Effect of Different Arbuscular Mycorrhizal Fungi Strains on Mineral Nutrition and Antioxidant Enzymes of Chrysanthemum morifolium

[Objective] The purpose was to study the effects of different arbuscular mycorrhizal fungi strains（AMF）on the mineral nutrition and antioxidant enzymes of Chrysanthemum morifolium.[Method] The pot experiment was conducted in the greenhouse,C.morifolium ＇Jinba＇ was inoculated with five kinds of AMF,N,P,K,malondial dehyde（MDA）content,as well as the superoxide dismutase（SOD）,peroxidase（POD） and catalase（CAT） activity in roots,leaves and petals of C.morifolium were measured at seedling and flowering stages.[Result] The G.i,G.e and G.m treatments could promote mineral nutrient absorption,increase N,P,K content in roots,leaves and petals of C.morifolium compared with the control without inoculation.The G.d、G.e and G.m treatments could significantly reduce MDA content in roots and petals,thus alleviating membrane permeability and lipid peroxidation.The G.i treatments could also improve the SOD,POD and CAT activities of C.morifolium,thereby increasing the capability of scavenging oxygen free radicals.[Conclusion] According to the comprehensive analysis,G.i was screened out as the best strain to improve mineral nutrition and antioxidant enzyme activities of C.morifolium.

Effects of Heavy-ion Beams Irradiation on Survival Rate and Antioxidant Enzymes of Sweet Sorghum Seedlings

[Objective] This study aimed to investigate the effects of heavy-ion beams irradiation on the seed germination potential, survival rate, antioxidant enzyme activi- ties and lipid peroxidation of sweet sorghum. [Method] The dry seeds were irradiated by ＇2（36. heavy ion beams with absorbed doses： 0, 40, 80, 120, 160 and 200 Gy, respectively. Then, the seed germination potential, survival rate, antioxidant enzyme activities and lipid peroxidation of sweet sorghum were measured. [Result] Heavy-ion beams irradiation exhibited different influence on germination potential and survival rates. Germination rate showed a downward trend, but the corresponding survival curve of seedlings was saddle-shaped. The activities of SOD, POD, CAT and ASA- POD changed in different trends as well. The MDA content rose toward increasing irradiation dose, suggesting that high dose of heavy-ion beams irradiation enhanced the damage to membrane of sweet sorghum seedlings. [Conclusion] After being irra- diated, germination potential and survival rates of sweet sorghum were decreased, and antioxidant enzymes activity changed greatly. This study laid the basis for fur- ther work on breeding and improvement of sweet sorghum irradiated by ,^（12）C^（6＋） heavy ion beams.

Effect of Botryosphaeria berengeriana f.sp.piricola and Biocontrol Bacteria on the System of Antioxidant Enzymes in Pears

[Objective] The aim was to understand defense mechanism of pear after inoculated Botryosphaeria berengeriana f. sp. piricolan and mechanism of antioxidant enzymes of biocontrol bacteria. [Method] Pears were treated by Botryosphaeria berengeriana f. sp. piricolan and bio control bacteria, and the change of antioxidant enzymes were determined. [Result] The biocontrol bacteria had little effect on MDA;the content of MDA treated by B. berengeriana reached high peak in 48 h, was 10.22nmol/g which was 1.86 times of CK; the content of MDA treated by B. berengeriana and biocontrol bacteria reached high peak in 24 h, was 8.92 nmol/g which was1.62 times of CK. The content of SOD treated by biocontrol bacteria reached high peak in 48 h, was 126.69 U/[g（FW）·min] which was 1.54 times of CK; the contents of SOD treated by B. berengeriana as well as B. berengeriana and biocontrol bacteria reached high peak in 24 h, were 122.10 and 135.32 U/[g（FW）·min] which were 1.48 and 1.65 times of CK respectively; the contents of POD on biocontrol bacteria treatment, B. ana treatment as well as B. berengeriana and biocontrol bacteria treatment reached high peak in 24 h, were 385.34, 342.50 and 290.00 U/[g（FW）·min] which were 1.83, 1.62 and 1.38 times of CK respectively. The contents of CAT on biocontrol bacteria treatment, B. rengeriana treatment as well as B. berengeriana and biocontrol bacteria treatment reached high peak in 6 h, were 133.33,114.17 and 113.35 U/[g（FW）·min] which were 1.33, 1.14 and 1.13 times of CK respectively. The biocontrol bacteria had little difference in CK; the content of PPO of B. berengeriana treatment reached high peak in 12 h, was 81.86 U/[g（FW）·min]which was 1.76 times of CK; B. berengeriana and biocontrol bacteria treatment reached high peak in 24 h, was 70.00 U/[g（FW）·min] which was 1.50 times of CK.[Conclusion] B. berengeriana and biocontrol bacteria had more effect on MDA; both B. berengeriana and biocontrol bacteria could increase the excitation of SOD enzyme activity; both B. berengeriana and biocontrol bacteria could increase the excitation of POD enzyme activity; both B. berengeriana and biocontrol bacteria could increase the excitation of CAT enzyme activity; using biocontrol bacteria alone had not obvious effect on PPO, B. berengeriana could increase the excitation of PPO enzyme activity.

Protective Role of Ca Against NaCl Toxicity in Jerusalem Artichoke by Up-Regulation of Antioxidant Enzymes

The ameliorative effect of external Ca^2＋ on Jerusalem artichoke （Helianthus tuberosus L.） under salt stress was studied through biochemical and physiological analyses of Jerusalem artichoke seedlings treated with or without 10 mol L^-1 CaCl2, 150 mmol L^-1 NaCl, and/or 5 mmol L^-1 ethylene-bis（oxyethylenenitrilo）-tetraacetic acid （EGTA） for five days. Exposure to NaC1 （150 mmol L^-1） decreased growth, leaf chlorophyll content, and photosynthetic rate of Jerusalem artichoke seedlings. NaC1 treatment showed 59% and 37% higher lipid peroxidation and electrolyte leakage, respectively, than the control. The activities of superoxide dismutase （SOD）, peroxidase （POD）, and catalase （CAT） were decreased by NaCl, indicating an impeded antioxidant defense mechanism of Jerusalem artichoke grown under salt stress. Addition of 10 mmol L^-1 CaCl2 to the salt solutions significantly decreased the damaging effect of NaC1 on growth and chlorophyll content and simultaneously restored the rate of photosynthesis almost to the level of the control. Ca^2＋ addition decreased the leaf malondialdehyde （MDA） content and electrolyte leakage from NaCl-treated seedlings by 47% and 24%, respectively, and significantly improved the activities of SOD, POD, and CAT in NaCl-treated plants. Addition of EGTA, a specific chelator of Ca2＋, decreased the growth, chlorophyll content, and photosynthesis, and increased level of MDA and electrolyte leakage from NaCl-treated plants and from the control plants. EGTA addition to the growth medium also repressed the activities of SOD, POD, and CAT in NaCl-treated and control seedlings. External Ca2＋ might protect Jerusalem artichoke against NaC1 stress by up-regulating the activities of antioxidant enzymes and thereby decreasing the oxidative stress.

Effects of melatonin on lipid peroxidation and antioxidant enzymes in streptozotocin-induced diabetic rat testis

Aim： To examine the effects of melatonin treatment on lipid peroxidation （LPO） and the activities of antioxidant enzymes in the testicular tissue of streptozotocin （STZ）-induced diabetic rats. Methods： Twenty-six male rats were randomly divided into three groups as follows： group Ⅰ, control, non-diabetic rats （n = 9）; group Ⅱ, STZ-induced, untreated diabetic rats （n = 8）; group Ⅲ, STZ-induced, melatonin-treated （dose of 10 mg/kg·day） diabetic rats （n = 9）. Following 8-week melatonin treatment, all rats were anaesthetized and then were killed to remove testes from the scrotum. Results： As compared to group Ⅰ, in rat testicular tissues of grouap Ⅱ, increased levels of malondialdehyde （MDA） （P 〈 0.01） and superoxide dismutase （SOD） （P 〈 0.01） as well as, decreased levels of catalase （CAT） （P 〈 0.01） and glutathione peroxidase （GSH-Px） （P 〉 0.05） were found. In contrast, as compared to group Ⅱ, in rat testicular tissues of group Ⅲ, levels of MDA decreased （but this decrease was not significant, P 〉 0.05） and SOD （P 〈 0.01） as well as CAT （P 〈 0.05） increased. GSH-Px was not influenced by any of the treatment. Melatonin did not significantly affect the elevated glucose concentration of diabetic group. At the end of the study, there was no significant difference between the melatonin-treated group and the untreated group by means of body and testicular weight. Conclusion： Diabetes mellitus increases oxidative stress and melatonin inhibits lipid peroxidation and might regulate the activities of antioxidant enzymes of diabetic rat testes.

Effects of insoluble Zn,Cd,and EDTA on the growth,activities of antioxidant enzymes and uptake of Zn and Cd in Vetiveria zizanioides

A root-bag experiment was conducted to study the effects of insoluble Zn, Cd, and ethylenediaminetetraacetic acid （EDTA） on the plant growth, activities of antioxidant enzymes, proline, glutathione （GSH）, water-soluble proteins and malondialdehyde （MDA） of Vetiveria zizanioides. The V. zizanioides uptake capacity of Zn and Cd also determined. The results showed that plant growth of V. zizanioides was inhibited by Zn and Cd. The shoot dry weight （SDW） and root dry weight （RDW） decrease by 14.2%, 14.1%, 17.0% and 17.3%, 32.5%, 35.7%, respectively, compared to the control without EDTA addition. After adding EDTA, shoot and root dry weight decreased over 10% and 15%, respectively. The toxicity from insoluble Zn and Cd in soil on SDW and RDW of V. zizanioides was in order： Zn＋Cd 〉 Cd 〉 Zn. The activities of superoxide dismutase （SOD）, peroxidase （POD） and catalase （CAT）, and contents of MDA and proline increased significantly, while the contents of GSH and water-soluble proteins decreased markedly with increasing Zn and Cd toxicity. With EDTA, shoot and root Zn concentrations increased in the Zn treatment by 7.3% and 37.4%, and Cd concentrations in the combined Zn and Cd treatment increased by 18.6% and 391.9% compared to the treatment without EDTA. However, Zn and Cd concentrations in shoot and roots decreased in the Cd treatment compared to the plants grown in absence of EDTA, with exception of root Cd concentration in the presence of EDTA.

Cobalt and manganese stress in the microalga Pavlova viridis (Prymnesiophyceae):Effects on lipid peroxidation and antioxidant enzymes

Pollution of marine environment has become an issue of major concern in recent years. Serious environmental pollution by heavy metals results from their increasing utilization in industrial processes and because most heavy metals are transported into the marine environment and accumulated without decomposition. The aim of the present study is to investigate the effects on growth, pigments, lipid peroxidation, and some antioxidant enzyme activities of marine microalga Pavlova viridis, in response to elevated concentrations of cobalt （Co） and manganese （Mn）, especially with regard to the involvement of antioxidative defences against heavy metal-induced oxidative stress. In response to Co^2＋, lipid peroxidation was enhanced compared to the control, as an indication of the oxidative damage caused by metal concentration assayed in the microalgal cells but not Mn^2＋. Exposure of Pavlova viridis to the two metals caused changes in enzyme activities in a different manner, depending on the metal assayed： after Co^2＋ treatments, total superoxide dismutase （SOD） activity was irregular, although it was not significantly affected by Mn^2＋ exposure. Co^2＋ and Mn^2＋ stimulated the activities of catalase （CAT） and glutathione （GSH）, whereas, glutathione peroxidase （GPX） showed a remarkable increase in activity in response to Co^2＋ treatments and decreased gradually with Mn^2＋ concentration, up to 50 μmol/L, and then rose very rapidly, reaching to about 38.98% at 200 μmol/L Mn^2＋. These results suggest that an activation of some antioxidant enzymes was enhanced, to counteract the oxidative stress induced by the two metals at higher concentration.

Effects of High Temperature on Antioxidant Enzymes and Lipid Peroxidation in Flag Leaves of Wheat During Grain Filling Period

On the basis of the phytotron, the effects of high temperature （daily average temperature 25, 30, 35 and 40℃, respectively） on antioxidant enzymes and lipid peroxidation in flag leaves of wheat at 50% relative air moisture during grain fastest filling stage [19-21 days after anthesis （DAA）] were studied. The wheat cultivars tested were Yangmai 9 with weak-gluten and Yangmai 12 with medium-gluten. Compared with 25℃, the higher the temperature was, the higher was the MDA content in flag leaves, while lower were the SOD, POD, and CAT activities. SOD and CAT activities in Yangmai 12 appeared to be more sensitive to high temperature than that in Yangmai 9. But POD activity in Yangmai 12 was less sensitive to high temperature. MDA content in Yangmai 12 was higher than that in Yangmai 9. The 1000-grain weight declined with increase in temperature.

Effects of osmotic stress on antioxidant enzymes activities in leaf discs of P_(SAG12)-IPT modified gerbera

Leaf senescence is often caused by water deficit and the chimeric gene PSA612-1PT is an auto-regulated gene delaying leaf senescence. Using in vitro leaf discs culture system, the changes of contents of chlorophylls, carotenoids, soluble protein and thiobarbituric acid reactive substance （TBARS） and antioxidant enzymes activities were investigated during leaf senescence of PSA612-1PT modified gerbera induced by osmotic stress compared with the control plant （wild type）. Leaf discs were incubated in 20%, 40% （w/v） polyethylene glycol （PEG） 6 000 nutrient solution for 20 h under continuous light [ 130 μmol/（m^2·s）]. The results showed that the contents of chlorophylls, carotenoids and soluble protein were decreased by osmotic stress with the decrease being more pronounced at 40% PEG, but that, at the same PEG concentration the decrease in the transgenic plants was significantly lower than that in the control plant. The activities of superoxide dismutase （SOD）, catalases （CAT）, ascorbate peroxidase （APX）, guaiacol peroxidase （GPX） and dehydroascorbate reductase （DHAR） were stimulated by PEG treatment. However, the increases were higher in PSA612-IPT transgenic plants than in the control plants, particularly at 40% PEG treatment. Lipid peroxidation （TBARS content） was increased by PEG treatment with the increase being much lower in transgenic plant than in the control plant. It could be concluded that the increases in the activities ofantioxidant enzymes including SOD, CAT, APX, GPX and DHAR were responsible for the delay of leaf senescence induced by osmotic stress.

Responses of Antioxidant Enzymes to Chilling Stress in Tobacco Seedlings

Chilling is one of the major abiotic stresses limiting yield and quality of many important crops. For better understanding of chilling stress responses in tobacco （Nicotiana tabacum）, growth rate and antioxidant enzymes of seedlings in 2 tobacco cultivars, viz., MSk326 （chilling sensitive variety） and Honghuadajinyuan （HHDJY, chilling tolerant variety） at chilling temperature （5℃） were studied. The results showed that the relative growth rate in chilling period to that in recovery period was significantly higher in roots than that in shoots for both cultivars, suggesting that shoots growth was more easily affected by chilling stress. Chilling stress increased peroxidase （POD） activity and reduced superoxide dismutase （SOD） activity in shoots of HHDJY, and catalase （CAT） activity was little affected. In the roots of HHDJY, chilling stress increased SOD and CAT activities, and had little effect on POD activity. For MSk326, chilling treatment increased SOD activity in shoots and declined CAT activity in roots. MDA concentration in both varieties was increased under the chilling stress, while it was decreased after seedlings were recovered growth for 4 d at normal temperature （25℃）. It showed that tobacco seedlings might have the capacity of recovering from chilling injury for a short term, The relationship between the growth rate and antioxidant enzyme activity was analyzed by stepwise regression. It was found that there was a close relationship between relative growth rate of tobacco seedlings and CAT activity under chilling stress condition and regression equations containing CAT could be used in predicting seedling growth rate of tobacco under chilling stress condition.

Effects of dietary menadione on the activity of antioxidant enzymes in abalone, Haliotis discus hannai Ino

A 240-day growth experiment in a re-circulating water system was conducted to investigate the effects of dietary menadione on the growth and antioxidant responses of abalone Haliotis discus hannai Ino. Triplicate groups of juvenile abalone (initial weight: 1.19 ± 0.01 g; shell length: 19.23 ± 0.01 mm) were fed to satiation with 3 semi-purified diets containing 0, 10, and 1 000 mg menadione sodium bisulfite (MSB)/kg, respectively. Results show that there were no significant differences in the rate of weight gain or in the daily increment in shell length of abalone among different treatments. Activities of superoxide dismutase (SOD), glutathione peroxidase (GPX), glutathione S-transferase (GST) and glutathione reductase (GR) in viscera were significantly decreased with dietary menadione. However, activities of these enzymes except for GPX in muscle were increased. Therefore, antioxidant responses of abalone were increased in muscle and decreased in viscera by dietary menadione.

Effects of Barium Stress in Brassica juncea and Cakile maritima:The Indicator Role of Some Antioxidant Enzymes and Secondary Metabolites

Soil contamination by toxic trace metal elements,like barium(Ba),may stimulate various undesirable changes in the metabolic activity of plants.The plant responses are fast and with,direct or indirect,generation of reactive oxygen species(ROS).To cope with the stress imposed by the ROS production,plants developed a dual cellular system composed of enzymatic and non-enzymatic players that convert ROS,and their by-products,into stable nontoxic molecules.To assess the Ba stress response of two Brassicaceae species(Brassica juncea,a glycophyte,and Cakile maritime,a halophyte),plants were exposure to different Ba concentrations(0,100,200,300 and 500µM).The plants response was evaluated through their morphology and development,the determination of plant leaves antioxidant enzymatic activities and by the production of plants secondary metabolites.Results indicated that the two Brassicaceae species have the ability to survive in an environment containing Ba(even at 500µM).The biomass production of C.maritima was slightly affected whereas an increase in biomass B.juncea was noticed.The stress imposed by Ba activated the antioxidant defense system in the two species,noticed by the changes in the leaves activity of catalase(CAT),ascorbate peroxidase(APX)and guaicol peroxidase(GPX),and of the secondary metabolites,through the production of total phenols and flavonoids.The enzymatic response was not similar within the two plant species:CAT and APX seem to have a more important role against the oxidative stress in C.maritima while in B.juncea is GPX.Overall,total phenols and flavonoids production was more significant in the plants aerial part than in the roots,of the both species.Although the two Brassicaceae species response was different,in both plants catalytic and non-catalytic transformation of ROS occurs,and both were able to overcome the Ba toxicity and prevent the cell damage.

Effects of Mutagens on Antioxidant Enzymes Activity and Cold Resistance of Alfalfa

This study aimed to solve the issues in safe wintering of alfalfa in the north of China. The^(60)Co-γ rays, ultraviolet and EMS were used to mutagenize seeds of 4 cultivars of alfalfa to investigate the effects of mutagens on antioxidant enzymes activity and cold resistance of alfalfa. The results showed that after the mutagenic treatment, the activity of the three kinds of antioxidant enzymes basically showed upward trends.^(60)Co-γ radiation increased the activity of SOD; ultraviolet radiation decreased the activity of SOD; and low-concentration EMS promoted and high-concentration EMS inhibited the activity of SOD. The activity of POD and CAT decreased with the increased radiation dose of^(60)Co-γ, but increased with the increased radiation dose of ultraviolet. The effects of EMS treatment on the activity of POD and CAT differed among different alfalfa cultivars. The concentration of MDA reduced under 30-min, 60-min ultraviolet treatment and 0.4% EMS treatment. According to the subordinate function values of various indices, it could be concluded that 150 Gy of^(60)Co-γ radiation, 90 min of ultraviolet radiation, and 0.4% of EMS were more conducive to improving the cold resistance of alfalfa. This study will provide a theoretical basis for the research on adaptability and cold resistance of alfalfa in rigid cold region and a technical reference for the breeding of high-yield, highquality and cold-resistant alfalfa cultivars.

Levels of antioxidant enzymes and alkaline protease from pulp and peel of sunflower

Objective:The activity of enzymes participating in the systems of antioxidant protection was assayed in the peel and pulp of sunflower.The essential roles of proteases in food stimulate research to find other sources of the enzyme especially from non-conventional sources.In the present work,we study several biochemical parameters in the pulp and peel of sunflower.Methods:Pulp and peel of sunflower was extracted,antioxidant enzymes and nonenzymatic antioxidant were measured.Alkaline protease was measured and purified from pulp in sunflower.Results:High carbohydrate concentration,beta-carotene,catalase and ascorbate peroxidase activities,free radical scavenging capacity and free flavonoid content were observed in the peel of sunflower.Whereas,MDA and ceruloplasmin activities were high in the pulp of sunflower.Conclusions:The present study concluded that peel in sunflower are strong radical scavengers and can be considered as good sources of natural antioxidants for medicinal and commercial uses.Further analysis showed that protease activity was a significantly high in the pulp compared to the peel.

Grafting Increases the Copper Tolerance of Cucumber Seedlings by Improvement of Polyamine Contents and Enhancement of Antioxidant Enzymes Activity

The aim of the study is to determine whether grafting could improve antioxidant enzyme activities and polyamine contents in leaves of cucumber plants（Cucumis sativus L.cv.Xintaimici） under copper stress.Grafted（using Cucurbita ficifolia as rootstock） and ungrafted cucumber seedlings were cultured in deep flow technique（DFT） with the Cu2＋ concentration of 40 μmol L-1.The results showed that on the 9th day of copper stress treatment,the contents of malondialdehyde（MDA） and hydrogen peroxide（H2O2）,superoxide radical（） producing rate,and electrolyte leakage percentage were significantly lower in grafted seedlings in comparison to those of the ungrafted seedlings,whereas the activities of antioxidants such as superoxide dismutase（SOD,EC 1.15.1.1）,peroxidase（POD,EC 1.11.1.7）,ascorbate peroxidase（APX,EC 1.11.1.11）,catalase（CAT,EC 1.11.1.6）,glutathione reductase（GR,EC 1.6.4.2）,and monodehydroascorbate reductase（MDHAR,EC 1.6.5.4） of grafted seedlings were also significantly higher than that of ungrafted seedlings,and the contents of free proline and soluble protein of grafted seedlings were significantly higher than that of ungrafted seedlings.Cu2＋ treatment increased the putrescine（Put） level and lowered the spermidine（Spd） and spermine（Spm） levels,thereby reducing the Put/（Spd ＋ Spm） ratio in leaves of grafted and ungrafted seedlings.Grafting markedly reversed these Cu-induced effects for all three PAs and partially restored the Put/（Spd ＋ Spm） ratio in leaves.These results suggest that grafting can enhance the tolerance of cucumber seedlings to Cu2＋ stress by increasing the activities of antioxidants and the levels of endogenous Spd and Spm,decreasing the Put/（Spd ＋ Spm） ratio and the levels of ROS,promoting free proline and soluble protein synthesis in cucumber seedling leaves.

Expression and sub-cellular localization of leucine-rich repeats and immunoglobulin-like domains are related to antioxidant enzymes in human ependymoma and oligodendroglioma

The current study investigated correlations between the expression of leucine-rich repeats and immunoglobulin-like domain 1 （LRIG1） and antioxidant enzymes and related proteins, including manganese superoxide dismutase, glutamate cysteine ligase catalytic or regulatory subunit, thioredoxin and thioredoxin reductase, in both human ependymoma and oligodendroglioma. Results revealed that the cytoplasmic expression of LRIG1 was associated with expression of glutamate cysteine ligase catalytic subunit in the human ependymoma, while the nuclear expression of LRIG1 was associated with expression of thioredoxin reductase. In human oligodendroglioma, the cytoplasmic expression of LRIG1 was associated with expression of the glutamate cysteine ligase catalytic subunit. Both the nuclear and perinuclear expressions of LRIG1 were associated with expression of glutamate cysteine ligase regulatory subunit. These results indicated that several antioxidant enzymes and related proteins contributed to LRIG1 expression, and that these may participate in the antioxidation of the cells.

Pesticide-Induced Alterations of Esterase and Antioxidant Enzymes of Aquatic Organisms Oreochromis mossambicus and Xenopus laevis

Pesticides are extensively utilized in modern farming to control pests and weeds, thereby ensuring high quality and quantity of crops. Aerial drifts and runoffs after rain transport these agrochemicals to aquatic bodies, where they adversely affect aquatic organisms. We carried out a study to assess the effects of carbaryl and dimethoate on esterase and antioxidant enzyme activities of tadpoles, adult frogs and juvenile fish. These organisms were exposed to sublethal contraptions of 2.9 ppm carbaryl and 4.8 ppm dimethoate for 96 hours. After the exposure period, the fish and frogs were sacrificed and post-mitochondrial fractions were prepared for enzymatic analysis. Acetylcholinesterase (AChE), carboxylesterase (CbE), superoxide dismutase, glutathione peroxidase and catalase were measured. Carbaryl and dimethoate inhibited the activities of acetylcholinesterase, carboxylesterase, superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) in juvenile fish, tadpoles and adult frogs. Inhibition of SOD, CAT and GPx suggests that the two pesticides caused oxidative stress in the aquatic organisms, while inhibition of AChE and CbE affected the normal transmission of nerve impulses. The results indicate that the two pesticides affect the well-being of the studied aquatic organisms.

Effect of Alkali Stress on Soluble Sugar, Antioxidant Enzymes and Yield of Oat

Alkali stress can cause severe crop damage and reduce production. However, physiological processes involved in alkali stress in oat seedlings are not well understood. In this study, physiological responses and yield of oat to alkali stress were studied using the alkali-tolerant oat genotype Vao-9 and the alkali-sensitive oat genotype Baiyan 5. The results were： （i） low concentrations of alkali stress （25 and 50 mmol L^-1） significantly reduced the yield and grain weight while increased the oat grain number per spike. A negative correlation between yield and malondialdehyde （MDA） content at the jointing and grain filling stages and positive correlations between yield on one hand and superoxide dismutase （SOD）, and peroxidase （POD） activities on the other at the jointing stage were observed. There was a positive correlation between MDA and soluble sugar at the grain filling stage; （ii） soluble sugar content was increased at the jointing and grain filling stages and decreased at the heading stage by alkali stress; （iii） alkali stress increased the SOD activity during the heading and grain filling stages, and increased the POD activity at the heading stage. As compared to the control, the increase of MDA contents in alkali-treated oat was observed, during the jointing, heading and grain filling stages; （iv） under alkali stress, the oat genotype Vao-9 showed higher antioxidant enzyme activity and lower soluble sugar contents during the heading stage, and lower MDA contents than those in the oat genotype Baiyan 5 under alkali stress. The result suggested that the high ROS scavenging capacity and soluble sugar levels might play roles in oat response to alkali stress,

Effects of Exogenous Silicon on the Activities of Antioxidant Enzymes and Lipid Peroxidation in Chilling-Stressed Cucumber Leaves

In order to increase vegetable productivity by improving environmental conditions, this article investigates the effects of exogenous silicon on the activities of major antioxidant enzymes and on lipid peroxidation under chilling stress, and it examines whether silicon-induced chilling tolerance is mediated by an increase in antioxidant activity. Cucumis sativus cv. Jinchun 4 was hydroponically cultivated to the two-leaf stage, at which point seedlings were watered with different concentrations of silicon (0, 0.1 and 1 mmol L^-1) and separately exposed to normal (25/18℃) or chilling (15/8℃) temperatures for six days under low light (100μmol m^-2 s^-9. Data were collected from the second leaves on the percentage of withering and the levels of endogenous silicon, malondialdehyde (MDA), hydrogen peroxide (H202), superoxide radical (O2^.-), superoxide dismutase (SOD, EC 1.15.1.1), glutathione peroxidase (GSH-Px, EC 1.11.1.9), ascorbate peroxidase (APX, EC 1.11.1.11), monodehydroascorbate reductase (MDHAR, EC 1.6.5.4), glutathione reductase (GR, EC 1.6.4.2), reduced glutathione (GSH) and ascorbate (AsA). Compared to normal temperatures, chilling resulted in partially withered leaves and increased MDA content. When 0.1 or 1 mmol L^-1 exogenous silicon was combined with chilling, the withering of the cucumber leaves was reduced relative to the original chilling treatment, while the endogenous silicon content was increased, antioxidants such as SOD, GSH-Px, APX, MDHAR, GR, GSH, and AsA were more active, and the levels of H2O2, O2^.-, and MDA were lower. We propose that exogenous silicon leads to greater deposition of endogenous silicon and thereby increases antioxidant activities and reduces lipid peroxidation induced by chilling.

Effect of Benzo[a]pyrene on Detoxification and the Activity of Antioxidant Enzymes of Marine Microalgae

The objective of this study was to examine the effect ofbenzo[a]pyrene （BaP） on the detoxification and antioxidant systems of two microalgae, Isochrysis zhanjiangensis and Platymonas subcordiformis. In our study, these two algae were exposed to BaP for 4 days at three different concentrations including 0.5 μg L-1 （low）, 3 μg L-1 （mid） and 18 μg L-1 （high）. The activity of detoxi- fication enzymes, ethoxyresorufin O-deethylase （EROD） and glutathione S-transferase （GST） increased in P subcordiformis in all BaP-treated groups. In 1. zhanjiangensis, the activity of these two enzymes increased at the beginning of exposure, and then de- creased in the groups treated with mid- and high BaP. The activity of antioxidant enzyme superoxide dismutase （SOD） increased in/. zhanjiangensis in all BaP-treated groups, and then decreased in high BaP-treated group, while no significant change was observed in P subcordiformis. The activity of antioxidant enzyme catalase （CAT） increased in I. zhanjiangensis and P subcordiformis in all BaP- treated groups. The content of malondialdehyde （MDA） in Isochrysis zhanjiangensis increased first, and then decreased in high BaP-treated group, while no change occurred in P. subcordiformis. These results demonstrated that BaP significantly influenced the activity of detoxifying and antioxidant enzymes in microalgae. The metabolic related enzymes （EROD, GST and CAT） may serve as sensitive biomarkers of measuring the contamination level of BaP in marine water.