Oxidative status of Matricaria chamomilla plants related to cadmium and copper uptake

Phytochemical Characterization of Chamomile (Matricaria recutita L.) Roots and Evaluation of Their Antioxidant and Antibacterial Potential

Matricaria recutita L., German chamomile, is one of the most widely used medicinal plants, whose efficacy has been proven in numerous studies. However, its roots have attracted only little interest so far, since mainly above-ground plant parts are used for medicinal purposes. To broaden the knowledge of chamomile roots, a profound phytochemical characterization was performed along with a bioactivity screening of corresponding root extracts. While volatile constituents such as chamomillol and polyynes were detected using GC-MS, HPLC-MSⁿ analyses revealed the occurrence of four coumarin glycosides, more than ten phenolic acid esters and five glyceroglycolipids. Furthermore, the antioxidant activity of the extracts was evaluated. Polar extracts revealed IC₅₀ values ranging from 13 to 57 µg/mL in the DPPH radical scavenging assay, which is in the same range as reported for chamomile flower extracts. In addition, superoxide radical scavenging potential and mild antibacterial effects against S. aureus und B. subtilis were demonstrated. Moreover, to assess interspecies variation in chamomile roots, extracts of M. recutita were compared to those of M. discoidea DC. Interestingly, the latter revealed stronger antioxidant activity. The presented results aim at the valorization of chamomile roots, previously discarded as by-product of chamomile flower production, as a sustainable source of bioactive phytochemicals.

Nitrogen modulates strontium uptake and toxicity in Hypericum perforatum plants

Strontium is an unavoidable element occurring in plants due to its abundance in the soil and similarity with calcium. To mimic natural conditions, impacts of additional inorganic (nitrate) or organic (urea and allantoin) nitrogen sources (1 mM of each N form in addition to 3.53 mM N in the basic cultivation solution) or N deficit on strontium-induced changes (100 µM Sr) in the widely used medicinal plant Hypericum perforatum L. were studied. Though various effects of Sr on primary (stimulation of amino acids but depression of most Krebs acids, ascorbic acid and thiols) and secondary metabolites (stimulation of phenols but no change of pseudo/hypericin) or mineral elements were observed (reduction of Ca amount in both shoots and roots), organic N forms often mitigated negative action of Sr or even combined stimulatory impact was observed. Organic N forms also elevated shoot accumulation of Sr while N deficit reduced it. Additional N forms, rather than Sr itself, modulated reactive oxygen species and nitric oxide formation in the root tissue. Germination experiment showed no toxicity of Sr to H. perforatum up to 1 mM Sr and even stimulated accumulation of amino acids and phenols, indicating similar ontogenetic-related responses.

Glyphosate does not show higher phytotoxicity than cadmium: Cross talk and metabolic changes in common herb

Toxicity of glyphosate (G) alone or in combination with cadmium (Cd) was studied in Matricaria chamomilla. Cadmium accumulated in shoots and roots in relation to prolonged exposure while glyphosate and aminomethylphosphonic acid (AMPA) were detected only in roots. After 7 days of exposure, root Cd and G accumulation was similar (56 μg G or 47 μg Cd/g DW in 1 μM treatments and 330 μg G or 321 μg Cd/g DW in 10 μM treatments). Despite this fact, Cd stimulated higher ROS formation and G rather suppressed nitric oxide while H2O2 content was elevated by Cd. Subsequent assay of antioxidative enzymes (SOD, CAT, and APX) showed only the impact of Cd. Non-enzymatic antioxidants revealed more pronounced impact of Cd on ascorbic acid and soluble phenols while non-protein thiols showed synergistic effect of G and Cd in roots. Surprisingly, G alone or in combination with Cd depleted shoot citrate and tartrate accumulation despite no detectable G in shoots. In the roots, Cd evoked expected increase in malate and citrate content while G rather suppressed Cd-induced elevation. These data indicate that glyphosate is less toxic than cadmium but even low G doses are able to induce metabolic changes.

Iron oxide nanoparticles: a novel elicitor to enhance anticancer flavonoid production and gene expression in Dracocephalum kotschyi hairy-root cultures

BACKGROUND

Dracocephalum kotschyi Boiss. is a valuable source of rosmarinic acid (RA) and methoxylated hydroxyflavones (such as xanthomicrol and cirsimaritin) with antioxidative and antiplatelet effects and with antiproliferative potential against various cancer cells. The extensive application of nanotechnology in hairy root cultures is a new sustainable production platform for producing these active constituents. In the present study, hairy roots derived from 4-week-old leaves and Agrobacterium rhizogenes strain ATCC15834 were used to investigate the impact of various concentrations of iron oxide nanoparticles (Fe NPs) in two elicitation time exposures (24 and 48 h) on growth, antioxidant enzyme activity, total phenolic and flavonoid content (TPC and TFC), and some polyphenols. Gene expression levels of phenylalanine ammonia-lyase (pal) and rosmarinic acid synthase (ras) were also analyzed.

RESULTS

Iron nanoparticles enhanced biomass accumulation in hairy roots. The treatment time and Fe NP dosage largely improved the activity of antioxidant enzymes, TPC and TFC. The highest RA (1194 μg g^-1 FW) content (9.7-fold), compared to controls, was detected with 24 h of exposure to 75 mg L^-1 Fe NP, which was consistent with the expression of pal and ras genes under the influence of elicitation. The xanthomicrol, cirsimaritin, and isokaempferide content was increased 11.87, 3.85, and 2.27-fold, respectively.

CONCLUSION

Stimulation of D. kotschyi hairy roots by Fe NPs led to a significant increase in the induction and production of important pharmaceutical compounds such as rosmarinic acid and xanthomicrol. © 2019 Society of Chemical Industry.

The combined and single effect of salinity and copper stress on growth and quality of Mentha spicata plants

Copper is essential for plant growth, but in excess may cause adverse effects on plant physiology. Harmful effects are also caused by plant exposure to salinity (NaCl) due to the excessive use of fertilizers, soil degradation and/or the quality of the water used for irrigation. The impact of single and combined salinity (Sal) and copper (Cu) stress on spearmint metabolism were studied in hydroponics. Spearmint plants (Mentha spicata L.) were subjected to salinity stress (150 mM NaCl) and/or excessive Cu concentration (60 μM Cu) via the nutrient solution. Not only Sal and Cu, but also their combination suppressed plant growth by decreasing plant biomass, root fresh weight and plant height. Chlorophyll content decreased mainly for the combined stress treatment (Sal + Cu). Polyphenols and antioxidants (FRAP, DPPH, ABTS) increased in single stress treatments (Sal or Cu), but decreased in the combined stress (Sal + Cu). The application of Sal or Cu stress decreased Zn, N and K (leaves), K, Ca, P and Mg (roots) content. Copper application increased Ca and Mg in leaves. In conclusion, salinity stress and Cu exposure may change the primary metabolic pathways in favor of major volatile oil components biosynthesis, resulting in significant changes of essential oil yield and composition.

Heavy metals in contaminated environment: Destiny of secondary metabolite biosynthesis, oxidative status and phytoextraction in medicinal plants

Contamination of soils, water and air with toxic heavy metals by various human activities is a crucial environmental problem in both developing and developed countries. Heavy metals could be introduced into medicinal plant products through contaminated environment (soil, water and air resources) and/or poor production practices. Growing of medicinal plants in heavy metal polluted environments may eventually affect the biosynthesis of secondary metabolites, causing significant changes in the quantity and quality of these compounds. Certain medicinal and aromatic plants can absorb and accumulate metal contaminants in the harvestable foliage and, therefore, considered to be a feasible alternative for remediation of polluted sites without any contamination of essential oils. Plants use different strategies and complex arrays of enzymatic and non-enzymatic anti-oxidative defense systems to cope with overproduction of ROS causes from the heavy metals entered their cells through foliar and/or root systems. This review summarizes the reports of recent investigations involving heavy metal accumulation by medicinal plants and its effects on elicitation of secondary metabolites, toxicity and detoxification pathways, international standards regarding in plants and plant-based products, and human health risk assessment of heavy metals in soil-medicinal plants systems.

Cadmium and copper induced changes in growth, oxidative metabolism and terpenoids of Tanacetum parthenium

Morphological and biochemical responses of feverfew plants exposed to low (5 μM) and high (35 and 70 μM) levels of Cd or Cu were investigated. Increasing metal supply notably reduced the plant biomass. Elevated Cd and Cu levels also resulted in an increase in the leaf proline content. Besides, decrease in ascorbic acid (AsA) and glutathione (GSH) contents was similar in the leaves of Cd- and Cu-treated plants, indicating altered biosynthesis of AsA and GSH under metal excess. High metal doses stimulated increase in antioxidative enzyme activities that could be related to elevated hydrogen peroxide (H₂O₂) content and subsequent lipid peroxidation. Cd was typically more accumulated in shoots and roots than Cu, leading to higher translocation factor at high Cd doses. In terms of essential oil content, it seems that Cd had an inhibitory effect during the experiment, whereas Cu was found to stimulate it only at 5 μM. Furthermore, high Cd supply enhanced the relative proportion of monoterpene hydrocarbons, while Cu increased the proportion of sesquiterpenes, especially at 5 μM. This result provides the first evidence of the response of feverfew plants to Cd or Cu by associating stress-related responses with changes in terpenoids.

Age affects not only metabolome but also metal toxicity in Scenedesmus quadricauda cultures

Responses of Scenedesmus quadricauda grown in vitro and differing in age (old culture-13 months, young culture-1 month) to short-term cadmium (Cd) or nickel (Ni) excess (24h) were compared. Higher age of the culture led to lower amount of chlorophylls, ascorbic acid and glutathione but higher signal of ROS. Surprisingly, sucrose was detected using DART-Orbitrap MS in both old and young culture and subsequent quantification confirmed its higher amount (ca. 3-times) in the old culture. Cd affected viability and ROS amount more negatively than Ni that could arise from excessive Cd uptake which was also higher in all treatments than in respective Ni counterparts. Surprisingly, nitric oxide was not extensively different in response to age or metals. Strong induction of phytochelatin 2 is certainly Cd-specific response while Ni also elevated ascorbate content. Krebs cycle acids were more accumulated in the young culture but they were rather elevated in the old culture (citric acid under Ni excess). We conclude that organic solid 'Milieu Bristol' medium we tested is suitable for long-term storage of unicellular green algae (also successfully tested for Coccomyxa sp. and Parachlorella sp.) and the impact of age on metal uptake may be useful for bioremediation purposes.

Mechanisms of metal toxicity in plants

Metal toxicity in plants is still a global problem for the environment, agriculture and ultimately human health.

Physiology and methodology of chromium toxicity using alga Scenedesmus quadricauda as model object

Physiological responses of Scenedesmus quadricauda to Cr(VI) and Cr(III) excess were studied in buffer with circumneutral pH (6.5). Total Cr content was similar in low (1 μM of both oxidation states) but higher in 10 μM Cr(VI) treatment and high accumulation potential was detected (80-82% and 41-65% in 1 and 10 μM treatments, respectively). Specific fluorescence indicator (6-((anthracen-9-yl) methyleneamino)-2H-chromen-2-one) confirmed partial reduction of Cr(VI) to Cr(III) under exposure conditions. Viability and chlorophyll autofluorescence were more depleted by Cr(VI) while Cr(III) stimulated increase in ROS and lipid peroxidation. Antioxidative enzyme activities showed significantly higher values in 10 μM treatments of both Cr oxidation states. Depletion of mitochondrial proteins was not reflected in alteration of total soluble proteins indicating sensitivity of this organelle to Cr and TTC test showed no clear oxidation state-related effect. In this view, "Cr(VI) is not more toxic than Cr(III)" at least for some parameters. Subsequent study with the application of 10 μM Cr(VI) confirmed that HEPES buffer is more suitable exposure solution for toxicological studied than water or inorganic salts (higher chlorophyll autofluorescence was observed) and pH 6.5 is more suitable than low or high pH (4.5 or 8.5) in terms of Cr uptake. Another known Cr(III) fluorescence indicator (naphthalimide-rhodamine) also confirmed partial reduction of Cr(VI) to Cr(III) at acidic pH but only traces were seen at alkaline pH.

Toxicity of naturally-contaminated manganese soil to selected crops

The impact of manganese excess using naturally contaminated soil (Mn-soil, pseudototal Mn 6494 vs 675 μg g(-1) DW in control soil) in the shoots of four crops was studied. Mn content decreased in the order Brassica napus > Hordeum vulgare > Zea mays > Triticum aestivum. Growth was strongly depressed just in Brassica (containing 13696 μg Mn g(-1) DW). Some essential metals (Zn, Fe) increased in Mn-cultured Brassica and Zea, while macronutrients (K, Ca, Mg) decreased in almost all species. Toxic metals (Ni and Cd) were rather elevated in Mn-soil. Microscopy of ROS, NO, lipid peroxidation, and thiols revealed stimulation in all Mn-cultured crops, but changes were less visible in Triticum, a species with low shoot Mn (2363 μg g(-1) DW). Antioxidative enzyme activities were typically enhanced in Mn-cultured plants. Soluble phenols increased in Brassica only while proteins rather decreased in response to Mn excess. Inorganic anions (chloride, sulfate, and phosphate) were less accumulated in almost all Mn-cultured crops, while the nitrate level rather increased. Organic anions (malate, citrate, oxalate, acetate, and formate) decreased or remained unaffected in response to Mn-soil culture in Brassica, Hordeum, and Triticum but not in Zea. However, the role of organic acids in Mn uptake in these species is not assumed. Because control and Mn-soil differed in pH (6.5 and 3.7), we further studied its impact on Mn uptake in solution culture (using Mn concentration ∼5 mM deducted from water-soluble fraction of Mn-soil). Shoot Mn contents in Mn-treated plants were similar to those observed in soil culture (high in Brassica and low in Triticum) and pH had negligible impact. Fluorescence indicator of "general ROS" revealed no extensive or pH-dependent impact either in control or Mn-cultured roots. Observed toxicity of Mn excess to common crops urges for selection of cultivars with higher tolerance.

Hexavalent chromium damages chamomile plants by alteration of antioxidants and its uptake is prevented by calcium

Toxicity of low (3μM) and high (60 and 120μM) concentrations of hexavalent chromium/Cr(VI) in chamomile plants was studied. Fluorescence staining confirmed reduction of Cr(VI) to Cr(III). Cr was mainly accumulated in the roots with translocation factor <0.007. Notwithstanding this, both shoots and roots revealed increase in oxidative stress and depletion of glutathione, total thiols, ascorbic acid and activities of glutathione reductase and partially ascorbate peroxidase mainly at 120μM Cr. Though some protective mechanisms were detected (elevation of nitric oxide, enhancement of GPX activity and increase in phenols and lignin), this was not sufficient to counteract the oxidative damage. Consequently, soluble proteins, tissue water content and biomass production were considerably depleted. Surprising increase in some mineral nutrients in roots (Ca, Fe, Zn and Cu) was also detected. Subsequent experiment confirmed that exogenous calcium suppressed oxidative symptoms and Cr uptake but growth of chamomile seedlings was not improved. Alteration of naturally present reductants could be a reason for Cr(III) signal detected using specific fluorescence reagent: in vitro assay confirmed disappearance of ascorbic acid in equimolar mixture with dichromate (>96% at pH 4 and 7) while such response of glutathione was substantially less visible.

Contribution of reactive oxygen species (ROS) to genotoxicity of nitrobenzene on V. faba

Nitrobenzene is an important organic intermediate widely used in industry that can be hazardous to the environment. In our previous study, nitrobenzene showed genotoxic effect on soybean and tobacco plants at concentrations in the culture medium higher than 10 mg/L. The genotoxicity of nitrobenzene has been hypothesized to be multifactorial and reflective of the generation of free radicals; however, the mechanism has not been fully elucidated. The aim of this study was to investigate the relationship between the induction of genotoxicity and the production of free radicals in young seedlings of V. faba exposed to nitrobenzene, nitrobenzene + Vitamin C, and the controls (distilled water or Vitamin C). Micronucleus and chromosome aberration assays performed on root and leaf tissue of V. faba seedlings exposed to nitrobenzene (25 mg/L) demonstrated genotoxic effects which were partly reduced by Vitamin C at 25 mg/L. Increases in lipid peroxidase, O2•-, H2O2, superoxide dismutase and catalase activities were also observed in these tissues along with an attenuation of their induction by Vitamin C. Concomitant occurrence of genotoxicity and the generation of free radicals that are attenuated in the presence of Vitamin C, a scavenger of cellular free radicals, indicate that reactive oxygen species may contributes to genotoxicity of nitrobenzene in V. faba. These results are valuable for further understanding the genotoxicity mechanism of nitrobenzene.

Oxidative stress, uptake and bioconversion of 5-fluorouracil in algae

Impact of cytostatic drug 5-fluorouracil (FU) and its metabolite 2-fluoro-3-alanine (FA) on green alga Scenedesmus quadricauda was studied. FA elevated fluorescence signal of reactive oxygen species (ROS) more pronouncedly than FU at 1 and 10 μM doses while both ROS and reactive nitrogen species (RNS/NO) increased more expressively in 100 μM FU treatment. Cellular damage staining (Acridine Orange and Calcofluor White) did no reveal substantial difference between FU and FA. Majority of free amino acids including proline was unaffected after 24h of exposure. FA depleted ascorbate peroxidase activity more than FU therefore ascorbate content (AsA) was less affected while FU stimulated glutathione reductase activity less than FA and therefore glutathione (GSH) was more depleted. Both compounds accumulated concentration-dependently with higher absolute FA amounts but FU conversion to FA was also detected. We subsequently influenced 100 μM FU- and FA-induced changes using known ROS (DTT - dithiothreitol) and RNS/NO (SNP - sodium nitroprusside and PTIO - 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) modulators and results showed that PTIO depleted NO and elevated ROS while the opposite was found after SNP and DTT addition. Changes of lipid peroxidation (using BODIPY staining) confirmed that FU and FA toxicity is related to alteration of ROS/RNS balance.

Unexpected behavior of some nitric oxide modulators under cadmium excess in plant tissue

Various nitric oxide modulators (NO donors - SNP, GSNO, DEA NONOate and scavengers – PTIO, cPTIO) were tested to highlight the role of NO under Cd excess in various ontogenetic stages of chamomile (Matricaria chamomilla). Surprisingly, compared to Cd alone, SNP and PTIO elevated Cd uptake (confirmed also by PhenGreen staining) but depleted glutathione (partially ascorbic acid) and phytochelatins PC₂ and PC₃ in both older plants (cultured hydroponically) and seedlings (cultured in deionised water). Despite these anomalous impacts, fluorescence staining of NO and ROS confirmed predictable assumptions and revealed reciprocal changes (decrease in NO but increase in ROS after PTIO addition and the opposite after SNP application). Subsequent tests using alternative modulators and seedlings confirmed changes to NO and ROS after application of GSNO and DEA NONOate as mentioned above for SNP while cPTIO altered only NO level (depletion). On the contrary to SNP and PTIO, GSNO, DEA NONOate and cPTIO did not elevate Cd content and phytochelatins (PC₂, PC₃) were rather elevated. These data provide evidence that various NO modulators are useful in terms of NO and ROS manipulation but interactions with intact plants affect metal uptake and must therefore be used with caution. In this view, cPTIO and DEA NONOate revealed the less pronounced side impacts and are recommended as suitable NO scavenger/donor in plant physiological studies under Cd excess.

Manganese-induced oxidative stress in two ontogenetic stages of chamomile and amelioration by nitric oxide

Impact of manganese (Mn(2+)) excess (100, 500 and 1000 μM over 7 days) on two ontogenetic stages (7-week-old plants and 7-day-old seedlings) of Matricaria chamomilla was compared. Mn excess depressed growth of seedlings (but not germination) and stimulated oxidative stress (ROS and lipid peroxidation) in both plants and seedlings. Growth inhibition could be evoked by higher Mn uptake and higher translocation factor in seedlings than in plants. Total thiols staining revealed elevation in almost all treatments. In 7-week-old plants, activity of peroxidases increased slightly and rather decreased under high Mn doses. Superoxide rather than hydrogen peroxide contributed to visualized ROS presence. Fluorescence of nitric oxide (NO) showed stimulation in plants but decrease in seedlings. Impact of exogenous nitric oxide donor (sodium nitroprusside/SNP) was therefore tested and results showed amelioration of 1000 μM Mn-induced oxidative stress in seedlings (decrease in H2O2 and increase in NO content while antioxidative enzyme activities were variably affected) concomitantly with depleted Mn accumulation. It is concluded that NO participates in tolerance to Mn excess but negative effects of the highest SNP dose were also observed. Extensive fluorescence microscopy is also explanatively discussed.

Chromium uptake and consequences for metabolism and oxidative stress in chamomile plants

Chromium Cr(III) toxicity toward chamomile metabolism and oxidative stress-related parameters after 7 days of exposure was studied. Cr preferentially accumulated in the roots and evoked extensive both dose-dependent and dose-independent increase in fluorescence signals of ROS, NO and thiols. Superoxide increased mainly at the highest Cr dose, whereas H2O2 accumulation revealed a discontinuous trend in relation to external Cr supply, and this could be owing to variation in activities of peroxidases. Glutathione and ascorbate quantification, using LC-MS/MS equipment, revealed strong stimulation despite low shoot Cr amounts. Phenolic enzyme activities, except for PAL, were depressed by Cr presence, whereas phenolic metabolites were stimulated, indicating various time dynamics. Among free amino acids, their sum and even proline decreased in the roots, whereas soluble proteins increased. Mineral nutrients showed negligible responses with only Zn and Cu being depleted in both shoots and roots. Cr staining using Cr(III)-specific (naphthalimide-rhodamine) and metal nonspecific (Phen Green) dyes indicated that the former correlated well with AAS quantification of Cr amount. Use of Phen Green is also discussed. These data indicate that Cr-induced oxidative stress is not simply a function of exposure time and applied concentration. Microscopic observations in terms of oxidative stress and chromium uptake are presented here for the first time.

Cadmium-induced cyto- and genotoxicity are organ-dependent in lettuce

Cadmium is a priority pollutant. Its mechanisms and effects within different plant organs remain unclear. Here, cyto-genotoxicity biomarkers were evaluated in roots and leaves after Cd exposure (0, 1, 10, and 50 μM) of the model crop Lactuca sativa L. (cv. "Reine de Mai"). Overall, superoxide dismutase (SOD) and catalase (CAT) activities were stimulated in leaves, where Cd accumulation was lower in comparison to that in roots. In roots, SOD and peroxidase (POX, APX) activities were stimulated. Moreover, in both organs glutathione reductase (GR) was not affected by Cd. Overall, the H(2)O(2) content increased in both organs, while the total antioxidant capacity decreased in leaves and increased in roots with Cd concentrations. In both organs, lipid and protein oxidation rose with consequent increase of membrane permeability. Simultaneously, the comet assay showed that tail moment, tail length, and % tail DNA were maximum for 1 μM. For 10 μM, shorter tails were found suggesting induced Cd-DNA adducts that lead to DNA-DNA/DNA-protein cross-links, and/or formation of longer DNA fragments, and/or impairment of DNA repair mechanisms, while at 50 μM, nucleoids sensitivity to the technique was evident. This result was consistent with the maximum micronuclei frequency found for the 10 μM Cd dose in roots, suggesting that the surviving cells in this organ had an increase of mitotic catastrophe and that DNA repair systems for blocking cell cycle were dysfunctional. In lower Cd concentrations, root cells might have developed strategies to repair damaged DNA by blocking the cell cycle at specific checkpoints, thus avoiding mitotic catastrophe. Roots at 1 μM showed a cell cycle blockage trend at the G(2) checkpoint, while those at higher concentrations presented S phase delay. We finally discuss a general model of Cd-organ interaction covering these cyto- and genotoxic effects and the potential use of this cultivar in phytoremediation strategies.

Modulation of copper uptake and toxicity by abiotic stresses in Matricaria chamomilla plants

The impact of salinity (S) or nitrogen deficiency (-N) on copper (Cu) uptake and changes to metabolism were studied in the combined treatments after 7 days of exposure. S suppressed growth, water content, soluble proteins, and reducing sugars more negatively than -N. ROS (hydrogen peroxide and superoxide) were differentially but relatively slightly affected while peroxidase activities were strongly elevated mainly in Cu+NaCl variant. Total soluble phenols and individual phenolic acids (free and cell wall-bound fraction) were accumulated the most in Cu-N while, among free amino acids, proline sharply increased in Cu+NaCl; this suggests a compensatory mechanism between the syntheses of antioxidants aimed to maintain antioxidative protection because numerous root phenolic acids were even depressed by S. Salinity also suppressed accumulation of coumarin herniarin, but its glucosidic precursors ((Z)- and (E)-2-ß-D-glucopyranosyloxy-4-methoxycinnamic acids) increased. Activities of selected phenolic enzymes were rather suppressed by S after a given exposure period while lignin content increased, suggesting different time dynamics if S and -N variants are compared. Selected mineral nutrients (K, Fe, and partially Mg) were more reduced by S than by -N. Shoot and root Cu amounts were depressed by -N but elevated by S. Significance and possible role of observed metabolic changes in relation to Cu accumulation are discussed.

Responses of environmental Amycolatopsis strains to copper stress

Copper is a redox-active metal, which acts as a catalyst in the formation of Reactive Oxygen Species (ROS) encouraging oxidative stress. Protection against oxidants is intrinsic to every living cell; however, in stress conditions, cells are forced to increase and expand their antioxidative network. In this work, the novel copper-resistant strain Amycolatopsis tucumanensis and the copper-sensitive Amycolatopsis eurytherma were grown under copper increasing concentrations in order to elucidate the dissimilar effects of the metal on the strains viability, mainly on morphology and antioxidant capacity. Although biosorbed copper encouraged ROS production in a dose-dependent manner in both strains, the increase in ROS production from the basal level to the stress conditions in A. tucumanensis is lesser than in the copper-sensitive strain; likewise, in presence of copper A. eurytherma suffered inexorable morphological alteration while A. tucumanensis was not affected. The levels of antioxidant enzymes and metallothioneins (MT) were all greater in A. tucumanensis than in A. eurytherma; in addition MT levels as well as superoxide dismutase and thioredoxin reductase activities in A. tucumanensis, were higher as higher the concentration of copper in the culture medium. This work has given evidence that an efficient antioxidant defense system might aid microorganisms to survive in copper-stress conditions; besides it constitutes the first report of oxidative stress study in the genus Amycolatopsis and contributes to enlarge the knowledge on the copper-resistance mechanisms of A. tucumanensis.

Alleviation of copper-induced oxidative damage in Chlamydomonas reinhardtii by carbon monoxide

Carbon monoxide (CO) is an endogenous gaseous molecule in plants and animals. Recent studies have shown that it is one of the most essential cellular components regulating many aspects of plant growth and development. However, whether CO regulates the green algae adaptive response to heavy metal toxicity is unknown. The present study investigated the role of CO in regulating Cu-induced oxidative stress in eukaryotic algae Chlamydomonas reinhardtii. Cells pretreated with 5 μM CO for 30 min and followed by exposure to 5 μM Cu(II) for 4 days showed attenuated toxicity. The CO-improved growth of algae was correlated with reduced lipid peroxidation and increased chlorophyll accumulation. The beneficial effect of CO was confirmed by histochemical staining with reactive oxygen species. Further, treatment with 5 μM CO increased the activity of catalase with Cu. However, a reduced superoxide dismutase activity was observed in the CO + Cu-treated algae compared to the control (activity of Cu treatment alone). Under the same condition, the activity of ascorbate peroxidase was not significantly changed. These results suggest that CO can play an important role in regulating the response of algae to Cu stress.

Nitrate deficiency reduces cadmium and nickel accumulation in chamomile plants

The effect of nitrogen (nitrate) deficiency (-N) on the accumulation of cadmium (Cd) and nickel (Ni) in chamomile ( Matricaria chamomilla ) plants was studied. Elimination of N from the culture medium led to decreases in N-based compounds (free amino acids and soluble proteins) and increases in C-based compounds (reducing sugars, soluble phenols, coumarins, phenolic acids, and partially flavonoids and lignin), being considerably affected by the metal presence. Proline, a known stress-protective amino acid, decreased in all -N variants. The activity of phenylalanine ammonia-lyase was stimulated only in -N control plants, whereas the activities of polyphenol oxidase and guaiacol peroxidase were never reduced in -N variants in comparison with respective +N counterparts. Among detected phenolic acids, chlorogenic acid strongly accumulated in all N-deficient variants in the free fraction and caffeic acid in the cell wall-bound fraction. Mineral nutrients were rather affected by a given metal than by N deficiency. Shoot and total root Cd and Ni amounts decreased in -N variants. On the contrary, ammonium-fed plants exposed to N deficiency did not show similar changes in Cd and Ni contents. The present findings are discussed with respect to the role of phenols and mineral nutrition in metal uptake.

Assessment of heavy metal pollution in Republic of Macedonia using a plant assay

Different plant organs (leaves, flowers, stems, or roots) from four plant species-Urtica dioica L. (Urticaceae), Robinia pseudoacacia L. (Fabaceae), Taraxacum officinale (Asteraceae), and Matricaria recutita (Asteraceae)-were evaluated as possible bioindicators of heavy-metal pollution in Republic of Macedonia. Concentrations of Pb, Cu, Cd, Mn, Ni, and Zn were determined in unwashed plant parts collected from areas with different degrees of metal pollution by ICP-AES. All these elements were found to be at high levels in samples collected from an industrial area. Maximum Pb concentration was 174.52 ± 1.04 mg kg⁻¹ in R. pseudoacacia flowers sampled from the Veles area, where lead and zinc metallurgical activities were present. In all control samples, the Cd concentrations were found to be under the limit of detection (LOD <0.1 mg kg⁻¹) except for R. pseudoacacia flowers and T. officinale roots. The maximum Cd concentration was 7.97 ± 0.15 mg kg⁻¹ in R. pseudoacacia flowers from the Veles area. Nickel concentrations were in the range from 1.90 ± 0.04 to 5.74 ± 0.03 mg kg⁻¹. For U. dioica leaves and R. pseudoacacia flowers sampled near a lead-smelting plant, concentrations of 465.0 ± 0.55 and 403.56 ± 0.34 mg kg⁻¹ Zn were detected, respectively. In all control samples, results for Zn were low, ranging from 10.2 ± 0.05 to 38.70 ± 0.18 mg kg⁻¹. In this study, it was found that the flower of R. pseudoacacia was a better bioindicator of heavy-metal pollution than other plant parts. Summarizing the results, it can be concluded that T. officinale, U. dioica, and R. pseudoacacia were better metal accumulators and M. recutita was a metal avoider.

Chamomile (Matricaria chamomilla L.): An overview

Chamomile (Matricaria chamomilla L.) is a well-known medicinal plant species from the Asteraceae family often referred to as the "star among medicinal species." Nowadays it is a highly favored and much used medicinal plant in folk and traditional medicine. Its multitherapeutic, cosmetic, and nutritional values have been established through years of traditional and scientific use and research. Chamomile has an established domestic (Indian) and international market, which is increasing day by day. The plant available in the market many a times is adulterated and substituted by close relatives of chamomile. This article briefly reviews the medicinal uses along with botany and cultivation techniques. Since chamomile is a rich source of natural products, details on chemical constituents of essential oil and plant parts as well as their pharmacological properties are included. Furthermore, particular emphasis is given to the biochemistry, biotechnology, market demand, and trade of the plant. This is an attempt to compile and document information on different aspects of chamomile and highlight the need for research and development.

Tolerance of Silene vulgaris to copper: population-related comparison of selected physiological parameters

Tolerance of three Slovak populations of Silene vulgaris [from the localities "Harmanec" (total soil Cu 34.1 mg kg⁻¹), "Lubietová"; (total soil Cu 831.6 mg kg⁻¹) and "Špania dolina" (total soil Cu 1368.7 mg kg⁻¹) referred as SV1, SV2, and SV3, respectively] and Silene dioica (SD; from the locality "Špania dolina") exposed to 60 μM Cu for 7 days has been studied. Respective controls with 0.21 μM Cu were also cultured. SV3 and SD contained higher total shoot Cu than SV1. Methanol-soluble shoot Cu represented 60, 59, 59, and 55% from total shoot Cu and roots contained 16.7-, 20.4-, 9.9- and 28.9-fold more Cu than shoots in SV1, SV2, SV3, and SD, respectively. Soluble proteins were the least affected in SV3 and SD when Cu-exposed and control plants were compared. Root hydrogen peroxide and superoxide showed similar trend and were correlated with enhancement of ascorbate- and guaiacol-peroxidase activities. Malondialdehyde accumulation increased in SV1 and SV2. Phenylalanine ammonia-lyase activity and total soluble phenols were higher in SV3 Cu-exposed plants compared to SV1 and SV2. Shikimate dehydrogenase activity was enhanced in all Cu-exposed populations. Cinnamyl alcohol dehydrogenase activity and root lignin content were not affected and polyphenol oxidase activity was not detected. Within 14 detected free amino acids, majority of them decreased preferentially in the roots. Only serine increased in shoots and decreased in roots of all populations. Potassium content was not affected in SV3. Na, Ca, and Fe increased in roots of Cu-exposed plants of all populations, while Mg was the least affected and Zn increased in SV2 and SV3 shoots and roots. This study revealed the highest tolerance in population from the locality with the highest soil Cu content. Present findings as complex metabolic responses to Cu stress with special emphasis on phenolic metabolism are discussed.

Copper uptake is differentially modulated by phenylalanine ammonia-lyase inhibition in diploid and tetraploid chamomile

The effect of phenylalanine ammonia-lyase (PAL) inhibition by 2-aminoindane-2-phosphonic acid (AIP) in copper-exposed diploid and tetraploid chamomile (Matricaria chamomilla ) roots has been studied in a short-term experiment (24 h). Cu evoked stronger induction of PAL activity and accumulation of soluble phenols, flavonols (quercetin and kaempferol), and lignin in diploid plants, whereas AlCl3-reactive flavonoids and phenolic acids did not differ with respect to ploidy. Amounts of hydrogen peroxide and superoxide also preferentially increased in diploid. Surprisingly, PAL activity was restored in both +AIP cultivars, being inversely correlated with the accumulation of free phenylalanine. Notwithstanding this, total soluble phenols and flavonols were more depleted in Cu+AIP diploid roots. Soluble proteins decreased in response to Cu, and AIP had no effect. Among free amino acids, proline increased more visibly in Cu+AIP diploid, suggesting that this could be a protective mechanism in conditions with depleted content of phenols. Decrease in potassium content was ploidy-independent, calcium increased in all Cu variants, and Fe increased in Cu-exposed tetraploid. Shoot Cu content did not differ in Cu-exposed cultivars, but diploid roots contained more Cu. AIP decreased root Cu but increased shoot Cu amounts in diploid, whereas tetraploid plants did not exhibit similar responses. These data indicate that inhibition of root phenolic metabolism by AIP was effective enough, allowing Cu to accumulate in diploid shoots. The present findings are discussed in the context of available data about AIP effects and with respect to the role of phenols in metal uptake.

Effect of BSO-supplemented heavy metals on antioxidant enzymes in Arabidopsis thaliana

Activities of the ascorbate-glutathione cycle enzymes were investigated in leaves of Arabidopsis thaliana plants grown for 7 and 14 days in modified Hoagland nutrient solution containing Cd and Cu alone or supplemented with buthionine sulfoximine (BSO), an inhibitor of glutathione synthesis. In A. thaliana treated with Cd+BSO, the modifying BSO effect involved dehydroascorbate reductase (DHAR) activity after 7 days of treatment and ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR) activities after 14 days. DHAR activity increased, while activities of APX, MDHAR and GR decreased in comparison to that found with Cd alone. BSO supplied in combination with Cu modified the metal effect on APX activity after 7 days of exposure and on MDHAR activity after 14 days. Cu+BSO enhanced APX activity, but decreased MDHAR activity as compared to that with Cu alone. Similarities and varieties in the modifying BSO effect, depending on the metal, have been discussed. The modifying BSO effect was more pronounced in the plants exposed to Cd than Cu, and was opposite after 7 and 14 days. However, differences between the effects of the individual metals on the enzymes were greater after 7 days of plant exposure.

Differential effect of equal copper, cadmium and nickel concentration on biochemical reactions in wheat seedlings

Influence of 75 microM copper (Cu), cadmium (Cd) and nickel (Ni) on growth, tissue metal accumulation, non-protein thiols (NPT) and glutathione (GSH) contents, membrane damage, lipid peroxidation and protein oxidation as well as protease, glutathione S-transferase (GST) and peroxidase (POD) activities were studied in the shoots and roots of wheat seedlings after 7 days of metal exposure. The greatest growth reduction was found in response to Cu treatment; however accumulation of this metal in the wheat tissues was the lowest compared to the other metals used. All metals caused enhancement of electrolyte leakage from cells as well as increased lipid peroxidation and protein carbonylation. Proteolytic activity was enhanced only in Cu-exposed seedlings and in the roots it coincided with elevated protein carbonylation. The most pronounced increase in POD activity in the shoots was found after Ni treatment while in the roots in response to Cu. In contrast to Cu, application of Cd and Ni resulted in accumulation of NPT and induction of GST activity, which suggested involvement of these mechanisms in metal tolerance in wheat.

Fluroxypyr triggers oxidative damage by producing superoxide and hydrogen peroxide in rice (Oryza sativa)

The present study has evaluated effect of fluroxypyr concentrations 0-0.8 mg l(-1) (a widely-used herbicide for controlling annual or perennial weeds growth) on selected metabolic and stress-related parameters in Oryza sativa plants after 6 days of exposure. Increasing concentrations decreased shoot growth and accumulation of chlorophylls but had no effect on root biomass. Increasing doses led also to increase in superoxide radical, hydrogen peroxide and proline accumulation, while malondialdehyde, an indicator of lipid peroxidation, was constitutively elevated. Histochemical staining with nitroblue tetrazolium and 3, 3-diaminobenzidine were positively correlated with the generation of superoxide radical and H(2)O(2). The fluroxypyr-induced oxidative stress triggered significant changes in activities of superoxide dismutase, catalase, ascorbate peroxidase and peroxidase (POD). Activities of the antioxidant enzymes show a general increase at low fluroxypyr concentrations and a decrease at high fluroxypyr levels (except for POD). Analysis of naturing polyacrylamide gel electrophoresis confirmed these results. These data support the observation that fluroxypyr-triggered oxidative stress was responsible for the disturbance of the growth in the rice plants.

Nitric oxide signals ROS scavenger-mediated enhancement of PAL activity in nitrogen-deficient Matricaria chamomilla roots: side effects of scavengers

Owing to the abundance of phenolic metabolites in plant tissue, their accumulation represents an important tool for stress protection. However, the regulation of phenolic metabolism is still poorly known. The regulatory role of reactive oxygen species (ROS) in the activity of phenylalanine ammonia-lyase (PAL) in nitrogen (N)-deficient chamomile roots treated for 24 h was studied using three ROS scavengers [dithiothreitol (DTT), salicylhydroxamic acid, and sodium benzoate]. Scavengers decreased the level of hydrogen peroxide and/or superoxide (and up-regulated ascorbate/guaiacol peroxidase and glutathione reductase), but, surprisingly, stimulated PAL activity. This up-regulation was correlated with increases in nitric oxide (NO) content, total soluble phenols, selected phenolic acids, and, partially, lignin (being expressed the most in DTT-exposed roots). We therefore tested the hypothesis that NO may be involved in these changes. Application of 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) decreased PAL activity and the accumulation of soluble phenols in all treatments. Exogenous H(2)O(2) and NO also stimulated PAL activity and the accumulation of phenols. We conclude that NO, in addition to hydrogen peroxide, may regulate PAL activity during N deficiency. The anomalous effect of PTIO on NO content and possible mechanism of ROS scavenger-evoked NO increases in light of the current knowledge are also discussed.