Increased Antioxidant Activity under Elevated Temperatures: A Mechanism of Heat Stress Tolerance in Wheat Genotypes

An experiment was conducted with three wheat (Triticum aestivum L.) genotypes C 306, HD 2285 and HD 2329 (differently susceptible to water and temperature stress) to study the extent of oxidative injury and activities of antioxidant enzymes in relation to heat stress induced by manipulating dates of sowing. Increase in temperature by late sowing significantly decreased leaf relative water content (RWC), ascorbic acid content, and increased H₂O₂ content and lipid peroxidation in all the genotypes at 8 and 23 d after anthesis. Temperature tolerant genotypes C 306, closely followed by HD 2285 were superior to HD 2329 in maintaining high RWC, ascorbic acid content, and lower H₂O₂ content and lipid peroxidation (malondialdehyde content) under high temperature (late sowing) at the two stages. Activities of superoxide dismutase and catalase were highest in HD 2285 followed by C 306 and minimum in HD 2329 while ascorbate peroxidase activity was highest in C 306.     

Drought induced programmed cell death and associated changes in antioxidants, proteases, and lipid peroxidation in wheat leaves

Two wheat (Triticum aestivum L.) genotypes with varying degree of drought tolerance were used to analyze programmed cell death (PCD) and related biochemical changes under drought stress. Drought induced PCD in leaves, as evident by internucleosomal nDNA fragmentation, was observed in sensitive genotype Nesser. Drought tolerant genotype (FD-83) showed higher peroxidase, superoxide dismutase, and catalase activities and ascorbate content under drought stress compared to sensitive genotype. Total phenolic content increased whereas lipid peroxidation remained un-changed under drought in FD-83. In contrast, drought enhanced the proteases and ascorbate peroxidase activities and lipid peroxidation (MDA content) in Nesser.     

Stress induced injury and antioxidant enzymes in relation to drought tolerance in wheat genotypes

The role of plant antioxidant system in water stress tolerance was studied in three contrasting wheat genotypes. Water stress imposed at different stages after anthesis resulted in a general increase in lipid peroxidation (LPO) and decrease in membrane stability index (MSI), and contents of chlorophylls (Chl) and carotenoids (Car). Antioxidant enzymes like glutathione reductase and ascorbate peroxidase significantly increased under water stress. Genotype C 306, which had highest glutathione reductase and ascorbate peroxidase activity, also showed lowest LPO and highest MSI, and Chl and Car contents under water stress in comparison to susceptible genotype HD 2329, which showed lowest antioxidant enzyme activity as well as MSI, Chl and Car contents and highest LPO. HD 2285 which is tolerant to high temperature during grain filling period showed intermediate behaviour. Thus, the relative tolerance of a genotype to water stress as reflected by its comparatively lower LPO and higher MSI, Chl and Car contents is closely associated with its antioxidant enzyme system. This revised version was published online in August 2006 with corrections to the Cover Date.     

Evaluation of oxidative stress tolerance in maize (Zea mays L.) seedlings in response to drought

Seedlings of selected six genotypes of maize (Zea mays L.) differing in their drought sensitivity (LM5 and Parkash drought-tolerant and PMH2, JH3459, Paras and LM14 as drought-sensitive) were exposed to 72 h drought stress at two leaf stage. Alterations in their antioxidant pools combined with activities of enzymes involved in defense against oxidative stress were investigated in leaves. Activities of some reactive oxygen species (ROS)-scavenging enzymes, catalase (CAT) and ascorbate peroxidase (APX) were enhanced in tolerant genotypes in response to drought stress. Superoxide dismutase (SOD) activity was significantly decreased in sensitive genotypes, but remained unchanged in tolerant genotypes under stress. Peroxidase (POX) activity was significantly induced in tolerant, as well as sensitive genotypes. Imposition of stress led to increase in H2O2 and malondialdehyde (MDA, a marker for lipid peroxidation) content in sensitive genotypes, while in tolerant genotypes no change was observed. Significant increase in glutathione content was observed in sensitive genotypes. Ascorbic acid pool was induced in both tolerant and sensitive genotypes, but induction was more pronounced in tolerant genotypes. Significant activation of antioxidative defence mechanisms correlated with drought-induced oxidative stress tolerance was the characteristic of the drought tolerant genotypes. These studies provide a mechanism for drought tolerance in maize seedlings.     

Salt-Induced Changes in Physio-Biochemical and Antioxidant Defense System in Mustard Genotypes

Salinity stress is a major factor limiting plant growth and productivity of many crops including oilseed. The present study investigated the identification of salt tolerant mustard genotypes and better understanding the mechanism of salinity tolerance. Salt stresses significantly reduced relative water content (RWC), chlorophyll (Chl) content, K⁺ and K⁺ /Na⁺ ratio, photosynthetic rate (P_N), transpiration rate (Tr), stomatal conductance (gs), intercellular CO₂ concentration (Ci) and increased the levels of proline (Pro) and lipid peroxidation (MDA) contents, Na⁺ , superoxide (O₂^•− ) and hydrogen peroxide (H₂O₂) in both tolerant and sensitive mustard genotypes. The tolerant genotypes maintained higher Pro and lower MDA content than the salt sensitive genotypes under stress condition. The activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), glutathione peroxidase (GPX), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) were increased with increasing salinity in salt tolerant genotypes, BJ-1603, BARI Sarisha-11 and BARI Sarisha-16, but the activities were unchanged in salt sensitive genotype, BARI Sarisha-14. Besides, the increment of ascorbate peroxidase (APX) activity was higher in salt sensitive genotype as compared to tolerant ones. However, the activities of glutathione reductase (GR) and glutathione S-transferase (GST) were increased sharply at stress conditions in tolerant genotypes as compared to sensitive genotype. Higher accumulation of Pro along with improved physiological and biochemical parameters as well as reduced oxidative damage by up-regulation of antioxidant defense system are the mechanisms of salt tolerance in selected mustard genotypes, BJ-1603 and BARI Sarisha-16.     

Hydrogen peroxide pre-treatment induces salt-stress acclimation in maize plants

The effect of exogenously applied H2O2 on salt stress acclimation was studied with regard to plant growth, lipid peroxidation, and activity of antioxidative enzymes in leaves and roots of a salt-sensitive maize genotype. Pre-treatment by addition of 1 microM H2O2 to the hydroponic solution for 2 days induced an increase in salt tolerance during subsequent exposure to salt stress. This was evidenced by plant growth, lipid peroxidation and antioxidative enzymes measurements. In both leaves and roots the variations in lipid peroxidation and antioxidative enzymes (superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase, glutathione reductase, and catalase) activities of both acclimated and unacclimated plants, suggest that differences in the antioxidative enzyme activities may, at least in part, explain the increased tolerance of acclimated plants to salt stress, and that H2O2 metabolism is involved as signal in the processes of maize salt acclimation.     

Role of antioxidant and anaerobic metabolism enzymes in providing tolerance to maize (Zea mays L.) seedlings against waterlogging

The present investigation was undertaken to identify the possible mode of mechanism that could provide tolerance to maize (Zea mays L.) seedlings under waterlogging. Using cup method, a number of maize genotypes were screened on the basis of survival of the seedlings kept under waterlogging. Two tolerant (LM5 and Parkash) and three susceptible (PMH2, JH3459 and LM14) genotypes were selected for the present study. Activities of antioxidant and ethanolic fermentation enzymes and content of hydrogen peroxide (H2O2), glutathione and ascorbic acid were determined in roots of these genotypes after 72 h of waterlogging. Waterlogging treatment caused decline in activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) in all the genotypes. However, only susceptible genotypes showed slight increase in glutathione reductase (GR) activity. Significant reduction in APX/GR ratio in susceptible genotypes might be the cause of their susceptibility to waterlogging. The tolerant seedlings had higher GR activity than susceptible genotypes under unstressed conditions. Stress led to decrease in H202 and increase in glutathione content of both tolerant and susceptible genotypes, but only tolerant genotypes exhibited increase in ascorbic acid under waterlogging conditions. In the tolerant genotypes, all the enzymes of anaerobic metabolism viz. alcohol dehydrogenase (ADH), aldehyde dehydrogenase (ALDH) and pyruvate decarboxylase (PDC) were upregulated under waterlogging, whereas in susceptible genotypes, only ADH was upregulated, suggesting that efficient upregulation of entire anaerobic metabolic machinery is essential for providing tolerance against waterlogging. The study provides a possible mechanism for waterlogging tolerance in maize.     

Proline improves copper tolerance in chickpea (Cicer arietinum)

The present study suggests the involvement of proline in copper tolerance of four genotypes of Cicer arietinum (chickpea). Based on the data of tolerance index and lipid peroxidation, the order for copper tolerance was as follows: RSG 888?>?CSG 144?>?CSG 104?>?RSG 44 in the selected genotypes. The basis of differential copper tolerance in chickpea genotypes was characterized by analyzing, antioxidant enzymes (superoxide dismutase, ascorbated peroxidase and catalase), phytochelatins, copper uptake, and proline accumulation. Chickpea genotypes showed stimulated superoxide dismutase activity at all tested concentrations of copper, but H₂O₂ decomposing enzymes especially; ascorbate peroxidase did not increase with 25 and 50 μM copper treatments. Catalase activity, however, increased at lower copper concentrations but failed to stimulate at 50 μM copper. Such divergence in responses of these enzymes minimizes their importance in protecting chickpea against copper stress. The sensitive genotypes showed greater enhancement of phytochelatins than that of tolerant genotypes. Hence, the possibility of phytochelatins in improving copper tolerance in the test plant is also excluded. Interestingly, the order of proline accumulation in the chickpea genotypes (RSG 888?>?CSG 144?>?CSG 104?>?RSG 44) was exactly similar to the order of copper tolerance. Based on hyperaccumulation of proline in tolerant genotype (RSG 44) and the reduction and improvement of lipid peroxidation and tolerance index, respectively, by proline pretreatment, we conclude that hyperaccumulation of proline improves the copper tolerance in chickpea.     

Involvement of Lipid Peroxidation in Water Stress-Promoted Senescence of Detached Rice Leaves

Role of lipid peroxidation and antioxidative enzymes (catalase, peroxidase, superoxide dismutase, ascorbate peroxidase and glutathione reductase) in water stress-promoted senescence of detached rice leaves was investigated. The senescence was followed by measuring the decrease in protein content. Increased lipid peroxidation was closely correlated with senescence in water stressed leaves. Decrease in superoxide dismutase activity was evident 8 h after beginning of water stress. However, decreased catalase, peroxidase, and ascorbate peroxidase activity was observed only when senescence was observed. Glutathione reductase was not affected by water stress. Free radical scavengers retarded water stress-enhanced senescence.     

Arbuscular mycorrhizal fungi regulate the oxidative system,hormones and ionic equilibrium to trigger salt stress tolerance in Cucumis sativus L.

Arbuscular mycorrhizal fungi (AMF) association increases plant stress tolerance. This study aimed to determine the mitigation effect of AMF on the growth and metabolic changes of cucumbers under adverse impact of salt stress. Salinity reduced the water content and synthesis of pigments. However, AMF inoculation ameliorated negative effects by enhancing the biomass, synthesis of pigments, activity of antioxidant enzymes, including superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase, and the content of ascorbic acid, which might be the result of lower level lipid peroxidation and electrolyte leakage. An accumulation of phenols and proline in AMF-inoculated plants also mediated the elimination of superoxide radicals. In addition, jasmonic acid, salicylic acid and several important mineral elements (K, Ca, Mg, Zn, Fe, Mn and Cu) were enhanced with significant reductions in the uptake of deleterious ions like Na+. These results suggested that AMF can protect cucumber growth from salt stress.     

Trichiliadregeana胚轴的脱水敏感性与抗坏血酸的抗氧化作用

以顽拗性TrichiliadregeanaSond.种子为材料,研究其胚轴的脱水敏感性与抗坏血酸的抗氧化作用。T.dregeana胚轴的脱水耐性随着脱水进程逐渐下降,50%的胚轴被脱水致死的含水量(W50)大约为0.16gH2O/gDW。在脱水过程中,胚轴的电解质渗漏速率逐渐增加,超氧物歧化酶(SOD)、抗坏血酸过氧化物酶(APX)、过氧化氢酶(CAT)、谷胱苷肽还原酶(GR)和脱氢抗坏血酸还原酶(DHAR)的活性下降,硫代巴比妥酸(TBA)-活性产物的含量增加。2.5~10.0mmol/L抗坏血酸处理能有效地增加胚轴的脱水耐性和SOD、APX、CAT和GR的活性,降低电解质渗漏速率和TBA活性产物的含量。结果表明,T.dregeana胚轴的脱水耐性与抗氧化酶的活性增加和脂质过氧化作用的降低密切相关。     

Salicylic Acid Application Mitigates Oxidative Damage and Improves the Growth Performance of Barley under Drought Stress

Drought is a severe environmental constraint, causing a significant reduction in crop productivity across the world. Salicylic acid (SA) is an important plant growth regulator that helps plants cope with the adverse effects induced by various abiotic stresses. The current study investigated the potential effects of SA on drought tolerance efficacy in two barley (Hordeum vulgare) genotypes, namely BARI barley 5 and BARI barley 7. Ten-day-old barley seedlings were exposed to drought stress by maintaining 7.5% soil moisture content in the absence or presence of 0.5, 1.0 and 1.5 mM SA. Drought exposure led to severe damage to both genotypes, as indicated by phenotypic aberrations and reduction of dry biomass. On the other hand, the application of SA to drought-stressed plants protected both barley genotypes from the adverse effects of drought, which was reflected in the improvement of phenotypes and biomass production. SA supplementation improved relative water content and proline levels in drought-stressed barley genotypes, indicating the osmotic adjustment functions of SA under water-deficit conditions. Drought stress induced the accumulation of reactive oxygen species (ROS), such as hydrogen peroxide (H₂O₂) and superoxide (O₂ ^•− ), and the lipid peroxidation product malondialdehyde (MDA) in the leaves of barley plants. Exogenous supply of SA reduced oxidative damage by restricting the accumulation of ROS through the stimulation of the activities of key antioxidant enzymes, including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) and glutathione peroxidase (GPX). Among the three-applied concentrations of SA, 0.5 mM SA exhibited better mitigating effects against drought stress considering the phenotypic performance and biochemical data. Furthermore, BARI barley 5 showed better performance under drought stress than BARI barley 7 in the presence of SA application. Collectively, our results suggest that SA played a crucial role in improving water status and antioxidant defense strategy to protect barley plants from the deleterious effects of water deficiency.     

Morphological changes and antioxidant defence systems in soybean genotypes as affected by salt stress

Abstract

The present investigation was conducted to evaluate salt tolerance in nine genotypes of soybean (Glycine max L.). Ten-day-old seedlings, grown hydroponically, were treated with 0, 25, 50, 75, 100, 125 and 150 mM NaCl for five days. Growth, lipid peroxidation and antioxidant enzyme activities were evaluated. Growth, measured in terms of length, fresh weight and dry weight of plants, was drastically reduced in PK-416, while there was little effect of NaCl treatment on Pusa-37 genotype of soybean. A high level of lipid peroxidation was observed in PK-416 as indicated by increased level of malondialdehyde. Activities of superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase were maximum in Pusa-37 where 9-fold, 1-fold, 5-fold and 6-fold increases over control were observed, respectively. The results suggested that PK-416 and Pusa-37 are salt-sensitive and salt-tolerant genotypes of soybean, respectively, and antioxidant defence systems involved in conferring the sensitiveness and tolerance in these genotypes.     

Antioxidant gene-enzyme responses in Medicago truncatula genotypes with different degree of sensitivity to salinity

Antioxidant responses and nodule function of Medicago truncatula genotypes differing in salt tolerance were studied. Salinity effects on nodules were analysed on key nitrogen fixation proteins such as nitrogenase and leghaemoglobin as well as estimating lipid peroxidation levels, and were found more dramatic in the salt-sensitive genotype. Antioxidant enzyme assays for catalase (CAT, EC 1.11.1.6), superoxide dismutase (EC 1.15.1.1), ascorbate peroxidase (EC 1.11.1.11) and guaiacol peroxidase (EC 1.11.1.7) were analysed in nodules, roots and leaves treated with increasing concentrations of NaCl for 24 and 48 h. Symbiosis tolerance level, depending essentially on plant genotype, was closely correlated with differences of enzyme activities, which increased in response to salt stress in nodules (except CAT) and roots, whereas a complex pattern was observed in leaves. Gene expression responses were generally correlated with enzymatic activities in 24-h treated roots in all genotypes. This correlation was lost after 48 h of treatment for the sensitive and the reference genotypes, but it remained positively significant for the tolerant one that manifested a high induction for all tested genes after 48 h of treatment. Indeed, tolerance behaviour could be related to the induction of antioxidant genes in plant roots, leading to more efficient enzyme stimulation and protection. High induction of CAT gene was also distinct in roots of the tolerant genotype and merits further consideration. Thus, part of the salinity tolerance in M. truncatula is related to induction and sustained expression of highly regulated antioxidant mechanisms.     

Salinity up-regulates the antioxidative system in root mitochondria and peroxisomes of the wild salt-tolerant tomato species Lycopersicon pennellii

The effect of salinity on the antioxidative system of root mitochondria and peroxisomes of a cultivated tomato Lycopersicon esculentum (Lem) and its wild salt-tolerant related species L. pennellii (Lpa) was studied. Salt stress induced oxidative stress in Lem mitochondria, as indicated by the increased levels of lipid peroxidation and H(2)O(2). These changes were associated with decreased activities of superoxide dismutase (SOD) and guaiacol peroxidases (POD) and contents of ascorbate (ASC) and glutathione (GSH). By contrast, in mitochondria of salt-treated Lpa plants both H(2)O(2) and lipid peroxidation levels decreased while the levels of ASC and GSH and activities of SOD, several isoforms of ascorbate peroxidase (APX), and POD increased. Similarly to mitochondria, peroxisomes isolated from roots of salt-treated Lpa plants exhibited also decreased levels of lipid peroxidation and H(2)O(2) and increased SOD, ascorbate peroxidase (APX), and catalase (CAT) activities. In spite of the fact that salt stress decreased activities of antioxidant enzymes in Lem peroxisome, oxidative stress was not evident in these organelles.     

Comparison of resistance to drought of three bean cultivars

The aim of the present work was to evaluate oxidative stress and plant antioxidant system of three contrasting bean (Phaseolus vulgaris L.) genotypes in the response to drought. Drought was imposed 14 d after emergence, by withholding water, until leaf relative water content reached 65 %. Water stress increased lipid peroxidation (LPO), membrane injury index, H₂O₂ and OH^⋅ production in leaves of stressed plants. Activities of the antioxidative enzymes superoxide dismutase (SOD) and ascorbate peroxidase (APOX) increased significantly under water stress in all the studied cultivars, while catalase (CAT) increased in cvs. Plovdiv 10 and Prelom, but decreased in cv. Dobrudjanski ran. Furthermore cv. Plovdiv 10 which had the highest APOX and CAT activities also showed the lowest increase in H₂O₂ and OH^⋅ production and LPO while cv. Dobrudjanski ran showed the lowest increases (and often the lowest values) in the antioxidant enzyme activities and the highest increases of H₂O₂ and OH^⋅ production, and LPO. On the basis of the data obtained we could specify cv. Plovdiv 10 and cv. Prelom as drought tolerant and cv. Dobrudjanski ran as a drought sensitive.     

Heat Stress-Induced Cell Death, Changes in Antioxidants, Lipid Peroxidation, and Protease Activity in Wheat Leaves

Six wheat genotypes were evaluated for heat tolerance in terms of seedling growth, antioxidant response and cell death. Based on the heat susceptibility index (HSI), response of the genotypes varied from heat tolerant (Inqilab-91) to heat sensitive (Sitta) along with moderately tolerant (Nesser and Sarsabz) and sensitive (Fareed and FD-83). Heat stress-induced programmed cell death (probably necrosis) in wheat leaves was evident by DNA smear. MDA content increased above twofold in most of genotypes under heat stress, with the lowest increase in the heat-tolerant genotype Nesser. Catalase activity diminished under heat stress in all genotypes. Peroxidase, superoxide dismutase (SOD), protease, and ascorbate peroxidase (APX) activities increased under heat stress. Apparently, heat stress-induced reduction in catalase activity was compensated by a parallel increase in peroxidases to quench H₂O₂. Heat stress-induced decrease (%) in catalase and increase in protease activities showed significant positive correlations, whereas increase (%) in APX activity showed a significant negative correlation with HSI or relative heat tolerance of genotypes. All these correlations signify that catalase, protease and ascorbate peroxidase can be used efficiently as biochemical markers to assess the relative heat stress tolerance of wheat genotypes at the seedling stage. In conclusion, using a multiparametric approach involving morphophysiological and biochemical assays, the sensitivity of wheat genotypes to heat stress could be evaluated to a sufficient level of certainty at the seedling stage.     

Modulation of symbiotic efficiency and nodular antioxidant enzyme activities in two <Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> genotypes under salinity

To analyse nodular expression of antioxidant enzymes depending on plant genotype and salinity, two Phaseolus vulgaris genotypes, tolerant BAT477 and sensitive COCOT, were inoculated with the reference strain Rhizobium tropici CIAT899 and grown under 25 and 50 mM NaCl. Plant growth, nodulation and nitrogen fixing activity measured by the acetylene reducing activity (ARA) as an indicator of nitrogenase (E.C. 1.7.9.92) activity were more affected by salt concentrations in COCOT than in BAT477, particularly with 50 mM NaCl. Electrophoresis analysis of antioxidant enzymes in nodules, roots and free-living rhizobia showed that only catalase (CAT E.C. 1.11.1.6) isoenzymes varied with genotype. The sensitive genotype showed lower antioxidant enzyme activities than tolerant genotype and it was more affected by salinity. In the tolerant genotype catalase and ascorbate peroxidase (APX, E.C. 1.11.1.11) were inhibited by salt stress, whereas superoxide dismutase (SOD, E.C. 1.15.1.1) and peroxidase (POX, E.C. 1.11.1.7) were activated by salinity. Statistical analysis allowed suggesting that tolerance to salinity is associated with a differential regulation of distinct superoxide dismutase and peroxidase activities.     

Physiological and biochemical traits of drought tolerance in Argania spinosa

The objective of this study was to understand and characterize the physiological and biochemical tolerance mechanisms of Argania spinosa under drought stress for selection tolerant ecotypes. Significant differences were observed among ecotypes in indices of leaf water status studied: stomatal conductance (g_s), predawn leaf water potential (Ψ_pd) and leaf relative water content. There was a significant decrease in these physiological traits with increasing degree of drought stress in all ecotypes. Drought stress significantly increased endogenous H₂O₂ and lipid peroxidation. Moderate and severe drought stress increased significantly the catalase, superoxide dismutase, peroxidase, polyphenoloxidase and lipoxygenase activities, depending on time. Their constitutive activities were higher in inland ecotypes than in coastal ecotypes. According to canonical discriminant analysis, the inland ecotypes were essentially distinguished from the coastal ecotypes by the following physiological and biochemical traits: Ψ_pd, g_s, polyphenol oxidase, superoxide dismutase and malonyldialdehyde. Inland ecotypes seem to be more tolerant to drought stress than coastal ecotypes.     

Up-regulation of the leaf mitochondrial and peroxisomal antioxidative systems in response to salt-induced oxidative stress in the wild salt-tolerant tomato species Lycopersicon pennellii

The response of the antioxidative systems of leaf cell mitochondria and peroxisomes of the cultivated tomato Lycopersicon esculentum (Lem) and its wild salt-tolerant related species Lycopersicon pennellii (Lpa) to NaCl 100 mM stress was investigated. Salt-dependent oxidative stress was evident in Lem mitochondria as indicated by their raised levels of lipid peroxidation and H2O2 content whereas their reduced ascorbate and reduced glutathione contents decreased. Concomitantly, SOD activity decreased whereas APX and GPX activities remained at control level. In contrast, the mitochondria of salt-treated Lpa did not exhibit salt-induced oxidative stress. In their case salinity induced an increase in the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and glutathione-dependent peroxidase (GPX). Lpa peroxisomes exhibited increased SOD, APX, MDHAR and catalase activity and their lipid peroxidation and H2O2 levels were not affected by the salt treatment. The activities of all these enzymes remained at control level in peroxisomes of salt-treated Lem plants. The salt-induced increase in the antioxidant enzyme activities in the Lpa plants conferred cross-tolerance towards enhanced mitochondrial and peroxisomal reactive oxygen species production imposed by salicylhydroxamic acid (SHAM) and 3-amino-1,2,4-triazole (3-AT), respectively.