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A comparative investigation was conducted to evaluate transcriptional changes in guard cells (GCs) of closely related halophytic (Chenopodium quinoa) and glycophytic (Spinacia oleracea) species. Plants were exposed to 3 weeks of 250 mM sodium chloride treatment, and GC-enriched epidermal fragments were mechanically prepared. In both species, salt-responsive genes were mainly related to categories of protein metabolism, secondary metabolites, signal transduction and transport systems. Genes related to abscisic acid (ABA) signaling and ABA biosynthesis were strongly induced in quinoa but not in spinach GCs. Also, expression of the genes encoding transporters of amino acids, proline, sugars, sucrose and potassium increased in quinoa GCs under salinity stress. Analysis of cell-wall-related genes suggests that genes involved in lignin synthesis (e.g. lignin biosynthesis LACCASE 4) were highly upregulated by salt in spinach GCs. In contrast, transcripts related to cell wall plasticity Pectin methylesterase3 (PME3) were highly induced in quinoa. Faster stomatal response to light and dark measured by observing kinetics of changes in stomatal conductance in quinoa might be associated with higher plasticity of the cell wall regulated by PME3 Furthermore, genes involved in the inhibition of stomatal development and differentiation were highly expressed by salt in quinoa, but not in spinach. These changes correlated with reduced stomatal density and index in quinoa, thus improving its water use efficiency. The fine modulation of transporters, cell wall modification and controlling stomatal development in GCs of quinoa may have resulted in high K+/Na+ ratio, lower stomatal conductance and higher stomatal speed for better adaptation to salinity stress in quinoa.

Soil salinity is among the major abiotic stresses that plants must cope with, mainly in arid and semiarid regions. The tolerance to high salinity is an important agronomic trait to sustain food production. Quinoa is a halophytic annual pseudo-cereal species with high nutritional value that can secrete salt out of young leaves in external non-glandular cells called epidermal bladder cells (EBC). Previous work showed high salt tolerance, but low EBC density was associated with an improved response in the early phases of salinity stress, mediated by tissue-tolerance traits mainly in roots. We compared the transcript profiling of two quinoa genotypes with contrasting salt tolerance patterning to identify the candidate genes involved in the differentially early response among genotypes. The transcriptome profiling, supported by in vitro physiological analyses, provided insights into the early-stage molecular mechanisms, both at the shoot and root level, based on the sensitive/tolerance traits. Results showed the presence of numerous differentially expressed genes among genotypes, tissues, and treatments, with genes involved in hormonal and stress response upregulated mainly in the sensitive genotype, suggesting that tolerance may be correlated to restricted changes in gene expression, at least after a short salt stress. These data, showing constitutive differences between the two genotypes, represent a solid basis for further studies to characterize the salt tolerance traits. Additionally, new information provided by this work might be useful for the development of plant breeding or genome engineering programs in quinoa.

Populus is a genus of globally significant plantation trees used widely in industrial and agricultural production. Poplars are easily damaged by Micromelalopha troglodyta and Hyphantria cunea , resulting in decreasing quality. Because of their strong insect resistance, Bt toxin-encoded Cry genes have been widely adopted in poplar breeding. Therefore, the potential adverse effects of Cry1Ah1- modified (CM) poplars on the ecological environment have been concerned. The Illumina novaseq platform was used to perform high-throughput sequencing . Alpha diversity analyses were performed using the Chao1 index to determine community richness, and the Shannon index analyses were used to determine community richness and evenness. Our analysis of rhizosphere soil chemistry patterns revealed that rhizosphere soil available phosphorus, rhizosphere microbial biomass nitrogen, and rhizosphere phosphorus levels were declined. In contrast, rhizosphere microbial biomass carbon level increased in CM poplar rhizosphere samples. We applied metagenomic sequencing of non-transgenic (NT) and CM poplar rhizosphere samples collected from a natural field; the predominant taxa included Proteobacteria, Acidobacteria, and Actinobacteria. Together, these results showed that the Cry1Ah1 expression has no significant influences on the community composition of rhizosphere microbiomes . Also, the Cry1Ah1 expression in poplars has no notable effects on the relative abundances of most rhizosphere bacteria . In addition, there are no significant adverse effects of CM varieties on most rhizosphere fungal abundances. However, only a few rhizosphere fungal abundances differ in NT and CM varieties.

Epidermal fragments enriched in guard cells (GCs) were isolated from the halophyte quinoa (Chenopodium quinoa Wild.) species, and the response at the proteome level was studied after salinity treatment of 300 mM NaCl for 3 weeks. In total, 2147 proteins were identified, of which 36% were differentially expressed in response to salinity stress in GCs. Up and downregulated proteins included signaling molecules, enzyme modulators, transcription factors and oxidoreductases. The most abundant proteins induced by salt treatment were desiccation-responsive protein 29B (50-fold), osmotin-like protein OSML13 (13-fold), polycystin-1, lipoxygenase, alpha-toxin, and triacylglycerol lipase (PLAT) domain-containing protein 3-like (eight-fold), and dehydrin early responsive to dehydration (ERD14) (eight-fold). Ten proteins related to the gene ontology term &ldquo, response to ABA&rdquo, were upregulated in quinoa GC, this included aspartic protease, phospholipase D and plastid-lipid-associated protein. Additionally, seven proteins in the sucrose&ndash, starch pathway were upregulated in the GC in response to salinity stress, and accumulation of tryptophan synthase and L-methionine synthase (enzymes involved in the amino acid biosynthesis) was observed. Exogenous application of sucrose and tryptophan, L-methionine resulted in reduction in stomatal aperture and conductance, which could be advantageous for plants under salt stress. Eight aspartic proteinase proteins were highly upregulated in GCs of quinoa, and exogenous application of pepstatin A (an inhibitor of aspartic proteinase) was accompanied by higher oxidative stress and extremely low stomatal aperture and conductance, suggesting a possible role of aspartic proteinase in mitigating oxidative stress induced by saline conditions.

Green gram [Vigna radiata (L.)] is an important pulse crop in tropical and sub-tropical regions around the globe. We evaluated green gram germplasm comprising a large collection of 533 accessions for qualitative and quantitative traits. On the basis of average linkage, germplasm was grouped in five main clusters, where cluster I and cluster V grouped the accessions with contrasting traits, similar to clusters II and IV which also differ strikingly.Majority of the positive qualitative traits, particularly of breeder’s interest, were concentrated in clusters I-III, including tolerance against yellow mosaic virus and leaf curl virus. In principal component analysis (PCA), quantitative traits contributed positively to first two PCs. The results of PCA, phenotypic and genotypic coefficients of variations and genetic advance suggested that selection for higher pods/plant, branches/plant, seeds/pod and 100 seed weight can significantly improve yield potential and hence, can be used as effective selection indicators. Overall negative association between days to maturity (DM), days to flowering (DF) and major yield traits suggested that selection for short duration plant will compromise yield potential. Appropriate harvest index (HI) range was determined on the basis of selection score (SC). The highest HI range was from 25.1–30.0% (12.07 SC) followed by 30.1–35.0% (10.34 SC), provided strong basis for future mungbean selection. Mungbean germplasm used in the current study displayed significant diversity for DF, DM and major yield traits and hence, can help to break negative linkage drag between DM and major yield contribution traits to develop high yielding short duration green gram varieties for hybridization-based breeding programs.

Stomata, which are microscopic valves on the leaf surface formed by two guard cells (GC), play a critical role in the regulation of leaf water and gas exchange and, hence, determine plant adaptive potential. However, little data is available on GC biochemistry, protein abundance and gene expression, mainly due to technical difficulties and challenges in isolating sufficient amounts of high-quality pure GC. In the present study we applied some modifications to the mechanical isolation of guard-cell to generalise this method for diverse growth conditions as well as plant species. Epidermal peel fragments enriched in guard cells were mechanically isolated from quinoa, spinach and sugar beet leaves grown at two conditions (normal and salt stress). Multiple analysis was performed to confirm the suitability and superiority of the modified technique to the original method. At the first step, the viability and purity of GC-enriched epidermal fragments were assessed under the microscope. Then, the RNA integrity, gene expression, and 1D SDS-PAGE tests were performed to validate the suitability of this technique for omics studies. The data revealed a wide range of proteins as well as a high integrity of RNA extracted from guard cell samples. The expression level of several GC-specific genes and mesophyll-dominant genes were investigated using a comparative analysis of transcriptome datasets of GC and whole-leaf samples. We found that Rubisco and photosynthesis-related proteins such as chlorophyll a/b binding protein were substantially higher in the whole leaf compared with the GCs. More importantly, GC-specific genes such as OST1, SLAC1, MYB60, FAMA and HT1 were highly expressed in the GCs, confirming that our guard cell preparation was highly enriched in GC gene transcripts. Real-time quantitative reverse transcription PCR further confirmed the efficacy of the GC isolation technique for exploring responses of GC to diverse types of stress at the molecular level.

Soil salinity is a major environmental constraint affecting crop growth and threatening global food security. Plants adapt to salinity by optimizing the performance of stomata. Stomata are formed by two guard cells (GCs) that are morphologically and functionally distinct from the other leaf cells. These microscopic sphincters inserted into the wax-covered epidermis of the shoot balance CO2 intake for photosynthetic carbon gain and concomitant water loss. In order to better understand the molecular mechanisms underlying stomatal function under saline conditions, we used proteomics approach to study isolated GCs from the salt-tolerant sugar beet species. Of the 2088 proteins identified in sugar beet GCs, 82 were differentially regulated by salt treatment. According to bioinformatics analysis (GO enrichment analysis and protein classification), these proteins were involved in lipid metabolism, cell wall modification, ATP biosynthesis, and signaling. Among the significant differentially abundant proteins, several proteins classified as “stress proteins” were upregulated, including non-specific lipid transfer protein, chaperone proteins, heat shock proteins, inorganic pyrophosphatase 2, responsible for energized vacuole membrane for ion transportation. Moreover, several antioxidant enzymes (peroxide, superoxidase dismutase) were highly upregulated. Furthermore, cell wall proteins detected in GCs provided some evidence that GC walls were more flexible in response to salt stress. Proteins such as L-ascorbate oxidase that were constitutively high under both control and high salinity conditions may contribute to the ability of sugar beet GCs to adapt to salinity by mitigating salinity-induced oxidative stress.

Soil salinity is a major environmental constraint affecting crop growth and threatening global food security. Plants adapt to salinity by optimizing the performance of stomata. Stomata are formed by two guard cells (GCs) that are morphologically and functionally distinct from the other leaf cells. These microscopic sphincters inserted into the wax-covered epidermis of the shoot balance CO2 intake for photosynthetic carbon gain and concomitant water loss. In order to better understand the molecular mechanisms underlying stomatal function under saline conditions, we used proteomics approach to study isolated GCs from the salt-tolerant sugar beet species. Of the 2088 proteins identified in sugar beet GCs, 82 were differentially regulated by salt treatment. According to bioinformatics analysis (GO enrichment analysis and protein classification), these proteins were involved in lipid metabolism, cell wall modification, ATP biosynthesis, and signaling. Among the significant differentially abundant proteins, several proteins classified as &ldquo, stress proteins&rdquo, were upregulated, including non-specific lipid transfer protein, chaperone proteins, heat shock proteins, inorganic pyrophosphatase 2, responsible for energized vacuole membrane for ion transportation. Moreover, several antioxidant enzymes (peroxide, superoxidase dismutase) were highly upregulated. Furthermore, cell wall proteins detected in GCs provided some evidence that GC walls were more flexible in response to salt stress. Proteins such as L-ascorbate oxidase that were constitutively high under both control and high salinity conditions may contribute to the ability of sugar beet GCs to adapt to salinity by mitigating salinity-induced oxidative stress.

Agricultural production needs to be doubled by year 2050; this task is complicated by various abiotic stresses severely affecting crop production. Salinity stress is among major environmental stresses that influences crop production globally and it is estimated that around 950 million hectares of arable land is affected by this environmental stress. Considering this fact, it is necessary to introduce new approaches to manage this main challenge. One of them is breeding for enhanced salinity tolerance. An alternative solution may be the use of halophyte relatives. Despite having high tolerance to salt stress, halophytic plants have not been extensively used to study salinity tolerance mechanisms. Also, studies investigating the salinity tolerance mechanism in halophytes have concentrated on physiological or anatomical aspects with relatively little focus being given to the omics-based studies such as metabolomics and transcriptome analysis. Epidermal bladder cells (EBCs) are specialized structures in some of halophytic plants that provide external store for toxic ions such as Na\(^+\) and Cl\(_-\), and hence understanding the function of EBCs may eventually play an important role in transferring this ability to crop plants. Stomata also being another focus of this study. Although there have been significant advances of understanding mechanisms that controlling stomatal development and also the signalling pathways that regulate guard cells function in glycophytes, much less is known about stomata development and operation in halophytes. In light with this fact a question on how environmental variables and in particular salinity stress change the basal stomatal development pathway requires more studies. Given the fact that osmotic stress and toxic Na\(^+\) level negatively affect stomatal parameters under saline conditions the question is that why are halophytes capable to optimise their stomata performance? Do halophytic plants possess unique stomata operation mechanisms? How does salinity stress affect epidermal cell differentiation which leads to either an increase or decrease in stomatal density? Hence, the major aim of this PhD project was to fill some of above discussed gaps in our knowledge by addressing the following specific objectives: (i) investigate the role of EBC in salinity tolerance in quinoa; (ii) identifying key genes related to salt sequestration into EBCs by transcriptome analysis of EBC through comparing bladder-bearing quinoa plants with those that EBCs were mechanically removed; (iii) evaluate the effects of salinity on EBC patterning in quinoa and correlate the extent of variability in this trait with the genetic variation in salinity stress tolerance; (iv) investigate stomata patterning and development and associate the extent of variability in stomata characteristics with genetic variation in salinity stress tolerance; (v) comparing stomatal traits as a component of the tolerant mechanism between halophytic crops and their wild relatives (using cultivated and wild barley as a case study). To provide direct supporting evidence for the role of EBCs that have been postulated to assist halophytes to cope with saline environment, Chenopodium quinoa plants were grown under saline conditions for 5 weeks. One day prior to commencement of salinity stress EBC from all leaves and petioles were gently removed using soft cosmetic brush. Physiological, ionic and metabolic changes in brushed and non-brushed leaves were compared. Gentle removal of EBC did neither initiate wound metabolism nor affected physiology and biochemistry of control-grown plants but had a pronounced effect on salt-grown plants resulting in a salt-sensitive phenotype. Of 91 detected metabolites, more than half (50) were significantly affected by salinity. Removal of EBC has dramatically modified these metabolic changes, with the biggest differences reported for gamma-aminobutyric acid (GABA), proline, sucrose and inositol, affecting ion transport across cellular membranes (as shown in electrophysiological experiments). This work provides the first direct evidence for the role of EBC in salt tolerance in halophytes and attributes this role to (1) key role of EBC as a salt dumper to externally sequester salt load; (2) improved K\(^+\) retention in leaf mesophyll and (3) storage space for several metabolites known to modulate plant ionic relations. To identify key genes related to salt sequestration abilities in EBCs, a transcriptome study was conducted with bladder-bearing and bladderless plants similar to above experiment. Comparing differently expressed genes (DEGs) of brushed and non-brushed leaves grown under 400 mM NaCl using a p-value < 0.05 and fold change > 2 as the significance cut-offs, indicated that 2015 genes were differently expressed where 1399 genes were up-regulated and 616 genes were down-regulated in bladder-bearing leaves. Significant alterations of genes related to ion transport, DNA replication, and genes related to stress signalling in response to salinity stress were determined. Altogether, the finding that the transcriptome of bladder-bearing leaves differed from those of bladderless leaves suggests that EBCs do not function as a passive external store place for salt as it was perceived before but play active metabolic role in quinoa plant. Varietal differences in salinity tolerance of quinoa was explored by evaluation of 114 accessions grown under control and 400 mM NaCl conditions, and different physiological and anatomical characteristics were measured. Accessions were grouped to sensitive, intermediate and tolerant classes based on relative dry weight defined as salinity tolerance index (STI). Results showed a large variability for fresh and dry weights indicating a strong genetic variation for salinity tolerance in quinoa. Bladder density increased in majority of accessions under saline condition while bladder diameter remained unchanged; this resulted in a large variability in a bladder volume as a dependant variable. Stomata density remained unchanged between saline and non-saline conditions while stomata length declined between 3% to 43% among accessions. Correlation analysis indicated a significant positive association between EBC diameter and STI on one hand and EBC volume and STI on the other hand, in a salt-tolerant group. A negative association between STI and stomata length was also found in a salt-tolerant group, suggesting that these plants were able to efficiently regulate stomatal patterning to efficiently balance water loss and CO\(_2\) assimilation under saline condition. Both salt-sensitive and salt-tolerant groups had the same Na\(^+\) content under saline condition; however, a negative association between leaf Na\(^+\) concentration and STI in salt-sensitive plants indicated an efficient Na\(^+\) sequestration into the EBCs in salt-tolerant plants. While sequestration of toxic ions into EBCs is an efficient mechanism contributing to salinity tolerance in quinoa, many halophytes do not utilize EBCs to modulate their tissue ion concentrations but still possess superior salinity tolerance ability. To elucidate possible compensation mechanism(s) underlying superior salinity tolerance in the absence of external salt storage capacity, we have selected four accessions from our previous experiment to address this issue. Whole-plant physiological and electrophysiological characteristics were assessed after 2 days and 3 weeks of 400 mM NaCl stress. The results showed that accession Q21 that had low EBC volume had superior photosynthetic rate and stomatal conductance at both 2 days and 3 weeks of salt stress than the counterpart Q68 with high EBC volume. Both accessions with low EBC volume (Q21 and Q30) utilised Na\(^+\) exclusion at the root level and were capable to maintain low Na\(^+\)concentration in leaves, to compensate for inability to sequester Na\(^+\) load in EBC. These conclusions were further confirmed by electrophysiological experiments showing higher Na\(^+\) efflux from Q21 and Q30 roots as compared with 195 and Q68 as accessions with high EBC volume. Furthermore, accessions with low EBC volume had significantly higher K\(^+\) concentration in their leaves at long-term salinity stress compared to plants with high EBC sequestration ability suggesting that the ability to maintain high K\(^+\) content in mesophyll was as another key compensation mechanism. In the light of importance of stomatal traits as a determinant of salinity tolerance in quinoa, we have extrapolated this work to cereal plants, comparing cultivated (CB; Hordeum vulgare) and wild (WB; Hordeum spontaneum ) barley. Twenty-six genotypes of WB and CB were grown under control and saline conditions and stomatal characteristics, leaf ion content and epidermal strips response to Na\(^+\) and K\(^+\) were measured. WB had higher relative biomass than CB when exposed to salinity stress. Under saline conditions, WB plants were able to keep constant stomata density (SD) while SD significantly decreased in CB. The higher SD in WB also resulted in higher stomatal conductance (gs) under saline conditions, with gs reduction being 51% and 72% in WB and CB, respectively. Furthermore, WB showed faster stomatal response to light, indicating their better ability to adapt to changing environmental conditions. Experiments with isolated epidermal strips indicated that CB genotypes have the higher stomatal aperture when incubated in 80 mM KCl solution, and its aperture declined when KCl was substituted by NaCl, indicating strong preference to KCl for stomatal operation in CB. On the contrary, WB genotype had the highest stomata aperture being exposed to 80 mM NaCl suggesting that WB plants may use Na\(^+\) instead of K\(^+\) for stomata movements. Our data suggest that CB employ a stress-escaping strategy by reducing stomata density, in an attempt to conserve water when grown under salinity conditions. WB, on the contrary, is capable to utilize Na\(^+\) as a cheap osmoticum for stomatal operation. In conclusion, this work has demonstrated that stomatal traits and tissue-tolerance mechanisms represent critical traits enabling plants adaptation to saline environment. These traits should become a focus of future breeding programs aimed to improve salinity tolerance in traditional crops.

To compensate for the lack of capacity for external salt storage in the epidermal bladder cells, quinoa plants employ tissue-tolerance traits, to confer salinity stress tolerance. Our previous studies indicated that sequestration of toxic Na+ and Cl− ions into epidermal bladder cells (EBCs) is an efficient mechanism conferring salinity tolerance in quinoa. However, some halophytes do not develop EBCs but still possess superior salinity tolerance. To elucidate the possible compensation mechanism(s) underlying superior salinity tolerance in the absence of the external salt storage capacity, we have selected four quinoa accessions with contrasting patterns of EBC development. Whole-plant physiological and electrophysiological characteristics were assessed after 2 days and 3 weeks of 400 mM NaCl stress. Both accessions with low EBC volume utilised Na+ exclusion at the root level and could maintain low Na+ concentration in leaves to compensate for the inability to sequester Na+ load in EBC. These conclusions were further confirmed by electrophysiological experiments showing higher Na+ efflux from roots of these varieties (measured by a non-invasive microelectrode MIFE technique) as compared to accessions with high EBC volume. Furthermore, accessions with low EBC volume had significantly higher K+ concentration in their leaves upon long-term salinity exposures compared to plants with high EBC sequestration ability, suggesting that the ability to maintain high K+ content in the leaf mesophyll was as another important compensation mechanism.

Wild barley Hordeum spontaneum (WB) is the progenitor of a cultivated barley Hordeum vulgare (CB). Understanding efficient mechanisms evolved by WB to cope with abiotic stresses may open prospects of transferring these promising traits to the high yielding CB genotypes. This study aimed to investigate the strategies that WB plants utilise in regard to the control of stomatal operation and ionic homeostasis to deal with salinity stress, one of the major threats to the global food security. Twenty-six genotypes of WB and CB were grown under glasshouse conditions and exposed to 300 mM NaCl salinity treatment for 5 weeks followed by their comprehensive physiological assessment. WB had higher relative biomass than CB when exposed to salinity stress. Under saline conditions, WB plants were able to keep constant stomatal density (SD) while SD significantly decreased in CB. The higher SD in WB also resulted in a higher stomatal conductance (gs) under saline conditions, with gs reduction being 51% and 72% in WB and CB, respectively. Furthermore, WB showed faster stomatal response to light, indicating their better ability to adapt to changing environmental conditions. Experiments with isolated epidermal strips indicated that CB genotypes have the higher stomatal aperture when incubated in 80 mM KCl solution, and its aperture declined when KCl was substituted by NaCl. On the contrary, WB genotype had the highest stomatal aperture being exposed to 80 mM NaCl suggesting that WB plants may use Na+ instead of K+ for stomata movements. Overall, our data suggest that CB employ a stress-escaping strategy by reducing stomata density, to conserve water, when grown under salinity conditions. WB, on a contrary, is capable of maintaining relatively constant stomata density, faster stomatal movement and higher gs under saline conditions.

To understand the adaptive strategies employed by plants to deal with saline conditions, two halophytic species [Chenopodium quinoa (quinoa) and Beta maritima (sea beet)] and their glycophytic relatives [Chenopodium album and Beta vulgaris (sugar beet)] were grown under 0−500 mM salt concentrations followed by the comprehensive assessment of their agronomical, ionic, gas exchange characteristics. Salinity levels up to 300 mM NaCl had no adverse effect on quinoa biomass and 200 mM NaCl stimulated sea beet growth. Stomatal conductance decreased in a dose-dependent manner in all species with increasing NaCl concentrations. However, CO2 assimilation rates remained constant or displayed higher values at the medium level of salinity (100−200 mM NaCl) in quinoa, sugar beet and sea beet. High maximum carboxylation rate of Rubisco (Vcmax) and higher rate of electron transport through photosystem II (J) were responsible for the high photosynthetic rates and biomass productions under these conditions. Both characteristics were much higher in halophytic species for the given external NaCl level. Stomatal densities were intrinsically lower in halophytic species (14–34%); these increased with increasing salinity levels in the sugar beet and sea beet while C. album and quinoa stomata remained less dense under saline conditions. Stomata responses to environmental stimuli were much faster in halophytes (16.6–49.7%), and substitution of K+ by Na+ resulted in promotion of stomatal opening under 50 mM NaCl and 50 mM KCl in quinoa. It is concluded that superior salinity tolerance in halophytes is achieved by significantly faster stomatal opening and closure, their ability to discriminate K+ over Na+, and uncoupling of CO2 assimilation from changes in stomatal aperture.

The present study aims at clarifying the differences in photosynthesis parameters, oxidative status and antioxidant enzyme activity among ten triticale genotypes in response to salinity stress; and utilizing the traits as biomarkers for identification of salt-tolerant triticale genotypes. The plants were cultivated in a hydroponic system with or without 220 mM salt concentration. The plants were analyzed for salt tolerance (in term of relative biomass) as well as for the traits at the vegetative (VG) and reproductive (RP) stages. Salinity resulted in significant decline in biomass (55–83%), net photosynthesis rate (12–65%), stomatal conductance (38–83%), transpiration rate (20–56%) and intercellular CO 2 concentrations (7–37%) among genotypes. In contrast, H 2 O 2 and lipid peroxidation (LP) increased markedly in leaves of salt-stressed plants. Activities of total superoxide dismutase (TSOD), catalase (CAT), guaiacol peroxidase and ascorbate peroxidase due to salinity were 0.97–1.84, 0.88–1.96, 0.78–2.23 and 0.61–1.81 times over the control plant, respectively. The photosynthesis attributes, LP and TSOD at the VG stage and LP and CAT at the RP stage showed correlations with scores of salt tolerance (ST) indicating contribution of these traits to ST at least at some part of the plant growth stages, while no connection was found between ST with POD and CAT. Collectively, membrane integrity was a suitable indicator for discrimination of genotypes for ST, while photosynthetic capacity and enzymatic defense system cannot be utilized as general selection criteria for ST during screening of relatively large populations of triticale.

Epidermal bladder cells (EBCs) have been postulated to assist halophytes in coping with saline environments. However, little direct supporting evidence is available. Here,Chenopodium quinoaplants were grown under saline conditions for 5weeks. One day prior to salinity treatment, EBCs from all leaves and petioles were gently removed by using a soft cosmetic brush and physiological, ionic and metabolic changes in brushed and non‐brushed leaves were compared. Gentle removal of EBC neither initiated wound metabolism nor affected the physiology and biochemistry of control‐grown plants but did have a pronounced effect on salt‐grown plants, resulting in a salt‐sensitive phenotype. Of 91 detected metabolites, more than half were significantly affected by salinity. Removal of EBC dramatically modified these metabolic changes, with the biggest differences reported for gamma‐aminobutyric acid (GABA), proline, sucrose and inositol, affecting ion transport across cellular membranes (as shown in electrophysiological experiments). This work provides the first direct evidence for a role of EBC in salt tolerance in halophytes and attributes this to (1) a key role of EBC as a salt dump for external sequestration of sodium; (2) improved K+retention in leaf mesophyll and (3) EBC as a storage space for several metabolites known to modulate plant ionic relations.

Physiological traits, which are positively associated with yield under salt-stress conditions, can be useful selection criteria in screening for salt tolerance. We examined whether chlorophyll (Chl) content can be used as screening criterion in wheat. Our study involved 5 wheat genotypes under both saline and nonsaline field conditions as well as in a sand-culture experiment. Salt stress reduced significantly biomass, grain yield, total Chl and both Chl a and b in all genotypes. In the sand-culture experiment, Chl accumulation was higher in PF70354/BOW, Ghods, and H499.71A/JUP genotypes at nonsaline control, moderate, and high salt concentrations, respectively. In the field experiment, genotype H499.71A/JUP belonged to those with the highest Chl density. The SPAD (Soil Plant Analysis Development) meter readings were linearly related to Chl content both in the sand-culture and in the field experiment. However, salt stress affected the calibration of SPAD meter. Therefore, separate Chl-SPAD equations were suggested for saline and nonsaline conditions. The correlation coefficients between the grain yield and SPAD were positive and significant both in the sand culture and in the field experiment. These findings suggested that SPAD readings could be used as a tool for rapid assessment of relative Chl content in wheat genotypes. It could be used for the indirect selection of high-yielding genotypes of wheat under saline condition in sand-culture and field experiments.

Irrigation by highly sodic water has been practiced only in recent years in Iran but has led to impaired productivity of thousands of hectares of agricultural lands. So, the present study was set out to evaluate the effectiveness of different rates and sizes of gypsum as an amendment which improves the physical and chemical properties of soil and crop productivity. A field experiment was conducted in a sodic soil at a farmer's field in Ramjerd, Fars. The treatments consisted of two gypsum granule sizes (1–10 mm and

To examine the impact of long-term salinity on triticale, two salt-tolerant (ET-84-15 and ET-86-9) and two salt-sensitive (ET-85-17 and Jouvanilo) genotypes were grown in a sand culture containing Hoagland solution with 200 mM NaCl. Lipid peroxidation (LPO), hydrogen peroxide (H2O2), photosynthetic parameters, and antioxidant enzymes including catalase (CAT), guaiacol peroxidase (GPOD), superoxide dismutase (SOD), and ascorbate peroxidase (APX) were analyzed at the late tillering (LT) and flowering (FL) stages. A substantial reduction was found in the net photosynthetic rate, stomatal conductance, and transpiration rate of the triticale genotypes due to salt stress, with a more noticeable decline in the sensitive ones. Salt-treated plants indicated the presence of high amounts of H2O2 and LPO with a subsequent increase in the activities of the enzymes’ SOD, CAT, and GPOD in comparison with the control treatment. Conversely, APX activities remained unaltered or decreased slightly by salt stress. The salt-tolerant genotypes exhibited lower H2O2 and LPO, and displayed increased activities of the enzymes participating in the reactive oxygen scavenging system except for APX. The activities of the antioxidant enzymes under both the saline and non-saline conditions were found to be higher at the FL stage than at the LT one. This may explain partly the reason for why triticale is more tolerant at the FL stage. These results clearly demonstrate that the activation of SOD, CAT, and GPOD could contribute to the salt-stress tolerance in triticale.

Waterlogging and salinity stresses significantly affect crop growth and global food production, and these stresses are often interrelated because waterlogging can lead to land salinisation by transporting salts to the surface. Although the physiological and molecular mechanisms of plant responses to each of these environmental constraints have been studied in detail, fewer studies have dealt with potential mechanisms underlying plant tolerance to the combined stress. This gap in knowledge is jeopardising the success of breeding programs. In the present work we studied the physiological and agronomical responses of 12 barley varieties contrasting in salinity stress tolerance to waterlogging (WL), salinity (NaCl) and combined (WL/NaCl) stresses. Stress damage symptoms were much greater in plants under combined WL/NaCl stress than those under separate stresses. The shoot biomass, chlorophyll content, maximum photochemical efficiency of PSII and shoot K+ concentration were significantly reduced under WL/NaCl conditions, whereas shoot Na+ concentration increased. Plants exposed to salinity stress showed lower damage indexes compared with WL. Chlorophyll fluorescence Fv/Fm value showed the highest correlation with the stress damage index under WL/NaCl conditions (r = –0.751) compared with other measured physiological traits, so was nominated as a good parameter to rank the tolerance of varieties. Average FW was reduced to 73 ± 2, 52 ± 1 and 23 ± 2 percent of the control under NaCl, WL and combined WL/NaCl treatments respectively. Generally, the adverse effect of WL/NaCl stress was much greater in salt-sensitive varieties than in more tolerant varieties. Na+ concentrations of the shoot under control conditions were 97 ± 10 µmol g–1 DW, and increased to 1519 ± 123, 179 ± 11 and 2733 ± 248 µmol g–1 under NaCl, WL and combined WL/NaCl stresses respectively. K+ concentrations were 1378 ± 66, 1260 ± 74, 1270 ± 79 and 411 ± 92 µmol g–1 DW under control, NaCl, WL and combined WL/NaCl stresses respectively. No significant correlation was found between the overall salinity stress tolerance and amount of Na+ accumulated in plant shoots after 15 days of exposure to 250 mM NaCl stress. However, plants exposed to combined salinity and WL stress showed a negative correlation between shoot Na+ accumulation and extent of salinity damage. Overall, the reported results indicate that K+ reduction in the plants under combined WL/NaCl stress, but not stress-induced Na+ accumulation in the shoot, was the most critical feature in determining the overall plant performance under combined stress conditions.