33 mg/kg). This increases the possible use of such an ornamental and floriculture plant as a prospective candidate for the efficient removal of soil Pb pollutants, as they can remediate soils, coupled with aesthetic and profitable outcomes for the growers.

Evaluation of soil pollution effects on maize (Zea mays) at selected Pb-Zn and limestone mine sites in Ebonyi State, Southeastern Nigeria

This research examined soil contamination and the uptake of potentially toxic elements (PTEs) by maize plants in mining communities. We collected 192 soil samples and 40 maize plant samples from two mining areas and a pristine site. We analyzed the physical properties and element content of the soil, including phosphorus, nitrogen, potassium, Fe, Zn, Co, Pb, Cd, Cr, and Ni. We also measured the elemental concentrations in the maize plants. The study found higher levels of Zn, Cu, and Pb at the mining sites compared to the control areas. The pollution factor (CF) indicated pollution with Cu > Pb > and > Zn at both mine sites. The pollution index (PLI) showed no pollution in the Nkalagu mine and control sites, but heavy and moderate pollution at the Ameka mine and control sites, respectively. The Ameka mine site was enriched with Zn. The bioaccumulation coefficient (BAC) was < 1 except for Zn at the Nkalagu mine and control site. The transfer factor for Fe and Zn from root to shoot was > 1. Pb was > 1 in all study areas except the Ameka mining areas. The results suggest remediation is needed for the two mine sites, especially at Ameka.

Impact of ethylene diamine tetraacetic acid on physiochemical parameters and yield attribute in two varieties of Brassica juncea under lead stress

Lead (Pb) is one of the most toxic elements on earth. The harmful effects of Pb at higher concentrations were seen on plant vegetation because plants are directly exposed towards it. Indian mustard, a well-known hyperaccumulator plant is the most promising crop for the environment, engaged in a variety of scenarios for ecological cleanup. In the present study, we used ethylene diamine tetraacetic acid (EDTA), a chelating agent that is of remarkable efficiency. The pot experiments were conducted in soil pretreated with 1000 mgkg-1 Pb with different concentrations of EDTA (2-10 mmol). All the growth parameters were reduced significantly in the plants treated with Pb and EDTA, however, a non-significant effect was observed in 5 mmol EDTA compared to Pb alone treatment. Photosynthetic pigments yield, nitrate reductase activity and NPK content were affected negatively; in contrast, superoxide dismutase and catalase activity was increased in Pb and Pb+EDTA treated in both the varieties. The Pb accumulation was elevated significantly by the augmentation of 5 mmol EDTA in both varieties. Accumulation of Pb in the shoot was higher in PM 25 than in P. Vijay, whereas root Pb accumulation showed the opposite, i.e., more Pb in roots of P. Vijay than PM 25. Moreover, The Pb accumulation per plant was observed more in P. Vijay as compared to PM 25. Hence, the present study implies that the augmentation of Pb-polluted soil with EDTA works well while dealing with B. juncea assisted phytoremediation and P. Vijay to be a stronger variety than PM 25. Further, 5 mmol of EDTA was optimum for phytoremediation of the soil polluted with up to 1000 mg Pb kg-1 soil.

Essential oil-grafted copper nanoparticles as a potential next-generation fungicide for holistic disease management in maize

Sustainable food production is necessary to meet the demand of the incessantly growing human population. Phytopathogens pose a major constraint in food production, and the use of conventional fungicides to manage them is under the purview of criticism due to their numerous setbacks. In the present study, essential oil-grafted copper nanoparticles (EGC) were generated, characterized, and evaluated against the maize fungal pathogens, viz., Bipolaris maydis, Rhizoctonia solani f. sp. sasakii, Macrophomina phaseolina, Fusarium verticillioides, and Sclerotium rolfsii. The ED₅₀ for the fungi under study ranged from 43 to 56 μg ml^-1, and a significant inhibition was observed at a low dose of 20 μg ml^-1 under in vitro conditions. Under net house conditions, seed treatment + foliar spray at 250 and 500 mg L^-1 of EGC performed remarkably against maydis leaf blight (MLB), with reduced percent disease index (PDI) by 27.116 and 25.292%, respectively, in two Kharif seasons (May-Sep, 2021, 2022). The activity of enzymatic antioxidants, viz., β-1, 3-glucanase, PAL, POX, and PPO, and a non-enzymatic antioxidant (total phenolics) was increased in treated maize plants, indicating host defense was triggered. The optimum concentrations of EGC (250 mg L^-1 and 500 mg L^-1) exhibited improved physiological characteristics such as photosynthetic activity, shoot biomass, plant height, germination percentage, vigor index, and root system traits. However, higher concentrations of 1,000 mg L^-1 rendered phytotoxicity, reducing growth, biomass, and copper bioaccumulation to high toxic levels, mainly in the foliar-sprayed maize leaves. In addition, EGC and copper nanoparticles (CuNPs) at 1,000 mg L^-1 reduced the absorption and concentration of manganese and zinc indicating a negative correlation between Cu and Mn/Zn. Our study proposes that the CuNPs combined with EO (Clove oil) exhibit astounding synergistic efficacy against maize fungal pathogens and optimized concentrations can be used as an alternative to commercial fungicides without any serious impact on environmental health.

Bioaccumulation level of metals and health risk assessment of selected red and green seaweeds validated by ICP-MS

The bioaccumulation of trace metals in 10 selected edible seaweeds was studied using inductively coupled plasma mass spectroscopy (ICP-MS). Bioaccumulation of higher levels of manganese (4.94 ± 0.15 μg/g) and aluminium (4.21 ± 0.18 μg/g) and lower levels of arsenic (0.18 ± 0.02 μg/g) and vanadium (0.09 ± 0.02 μg/g) were observed in Chlorophyta. In Rhodophyta, bioaccumulation of iron (8.51 ± 0.19 μg/g) was high, while lower levels of magnesium (0.13 ± 0.02 μg/g) and strontium (0.21 ± 0.01 μg/g) were observed among the seaweeds studied. Health assessment studies were also conducted on seaweeds to understand their effects on human consumption. The findings imply that consuming macroalgae has no health risk due to these elements in the general population. Furthermore, the confirmative toxicity of specific metals, such as Cd, Pb, and Zn metals in macroalgae, should be monitored constantly.

Particelle nanostrutturate di idrossiapatite biomimetica come sistema di delivery di micro e macro elementi nelle colture biologiche

Nanoparticelle biomimetiche di idrossiapatite drogate con ioni metallici (Cu, Fe, Mg, Zn, K) sono state utilizzate in formulazioni contenenti basse concentrazioni di rame (Cu) e zolfo (S) per controllare la peronospora (plasmopara viticola) e l'oidio (erysiphe necator) della vite. I formulati sono stati testati in campo sulla varietà di vino "Dolcetto" coltivata secondo tecniche di agricoltura biologica, e la loro efficacia è stata confrontata con prodotti commerciali contenenti miscela bordolese e zolfo.

I dati indicano che le formulazioni contenenti bassi dosaggi di rame e zolfo possono essere trasportati in modo efficiente dalle nanoparticelle di idrossiapatite biomimetica e possono ridurre la presenza di micota sulle foglie della vite. Nessun residuo di rame e zolfo è stato rilevato in campioni di vino ottenuti da viti in cui è stata utilizzata l'idrossiapatite biomimetica. Il drogaggio di nanoparticelle di idrossiapatite biomimetica con metalli di transizione è un modo efficiente per fornire micro e macro-elementi alle piante a basso livello di dosaggio. Le formulazioni contenenti idrossiapatite funzionano anche come supporti a lento rilascio di macronutrienti come elementi di calcio e fosforo.

Lead-induced modification of growth and yield of Linum usitatissimum L. and its soil remediation potential

This study was designed to evaluate the pre-reproductive and reproductive responses of Linum usitatissimum L. (flax, linseed plant) to different levels of Pb in the soil. Flax seeds were sown in garden soil-filled earthen pots and treated with three different levels of lead as lead chloride (150, 450, and 750 mg Pb kg^-1 soil) except control, and each treatment was replicated three times. Growth and reproductive parameters and photosynthetic pigments were significantly reduced (p ≤ 0.05) for all treatments. Quantitatively, Chlorophyll b content decreased more than chlorophyll a and the amount of proline content in the leaves increased in lockstep with the increase of Pb levels in the soil. Pb was found in substantial amounts in the roots, shoots, and seeds. The pattern of Pb accumulation in different organs was root > shoot > seeds. Pb levels in seeds obtained from 750 mg Pb kg^-1 soil-treated plants exceeded the permissible limits. Biological concentration factor (BCF), biological accumulation coefficient (BAC) and translocation factor (TF) values showed that roots of L. usitatissimum absorbed and accumulated a substantial quantity of Pb but translocated only a fraction of that to the shoots. Therefore, L. usitatissimum L. can be used in phytostabilization rather than phytoextraction of Pb.

Comparative zinc tolerance and phytoremediation potential of four biofuel plant species

Soil pollution has become a serious environmental problem worldwide due to rapid industrialization and urbanization. Zinc (Zn) contamination has raised concerns about potential effects on plants and human health. This study was conducted to assess the capability of four biofuel plants: Abelmoschus esculentus, Avena sativa, Guizotia abyssinica, and Glycine max to remediate and restore Zn contaminated soil. Selected plants were grown in soil exposed to different Zn treatments (50, 100, 200, 300, 400, 600, 800 and 1000 mg Zn kg^-1) for 12 weeks. Soil without spike taken as control. Zn induced toxicity significantly (p < 0.05) reduced seed germination and inhibited plant growth and leaf chlorophyll content. The investigated plants can tolerate a soil content of 800 mg Zn kg^-1 with the exception of A. sativa, which was most tolerant to high Zn concentrations (1000 mg Zn kg^-1) for all growth criteria. Moreover, increasing Zn content in soil resulted in a significant (p < 0.05) increase in Zn accumulation in various tissues of the four biofuel plants. According to phytoremediation efficiency, the four biofuel plants studied were arranged as follows: A. sativa (5.05%) > A. esculentus (4.15%) > G. max (2.31%) > G. abyssinica (1.17%). This study concluded that all tested biofuel plants species, especially A. sativa exhibited high Zn concentrations in roots and shoots, high Zn uptake capability, high tolerance, and high biomass at 50-800 mg Zn kg^-1 treatments. Consequently, these biofuel plants are excellent candidates for phytoremediation in Zn contaminated soils.

Environmental health and risk assessment metrics with special mention to biotransfer, bioaccumulation and biomagnification of environmental pollutants

The environment pollutants, which are landed up in environment because of human activities like urbanization, mining and industrializations, affects human health, plants and animals. The living organisms present in environment are constantly affected by the toxic pollutants through direct contact or bioaccumulation of chemicals from the environment. The toxic and hazardous pollutants are easily transferred to different environmental matrices like land, air and water bodies such as surface and ground waters. This comprehensive review deeply discusses the routes and causes of different environmental pollutants along with their toxicity, impact, occurrences and fate in the environment. Environment health and risk assessment tools that are used to evaluate the harmfulness, exposure of living organisms to pollutants and the amount of pollutant accumulated are explained with help of bio-kinetic models. Biotransfer, toxicity factor, biomagnification and bioaccumulation of different pollutants in the air, water and marine ecosystems are critically addressed. Thus, the presented survey would be collection of correlations those addresses the factors involved in assessing the environmental health and risk impacts of distinct environmental pollutants.

Seed Priming with ZnO and Fe3O4 Nanoparticles Alleviate the Lead Toxicity in Basella alba L. through Reduced Lead Uptake and Regulation of ROS

The increased lead (Pb) content in the environment has an impact on all living beings, including plant growth and quality. The present study aims to investigate the protective roles of zinc (Zn)- and iron (Fe)- nanoparticles (NPs) in alleviating stress symptoms caused by lead (Pb) exposure in Basella alba seedlings. For this purpose, 15 different treatment combinations of seed priming with two NPs at 0 and 200 mg L−1, and five Pb levels (0, 4, 8, 15, 20 mM) were chosen. Pb stress (20 mM) was found to reduce seed germination by 72.8% and seedling growth, particularly root length, by 92% when compared to the control. Under different Pb concentrations, seed priming with ZnNPs (200 mg L−1) and FeNPs (200 mg L−1) increased seed germination by 34.7% and 54.9%, respectively, and root length by 152.9% and 252.9%, respectively. In 20 mM Pb stress, NPs primed seedling showed decrease in Pb content by 33.7% with ZnNPs and 32.6% with FeNPs. Increased Pb stress resulted in increased reactive oxygen species (ROS) generation (H2O2) and lipid peroxidation (MDA) compared to non-Pb stressed seedlings. However, increased antioxidants in the NPs treatments such as SOD, CAT, POD and proline content, scavenged these ROS. Considering all the parameters under study, priming alleviated Pb stress in the following order: FeNPs > ZnNPs > hydropriming > control. To summarise, seed priming with Zn- and Fe-NPs has the potential to alleviate Pb toxicity via reduced Pb uptake, ROS generation and lipid peroxidation as well as increased proline content and activation of antioxidant enzymatic system.

A Comparative Analysis of Heavy Metal Effects on Medicinal Plants

Popularity of herbal drugs has always been in high demand, but recently it has been increasing all over the world, especially in India, because of the lower range of adverse health effects as compared to synthetic or man-made drugs. Not only this but their cost-effectiveness and easy availability to the poor people and the masses, particularly in developing countries, are major causes for their demand. But there lies a huge problem during the process of plant collection that affects their medicinal properties to certain degrees. This is caused by heavy metal toxicity in soil in different locations of the Indian subcontinent. This was correlated with their potential to cause health damage. Exposure of humans to heavy metals includes diverse pathways from food to water to consumption and inhalation of polluted air to permanent damage to exposed skin and even by occupational exposure at workplaces. As we can understand, the main mechanisms of heavy metal toxicity include the production of free radicals to affect the host by oxidative stress, damaging biological molecules such as enzymes, proteins, lipids, and even nucleic acids and finally damaging DNA which is the fastest way to carcinogenesis and in addition, neurotoxicity. Therefore, in this paper, we have researched how the plants/herbs are affected due to heavy metal deposition in their habitat and how it can lead to serious clinical complications.

Cadmium and lead differentially affect growth, physiology, and metal accumulation in guar (Cyamopsis tetragonoloba L.) genotypes

Phytoremediation is a strategy to employ plants to recover high quantities of metals in the soil into the harvestable parts such as shoots and roots. High levels of Cd and lead (Pb) in the soil cause several stress symptoms in plants including a decrease in growth, reduced root growth, and carbohydrate metabolism. In this study, Saravan and HGS-867 as local landrace and Indian guar variety were selected to investigate the effect of the application of Pb (0, 40, 150, and 200 mg/l) and the cadmium (0, 25, 50, and 100 mg/l) on phonological, yield parameters, and phytoremediation assessment. The results showed that Pb translocation factor (TF) was significant in Pb×Cd and Pb×Cd×G (genotype) at p<0.01 and in Pb×G at p<0.05. Pb bioconcentration factor (BCF) was significant (p<0.01) in all treatments except Cd and Cd×G treatments. Mean comparison of the data showed that the number of flowers, leaves, and clusters in plant decreased significantly with increasing Pb content. With increasing Cd concentration, the number of branches, height, the number of seeds, clusters, and leaves for each plant decreased significantly at the level of 1%. The maximum TF was observed in Pb at 40 mg/l in the HG-867 variety. Moreover, the Saravan landrace exposed to Cd (100 mg/l) showed the highest value of BCF (Cd). The gum percentage significantly decreased with increasing concentrations of Pb and Cd. Pearson's correlation analysis indicated that plant height, number of pods/plant, root length, biomass, and pod length had a positive correlation with seed yield and a negative correlation with TF (Pb) and BCF (Pb). The results suggest that according to TF, BCF, and BAC, C. tetragonoloba L. can be effectively used as a good accumulator of toxic metals in contaminated soils.

Effect of cadmium and ethylenediamine tetraacetic acid supplementation on cadmium accumulation by roots of Brassica species in Cd spiked soil

Cadmium (Cd) metal extraction through efficient plant roots has attracted much attention as this methodology is environment-friendly and cost-effective. Brassica species are well known for their tolerance towards high Cd concentration in contaminated soils. The tolerance ability may vary among species; hence the assessment of this variability is mandatory for selecting Brassica species. For this purpose, a greenhouse pot experiment was carried out using three Brassica species (Brassica juncea L., Brassica campestris L., and Brassica napus L.). To evaluate the effect of chelating agent ethylenediamine tetraacetic acid (EDTA) on Cd uptake, EDTA (0, 1, and 2 g kg^-1 soil) was supplemented along with Cd (0, 5, 10, 20, 40, and 80 mg kg^-1 soil). Among different species, B. juncea possessed the highest root dry biomass and lowest root Cd concentration in untreated soil. Overall root dry biomass of all tested Brassica species reduced on increasing Cd and EDTA levels. The trend was appeared to be related to an increase in root Cd concentration on the supplementation of EDTA that formed a complex with the target metal contaminate and resulted in vacuolar sequestration. Roots of B. juncea showed maximum Cd accumulation and highest values at Cd and EDTA levels up to 20 mg kg^-1 and 1 g kg^-1 soil due to the combined effect of root biomass and Cd concentration in roots. Thus, present findings inferred that Cd and EDTA supplementation might prove as a feasible strategy to improve remediation of Cd-polluted soil using B. juncea as an efficient Cd accumulator.

Metals in Calluna vulgaris, Empetrum nigrum, Festuca vivipara and Thymus praecox ssp. arcticus in the geothermal areas of Iceland

This investigation was conducted to identify the content of metals in Calluna vulgaris (family Ericaceae), Empetrum nigrum (family Ericaceae), Festuca vivipara (family Poaceae) and Thymus praecox subsp. arcticus (family Lamiaceae), as well as in the soils where they were growing in eight geothermal heathlands in Iceland. Investigation into the vegetation of geothermal areas is crucial and may contribute to their proper protection in the future and bring more understanding under what conditions the plants respond to an ecologically more extreme situation. Plants from geothermally active sites were enriched with metals as compared to the same species from non-geothermal control sites (at an average from about 150 m from geothermal activity). The enriched metals consisted of Cd, Co, Cu, Fe and Ni in C. vulgaris; Cd, Mn and Ti in E. nigrum; Hg and Pb in F. vivipara; and Cd, Fe and Hg in T. praecox. Notably, C. vulgaris, E. nigrum, F. vivipara and T. praecox had remarkably high concentrations of Ti at levels typical of toxicity thresholds. Cd and Pb (except for C. vulgaris and F. vivipara) were not accumulated in the shoots of geothermal plants. C. vulgaris from geothermal and control sites was characterised by the highest bioaccumulation factor (BF) of Ti and Mn; E. nigrum and F. vivipara by the highest BF of Ti and Cr; and T. praecox by the highest BF of Ti and Zn compared to the other elements. In comparison with the other examined species, F. vivipara from geothermal sites had the highest concentration of Ti in above-ground parts at any concentration of plant-available Ti in soil.

Effects of exogenous sulfur on maize (Zea mays L.) growth and Cd accumulation in Cd-contaminated plastic shed soil

Cadmium (Cd) pollution in plastic shed soils has become increasingly severe, posing a great threat to human health and social stability. Phytoremediation of cadmium pollution is an environmentally friendly and inexpensive remediation method. In this study, maize (Zea mays L.) was selected as the phytoremediation crop by a potted method, and the bioavailability of cadmium was investigated by adding exogenous elemental sulfur. The relationships among the sulfur content, maize growth, cadmium accumulation, and soil parameters were systematically studied. The results showed that, with the supplement of sulfur, the soil pH and activities of soil enzymes (urease, catalase, and sucrase) decreased gradually, and the available heavy metals (Cd, Cr, Zn, and Cu) in soil showed an upward trend. The optimal cadmium enrichment was achieved under T2 by increasing both the biomass of the maize plant and the cadmium concentration in roots and stems. However, T3 and T4 significantly inhibited the growth of maize roots and shoots, leading to a much lower plant biomass compared with that of CK (sulfur-free treatment) and T2. In addition, the cumulative cadmium was not increased because of the low accumulation of cadmium in some parts of the plant. Correlation analyses showed that the sulfur content was negatively correlated with soil pH and maize biomass (P < 0.01), and the cadmium content of whole maize was positively correlated with the dry weight of maize (P < 0.05) and the cadmium content in roots and stems (P < 0.01). In summary, to optimize cadmium phytoremediation of the plastic shed soil, an appropriate concentration of sulfur should be selected in practical applications to ensure that the biomass of the maize is maximized, and the cadmium concentration in different parts of the maize is increased or stabilized.

Glycinebetaine alleviates the chromium toxicity in Brassica oleracea L. by suppressing oxidative stress and modulating the plant morphology and photosynthetic attributes

Anthropogenic activities are a major source for contaminating the agricultural soil with heavy metals, which can affect physiological and metabolic processes in plants. Among the heavy metals, chromium (Cr) is the most toxic pollutant that negatively affects plants' metabolic activities, growth, and yield. Chromium reduces the plant growth and development by influencing the photosynthetic performance and antioxidant enzyme activities. This study was designed to examine the promotive role of exogenously applied glycinebetaine (GB) on plant morphophysiological and biochemical attributes in cauliflower (Brassica oleracea botrytis L.) under Cr toxicity. Four levels (0, 10, 100, and 200 μM) of Cr were tested under the application of GB (1 mM). The results delineated that Cr stress caused a considerable reduction in plant growth, photosynthetic pigment, gas exchange parameters, and biomass production. At high concentration (200 μM), chromium stress decreased the plant height (57%), root length (32%), number of leaves (45%), and leaf area (29%) as compared with controls. Due to Cr stress, the electrolyte leakage and accumulation of malondialdehyde and hydrogen peroxide increased both in the roots and leaves of cauliflower, whereas antioxidative enzyme activities (SOD, CAT, and POD) decreased both in the roots and leaves of cauliflower due to Cr stress. At 200 μM of chromium treatment, root dry weight, stem dry weight, leaf dry weight, and flower dry weight declined up to 43%, 40%, 53%, and 72%, respectively. With the application of GB, dry biomass of plant increased significantly as compared with no GB treatment under chromium stress. As Cr level increased in growth media, its concentration also increased in all plant parts including roots, stem, leaves, and flowers. However, GB application efficiently alleviated the Cr toxic effects on cauliflower and maintained higher plant growth, biomass production, photosynthetic attributes, and gas exchange traits as compared with their respective controls. Exogenously applied GB decreased oxidative stress and improved antioxidative enzyme activities as compared with treatments without GB application. Furthermore, Cr concentrations taken by plants were decreased due to GB application. These findings suggest that GB can play a positive role to maintain plant morphology and photosynthetic attributes under Cr toxic conditions in cauliflower.

Phytoremediation: Environmentally sustainable way for reclamation of heavy metal polluted soils

Soil contamination with toxic metals is a widespread environmental issue resulting from global industrialization within the past few years. Therefore, decontamination of heavy metal contaminated soils is very important to reduce the associated risks and for maintenance of environmental health and ecological restoration. Conventional techniques for reclamation of such soils are expensive and environmental non-friendly. Phytoremediation is an emerging technology implementing green plants to clean up the environment from contaminants and has been considered as a cost-effective and non-invasive alternative to the conventional remediation approaches. There are different types of phytoremediation including, phytostabilization, phytostimulation, phytotransformation, phytofiltration and phytoextraction, the latter being most extensively acknowledged for remediation of soils contaminated with toxic heavy metals. Recent literature is gathered to critically review the sources, hazardous effects of toxic heavy metals and environmentally sustainable phytoremediation technique for heavy metal polluted soils to offer widespread applicability of this green technology. Different strategies to enhance the bioavailability of heavy metals in the soil are also discussed shortly. It can be concluded that phytoremediation of heavy metal contaminated soils is a reliable tool and necessary for making the land resource accessible for crop production.

Evaluation of chromium phyto-toxicity, phyto-tolerance, and phyto-accumulation using biofuel plants for effective phytoremediation

Contamination of chromium signifies one of the major threats to soil system. Phytoremediation is a promising technique to reclaim metal-contaminated soil using plants which are capable to tolerate and accumulate heavy metals within in their tissues. The experiment reported in this article was carried out with six biofuel plant species, Cyamopsis tetragonoloba, Glycine max, Avena sativa, Abelmoschus esculentus, Sesamum indicum and Guizotia abyssinica, were subjected to eight Cr concentrations (0.5, 2.5, 5, 10, 25, 50, 75 and 100 mg kg^-1 soil) to investigate Cr toxicity, tolerance and accumulation. After 12 weeks of experiment, Cr phytotoxicity on morphological and biochemical parameters were evaluated. For six plant species, seed germination and most of growth parameters were significantly (p < 0.05) reduced under high Cr stress. Chlorophyll contents were also decreased with increased Cr concentrations. Accumulation of Cr was higher in roots than shoot in all studied plants. Significant Cr accumulation was in the order of C. tetragonoloba > A. sativa > A. esculentus > S. indicum > G. max > G. abyssinica. Bioconcentration factor, bioaccumulation coefficient, translocation factor and phytoremdiation ratio suggested that C. tetragonoloba, A. sativa and A. esculentus being more tolerant; having higher Cr accumulation and could be a high efficient plants for reclamation of Cr-contaminated soils.

Effect of distillery spentwash fertigation on crop growth, yield, and accumulation of potentially toxic elements in rice

The safe disposal of industrial effluents always remained a challenging process because of their high level of nutrients, toxic elements, and salts. A pot experiment was conducted to investigate the effects of various concentrations (5%, 10%, 15%, and 20%) of sugar industry effluent spentwash (SW) fertigated with tab water (TW), on soil properties, crop growth, physiological parameters, yield components, and accumulation of potentially toxic elements (PTEs) in rice (Oryza sativa L.) grains and straw. The results showed that soil physico-chemical properties were modified with rise in SW concentration. Application of 5% SW significantly enhanced the plant growth, and yield components. Photosynthesis rate, transpiration rate, and stomatal conductance were significantly higher under 5% SW concentration in comparison with control. However, SW concentrations of > 5% showed inhibitory effects for all growth, physiological, and yield components. Accumulation of PTEs showed increasing trend with rise in SW concentration. However, under 5% SW concentration, all the PTEs in rice grain and straw were within the permissible limits (PLs) recommended by FAO/WHO and no health hazards were detected by health risk assessment. Based on the study results, 5% SW fertigation with TW can be applied as fertilizer for enhancing the growth and productivity of rice. Graphical abstract.

Heavy metal accumulation imparts structural differences in fragrant Rosa species irrigated with marginal quality water

Wastewater is an alternative to traditional sources of renewable irrigation water in agriculture, particularly in water-scarce regions. However, the possible risks due to heavy metals accumulation in plant tissues are often overlooked by producers. The present study aimed to identify heavy metals-induced structural modifications to roots of scented Rosa species that were irrigated with water of marginal quality. The chemical and mineral contents from the experimental irrigation canal water (control) and treated wastewater were below the limits recommended by the Pakistan Environmental Protection Agency (Pak-EPA) for medicinal plants. The experimentally untreated wastewater contained electrical conductivity (EC), chemical oxygen demand (COD), biological oxygen demand (BOD), and heavy metals (Co, Cu, Cd, Pb) that were above the recommended limits. The responses by wastewater-treated Rosa species (Rosa damascena, R. bourboniana, R. Gruss-an-Teplitz, and R. centifolia) were evaluated. The experimental data revealed that treated wastewater significantly increased the thickness of collenchyma (cortex and pith) and parenchyma tissues (vascular bundle, xylem, and phloem) of R. Gruss-an-Teplitz. Root dermal tissues (epidermis) of R. bourboniana also responded to treated wastewater. R. damascena and R. centifolia were the least affected species, under the experimental irrigation conditions. Collenchyma and dermal tissues were thicker in R. damascena and R. Gruss-an-Teplitz under untreated wastewater conditions. In parenchyma tissues, vascular bundles were thicker in R. damascena in untreated wastewater conditions, while the xylem and phloem of R. Gruss-an-Teplitz were thicker where treated wastewater was applied. In tissues other than the vascular bundle, the differences in anatomical metrics due to the experimental irrigation treatments were greater during the second year of the experiment than in the first year. The contents of metals other than chromium in the roots and stems of roses were below the WHO limits, under all of the experimental irrigation conditions. Rosa centifolia contained higher heavy metals content than the other experimental species, and heavy metals content was associated with anatomical changes due to the treatments. We conclude that, under conditions of wastewater irrigation, R. Gruss-an-Teplitz was highly resistant; R. damascena was moderately resistant while R. bourboniana and R. centifolia were the most susceptible to irrigation with marginal quality water. This is the first report of plant tissue responses to wastewater irrigation by the experimental species. Regarding the accumulation of heavy metals in rose plant tissues, the results confirm that untreated wastewater must be treated to grow Rosa species where water is scarce.

Morpho-Physiological and Proteome Level Responses to Cadmium Stress in Sorghum

Cadmium (Cd) stress may cause serious morphological and physiological abnormalities in addition to altering the proteome in plants. The present study was performed to explore Cd-induced morpho-physiological alterations and their potential associated mechanisms in Sorghum bicolor leaves at the protein level. Ten-day-old sorghum seedlings were exposed to different concentrations (0, 100, and 150 μM) of CdCl2, and different morpho-physiological responses were recorded. The effects of Cd exposure on protein expression patterns in S. bicolor were investigated using two-dimensional gel electrophoresis (2-DE) in samples derived from the leaves of both control and Cd-treated seedlings. The observed morphological changes revealed that the plants treated with Cd displayed dramatically altered shoot lengths, fresh weights and relative water content. In addition, the concentration of Cd was markedly increased by treatment with Cd, and the amount of Cd taken up by the shoots was significantly and directly correlated with the applied concentration of Cd. Using the 2-DE method, a total of 33 differentially expressed protein spots were analyzed using MALDI-TOF/TOF MS. Of these, treatment with Cd resulted in significant increases in 15 proteins and decreases in 18 proteins. Major changes were absorbed in the levels of proteins known to be involved in carbohydrate metabolism, transcriptional regulation, translation and stress responses. Proteomic results revealed that Cd stress had an inhibitory effect on carbon fixation, ATP production and the regulation of protein synthesis. Our study provides insights into the integrated molecular mechanisms involved in responses to Cd and the effects of Cd on the growth and physiological characteristics of sorghum seedlings. We have aimed to provide a reference describing the mechanisms involved in heavy metal damage to plants.

Variation in copper and zinc tolerance and accumulation in 12 willow clones: implications for phytoextraction

Willows (Salix spp.) have shown high potential for the phytoextraction of heavy metals. This study compares variations in copper (Cu) and zinc (Zn) tolerance and accumulation potential among 12 willow clones grown in a nutrient solution treated with 50 μmol/L of Cu or Zn, respectively. The results showed differences in the tolerance and accumulation of Cu and Zn with respect to different species/clones. The biomass variation among clones in response to Cu or Zn exposure ranged from the stimulation of growth to inhibition, and all of the clones tested showed higher tolerance to Cu than to Zn. The clones exhibited less variation in Cu accumulation but larger variation in Zn accumulation. Based on translocation factors, it was found that most of the Cu was retained in the roots and that Zn was more mobile than Cu for all clones. It is concluded that most willow clones are good accumulators of Zn and Cu.

Toxic element profiles in selected medicinal plants growing on serpentines in Bulgaria

Populations of medicinal plants growing on serpentines and their respective soils were analyzed for Fe, Ni, Mn, Cr, Co, Cd, Cu, Zn, and Pb using inductively coupled plasma atomic emission spectrometry. Aqua regia extraction and 0.43 M acetic acid extraction were used for the quantification of pseudototal and bioavailable fractions, respectively, of elements in soil and nitric acid digestion for determination of total element content in plants. Screening was performed to (1) document levels of toxic metals in herbs extensively used in preparation of products and standardized extracts, (2) compare accumulation abilities of ferns and seed plants, and (3) estimate correlations between metal content in plants and their soils. The toxic element content of plants varied from site to site on a large scale. The concentrations of Fe and Ni were elevated while those of Cu, Zn, and Pb were close to average values usually found in plants. The highest concentrations for almost all elements were measured in both Teucrium species. Specific differences in metal accumulation between ferns and seed plants were not recorded. The investigated species are not hyperaccumulators but can accumulate toxic elements, in some cases exceeding permissible levels proposed by the World Health Organization and European Pharmacopoeia. The harvesting of medicinal plants from serpentines could be hazardous to humans.

The effects of excess copper on antioxidative enzymes, lipid peroxidation, proline, chlorophyll, and concentration of Mn, Fe, and Cu in Astragalus neo-mobayenii

To probe the physiological and biochemical tolerance mechanisms in Astragalus neo-mobayenii Maassoumi, an endemic plant around the Cu-rich areas from the North West of Iran, the effect of different copper concentrations at toxic levels on this plant was investigated. Copper was applied in the form of copper sulfate (CuSO₄·5H₂O) in four levels (0, 50, 100, and 150 μM). We observed no visible symptoms of Cu toxicity in this plant species. During the exposure of plants to excess copper, the antioxidant defense system helped the plant to protect itself from the damage. With increasing copper concentration, superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities increased in leaves and roots (P < 0.001) compared with that of the control group. The chlorophyll amount gradually declined with increasing Cu concentrations. However, reduction in the 50 μM level showed insignificant changes. Enhanced accumulation of proline content in the leaves was determined, as well as an increase of MDA content (oxidative damage biomarker) (P < 0.001). The results indicated that Cu contents in leaves and roots enhanced with increasing levels of Cu application. The Fe and Mn contents in both shoots and roots significantly decreased with increasing Cu concentration. Finally, the mechanisms of copper toxicity and copper tolerance in this plant were briefly discussed.

Growth, tolerance efficiency and phytoremediation potential of Ricinus communis (L.) and Brassica juncea (L.) in salinity and drought affected cadmium contaminated soil

We have previously reported that Ricinus communis (castor) is more tolerant to soil cadmium (Cd) and more efficient for Cd phytoremediation than Brassica juncea (Indian mustard) (Bauddh and Singh, 2012). In the present study, R. communis was found more tolerant to salinity and drought in presence of Cd and removed more Cd in a given time than Indian mustard. R. communis produced 23 and twelve folds higher biomass in terms of fresh weight and dry weight, respectively than that in B. juncea during three months when grown in Cd contaminated soil in presence of 100mM NaCl salinity and ten day water withdrawal based drought at 90 day after sowing (DAS). Castor plants showed stronger self-protection ability in form of proline bioaccumulation (r(2)=0.949) than Indian mustard (r(2)=0.932), whereas a lower r(2) for malondialdehyde (MDA) and total soluble protein in R. communis (r(2)=0.914 and r(2)=0.915, respectively) than that of B. juncea (r(2)=0.947 and r(2)=0.927, respectively) indicated a greater damage to cell membrane in Indian mustard during the multiple stress conditions. Though, the amount of Cd accumulated in the roots and shoots of Indian mustard was higher as per unit biomass than that in castor, total removal of the metal from soil was much higher in castor on per plant basis in the same period in presence of the stresses. R. communis accumulated about seventeen and 1.5 fold higher Cd in their roots and shoots, respectively than that of B. juncea in 90 DAS under the multiple stresses. Salinity alone enhanced Cd uptake, whereas drought stress reduced its uptake in both the plants.

Testing hypotheses on the resistance to metals by Daphnia longispina: differential acclimation, endpoints association, and fitness costs

Pollution by metals may lead to an increased tolerance in the exposed population through adaptive microevolution, with resistant genotypes becoming more abundant than in reference sites. This work investigated the outcomes associated with selection for resistance by testing three hypotheses to assess the following: Do resistant versus sensitive clonal lineages of Daphnia longispina differentially acclimate to metals during a long-term sublethal exposure, is there a significant correlation between lethal and sublethal responses, and does resistance to metals entail costs to fitness under uncontaminated conditions? No evidence of acclimation was observed. The median effective dilutions of acid mine drainage for reproduction were similar for successive broods within clones during long-term exposures. Lethal and sublethal responses were not correlated, indicating that mechanisms regulating the two types of response were more than likely different. Finally, fitness costs associated with the resistance to lethal levels of metals were not detected, but resistance to sublethal levels of Cu was found to be correlated with a lower intrinsic growth rate under control conditions.

Cadmium accumulation and tolerance of two safflower cultivars in relation to photosynthesis and antioxidative enzymes

To investigate the effects of cadmium (Cd) on photosynthetic and antioxidant activities of safflower (Carthamus tinctorius L.) plants, two cultivars (Yuming and New safflower No. 4) were used for long-term pot experiment, under 0, 25, 50 or 100 mg Cd kg(-1) (DW) soil conditions. The results showed that there is a large amount of Cd (148.6-277.2 mg kg(-1)) accumulated in the shoot of safflower, indicating this species might be a potential Cd accumulator. Exposure to 25-100 mg Cd kg(-1) soil decreased the net photosynthetic rate by 25.6%-48.9% for New safflower No. 4, and 16.7%-57.3% for Yuming, respectively. The inhibition of photosynthesis might result from the limitation of stomatal conductance, reduction in photosynthetic pigment, and destruction of photosynthetic apparatus caused by Cd stress. Cd caused an enhancement of malondialdehyde (MDA), an increase in activity of superoxide dismutase (SOD) and ascorbate peroxidase (APX), and a decrease in catalase (CAT) activity for both cultivars. It seems that SOD and APX accounted for the scavenging of oxidant stress in safflower cultivars. The physiological response of safflower plants to Cd stress was cultivar- and dose-dependent. New safflower No. 4 exhibited high photosynthetic performance at high Cd stress, which may be contributed by high intercellular CO(2) concentration, APX activity and Car/Chl ratio. In contrast, Yuming is more tolerant to Cd toxicity at low Cd level, in which an efficient antioxidant system is involved.

Nickel and phosphorous sorption efficiencies, tissue accumulation kinetics and morphological effects on Eichhornia crassipes

The aim of the research was to assess the uptake efficiencies of Ni and P, their distribution in tissues along time and their toxic effects on the internal and external morphologies of Eichhornia crassipes. Aquaria with plants exposed to 1 mg Ni l(-1) or 5 mg P l(-1) and control were arranged in triplicate. Water and plants (aerial parts and roots) were sampled along 30 days. Ni uptake and tissue bioaccumulation kinetics was significantly faster than that of P. Mean root length, number of leaves, biomass and chlorophyll concentration were negatively affected by Ni, while these parameters were significantly increased by P in comparison with the control. Stele and metaxylem vessel cross-sectional areas (CSA) in the P treatment were significantly lower in comparison with that obtained in the Ni treatment and in control. Metaxylem vessels CSA in plants exposed to Ni were significantly higher while the number of vessels was significantly lower than those obtained in the control. Despite the toxic effects, E. crassipes efficiently accumulated Ni, probably due to the morphological plasticity of its root system.

Cadmium tolerance and accumulation in eight potential energy crops

The production of energy crops that can be used for biodiesel production is a sustainable approach for the removal of metal pollutants by phytoremediation. This study investigated the cadmium (Cd) accumulation and tolerance of eight potential energy crops. After growth for 28 days in substrates containing 0, 50, 100 or 200 mg Cd x kg(-1), seedlings were evaluated for growth parameters, chlorophyll content, chlorophyll fluorescence parameters and Cd accumulation. All eight crops were moderately tolerant to Cd toxicity, with four [i.e., hemp (Cannabis sativa), flax (Linum usitatissimum), castor (Ricinus communis) and peanut (Arachis hypogaea)] being more tolerant than the others. Three of these crops (hemp, flax and peanut) had higher Cd accumulation capacities. The roots of peanut and hemp had high bioconcentration factors (BCF>1000), while flax shoots accumulated a higher concentration of Cd (>100 mg/kg). These results demonstrate that it is possible to grow energy crops on Cd-contaminated soil. Hemp, flax and peanut are excellent candidates for phytoremediation.

Chemical fractionation and translocation of heavy metals in Canna indica L. grown on industrial waste amended soil

A pot experiment was carried out to assess the effect of different amendments of industrial sludge on the growth of Canna indica L. as well as the translocation potential of heavy metals of this plant. The accumulation of metals (Cr, Fe, Cd, Cu, Ni, Zn, Mn and Pb) in different parts of C. indica L. grown on industrial sludge-amended soil increased with time and increasing doses of sludge amendments. Sequential extraction method was followed to estimate the different fractions of heavy metals in sludge-amended soils collected from different periods of this study. The results showed that Mn, Zn, Cd, Cr and Pb were mostly associated with Fe-Mn oxide fraction in all amendments, whereas, Ni was mostly found in residual (RES) fraction. Cu and Fe were found to be higher in organically bounded form (OM) and RES fraction. The metal concentration in C. indica L. after 90 days of experiment started, was in the order of Fe>Cr>Mn>Zn>Ni>Cu>Cd>Pb and the metal translocation was found lesser in shoot. With the increasing percentage of sludge amendments in soil the metal concentrations increased in different parts of plants. Overall, the plant C. indica L. was found to be well adapted in industrial sludge amendments and it may be recommended that this plant was found suitable for phytoremediation of most of the studied metals.

Slow growth of Empetrum nigrum in industrial barrens: combined effect of pollution and age of extant plants

We studied the impact of industrial pollution on population demography (age structure), growth and reproduction of crowberry, Empetrum nigrum L. Crowberry growing in severely polluted sites near non-ferrous smelters (at Harjavalta, Monchegorsk and Nikel) was on average twice as old as in unpolluted habitats, as indicated by the number of annual rings at root collar. Shoot length decreased both with plant ageing and due to pollution impact, while neither the proportion of generative plants nor berry production was affected by pollution or plant age. Our results suggest that death of the extant individuals of E. nigrum near the non-ferrous smelters is to a large extent explained by age-related damage of the main stem accelerated by pollution. Since vegetative propagation, seed germination and seedling establishment are hampered by soil toxicity, E. nigrum populations near the smelters continue to decline with ageing in spite of the gradual decline of emissions.

Remediation of heavy metal-contaminated forest soil using recycled organic matter and native woody plants

The main aim of this study was to determine how the application of a mulch cover (a mixture of household biocompost and woodchips) onto heavy metal-polluted forest soil affects (i) long-term survival and growth of planted dwarf shrubs and tree seedlings and (ii) natural revegetation. Native woody plants (Pinus sylvestris, Betula pubescens, Empetrum nigrum, and Arctostaphylos uva-ursi) were planted in mulch pockets on mulch-covered and uncovered plots in summer 1996 in a highly polluted Scots pine stand in southwest Finland. Spreading a mulch layer on the soil surface was essential for the recolonization of natural vegetation and increased dwarf shrub survival, partly through protection against drought. Despite initial mortality, transplant establishment was relatively successful during the following 10 yr. Tree species had higher survival rates, but the dwarf shrubs covered a larger area of the soil surface during the experiment. Especially E. nigrum and P. sylvestris proved to be suitable for revegetating heavy metal-polluted and degraded forests. Natural recolonization of pioneer species (e.g., Epilobium angustifolium, Taraxacum coll., and grasses) and tree seedlings (P. sylvestris, Betula sp., and Salix sp.) was strongly enhanced on the mulched plots, whereas there was no natural vegetation on the untreated plots. These results indicate that a heavy metal-polluted site can be ecologically remediated without having to remove the soil. Household compost and woodchips are low-cost mulching materials that are suitable for restoring heavy metal-polluted soil.

Copper bioavailability in the rhizosphere of maize (Zea mays L.) grown in two Italian soils

In this study, potentially bioavailable copper was estimated in two soils (a fungicide polluted and a natural soil) using a passive sampling technique, DGT. As plants can alter copper mobility and bioavailability in the soil, the rhizosphere properties of Zea mays L. were investigated using rhizoboxes. Compared to the total concentration, the soluble and the potentially bioavailable copper concentration in the bulk soils were generally low (less than 0.20% and 0.06% respectively), with a sixfold increase in the rhizosphere of the polluted soil. Our results suggest that maize cultivation in a polluted vineyard soil could increase the potentially available fraction of copper. DGTs showed a good sensitivity to soil properties and to root-induced changes in the rhizosphere, but the potentially bioavailable copper could not be related to the copper concentration in the above ground parts of maize. The results suggest that DGT may be used to predict some effects of the cultivation of polluted soils, for example, metal mobility and increased availability, but they cannot mimic the uptake of a tolerant plant. For both soils, dissolved organic carbon (DOC) concentrations were threefold higher in the rhizosphere than in the bulk soil, whilst bioaccumulation in leaves and roots was not significant. DOC production, usually effective in ion mobilization and assimilation, may help also in the reduction of Cu uptake at toxic concentrations. The sequestration of available Cu in soil and soil solution by DOC seems to contribute to maize tolerance.

Chemical fractionation and heavy metal accumulation in the plant of Sesamum indicum (L.) var. T55 grown on soil amended with tannery sludge: Selection of single extractants

A pot experiment was carried out to study the single and sequential extractions of metals in different tannery sludge amendment and the potential of the plant of Sesamum indicum L. var. T55 (sesame) for the removal of metals from tannery waste contaminated site. The metal extraction efficiency obtained with each extractants was slightly different and follow the order; EDTA>DTPA>NH(4)NO(3)>NaNO(3)>CaCl(2). The correlation analysis between extractable metals in the different amendments of sludge and metal accumulation in the plant (lower and upper parts) showed better correlation for most of the tested metals with EDTA extraction. In this study, a sequential extraction technique was applied on different amendments of tannery sludge. The results showed that Mn, Zn, Cr and Cd were mostly associated with Fe-Mn oxide fraction in most of the amendments, K and Ni was found in residual (RES) fraction, Fe and Cu was bound with organic matter (OM) and RES fractions and Na was associated with carbonate (CAR) fraction. The metal accumulation after 60 d of growth of the plant was found in the order of K>Na>Fe>Zn>Cr>Mn>Cu>Pb>Ni>Cd and its translocation was found less in upper part. The accumulation of toxic metals (Cr, Ni and Cd) in the plants was found to increase with increase in sludge ratio, in contrast, the accumulation of Pb decreased. In view of growth parameters and metal accumulation in the plant, it was observed that lower amendments (25%) of tannery sludge were found suitable for the phytoremediation of most of the studied metals.

Resistance to metal contamination by historically-stressed populations of Ceriodaphnia pulchella: environmental influence versus genetic determination

Field populations of daphnids historically-stressed by metal contamination may show increased resistance to those contaminants. This study was undertaken aiming to confirm/infirm three main hypotheses: (1) field populations living in historically-impacted environments are more tolerant to metal stress than populations from reference sites; (2) resistance differences are genetically-determined, i.e., differences persist after controlling for environmental and maternal effects, by acclimating cloned lineages to similar conditions; and (3) resistance to stress in field populations living in historically-impacted environments is due to the disappearance of sensitive individuals rather than the appearance of highly resistant ones, i.e., the shift in the central tendency of resistance is linked to a decrease in the range of population resistance and not to an increased upper limit of the population resistance. Three populations of the cladoceran Ceriodaphnia pulchella Sars in Southern Portugal were sampled; one of which has been historically-stressed by acid mine drainage (AMD) from an abandoned cupric-pyrite mine and two from reference sites within the same watershed. To assess if resistance differences were genetically-determined, the three populations were acclimated for at least five generations under the same controlled conditions. Assays with AMD contaminated water samples were performed with both non-acclimated and acclimated individuals from all studied populations. Reproduction results in sub-lethal assays revealed significant differences between the reference and stressed populations. Significant differences in resistance to lethal levels of toxicity were observed for both non-acclimated and acclimated populations, individuals from population I being more resistant than those from reference populations. The existence of genetically-determined sensitivity differences was attested by the presence of significant differences in resistance to lethal levels of toxicity in acclimated individuals from reference and stressed populations. Results from cumulative mortality assays revealed that sensitive individuals were most probably present in the original population, but no conclusion could be draw about the presence of extreme resistant individuals in the historically-stressed population. Finally, it was shown that responses among populations converged from high to low levels of contamination.

Nickelophilous plants and their significance in phytotechnologies

Nickeliferous soils are invaded predominantly by members of the Brassicaceae, Cyperaceae, Cunoniaceae, Caryophyllaceae, Fabaceae, Flacourtiaceae, Euphorbiaceous, Lamiaceae, Poaceae and Violaceae, and many of these plants are metal tolerant. About 300 Ni hyperaccumulating plants been identified. These members exhibit unusual appetite for toxic metals and elemental defense. Hyperaccumulators provide protection against fungal and insect attack. Investigations suggested that Ni-hyperaccumulation has a protective function against fungal and bacterial pathogens in Streptanthus polygaloides and Thlaspi montanum. Significance of nickelophilous plants and their significance in phytotechnologies are discussed in this paper.

Copper resistance of the evergreen dwarf shrub Arctostaphylos uva-ursi: an experimental exposure

The copper (Cu) resistance of Arctostaphylos uva-ursi was tested in a pot experiment (lasting 8 weeks) using rooted cuttings originating from an area near the Harjavalta Cu-Ni smelter, SW Finland. The fine roots were moderately infected by arbutoid mycorrhizae. The plants were exposed to five Cu levels (1, 10, 22, 46 and 100 mg l(-1)) given repeatedly together with a nutrient solution. The critical Cu concentration in the nutrient solution inhibiting the growth of A. uva-ursi was below 10 mg l(-1) Cu (EC(50) value for biomass production 3.3 mg l(-1) Cu). This concentration was clearly lower than the value we have found earlier for other dwarf shrubs under similar experimental conditions. Most of the Cu given accumulated in the roots and old stems. The results suggest that A. uva-ursi cuttings were relatively sensitive to Cu despite the ability of the adult clones to grow in Cu-contaminated soil. The adult clones extend their roots into the less toxic deeper soil layers, which may facilitate the avoidance of heavy metals.

Ultrastructural element localization by EDXS in Empetrum nigrum

Empetrum nigrum L. is one of the few species growing on highly polluted areas in the northern boreal forests and it accumulates considerable amounts of heavy metals especially in its older stems. Previous-year stems of Empetrum nigrum were collected from two different sites located at distances of 0.5km (highly contaminated) and 8km (low contaminated) from a Cu--Ni smelter at Harjavalta, SW Finland. The element (Al, As, Cu, Fe, Mn, Zn, Ca, K, P, S, Mg, Na) localization was performed by energy-dispersive X-ray spectroscopy (EDXS) after cryofixation, freeze-drying and pressure infiltration of the material. The results showed higher levels of Cu, As and Fe in cell compartments of E. nigrum close to the smelter than at further distance. The Al and Zn levels, in contrast, showed no clear differences between the sites. Cu was distributed homogeneously in the tissue and occurred in vacuoles, cytoplasm, cell walls as well as in lumens of the vascular tissue. The higher amounts of As were localized in the outer regions of the stem cross-section and the amounts were higher in the primary cell walls of living (ray cells, phloem) than dead cells (xylem, sclereids). Ray cells, phloem and sclereids had elevated Fe amounts compared to the other tissues in the contaminated stem samples but owing to the high variation between the replicates, no significant differences were found. Based on the rather homogeneous localization of Cu, As and Fe in the living tissue and increased levels of Cu, As and Fe in vacuoles, cell walls and cytoplasm near the smelter, it seems that more than one specific mechanism contribute to the heavy metal tolerance of E. nigrum. Macronutrients did not show clear differences between the two distances or connection to heavy metal localization. Neither the role of complexing agents in heavy metal tolerance in the cytoplasm or vacuoles could be shown by this study. Because of the more frequent localization of electron dense phenolic material in the polluted samples, it might also have a function in the heavy metal tolerance of E. nigrum.

Effect of mixed cadmium, copper, nickel and zinc at different pHs upon alfalfa growth and heavy metal uptake

Alfalfa plants were grown in soil-pots contaminated with a mixture of Cd(II), Cu(II), Ni(II), and Zn(II), (at 50 mg/kg each) at pHs of 4.5, 5.8, and 7.1. The plants were fertilized using a nutrient solution, which was adjusted appropriately to the same pH. Plants in the control treatment were grown in the absence of the heavy metals mixture. The growth of the control plants was the same at the three pHs studied and the heavy metal stressed plants also showed similar behavior at each pHs. There were statistically significant differences (P<0.05) between the shoot length of the control treatment plants and the length of plants grown in the presence of the heavy metal mixture. Under the effects of the heavy metal mixture, nickel was the most accumulated element in the shoot tissue, with 437, 333, and 308 ppm at pH 7.1, 5.8, and 4.5, respectively. Cadmium was found to be second in accumulated concentrations with 202 ppm, 124 ppm, and 132 ppm at pH 7.1, 5.8, and 4.5, respectively, while zinc was third, followed by copper. The maximum relative uptakes (element in plant/element in soil-water-solution) were found to be 26 times for nickel, 23 times for cadmium, 12 times for zinc. and 6 times for copper. We considered these relations as indicative of the ability of alfalfa plants to take up elements from a soil matrix contaminated with a mixture of cadmium, copper, nickel, and zinc.

Comparison of the element composition in several plant species and their substrate from a 1500000-km2 area in Northern Europe

Leaves of 9 different plant species (terrestrial moss represented by: Hylocomium splendens and Pleurozium schreberi; and 7 species of vascular plants: blueberry, Vaccinium myrtillus; cowberry, Vaccinium titis-idaea; crowberry, Empetrum nigrum; birch, Betula pubescens; willow, Salix spp.; pine, Pinus sylvestris and spruce, Picea abies) have been collected from up to 9 catchments (size 14-50 km2) spread over a 1500000 km2 area in Northern Europe. Soil samples were taken of the O-horizon and of the C-horizon at each plant sample site. All samples were analysed for 38 elements (Ag, Al, As, B, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Rb, S, Sb, Sc, Se, Si, Sn, Sr, Th, Tl, U, V, Y, Zn and Zr) by ICP-MS, ICP-AES or CV-AAS (for Hg-analysis) techniques. The concentrations of some elements vary significantly between different plants (e.g. Cd, V, Co, Pb, Ba and Y). Other elements show surprisingly similar levels in all plants (e.g. Rb, S, Cu, K, Ca, P and Mg). Each group of plants (moss, shrubs, deciduous and conifers) shows a common behaviour for some elements. Each plant accumulates or excludes some selected elements. Compared to the C-horizon, a number of elements (S, K, B, Ca, P and Mn) are clearly enriched in plants. Elements showing very low plant/C-horizon ratios (e.g. Zr, Th, U, Y, Fe, Li and Al) can be used as an indicator of minerogenic dust. The plant/O-horizon and O-horizon/C-horizon ratios show that some elements are accumulated in the O-horizon (e.g. Pb, Bi, As, Ag, Sb). Airborne organic material attached to the leaves can thus, result in high values of these elements without any pollution source.