Processing Effects on Selected Antioxidant Activities and Metabolizing Enzyme Inhibition of M. Koneigii (Curry Leaves) Extracts

Curry leaves, scientifically termed Murraya koenigii, are renowned in South Asian cuisine for their flavor enhancement and potential health benefits, including antioxidative, anti-inflammatory, and antidiabetic properties. This study aimed to evaluate the impact of thermal processing methods on curry leaves by analysing Total Phenolic Content (TPC), Total Flavonoid Content (TFC), antioxidant activity, and metabolizing enzyme inhibition. Fresh curry leaves were subjected to thermal treatments: Oven-dried at 60˚C and Air-dried at 25˚C for 2 weeks. Extracts were prepared using Ethanol and water solvents. Results indicated that Air-dried leaves exhibited significantly higher TPC (5132.65 mg GAE/100 g) and TFC (243.13 mg CE/100 g) compared to Fresh and Oven-dried leaves. Antioxidant assays show that oven-dried curry leaves at 60˚C displayed higher results in NORS, FRAP, and TEAC assays compared to Fresh and Air-dried leaves. Ethanol extracts showed better extraction of bioactive compounds than aqueous extracts. Moreover, Lipase inhibition activity was notably high, indicating potential health benefits. This study provides valuable insights into the effects of processing methods on curry leaf extracts, emphasizing the importance of solvent selection for optimal extraction of bioactive compounds.

Study on Antioxidant Enzyme Activity and Physiology and Biochemistry of Solanum nigrum L. under Glyphosate Stress

[Objectives] This study was conducted to investigate the scientific prevention and control of Solanum nigrum L. [Methods] Through experiments on S. nigrum from different sources, it was found that glyphosate stress had significant effects on antioxidant enzyme activity and oxidative damage of sensitive S. nigrum plants. [Results] Sensitive S. nigrum showed oxidative damage under glyphosate stress, while resistant S. nigrum responded to adversity damage by improving its antioxidant enzyme activity. The experimental results showed that the antioxidant enzymes and reduced glutathione of S. nigrum had certain metabolic detoxification effects under glyphosate stress. [Conclusions] This study provides a theoretical basis for scientific prevention and control of S. nigrum , and has a certain reference value for revealing the glyphosate resistance mechanism of S. nigrum .

Effects of mechanical damage and herbivore wounding on H2O2 metabolism and antioxidant enzyme activities in hybrid poplar leaves

The changes of hydrogen peroxide （H2O2） metabolism and antioxidant enzyme activities in a hybrid poplar （Populus simonii xp. pyramidalis ＇Opera 8277＇） in response to rnechanical damage （MD） and herbivore wounding （HW） were investigated to determine whether H2O2 could function as the secondary messenger in the signaling of systemic resistance. Results show that H2O2 was generated in wounded leaves through MD and HW treatments and systemically in unwounded leaves around the wounded leaves. The activities of antioxidant enzymes such as superoxide dismutase （SOD）, catalase （CAT） and ascorbate peroxidase （APX） were also enhanced. However, the H2O2 accumulation and antioxidant enzyme activities were inhibited in MD leaves through the pretreatment with DPI （which is a specific inhibitor of NADPH oxidase）. The results of this study suggest that H2O2 could be systemically induced by MD and HW treatments, and H2O2 metabolism was closely related to the change in SOD, APX and CAT activities. A high level of antioxidant enzymes could decrease membrane lipid peroxidation levels and effectively induce plant defense responses.

Distribution of Calcium in Bagged Apple Fruit and Relationship between Antioxidant Enzyme Activity and Bitter Pit

[Objective]The aim was to study the distribution of Ca in bagged apple fruit and the relationship between antioxidant enzyme activity and bitter pit disease,which will provide a basis for resolving Ca metabolism disorder in apple cultivation. [Method]With Fuji Apple as the tested material,the changes of Ca2＋ content and antioxidant enzyme activity in different parts of apple fruit after picking bags and storage period were determined. [Result]The results showed that Ca contents in the light surface of fruits were higher than that in the backlight surface. The Ca contents of stalk cavity were higher than that of calyx-end. The activities of SOD,POD,CAT and APX in the light surface of fruits were higher than that in the backlight surface. The activities of SOD,POD,CAT and APX of stalk cavity were higher than that of calyx-end. The contents of MDA in the light surface of fruits were lower than that in the backlight surface. The contents of MDA of stalk cavity were lower than that of calyx-end. [Conclusion]The incidence rate of bitter pit in the light surface of fruits were lower than that in the backlight surface,and the incidence rate of bitter pit of stalk cavity were lower than that of calyx-end.

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.

Research on Oxidative Stress Induced by Tenuazonic Acid from Alternaria augustiovoide and Changes in Antioxidant Enzyme Activities in Leaves of Echinochloa crus-galli

[Objective] The aim of the study was to determine whether phytotoxicity of TeA against Echinochloa crus-galli leaves was correlated with oxidative stress caused by generation of reactive oxygen and the changes of antioxidant enzymes activity.[Method] The changes of malondialdehyde（MDA）content,hydrogen peroxide（H2O2）,and activities of superoxide dismutase（SOD）,glutathione reductase（GR）and catalase（CAT）were studied by leaf segment method in vitro.[Result] After the treatment of 500 μmol/L TeA,the content of MDA and H2O2 increased by 247.86% and 67.00%,respectively,indicating that the accumulation of MDA and H2O2 in E.crus-galli leaves was due to the reactive oxygen burst induced by TeA.TeA induced a significant increase in activities of SOD,GR and CAT.At 500 μmol/L TeA,activities of SOD,GR and CAT increased more than one fold compared with the control.[Conclusion] TeA could not only cause oxidative stress in leaves of E.crus-galli through the induction of reactive oxygen,but also induce the increasing of antioxidant enzyme activity.

Extraction of Pumpkin Polysaccharide by Complex Enzyme Method and Its Antioxidant Research

[Objective] This paper aims to study a new method of extracting pumpkin polysaccharide from pumpkin. Single factor experiments were conducted to examine the effects of extracting time,temperature,the solid-liquid ratio and pH value on the extraction yield of polysaccharide from pumpkin. [Method] The best enzyme ratio and extraction conditions for complex enzymes extraction were determined through orthogonal tests. Scavenging ·OH and O-2 activities of pumpkin polysaccharides were also investigated by salicylic acid and improved self-oxidation of o-pheno methods respectively. [Results] The results showed that the biggest extraction yield of polysaccharide from pumpkin can be got when adding 1% cellulose enzyme,1.5% pectinase,1.0% papain and Na2HPO4-citric acid buffer solution (pH was 4.6),and oscillating for 30 min under water at 40 ℃ with the solid-liquid ratio of 1:30. In addition,pumpkin polysaccharides had a strong activity of eliminating ·OH,but very weak activity to scavenge O-2. [Conclusion] This study provided basic data for research and application of Pumpkin polysaccharide.

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.

Effects of Chitosan and Organosilicon on Antioxidant Enzyme Activity of Tomato Seedlings Diseased with Botrytis cinerea

[Objective] The aim was to explore effects of chitosan and organosilicon on tomato resistance against Botrytis cinerea. [Method] With leaf spraying method adopted, four groups were set in the test, including control group, groups treated with Botrytis cinerea, with chitosan and Botrytis cinerea, and with chitosan, organosilicon, and Botrytis cinerea, in order to study on effects of chitosan and organosilicon on antioxidant enzyme activities of tomato. [Result] Antioxidant enzyme activities of tomato seedlings were improved in groups with chitosan, organosilicon, and Botrytis cinerea and with chitosan and Botrytis cinerea compared with the group treated with Botrytis cinerea. On the 6th d, activities of PAL, SOD, POD, PPO and CAT in groups with chitosan and Botrytis cinerea, and with chitosan, organosilicon, and Botrytis cinerea increased by 27.36%, 52.07%, 43.55%, 82.02% and 71.82%, and 18.91%, 30.22%, 57.14%, 38.09% and 53.64%, respectively. [Conclusion] Antioxidant enzyme activities of tomato seedlings could be improved by chitosan and organosilicon.

Effects of Relative Soil Water Content on Antioxidant Enzyme System in Malus sieversii(Lebed.) Roem

By pot experiment under artificially simulated water stress conditions, soluble protein content, MDA content and SOD, POD, CAT and APX activities in Malus sieversfi leaves were determined to reveal the response mechanism of M. sieversii to changes of relative soil water content. According to the results, with the decrease of relative soil water content, MDA content in M. sieversii leaves increased by mem- brane lipid peroxidation. Cells resist water stress-induced membrane lipid peroxidation and clear the increased reactive oxygen species by improving soluble protein content and SOD, POD, CAT and APX activities. However, various enzymes were involved in the response to water stress under different moisture conditions. In addition, the results indicated that M. sieversii had a good adaptability to higher relative soil water contents.

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.

Phytotoxicity of cadmium on protein, proline and antioxidant enzyme activities in growing Arachis hypogaea L. seedlings

Phytotoxicity of cadmium on growing Arachis hypogaea L. seedlings was studied. Seeds were exposed to 25, 50, and 100 μmol/L CdCl2 concentrations, for a period of 10, 15, 20 and 25 d. The extent of damage to chlorophyll, protein, proline, nitrate and nitrite reductase, antioxidant enzyme activity in leaves and roots were evaluated after 10 d of cadmium stress. The higher concentration of cadmium （100 μmol/L） resulted （leaves and roots） total chlorophyll 91.01%, protein 79.51%, 83.61%, nitrate reductase 79.39%, 80.72% and nitrite reductase 77.07%, 75.88% activity decreased with increase in cadmium concentrations and exposure periods. Cadmium caused significant changes in the activity of antioxidative enzymes. Contrastingly Cd treated plant tissues showed an increase in proline 159.87%, 239.6%, gluthion reductase （GR） 337.72%, 306.14%, superoxide disumutase （SOD） 688.56%, 381.72%, ascorbate peroxidase （APX） 226.47%, 252.14%, peroxidase （POD） 72.19%, 60.29% and catalase （CAT） 228.96%, 214.74% as compared to control. Cadmium stress caused a significant increase in the rate of SOD activity in leaves and roots of plant species. Results show the crop A. hypogaea is highly sensitive even at very low cadmium concentrations.

Physiological responses of Brassica napus to fulvic acid under water stress: Chlorophyll a fluorescence and antioxidant enzyme activity

The ameliorative effect of fulvic acid(0, 300, and 600 mg L-1) on photosystem II and antioxidant enzyme activity of the rapeseed(Brassica napus L.) plant under water stress(60, 100, and 140 mm evaporation from class A pan) was studied using split plots in a randomized complete block design with three replications. Results indicated that application of fulvic acid(FA) improved the maximum quantum efficiency of PSII(Fv/Fm)and performance index(PI) of plants under both well-watered and limited-water conditions. The time span from Foto Fmand the energy necessary for the closure of all reaction centers was significantly increased, but the size of the plastoquinone pool was reduced with increasing water stress levels. Plants treated with FA had higher peroxidase and catalase activities under all irrigation conditions. Activities of ascorbate peroxidase and superoxide dismutase in plants increased with increasing water stress. Malondialdehyde increased under severe water stress, but application of FA significantly decreased lipid peroxidation. Production of reactive oxygen species(ROS) is a common phenomenon in plants under stress. Under this condition, the balance between the production of ROS and the quenching activity of antioxidants is upset, often resulting in oxidative damage. In this study, application of FA significantly increased fluorescence of chlorophyll a, inhibiting ROS production and enhancing antioxidant enzymes activity that destroyed ROS. Thus, ROS in plant cells was reduced under water stress by application of FA and consequently lipid peroxidation was reduced.

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.

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 Photosynthetic Capacity and Antioxidant Enzyme Activities in Chloroplast of Cucumber Seedlings Under Excess Manganese

Effects of silicon on photosynthetic parameters and antioxidant enzymes of chloroplast in cucumber seedlings under excess Mn were studied. Compared with the control, excess Mn significantly inhibited net photosynthetic rate （Pn）, stomatal conductance, as well as the maximum yield of the photosystem II photochemical reactions （Fv/Fm） and the quantum yield of photosysytem II electron transport （Φ PSII）, application of Si reversed the negative effects of excess Mn. In the further investigation, it was obtained that application of Si significantly increased the activities of enzymes related with ascorbate-glutathione cycle including ascorbate peroxidase （APX）, dehydroascorbate reductase （DHAR） and glutathione reductase （GR） in cucumber chloroplast under excess Mn, this could be responsible for the lower accumulation of H2O2 and lower lipid peroxidation of chloroplast induced by Mn, and resulted in keeping higher photosynthesis.

The Study on the Effects of Chinese Herbal Mixtures on Growth,Activity of Post-Ruminal Digestive Enzymes and Serum Antioxidant Status of Beef Cattle

Sixteen Limousin×Luxi crossbred beef cattle [（199.4±8.67） kg] were used to evaluate the effects of Chinese herbal mixtures （CHM） on growth, activities of post-ruminal digestive enzymes and serum antioxidant status of beef cattle. Treatments were control （no CHM supplementation） and three formulations of CHM （CHM-A, CHM-B and CHM-C） that were arranged as completely randomized design. The calves were fed in indoor individual feeding barn with total mixed ration for 90 d. The CHM-A, CHM-B, and CHM-C was incorporated into the diet at the level of 20 g kg-1 DM （dry matter） of concentrate. The cattle were weighted at the beginning, at the end and every 15 d between to determine growth rate. Blood sample was taken every 30 d to analyze activities of total superoxide dismutase （T-SOD） and glutathione peroxidase （GSH-PX） and concentration of malondialdehyde （MDA）. The cattle were slaughtered at the end of experiment and chymus samples from various section of the post-ruminal digestive tract were collected to analyze enzymes activities. All cattle had similar average daily gain, but cattle supplemented with CHM-A tended faster growth （P=0.08） compared to the control and other CHM treatments. Supplementation of CHM did not affect pH of chymus in any section of the post-ruminal digestive tract. Activities of pepsin, trypsin, chymotrypsin, and lipase in chymus samples were enhanced （P0.05） to various extents by supplementation of CHM-A, CHM-B, and CHM-C depending on the enzymes and the site of the digestive tract. Amylase activity was increased only by CHM-A and CHM-C from chymus sample collected at the ileum. Supplementation of CHM-A and CHM-B reduced （P0.05） concentration of MDA, but did not affect GSH-PX activity in the serum of cattle throughout the entire experimental period. Cattle supplemented with CHM-B also had higher （P0.05） T-SOD activity in the serum at day 30 and 60 as compared with the control and the other two CHM treatments. Chinese herbal mixtures supplemented at the levels of 20 g kg-1 DM of concentrate increased post-ruminal digestive enzymes activity and enhanced serum antioxidant status. Inclusion of CHM-A and CHM-B in the diet may be favourable for ruminant production.

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.

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.