The Effect of Acid Stress Treatment on Viability and Membrane Fatty Acid Composition of Oenococcus oeni SD-2a

To obtain ready-to-use wine malolactic starter cultures with high viability, the effects of acid stress treatments on the growth, inoculation viability, freeze-drying viability, and membrane fatty acid composition of the native Oenococcus oeni SD-2a strain were studied. The results showed that pH 3.5 and 3.2 adaptive treatments did not strongly decrease cell biomass but increased distinctly inoculation viability and freeze-drying viability. Concerning the membrane fatty acid composition, it was observed that acid stress conditions increased significantly the relative concentration of lactobacillic acid （C19cycl 1） and the unsaturated：saturated fatty acid ratio in cell membrane lipids. We assumed that acid-induced cross protective responses could be used in preparing ready-to-use O. oeni SD-2a malolactic starter cultures, and the accumulation of lactobacillic acid in the membrane of O. oeni SD-2a cells appears as an acid stress response mechanism, which might be related with the enhanced viability.

Application of organic fertilizer for improving soybean production under acidic stress

The presence of acidic soil in rural areas poses difficulties for agricultural production.One factor regulating soil pH is the overuse of inorganic fertilizer.The increased use of fertilizers in soybean production not only raises sustainability concerns but also contributes to soil acidity.Therefore,the use of organic fertilizer could offer a solution for addressing both issues related to soil acidity and sustainability.The purpose of this study was to investigate the manipulation of soil pH using organic fertilizer for soybean production under acidic stress.The planting medium,consisting of a mixture of topsoil,rice husk charcoal,and organic fertilizer(in a ratio of 2:1:1),was supplemented with 0.5 g of NPK fertilizer as a basal treatment in each planting medium.To regulate the soil acidity to pH 4,we added FeSO_(4) and allowed the mixture to incubate for 30 days.The results demonstrate that the application of three types of organic fertilizers chicken manure(P1),oil palm empty bunch fertilizer(P2),and vermicompost(P3)positively impacts the growth of three soybean varieties.The findings indicate that the application of P2 organic fertilizer can increase vegetative growth almost 50%in soybeans on acidic soil,including plant height,leaf count,and root length.Meanwhile,applying P3 organic fertilizer can boost reproductive growth responses in soybeans on acidic soil,such as pod number(from around 0-4 unit to 42-51 unit),grain number(from around 0-5 unit to 88-90 unit),and grain weight(from around 0-0.37 g to 12-25 g).Organic fertilizer has the potential to regulate soil pH,promoting higher yields of soybeans under acidic stress.

Acid stress response in environmental and clinical strains of enteric bacteria

The success of many enteric bacteria is hinged on the ability to tolerate environmental stress such as extreme acidity. The acid stress response （ASR） has been investigated in many enteric bacteria and has been shown to involve variable expression of a broad spectrum of genes involved in transcriptional regulation, metabolism, colonization and virulence; representing a linkage between acid tolerance and pathogenicity. Though the majority of ASR studies have been conducted in laboratory conditions and from the perspective of pathogenicity, the role of environmental reservoirs on acid adaptation has recently emerged as an important aspect of pathogenic microbial ecology. This mini-review profiles ASR in three opportunistic enteric pathogens and synthesizes recent work pertaining to the study of this dynamic response.

Effects of Salt Stress on Fatty Acid Composition of Thylakoid Membrane of Two Rice Cultivars Differing in Salt Tolerance

[Objective] The aim of the study is to understand the changes of fatty acid composition of rice thylakoid membrane under salt stress.[Method] Under salt stress of different concentrations of NaCl,rice seedlings of Pokkali and Peta with six leaves and one central leaf were used as experimental materials to extract the fatty acid from their thylakoid membranes,and gas chromatograph(1890)was used to analyze fatty acid composition.[Result] Fatty acid component 14∶0,18∶0,16∶1(3t),18∶1 in both the two experimental materials showed little variations in the first four days of salt stress,whereafter they increased slightly;while the fatty acid component 16∶0 and level of saturation of fatty acid(LSFA)showed the similar variation trend in the first four days of treatment compared to those of the fatty acid components mentioned above,whereafter they rose in Pokkali and presented an opposite variation trend in Peta;fatty acid component 18∶3 and level of unsaturation of fatty acid(LUFA)reduced all the time under stress condition,and the reducing amplitude in 100 mmol/L NaCl treatment group was smaller than that of 100 mmol/L NaCl treatment group,and in Pokkali was smaller than that in Peta under specific conditions.Meanwhile,level of saturation of fatty acid in both experimental materials increased,and the rising amplitude in Peta was smaller than that of Pokkali.[Conclusion] With regard to LUFA,Pokkali is endowed with more salt tolerance than Peta.

Efect of the Gad system on Actinobacillus succinogenes during acid stress

The glutamate decarboxylase(Gad)system is an important amino acid-dependent acid resistance system commonly found in microorganisms.Actinobacillus succinogenes is one of the best natural producers of succinic acid(SA)but lacks glutamate decarboxylase.This study assessed the efects of Gad system introduction into A.succinogenes.The recombinant strains gadB-SW and gadBC-SW were constructed by heterologous expression of gadB alone,or gadB together with gadC,respectively.After 1.0 and 1.5 h of acid stress at pH 4.6,cell survival of gadBC-SW was greater than gadB-SW.The growth of gadB-SW and gadBC-SW was both afected by the expression of heterologous proteins and byγ-aminobutyric acid,with gadBC-SW growth reduced at a neutral pH.SA production in acidic conditions was evaluated by a shake fask and by 3-L bioreactor fermentation.The results showed gadBC-SW to increase SA production by 8.4%in shake fask compared to the parent strain,SW.For a 3-L bioreactor batch fermentation under acidic environment,the highest conversion rate of sugar to SA was observed for gadBC-SW,reaching 96%.However,SA concentration by gadBC-SW was only 47 g/L and 31 g/L at pH 6.5 and pH 6.0,respectively.In summary,the introduction of heterologous gadB and gadC into A.succinogenes not only improved acid tolerance but also infuenced the synthesis of SA and added a metabolic burden.

Effects of Lanthanum on Redox Systems in Plasma Membranes of Casuarina equisetifolia Seedlings Under Acid Rain Stress

The effects of lanthanum on some redox system(PMRS) properties of the plasma membrane(PM) vesicles from Casuarina equisetifolia seedlings under artificial acid rain(pH 4.5)stress were studied. The results show that there are NADH oxidase and EDTA Fe 3+ reductase, and nitrate reductase in the seedling PM, and they have different responses to soaking seeds for 8 h in a series of LaCl 3 solution. The NADH oxidase activities and the Nitrate reductase activities can be stimulated when La 3+ concentrations is in the range of 50～200 mg·L -1 , but their activities are inhibited or fluctuate by the higher La 3+ concentrations. The EDTA Fe 3+ reductase activities can be stimulated by La 3+ concentrations in the range of 50～400 mg·L -1 . The research also revealed that La 3+ reduces the relative permeability of membranes and have the function in protecting membranes under acid rain stress by the way of inhibiting the leakage of electrolyte.

Effects of La^(3+) on ATPase Activities of Plasma Membrane Vesicles Isolated from Casuarina Equisetifolia Seedlings under Acid Rain Stress

The effects of La^(3+) on the growth and the ATPases activities of plasma membrane(PM) vesicles isolated from Casuarina equisetifolia seedlings under artificial acid rain(pH 4.5) stress were studied. The results show that the height, length of roots, fresh weight and PM H^+-ATPase activites of Casuarina equisetifolia seedlings increase by the treatments of soaking seeds in LaCl_3 solutions with lower concentrations, and those can reach their peak values by treating with 200 mg·L^(-1) La^(3+). However, in comparison with the CK, those are inhibited by the higher La^(3+) concentrations; PM Ca^(2+)-ATPase activity is inhibited with the treatments of La^(3+). The results also reveal that the H^+-ATPase activity and the growth of cell enlarge have a remarkable positive correlation, and La^(3+) activating H^+-ATPase can facilitate plant growth. La^(3+) also can alleviate cytosolic acidification of plant under acid rain stress and indirectly maintain the stability of intracellular environment. In order to resistant to acid rain and accelerate the growth of Casuarina equisetifolia, the suitable range of La^(3+) concentrations to soak seeds for 8 h is 50～200 mg·L^(-1).

Accumulation of Rare Earth Elements in Spinach and Soil under Condition of Using REE and Acid Rain Stress

The content and distribution characteristics of REE in spinach and soil under using REE and acid rain stress were studied by pot experiments. The results show that the content of REE is 0 527～0 696 (μg·g -1 ) in the above ground portion of spinach, 2 668～3 003 (μg·g -1 ) in the under ground portion of spinach and 229 09～250 30 (μg·g -1 ) in the soil. With the acidity of acid rain increasing, the leaching of REE in plants and soil is strengthened and the amount of REE reduces with decreasing of pH value. After REE are used, though plants show the selective absorption to Ce group elements (especially spraying on leaves), regardless under acid rain stress or using REE or not, the distribution model of REE in the above ground and under ground portion of plants is basically the same with the control. Plants also follow the Oddo Harkins rule of the REE of distribution abundance, light rare earth elements is enriched, the minus of Eu is abnormal and admeasure of Ce is a rich model. The results show that REE in plants mainly come from soil and are affected by it.

UV-Vis Spectroscopy Study on Interaction between Microperoxidase-11 and Pr Ion Under Acid Rain Stress

Interaction between rare earth ion praseodymium (Pr(Ⅲ)) and MP11 with/without hydrogen ion (H +) in different media( aqueous, phosphate buffer, physiological condition) were studied by UV Vis spectroscopy. All the results indicate that Pr(Ⅲ) interacts with MP11, increasing the non planarity of porphyrin periphery, leading MP11 to form two conformations when titrated by Pr(Ⅲ). Excessive Pr(Ⅲ) acts as a contaminant in living organism. H + and Pr(Ⅲ) have antagonistic effect on MP11, suggesting that at suitable concentration under physiological conditions, Pr(Ⅲ) can be used as biomodulator in protecting plants from acid rain stress or in rehabilitating the harm.

Effect of Ascorbic Acid and Silicium on Photosynthesis, Antioxidant Enzyme Activity, and Fatty Acid Contents in Canola Exposure to Salt Stress

The effects of exogenous ascorbic acid and silicium on leaf fresh weigh, seed yield, photosynthesis, changes of the activities of major antioxidant enzymes, nitrate reductase activity, proline accumulation, chlorophyll content, and fatty acid composition were investigated in salt-stressed canola. A hydroponic pot experiment was conducted based on randomized complete block design, factorial arrangement was used with 16 combinations of salinity stress （0, 100, 200, and 300 mmol L-1 NaC1）, ascorbic acid （0 and 30 mmol L-1）, and silicium （2 and 4 mmol L-1 from potassium silicate） with three replicates. The results showed that salinity significantly decreased leaf area and leaf fresh weight, seed yield, photosynthesis, nitrate reductase activity, chlorophyll content, and seed protein percentage. Conversely, respiration, antioxidant enzymes activity, proline accumulation, and linolenic acid percentage increased due to salt stress. Ascorbic acid application improved photosynthesis and seed yield and mitigated antioxidant enzyme activity. In addition, nitrate reductase activity and chlorophyll a and b were positively affected by ascorbic acid. Regarding silicium application, that was found that leaf area, leaf fresh weight, seed yield and photosynthesis, ascorbate peroxidase activity, nitrate reductase activity, and chlorophyll content increased, while respiration decreased. Furthermore, silicium had not significant effect on antioxidant enzyme activity. In general, ascorbic acid and silicium were involved in the defensive mechanisms against salinity stress and it can be suggested that, ascorbic acid and silicium application had positive effect on canola growth under conditions of salt stress.

Effects of Cinnamic Acid on Bacterial Community Diversity in Rhizosphere Soil of Cucumber Seedlings Under Salt Stress

To investigate the effects of a plant autotoxin, cinnamic acid, on bacterial communities in the rhizosphere soil of cucumber seedlings under salt stress, we used cucumber as the experimental material, cinnamic acid as the autotoxin, and NaCl to apply salt stress. Bacterial communities in the rhizosphere soil were analyzed using polymerase chain reaction （PCR）, denaturing gradient gel electrophoresis （DGGE）, and clone sequencing. Salt stress decreased the diversity of bacterial species in rhizosphere soil of cucumber seedlings at several growth stages. Cinnamic acid exacerbated the effects of salt stress at high concentrations, but alleviated its effects at low concentrations. Cloning and sequencing results indicated that DGGE bands amplified from soil samples showed high homology to uncultured bacterial species. Cinnamic acid at 50 mg kg^-1 soil improved cucumber growth and was the most effective treatment to alleviate the effects of salt stress on bacterial communities.

Effect of exogenous application of salicylic acid on the drought stress responses of Gardenia jasminoides

The alleviative effects of exogenous salicylic acid （SA） on plants against drought stress were assessed in Gardenia jasminoides seedlings treated with different concentrations of SA. Drought stress was simulated to a moderate level by 15% polyethylene glycol （PEG） 6000 treatment. Seedlings exposed to 15% PEG for 14 days exhibited a decrease in aboveground and underground dry mass, seedling height, root length, relative water content, photosynthetic pigment content, net photosynthetic rate （Pn）, transpiration rate （Tr）, stomatal conductance （Gs）, and water use efficiency. In PEG-stressed plants, the levels ofproline, malondialdehyde （MDA）, hydrogen peroxide （H2O2）, and electrolyte leakage rose significantly, whereas antioxidative activity, including superoxide, peroxidase, and catalase activities, declined in leaves. However, the presence of SA provided an effective method of mitigating PEG-caused physiological stresses on G. jasminoides seedlings, which depended on SA levels. PEG-treated plants exposed to SA at 0.5-1.0 mmol/L significantly eased PEG-induced growth inhibition. Application of SA, especially at concentrations of 0.5-1.0 mmol/L, considerably improved photosynthetic pigments, photosynthesis, antioxidative activity, relative water content, and proline accumulation, and decreased MDA content, H202 content, and electrolyte leakage. By contrast, the positive effects were not evident, or even more severe, in PEG＋SA4 treatment. Based on these physiological and biochemical data, a suitable concentration of SA, potential growth regulators, could be applied to enhance the drought tolerance of G. jasminoides.

Polyaspartic acid mediates the absorption and translocation of mineral elements in tomato seedlings under combined copper and cadmium stress

Polyaspartic acid(PASP)is a nontoxic,biodegradable,environmentally friendly polymer and is widely used as a fertilizer synergist in agricultural production.In many old orchards and vegetable gardens,highly fertile soil is often accompanied by severe heavy metal contamination.The present study was designed to investigate mineral element interactions mediated by PASP under copper(Cu)+cadmium(Cd)combined stress to provide reasonable suggestions for scientific fertilization.A pot experiment was conducted in which tomato seedlings served as plant materials.A concentration of 700 mgPASP and foliar spraying application methods were selected based on previous experiments.Four treatments were applied:normal soil(control(CK)),Cu+Cd(combined stress),Cu+Cd+PASP,and normal soil+PASP.The plant biomass,root activity,and mineral elements were measured,and these data were analyzed by Data Processing System(DPS)statistical software.The results showed that,under Cu+Cd combined stress,PASP promoted stem diameter growth,root activity and chlorophyll content and ultimately increased the biomass of tomato seedlings to different degrees.Moreover,the content of both Cu and Cd and their individual accumulation in plants decreased.PASP increased the distribution of Cu and Cd in the roots under Cu+Cd combined stress,and the translocation ability from the roots to shoots was significantly restricted.With respect to essential elements,PASP promoted mainly the absorption and translocation of potassium(K),calcium(Ca),and magnesium(Mg),which greatly exerted physiological roles.However,the variation trends of Cu and Cd under normal soil conditions contrasted with those under stress conditions.With respect to essential elements other than K,Ca,and Mg,PASP mostly restrained their absorption but promoted their translocation.The regulatory mechanism of PASP differed between the combined stress conditions and normal soil conditions.Under the combined stress conditions,PASP seemed to mainly promote these advantageous factors that exert physiological regulatory functions.Under normal soil conditions,PASP mainly acted as a biological stimulant or signaling molecule for increased nutrient efficiency,which caused greater biomass productivity.

Effects of rutin on oxidative stress in mice with kainic acid-induced seizure

Flavonoids are present in foods such as fruits and vegetables. Several studies have demonstrated a relationship between the consumption of flavonoid-rich foods and prevention of human disease, including neurodegenerative disorders. We assessed the effect of rutin （quercetin-3-O-rutinoside） on oxidative stress in kainic acid （KA）-induced seizure. METHODS： Thirty-six BALB/c mice were randomly divided into three groups. In the control group, saline （intra-peritoneal, i.p.） was administered for 7 d, and on the last day, KA （10 mg/kg, i.p.） was injected 30 min after administration of saline. In rutin groups, mice were pretreated with rutin （100 and 200 mg/kg, i.p.） for 7 d, and on the last day, KA （10 mg/kg, i.p.） was injected 30 min after administration of rutin. Subsequently, behavioural changes were observed in mice. Lipid peroxidation and oxidative stress were measured respectively in the early and late phases after KA-induced seizures. RESULTS： Seizure scores in the rutin groups were significantly lower than those in the control group （P 〈 0.01）. Furthermore, rutin dose-dependently inhibited the number of wet-dog shakes （WDS） （P 〈 0.05）. Malondialdehyde level in the hippocampus of the rutin groups was significantly lower than that in the hippocampus of the control group on days 1 and 21 after KA administration. In the rutin groups, the thiol levels observed on day 1 after KA administration were higher than that in the control group （P 〈 0.01）. CONCLUSION： These results indicate that rutin has potential anticonvulsant and antioxidative activities against oxidative stress in KA-induced seizure in mice.

Effects of applied potential on the stress corrosion cracking behavior of 7003 aluminum alloy in acid and alkaline chloride solutions

Potentiodynamic polarization tests and slow strain rate test（SSRT） in combination with fracture morphology observations were conducted to investigate the stress corrosion cracking（SCC） behavior of 7003 aluminum alloy（AA7003） in acid and alkaline chloride solutions under various applied potentials（Ea）. The results show that AA7003 is to a certain extent susceptible to SCC via anodic dissolution（AD） at open-circuit potential（OCP） and is highly susceptible to hydrogen embrittlement（HE） at high negative Ea in the solutions with p H levels of 4 and 11. The susceptibility increases with negative shift in the potential when Ea is less than-1000 m V vs. SCE. However, the susceptibility distinctly decreases because of the inhibition of AD when Ea is equal to-1000 m V vs. SCE. In addition, the SCC susceptibility of AA7003 in the acid chloride solution is higher than that in the alkaline solution at each potential. Moreover, the effect of hydrogen on SCC increases with increasing hydrogen ion concentration.

Analysis of Organic Acids Accumulated in Kochia Scoparia Shoots and Roots by Reverse-phase High Performance Liquid Chromatography Under Salt and Alkali Stress

Several organic acids accumulated in Kochia Scoparia shoots and roots were studied by means of reverse-phase high performance liquid chromatography with a C18 column. Five types of binary organic acids were separated. The organic acid concentrations were determined in K. Scoparia seedlings stressed by saline （NaCI） and alkaline （NaHCO3） at the same Na^＋ concentration. Concentrations of organic acids are stimulated by alkaline because the cells will adjust their pH values through the accumulation of organic acids, when the environment is basic. The concentrations of oxalic acid and succinic acid are higher than those of other organic acids, including tartaric acid and malic acid, and the concentration of citric acid is the lowest. The concentrations of the organic acids in the roots are higher than those in the shoots under salt（NaCI） stress, but the results are opposite while the roots are under alkali （ NaHCO3 ） stress. This indicates that there are different adaptive strategies for K. Scopar/a seedlings in organic acid metabolism under salt and alkali stress.

Exogenous Application of Salicylic Acid and Nitric Oxide on the Ionic Contents and Enzymatic Activities in NaCl-Stressed Soybean Plants

The possible protective role of exogenous SA and NO donor (sodium nitroprusside) against salt stress was examined NaCl-induced oxidative stress in Glycine max L. The results indicated that NaCl-induced ionic toxicity led to significant increase of Na+ uptake in root and shoot of soybean, while K+ and Ca2+ uptake was decreased markedly. Application of SA, SNP and the combination of SA with SNP inhibited Na+ uptake, but improved K+ and Ca2+ uptake. Under NaCl salinity, germination percentage (GP) was decreased significantly as compared with control plants. Moreover, the activity of lipoxygenase (LOX) was increased by NaCl, while the application of SA, NO and SA + SNP could decrease LOX activity in this condition. As well, activities of the polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) were significantly decreased by 100 mM NaCl, while the application of exogenous SA and NO increased the activities of PPO and PAL. In addition, it was observed that the SA and NO have effective functions in decreasing the damages induced by NaCl salinity. The seeds of G. max cv. Union × Elf (called L17) were obtained from the Institute of Sapling and Seed in Tehran and experiments have been done in Science and Research Branch, Islamic Azad University. After treatment with SA, SNP and NaCl, the plants were harvested for the estimation of ionic contents and assay of enzyme activities. The results showed that SA and NO act synergistically to reduce the damaging effects of salt tress via enhancing the activity of antioxidative systems.

Effect of sodium salicylate on oxidative stress and insulin resistance induced by free fatty acids

BACKGROUND: It has been reported that high-dose salicylates improve free fatty acids (FFAs)-induced insulin resistance and beta-cell dysfunction in vitro, but the mechanism remains uncertain. In insulin-resistant rats, we found that the supplementation of sodium salicylate is associated with a reduction of plasma malondialdehyde (MDA), a marker of oxidative stress. Few studies have investigated the effects of salicylates on oxidative stress levels in insulin-resistant animal models. This study aimed to assess the effect of sodium salicylate on insulin sensitivity and to explore the potential mechanism by which it improves hepatic and peripheral insulin resistance. METHODS: Intralipid+heparin (IH), saline (SAL), or intralipid+heparin+sodium salicylate (IHS) were separately infused for 7 hours in normal Wistar rats. During the last 2 hours of the infusion, hyperinsulinemic-euglycemic clamping was 3 performed with [6-(3)H] glucose tracer. Plasma glucose was measured using the glucose oxygenase method. Plasma insulin and C-peptide were determined by radioimmunoassay. MDA levels and glutathione peroxidase (GSH-PX) activity in the liver and skeletal muscle were measured with colorimetric kits. RESULTS: Compared with infusion of SAL, IH infusion increased hepatic glucose production (HGP), and decreased glucose utilization (GU) (P<0.05). The elevation of plasma free fatty acids increased the MDA levels and decreased the GSH-PX activity in the liver and muscle (P<0.01). Sodium salicylate treatment decreased HGP, elevated GU (P<0.05), reduced MDA content by 60% (P<0.01), and increased the GSH-PX activity by 35% (P<0.05). CONCLUSIONS: Short-term elevation of fatty acids induces insulin resistance by enhancing oxidative stress levels in the liver and muscle. The administration of the anti-inflammatory drug sodium salicylate reduces the degree of oxidative stress, therefore improving hepatic and peripheral insulin resistance. IKK-beta and NF-kappa B provide potential pathogenic links to oxidative stress.

Syringic acid improves oxidative stress and mitochondrial biogenesis in the liver of streptozotocin-induced diabetic rats

Objective:To determine the effects of syringic acid on hepatic damage in diabetic rats.Methods:Diabetes was induced by streptozotocin.Diabetic rats were given syringic acid at doses of 25,50 and 100 mg/kg by oral gavage for 6 weeks.Syringic acid effects on the liver were evaluated by examination of plasma biochemical parameters,and pathological study.In addition,biomarkers of lipid peroxidation and antioxidant status of liver tissues were assessed.Real time-PCR was performed to investigate the m RNA expression levels of mitochondrial biogenesis indices in different groups.Results:Syringic acid significantly attenuated the increase in most of plasma biochemical parameters in diabetic rats.Moreover,syringic acid treatment increased the catalase activity while it reduced the superoxide dismutase activity and hepatic malondialdehyde level in diabetic rats.There was no difference between the glutathione content of the treated and untreated groups.These findings were supported by alleviation of histopathological damages in the syringic acid-treated groups compared to the untreated diabetic group.Syringic acid also significantly upregulated the hepatic m RNA expression of PGC-1α,NRF-1,and NRF-2 and increased the mtD NA/nD NA ratio in diabetic rats.Conclusions:Syringic acid can be considered as a suitable candidate against hepatic complications since it can reduce oxidative damages in diabetic cases.Furthermore,it has the potential of targeting hepatic mitochondria in diabetes.

Exogenous application of succinic acid enhances tolerance of Larix olgensis seedling to lead stress

Larix olgensis A. Henry(Changbai larch) is a productive commercial species and good candidate for afforestation in northeast China. It is widely planted in lead-stressed soils which can induce oxidative damage in this plant. Increasing tolerance to lead(Pb) stress is therefore of keen interest. A greenhouse experiment was conducted to identify the biomass, physiological responses and Pb accumulation of L. olgensis seedlings to Pb stress under succinic acid(SA) application and to explore the interaction of exogenous SA applications and stress resistance. L. olgensis seedlings were planted in Pb-stressed or unstressed haplic cambisols in pots. In Pb-contaminated soils the seedlings were treated daily with concentrations of SA solutions at a rate approximately equivalent to 0, 0.04,0.2, 1.0, or 2.0 mmol kg-1of soil for 10, 20, and 30 days,respectively. Pb treatment induced damage in the seedlings and led to the inhibition of biomass accumulation in roots,stems and leaves, and a rise in Pb accumulation in fine roots and leaves. Malondialdehyde(MDA) content and electrolyte leakage in leaves significantly increased while peroxidase(POD) activities, soluble protein and photosynthetic pigment contents in leaves were all reduced.Physiological toxicity was promoted with increasing Pb treatment times. When Pb-stressed seedlings were exposed to SA(especially 10.0 mmol L-1 over 20 days), the physiological responses for Pb-only were reversed and the biomass of roots, stems, and leaves dramatically increased.SA facilitated Pb uptake in fine roots and leaves but more Pb accumulated in fine roots. The results demonstrate that exogenous SA alleviates Pb-induced oxidative injuries and improves the tolerance of L. olgensis seedlings to Pb stress.