Guaiacol Peroxidation Research Articles

The effect of silicon application and salicylic acid on enzymatic and non-enzymatic reactions of Scophularia striata L. under drought stress

Foliar spraying of salicylic acid (SA) and silicon (Si) was carried out as a moderator of drought stress on growth and antioxidant system in two different ecotypes of scrophularia striata as a medicinal plant. A factorial experiment was conducted based on a completely randomized design in three replications. The statistical analysis of the studied traits showed that drought stress decreased the length and weight (dry and fresh) traits of shoot, root and stem-to-root length ratio in Ilam ecotype, while the root length and root-to-stem length ratio increased in Abdanan ecotype. The interaction between salicylic acid (SA), silicon (Si) and drought stress caused an increase in root length and the root-to-stem length ratio in Abadanan ecotype, this interaction on root fresh weight was not significant. The application of drought stress led to a reduction in the content of total phenol, flavonoid, anthocyanin and ascorbic acid in both ecotypes, but the activity of ascorbate peroxidase (APX) enzyme increased in both ecotypes and polyphenol oxidase (PPO) in Ilam ecotype. The interaction between salicylic acid (SA), silicon (Si) and drought stress increased the enzyme antioxidant activity, catalase (CAT), guaiacol peroxide (GPX), as well as the content of flavonoid, ascorbic acid and phenol in Ilam ecotype (50% field capacity +drought stress) and Abdanan ecotype (50% field capacity). However, this interaction had no significant effect on the activity of ascorbate peroxidase (APX) enzyme. The general results showed that the simultaneous use of SA and Si improves the antioxidant defense in Scrophularia striata under drought stress.

Salicylic acid mediated physiological and biochemical alterations to confer drought stress tolerance in Zinnia ( Z. elegans )

Background: Protective role of salicylic acid against drought has been widely reported, but its effects on Zinnia elegans remain unknown.
 Hypotheses: Foliar salicylic acid (SA) improves water status, pigments, and antioxidant systems of Zinnia plants under drought stress.
 Studied species: Z. elegans (cv. Dreamland) were purchased from Chanan Seeds Store Lahore, Pakistan.
 Study site and dates: MNS University of Agriculture, Multan, Punjab, Pakistan; March-May, 2018.
 Methods: After two weeks of transplanting, one set of seedlings was exposed to drought stress (60 % field capacity, FC) while other control set was maintained at 100 % FC. Foliar SA (100 mg L-1) was applied to plants at drought initiation.
 Results: Foliar SA treatment to water stressed plants (60 % FC) increased the leaf area (46.89 cm2), shoot and root lengths (25 cm and 26.67 cm, respectively), leaf relative water content (75.98 %); chlorophyll a (0.68 mg g-1), chlorophyll b (0.38 mg g-1) and carotenoid concentrations (1.10 mg g-1); and catalase (116.67 U min-1 mg-1 protein), guaiacol peroxide (72 U min-1 mg-1 protein) and superoxide dismutase (93 U min-1 mg-1 protein) activities.
 Conclusions: Foliar SA could be used to minimize impacts of water stress in Zinnia plants.

Effect of Silver Nanoparticles on the In Vitro Regeneration, Biochemical, Genetic, and Phenotype Variation in Adventitious Shoots Produced from Leaf Explants in Chrysanthemum.

Novel and unique properties of nanomaterials, which are not apparent in larger-size forms of the same material, encourage the undertaking of studies exploring the multifaced effects of nanomaterials on plants. The results of such studies are not only scientifically relevant but, additionally, can be implemented to plant production and/or breeding. This study aimed to verify the applicability of silver nanoparticles (AgNPs) as a mutagen in chrysanthemum breeding. Chrysanthemum × grandiflorum (Ramat.) Kitam. ‘Lilac Wonder’ and ‘Richmond’ leaf explants were cultured on the modified MS medium supplemented with 0.6 mg·L−1 6-benzylaminopurine (BAP) and 2 mg·L−1 indole-3-acetic acid (IAA) and treated with AgNPs (spherical; 20 nm in diameter size; 0, 50, and 100 mg·L−1). AgNPs strongly suppressed the capability of leaf explants to form adventitious shoots and the efficiency of shoot regeneration. The content of primary and secondary metabolites (chlorophyll a, chlorophyll b, total chlorophylls, carotenoids, anthocyanins, phenolic compounds) and the activity of enzymatic antioxidants (superoxide dismutase and guaiacol peroxide) in leaf explants varied depending on the AgNPs treatment and age of culture. Phenotype variations of ex vitro cultivated chrysanthemums, covering the color and pigment content in the inflorescence, were detected in one 50 mg·L−1 AgNPs-derived and five 100 mg·L−1 AgNPs-derived ‘Lilac Wonder’ plants and were manifested as the color change from pink to burgundy-gold. However, no changes in inflorescence color/shape were found among AgNPs-treated ‘Richmond’ chrysanthemums. On the other hand, the stem height, number of leaves, and chlorophyll content in leaves varied depending on the AgNPs treatment and the cultivar analyzed. A significant effect of AgNPs on the genetic variation occurrence was found. A nearly two-fold higher share of polymorphic products, in both cultivars studied, was generated by RAPD markers than by SCoTs. To conclude, protocols using leaf explant treatment with AgNPs can be used as a novel breeding technique in chrysanthemum. However, the individual cultivars may differ in biochemical response, the efficiency of in vitro regeneration, genetic variation, and frequency of induced mutations in flowering plants.

Combined effects of vermicompost and vermicompost leachate on the early growth of Meloidogyne incognitastressed Withania somnifera (L.) Dunal.

Roots of Withania somnifera, an important medicinal herb, are prone to the infection of Meloidogyne incognita (a root parasitic nematode). The infection lowers the quality and quantity of plant material and poses a challenge in crop cultivation and obtaining desirable yield. In the present study, in vitro inhibitory activity of vermicompost leachate (Vcom-L) was assessed against % hatch and survival of M. incognita in a 96h assay. Then, Vcom-L was used as soil supplement in combination with vermicompost (Vcom) to evaluate their nematode inhibitory and stress alleviating effect in W. somnifera, in a pot experiment. Root galling intensity and growth performance of nematode-stressed W. somnifera raised from seeds pre-soaked in distilled water (DW), Vcom-L, vermicompost tea (Vcom-T) and different dilutions of Vcom-L were assessed. We observed 79% suppression of egg hatching and 89% juvenile (J2) mortality after 96h compared to control, at 100% concentration of Vcom-L. Significant reduction in gall formation with increase in growth parameters of seedlings was observed after combined application of Vcom (60% or 100%) + Vcom-L and was evident as enhancement in seedling biomass and contents of chlorophyll and protein. However, proline, total phenolics and malondialdehyde (MDA) content declined significantly in these combinations compared to the control (0% Vcom). Activity of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidise (APX), guaiacol peroxidise (GPX) and glutathione reductase (GR) declined with Vcom as well as Vcom + Vcom-L and corresponded with decline in the accumulation of reactive oxygen species in leaves. Further, 1:5 and 1:10 dilutions of Vcom-L in combination with Vcom (60%) proved beneficial in mitigating the nematode-induced stress in W. somnifera. Present results showed the potential of Vcom and Vcom-L in standardised combination as an effective strategy in controlling the pathogenicity of M. incognita in medicinal plants such as W. somnifera.

Phytoremediation of soil treated with metalliferous leachate from an abandoned industrial site by Alternanthera sessilis and Ipomoea aquatica: Metal extraction and biochemical responses

Metalliferous soil (MS) was collected from near an abandoned pulp and paper mill, and leachates were extracted in water to simulate natural water percolation. Metalliferous soil leachates (MSL) were added to the garden soil, and phytoremediation trials were carried out by Alternanthera sessilis and Ipomoea aquatica for 28-d in pot experiments. The aqueous leachates could extract 18–33% of the metals from the MS. The maximum accumulation of 38–43 μg Cd/g, 211–294 μg Pb/g, 199–218 μg Cr/g, 92–95 μg Ni/g, 422–511 μg Cu/g, 2366–3531 μg Zn/g, 6910–6105 μg Fe/g, and 4410–5576 μg Mn/g in the plants exceeded the respective toxic ranges, indicating their tolerance. Plants showed >50% removal efficiency for Pb, Cr, and Cu. For other metals, variable removal efficiency between 25 and 48% was also noted. The root morphology and X-ray microanalysis revealed Pb, Cr, and Fe deposits that influenced their uptake and possible interactions with other elements. The treated plants showed reduced chlorophylls, carotenoids, protein, and ascorbate, along with an increase in superoxide radical, hydrogen peroxide, and lipid peroxidation. A concomitant increase in the activities of all the vital antioxidant enzymes such as superoxide dismutase, catalase, ascorbate peroxidise, and guaiacol peroxidise helped to combat multi-metal stress in them. Overall, owing to their metal uptake efficiency, significant oxidative stress mitigation properties, rapid growth rate, and large biomass, A. sessilis, and I. aquatica can be recommended for use in the decontamination of multiple metals.

Mesorhizobium ciceri as biological tool for improving physiological, biochemical and antioxidant state of Cicer aritienum (L.) under fungicide stress

Fungicides among agrochemicals are consistently used in high throughput agricultural practices to protect plants from damaging impact of phytopathogens and hence to optimize crop production. However, the negative impact of fungicides on composition and functions of soil microbiota, plants and via food chain, on human health is a matter of grave concern. Considering such agrochemical threats, the present study was undertaken to know that how fungicide-tolerant symbiotic bacterium, Mesorhizobium ciceri affects the Cicer arietinum crop while growing in kitazin (KITZ) stressed soils under greenhouse conditions. Both in vitro and soil systems, KITZ imparted deleterious impacts on C. arietinum as a function of dose. The three-time more of normal rate of KITZ dose detrimentally but maximally reduced the germination efficiency, vigor index, dry matter production, symbiotic features, leaf pigments and seed attributes of C. arietinum. KITZ-induced morphological alterations in root tips, oxidative damage and cell death in root cells of C. arietinum were visible under scanning electron microscope (SEM). M. ciceri tolerated up to 2400 µg mL−1 of KITZ, synthesized considerable amounts of bioactive molecules including indole-3-acetic-acid (IAA), 1-aminocyclopropane 1-carboxylate (ACC) deaminase, siderophores, exopolysaccharides (EPS), hydrogen cyanide, ammonia, and solubilised inorganic phosphate even in fungicide-stressed media. Following application to soil, M. ciceri improved performance of C. arietinum and enhanced dry biomass production, yield, symbiosis and leaf pigments even in a fungicide-polluted environment. At 96 µg KITZ kg−1 soil, M. ciceri maximally and significantly (p ≤ 0.05) augmented the length of plants by 41%, total dry matter by 18%, carotenoid content by 9%, LHb content by 21%, root N by 9%, shoot P by 11% and pod yield by 15% over control plants. Additionally, the nodule bacterium M. ciceri efficiently colonized the plant rhizosphere/rhizoplane and considerably decreased the levels of stressor molecules (proline and malondialdehyde) and antioxidant defence enzymes viz. ascorbate peroxidise (APX), guaiacol peroxidise (GPX), catalase (CAT) and peroxidises (POD) of C. arietinum plants when inoculated in soil. The symbiotic strain effectively colonized the plant rhizosphere/rhizoplane. Conclusively, the ability to endure higher fungicide concentrations, capacity to secrete plant growth modulators even under fungicide pressure, and inherent features to lower the level of proline and plant defence enzymes makes this M. ciceri as a superb choice for augmenting the safe production of C. arietinum even under fungicide-contaminated soils.

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Salinity stress inhibits plant growth by affecting morphological, photosynthesis, antioxidant phenomena, and nitrogen metabolism, among other physiological and biochemical processes. In this study, the effects of pre-soaking Wheat and Mung grains in aqueous extract of Cissus quadrangularis on growth, and antioxidant activity of salt-treated plants, were investigated. The pre-soaking of grains in extract demonstrated a significant enhancement in growth parameters. The activity of superoxide dismutase (SOD), guaiacol peroxidise (GPOX), and ascorbate peroxidase (APX), catalase (CAT) increased with increasing the concentration of C. quadrangularis extract up to 3%w/v while decreasing when at a higher concentration of 10%w/v. The estimation of bioactive compound Proline also observes higher concentrations at 3%w/v under treatment with different salt stress. Therefore, the study suggested that seed priming with plant extract is an effective technique to improve the growth of Wheat and Mung seedlings under salt stress conditions.

Antioxidant system status of cucumber plants under pesticides treatment

A plants’ physiology maybe affected by various pesticides through the activation or inactivation of different biochemical pathways in target and non-target plants. In response to pesticides as xenobiotics, plants activate their antioxidant defense systems through both enzymatic and non-enzymatic pathways. In this study, two of the most common pesticides used to control cucumber whiteflies, imidacloprid and dichlorvos were sprayed on cucumber seedlings. Treatment with both pesticides significantly increased the activity of superoxide dismutase, catalase, ascorbate peroxidase, guaiacol peroxide, and phenylalanine ammonia-lyase. Moreover, total protein, proline, total soluble carbohydrates, and total phenolic content showed a significant elevation in response to the treatment with both pesticides compared to the control. The effects of the separate use of pesticides resulted in variation in the peak day of physiological changes in treated plants. Further experiments showed that pesticide treatment leads to a significant decrease in polyphenol oxidase activity, but no significant changes in contents of hydrogen peroxide, malondialdehyde, and electrolyte leakage index were found. Our results suggest that imidacloprid and dichlorvos had profound effects on the physiological status of cucumber plants at recommended rates. Our data also showed that the responses were similar between the two pesticides with differences in response times following treatment.

Low temperature induced oxidative stress tolerance in oats (Avena sativa L.) genotypes

Chilling tolerance adaptation in plant cell can be correlated with efficiency of antioxidant defence system, antioxidants and osmoprotectants. In this study, such responses were comparatively studied in four high yielding oats genotypes (OL-9, OL-10, OL-125, Kent) under control (25 °C) and chilling stress (5 °C) conditions. Cold temperature upregulated the activites of catalase, guaiacol peroxide, ascorbate peroxidase (APX), glutathione reductase in root and shoot of all four genotypes. The SOD enzyme activity was decreased in both organs by 32% with chilling stress. Chilling stress increased redox potential of plant cell significantly by increasing the level of ascorbate and glutathione in order to cope up the reactive oxygen species The concentration of proline, total phenol, total sugar, H2O2, soluble protein and free amino acids was increased with imposition of cold stress in both roots and shoots though a decline in MDA content was observed. The observed biochemical diversity revealed that catalase, APX, glutathione and sugars appeared to have greater role in conferring chilling tolerance in oats genotypes as indicated by their greater variations with cold stress.

BIOCHEMICAL AND PHYSIOLOGICAL CHANGES OF CALLUS GROWTH AND LYCOPENE PIGMENT PRODUCTION FROM TOMATO (Lycopersicon esculentum Mill.) UNDER DROUGHT STRESS

This experiment was conducted in faculty of Science labs, Kufa University, carried out during 2015 to applied methods for extraction, purification and Quantitative of Lycopene red pigments, from callus tissue and tomato fruits mother plant (Lycopersicon esculentum Mill).This study include of three parts, Firstly; Tomato seeds(Supper queen) hybrid were germinated in free MS medium and callus induction from shoot tip (3cmpieces) by using MS medium supplemented with Dichlorophenoxiactic acid (2,4-D) at different concentration (0.5,1, 1.5mg/l)with benzyl adenine (BA) at concentration of (0.3 mg/l). Secondly; identically callus fresh weight re-cultured in the same MS medium supplemented with high molecular weight polyethylene glycol (PEG) was used as selective agent at level of (5,10,15 and 25%). Thirdly; comparisons study were made between in vitro and in vivo grown plant. Powder of control lycopene used as standard solution. The content of lycopene was done by using high performance liquid chromatography (HPLC), and compare of the quantitatively of lycopene with these content in fruits of mother plant, and callus tissue. Also, include alcohol extraction of Lycopene from tomato fruit by using acetone and hexane mixture. The result showed significant increased (P< 0.05) of lycopene production and the superiority of lycopene content in callus than the content in fruits of mother plant. Antioxidant enzymes activity like Catalase (CAT),Guaiacol peroxidise (POX) and Superoxide dismutase(SOD) were high in callus under drought stress than in fruit of mother plant. However, Proline and total sugar content were at higher levels in callus under drought stress than in fruit of mother plant.

Advantages of an Electrochemical Method Compared to the Spectrophotometric Kinetic Study of Peroxidase Inhibition by Boroxine Derivative.

In this study, boroxine derivative (K2[B3O3F4OH]) was tested as an inhibitor of horseradish peroxidase (HRP) by spectrophotometric and electrochemical methods. The activity of horseradish peroxidase was first studied under steady-state kinetic conditions by a spectrophotometric method which required the use of guaiacol as a second substrate to measure guaiacol peroxidation. The results of this method have shown that, by changing the concentration of guaiacol as the literature suggests, a different type of inhibition is observed than when changing the concentration of hydrogen peroxide as the substrate. This suggests that guaiacol interferes with the reaction in some way. The electrochemical method involves direct electron transfer of HRP immobilized in Nafion nanocomposite films on a glassy carbon (GC) electrode, creating a sensor with an electro-catalytic response to the reduction of hydrogen peroxide. The electrochemical method simplifies kinetic assays by removing the requirement of reducing substrates.

Biochemical Characterization of Compatible Plant Virus Interaction: A Case Study with Bunchy Top Virus-Banana Host-Pathosystem

Environmental stresses of both biotic and abiotic nature produce characteristic changes in physiology and metabolic processes of higher plants (Miteva et al., 2005). Among these stresses, infection by the pathogens causes substantial alterations of biochemical changes leading to harmful effects on plant health. Banana cultivation is subjected to many natural calamities including pest and pathogen attacks which constitute the major production problem. Among plant diseases, viral diseases may cause considerable loss on production by retarding plant growth and reducing yield. Four viral diseases viz., Banana Bunchy Top Disease (BBTD) caused by Banana bunchy top virus (BBTV), Bract Mosaic Disease (BBrMD) caused by Banana bract mosaic virus (BBrMV), Banana Streak Disease (BSD) caused by different species of Banana streak virus (BSV) and banana mosaic or infectious chlorosis caused by Cucumber mosaic virus (CMV) occur in most of the banana growing regions of the world. Among banana viral diseases, Banana Bunchy Top Disease (BBTD) is one of the most destructive viral diseases in Tropical Asia, Pacific Indian Oceania (PIO) regions and Africa. Grand Nain, Virupakshi (Hill banana), Robusta, Nendran, Rasthali, Poovan, Ney Poovan, Monthan and Red Banana are severely affected by BBTD. There is no resistance gene source available in germplasm of bananas and plantains (Shekhawat et al., 2012). The BBTV affected plants show intermittent dark green dots, dash, streaks of variable length on leaf sheath, midrib, leaf veins and petioles of infected plants. Leaves produced are progressively shorter, brittle in texture, narrow and gives the appearance of bunchyness at the top leading to 100% yield loss (FAO., 2009). Plants have evolved various pre-existing physical and chemical barriers, as well as inducible defense responses that interfere with pathogen colonization (Jones and Dangl, 2006; Zhao et al., 2008; Vanitha et al., 2009). However, this requires comprehensive studies and understanding of the adaptive mechanisms and responses to BBTV infection in banana. Because viruses cannot be cultured in vitro, our knowledge about their interactions with host and changes on physiology, biochemistry and molecular biology of the host is limited. Moreover, a comprehensive report regarding biochemical alterations in banana plants infected by BBTV is still not clear. Therefore, the present investigation was conducted to find the quantitative estimations of physiological and biochemical parameters such as protein, pigment and carbohydrate contents, phenolic compounds, polyphenol oxidase (PPO), peroxidase (POX), catalase (CAT), ascorbate peroxidise (APX), guaiacol peroxidise (GPX) and superoxide dismutase (SOD) activities, indicating their role in BBTV inoculated and non-inoculated plants of Virupakshi (hill banana), a unique flavoured elite dessert banana cultivar and Grand Nain, which belongs to a Cavendish sub group occupying approximately 50% of area in the world.

Hepatic dysfunction induced by 7, 12-dimethylbenz(α)anthracene and its obviation with erucin using enzymatic and histological changes as indicators.

The toxicity induced by 7, 12-dimethylbenz(α)anthracene (DMBA) has been widely delineated by a number of researchers. This potent chemical damages many internal organs including liver, by inducing the production of reactive oxygen species, DNA-adduct formation and affecting the activities of phase I, II, antioxidant and serum enzymes. Glucosinolate hydrolytic products like isothiocyanates (ITCs) are well known for inhibiting the DNA-adduct formation and modulating phase I, II enzymes. Sulforaphane is ITC, currently under phase trials, is readily metabolized and inter-converted into erucin upon ingestion. We isolated erucin from Eruca sativa (Mill.) Thell. evaluated its hepatoprotective role in DMBA induced toxicity in male wistar rats. The rats were subjected to hepatic damage by five day regular intraperitoneal doses of DMBA. At the end of the protocol, the rats were euthanized, their blood was collected and livers were processed. The liver homogenate was analyzed for phase I (NADPH-cytochrome P450 reductase, NADH-cytochrome b5 reductase, cytochrome P450, cytochrome P420 and cytochrome b5), phase II (DT diaphorase, glutathione-S-transferase and γ-glutamyl transpeptidase) and antioxidant enzymes (superoxide dismutase, catalase, guaiacol peroxidise, ascorbate peroxidise, glutathione reductase and lactate dehydrogenase). The level of thiobarbituric acid reactive substances, lipid hydroperoxides, conjugated dienes and reduced glutathione in the liver homogenate was also analyzed. The serum was also analyzed for markers indicating hepatic damage (alkaline phosphatase, serum glutamic oxaloacetic transaminase, serum glutamic pyruvic transaminase, direct bilirubin and total bilirubin). Erucin provided significant protection against DMBA induced damage by modulating the phase I, II and antioxidant enzymes. The histological evaluation of liver tissue was also conducted, which showed the hepatoprotective role of erucin.

Sensitivity of Allium cepa and Vicia faba towards cadmium toxicity

Sensitivity of common onion (Allium cepa L.) and faba bean (Vicia faba L.) to cadmium (Cd) stress was investigated using genotoxicity endpoints. Simultaneously, the antioxidative stress enzymes (guaiacol peroxidise and catalase) and lipid peroxidation [malonaldehyde (MDA) content] were investigated in the plants exposed to Cd in solution. The endpoints screened for genotoxicity included chromosomal aberrations, micronuclei frequency and mitotic frequency. Additionally comet assay was performed for DNA fragmentation. Evan’s blue uptake by the root meristems as a cell death parameter served as indicator of cytotoxicity. The results indicated that exposure to Cd induced dose-dependent increase in chromosomal aberrations, DNA fragmentation and micronucleus frequency in both A.cepa and V. faba. The enzymes guaiacol peroxidase (GPX) and catalase (CAT) activities increased in both the plants and were higher in V. faba. A positive correlation between the activity of GPX and CAT and MDA content was recorded at all concentrations of Cd. Regarding sensitivity, our results showed that V. faba is more sensitive plant than A. cepa towards Cd –induced toxicity. Higher genotoxicity level correlated to the increased level of oxidative stress in root tissues. This was likely to be an important cause of Vicia plant to be less tolerant than Allium.

Influence of EDTA and citric acid on lead-induced oxidative stress to Vicia faba roots

In spite of substantial advancement in recent past, the role of metal speciation in assessing biogeochemical behaviour of Pb is still topical. Organic ligands are capable to modify Pb speciation in nutrient/soil solution and in turn its soil–plant transfer and toxicity. In this sense, the main objective of this study was to evaluate the effect of organic ligands on Pb-induced oxidative stress to Vicia faba roots. V. faba seedlings grown to controlled hydroponic system were treated with 5 μM Pb as lead nitrate in the presence and absence of organic ligands viz ethylenediaminetetraacetic acid (EDTA) and citric acid (CA) for 1, 4, 8, 12, and 24 h. The chemical speciation of Pb (percent free and chelated Pb) in nutrient solution in the presence and absence of organic ligands was calculated using Visual Minteq speciation model. The effect of chemical speciation on Pb-induced oxidative stress to V. faba roots was investigated using plant enzymatic antioxidative system [superoxide dismutases (SOD), guaiacol peroxidise (GPX), ascorbate peroxidase (APX), glutathione reductase (GR), and catalase (CAT)]. The antioxidant enzymes activities were determined using ultraviolet spectrophotometer. The activities of SOD, GPX, APX, and GR significantly increased whereas that of CAT decreased in V. faba roots under Pb alone treatment. Lead-induced increase/decrease in antioxidant enzymes activities was not linear but varies with treatment exposure time. EDTA dose dependently inhibited Pb-induced changes in antioxidant enzymes activities. However, CA did not cause any significant change in Pb-induced variation in antioxidant enzymes activities, but delayed or slightly reduced the Pb effect. The present study suggested that physiological responses of V. faba roots to Pb toxicity vary with applied Pb form and duration of exposure. EDTA can inhibit Pb-induced toxicity to V. faba seedlings by forming stable Pb-EDTA complexes due to its high binding strength for Pb. However, CA had no effect on Pb-induced toxicity to V. faba roots due to weak complexation with Pb.

Response of antioxidant defences to Zn stress in three duckweed species

In the plants, Lemna gibba, Lemna minor and Spirodela polyrrhiza L., the effect of different concentrations of zinc (0.01, 0.05, 0.1, 0.5 and 1.5mgL−1 Zn) applied for four day was assessed by measuring changes in the chlorophyll, protein, malondialdehyde (MDA), catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX) and guiacolperoxidase (GPX) activity of the plants. According to results, Zn contents in plants increased with increasing Zn supply levels. The level of photosynthetic pigments and soluble proteins reduced only upon exposure to high Zn concentrations. At the same time, the level of malondialdehyde (MDA) increased with increasing Zn concentration. These results suggested an alleviation of stress that was possibly the result of antioxidants such as catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX) as well as guaiacol peroxidise (GPOX), which increased linearly with increasing Zn levels. Cellular antioxidant levels showed an increase suggesting a defensive mechanism to preserve against oxidative stress given rise to by Zn. Besides, the proline amount in L. gibba, L. minor and S. polyrrhiza increased with increasing zinc levels. These conclusions proposed that L. gibba, L. minor and S. polyrrhiza are supplied with an efficient antioxidant mechanism against Zn-induced oxidative stress which saves the plant's photosynthetic machinery from damage.It is concluded that higher zinc levels cause oxidative stress in L. gibba, L. minor and S. polyrrhiza cells and may reason membrane damage through production of ROS and interferes with chlorophyll metabolism.

Inhibition of peroxidase-catalyzed iodination by thioamides: experimental and theoretical study of the antithyroid activity of thioamides

The reaction of di-iodine with N-methyl-2-mercapto-benzothiazole (NMBZT) in the presence of ferric tetra-phenyl-porphyrin chloride (FeTPPCl) in 6 ∶ 3 ∶ 1 (I2 ∶ thioamide ∶ FeTPPCl) molar ratio yields a mixture of products consisting of the iodonium {[(NMBZT)2I]+·[(I7)−]}n salt, 1, and the FeTPPCl complex, 2. The compounds were characterized by X-ray diffraction analysis. The crystal structure of 1 was identical to the one already published, while of compound 2 at 294(1) K re-evaluates previous work on it. The inhibition activity of the thioamide ligands (N-methyl-2-mercapto-benzothiazole (NMBZT), 2-mercapto-benzothiazole (MBZT), 5-chloro-2-mercapto benzothiazole (CMBZT), 2-mercaptothiazolidine (MTZT), 2-mercaptopyridine (PySH), thiourea (TU), 1,3-bis(3-pyridyl-methyl)-2-thiourea (PyTU), 2-mercapto-3,4,5,6-tetrahydropyrimidine (THP), 2-mercaptopyrimidine (PmSH), 6-propyl-2-thiouracil (PTU), 6-methyl-2-thiouracil (MTU), di-thiouracil-2,4 (DTUC), 2-mercapto-4-methyl-pyrimidine hydro chloride (MPmCl), methimazole (MMI), 2-mercapto-benzimidazole (BZIM), 5-nitro-2-mercapto-benzimidazole (NiMBZIM), 5-methyl-2-mercapto-benzimidazole (MBZIM), 2-hydroxy-pyrimidine (PmOH), 2-hydroxypyridine (PyOH)) against the catalytic oxidation of iodides by H2O2 in the presence of FeTPPCl (a model of the active site of Thyroid Peroxidase (TPO)) was measured as a result of the yield of I3− resulting from the oxidation of I− and was also evaluated theoretically using electronic structure calculation methods (DFT). The compounds exhibiting high and intermediate degree of inhibition (between 27% and 17%) are MBZT, MMI, PySH, NMBZT, PmSH, MBZIM, NiBZIM and MTZT. The kinetic study of inhibition of lactoperoxidase (LPO) (a model of TPO) is based on the assessment of LPO activity in the presence of its inhibitors—the thioamide compounds. LPO activity can be assayed by measuring guaiacol (gua) peroxidation to tetraguaiacol in the presence of H2O2. The results illustrated that the lowest IC50 values (<10 μM) required for the LPO inhibition were exhibited by DTUC, NiMBZIM, MBZT, PySH thioamides. Low concentrations between 10 and 30 μM are obtained in the case of CMBZT, BZIM, MPmCl, PmSH, MBZIM, and MMI. DFT calculations of the geometric and energetic profiles threw light on the mechanism of the inhibition process by the thioamide compounds scrutinizing all crucial reaction steps and are in agreement with the experimental results.

Response of Oryzacystatin I Transformed Tobacco Plants to Drought, Heat and Light Stress

AbstractTransformed tobacco plants expressing a rice cysteine proteinase inhibitor (OC‐I) and non‐transformed plants were grown in a controlled environment and subjected to various stresses. Two‐month‐old transformed and non‐transformed plants were exposed for 5 days to drought conditions by withholding watering. High temperature (40 °C) was applied additionally at day 6th for 5 h either individually or in combination with drought. All stress treatments were applied under low (150 μmol m−2 s−1 PPFD) and high light intensity (HL) of 1000 μmol m−2 s−1 PPFD to determine if OC‐I expression might provide protection under combination of stresses usually existing in nature. Drought stress led to diminution in leaf relative water content, photosynthesis inhibition, decrease in chlorophyll content and accumulation of malondialdehyde and proline. Heat stress alone did not affect the plants significantly, but intensified the effect of drought stress. HL intensity further increased the proline content. OC‐I transformed plants grown under low light intensity had significantly higher total superoxide dismutase and guaiacol peroxidase activities as well as their isoforms than non‐transformed control plants under non‐stress and stress conditions. Catalase activity was not highly affected by OC‐I expression. Results indicate that OC‐I expression in tobacco plants provides protection of the antioxidative enzymes superoxide dismutase and guaiacol peroxidise under both non‐stress and stress conditions.

Metalliferous and non-metalliferous populations of Viola tricolor represent similar mode of antioxidative response

Heavy metal-contaminated sites are excellent areas to examine the antioxidative machinery responsible for physiological adaptations of many plant species. Superoxide dismutase (SOD), guaiacol peroxide (GPX), ascorbate peroxide (APX), catalase (CAT) activity and hydrogen peroxide (H(2)O(2)) content were analyzed in leaves and roots of Viola tricolor (Viola) from contaminated soils ('Bukowno', 'Saturn', 'Warpie' heaps), and non-contaminated soil ('Zakopane meadow') to examine the level of oxidative stress and antioxidative response. In leaves, six isoforms of SOD were recognized. Roots possessed two additional bands, named manganese superoxide dismutase (MnSOD)-like form (MnSODI) and Cu/ZnSOD-like form (Cu/ZnSODIV). The H(2)O(2) content in leaves ranged from 554 to 5 098 micromol H(2)O(2)/gf.w. and was negatively correlated with CAT activity. The non-contaminated population was characterized by the lowest CAT activity combined with the highest H(2)O(2) concentration. Two isoforms of CAT, CAT-1 and CAT-2, were recognized in leaves of plants from non-contaminated and contaminated sites, respectively. In roots of individuals from two heaps ('Warpie' and 'Saturn'), two distinct bands for each CAT isoform were observed. A slower migrating band may be an aggregate, exhibiting CAT and MnSODs activities. Both peroxidases (APX and GPX) presented the same pattern of activity, depending on the organ, indicating that in leaves and roots APX and GPX were regulated in parallel. Differences in enzyme activities and H(2)O(2) content between plants from different contaminated sites were statistically significant, but were tightly maintained at a very similar level. Prolonged and permanent heavy metal stress evoked a very similar mode of antioxidative response in specimens of analyzed metalliferous populations not causing measurable oxidative stress. Thus, our results clearly indicate that V. tricolor is a taxon well adapted to heavy metal-contaminated soils, and that differences in enzyme activities and H(2)O(2) content result from adjustment of plants to a variety of conditions.

Replacement of the Distal Glycine 139 Transforms Human Heme Oxygenase-1 into a Peroxidase

The human heme oxygenase-1 crystal structure suggests that Gly-139 and Gly-143 interact directly with iron-bound ligands. We have mutated Gly-139 to an alanine, leucine, phenylalanine, tryptophan, histidine, or aspartate, and Gly-143 to a leucine, lysine, histidine, or aspartate. All of these mutants bind heme, but absorption and resonance Raman spectroscopy indicate that the water coordinated to the iron atom is lost in several of the Gly-139 mutants, giving rise to mixtures of hexacoordinate and pentacoordinate ligation states. The active site perturbation is greatest when large amino acid side chains are introduced. Of the Gly-139 mutants investigated, only G139A catalyzes the NADPH-cytochrome P450 reductase-dependent oxidation of heme to biliverdin, but most of them exhibit a new H(2)O(2)-dependent guaiacol peroxidation activity. The Gly-143 mutants, all of which have lost the water ligand, have no heme oxygenase or peroxidase activity. The results establish the importance of Gly-139 and Gly-143 in maintaining the appropriate environment for the heme oxygenase reaction and show that Gly-139 mutations disrupt this environment, probably by displacing the distal helix, converting heme oxygenase into a peroxidase. The principal role of the heme oxygenase active site may be to suppress the ferryl species formation responsible for peroxidase activity.