Adaptational Changes in Lipids of <Emphasis Type="Italic">Bradyrhizobium</Emphasis> SEMIA 6144 Nodulating Peanut as a Response to Growth Temperature and Salinity

Phospholipids provide the membrane with its barrier function and play a role in a variety of processes in the bacterial cell, as responding to environmental changes. The aim of the present study was to characterize the physiological and metabolic response of Bradyrhizobium SEMIA 6144 to saline and temperature stress. This study provides metabolic and compositional evidence that nodulating peanut Bradyrhizobium SEMIA 6144 is able to synthesize fatty acids, to incorporate them into its phospholipids (PL), and then modify them in response to stress conditions such as temperature and salinity. The fatty acids were formed from [1-¹⁴C]acetate and mostly incorporated in PL (95%). Phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and cardiolipin (CL) were found to be the major phospholipids in the bacteria analyzed. The amount and the labeling of each individual PL was increased by NaCl, while they were decreased by temperature stress. The amount of PC, PE, and PG under the combined stresses decreased, as in the temperature effect. The results indicate that synthesized PL of Bradyrhizobium SEMIA 6144 are modified under the tested conditions. Because in all conditions tested the PC amount was always modified and PC was the major PL, we suggest that this PL may be involved in the bacteria response to environmental conditions.     

Growth of Bradyrhizobium sp. SEMIA 6144 in Response to Methylglyoxal: Role of Glutathione

We previously showed the important role of glutathione (GSH) in the protection mechanism against different stresses, such as acid pH, saline, and oxidative stress, using a GSH-deficient mutant of Bradyrhizobium sp. (peanut microsymbiont). In this work, we studied the role of GSH in the protection mechanism against methylglyoxal (MG) toxicity. MG is a naturally occurring toxic electrophilic compound, and it has been shown that GSH is involved in the detoxification of MG in Escherichia coli. One recognized component of this detoxification process is the formation of a GSH adduct, which in turn transports potassium (K⁺) out of bacterial cells. Our results showed that growth of wild-type strain Bradyrhizobium sp. SEMIA 6144 was not affected at a MG concentration of 0.5 mM in the yeast extract–mannitol culture medium. However, a reduction of growth, at concentrations of 1.5 and 2.5 mM MG and reaching complete growth inhibition at 3.0 mM MG, was observed. In wild-type strain, intracellular GSH content decreased, and intracellular K⁺ content was unchanged, whereas GSH-deficient mutant SEMIA 6144-S7Z was unable to grow at 1.5 mM MG. The addition of external GSH to the incubation medium did not restore the growth rate either in wild-type or mutant strains. Our findings showed that GSH has not proven to be protective against the cell-growth inhibiting activity of MG. Therefore, the response of Bradyrhizobium sp. growth to MG is different from that reported in E. coli and other Gram-negative bacteria.     

Phenolic acids: Possible agents of modifying N2-fixing symbiosis through rhizobial alteration?

Phenolic acids, low molecular weight phenolics, are precursors of a variety of antimicrobial compounds, root signalling molecules, and phytoalexins that play an important role in plant defence responses. In agro ecosystem, a large amount of litter is turned over during the cropping season, fallow period and land preparation. This releases a flush of phenolic acids, amounts of which exceed very much the quantities released in root exudation. In rhizobial inoculation of legumes, these phenolic acids, depending on the concentration, may affect the persistence of rhizobia in the soil and their symbiotic efficiency, in terms of N₂ fixation. The present study evaluates the effects of different concentrations of four phenolic acids (protocatechuic, p-coumaric, ferulic and vanillic) on population size of four rhizobial strains (Bradyrhizobium elkanii SEMIA 5019, B. japonicum TAL 102 and TAL 620, and Azorhizobium caulinodans ORS 571). Culture media with different concentrations of phenolic acids in the presence or absence of manitol were used to evaluate rhizobial population size on day 6. Rhizobial total proteins were extracted and electrophoresed on polyacrylamide gels. Further, the effects of phenolic acid-affected rhizobia on N₂ fixing capacity were also investigated by inoculating two of those strains to soybean. Phenolic acid-treated B. elkanii SEMIA 5019 and B. japonicum TAL 102 were inoculated to soybean, and plant growth, N accumulation and nodule dry weight were assessed in a pot experiment. The population size of TAL 102 was induced when the culture medium was supplied with different phenolic acids as the sole carbon source. In many cases, the presence of manitol in the medium masked the differential effects of phenolic acids on the rhizobial population size. All four phenolic acids used in our study suppressed the population size of TAL 620. Strain ORS 571 showed low population size at low concentrations followed by a growth recovery at high phenolic acid concentrations. Strain SEMIA 5019 treated with 0.03 mM ferulic acid produced the highest increase in shoot growth of soybean, (ca. 65%). Treating strain SEMIA 5019 with 9 mM protocatechuic acid produced the largest decrease in nodule dry weight (ca. 50%) without any significant changes in shoot N accumulation. P-coumaric acid, even at 0.12 mM, could stimulate the N₂ fixing activity of SEMIA 5019, whereas the same concentration reduced the effectiveness of TAL102 in a soybean-rhizobium symbiosis. Phenolic acid interactions with rhizobia led to biochemical, and hence physiological changes, resulting in an alteration in their symbiotic ability. Different leguminous plants secrete different phenolic compounds other than phenolic acids during root exudation. Further studies should therefore be conducted to evaluate the effects of those compounds on the symbiosis. It is concluded from this study that the effect of phenolic acids is concentration and structure dependant, and strain-specific. The effect will also be pH dependant. Thus, phenolic acids are possible agents for modifying the legume-rhizobial symbiosis.     

Glutamate Is Involved in Acid Stress Response in Bradyrhizobium sp. SEMIA 6144 (Arachis hypogaea L.) Microsymbiont

In the present study, the effect of acid stress on ammonium assimilation in Bradyrhizobium sp. SEMIA 6144 (Arachis hypogaea L.) microsymbiont was analyzed. The bacterial growth rate was decreased by 50%, and a significant increase in intracellular glutamate concentration was detected when the strain grew at acid pH (5.5). Assays of the enzymes involved in glutamate synthesis showed increased activities of glutamine synthetase (GS) and glutamate synthase (NADPH-GOGAT) under acid stress condition. This would support the contention that the GS/NADPH-GOGAT pathway contributes to the increase of glutamate synthesis as a compatible solute in response to acid stress.     

Nod factor-independent ‘crack-entry’ symbiosis in dalbergoid legume Arachis hypogaea

Dalbergoids are typified by crack-entry symbiosis which is evidenced to be Nod Factor (NF)-independent in several Aeschynomene legumes. Natural symbionts of the dalbergoid legume Arachis hypogaea are always NF-producing, prompting us to check whether symbiosis in this legume could also be NF-independent. For this, we followed the symbiosis with two NF-containing bradyrhizobial strains – SEMIA6144, a natural symbiont of Arachis and ORS285, a versatile nodulator of Aeschynomene legumes, along with their corresponding nodulation (nod) mutants. Additionally, we investigated NF-deficient bradyrhizobia like BTAi1, a natural symbiont of Aeschynomene indica and the WBOS strains that were natural endophytes of Oryza sativa, collected from an Arachis-Oryza intercropped field. While SEMIA6144ΔnodC was non-nodulating, both ORS285 and ORS285ΔnodB could induce functional nodulation, although with lower efficiency than SEMIA6144. On the other hand, all the NF-deficient strains – BTAi1, WBOS2 and WBOS4 showed comparable nodulation with ORS285 indicating Arachis to harbour an NF-independent mechanism of symbiosis. Intriguingly, symbiosis in Arachis, irrespective of whether it was NF-dependent or independent, was always associated with the curling or branching of the rosette root hairs at the lateral root bases. Thus, despite being predominantly described as an NF-dependent legume, Arachis does retain a vestigial, less-efficient form of NF-independent symbiosis.     

Cadmium Accumulation and Tolerance in <Emphasis Type="Italic">Bradyrhizobium</Emphasis> spp. (Peanut Microsymbionts)

In this study, the effect of cadmium (Cd) on cell viability and its accumulation in Bradyrhizobium spp. (peanut microsymbionts) as well as the role of glutathione (GSH) in the tolerance to this metal were investigated. A reference strain recommended as peanut inoculant (Bradyrhizobium sp. SEMIA6144) grew up to 10 μM Cd meanwhile a GSH-deficient mutant strain (Bradyrhizobium sp. SEMIA6144-S7Z) was unable to grow at this concentration. Two native peanut isolates obtained from Córdoba soils (Bradyrhizobium sp. NLH25 and Bradyrhizobium sp. NOD31) tolerated up to 30 μM Cd. The analysis of Cd content showed that Bradyrhizobium sp. SEMIA6144 accumulated a high amount of this metal, but a considerable inhibition of growth was observed compared to tolerant strains at 10 μM Cd. At this concentration, the intracellular GSH content of all the Bradyrhizobium sp. strains was not modified in comparison to control conditions. However, at 30 μM Cd, the intracellular GSH content significantly increased in Bradyrhizobium sp. strains NLH25 and NOD31. Thus, the distinct response of each Bradyrhizobium sp. strain to Cd reveals that, even in closely related lineages, there are strain-specific variations influencing the levels of tolerance to this metal. Indeed, the native peanut isolates tolerated higher Cd concentration than the reference strain, possibly due to an increase in GSH levels which could act as a detoxifying agent.     

Effects of single and co-inoculation with native phosphate solubilising strain Pantoea sp J49 and the symbiotic nitrogen fixing bacterium Bradyrhizobium sp SEMIA 6144 on peanut (Arachis hypogaea L.) growth

In the present study, attempts were made to analyze the effect of co-inoculation with an efficient phosphate solubilising native isolate Pantoea sp J49 and the symbiotic nitrogen fixing Bradyrhizobium sp SEMIA 6144 strain on Arachis hypogaea L. plants growth. Single and co-inoculation of peanut plants growing in plastic pots containing soil with low P content were developed. Plants were harvested at R1 and R4 growth stages and were analyzed in different growth parameters. Survival of strain Pantoea sp J49 was analyzed in soil samples and in root tissues. Plants inoculated only with Pantoea sp J49 showed the highest shoot and root weight in both reproductive growth stages evaluated. Plants co-inoculated with this strain and Bradyrhizobium sp SEMIA 6144 showed increase in aerial dry weight at R1 stage. Survival assays demonstrated that Pantoea sp J49 survives not only in the peanut rhizosphere but also inside plant tissues, including nodules formed when it was co-inoculated with Bradyrhizobium sp SEMIA 6144. Results obtained in this study confirm the great potential of the native Pantoea sp J49 isolate in the promotion of peanut plant growth, probably related with its capacity to solubilise phosphate.     

Symbiotic nitrogen fixation and nitrate reduction in two peanut cultivars with different growth habit and branching pattern structures

We have investigated the response of two peanut cultivars (TEGUA and UTRE) with different growth habits and branching pattern structures to different nitrogen (N) sources, namely, N-fertilizer or N₂ made available by symbiotic fixation, and analysed the pattern of nitrate reductase (NR) activity in these cultivars. Nitrate and amino acid contents were also examined under these growth conditions. In terms of nitrogen source, cv. TEGUA showed a better response to inoculation with Bradyrhizobium sp. SEMIA 6144 at 40 days after planting, while cv. UTRE responded better to N-fertilizer (5 mM KNO₃). Both cultivars showed different patterns of NR activity in the analyzed plant organs (leaves, roots, and nodules), which were dependent on the N source. When nitrogen became available to the plant through symbiotic N₂ fixation, the patterns of NR activity distribution were different in the two cultivars, with cv. TEGUA showing a higher NR activity in the nodules than in the leaves and roots, and cv. UTRE showing no difference in terms of NR activity among organs. The nitrate and amino acid contents showed a similar trend between the two cultivars, with the highest nitrate content in the leaves of fertilized plants and the highest amino acid content in the nodules. The high nitrate content of the leaves of cv. UTRE indicated the better response of this cultivar to N-fertilizer.     

Expression of a carbonic anhydrase gene is induced by environmental stresses in Rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Expression of the gene (OsCA1) coding for carbonic anhydrase (CA) in leaves and roots of rice was induced by environmental stresses from salts (NaCl, NaHCO₃ and Na₂CO₃), and osmotic stress (10%, w/v, PEG 6000). CA activity of rice seedlings more than doubled under some of these stresses. Transgenic Arabidopsis over-expressing OsCA1 had a greater salt tolerance at the seedling stage than wild-type plants in 1/2 MS medium with 5 mM NaHCO₃, 50 mM NaCl, on 100 mM NaCl. Thus CA expression responds to environmental stresses and is related to stress tolerance in rice.     

Can <Emphasis Type="Italic">Bradyrhizobium</Emphasis> strains inoculation reduce water deficit effects on peanuts?

Drought is one of the environmental factors that most affects peanut cultivation in semi-arid regions, resulting in economic losses to growers. However, growth promoting bacteria are able to reduce water deficit damage in some plant species. In this context, this study aimed to evaluate the interaction of Bradyrhizobium strains reducing water stress effects on peanut genotypes by antioxidant enzymes activities, leaf gas exchanges and vegetative growth, as well as to determine the taxonomic positioning of strain ESA 123. The 16S rRNA gene of ESA 123 was amplified by PCR and sequenced by dideoxy Sanger sequencing method. An experiment was performed in greenhouse with three peanut genotypes (BRS Havana, CNPA 76 AM and 2012-4), two Bradyrhizobium strains (SEMIA 6144 and ESA 123), a mineral source of N and an absolute control (without N) under two water regimes (with and without irrigation). Seeds of peanut were sown and the plants were grown until 30 days after emergence. On the 20th day, the water deficit plants group had their irrigation suspended for 10 days. At in silico analyzes, ESA 123 presented 98.97% similarity with the type strain of B. kavangense. Leaf gas exchange was affected by water deficit; as well as alteration of antioxidant activities and reduction of vegetative growth variables. However, some plants inoculated with SEMIA 6144 and ESA 123 strains presented lower reductions and increment of some evaluated variables, mainly the ones inoculated with the ESA 123 strain, Bradyrhizobium sp. from the semi-arid region of Northeast Brazil. This data suggests beneficial effects of the peanut-Bradyrhizobium interaction in a water stress condition, specially with the ESA 123 strain.     

Differential expression of ferritin genes in response to abiotic stresses and hormones in pear (<Emphasis Type="Italic">Pyrus pyrifolia</Emphasis>)

In this study, the expression patterns of four ferritin genes (PpFer1, PpFer2, PpFer3, and PpFer4) in pear were investigated using quantitative real-time PCR. Analysis of tissue-specific expression revealed higher expression level of these genes in leaves than in other tested tissues. These ferritin genes were differentially expressed in response to various abiotic stresses and hormones treatments. The expression of ferritin wasn’t affected by Fe(III)-citrate treatment. Abscisic acid significantly enhanced the expression of all four ferritin genes, especially PpFer2, followed by N-benzylyminopurine, gibberellic acid, and indole-3-acetic acid. The expression peaks of PpFer1 and PpFer3 in leaves appeared at 6, 6, and 12 h, respectively, after pear plant was exposed to oxidative stress (5 mM H₂O₂), salt stress (200 mM NaCl), and heat stress (40°C). A significant increase in PpFer4 expression was detected at 6 h after salt stress or heat stress. The expression of ferritin genes was not altered by cold stress. These results suggested that ferritin genes might be functionally important in acclimation of pear to salt and oxidative stresses. Hormone treatments had no significant effect on expression of ferritin genes compared to abiotic stresses. This showed accumulation of ferritin genes could be operated by different transduction pathways under abiotic stresses and hormones treatments.     

Influence of exogenously applied nitric oxide on strawberry (Fragaria × ananassa) plants grown under iron deficiency and/or saline stress

A study was carried out to assess the protective effects of exogenously applied nitric oxide (NO) in the form of its donor sodium nitroprusside (SNP) to strawberry seedlings (Fragaria × ananassa cv. Camarosa) grown under iron deficiency (ID), salinity stress or combination of both. The experimental design contained control, 0.1 mM FeSO₄ (ID, Fe deficiency); 50 mM NaCl (S, Salinity) and ID + S. Plants were sprayed with 0.1 mM SNP or 0.1 mM sodium ferrocyanide, an analogue of SNP containing no NO. The deleterious effects of ID + S treatments on plant fresh and dry matters, total chlorophyll and chlorophyll fluorescence were more striking than those caused by the ID or S treatment alone. Furthermore, combination of salinity and iron stress exacerbated electrolyte leakage (EL) and the levels of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) in plant leaves compared to those in plants grown with either of the single stresses. NO treatment effectively reduced EL, MDA and H₂O₂ in plants grown under stress conditions applied singly or in combination. Salt stress alone and with ID reduced the superoxide dismutase (EC1.15.1.1) and catalase (EC 1.11.1.6) activities but increased that of POD (EC 1.17.1.7). Exogenously applied NO led to significant changes in antioxidant enzyme activities in either ID or S than those by ID+S. Overall, exogenously applied NO was more effective in mitigating the stress‐induced adverse effects on the strawberry plants exposed to a single stress than those due to the combination of both stresses.     

Comparison of the effects of salt-stress and alkali-stress on photosynthesis and energy storage of an alkali-resistant halophyte <Emphasis Type="Italic">Chloris virgata</Emphasis>

Seedlings of Chloris virgata were treated with varying (0–160 mM) salt-stress (SS; 1: 1 molar ratio of NaCl to Na₂SO₄) or alkali-stress (AS; 1: 1 molar ratio of NaHCO₃ to Na₂CO₃). To compare these effects, relative growth rates (RGR), stored energy, photosynthetic pigment contents, net photosynthetic rates, stomatal conductance, and transpiration rates were determined. Both stresses did not change significantly the photosynthetic parameters of C. virgata under moderate stress (below 120 mM). Photosynthetic ability decreased significantly only at high stress (160 mM). Thus C. virgata, a natural alkali-resistant halophyte, adapts better to both kinds of stress. The inhibition effects of AS on RGR and energy storage of C. virgata were significantly greater than that of SS of the same intensity. The energy consumption of C. virgata was considerably greater while resisting AS than while resisting SS.     

Involvement of glutathione and enzymatic defense system against cadmium toxicity in Bradyrhizobium sp. strains (peanut symbionts)

In this study, the effects of cadmium (Cd) on cell morphology and antioxidant enzyme activities as well as the distribution of the metal in different cell compartments in Bradyrhizobium sp. strains were investigated. These strains were previously classified as sensitive (Bradyrhizobium sp. SEMIA 6144) and tolerant (Bradyrhizobium sp. NLH25) to Cd. Transmission electron micrographs showed large electron-translucent inclusions in the sensitive strain and electron-dense bodies in the tolerant strain, when exposed to Cd. Analysis of Cd distribution revealed that it was mainly bounded to cell wall in both strains. Antioxidant enzyme activities were significantly different in each strain. Only the tolerant strain was able to maintain a glutathione/oxidized glutathione (GSH/GSSG) ratio by an increase of GSH reductase (GR) and GSH peroxidase (GPX) enzyme activities. GSH S-transferase (GST) and catalase (CAT) activities were drastically inhibited in both strains while superoxide dismutase (SOD) showed a significant decrease only in the sensitive strain. In conclusion, our findings suggest that GSH content and its related enzymes are involved in the Bradyrhizobium sp. tolerance to Cd contributing to the cellular redox balance.     

Salt stress induced biometric and physiological changes in Solanum tuberosum L. cv. Bintje grown in vitro

Potato plants grown in vitro were subjected to different salt stresses by providing the salts NaCl, Na₂SO₄, MgCl₂ and MgSO₄ in different concentrations up to 300 mM. Salinity greatly affected the survival and the rooting of the plants. Shoot and root growth decreased with increasing salt concentrations. Under mild stress conditions, i.e. in conditions where the plant is able to adapt to the stress, the observed decrease was dependent upon the salt used. Under severe stress conditions, however, the decrease of the shoot and root growth was independent of the nature of the ions.     

Physiological changes induced in four bacterial strains following oxidative stress

In order to study the behavior and resistance of bacteria under extreme conditions, physiological changes associated with oxidative stress were monitored using flow cytometry. The study was conducted to assess the maintenance of membrane integrity and potential as well as the esterase activity, the intracellular pH and the production of superoxide anions in four bacterial strains (Ralstonia metallidurans, Escherichia coli, Shewanella oneidensis and Deinococcus radiodurans). The strains were chosen for their potential use in bioremediation. Suspensions of R. metallidurans, E. coli, S. oneidensis and D. radiodurans were submitted to 1 h of oxidative stress (H₂O₂ at various concentrations from 0 to 880 mM). Cell membrane permeability (propidium iodide) and potential (rhodamine-123,3,3’-dihexyloxacarbocyanine iodide), intracellular esterase activity (fluorescein diacetate), intracellular-reactive oxygen species concentration (hydroethidine) and intracellular pH (carboxy-fluorescein diacetate succinimidyl ester 5-(6)) were monitored to evaluate the physiological state and the overall fitness of individual bacterial cells under oxidative stress. The four bacterial strains exhibited varying sensitivities towards H₂O₂. However, for all the bacterial strains, some physiological damage could already be observed from 13.25 mM H₂O₂ onwards, in particular with regard to their membrane permeability. Depending on the bacterial strains, moderate to high physiological damage could be observed between 13.25 mM and 220 mM H₂O₂. The membrane potential, esterase activity, intracellular pH and production of superoxide anion production were in all four strains considerably modified at high H₂O₂ concentrations. In conclusion, we show that a range of significant physiological alterations occur when bacteria are challenged with H₂O₂ and fluorescent staining methods coupled with flow cytometry are used for monitoring the changes induced not only by oxidative stress, but also by other stresses like temperature, radiation, pressure, pH, etc. The text was submitted by the authors in English.     

Over-expression of the apple <Emphasis Type="Italic">spermidine synthase</Emphasis> gene in pear confers multiple abiotic stress tolerance by altering polyamine titers

An apple spermidine synthase (SPDS) gene (MdSPDS1) was verified to encode a functional protein by the complementation of the spe3 yeast mutant, which lacks the SPDS gene. To justify our hypothesis that apple SPDS is involved in abiotic stress responses and to obtain transgenic fruit trees tolerant to abiotic stresses as well, MdSPDS1-over-expressing transgenic European pear (Pyrus communis L. ‘Ballad’) plants were created by Agrobacterium-mediated transformation. A total of 21 transgenic lines showing various spermidine (Spd) titers and MdSPDS1 expression levels were obtained. Selected lines were exposed to salt (150 mM NaCl), osmosis (300 mM mannitol), and heavy metal (500 μM CuSO₄) stresses for evaluating their stress tolerances. Transgenic line no. 32, which was revealed to have the highest Spd accumulation and expression level of MdSPDS1, showed the strongest tolerance to these stresses. When growth increments, electrolyte leakage (EL), and values of thiobarbituric acid reactive substances (TBARS) were monitored, line no. 32 showed the lowest growth inhibition and the least increase in EL or TBARS under stress conditions. Spd titers in wild-type and transgenic lines showed diverse changes upon stresses, and these changes were not consistent with the changes in MdSPDS1 expressions. Moreover, there were no differences in the sodium concentration in the shoots between the wild type and line no. 32, whereas the copper concentration was higher in the wild type than in line no. 32. Although the mechanism(s) underlying the involvement of polyamines in stress responses is not known, these results suggest that the over-expression of the SPDS gene substantially increased the tolerance to multiple stresses by altering the polyamine titers in pear. Thus, MdSPDS1-over-expressing transgenic pear plants could be used to improve desert land and/or to repair polluted environments. Xiao-Peng Wen and Xiao-Ming Pang contributed equally to this work.     

Interaction between hydrogen peroxide and sodium nitroprusside following chemical priming of Ocimum basilicum L. against salt stress

Sodium nitroprusside (SNP) and hydrogen peroxide (H₂O₂)_, as priming agents, have the well-recorded property to increase plant tolerance against a range of different abiotic stresses such as salinity. In this regard, the present study was conducted to evaluate the effect of different levels of SNP (100 and 200 µM) and H₂O₂ (2.5 and 5 mM) as well as their combinations under salt stress (0 and 50 mM NaCl) on key physiological and biochemical attributes of the economically important aromatic plant basil (Ocimum basilicum L.) grown under hydroponic culture. Results revealed that morphological parameters such as plant height, root length, leaf fresh and dry weights (FW and DW) were significantly decreased by salinity stress, while SNP and H₂O₂ treatments, alone or combined, increased FW and DW thus enhancing plant tolerance to salt stress. Furthermore, 200 µM SNP + 2.5 mM H₂O₂ appeared to be the most effective treatment by causing significant increase in chlorophyll a and b, anthocyanin content and guaiacol peroxidase and ascorbate peroxidase enzymes activities under saline condition. In addition, analytical measurements showed that essential oil profile (concentration of main components) under salt stress was mostly affected by SNP and H₂O₂ treatments. The highest increase was observed for methyl chavicol (43.09–69.91%), linalool (4.8–17.9%), cadinol (1.5–3.2%) and epi-α-cadinol (0.18–10.75%) compounds. In conclusion, current findings demonstrated a positive crosstalk between SNP and H₂O₂ toward improved basil plant tolerance to salt stress, linked with regulation of essential oil composition.