Plasma-activated water (PAW) seed treatment is an emerging green technology that enhances plant germination and growth; however, its role in drought stress tolerance remains unclear. In this study, pea (Pisum sativum L.) seeds were treated with PAW (10 mg L⁻¹ nitrite, 30 mg L⁻¹ nitrate, pH 3.9), Zn-enriched PAW (PAW+Zn; 6 mg L⁻¹ H₂O₂, 19 mg L⁻¹ nitrite, 20 mg L⁻¹ nitrate, 14 mg L⁻¹ Zn, pH 4.7), distilled water, or Zn-enriched distilled water. Subsequently, three-week-old plants were subjected to osmotic stress using PEG8000 (20% w/v). PAW induced partial hilum opening and mild seed coat damage, while PA(W+Zn) increased nitric oxide accumulation. Both treatments enhanced nutrient bioavailability and shootward translocation, particularly of Zn and Fe. Under stress, PAW promoted the formation of larger but thinner leaves, indicating adaptive morphological responses. However, stomatal conductance, relative water content, photosynthesis, and starch accumulation remained unaffected. Unchanged proline levels and reduced soluble sugars suggest that classical osmotic acclimation was not induced by PAW treatments. Instead, both PAW and PA(W+Zn) increased abscisic acid (ABA) levels and PsDHN2 expression, indicating activation of ABA-dependent stress signalling, likely mediated by nitrate-, nitrite-, and H₂O₂-derived signals. Tissue-specific cytokinin responses and enhanced antioxidant enzyme activities (superoxide dismutase, catalase) further suggest the establishment of a primed state. Overall, PAW-based seed treatments induce complex physiological and molecular responses, with morphological, ionic, hormonal, and antioxidant processes contributing to stress adaptation in pea.

Plasma-activated water (PAW) seed treatment is an emerging green technology that enhances plant germination and growth; however, its role in drought stress tolerance remains unclear. In this study, pea (Pisum sativum L.) seeds were treated with PAW (10 mg L⁻¹ nitrite, 30 mg L⁻¹ nitrate, pH 3.9), Zinc (Zn)-enriched PAW (PA(W+Zn); 6 mg L⁻¹ hydrogen peroxide (H₂O₂), 19 mg L⁻¹ nitrite, 20 mg L⁻¹ nitrate, 14 mg L⁻¹ Zn, pH 4.7), distilled water (DW), or Zn-enriched DW. Subsequently, three-week-old plants were subjected to osmotic stress using polyethylene glycol 8000 (PEG8000) (20% w/v). PAW induced partial hilum opening and mild seed coat damage, while PA(W+Zn) increased nitric oxide (NO) accumulation. Both treatments enhanced nutrient levels and shootward translocation, particularly of Zn and iron (Fe). Under stress, PAW promoted the formation of larger but thinner leaves, indicating adaptive morphological responses. However, stomatal conductance, relative water content, photosynthesis, and starch accumulation remained unaffected. Unchanged proline levels and reduced soluble sugars suggest that classical osmotic acclimation was not induced by PAW treatments. Instead, both PAW and PA(W+Zn) increased abscisic acid (ABA) levels and PsDHN2 expression, indicating activation of ABA-dependent stress signalling, likely mediated by nitrate-, nitrite-, and H2O2-derived signals. Tissue-specific cytokinin (CK) responses and enhanced antioxidant enzyme activities (superoxide dismutase [SOD], catalase [CAT]) further suggest the establishment of a primed state. Overall, PAW-based seed treatments induce complex physiological and molecular responses involving ABA signalling, selected ion translocation, and antioxidant enzymes without significantly improved water status, stomatal regulation, or photosynthetic performance.

Glutathione transferases (GSTs, EC 2.5.1.18) are a diverse enzyme family involved in various cellular processes, regulated by several stimuli, including plant hormones (phytohormones). Additionally, GSTs can also influence hormone levels, as certain GSTs, particularly members of the Phi class GSTs (GSTFs) have been reported to directly bind small phytohormones (auxin, cytokinin, and salicylic acid). However, the structural aspects of these interactions remained unresolved. It has been documented that an Arabidopsis thaliana GSTF, AtGSTF2, possesses unique non-catalytic ligand-binding sites (L sites). This study focuses on the orthologous tomato (Solanum lycopersicum) GSTFs (SlGSTFs) and explores the connection between this non-catalytic ligand-binding function and phytohormones. Using modern in silico techniques, such as protein modelling by AlphaFold, molecular docking, and molecular dynamics (MD) simulations, we provide the first insights into the possible phytohormone-binding ability of SlGSTFs. In particular, SlGSTF5 shows significant potential for a novel phytohormone binding function, thereby broadening the potential roles of plant GSTs. Our work also includes a simple protocol for modelling and analysing protein-ligand interactions, offering valuable insights into the role of individual plant GSTs.

Nocturnal red light application affects defence-related enzymes in wheat, in particular antioxidants and glutathione transferases (GSTs), which are crucial for successful plant defence. In our study, we sought to answer the question of whether night-time illumination during anthesis induces detectable changes in the infection responses of wheat cultivars with different levels of Fusarium resistance. To address this question, we investigated a range of factors from yield parameters and membrane status to changes in enzyme activities and gene expression and its regulation. Nocturnal red light treatment increased the activities of superoxide dismutase, catalase, guaiacol-dependent peroxidase and GSTs. In parallel with increased activity of detoxification enzymes, a higher grain yield was observed in the more resistant wheat line during infection by Fusarium graminearum. Notably, GSTs, which are typically down-regulated in darkness, were strongly up-regulated by red light at night in the more susceptible cultivar, especially TaGSTU1B and TaGSTF5. In addition, an exceptionally high and light-dependent transcriptional activity of TaGSTF5 was detected in the sensitive line. Sequence analysis of the regulatory region of TaGSTF5 identified an additional GATA box, a circadian regulatory element, which may be responsible for the increased transcript levels. These results suggest that nocturnal red light can effectively enhance antioxidant and GST activity as part of the defence of wheat against Fusarium head blight, but this depends on the Fusarium resistance of the selected wheat genotypes.

The interaction between ethylene (ET) and light/dark cycles is complex and regulates plant growth, development and stress responses. While ET synthesis is influenced by circadian rhythms, light -especially red light- it can also affect ET-regulated processes, depending on the developmental stage and organ type. This study investigated the effects of nocturnal red light exposure on mature tomato plant leaves, using wild-type (WT) and ET-insensitive Never ripe (Nr) mutant. Red light application for one week at night did not significantly affect leaf biomass and area, but it altered structural traits such as leaf thickness and internode length, particularly in WT plants. Transcriptomic analyses indicated significant differences in gene expression between WT and Nr plants, particularly in genes related to photosynthesis, growth regulation and the circadian clock. Red light also modulated the expression of hormone-related genes and increased the levels of defence-related phytohormones (ET, salicylic acid, abscisic acid) as well as the activity of antioxidant enzymes (e.g. guaiacol peroxidase, glutathione S-transferase) in a manner dependent on ET in WT plants. Interestingly, although ET is involved in many of these processes, red light was also found to increase biotic stress resistance in Nr mutants, as evidenced by reduced Botrytis cinerea infection. This suggests that red light may activate defence pathways independently of ET. Our findings highlight the potential of red light as an environmentally friendly tool for improving crop disease resistance and emphasise the pivotal role of ET signalling, which can be regulated by specific light spectra, in plant’s defence reactions.

Plant glutathione peroxidase-like (GPXL) enzymes are thiol-based peroxidases that reduce H2O2 or hydroperoxides to water or alcohols using electrons principally from thioredoxin. Arabidopsis thaliana possesses eight isoenzymes (AtGPXL1−8) located in different plant organelles and have various roles in redox-dependent processes. The determination of the redox potential of 6-day-old T-DNA insertional mutants (Atgpxl1–Atgpxl8) using a cytosolic redox-sensitive fluorescent probe (roGFP2) uncovered more oxidized redox status in the shoot and/or root of the untreated mutants, except for Atgpxl5. To investigate the involvement of AtGPXLs in the growth and abiotic stress responses of seedlings, the 4-day-old Atgpxls were exposed to salt and osmotic stresses for two weeks. The evaluation of the reactive oxygen species (ROS) levels of untreated 18-day-old plants using fluorescent microscopy revealed the elevated accumulation of total ROS in the shoots and, in some cases, the roots of the mutants. Regarding the growth of roots, both the length of primary roots and/or the number of lateral roots were affected by the mutation of AtGPXLs. A strong negative correlation was observed between the ROS level of wild type shoots and the development of lateral roots, but it was altered in mutants, while in the case of Atgpxl1, Atgpxl5, and Atgpxl7 seedlings, it disappeared; in other mutants (Atgpxl4, Atgpxl6, and Atgpxl8), the correlation became stronger. Our analysis underpins the discrete role of AtGPXL enzymes in controlling the growth and development of plants by fine tuning the ROS contents and redox status in an organ-specific way. Differences in root phenotype and metabolic activity between Atgpxl mutants and wild type plants highlight the essential role of AtGPXLs in ROS processing to support growth, which is particularly evident when one GPXL isoenzyme is absent or its activity is reduced, both under normal and abiotic stress conditions.

This study explores the long-term effects of nocturnal red light treatment on tomato plants, focusing on photosynthesis, metabolism, and defence mechanisms. The impact of red light treatment applied at night to both young and old leaves at various times of day was investigated. The results showed that, after three weeks, nocturnal red light treatment improved photosynthetic efficiency in both upper and lower leaves, particularly in the morning and at noon. This enhancement in photosynthesis was associated with higher CO2 assimilation. Interestingly, older leaves, which usually demonstrate reduced photosynthetic activity, also benefited from red light exposure. Additionally, red light treatment resulted in significant changes to the accumulation of starch and sugars. Higher levels of starch were found in the leaves in the afternoon, alongside increased levels of sucrose in both leaves. Metabolomics analysis revealed that the level of several defence-related metabolites, including 4-guanidinobutyric acid, fucose and quinic acid, increased following exposure to red light. This suggests that red light applied at night could have a priming effect, enhancing defence against pathogens. Conversely, the levels of some metabolites, such as myo-inositol and N-acetylaspartate, decreased, indicating adjustments in plant stress responses. Red light influenced plant height and leaf area and enhanced callose content in older leaves. Moreover, red light can hard plants against fungal pathogens, such as Botrytis cinerea. These results suggest that exposure to red light at night is an effective, environmentally friendly approach to enhance the resilience of tomato plants and optimise greenhouse farming practices, particularly through supplemental or interlighting systems.

Osmotic stress induces the overproduction of reactive oxygen species (ROS), leading to oxidative damage to cellular components, with lipid peroxidation being one of the most harmful consequences. Glutathione transferases (GSTs; E.C. 2.5.1.18) play a key role in detoxifying harmful compounds through their glutathione transferase and glutathione peroxidase (GPOX) activities. To investigate the specific roles of GSTs in tomato responses to osmotic stress, two cultivars of Solanum lycopersicum (cv. Mobil and Moneymaker) were treated with increasing concentrations of polyethylene glycol (PEG 6000) over several days. Both cultivars exhibited similar symptoms of severe stress, but their enzymatic activity and the expression of GST genes differed. These gene expression patterns indicate that a specific group of tomato GSTs, including certain Tau and Theta class GSTs (GSTUs and GSTTs), may play an important role in defending against osmotic stress across various tomato varieties. Additionally, the gene expression profiles of the two cultivars likely correspond to the differences observed in their enzymatic activity: elevated GST and GPOX activity in Mobil, but in Moneymaker, solely the GPOX activity was increased. Particular focus was given to the tomato Theta class GSTs (SlGSTTs), known for their GPOX activity and substrate preference for lipid peroxides. Marked upregulation was observed of SlGSTT genes under osmotic stress. Protein modeling and molecular docking suggest that SlGSTT2 and SlGSTT3 isoenzymes may contribute to membrane protection by scavenging different lipid peroxidation products in the peroxisomes.

Plant infections caused by fungi lead to significant crop losses worldwide every year. This study aims to better understand the plant defence mechanisms regulated by red light, in particular, the effects of red light at night when most phytopathogens are highly infectious. Our results showed that superoxide production significantly increased immediately after red light exposure and, together with hydrogen peroxide levels, was highest at dawn after 30 min of nocturnal red-light treatment. In parallel, red-light-induced expression and increased the activities of several antioxidant enzymes. The nocturnal red light did not affect salicylic acid but increased jasmonic acid levels immediately after illumination, whereas abscisic acid levels increased 3 h after nocturnal red-light exposure at dawn. Based on the RNAseq data, red light immediately increased the transcription of several chloroplastic chlorophyll a-b binding protein and circadian rhythm-related genes, such as Constans 1, CONSTANS interacting protein 1 and zinc finger protein CONSTANS-LIKE 10. In addition, the levels of several transcription factors were also increased after red light exposure, such as the DOF zinc finger protein and a MYB transcription factor involved in the regulation of circadian rhythms and defence responses in tomato. In addition to identifying these key transcription factors in tomato, the application of red light at night for one week not only reactivated key antioxidant enzymes at the gene and enzyme activity level at dawn but also contributed to a more efficient and successful defence against Botrytis cinerea infection.

Salicylic acid (SA) plays a crucial role not only in defence against pathogen attacks, but also in abiotic stress responses. Recently, some key steps of SA signalling outlined the importance of redox state-dependent processes. This study explores the role of glutathione transferases (GSTs) in the transcriptional reprogramming of redox status-related genes in seven-day-old wild type and Atgst mutant Arabidopsis thaliana plants. The timing of redox changes, detected by the redox-sensitive green fluorescent protein (roGFP2), differed in wild type roots treated with 10 μM or 100 μM SA. Our results verified how the applied SA concentrations had different effect on the expression of oxidative stress- and redox-related genes, among them on the expression of AtGSTF8 and AtGSTU19 genes. Lower vitality and less negative E GSH values were specific characteristics of the Atgst mutants compared to the wild type plants throughout the experiment. Changes in the redox potential were only modest in the mutants after SA treatments. A slightly modified gene expression pattern was observed in control conditions and after 1 h of SA treatments in Atgst mutants compared to Col-0 roots. These data originating from the whole roots provide indirect evidence for the role of the investigated AtGSTF8 and AtGSTU19 isoenzymes in the transduction of the redox signal. Our results demonstrate that the investigated Arabidopsis GSTs have a role in maintaining the levels of reactive oxygen species- and redox homeostasis and are involved in transcriptional reprogramming in the roots.

Glutathione transferases (GSTs) are one of the most versatile multigenic enzyme superfamilies. In our experiments, the involvement of the genotype-specific induction of GST genes and glutathione- or redox-related genes in pathways regulating salt-stress tolerance was examined in tomato cultivars (Solanum lycopersicum Moneymaker, Mobil, and Elán F1). The growth of the Mobil plants was adversely affected during salt stress (100 mM of NaCl), which might be the result of lowered glutathione and ascorbate levels, a more positive glutathione redox potential (EGSH), and reduced glutathione reductase (GR) and GST activities. In contrast, the Moneymaker and Elán F1 cultivars were able to restore their growth and exhibited higher GR and inducible GST activities, as well as elevated, non-enzymatic antioxidant levels, indicating their enhanced salt tolerance. Furthermore, the expression patterns of GR, selected GST, and transcription factor genes differed significantly among the three cultivars, highlighting the distinct regulatory mechanisms of the tomato genotypes during salt stress. The correlations between EGSH and gene expression data revealed several robust, cultivar-specific associations, underscoring the complexity of the stress response mechanism in tomatoes. Our results support the cultivar-specific roles of distinct GST genes during the salt-stress response, which, along with WRKY3, WRKY72, DREB1, and DREB2, are important players in shaping the redox status and the development of a more efficient stress tolerance in tomatoes.

Glutathione transferases (GSTs) are enzymes that catalyse modifications and conjugations of a range of organic and often cytotoxic compounds. GST enzymes with many functions-such as their conjugation activity against herbicides and their metabolites-can be induced and show light and circadian determination. The enzyme family, which is widespread in its function, also shows great diversity in its structure, which has been linked to its enzyme kinetic characteristics and physiological role at many points. In this study, we aimed to find out the role of different glutathione transferases in the herbicide responses to flumioxazin, as well as to determine how the antioxidant and detoxification response to herbicide treatment changes in the presence and absence of light. One of the herbicide treatments was carried out during the light period in the morning (9:00 a.m.), and the other before the end of the dark period (4:00 a.m.). The decrease in the maximal quantum efficiency of PS II and the reduction in the chlorophyll concentration supported the effect of the herbicide on Papaver rhoeas. In the guaiacol peroxidase POD and GST activity, there were large differences between the cultivated plants and the weed; both enzyme activities were much higher in the case of wheat. According to the activity of the antioxidant defence enzymes and GST gene expression data, the application of the photosynthesis inhibitor herbicide, flumioxazin, in the dark could allow the wheat antioxidant defence to switch on before the herbicide effect could appear in the light period. Phi and tau group GSTs were transcriptionally upregulated by the treatments in wheat plants (especially TaGSTU1B), while fewer changes were detectable in poppy weed (PrGSTU4). Based on our results, in the background of the greater and more successful response to flumioxazin may be-among other things-the higher degree of variability of the GSTU genes of wheat compared to poppies.

Fusarium graminearum and F. culmorum cause the most widespread wheat disease Fusarium head blight (FHB). The present study describes that the Fusarium inoculation of the wheat spikes caused systemic changes in the key elements of the antioxidant/detoxification defence system in the flag leaf during the grain filling period in wheat lines differing in biotic stress susceptibility to explore changes in some components of the response. According to our data, the inoculation with both F. graminearum and F. culmorum at the anthesis changed significantly the activities of superoxide dismutase (SOD) and guaiacol peroxidase (POD) enzymes, as well as the glutathione transferase (GST) activity in the flag leaves of the selected wheat lines approx. two weeks later after the infection. In silico approach supported the expressional up-regulation of various GST genes upon Fusarium infection. Based on our results, GST sequences TaGSTF26 and TaGSTU120 were among the series of important stress response genes, which were transcriptionally up-regulated, thus possibly playing a role in the systemic response to Fusarium infection, where TaGSTF26 might have an important role in the successful defence. These GSTs can serve as effective markers of the detoxification process for breeders and plant protection in the future.

Plant defense responses against Fusarium infection can be controlled by light. In this study, the effects of nocturnal red light were investigated on glutathione transferases (GSTs) in the leaves of the moderate- and high-Fusarium resistant wheat cultivars, GK Ígéret and GK Arató, respectively. GST activity increased in the light phase during the day, while it decreased after midnight. Since GST activity was lowest at midnight, we examined whether red light application at midnight could prevent the night-time drop in enzyme activity. We found that 15-min-long nocturnal red light application was effective to increase GST activity at dawn. The effects of red light pretreatments on GST expression and activity, as well as the oxidative stress induced by fumonisin B1 (FB1), were investigated. FB1 exposure increased GST activity and the expression of GST genes at dawn but nocturnal red light application in combination with the mycotoxin also increased GST activity and the transcript levels of the selected GSTs in the resistant GK Arató. In addition to its effects on GSTs, it was discovered that, depending on the degree of tolerance, nocturnal red light increased the activity of the major antioxidant enzymes at dawn in both of the chosen wheat genotypes. These decreased FB1’s oxidative stress-causing actions, resulting in lower lipid peroxidation and less cell viability loss when exposed to the mycotoxin. Pretreatment with nocturnal red light enhanced the activity of GST and antioxidant enzymes in wheat plant leaves, contributing to FB1 detoxification and reducing oxidative stress.

Reactive oxygen species (ROS), antioxidants and their reduction-oxidation (redox) states all contribute to the redox homeostasis, but glutathione is considered to be the master regulator of it. We aimed to understand the relationship between the redox potential and the diverse glutathione transferase (GST) enzyme family by comparing the stress responses of two tomato cultivars (Solanum lycopersicum 'Moneymaker' and 'Ailsa Craig'). Four-week-old plants were treated by two concentrations of mannitol, NaCl and salicylic acid. The lower H2O2 and malondialdehyde contents indicated higher stress tolerance of 'Moneymaker'. The redox status of roots was characterized by measuring the reduced and oxidized form of ascorbate and glutathione spectrophotometrically after 24 h. The redox potential of 'Ailsa Craig' was more oxidized compared to 'Moneymaker' even under control conditions and became more positive due to treatments. High-throughput quantitative real-time PCR revealed that besides overall higher expression levels, SlGSTs were activated more efficiently in 'Moneymaker' due to stresses, resulting in generally higher GST and glutathione peroxidase activities compared to 'Ailsa Craig'. The expression level of SlGSTs correlated differently, however Pearson's correlation analysis showed usually strong positive correlation between SlGST transcription and glutathione redox potential. The possible redox regulation of SlGST expressions was discussed.

Light is essential for plant life. It provides a source of energy through photosynthesis and regulates plant growth and development and other cellular processes, such as by controlling the endogenous circadian clock. Light intensity, quality, duration and timing are all important determinants of plant responses, especially to biotic stress. Red light can positively influence plant defence mechanisms against different pathogens, but the molecular mechanism behind this phenomenon is not fully understood. Therefore, we reviewed the impact of red light on plant biotic stress responses against viruses, bacteria, fungi and nematodes, with a focus on the physiological effects of red light treatment and hormonal crosstalk under biotic stress in plants. We found evidence suggesting that exposing plants to red light increases levels of salicylic acid (SA) and induces SA signalling mediating the production of reactive oxygen species, with substantial differences between species and plant organs. Such changes in SA levels could be vital for plants to survive infections. Therefore, the application of red light provides a multidimensional aspect to developing innovative and environmentally friendly approaches to plant and crop disease management.

Glutathione transferases (GSTs) play a crucial role in detoxification processes due to the fact of their glutathione (GSH) conjugating activity, and through glutathione peroxidase or dehydroascorbate reductase (DHAR) activities, they influence the redox state of GSH and ascorbate (AsA). The plant-specific tau (GSTU) group is the largest class of Arabidopsis GSTs, and their members are involved in responses to different abiotic stresses. We investigated the effect of salt stress on two-week-old Arabidopsis thaliana wild-type (Col-0), Atgstu19 and Atgstu24 mutant plants after applying 150 mM NaCl for two days. The Atgstu19 seedlings had lower GST activity and vitality both under control conditions and after salt stress than the wild-type, but the level of total ROS was similar to the Col-0 plants. The GST activity of the knockout Atgstu24 mutant was even higher under control conditions compared to the Col-0 plants, while the ROS level and its vitality did not differ significantly from the wild-type. Analysis of the AtGSTU expression pattern revealed that the mutation in a single AtGSTU gene was accompanied by the up- and downregulation of several other AtGSTUs. Moreover, elevated AsA and GSH levels, an altered GSH redox potential and increased DHAR and glutathione reductase activities could help to compensate for the mutation of AtGSTU genes. The observed changes in the mutants suggest that the investigated isoenzymes influence the redox homeostasis under control conditions and after NaCl treatment in Arabidopsis seedlings. These data indicate for the first time the more general role of a temporary shift of redox status as part of GST mechanisms and regulation.

The Plant Molecular Physiology textbook is designed to introduce undergraduate students into the life of plants. First, the genetic basis of the growth and development of plants is described. The first chapter explores the molecular regulatory factors with high importance in functioning of the genome and controlling the expression of genes. The second chapter introduces the specific organisation of plant cells and cellular organelles. Following chapters discuss the demand of plants for minerals, the uptake and transport of water and nutrients, and the mechanisms and significance of photosynthesis. The main endogenous factors (plant hormones) and the most important exogenous signal (light) and related signalling events affecting plant life and adaptation are also discussed. The plant-specific aspects of these biological processes, their regulatory and signalling mechanisms are also described. Then, the key points of plant ontogenesis including growth and development, reproduction and senescence are highlighted.

The presence or absence of light is one of the most significant environmental factors affecting plant growth and defence. Therefore, the selection of the most appropriate time of application may maximize the benefits of photosynthetic inhibitors. In this work, the concentration and daytime or night-time-dependent effects of bentazon were tested in soybean and common ragweed. The recommended dose (1440 g ha−1) and also half the recommended dose significantly reduced the maximum quantum yield (Fv/Fm) and increased H2O2 levels in common ragweed. Interestingly, bentazon did not change Fv/Fm in soybean. The activity of superoxide dismutase changed in a dose-dependent manner only in common ragweed. The activity of ascorbate peroxidase, catalase and glutathione S-transferase (GST), as well as the contents of ascorbate (AsA) and glutathione (GSH) did not change significantly in this plant species. In soybean, alterations in H2O2 levels were lower but GST and APX activity, as well as AsA and GSH levels were higher compared to common ragweed. At the same time, the rate of lipid peroxidation and ion leakage increased upon bentazon, and were higher in the light phase-treated leaves in the case of both plant species. These results can contribute to optimizing the effects and uses of herbicides in agriculture.

The detoxification of harmful metabolites can determine the effectiveness of plant stress responses. Scavenging some of these toxic stress by-products through the reduced form of glutathione is catalysed by members of the glutathione transferase (GST) enzyme superfamily. The involvement of these enzymes was studied in the model organism Brachypodium distachyon (L.)P.Beauv. Bd21 and in its derivative Bd21-3, a more drought tolerant line. Osmotic stress treatment resulted in a decrease in the water potential of both Brachypodium genotypes, the difference between the control and treated plant's ψw decreased by the last sampling day in Bd21-3, suggesting some degree of adaptation to the applied osmotic stress. Increased GST activity revealed a severe defence reaction against the harmful imbalance of the redox environment. Screening for the gene sequences led to the identification of 91 full-length or partial GST sequences. Although purple false brome has a relatively small genome, the number of identified GST genes was almost as high as the number predicted in wheat. The estimation of GST expression showed stress-induced differences: higher expression levels or the fast induction of BdGSTF8, BdGSTU35 and BdGSTU42 gene products presumably indicate a strong detoxification under osmotic stress.