Effect of nitric oxide and putrescine on antioxidative responses under NaCl stress in chickpea plants

Chickpea plants were subjected to salt stress for 48 h with 100 mM NaCl, after 50 days of growth. Other batches of plants were simultaneously treated with 0.2 mM sodium nitroprusside (NO donor) or 0.5 mM putrescine (polyamine) to examine their antioxidant effects. Sodium chloride stress adversely affected the relative water content (RWC), electrolyte leakage and lipid peroxidation in leaves. Sodium nitroprusside and putrescine could completely ameliorate the toxic effects of salt stress on electrolyte leakage and lipid peroxidation and partially on RWC. No significant decline in chlorophyll content under salt stress as well as with other treatments was observed. Sodium chloride stress activated the antioxidant defense system by increasing the activities of peroxidase (POX), catalase (CAT) superoxide dismutase (SOD) and ascorbate peroxidase (APX). However no significant effect was observed on glutathione reductase (GR) and dehydro ascorbate reductase (DHAR) activities. Both putrescine and NO had a positive effect on antioxidant enzymes under salt stress. Putrescine was more effective in scavenging superoxide radical as it increased the SOD activity under salt stress whereas nitric oxide was effective in hydrolyzing H₂O₂ by increasing the activities of CAT, POX and APX under salt stress.     

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.     

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.     

Effect of short-term salt stress on oxidative stress markers and antioxidant enzymes activity in tocopherol-deficient Arabidopsis thaliana plants

Changes of carotenoids and anthocyanins content, lipid peroxidation, and activity of antioxidant enzymes were studied in wild type and tocopherol-deficient lines vte1 and vte4 of Arabidopsis thaliana subjected to 200 mM NaCI during 24 h. The salt stress enhanced the intensity of lipid peroxidation to different extent in all three plant lines. Salt stress resulted in an increase of carotenoid content and activity of catalase, ascorbate peroxidase, guaiacol peroxidase and glutathione reductase in wild type and tocopherol-deficient vte1 mutant. However, the increase in anthocyanins concentration was observed in vte1 mutants only. In vte4 mutant, which contain gamma-tocopherol instead of alpha-tocopherol, the response to salt stress occurred via coordinative action of superoxide dismutase and enzymes of ascorbate-glutathione cycle, in particular, ascorbate peroxidase, glutathione reductase, dehydroascorbate reductase, and glutathione-S-transferase. It can be concluded, that salt stress was accompanied by oxidative stress in three studied lines, however different mechanisms involved in adaptation of wild type and tocopherol-deficient lines to salt stress.     

Effect of flooding on the activities of some enzymes of activated oxygen metabolism,the levels of antioxidants,and lipid peroxidation in senescing tobacco leaves

Effects of flooding on the activities of some enzymes of activated oxygen metabolism, the levels of antioxidants, and lipid peroxidation in senescing leaves of tobacco were investigated. As judged by the decrease in chlorophyll and protein levels, flooding accelerated the senescence of tobacco leaves. Total peroxide and the lipid peroxidation product, malondialdehyde, increased in both control and flooding-treated leaves with increasing duration of the experiment. Throughout the duration of the experiment, flooded leaves had higher levels of total peroxide and malondialdehyde than did control leaves. Flooding resulted in an increase in peroxidase and ascorbate peroxidase activities and a reduction of superoxide dismutase activity in the senescing leaves. Glycolate oxidase, catalase, and glutathione reductase activities were not affected by flooding. Flooding increased the levels of total ascorbate and dehydroascorbate. Total glutathione, reduced form glutathione, or oxidized glutathione levels in flooded leaves were lower than in control leaves during the first two days of the experiment, but were higher than in control leaves at the later stage of the experiment. Our work suggests that senescence of tobacco induced by flooding may be a consequence of lipid peroxidation possibly controlled by superoxide dismutase activity. Our results also suggest that increased rates of hydrogen peroxide in leaves of flooded plants could lead to increased capacities of the scavenging system of hydrogen peroxide.Abbreviations GSH reduced form glutathione - GSSG oxidized form glutathione - GSSG reductase glutathione reductase - MDA malondialdehyde - SOD superoxide dismutase     

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.     

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.     

Hepatoprotective and antioxidant property of Andrographis paniculata (Nees) in BHC induced liver damage in mice

Andrographis paniculata (AP) treatment prevents BHC induced increase in the activities of enzymes y-Glutamyl transpeptidase, glutathione-S-transferase and lipid peroxidation. The activities of antioxidant enzymes like superoxide dismutase, catalase, glutathione peroxidase and the levels of glutathione were decreased following BHC effect. Administration of AP showed protective effects in the activity of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase as well the level of glutathione. The activity of lipid peroxidase was also decreased. The result indicate antioxidant and hepatoprotective action of A. paniculata.     

Effects of piperine on antioxidant pathways in tissues from normal and streptozotocin-induced diabetic rats

Using diabetes mellitus as a model of oxidative damage, this study investigated whether subacute treatment (10 mg/kg/day, intraperitoneally for 14 days) with the compound piperine would protect against diabetes-induced oxidative stress in 30-day streptozotocin-induced diabetic Sprague-Dawley rats. Liver, kidney, brain, and heart were assayed for degree of lipid peroxidation, reduced and oxidized glutathione (GSH and GSSG, respectively) content, and activities of the free-radical detoxifying enzymes catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase. Piperine treatment of normal rats enhanced hepatic GSSG concentration by 100% and decreased renal GSH concentration by 35% and renal glutathione reductase activity by 25% when compared to normal controls. All tissues from diabetic animals exhibited disturbances in antioxidant defense when compared with normal controls. Treatment with piperine reversed the diabetic effects on GSSG concentration in brain, on renal glutathione peroxidase and superoxide dismutase activities, and on cardiac glutathione reductase activity and lipid peroxidation. Piperine treatment did not reverse the effects of diabetes on hepatic GSH concentrations, lipid peroxidation, or glutathione peroxidase or catalase activities; on renal superoxide dismutase activity; or on cardiac glutathione peroxidase or catalase activities. These data indicate that subacute treatment with piperine for 14 days is only partially effective as an antioxidant therapy in diabetes.     

Effect of Arbuscular Mycorrhizal Inoculation on Salt-induced Nodule Senescence in <Emphasis Type="Italic">Cajanus cajan</Emphasis> (Pigeonpea)

Many physiological and biochemical plant processes affected by salt stress trigger premature nodule senescence and decrease their ability to fix nitrogen. The objective of this study was to evaluate the role of arbuscular mycorrhiza (AM) in moderating salt-induced premature nodule senescence in Cajanus cajan (L.) Millsp. Greenhouse experiments were conducted in which the plants were exposed to salinity stress of 4, 6, and 8 dSm⁻¹. Various parameters linked to nodule senescence were assessed at 80 days after sowing. Nodulation, leghemoglobin content, and nitrogenase enzyme activity measured as acetylene-reducing activity (ARA) were evaluated. Two groups of antioxidant enzymes were studied: (1) enzymes involved in the detoxification of O₂⁻ radicals and H₂O₂, namely, superoxide dismutase (SOD), catalase (CAT) and peroxidase (POX), and (2) enzymes that are important components of the ascorbate glutathione pathway responsible for the removal of H₂O₂, namely, glutathione reductase (GR) and ascorbate peroxidase (APOX). Exposure of plants to salinity stress enhanced nodule formation; however, nodule growth suffered remarkably and a marked decline in nodule biomass, relative permeability, and lipid peroxidation was observed. Leghemoglobin content and ARA were reduced under saline conditions. AM significantly improved nodulation, leghemoglobin content, and nitrogenase activity under salt stress. Activities of SOD, CAT, APOX, POX, and GR increased markedly in mycorrhizal-stressed plants. A synthesis of the evidence obtained in this study suggests a correlation between enhanced levels of antioxidant enzyme activities, reduced membrane permeability, reduced lipid peroxidation, and improved nitrogen-fixing efficiency of AM plants under stressed and unstressed conditions. These factors could be responsible for the protective effects of mycorrhiza against stress-induced premature nodule senescence.     

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.     

Antioxidative responses of Calendula officinalis under salinity conditions.

To gain a better insight into long-term salt-induced oxidative stress, some physiological parameters in marigold (Calendula officinalis L.) under 0, 50 and 100 mM NaCl were investigated. Salinity affected most of the considered parameters. High salinity caused reduction in growth parameters, lipid peroxidation and hydrogen peroxide accumulation. Under high salinity stress, a decrease in total glutathione and an increase in total ascorbate (AsA + DHA), accompanied with enhanced glutathione reductase (GR, EC 1.6.4.2) and ascorbate peroxidase (APX, EC 1.11.1.11) activities, were observed in leaves. In addition, salinity induced a decrease in superoxide dismutase (SOD, EC 1.15.1.1) and peroxidase (POX, EC 1.11.1.7) activities. The decrease in dehydroascorbate reductase (DHAR, EC 1.8.5.1) and monodehydroascorbate reductase (MDHAR, EC 1.6.5.4) activities suggests that other mechanisms play a major role in the regeneration of reduced ascorbate. The changes in catalase (CAT, EC 1.11.1.6) activities, both in roots and in leaves, may be important in H2O2 homeostasis.     

Response of the cultivated tomato and its wild salt-tolerant relative Lycopersicon pennellii to salt-dependent oxidative stress: The root antioxidative system

The response of the antioxidant system to salt stress was studied in the roots of the cultivated tomato Lycopersicon esculentum Mill. cv. M82 (Lem) and its wild salt-tolerant relative L. pennellii (Corr.) D'Arcy accession Atico (Lpa). Roots of control and salt (100 m M NaCl)-stressed plants were sampled at various times after commencement of salinization. A gradual increase in the membrane lipid peroxidation in salt-stressed root of Lem was accompanied with decreased activities of the antioxidant enzymes: superoxide dismutase (SOD; EC 1.15.1.1), catalase (CAT; EC 1.11.1.6), ascorbate peroxidase (APX; EC 1.11.1.11) and decreased contents of the antioxidants ascorbate and glutathione and their redox states. In contrast, increased activities of the SOD, CAT, APX, monodehydroascorbate reductase (MDHAR; EC 1.6.5.4), and increased contents of the reduced forms of ascorbate and glutathione and their redox states were found in salt-stressed roots of Lpa, in which the level of membrane lipid peroxidation remained unchanged. It seems that the better protection of Lpa roots from salt-induced oxidative damage results, at least partially, from the increased activity of their antioxidative system.     

Comparative lipid peroxidation,antioxidant defense systems and proline content in roots of two rice cultivars differing in salt tolerance

The changes in the activity of antioxidant enzymes such as superoxide dismutase (SOD: EC 1.15.1.1), catalase (CAT: EC 1.11.1.6), peroxidase (POX: EC 1.11.1.7), ascorbate peroxidase (APOX: EC 1.11.1.11) and glutathione reductase (GR: EC 1.6.4.2), free proline content, and the rate of lipid peroxidation level in terms of malondialdehyde (MDA) in roots of two rice cultivars (cvs.) differing in salt tolerance were investigated. Plants were subjected to three salt treatments, 0, 60, and 120 mol m⁻³ NaCl for 7 days. The results showed that activated oxygen species may play a role in cellular toxicity of NaCl and indicated differences in activation of antioxidant defense systems between the two cvs. The roots of both cultivars showed a decrease in GR activity with increase in salinity. CAT and APOX activities increased with increasing salt stress in roots of salt-tolerant cultivar Pokkali but decreased and showed no change, respectively, in roots of IR-28 cultivar. POX activity decreased with increasing NaCl concentrations in salt-tolerant Pokkali but increased in IR-28. SOD activity showed no change in roots of both cultivars under increasing salinity. MDA level in the roots increased under salt stress in sensitive IR-28 but showed no change in Pokkali. IR-28 produced higher amount of proline under salt stress than in Pokkali. Increasing NaCl concentration caused a reduction in root fresh weight of Pokkali and root dry weight of IR-28. The results indicate that improved tolerance to salt stress in root tissues of rice plants may be accomplished by increased capacity of antioxidative system.     

Antioxidant enzymatic systems in neuronal and glial cell-enriched fractions of rat brain during aging

The activities of Cu,Zn superoxide dismutase, glutathione peroxidase, catalase and glutathione reductase in neuronal and glial cell-enriched fractions obtained from the cerebral cortex of rat brain during aging (15, 30, 90, 350, 750 days of age) were assayed. Our results showed that glutathione peroxidase, catalase and glutathione reductase activities varied little during the examined periods. Only the Cu,Zn superoxide dismutase activity decreased notably from 15th to 750th day of age in both neuronal and glial cells, moreover the activities of all enzymes studied were always detected at lower levels in neuronal cells with respect to glial cells. In agreement with diminished SOD activity, the lipid peroxidation showed an elevated increase with aging; this fact is more evident in neuronal than in glial cells. In conclusion our data show that Cu,Zn superoxide dismutase is the most affected antioxidant enzymatic system of brain aging and it could be responsible for the increased lipid peroxidation in both cell types examined.A preliminary report of these results was presented at the 19th Meeting F.E.B.S. Rome July 2–7, 1989.     

Antioxidants and Manganese Deficiency in Needles of Norway Spruce (Picea abies L.) Trees

Chlorotic and green needles from Norway spruce (Picea abies L.) trees were sampled in the Calcareous Bavarian Alps in winter. The needles were used for analysis of the mineral and pigment contents, the levels of antioxidants (ascorbate, glutathione), and the activities of protective enzymes (superoxide dismutase, catalase, ascorbate peroxidase, monodehydroascorbate radical reductase, dehydroascorbate reductase, glutathione reductase). In addition, the activities of two respiratory enzymes (glucose-6-phosphate dehydrogenase, NAD-malate dehydrogenase), which might provide the NADPH necessary for functioning of the antioxidative system, were determined. We found that chlorotic needles were severely manganese deficient (3 to 6 micrograms Mn per gram dry weight as compared with up to 190 micrograms Mn per gram dry weight in green needles) but had a similar dry weight to fresh weight ratio, had a similar protein content, and showed no evidence for enhanced lipid peroxidation as compared with green needles. In chlorotic needles, the level of total ascorbate and the activities of superoxide dismutase, monodehydroascorbate radical reductase, NAD-malate dehydrogenase, and glucose-6-phosphate dehydrogenase were significantly increased, whereas the levels of ascorbate peroxidase, dehydroascorbate reductase, glutathione reductase, and glutathione were not affected. The ratio of ascorbate to dehydroascorbate was similar in both green and chlorotic needles. These results suggest that in spruce needles monodehydroascorbate radical reductase is the key enzyme involved in maintaining ascorbate in its reduced state. The reductant necessary for this process may have been supplied at the expense of photosynthate.     

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.     

Salt tolerance of barley induced by the root endophyte Piriformospora indica is associated with a strong increase in antioxidants

The root endophytic basidiomycete Piriformospora indica has been shown to increase resistance against biotic stress and tolerance to abiotic stress in many plants. Biochemical mechanisms underlying P. indica-mediated salt tolerance were studied in barley (Hordeum vulgare) with special focus on antioxidants. Physiological markers for salt stress, such as metabolic activity, fatty acid composition, lipid peroxidation, ascorbate concentration and activities of catalase, ascorbate peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase and glutathione reductase enzymes were assessed. Root colonization by P. indica increased plant growth and attenuated the NaCl-induced lipid peroxidation, metabolic heat efflux and fatty acid desaturation in leaves of the salt-sensitive barley cultivar Ingrid. The endophyte significantly elevated the amount of ascorbic acid and increased the activities of antioxidant enzymes in barley roots under salt stress conditions. Likewise, a sustained up-regulation of the antioxidative system was demonstrated in NaCl-treated roots of the salt-tolerant barley cultivar California Mariout, irrespective of plant colonization by P. indica. These findings suggest that antioxidants might play a role in both inherited and endophyte-mediated plant tolerance to salinity.     

Characterization of <Emphasis Type="Italic">Brassica juncea</Emphasis> antioxidant potential under salinity stress

Present study characterizes the anti-oxidative defense potential of four Brassica juncea varieties, Pusa Jaikisan, Varuna, RLM-198, and CS-52, differing in their ability to withstand salinity stress. 7-day-old seedlings raised in MS medium supplemented with 0, 50, 100, and 150 mM NaCl were used to monitor changes in the growth profile, level of stress marker molecules, and activities of important antioxidant enzymes. Increasing NaCl concentration resulted in a significant (P ≤ 0.05) reduction of shoot fresh and dry mass and vigor index in all the varieties tested. Maximum reduction in growth was recorded for RLM-198 while CS-52 maintained better growth characteristics. Varuna and RLM-198 exhibited a limited increase in superoxide dismutase, ascorbate peroxidase, and total peroxidase activity under increasing salinity. These varieties also recorded maximum salt stress-induced damage in terms of increased lipid peroxidation, H₂O₂ content, and electrolyte leakage. On the other hand, CS-52 recorded maximum proline accumulation with minimum levels of H₂O₂, electrolyte leakage, and malondialdehyde contents. With increasing salinity stress, CS-52 recorded maximal increase in the activity of antioxidant enzymes. However, catalase activity did not correlate with alterations in H₂O₂ levels under stress. Interestingly, a lower superoxide dismutase:ascorbate peroxidase ratio in CS-52 correlated with stress tolerance trait, while a comparatively higher superoxide dismutase:ascorbate peroxidase ratio in RLM-198 marked the susceptible nature of the variety. Our results propose that superoxide dismutase:ascorbate peroxidase ratio is the critical factor, determining the degree of stress tolerance in Brassica juncea.     

Oxidative stress is not related to the mode of action of herbicides that inhibit acetolactate synthase

Imazethapyr (IM) is an imidazolinone herbicide which inhibits the biosynthesis of branched chain amino acids, by blocking acetolactate synthase (ALS; EC 4.1.3.18), the first common enzyme of the pathway. To study new aspects of the mode of action of ALS-inhibiting herbicides, pea plants grown in hydroponic cultures were supplied with IM and were analysed with reference to the antioxidant system and oxidative markers. A slight lipid peroxidation was detected in leaves after IM treatment, but no changes were noted in electrolyte leakage or carbonyl content. The ascorbate pool of leaves was oxidized under IM treatment. The analysis of the antioxidant enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), catalase (CAT) and guaiacol peroxidase (GPX), showed that IM treatment only caused an enhancement of GPX activity in leaves. In roots, the herbicide caused a decrease in lipid peroxidation. The enhancement of the reduced glutathione content detected in IM-treated roots can be related to the detected increase of GR activity. The lack of more noticeable effects on antioxidant enzymatic activities could be explained by the inability of IM-treated plants to respond to oxidative stress with modifications in their protein synthesis. Our results suggest that oxidative stress is not related to the mode of action of ALS-inhibitors. The slight changes detected in the antioxidative status of treated plants are too secondary in time and intensity to be related to the lethality caused by ALS-inhibitors