Effect of different forms of selenium on the plant–soil–earthworm system

Selenium (Se) is an essential micronutrient for humans, animals, and certain lower plants, but at higher concentrations Se becomes toxic to organisms. The boundary between the Se beneficial effect and its toxicity is narrow and depends on its chemical form, applied concentration, and other environmentally regulating factors. Due to the potential risk of toxicity in higher concentration, the aim of this study was to estimate the impact of increased concentrations of different forms of Se on the response of the wheat–soil–earthworm system. Soil, earthworms, and wheat grains were exposed to the Se in form of selenite and selenate in concentrations of 0.01, 0.1, and 1 mg kg⁻¹. As an indicator of oxidative stress in wheat, lipid peroxidation levels (LPO) and total H₂O₂ content were determined, while antioxidative response was determined by catalase (CAT), glutathione peroxidase (GPX), and glutathione reductase (GR) activities. The biomarker responses in earthworms were determined by acetylcholinesterase (AChE), carboxylesterase (CES), and antioxidative enzymes (CAT and glutathione S‐transferase) activities. Selenite and selenate increased Se content in the wheat and earthworms, while selenate application was more efficient, indicating higher bioaccumulation of this Se form. Both Se forms did not cause significant changes in the LPO level and H₂O₂ content, while GPX activities were elevated in all treatments, suggesting that oxidative stress was not induced in wheat. In earthworms, Se significantly reduced activities of AChE and CAT at some concentrations, while CES activity was increased at all concentrations applied. This study showed significant impact of Se on measured biochemical responses in wheat and earthworms, indicating the disruption of homeostasis. Obtained results can serve as basis for further studies on Se effects and will help in including different aspects necessary for understanding of Se impact on different components of soil ecosystems.     

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

Purpose

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.

Materials and methods

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.

Results and discussion

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.

Conclusions

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.     

Study of cadmium (Cd)-induced oxidative stress in Eisenia fetida based on mathematical modelling

As a sensitive biological indicator, earthworms are widely used to monitor various pollutants of soil and provide an early warning for soil pollution. However, because many indices are involved in the exposure-induced oxidative stress response, practical applications of these indices are quite inconvenient. Therefore, it is appropriate to investigate the key monitoring index for use in early warning and pollution monitoring. Using Eisenia fetida as an experimental model in an indoor simulation experiment, the mathematical modelling of the effect on oxidative stress in earthworms under cadmium (Cd) stress was studied. The test lasted 40 d, with the removal of one earthworm every 10 d. The Cd²⁺ concentration gradient was set as 0, 1, 10, 20, 100, 200, 400, and 800 mg kg^-1 dry weight. The earthworms were divided into two sections from the clitellum for the determination of total protein (TP) and peroxidase (POD), superoxide dismutase (SOD), glutathione-S-transferase (GST), glutathione peroxidase (GPX), catalase (CAT), malondialdehyde (MDA), and acetylcholinesterase (AChE) activities. Results showed that POD was the key index of oxidative stress in head tissues after 10 d of exposure, TP was the key index at 20 d, and POD became the key index again at 30 and 40 d. By contrast, in tail tissues, MDA and SOD were the key indices at an exposure time of 10 d, GPX at 20 d, CAT and TP at 30 d, and POD and MDA at 40 d. These results contribute to establishing a scientific method for ecotoxicological diagnosis and revealing the mechanism of soil Cd toxicity.     

Study of oxidative stress cadmium(Cd)-induced in Eisenia fetida based on mathematical modeling

As a sensitive biological indicator, earthworms are widely used to monitor various pollutants of soil and provide an early warning for soil pollution.However, because many indices are involved in the exposure-induced oxidative stress response, practical applications of these indices are quite inconvenient.Therefore, it is appropriate to investigate the key monitoring index for use in early warning and pollution monitoring. Using Eisenia fetida as an experimental model in an indoor simulation experiment, the mathematical modelling of the effect on oxidative stress in earthworms under cadmium(Cd) stress was studied.The test lasted 40 d, with the removal of one earthworm every 10 d. The Cd~(2+)concentration gradient was set as 0, 1, 10, 20, 100, 200, 400, and 800 mg kg~(-1) dry weight. The earthworms were divided into two sections from the clitellum for the determination of total protein(TP) and peroxidase(POD), superoxide dismutase(SOD), glutathione-S-transferase(GST), glutathione peroxidase(GPX), catalase(CAT), malondialdehyde(MDA), and acetylcholinesterase(AChE)activities. Results showed that POD was the key index of oxidative stress in head tissues after 10 d of exposure, TP was the key index at 20 d, and POD became the key index again at 30 and 40 d. By contrast, in tail tissues, MDA and SOD were the key indices at an exposure time of 10 d, GPX at 20 d, CAT and TP at 30 d, and POD and MDA at 40 d. These results contribute to establishing a scientific method for ecotoxicological diagnosis and revealing the mechanism of soil Cd toxicity.     

Alteration of Phytotoxicity and Oxidant Stress Potential by Metal Oxide Nanoparticles in Cucumis sativus

This study was carried out to examine the phytotoxicity and oxidant stress by CuO and ZnO nanoparticles (NPs) in Cumumis sativus and the characterization of CuO and ZnO NP suspensions. We estimated the bioaccumulation of CuO and ZnO NP in plant, reactive oxygen species enzyme (superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD)) activities in plant tissue of root, and observed CuO and ZnO NPs with transmission electron microscopy. We found that the seedling biomass significantly decreased to 75% and 35% of that of control at 1,000?mg/L of CuO and ZnO NPs, respectively. The bioavailability and oxidant stress potential of plants exposed to metal oxide particles were dependent in the size, concentration, and species of the NPs. The median inhibition concentrations of CuO and ZnO NPs were 376 and 215?mg/L, respectively. In transmission electron microscopy, CuO and ZnO NPs greatly adhered to the root cell wall, and NPs were observed in the root cells. Another finding indicated that both CuO and ZnO NPs caused statistically significant increase in SOD, CAT, and POD activities and significant increase at 100?mg/L concentration levels. These results indicated that NPs alter both phytotoxicity and oxidative stress in plant assays. We further suggest that the oxidative stress markers appear to be a good predator of potential future toxicity of nanoparticles.     

Comparative Selenium Toxicity to Laboratory-Reared and Field-Collected Hyalella azteca (Amphipoda, Hyalellidae)

Selenium (Se) contamination of aquatic habitats is a global environmental issue. Although organic forms of Se are thought to represent the most bioavailable forms of Se, elevated concentrations of inorganic Se can cause toxicity in aquatic organisms such as benthic invertebrates. To assess the potential role of Se in mortalities observed during previous in situ invertebrate exposures, laboratory experiments on toxicity of inorganic Se (selenate) to Hyalella azteca were performed. Both a laboratory-reared and a field-collected H. azteca population were exposed to Se concentrations ranging from near 0 (control) to 21.79?mg/L, and survival of exposed individuals was monitored over 10?days. In the laboratory-reared H. azteca, significant changes in mortality pattern and reductions in mean survival time (MST) were noted in the test groups exposed to ??0.164?mg/L Se. In the field-collected animals however, significant changes in mortality pattern and reductions in MST were measured in H. azteca exposed to ??1.43?mg/L Se. The 10-day LC50s were 0.086 and 0.574?mg Se/L for the laboratory and field-collected H. azteca populations, respectively. The laboratory-reared group thus was about one order of magnitude more sensitive to Se exposure than the field-collected amphipods. Our results suggest that Se toxicity was likely not a major contributor to amphipod mortalities observed in earlier field studies. Furthermore, population-specific tolerances of the test organisms may need to be considered when extrapolating laboratory-generated data to field situations.     

Variation of Antioxidant Activity in Dreissena polymorpha Specimens Exposed to 2,2′,4,4′,5,6′-Hexa BDE (BDE-154)

We evaluated the imbalance of the oxidative status in zebra mussel (Dreissena polymorpha) specimens exposed for 96?h to environmentally relevant concentrations (0.1, 0.5, and 1???g/L) of the 2,2??,4,4??,5,6??-hexa BDE (BDE-154). The activities of three antioxidant enzymes, catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and the phase II detoxifying enzyme glutathione S-transferase (GST), were measured in the cytosolic fraction from a pool of zebra mussels. Significant variations in the activity of each single enzyme were noticed at each treatment, indicating that exposure to BDE-154 was able to impair the oxidative status of treated bivalves through the increase of reactive oxygen species. In detail, SOD and GPx were significantly induced, while CAT and GST were depressed with respect to the baseline levels. These data have confirmed that the raise of oxidative stress is the main cause of the BDE-154-induced genetic damage observed in a previous study on the zebra mussel.     

Effects of a Simulated Agricultural Runoff Event on Sediment Toxicity in a Managed Backwater Wetland

We examined the effects of an amended mixture of three pesticides, atrazine (72.7?g), S-metolachlor (54.5?g), and permethrin (both cis and trans isomers; 11.4?g), on 10-day sediment toxicity to Hyalella azteca in a managed natural backwater wetland after a simulated agricultural runoff event. Sediment samples were collected at 10, 40, 100, 300, and 500?m from inflow 13?days prior to amendment and 1, 5, 12, 22, and 36?days post-amendment. Background pesticide concentrations ranged from <1 to 977, <1 to 119, and <1 to 2???g?kg^?1, for atrazine, S-metolachlor, and permethrin, respectively. Average post-amendment atrazine and S-metolachlor were 2,915?C3,927 and 3?C20???g?kg^?1, respectively at 10?C40?m and 538?C872 and <1???g?kg^?1, respectively at 300?C500?m. Average post-amendment permethrin was 65?C200???g?kg^?1 at 10?C40?m and 1?C10???g?kg^?1 at 300?C500?m. H. azteca 10-day survival varied spatially and temporally up to 100?m from inflow. Animal growth, independent of survival, was reduced 40 and 100?m from inflow on day?36, showing continued sediment toxicity of up to 100?m from inflow more than 1?month after amendment. Animal survival and growth were unaffected at 300 and 500?m from inflow throughout the study period. Correlations of pesticide concentrations and H. azteca responses indicated that observed sediment toxicity was primarily from permethrin with potential additional synergistic toxicity from atrazine and methyl parathion. Study results indicate that natural backwater wetlands can be managed to ameliorate pesticide mixture 10-day sediment toxicity to H. azteca within 300?m of inflow and smaller wetlands (??100?m) may require several months of effluent retention to mitigate effects.     

Kinetics of Zinc Uptake and Anatomy of Roots and Leaves of Coffee Trees as Affected by Zinc Nutrition

Abstract

The influence of silicon (Si) (2.5 mM), sodium chloride (NaCl) (100 mM), and Si (2.5 mM) + NaCl (97.5 mM) supply on chlorophyll content, chlorophyll fluorescence, the concentration of malondialdehyde (MDA), H₂O₂ level, and activities of superoxide dismutase (SOD; E.C.1.15.1.1.), ascorbate peroxidase (APx; E.C.1.11.1.11.), catalase (CAT; E.C.1.11.1.6.), guaiacol peroxidase (G-POD; E.C.1.11.1.7.) enzymes, and protein content were studied in tomato (Lycopersicon esculentum Mill c.v.) leaves over 10-day and 27-day periods. The results indicated that silicon partially offset the negative impacts of NaCl stress with increased the tolerance of tomato plants to NaCl salinity by raising SOD and CAT activities, chlorophyll content, and photochemical efficiency of PSII. Salt stress decreased SOD and CAT activities and soluble protein content in the leaves. However, addition of silicon to the nutrient solution enhanced SOD and CAT activities and protein content in tomato leaves under salt stress. In contrast, salt stress slightly promoted APx activity and considerably increased H₂O₂ level and MDA concentration and Si addition slightly decreased APx activity and significantly reduced H₂O₂ level and MDA concentration in the leaves of salt-treated plants. G-POD activity was slightly decreased by addition of salt and Si. Enhanced activities of SOD and CAT by Si addition may protect the plant tissues from oxidative damage induced by salt, thus mitigating salt toxicity and improving the growth of tomato plants. These results confirm that the scavenging system forms the primary defense line in protecting oxidative damage under stress in crop plants.     

Effect of Boron on Antioxidant Response of Two Lentil (Lens culinaris) Cultivars

Boron (B) is an essential micronutrient for plants through paticipating key reactions such as reproduction, development, and regeneration. Similar to its deficiency, its over-concentations possess toxic effects on plant growth. In this work, possible boron toxicity was researched through evaluating alaterations in antioxidant enzymes, oxidative stress biomarkers, and chlorophyll contents for two types of lentil species as red (native) and green (winter flake 11) lentil (Lens culinaris L.cv) cultivars, which are indigenous to Turkey. Ten days old seedling lentil plants were subjected to low as 0.5, 1.0 mM and high 2.0 and 5.0 mM boric acid treatments for 7 days. B worked as a growth-promoting nutrient for 0.5, 1.0, and 2.0 mM concentration by enhancing length and weight of both shoot and root tissues, while it started showed its suppression effect on these tissues at 5-mM cocentration, which were obtained more dramatic for green lentil in comparison to red lentil. In contrast to this, oxidative stress markers such as MDA, H₂O₂, and proline concentrations showed increasing trend for 0.5, 1.0, 2.0, and 5.0 mM B treatment, accompanied with a change in photosynthetic pigment concentrations (p < 0.01). MDA in red lentil shoot control was 30,3871 (μmol/gFW) and it was significantly increased to 36,5806 and 51,7414 by the 2.0 and 5.0 B rates, respectively. However, enzymes in anti-oxidation metabolism include superoxide dismutase (SOD), guaiacol peroxidase (GPX), lipoxygenase (LOX), glutathione peroxidase (GSH-Px) activities were obtained higher in high-B-treated groups, while decreased and stable activities were obtained for catalase (CAT) and ascorbate peroxidase (APX) enzymes. CAT and APX activities were higher than those were obtained for 2.0 and 5.0 mM B treatments in both root and shoot tissues. The lentil species manipulated their metabolism to suppress B-stress, and enhanced growth in shoot and root tissues up to 5-mM B stress even though oxidative stress markers showed increasing trend from low B concentrations, 1.0 mM. Therefore, B stress can be claimed as “doubled edge sword” for these lentil species.

Abbreviations

AOS, active oxygen species; APX, ascorbate peroxidase; CAT, catalase; DAB, diamino-benzidine tetrahydrochloride; DMSO, dimethyl sulfoxide DW, dry weight; EDTA, ethylenediamine-N,N,N₀,N₀-tetraacetic acid; FW, fresh weight GPX, guaiacol peroxidase; GSH-P_x, glutathione peroxidase; LOX, lipoxygenase; MDA, malondialdehyde; NBT, nitroblue tetrazolium; PEG, polyethylene glycol; ROS, reactive oxygen species; SOD, superoxide dismutase; H₂O_2, Hydrogen peroxide;     

The role of oxidative stress in spring barley cross-adaptation to different heavy metals

The aim of this study is to investigate the possibilities and the mechanisms of spring barley (Hordeum vulgare L.) cross-adaptation to different heavy metals after hardening with ozone (O₃), drought and UV-B radiation. Dry shoot biomass, accumulation of superoxide (O₂˙^?) and malondialdehyde (MDA), and activities of enzymes superoxide dismutase (SOD), glutathione reductase (GR) and catalase (CAT) were measured after hardening and heavy metal treatments. Seedlings, exposed to ozone and drought prior to copper (Cu) treatment, showed significantly increased tolerance to this heavy metal. The most possible causes of cross-adaptation to this redox-active heavy metal, which triggered very strong oxidative stress in nonhardened barley seedlings, were increased CAT activity, mitigation of O₂˙^? accumulation and lipid peroxidation. Cross-adaptation to cadmium (Cd) was induced only by drought hardening. In this case, however, adaptation had lower effect on antioxidative enzymes, did not altered O₂˙^? accumulation and even slightly increased the intensity of lipid peroxidation. The study reveals that stimulation of CAT activity and mitigation of oxidative stress are the main reasons for plant adaptation to Cu; whereas cross-adaptation to Cd, heavy metal with much lower oxidative capacity, is determined by the mechanisms that are not related to oxidative stress directly.     

Responses of Biochemical Markers in the Fish Prochilodus lineatus Exposed to a Commercial Formulation of Endosulfan

Among the most extensively used compounds for the pest control in Argentinean crops is the organochlorine endosulfan. The sublethal effects of the commercial endosulfan formulation on hematology and lipid peroxidation (LPO) of the neotropical fish Prochilodus lineatus were investigated. Firstly, we calculated acute toxicity (LC₅₀) in order to define sublethal concentrations (0, 1.2, and 2.4 ??g L^?1). Hematological and oxidative stress responses were assessed at 24, 48, and 96 h. Endosulfan exposure significantly diminished the hemoglobin concentration, mean cell hemoglobin, and total plasma protein and increased white blood cells count and plasma glucose after 96 h. Exposed fish showed an alteration of the differential leukocytes count, evidenced by more thrombocytes and monocytes and less lymphocytes and neutrophils. Endosulfan increased LPO levels in intestine, liver, and brain in both sublethal concentrations. The present results suggest that endosulfan produces biochemical and physiological alterations, including immunological disorders, and it is a good inductor of oxidative stress in P. lineatus.     

Differences in antioxidant enzyme activities and oxidative markers in ten wheat (Triticum durum Desf.) genotypes in response to drought,heat and paraquat stress

Changes in enzymatic antioxidants and oxidative injury were evaluated in leaves of 10 wheat genotypes under drought, heat and paraquat (PQ) stress. The seedlings of wheat were germinated in plastic pots and grown in a greenhouse under semi-controlled conditions. Each treatment was performed at the 4th–5th leaf stage. Antioxidant enzyme activities catalase (CAT), guaiacol peroxidase (GPOX), lipid peroxidation (LPO), hydrogen peroxide (H₂O₂) production, chlorophyll content and cell membrane leakage were determined. Results indicated that the three treatments decreased membrane stability, chlorophyll content and increased the LPO, H₂O₂ content and activities of CAT and GPOX. The ANOVA analysis revealed significant differences between genotypes in response to the various treatments imposed. Wheat genotypes Bidi 17, Beliouni and Djennah khetifa showed the lowest LPO and H₂O₂ content and the highest total chlorophyll content, relative electrolyte leakage (REL), CAT and GPOX activities, while Colosseo, Waha, Vitron and Benisuif showed the lowest antioxidant defends, lowest REL and the highest H₂O₂ and MDA contents. Oued zenati, Beltagy and Bousselam showed intermediate response in terms of oxidative stress and antioxidant activity.     

盐胁迫下两种草坪草膜脂过氧化和抗氧化酶比较

Salinity stress is a major factor limiting the growth of turfgrass irrigated with recycled wastewater. The change in lipid peroxidation in terms of malondialdehyde (MDA) content and the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxide (APX) and glutathione reductase (GR) in the shoots and roots of Kentucky bluegrass and tall fescue were investigated under salinity stress. Plants were subjected to 0, 50, 100, 150 and 200 mmol L 1 NaCl for 40 d. The MDA content under salinity stress was lower in tall fescue than in Kentucky bluegrass in both shoots and roots. Activities of SOD in the shoots of both species increased with salinity stress. The activities of CAT and APX decreased in Kentucky bluegrass, but no significant difference in the activities of CAT and APX was observed in tall fescue. The activities of SOD, CAT and APX in the shoots of tall fescue were higher than those in Kentucky bluegrass. In the roots of Kentucky bluegrass, SOD and GR activities increased and CAT and APX activities decreased in comparison with the control. In the roots of tall fescue, salinity increased the activities of SOD, CAT, and APX. These results suggested that tall fescue exhibited a more effective protection mechanism and mitigated oxidative stress and lipid peroxidation by maintaining higher SOD, CAT and APX activities than Kentucky bluegrass.     

Effects of cobalt oxide nanomaterial on plants and soil invertebrates at different levels of biological organization

Purpose

Metallic nanomaterials (MNM) like cobalt oxide (nano-Co₃O₄) are currently attracting enormous interest owing to their unique size and shape-dependent properties and potential applications in various sectors. The aims of this study were to assess the toxicity of nano-Co₃O₄ and to propose a risk limit through the estimation of a Predicted No Effect Concentration (PNEC) for this MNM to soil biota.

Materials and methods

For this purpose, a battery of sub-lethal ecotoxicological tests was performed to assess the influence of this MNM on four plant species (endpoints: germination and growth) and two invertebrate species (endpoints: avoidance and reproduction) following standard protocols. Further, biochemical endpoints (acetylcholinesterase [AChE], catalase [CAT], glutathione-S-transferase [GST] activity, and lipid peroxidation [LPO]) were also assessed in Eisenia andrei, one of the invertebrate species tested, in order to contribute for refining the PNEC value.

Results and discussion

The recorded data showed a significant inhibition in the germination of L. lycopersicum and in the growth of Z. mays, even at the lowest concentration tested (269.3 mg kg^?1 soil_dw of nano-Co₃O₄). Concerning the soil invertebrates, the results showed only significant avoidance (p?<?0.05) by E. andrei in the soil contaminated with the highest concentration tested (1000 mg kg^?1 soil_dw of nano-Co₃O₄), while no significant ecotoxicological effect on reproductive outputs of both species was recorded. However, the data reported for AChE, CAT, GST, and LPO showed significant effects at the range of concentrations tested in E. andrei. Thus, we recorded, the occurrence of oxidative stress and the enhancement of lipid peroxidation, on this invertebrate species.

Conclusions

The data obtained in this study supports the proposal of a PNEC value of 9.1 mg kg^?1 soil_dw for nano-Co₃O₄ in soil. The integration of data from biochemical endpoints allowed the refinement of the PNEC value and to obtain a more protective threshold.

     

Antimony Accumulation, Growth Performance, Antioxidant Defense System and Photosynthesis of Zea mays in Response to Antimony Pollution in Soil

Antimony (Sb) pollution in the downstream farmland soil of the Sb mine area has been of a great environmental concern to the local residents. However, effects of Sb on the growth and physiology of crops are still not well known. In the present study, Sb uptake and its effect on growth, antioxidant defense system, and photosynthesis of maize (Zea mays) were investigated. Our results demonstrated that accumulation of Sb in the maize increased with increasing Sb level in the soil. Sb could be easily translocated from root to shoot with a translocation coefficient over 2.05. Plant growth and biomass were reduced due to Sb pollution. Under Sb stress, the activities of peroxidase (POD), superoxide dismutases (SOD), and catalase (CAT) responded differently. The activities of POD and SOD were inhibited when the soil Sb concentration was higher than 50 mg kg^?1. CAT activity showed an increasing trend with increasing soil Sb concentration. Chlorophyll synthesis and the maximum photochemical efficiency (F _V/F _M) were also inhibited significantly under stress of high-level Sb in soil.     

EFFECT OF PLANT GROWTH-PROMOTING RHIZOBACTERIA STRAIN ON FREEZING INJURY AND ANTIOXIDANT ENZYME ACTIVITY OF WHEAT AND BARLEY

In 2009 a greenhouse experiment was conducted to determine the effects of boron (B) and plant growth-promoting rhizobacteria (PGPR) on wheat (Triticum aestivum spp. vulgare cv ‘Bezostiya’) and barley (Hordeum vulgare cv ‘Tokak’) on plant growth, freezing injury, and antioxidant enzyme capacity. Results showed that boron (0, 1, 3, 6, 9 kg B ha^?1) and PGPR application (Bacillus megaterium M3, Bacillus subtilis OSU142, Azospirillum brasilense Sp245 and Raoultella terrigena) at which 50% of leaves were injured (LT₅₀) values and ice nucleation activities in both plants were found statistically significant. Boron application with all PGPR strains decreased LT₅₀ values in wheat and barley plants under noncold stress (NCS) and cold stress conditions (CS). There were statistically significant differences between bacterial inoculation and B fertilizer in terms of root and shoot dry weight under NCS and CS conditions. Reactive oxidative oxygen species (ROS) and antioxidant enzyme activities (SOD, POD, CAT) were negatively affected CS conditions and decreased with reduced temperatures of media, but B and PGPR applications alleviated the low-temperature deleterious effects in both plants species tested. The lowest ROS and antioxidant enzyme (SOD, POD, CAT) of wheat and barley were observed with 6 kg B ha^?1 with R. terrigena.     

Coexpression of the superoxide dismutase and the catalase provides remarkable oxidative stress resistance in Lactobacillus rhamnosus

Lactic acid bacteria (LAB) are generally sensitive to oxidative stress caused by reactive oxygen species (ROS). Antioxidant enzymes, especially superoxide dismutase (SOD) and catalase (CAT), can protect against ROS by eliminating superoxide and H(2)O(2), respectively. Lactobacillus rhamnosus is a valuable probiotic starter culture but is deficient in both SOD and CAT, and is thus likely to suffer from oxidative stress in industrial fermentation. To confer high level of oxidative resistance on L. rhamnosus , the SOD gene sodA from Streptococcus thermophilus and CAT gene katA from L. sakei were coexpressed in L. rhamnosus AS 1.2466. The enzyme activities of SOD and CAT were 147.80 ± 1.08 U/mg protein and 2.53 μmol of H(2)O(2) /min/10(8) cfu, respectively, in the recombinant L. rhamnosus CS. After incubation with 10 mM H(2)O(2), the survival ratio of L. rhamnosus CS was 400-fold higher than that of L. rhamnosus CAT. In long-term aerated conditions, viable cells of L. rhamnosus CS remained ～10(6) cfu/mL after incubation for 7 days, while no living cells of the control were detected. These results showed that the cooperation between SOD and CAT could significantly enhance oxidative resistance in L. rhamnosus . To our best knowledge, this is the first report of two synergistic antioxidant genes being coexpressed in the same Lactobacilli.     

Silicon Increases Tolerance to Boron Toxicity and Reduces Oxidative Damage in Barley

ABSTRACT

Silicon (Si) protects plants from multiple abiotic and biotic stresses The effect of exogenous Si levels (50, 75, and 100 mg kg^?1) on the growth, boron (B) and Si uptake, lipid peroxidation (MDA), lipoxygenase activity (LOX; EC 1.13.11.12), proline, and H₂O₂ accumulation, non-enzymatic antioxidant activity (AA) and the activities of major antioxidant enzymes (superoxide dismutase, SOD, EC 1.15.1.1; catalase, CAT, EC 1.11.1.6 and ascorbate peroxidase, APX, EC 1.11.1.11) of barley (Hordeum vulgare L.) were investigated under glasshouse conditions. Increasing levels of Si supplied to the soil with 20 mg kg^?1 B counteracted the deleterious effects of B on shoot growth. Application of B significantly increased the B concentration in barley plants. However, Si application decreased B concentrations. Increasing application of Si increased the Si concentration in barley plants. The concentration of H₂O₂ was increased by B toxicity but decreased by Si supply. Boron toxicity decreased proline concentrations and increased lipid peroxidation (MDA content) and LOX activity of barley. Compared with control plants, the activities of AA, SOD, CAT, and APX in B stressed plants grown without Si decreased, and application of Si increased their activities under toxic B conditions. The LOX activity was decreased by Si. Based on the present work, it can be concluded that Si alleviates B toxicity by possibly preventing oxidative membrane damage, both through lowering the uptake of B and by increasing tolerance to excess B within the tissues.     

Cobalt accumulation and antioxidant system in pakchois under chemical immobilization in fluvo-aquic soil

Purpose

Cobalt (Co) is a toxic metal to the environment and human’s health. The purpose of the study is to achieve an investigation into the efficacy of calcium carbonate and cow dung for Co immobilization in fluvo-aquic soil, as well as their effects on the antioxidant system in plants.

Materials and methods

Calcium carbonate and cow dung were incorporated with the Co-polluted fluvo-aquic soil where pakchois (Brassica chinensis L.) were grown. Co concentration, superoxide dismutase (SOD) activity, catalase (CAT) activity, and malondialdehyde (MDA) concentration in the shoots of the mature plants were inspected.

Results and discussion

As calcium carbonate concentration rose (0 to 12 g kg^?1), Co concentration in shoots of the plants decreased firstly and then increased again (P < 0.05), while the accumulation level of Co kept decreasing with cow dung concentration rising (P < 0.05). Under the amendment treatments, the SOD activity, CAT activity, and MDA concentration in the shoots were all positively correlated to the Co concentration in the plant tissue (r = 0.792, 0.904, and 0.807, P < 0.01), indicating the antioxidant system receptivity to the Co accumulation. The amendments in soil can alleviate the oxidative stress in pakchois owing to Co pollution. As calcium carbonate concentration ranged from 5.64 to 7.86 g kg^?1, the parameters reached a maxima (minimum), respectfully.

Conclusions

Calcium carbonate and cow dung in fluvo-aquic soil are effective for Co immobilization and mitigating any pertinent oxidative stress in pakchoi plants. Calcium carbonate concentration within a range of 5.64 to 7.86 g·kg^?1 will achieve optimum efficacy.