Structural Changes of Cell Wall and Lignifying Enzymes Modulations in Bean Roots in Response to Copper Stress

Fourteen-day-old bean seedlings were cultured in nutrient solution containing Cu²⁺ ions at various concentrations (50 and 75 μM of CuSO₄) for 3 days. This excess of copper induced a reduction in the water volume absorbed by the plants. Moreover, this reduction was accompanied by an increase of the amount of copper taken up by the roots. Analysis by native gel electrophoresis of cell wall peroxidase activities in the roots revealed a stimulation of two anionic isoforms (A₂ and A₃) under cupric stress conditions. Moreover, the activity of phenylalanine ammonia lyase (EC. 4.3.1.5), which plays an important role in plant defense, was enhanced. Copper-treated bean roots showed modifications in the cell walls of various tissues. Label for lignin, callose, and suberin with berberine-aniline blue revealed abnormal cell wall thickenings in the endodermis, the phloem, and the xylem, especially in plants treated with 75 μM CuSO₄.     

Effects of copper on expression of methane monooxygenases,trichloroethylene degradation,and community structure in methanotrophic consortia

Copper plays a key role in regulating the expression of enzymes that promote biodegradation of contaminants in methanotrophic consortia (MC). Here, we utilized MC isolated from landfill cover to investigate cometabolic degradation of trichloroethylene (TCE) at nine different copper (Cu²⁺) concentrations. The results demonstrated that an increase in Cu²⁺ concentration from 0 to 15 μM altered the specific first‐order rate constant k_1,TCE, the expression levels of methane monooxygenase (pmoA and mmoX) genes, and the specific activity of soluble methane monooxygenase (sMMO). High efficiency TCE degradation (95%) and the expression levels of methane monooxygenase (MMO) were detected at a Cu²⁺ concentration of 0.03 μM. Notably, sMMO‐specific activity ranged from 74.41 nmol/(mg_cell h) in 15 μM Cu²⁺ to 654.99 nmol/(mg_cell h) in 0.03 μM Cu²⁺, which contrasts with cultures of pure methanotrophs in which sMMO activity is depressed at high Cu²⁺ concentrations, indicating a special regulatory role for Cu²⁺ in MC. The results of MiSeq pyrosequencing indicated that higher Cu²⁺ concentrations stimulated the growth of methanotrophic microorganisms in MC. These findings have important implications for the elucidation of copper‐mediated regulatory mechanisms in MC.     

Effect of copper excess on H2O2 accumulation and peroxidase activities in bean roots

We studied oxidative stress and peroxidase activity resulting from application of excess copper in the nutrient medium on the roots of young bean seedlings. The change in H2O2 content, lipid peroxidation and antioxidant enzymes activities were quantified and located. Excess of copper caused a loss of membrane integrity and the formation of hydrogen peroxide (H2O2) as visualized in the transmission electron microscopy and measured using spectrophotometry. H2O2 accumulated in the intercellular spaces and in the cell wall. The production of H2O2 was accompanied by an increase in the activity of soluble and ionic GPX (guaiacol peroxidase, EC 1.11.17), CAPX (coniferyl alcohol peroxidase) and NADH oxidase.     

Effects of cadmium and copper on peroxidase, NADH oxidase and IAA oxidase activities in cell wall, soluble and microsomal membrane fractions of pea roots

Twelve-day-old seedlings of pea (Pisum sativum L.) that were treated for 4 days by 20 and 100 micromol/l Cd(NO3)2 or CuSO4 showed a growth reduction in all organs. From root protein extracts, the activities of guaiacol peroxidase (GPX; EC 1.11.1.7), ascorbate peroxidase (APX; EC 1.11.1.11), coniferyl alcohol peroxidase (CAPX), NADH oxidase, and indole-3-acetic acid (IAA) oxidase were measured in covalently--and ionically--[symbol: see text] bound cell wall, soluble, and microsomal membrane fractions. With the exception of 20 micromol/l Cu, metal treatments enhanced GPX activity in all fractions. Only IAA oxidase activity was metal-elevated in the covalently bound cell wall fraction, while the ionic one showed Cd stimulation for all assayed enzymic activities. These effects were not entirely observed in Cu-treated plants, since APX and IAA oxidase activities were only enhanced in this fraction. However, soluble extract showed stimulation of APX activity, while in the microsomal fraction metal exposure also increased the activities of CAPX and NADH oxidase. Differential responses of root cell fractions to the presence of cadmium and copper ions are discussed in regard to the contribution of their enzymic capacities in antioxidant, lignification, and auxin degradation pathways. Comparisons between metals and dose effects are also underlined.     

Permeability of Plant Young Root Endodermis to Cu Ions and Cu-Citrate Complexes in Corn and Soybean

The non-selective apoplastic passage of Cu and Cu-citrate complexes into the root stele of monocotyledonous corn and dicotyledonous soybean was investigated using an inorganic-salt-precipitation technique. Either Cu ions or Cu-citrate complexes were drawn into root through the apoplast from the root growth medium, and K₄[Fe(CN)₆] was subsequently perfused through xylem vessels or the entire root cross section. Based on microscopic identification of the reddish-brown precipitates of copper ferrocyanide in the cell walls of the xylem of corn and soybean roots, Cu²⁺ passed through the endodermal barrier into the xylem of both species. When the solution containing 200 μM CuSO₄ and 400 μM sodium citrate (containing 199.98 μM Cu-citrate, 0.02 μM Cu²⁺) was drawn via differential pressure gradients into the root xylem while being perfused with K₄[Fe(CN)₆] through the entire root cross-section, reddish-brown precipitates were observed in the walls of the stele of soybean, but not corn root. However, when a CuSO₄ solution containing 0.02 or 0.2 μM free Cu²⁺ was used, no reddish-brown precipitates were detected in the stele of either of the two plants. Results indicated that endodermis was permeable to Cu-citrate complexes in primary roots of soybean, but not corn. The permeability of the endodermal barrier to the Cu-citrate complex may vary between dicotyledonous and monocotyledonous plants, which has considerable implications for chelant-enhanced phytoextraction.     

Inhibitory effects of copper on bacteria related to the free ion concentration

Cu²⁺ ion determinations were carried out in complex and in inorganic salts-glycerol media, to which increasing amounts of Cu(II) had been added, with the ion-specific Cu(II)-Selectrode. Likewise, complexing capacity of bacterial suspensions was estimated by titration with CuSO₄.Copper-sensitive bacteria, e.g.,Klebsiella aerogenes, were inhibited in their growth and survival in the range of 10^–8–10^–6 M Cu²⁺ ion concentrations. In copper-buffered complex media, high copper loads could be tolerated, as growth proceeded with most of the copper bound to medium components. In low-complexing mineral salts media, in which high Cu²⁺ ion concentrations exist at low copper loads, there was competition of Cu²⁺ for binding sites of the cells. Total allowed copper was then determined by the ratio of copper to biomass.Copper-resistant bacteria could be isolated from a stock solution of CuSO₄, containing 100 ppm Cu(II). They were of thePseudomonas type and showed a much higher tolerance towards Cu²⁺, up to 10^–3 M.     

Response to copper excess in Arabidopsis thaliana: Impact on the root system architecture,hormone distribution,lignin accumulation and mineral profile

Growth, in particular reorganization of the root system architecture, mineral homeostasis and root hormone distribution were studied in Arabidopsis thaliana upon copper excess. Five-week-old Arabidopsis plants growing in hydroponics were exposed to different Cu²⁺ concentrations (up to 5 μM). Root biomass was more severely inhibited than shoot biomass and Cu was mainly retained in roots. Cu²⁺ excess also induced important changes in the ionome. In roots, Mg, Ca, Fe and Zn concentrations increased, whereas K and S decreased. Shoot K, Ca, P, and Mn concentrations decreased upon Cu²⁺ exposure. Further, experiments with seedlings vertically grown on agar were carried out to investigate the root architecture changes. Increasing Cu²⁺ concentrations (up to 50 μM) reduced the primary root growth and increased the density of short lateral roots. Experiment of split-root system emphasized a local toxicity of Cu²⁺ on the root system. Observations of GUS reporter lines suggested changes in auxin and cytokinin accumulations and in mitotic activity within the primary and secondary root tips treated with Cu²⁺. At toxic Cu²⁺ concentrations (50 μM), these responses were accompanied by higher root apical meristem death. Contrary to previous reports, growth on high Cu²⁺ did not induce an ethylene production. Finally lignin deposition was detected in Cu²⁺-treated roots, probably impacting on the translocation of nutrients. The effects on mineral profile, hormonal status, mitotic activity, cell viability and lignin deposition changes on the Cu²⁺-induced reorganization of the root system architecture are discussed.     

Copper toxicity and sulfur metabolism in Chinese cabbage are affected by UV radiation

Biomass production, dry matter content, specific leaf area and pigment content of Chinese cabbage were all quite similar, when plants were grown in the absence or presence of UV-A + B (2.2 mW cm⁻²). Elevated Cu²⁺ concentrations (2–10 μM) in the root environment and UV radiation had negative synergistic effects for Chinese cabbage and resulted in a more rapid and stronger decrease in plant biomass production and pigment content. The quantum yield of photosystem II photochemistry (F_v/F_m) was only decreased at ≥5 μM Cu²⁺ in the presence of UV radiation, when leaf tissue started to become necrotic. The enhanced Cu toxicity in the presence of UV was largely due to a UV-induced enhanced accumulation of Cu in both roots and shoots. An enhanced Cu content strongly affected the uptake and assimilation of sulfur in plants. The total sulfur content of the root increased at ≥2 μM Cu²⁺ in presence of UV and at 10 μM Cu²⁺ in absence of UV and that of the shoot increased at ≥2 μM Cu²⁺ in presence of UV and at ≥5 μM Cu²⁺ in absence of UV. In the shoot it could be attributed mainly to an increase in sulfate content. Moreover, there was a strong increase in the water-soluble non-protein thiol content upon Cu²⁺ exposure in the root and, to a lesser extent in the shoot, both in the presence and absence of UV. The regulation of the uptake of sulfate responded to the occurrence of Cu toxicity directly, since it was more rapidly affected in the presence than in the absence of UV radiation. For instance, the expression and activity of the high affinity sulfate transporter, Sultr1;2, were enhanced at ≥2 μM in the presence of UV, and at ≥5 μM Cu²⁺ in the absence of UV. In the shoot, the expression of the vacuolar sulfate transporter, Sultr4;1, was upregulated at ≥5 μM Cu²⁺ in the presence and absence of UV whilst the expression of a second vacuolar sulfate transporter, Sultr4;2, was upregulated at 10 μM Cu²⁺ in the presence of UV. It is suggested that high Cu tissue levels may interfere/react with the signal compounds involved in the regulation of expression and activity of sulfate transporters. The expression of adenosine 5′-phosphosulfate reductase in the root was hardly affected and was slightly down-regulated at 2 μM in the presence of UV and at 10 μM in the absence of UV. The expression and activity of sulfate transporters were enhanced upon exposure at elevated Cu²⁺ concentrations; this may not be simply due to a greater sulfur demand at higher Cu levels, but more likely is the consequence of Cu toxicity, since it occurred more rapidly in the presence compared to the absence of UV.     

Copper induced suppression of systemic microbial contamination in <Emphasis Type="Italic">Erythrina variegata</Emphasis> L. during in vitro culture

Latent infection is one of the major problem encountered in plant tissue culture, with no effective solution available so far. It is responsible for huge losses in terms of time, effort and money both in industrial and scientific laboratories. In the present investigation, we have used copper sulfate (CuSO₄) for effective control of latent infection in cultures of Erythrina variegata, without compromising on the growth of the culture. Culture media MS?+?BA (5.0 μM)?+?NAA (0.5 μM) were supplemented with different concentrations of CuSO₄, among the evaluated concentrations, 10.0 μM was found to be most suitable. The adventitious shoots produced per explant, average shoot length and chlorophyll content, increased in cultures growing on optimized CuSO₄, also, instances of endogenous infection were significantly reduced, but no signs of toxicity in plants could be detected. However, at higher concentration (>10 μM) of copper, albeit, infection was suppressed more effectively but the growth of plant was severely affected, recording significant reduction in numbers of shoots per explant, average shoot length and chlorophyll content. The results obtained demonstrate that copper optimization in plant tissue culture media provides twofold benefits; not only it improves the shoot multiplication rate and growth of the cultures, but, also effectively controls the problem of endogenous infection with no cytotoxicity.     

Effects of different sources of copper on Ctr1, ATP7A,ATP7B,MT and DMT1 protein and gene expression in Caco-2 cells

Copper sulfate (CuSO₄), micron copper oxide (micron CuO) and nano copper oxide (nano CuO) at different concentrations were, respectively, added to culture media containing Caco-2 cells and their effects on Ctr1, ATP7A/7B, MT and DMT1 gene expression and protein expression were investigated and compared. The results showed that nano CuO promoted mRNA expression of Ctr1 in Caco-2 cells, and the difference was significant compared with micron CuO and CuSO₄. Nano CuO was more effective in promoting the expression of Ctr1 protein than CuSO₄ and micron CuO at the same concentration. Nano CuO at a concentration of 62.5 μM increased the mRNA expression levels of ATP7A and ATP7B, and the difference was significant compared with CuSO₄. The addition of CuSO₄ and nano CuO to the culture media promoted the expression of ATP7B proteins. CuSO₄ at a concentration of 125 μM increased the mRNA expression level of MT in Caco-2 cells, and the difference was significant compared with nano CuO and micron CuO. Nano CuO at a concentration of 62.5 μM inhibited the mRNA expression of DMT1, and the difference was significant compared with CuSO₄ and micron CuO. Thus, the effects of CuSO₄, micron CuO and nano CuO on the expression of copper transport proteins and the genes encoding these proteins differed considerably. Nano CuO has a different uptake and transport mechanism in Caco-2 cells to those of CuSO₄ and micron CuO.     

Copper and mercury induced oxidative stresses and antioxidant responses of Spirodela polyrhiza (L.) Schleid

Duckweed is recognized as a phytoremediation aquatic plant due to the production of large biomass and a high level of tolerance in stressed conditions. A laboratory experiment was conducted to investigate antioxidant response and mechanism of copper and mercury tolerance of S. polyrhiza (L.) Schleid. To understand the changes in chlorophyll content, MDA, proline, and activities of ROS-scavenging enzymes (SOD, CAT, GPOD) during the accumulation of Cu⁺² and Hg⁺², S. polyrhiza were exposed to various concentrations of Cu⁺² (0.0–40 μM) and Hg⁺² (0.0–0.4 μM). antioxidant activity initially indicated enhancing trend with application of 10 μM Cu⁺²; 0.2 μM Hg⁺² (SOD), of 20 μM Cu⁺²; 0.2 μM Hg⁺² (CAT) and of 10 μM Cu⁺²;0.2 μM Hg⁺² (GPOD) and then decreased consistently up to 40 μM Cu⁺² and 0.4 μM Hg⁺². In the experiment chlorophyll and frond multiplication initially showed increasing tendency and decreased gradually with the application of increased metal concentration. Application of heavy metal has constantly enhanced proline and MDA content while the maximum increase was observed with the application of 40 μM Cu; 0.4 μM Hg for proline and MDA respectively. The upregulation of antioxidant enzymes and proline reveals that S. polyrhiza has strong biochemical strategies to deal with the heavy metal toxicity induced by the accumulation of Cu⁺² and Hg⁺².     

Copper supply and the leaf emergence rate of spring wheat

Copper deficiency can delay flowering and plant maturity. However, the effect of copper deficiency on the rate of leaf emergence has not been quantified. We tested the hypothesis that low copper supply decreases the rate of leaf emergence of wheat (Triticum aestivum L. cv Gamenya). Copper foliar sprays are commonly applied to wheat. We examined the response of the rate of leaf emergence to a foliar application of copper sulphate.Wheat was grown in root cooling tanks (20°C) in the glasshouse. Soil copper treatments were applied as solutions of CuSO₄.5H₂O at three rates: Cu₀=no added Cu, Cu₄₀₀=400 g Cu per 3 kg pot, and Cu₁₆₀₀=1600 g Cu per pot. An additional treatment of a foliar spray of CuSO₄.5H₂O (0.4 mg Cu per plant) was applied to Cu₀ and Cu₄₀₀ plants 45 days after sowing (5.5 leaves on the main stem). Leaves on the main stem were counted and the rate of leaf emergence was estimated from the regression of number of emerged leaves against thermal time (base 0°C). The phyllochron was calculated as 1/rate of emergence.Leaves on Cu₀ and Cu₄₀₀ plants took longer to emerge than on Cu₁₆₀₀ plants, with the phyllochron of Cu₁₆₀₀ plants being 130 compared to 137 for the Cu₄₀₀ plants and 158 for the Cu₀ plants. The foliar application of CuSO₄ at the 5–6 leaf stage resulted in a decrease in the phyllochron of the Cu₀ plants to 127, but no change in that of the Cu₄₀₀ plants.     

Interactions of free copper (II) ions alone or in complex with iron (III) ions with erythrocytes of marine fish Dicentrarchus labrax

As a consequence of human activity, various toxicants - especially metal ions - enter aquatic ecosystems and many fish are exposed to considerable levels. As the free ion and in some complexes, there is no doubt that copper promotes damage to cellular molecules and structures through radical formation. Therefore, we have investigated the influence of copper uptake by the red blood of the sea bass (Dicentrarchus labrax), and its oxidative action and effects on cells in the presence of complexed and uncomplexed Fe³⁺ ions.Erythrocytes were exposed to various concentrations of CuSO₄, Fe(NO₃)₃, and K₃Fe(CN)₆ for up to 5 h, and the effects of copper ions alone and in the combination with iron determined. The results show that inside the cells cupric ion interacts with hemoglobin, causing methemoglobin formation by direct electron transfer from heme Fe²⁺ to Cu²⁺. Potassium ferricyanide as a source of complexed iron decreases Met-Hb formation induced by copper ions unlike Fe(NO₃)₃. We also found that incubation of fish erythrocytes with copper increased hemolysis of cells. But complexed and uncomplexed iron protected the effect of copper. CuSO₄ increased the level of lipid peroxidation and a protective effect on complexed iron was observed. Incubation of erythrocytes with copper ions resulted in the loss of a considerable part of thiol content at 10 and 20 μM. This effect was decreased by potassium ferricyanide and Fe(NO₃)₃ only after 1 and 3 h of incubation. The level of nuclear DNA damage assayed by comet assay showed that 20 μM CuSO₄ as well as 20 μM Fe(NO₃)₃ and 10 mM K₃Fe(CN)₆ induce single- and double-strand breaks. The lower changes were observed after the exposure of cells to K₃Fe(CN)₆. The data suggest that complexed iron can act protectively against copper ions in contrast to Fe(NO₃)₃.     

Copper-induced oxidative damage, antioxidant response and genotoxicity in Lycopersicum esculentum Mill. and Cucumis sativus L.

Adequate copper (Cu²⁺) concentrations are required for plants; however, at higher concentrations it can also cause multiple toxic effects. In the present study, lipid peroxidation, hydrogen peroxide levels as well as ascorbate peroxidase (APX: EC 1/11/1/11) and catalase (CAT: EC 1.11.1.6) activities were determined in Lycopersicum esculentum Mill. and Cucumis sativus L. seedlings after 7-day exposure to copper sulfate. In addition, DNA damage in these two crops was assessed by measuring micronucleus (MN) frequency and tail moments (TM) as determined by Comet assay. Inhibitory copper concentrations (EC₅₀: 30 and 5.5 ppm for L. esculentum and C. sativus, respectively) were determined according to dose-dependent root inhibition curves, and EC₅₀ and 2×EC₅₀ were applied. Malondialdehyde (MDA) and H₂O₂ levels significantly increased in all groups studied. CAT activity increased in treatment groups of C. sativus. APX activity increased in L. esculentum seedlings due to 2×EC₅₀ treatment. Reductions in mitotic indices (MI) represented Cu²⁺dependent root growth inhibition in all treatment groups studied. According to TMs and MN frequencies, copper exposure induced significant DNA damage (p < 0.05) in all study groups, whereas the DNA damage induced was dose dependent in C. sativus roots. In conclusion, Cu²⁺induced oxidative damage, elevations in H₂O₂ levels and alterations in APX and CAT activities, as well as significant DNA damage in nuclei of both study groups. To our knowledge, this is the first comparative and comprehensive study demonstrating the effects of copper on two different plant species at relevant cytotoxic concentrations at both biochemical and genotoxicity levels with multiple end points.     

Increase of Copper Toxicity to Growth of Chlorella vulgaris with Increase of Light Intensity

Abstract In the absence of inhibitory concentrations of copper, the photoautotrophic growth of Chlorella vulgaris INETI58C at 27°C exhibited a higher specific growth rate and reached a higher maximal concentration of biomass, under irradiance of 150 W m⁻², compared with 100 W m⁻². However, when the mineral growth medium was supplemented with CuSO₄ (range 40–80 μM), algal growth was significantly affected at the higher light intensity. In the presence of Cu²⁺, the increase in dry biomass was uncoupled from the increase in cell concentration since more than 16 autospores gathered together, inside the enlarged mother cell, suggesting that copper arrested the normal bursting of the mother cell wall. At the higher irradiance, growth medium supplementation with 80 μM of CuSO₄ led to bleaching of photosynthetic pigments. No growth was observed, while, under the lower irradiance, growth was only slightly inhibited. Results clearly showed that copper toxicity to growth of C. vulgaris was strongly influenced by light intensity. Higher light intensity elicits lethal or sublethal Cu²⁺ damage at concentrations lower than the threshold level for damage at lower light intensities. Cu²⁺ may elicit lethal or sublethal light damage at irradiances lower than the threshold level for unpolluted aquatic systems. Received: 17 January 1997; Accepted 15 April 1997     

Volatile essential oil chemical composition of basil (<Emphasis Type="Italic">Ocimum basilicum</Emphasis> L. ‘Green’) cultivated in a greenhouse and micropropagated on a culture medium containing copper sulfate

The objective of this study was to determine the effects of copper sulfate (CuSO₄) on the chemical composition of basil (Ocimum basilicum L. ‘Green’) using static headspace extraction. The basil was cultivated in vitro and ex vitro. The sowing was completed in trays, and the seedlings were transplanted to pots and grown in a protected environment for 180 d. For in vitro cultivation, the seeds were placed on Murashige and Skoog (MS) medium enriched with growth regulators, sucrose, agar, and CuSO₄ (at 0 μM [control], 25 μM, or 75 μM). Volatile organic compounds emitted from the excised leaves were collected by the static headspace technique, and identified by gas chromatography coupled to mass spectrometry (GC/MS). Twenty-six compounds were identified in the leaves harvested from the plants cultivated in vitro, while 11 compounds were identified in the leaves sampled from the ex vitro plants. Oxygenated monoterpenes were the main compounds found in plants cultivated ex vitro. Phenylpropanoids predominated in the control and the 25 μM CuSO₄ treatments. The main compounds found were methyl eugenol (52.03%) and eugenol (20.66%). For the 75 μM CuSO₄ treatment, the major compounds detected were linalool (28.14%) and 1.8-cineole (15.7%). Volatile secondary metabolites of basil cultivated in vitro with CuSO₄ were easily isolated and rapidly obtained. The results of this study demonstrate the feasibility and potential of using copper treatments to reduce the impact of seasonality on essential oil production.     

Effects of Irradiance and Copper on the Activity of Ascorbate Oxidase in Detached Rice Leaves

The effects of copper on the activity of ascorbic acid oxidasc (AAO) in detached rice leaves under both light and dark conditions and in etiolated rice seedlings were investigated. CuSO₄ increased AAO activity in detached rice leaves in both light and darkness, however, the induction in darkness was higher than in the light. In the absence of CuSO₄, irradiance (40 μmol m^-2 s^-1) resulted in a higher activity of AAO in detached rice leaves than dark treatment. Both CuSO₄ and CuCl₂ increased AAO activity in detached rice leaves, indicating that AAO is activated by Cu. Sulfate salts of Mg, Mn, Zn and Fe were ineffective in activating AAO in detached leaves. CuSO₄ was also observed to increase AAO activity in the roots but not in shoots of etiolated rice seedlings. This revised version was published online in July 2006 with corrections to the Cover Date.     

Antioxidant response to cadmium in Phragmites australis plants

Phragmites (Phragmites australis Cav. (Trin.) ex Steud) plants exposed to a high concentration of CdSO₄ (50 μM) for 21 d were analysed with respect to the distribution of metal, its effects on antioxidants, the antioxidant enzymes and the redox status in leaves, roots and stolons. The highest accumulation of Cd²⁺ occurred in roots followed by leaves, and it was not significant in the stolons when compared with the control plants. In particular, in roots from Cd-treated plants, both the high amount of GSH and the parallel increase of glutathione-S-transferase (EC 2.5.1.18; GST) activity seemed to be associated with an induction of the detoxification processes in response to the high cadmium concentration. Superoxide dismutase (EC 1.15.1.1; SOD), ascorbate peroxidase (EC 1.11.1.11; APX), glutathione reductase (EC 1.6.4.2; GR) and catalase (EC 1.11.1.6; CAT) activities as well as reduced and oxidised glutathione contents in all samples of leaves, roots and stolons were increased in the presence of Cd²⁺ when compared to control plants. Despite the fact that Cd²⁺ has a redox characteristic not compatible with the Fenton-type chemistry that produces active oxygen species, the antioxidant response is widespread and generic. Increased activities of antioxidant enzymes in Cd-treated plants suggest that metal tolerance in Phragmites plants might be associated to the efficiency of these mechanisms.     

Biological effects of high copper and zinc concentrations and their interaction in rapeseed plants

In experiments with rapeseed (Brassica napus L., cv. Westar) plants, it was confirmed that copper was considerably more toxic than zinc. The toxic effects of 50 and 150 μM CuSO₄ were comparable to those of 1000 and 2500 μM ZnSO₄. The analysis of the effects of these concentrations of copper and zinc on photosynthetic pigment contents and on the rate of lipid peroxidation did not reveal any reasons for different toxicities of these heavy metals (HM). Among biological effects studied, significant differences were found in the organ distribution of these metals in plants grown on both the standard medium and the medium with high concentrations of copper or zinc. Copper retained in the roots in relatively small amounts and was poorly transported over the aboveground part of the plants. It stayed mainly in the lower leaves, and its distribution changed only a little during the recovery of plants following the HM treatment. In contrast, zinc proved to be highly mobile, it was concentrated in the upper leaves and actively transported when the plants were transferred to a medium with the optimal HM concentrations. High copper concentrations slowed strongly zinc uptake by the roots but practically did not change its movement over the plant. In contrast, high zinc concentrations facilitated copper uptake by the roots but reduced its transfer to the aboveground organs. The data presented here allow us to hypothesize that biological peculiarities of organ and cellular distribution of copper and zinc in plants and interaction of these HM play an important role in the toxic effects of high concentrations of these HM and the mechanisms of adaptation to them at industrial environmental pollution used by rapeseed plants.