Salt Stress Resistance Research Articles

Positive impact of vermicompost leachate on salt stress resistance in tomato (Solanum lycopersicum L.) at the seedling stage: a phytohormonal approach

Vermicompost leachate (VCL) produced by earthworms is a valuable biostimulant but its hormonal impact on salt-treated plants remains elusive. Plants of Solanum lycopersicum L. were cultivated in nutrient solution and exposed during 7 days to 125 mM NaCl in the presence or absence of VCL (18 mL.L−1). Mineral nutrition, water and hormonal status were quantified in roots, young and old leaves and analyzed in relation to phytohormone content of VCL. VCL improved plant growth and reduced Na+ accumulation in salt-stressed plants. It delayed senescence in young leaves through a decrease in ethylene synthesis and an increase in proline and anthocyanin contents. VCL contains high amounts of salicylic acid, benzoic acid and aminocyclopropane carboxylic acid (ACC) but low concentrations of jasmonates, cytokinins and proline. VCL did not increase abscisic acid content in salt-stressed plants and did not lead to ACC accumulation while it increased jasmonate accumulation and modified the pattern of cytokinin profile with an increase in dihydrozeatin-types in old leaves and N6-(∆2-isopentenyl)adenine-types in young ones. VCL reduces the impact of salinity on leaf senescence, which is related to its impact on endogenous phytohormones rather than to a passive absorption of exogenous hormonal compounds.

Overexpression of ThSAP30BP from Tamarix hispida improves salt tolerance

Histone deacetylases (HDACs) play an important regulatory role in plant response to biotic and abiotic stresses. They improve plant stress resistance by increasing the degree of histone acetylation associated with stress-responsive genes. SAP30BP, a human transcriptional regulatory protein, can increase histone deacetylase activity by regulating the deacetylation levels of lysines 9 and 14 in histone H3. In this study, a ThSAP30BP gene was cloned and characterized from Tamarix hispida (a kind of woody halophyte). The expression patterns of ThSAP30BP under different abiotic stresses and hormone treatments were detected by qRT-PCR. The results showed that ThSAP30BP was significantly upregulated at most time points under various stress treatments, suggesting that ThSAP30BP may be related to the abiotic stress response of T. hispida. To further analyze the salt stress resistance function of the ThSAP30BP gene, the plant overexpression vector pROKII-ThSAP30BP was instantaneously constructed and transformed into T. hispida. Meanwhile, the empty vector pROKII was also transformed as a control. The activities of SOD and POD, the contents of H2O2 and MDA, the relative conductance and the staining of NBT, DAB and Evans blue were analyzed and compared under salt stress. The results showed that the overexpression of ThSAP30BP in T. hispida reduced the accumulation of ROS in plants and the cell death rate under salt stress. These results suggested that ThSAP30BP may play an important physiological role in salt tolerance of T. hispida.

Stress-Activated Protein Kinase OsSAPK9 Regulates Tolerance to Salt Stress and Resistance to Bacterial Blight in Rice

BackgroundSalt stress and bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo) are key limiting factors of rice (Oryza sativa L.) yields. Members of sucrose non-fermenting 1 (SNF1)-related protein kinase 2 (SnRK2), which is a family of plant-specific Ser/Thr kinases, are important components of signaling pathways involved in plant developmental processes and responses to stresses. There are 10 members of the SnRK2 family in rice; however, their functions are poorly understood, as are the underlying molecular mechanisms.ResultsIn this study, we found that OsSAPK9, which belongs to the SnRK2 family, positively regulated salt-stress tolerance and strain-specific resistance to bacterial blight in rice. RNA sequencing revealed that there were 404 and 1324 genes differentially expressed in OsSAPK9-RNAi in comparison with wild-type plants under salt-stress conditions and after Xoo inoculation, respectively, which participate in basic metabolic processes. In total, 65 common differentially expressed genes involved mainly in defense responses were detected both under salt-stress conditions and after Xoo inoculation. Moreover, in vivo and in vitro experiments demonstrated that OsSAPK9 forms a protein complex with the molecular chaperones OsSGT1 and OsHsp90, and transgenic plants overexpressing OsSGT1 exhibited decreased tolerances to salt stress and significantly increased resistance levels to bacterial blight. Thus, OsSAPK9 may function as a center node regulator of salt-stress responses and disease-resistance pathways through its interaction with OsSGT1 in rice.ConclusionThis study confirms that OsSAPK9 functions as a positive regulator of salt-stress responses and disease resistance through its interaction with OsSGT1 in rice.

A Glycine max sodium/hydrogen exchanger enhances salt tolerance through maintaining higher Na+ efflux rate and K+/Na+ ratio in Arabidopsis

BackgroundSoybean (Glycine max (L.)) is one the most important oil-yielding cash crops. However, the soybean production has been seriously restricted by salinization. It is therefore crucial to identify salt tolerance-related genes and reveal molecular mechanisms underlying salt tolerance in soybean crops. A better understanding of how plants resist salt stress provides insights in improving existing soybean varieties as well as cultivating novel salt tolerant varieties. In this study, the biological function of GmNHX1, a NHX-like gene, and the molecular basis underlying GmNHX1-mediated salt stress resistance have been revealed.ResultsWe found that the transcription level of GmNHX1 was up-regulated under salt stress condition in soybean, reaching its peak at 24 h after salt treatment. By employing the virus-induced gene silencing technique (VIGS), we also found that soybean plants became more susceptible to salt stress after silencing GmNHX1 than wild-type and more silenced plants wilted than wild-type under salt treatment. Furthermore, Arabidopsis thaliana expressing GmNHX1 grew taller and generated more rosette leaves under salt stress condition compared to wild-type. Exogenous expression of GmNHX1 resulted in an increase of Na+ transportation to leaves along with a reduction of Na+ absorption in roots, and the consequent maintenance of a high K+/Na+ ratio under salt stress condition. GmNHX1-GFP-transformed onion bulb endothelium cells showed fluorescent pattern in which GFP fluorescence signals enriched in vacuolar membranes. Using the non-invasive micro-test technique (NMT), we found that the Na+ efflux rate of both wild-type and transformed plants after salt treatment were significantly higher than that of before salt treatment. Additionally, the Na+ efflux rate of transformed plants after salt treatment were significantly higher than that of wild-type. Meanwhile, the transcription levels of three osmotic stress-related genes, SKOR, SOS1 and AKT1 were all up-regulated in GmNHX1-expressing plants under salt stress condition.ConclusionVacuolar membrane-localized GmNHX1 enhances plant salt tolerance through maintaining a high K+/Na+ ratio along with inducing the expression of SKOR, SOS1 and AKT1. Our findings provide molecular insights on the roles of GmNHX1 and similar sodium/hydrogen exchangers in regulating salt tolerance.

Enzymatic activity and functional analysis under multiple abiotic stress conditions of a dehydroascorbate reductase gene derived from Liriodendron Chinense

Dehydrogenase ascorbic reductase (DHAR) is a critical enzyme involved in resistance to environmental stress. However, few DHAR genes have been identified in woody plants. Liriodendron chinense is a relict tree species of Magnoliaceae. Due to its outstanding ornamental features and fine wood properties, L. chinense is becoming increasingly applied in both timber production and landscaping. A broad ability to adapt is the initial premise of extensive planting of trees; as a result, discovery and functional validation of resistance genes are extremely important. In this study, a putative DHAR gene was isolated from L. chinense. The full-length coding sequence of the LcDHAR gene was cloned and expressed in Escherichia coli. The enzyme was then isolated and purified to investigate its activity and obtain its Michaelis constant. The results showed that the LcDHAR gene encodes a 216-aa protein that contains a complete DHAR domain. Subcellular localization assay revealed LcDHAR a cytoplasmic protein. We further calculated KmGSH and KmDHA values of 1.04 mM and 0.81 mM, respectively, for LcDHAR. Moreover, overexpression of the LcDHAR gene in Arabidopsis thaliana led to a higher content of AsA as well as enhanced salt and drought stress resistance. In addition, the transgenic plants produced leaves at an earlier time and the root length was significantly longer than that of col-0 wild-type line under gradient salt and drought stresses. Taken together, the results of this study reveal that LcDHAR might play a protective role in response to salt and drought stresses and provide a partial framework for LcDHAR gene regulation of DHA and AsA contents in Liriodendron.

Characterization of Phytase Transgenic Wheat under Salt Stress

Wheat is the major cereal crop. It is grown to meet the demand of food in developing countries but salinity is the serious problem in some countries which are based on agriculture. In the present study fourteen transgenic lines expressing phytase gene were selected using PCR and BASTA leaf paint assay. Different morphological and biochemical analysis that include plant growth, number of spikes, length of spikes, chlorophyll, soluble protein, soluble sugar and proline content were carried out from the leaf of the plants under different stress level of salt. Results showed mostly significant reduction in all the morphological parameters and chlorophyll content with increase in salt concentration while on the other hand in all other parameters, most of them showed significant increment. The result showed that some lines have ability to resist salt stress.

Molecular cloning and functional characterization of a glyceraldehyde-3-phosphate dehydrogenase gene from Spartina alterniflora reveals its involvement in salt stress response

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) has been emerging to be a multifunctional protein involved in various cellular processes, in addition to its role in energy metabolism. In this study, the SaGAPDH gene was cloned from Spartina alterniflora based on the full-length cDNA library. The open reading frame of SaGAPDH was 1014 bp, and it was encoding 337 amino acids with a calculated molecular mass of 36.40 kDa. Multiple sequence alignment showed that SaGAPDH had high amino acid sequence identity with other plant GAPDHs, and phylogenetic analysis demonstrated that SaGAPDH had a closer affinity to GAPDH in Aeluropus lagopoides (AlGAPDH). Subcellular localization suggested that SaGAPDH was located in cytosol. The recombinant SaGAPDH protein was expressed in Escherichia coli cells to characterize its catalytic activity. And E. coli carrying SaGAPDH gene showed an increased salt stress resistance. SaGAPDH gene was induced by salt stress, and to further investigate its function, transgenic Arabidopsis plants ectopically antisense-overexpressing SaGAPDH was generated. The transgenic Arabidopsis plants showed a specific down-regulation of AtGAPC1 transcript and the GAPDH enzyme activity. They also showed decreased tolerance to salt stress and down-regulation of antioxidant enzymes including catalase, ascorbate peroxidase, superoxide dismutase, and peroxidase, as well as their transcripts. Above results were further confirmed by the aggravation of oxidative damage in SaGAPDH antisense-overexpressing transgenic Arabidopsis lines, which accumulated more reactive oxygen species (ROS) such as superoxide anion (O 2 ·− ) and hydrogen peroxide (H2O2) under salt stress. This study indicated that SaGAPDH may play an important role in response to salt stress by the regulation of redox homeostasis.

Comparative physiological and transcriptomic analyses reveal salt tolerance mechanisms of Zygosaccharomyces rouxii

Abstract Zygosaccharomyces rouxii is widely applied in the production of fermented foods, where salt stress is a common environmental condition encountered. In this study, salt stress response of Z. rouxii was investigated based on physiological and transcriptomic analyses, and the results showed that Z. rouxii evoked a global regulation to resist salt stress. Analysis of physiological data showed that salt stress led to accumulation of glycerol and trehalose, and increase of unsaturated fatty acids-proportions. Intracellular amino acid analysis showed that the content of 4 amino acids (threonine, tyrosine, lysine and proline) increased significantly and 2 amino acids (serine and lysine) decreased. In addition, scanning electron microscopy analyses showed that the cell surface of Z. rouxii became rough and cell wall ruptured accompanied by intracellular spillover after salt stress. Comparison of transcriptome data showed that the genes involved in cellular metabolism and ribosome biosynthesis exhibited differently expression, which is consistent with the results of physiological data. Results presented in this study may be helpful in understanding the salt tolerance mechanism of Z. rouxii, and provide theoretical support of its application during food fermentation.

Overexpression of a MYB Family Gene, OsMYB6, Increases Drought and Salinity Stress Tolerance in Transgenic Rice.

MYB transcription factors have been demonstrated to play key regulatory roles in plant growth, development and abiotic stress response. However, knowledge concerning the involvement of rice MYB genes in salinity and drought stress resistance are largely unknown. In the present study, we cloned and characterized the OsMYB6 gene, which was induced by drought and salinity stress. Subcellular localization of OsMYB6-YFP fusion protein in protoplast cells indicated that OsMYB6 was localized in the nucleus. Overexpression of OsMYB6 in rice did not suggest a negative effect on the growth and development of transgenic plants, but OsMYB6-overexpressing plants showed increased tolerance to drought and salt stress compared with wild-type plants, as are evaluated by higher proline content, higher CAT and SOD activities, lower REL and MDA content in transgenic plants under drought and salt stress conditions. In addition, the expression of abiotic stress-responsive genes were significantly higher in OsMYB6 transgenic plants than that in wild-type plants under drought and salt stress conditions. These results indicate that OsMYB6 gene functions as a stress-responsive transcription factor which plays a positive regulatory role in response to drought and salt stress resistance, and may be used as a candidate gene for molecular breeding of salt-tolerant and drought-tolerant crop varieties.

Overexpression of the Stress-Inducible SsMAX2 Promotes Drought and Salt Resistance via the Regulation of Redox Homeostasis in Arabidopsis.

Recent studies have demonstrated that strigolactones (SLs) also participate in the regulation of stress adaptation; however, the regulatory mechanism remains elusive. In this study, the homolog of More Axillary Branches 2, which encodes a key component in SL signaling, in the perennial oil plant Sapium sebiferum was identified and functionally characterized in Arabidopsis. The results showed that the expression of SsMAX2 in S. sebiferum seedlings was stress-responsive, and SsMAX2 overexpression (OE) in Arabidopsis significantly promoted resistance to drought, osmotic, and salt stresses. Moreover, SsMAX2 OE lines exhibited decreased chlorophyll degradation, increased soluble sugar and proline accumulation, and lower water loss ratio in response to the stresses. Importantly, anthocyanin biosynthesis and the activities of several antioxidant enzymes, such as superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX), were enhanced in the SsMAX2 OE lines, which further led to a significant reduction in hydrogen peroxide levels. Additionally, the SsMAX2 OE lines exhibited higher expression level of several abscisic acid (ABA) biosynthesis genes, suggesting potential interactions between SL and ABA in the regulation of stress adaptation. Overall, we provide physiological and biochemical evidence demonstrating the pivotal role of SsMAX2 in the regulation of osmotic, drought, and salt stress resistance and show that MAX2 can be a genetic target to improve stress tolerance.

Maize Sep15-like functions in endoplasmic reticulum and reactive oxygen species homeostasis to promote salt and osmotic stress resistance.

In animals, the Sep15 protein participates in disease resistance, growth, and development, but the function of its plant homologues remains unclear. Here, the function of maize Sep15 was analysed by characterization of two independent Sep15-like loss-of-function mutants. In the absence of ZmSep15-like, seedling tolerance to both water and salinity stress was compromised. The mutants experienced a heightened level of endoplasmic reticulum stress, and over-accumulated reactive oxygen species, resulting in leaf necrosis. Characterization of Arabidopsis thaliana atsep15 mutant as well as like with ectopic expression of ZmSep15-like indicated that ZmSep15-like contributed to tolerance of both osmotic and salinity stress. ZmSep15-like interacted physically with UDP-glucose: glycoprotein glucosyltransferase1 (UGGT1). When the interaction was disrupted, the response to both osmotic and salinity stresses was impaired in maize or Arabidopsis. Co-expressing ZmUGGT1 and ZmUGGT2 enhanced the tolerance of A.thaliana to both stressors, indicating a functional interaction between them. Together, the data indicated that plants Sep15-like proteins promote osmotic and salinity stress resistance by influencing endoplasmic reticulum stress response and reactive oxygen species level.

GW5-Like, a homolog of GW5, negatively regulates grain width, weight and salt resistance in rice.

Grain size is an important determinant of yield potential in crops. We previously demonstrated that natural mutations in the regulatory sequences of qSW5/GW5 confer grain width diversity in rice. However, the biological function of a GW5 homolog, named GW5-Like (GW5L), remains unknown. In this study, we report on GW5L knockout mutants in Kitaake, a japonica cultivar (cv.) considered to have a weak gw5 variant allele that confers shorter and wider grains. GW5L is evenly expressed in various tissues, and its protein product is localized to the plasma membrane. Biochemical assays verified that GW5L functions in a similar fashion to GW5. It positively regulates brassinosteroid (BR) signaling through repression of the phosphorylation activity of GSK2. Genetic data show that GW5L overexpression in either Kitaake or a GW5 knockout line, Kasaorf3 (indica cv. Kasalath background), causes more slender, longer grains relative to the wild-type. We also show that GW5L could confer salt stress resistance through an association with calmodulin protein OsCaM1-1. These findings identify GW5L as a negative regulator of both grain size and salt stress tolerance, and provide a potential target for breeders to improve grain yield and salt stress resistance in rice.

Effect of Salt and Temperature Stress Resistance on the Tolerance of Candida parapsilosis to Extreme Conditions

Effect of Salt and Temperature Stress Resistance on the Tolerance of Candida parapsilosis to Extreme Conditions

Molecular cloning and functional characterization of the Aluminum-activated malate transporter gene MdALMT14

The salinity of soil severely restricts the rate of land use and crop productivity. Plants have developed complex mechanisms, including osmotic adjustment, to resist salt stress. Here, we report that the MdALMT14 gene in the apple is a homolog of the Arabidopsis malate acid transporter gene AtALMT14. The expression of MdALMT14 was induced by salt treatment. The ectopic expression of MdALMT14 in Arabidopsis decreased the malondialdehyde (MDA) content and the relative electronic conductivity under salt conditions. In addition, our results showed that MdALMT14 impacted salt tolerance by promoting the accumulation of malic acid in Arabidopsis. The overexpression of MdALMT14 increased salt tolerance in apple calli. Taken together, these findings provide evidence that the apple Aluminum-activated Malate Transporter MdALMT14 is involved in salt stress tolerance and the regulation of malic acid content. These data provide new ideas for further attempts to improve stress tolerance and fruit quality through cultivation and breeding methods.

Negative control of Strictisidine synthase like-7 gene on salt stress resistance in Arabidopsis thaliana

Negative control of Strictisidine synthase like-7 gene on salt stress resistance in Arabidopsis thaliana

INDETERMINATE SPIKELET1 Recruits Histone Deacetylase and a Transcriptional Repression Complex to Regulate Rice Salt Tolerance.

Perception and transduction of salt stress signals are critical for plant survival, growth, and propagation. Thus, identification of components of the salt stress-signaling pathway is important for rice (Oryza sativa) molecular breeding of salt stress resistance. Here, we report the identification of an apetala2/ethylene response factor transcription factor INDETERMINATE SPIKELET1 (IDS1) and its roles in the regulation of rice salt tolerance. By genetic screening and phenotype analysis, we demonstrated that IDS1 conferred transcriptional repression activity and acted as a negative regulator of salt tolerance in rice. To identify potential downstream target genes regulated by IDS1, we conducted chromatin immunoprecipitation (ChIP) sequencing and ChIP-quantitative PCR assays and found that IDS1 may directly associate with the GCC-box-containing motifs in the promoter regions of abiotic stress-responsive genes, including LEA1 (LATE EMBRYOGENESIS ABUNDANT PROTEIN1) and SOS1 (SALT OVERLY SENSITIVE1), which are key genes regulating rice salt tolerance. IDS1 physically interacted with the transcriptional corepressor topless-related 1 and the histone deacetylase HDA1, contributing to the repression of LEA1 and SOS1 expression. Analyses of histone H3 acetylation status and RNA polymerase II occupation on the promoters of LEA1 and SOS1 further defined the molecular foundation of the transcriptional repression activity of IDS1. Our findings illustrate an epigenetic mechanism by which IDS1 modulates salt stress signaling as well as salt tolerance in rice.

The Role of Calcium-Dependent Protein Kinase Genes CPK16, CPK25, CPK30, and CPK32 in Stilbene Biosynthesis and the Stress Resistance of Grapevine Vitis amurensis Rupr.

It is known that calcium-dependent protein kinases (CDPK or CPK) are implicated in the regulation of plant development and stress adaptation. However, there is a lack of information on the properties and functions of certain CDPK family members. The present study investigates the functions of four CDPK genes of the grapevine Vitis amurensis Rupr. in the formation of its high stress resistance level and the production of valuable secondary metabolites. Overexpression of the CPK30 gene of V. amurensis considerably increased the resistance of V. amurensis transgenic cell lines to salt and cold stresses, while CPK16, CPK25, and CPK32 overexpression did not influence the salt and temperature stress tolerance. VaCPK16 and VaCPK32 overexpression increased stilbene production in V. amurensis cell cultures by 2.1–3.1 and 1.6–3.1 times, respectively. The data indicate that the VaCPK30 gene is involved in the formation of grapevine salt and cold stress resistance, while the VaCPK16 and VaCPK32 genes contribute to increased stilbene accumulation.

Functional characterization of CgPBS2, a MAP kinase kinase in Colletotrichum gloeosporioides, using osmotic stress sensitivity as a selection marker

Colletotrichum leaf disease of Hever brasiliensis (rubber tree) caused by C. gloeosporioides is one of the major causes of declining rubber tree yields. Little is known about the fungal molecular characters that are important for pathogenicity on rubber tree and fungicide resistance. In this study, we cloned the CgPBS2 gene, the key component of the Hog1 pathway which controls various aspects of osmoregulation and fungicide resistance in various fungal pathogens, including the causal agent of Colletotrichum leaf disease of rubber tree. We characterized the function of the CgPBS2 gene by reverse genetics. Because the Hog1 pathway plays an important role in stress responses, we obtained a CgPBS2 gene deletion mutant by PEG-mediated transformation of protoplasts after reducing the concentration of sucrose in the screening medium from 1.0 M to 0.2 M. Then, the complemented transformants and GFP-labelled CgPBS2 gene transformants were selected directly under highly hyperosmotic medium (PDA + 1.5 M sorbitol) without using other selectable gene markers. Phenotypic observations showed that the CgPBS2 protein was mainly localized in the conidial cytoplasm of the CgPBS2-GFP transformants. In addition, disruption of CgPBS2 led to sensitivity to hyperosmosis and high salt concentration as well as resistance to the fungicide fludioxonil. No obvious difference in virulence was observed between the null mutant and the wild-type strain. These results provide insights into the role of the CgPBS2 gene in osmotic stress, salt stress and fludioxonil resistance and suggest that osmotic stress sensitivity can be used as a selection marker.

The response of transgenic Brassica species to salt stress: a review.

Salt stress is considered one of the main abiotic factors to limit crop growth and productivity by affecting morpho-physiological and biochemical processes. Genetically, a number of salt tolerant Brassica varieties have been developed and introduced, but breeding of such varieties is time consuming. Therefore, current focus is on transgenic technology, which plays an important role in the development of salt tolerant varieties. Various salt tolerant genes have been characterized and incorporated into Brassica. Therefore, such genetic transformation of Brassica species is a significant step for improvement of crops, as well as conferring salt stress resistance qualities to Brassica species. Complete genome sequencing has made the task of genetically transforming Brassica species easier, by identifying desired candidate genes. The present review discusses relevant information about the principles which should be employed to develop transgenic Brassica species, and also will recommend tools for improved tolerance to salinity.

Assessment of the preventive effect of vermicompost on salinity resistance in tomato (Solanum lycopersicum cv. Ailsa Craig)

To determine the effects of vermicompost leachate (VCL) on resistance to salt stress in plants, young tomato seedlings (Solanum lycopersicum, cv. Ailsa Craig) were exposed to salinity (150 mM NaCl addition to nutrient solution) for 7 days after or during 6 mL L− 1 VCL application. Salt stress significantly decreased leaf fresh and dry weights, reduced leaf water content, significantly increased root and leaf Na+ concentrations, and decreased K+ concentrations. Salt stress decreased stomatal conductance (gs), net photosynthesis (A), instantaneous transpiration (E), maximal efficiency of PSII photochemistry in the dark-adapted state (Fv/Fm), photochemical quenching (qP), and actual PSII photochemical efficiency (ΦPSII). VCL applied during salt stress increased leaf fresh weight and gs, but did not reduce leaf osmotic potential, despite increased proline content in salt-treated plants. VCL reduced Na+ concentrations in leaves (by 21.4%), but increased them in roots (by 16.9%). VCL pre-treatment followed by salt stress was more efficient than VCL concomitant to salt stress, since VCL pre-treatment provided the greatest osmotic adjustment recorded, with maintenance of net photosynthesis and K+/Na+ ratios following salt stress. VCL pre-treatment also led to the highest proline content in leaves (50 µmol g− 1 FW) and the highest sugar content in roots (9.2 µmol g− 1 FW). Fluorescence-related parameters confirmed that VCL pre-treatment of salt-stressed plants showed higher PSII stability and efficiency compared to plants under concomitant VCL and salt stress. Therefore, VCL represents an efficient protective agent for improvement of salt-stress resistance in tomato.