Shoot Sodium Research Articles

Effects of Funneliformis mosseae on the growth and rhizosphere bacterial communities of Astragalus adsurgens and Stipa grandis under combined cadmium and salt stress

The phytoremediation efficiency of heavy metal‐contaminated saline soils is limited by low plant biomass and low accumulation of salt or heavy metals. Arbuscular mycorrhizal fungi (AMF) can directly promote plant growth or indirectly affect plant growth by regulating rhizosphere microbial communities; however, few studies have investigated the regulation of AMF on rhizosphere bacteria in heavy metal‐contaminated saline soils. This study investigated the effects of AMF (Funneliformis mosseae) on the growth and rhizosphere bacteria in Astragalus adsurgens Pall. and Stipa grandis P. Smirn. in cadmium (Cd)‐contaminated saline soils. The results revealed that F. mosseae improved the growth of the two grasses through distinct strategic mechanisms. In A. adsurgens, F. mosseae decreased shoot sodium ion (Na+) and Cd concentrations, increased Na+, Cd, and nutrient accumulations, enhanced the stability of the interaction network of the top 15 bacterial species with significant differences, and resulted in higher resistance of bacteria to external disturbances. F. mosseae increased the relative abundances of Paludibaculum, Pedomicrobium, and Aquicella, which positively correlated with biomass, Na+, and Cd accumulations. In S. grandis, F. mosseae promoted Na+, Cd, and nutrient accumulations and regulated interactions among the top 15 bacterial species with significant differences. Total nodes, total links, and average degree of the network increased, indicating a closer and more complex relationship between bacteria. F. mosseae increased the relative abundance of Devosia, Exiguobacterium, Pseudoxanthomonas, and Aliihoeflea, which positively correlated with biomass, Na+, and Cd accumulations. This study presented data to support plant‐mediated remediation of heavy metal‐contaminated saline soils using AMF symbiosis.

Role of Humic Acid on Inducing Salt Tolerance of Ivy Geranium (Pelargonium peltatum L.) Plants

Saline water is used in floriculture as an alternative to freshwater in arid regions such as Saudi Arabia (SA). However, salt stress considerably accelerates serious physio-biochemical changes associated with a decline in plant establishment. Recently, humic acid (HA) foliar spraying has induced plant stress tolerance in the era of climate change; however, its precise roles in the floriculture industry within saline conditions are not yet well documented. A factorial pot experiment throughout the 2022/2023 season was conducted in the Nursery of Sustainability and Environmental Developmental Department, King Saud University, Riyadh, SA, to evaluate the potential effects of HA (0, 500, 1000 and 2000 mg/L) on growth, flowering and some physiological characteristics of Ivy geranium (Pelargoniumpeltatum) plants irrigated with saline water (230 “control”, 2000 and 4000 mg/L NaCl). Irrigation with saline water markedly inhibited plant growth, flowering attributes, the chlorophyll index, as well as macro and micro-nutrient levels, but increased the content of iron, sodium and proline in plant shoots relative to plants irrigated with non-salinized water. However, HA mainly at 1000 mg/L significantly improved plant growth, flowering capacity, nutrient status, proline accumulation and chlorophyll index under salinized or non-salinized irrigation water. Additionally, spraying of HA concentrations (500, 1000 and 2000 mg/L) under normal or salinity conditions significantly increased shoot sodium content relative to non-treated plants under such salinity levels. Our findings highlight the significance of HA concentrations (500, 1000 and 2000 mg/L) in improving the salt tolerance of Ivy geranium. Within the scarcity of irrigation water, it is recommended to irrigate Ivy geranium with saline water up to 4000 mg/L NaCl associated with spraying HA concentrations in special 1000 mg/L.

Effects of a Furrow-Bed Seeding System on Stand Establishment, Soil Bacterial Diversity, and the Yield and Quality of Alfalfa Under Saline Condition.

Salt stress account for large decreases in crop yield all over the world. Furrow-bed system is an efficient practice to promote plant growth in saline soil. However, the effects of Furrow-bed system on the soil environment and the growth of alfalfa (Medicago sativa L.) in salinity are not clear. For a wider and more detail evaluation, alfalfa were planted in saline sandy loam soil in fall, the effects of two plant systems (FU, furrow-bed seeding system; FL, flat-bed seeding system) on soil moisture, root zone salinity, soil microbial community structure, seedling emergence number in the early stage of the growth period and soil nutrient contents, alfalfa production characteristics in the second growth year were determined in a 2-year field experiment. The result showed that, compared with FL, FU resulted in increased soil moisture content and seedling emergence, and significantly reduced relative abundance of Actinobacteria and Choroflexi in soil, but it did not affect root zone salinity at the seedling stage. In April of second growth year, the soil salinity was lower, and the soil available phosphorus, potassium, nitrogen, and soil organic matter contents of the root zone were higher in FU than in FL. Compared with FL, FU resulted in increased yield (by 37.5%), protein content (by 3.6%), and potassium concentration (by 33.2%), and decreased ash content (by 7.7%), and sodium concentration (by 19.0%) in alfalfa plants. Pearson’s correlation analysis indicated that the increased yield was positively correlated with seedling emergence, soil available potassium, total nitrogen, and organic matter contents, and shoot potassium content and negatively correlated with shoot sodium content. The relative abundance of Actinobacteria was negatively correlated with alfalfa ash, calcium, and sodium concentrations, and positively correlated with shoot potassium content. Taken together, the results indicate that Furrow-bed seeding in early fall alleviated salt stress of alfalfa and have the potential to enhance the yield and quality of alfalfa cultivated in saline soils by improving the soil environment and regulating the growth and physiology of alfalfa. Graphical

Rootstock type influences salt exclusion response of grafted Shiraz under salt treatment at elevated root zone temperature

Background and Aims The temperature of the upper soil zone lags but strongly correlates with prevailing air temperature. The effect of root zone (RZ) temperature on shoot salt exclusion is poorly understood. The aim was to gain a better understanding of the effect of RZ temperature on the salt exclusion, growth and stomatal conductance of Shiraz grafted onto a range of rootstock genotypes. Methods and Results Glasshouse grown Shiraz on 140 Ruggeri, K51-40 and six K51-40 × 140 Ruggeri hybrid rootstocks were assessed at a cool (mean 19.3°C) and hot (mean 30.8°C) RZ temperature, plus or minus salt treatment of 50 mmol/L chloride with mixed cations. After 28 days, plants were destructively harvested. Chloride concentration in laminae, petioles and roots and cation concentration in laminae and roots were measured. All rootstocks showed enhanced shoot sodium exclusion under salt treatment at the hot RZ temperature demonstrated by significantly lower sodium concentration in laminae and higher concentration in roots. Shoot chloride exclusion capacity of salt-treated K51-40 declined, while that of 140 Ruggeri and two hybrid rootstocks improved at the hot RZ temperature. Conclusions Shoot chloride exclusion varied widely among rootstock genotypes subjected to salinity and hot RZ temperature, compared with shoot sodium exclusion, reflecting its control by multiple genes and apparent differential sensitivity to environmental cues. Significance of the Study The genetic potential of 140 Ruggeri to enhance shoot sodium and chloride exclusion at elevated RZ temperature was demonstrated, highlighting its potential as a breeding parent for rootstock improvement, to meet anticipated future challenges of rising RZ temperature and salinity.

Meta-analysis and validation of genomic loci governing seedling and reproductive stage salinity tolerance in rice.

Identification of concurrent genomic regions contributing tolerance to salinity at the seedling and reproductive stages were done using 45 quantitative trait loci (QTL) mapping studies reporting 915 individual QTLs. The QTL-data were used to perform a meta-analysis to predict, validate and analyze the Meta-QTLs governing component traits contributing to salinity tolerance. We predicted a total of 65 and 49 Meta-QTLs distributed across the genome governing seedling and reproductive stage salinity tolerance, respectively. Salinity stress (EC ~10.0dSm-1 ) was evaluated in a set of 32 genotypes grown hydroponically, from these eight extreme (highly tolerant and highly susceptible) genotypes were selected for validation of significant Meta-QTLs. Another set of eight previously known and reported (highly tolerant and highly susceptible) genotypes were evaluated under saline micro plot conditions (EC ~8.0dSm-1 ) and used for validation of significant Meta-QTLs for reproductive stage salinity tolerance. The microsatellite marker "RM5635" linked to MSQTL4.2 (~295.43 kb) was able to clearly differentiate contrasting genotypes for seedling stage salinity tolerance, whereas at the reproductive stage, none of the markers were able to validate the predicted Meta-QTL for salinity tolerance. Earlier reported, gene expression studies were used for candidate gene analysis of validated MSQTL4.2, which indicated the down regulation of Os04g0423100, a gene encoding Mono-oxygenase-FAD binding domain containing protein. The traits associated with this Meta-QTL were root and shoot sodium and potassium concentration and leaf chlorophyll content. The identified and validated genomic region assumes a great significant role in seedling stage salinity tolerance in rice, and it can be used for marker-assisted backcross breeding programs.

Diversity of Sodium Transporter HKT1;5 in Genus Oryza

Asian cultivated rice shows allelic variation in sodium transporter, OsHKT1;5, correlating with shoot sodium exclusion (salinity tolerance). These changes map to intra/extracellularly-oriented loops that occur between four transmembrane-P loop-transmembrane (MPM) motifs in OsHKT1;5. HKT1;5 sequences from more recently evolved Oryza species (O. sativa/O. officinalis complex species) contain two expansions that involve two intracellularly oriented loops/helical regions between MPM domains, potentially governing transport characteristics, while more ancestral HKT1;5 sequences have shorter intracellular loops. We compared homology models for homoeologous OcHKT1;5-K and OcHKT1;5-L from halophytic O.coarctata to identify complementary amino acid residues in OcHKT1;5-L that potentially enhance affinity for Na+. Using haplotyping, we showed that Asian cultivated rice accessions only have a fraction of HKT1;5 diversity available in progenitor wild rice species (O. nivara and O. rufipogon). Progenitor HKT1;5 haplotypes can thus be used as novel potential donors for enhancing cultivated rice salinity tolerance. Within Asian rice accessions, 10 non-synonymous HKT1;5 haplotypic groups occur. More HKT1;5 haplotypic diversities occur in cultivated indica gene pool compared to japonica. Predominant Haplotypes 2 and 10 occur in mutually exclusive japonica and indica groups, corresponding to haplotypes in O. sativa salt-sensitive and salt-tolerant landraces, respectively. This distinct haplotype partitioning may have originated in separate ancestral gene pools of indica and japonica, or from different haplotypes selected during domestication. Predominance of specific HKT1;5 haplotypes within the 3 000 rice dataset may relate to eco-physiological fitness in specific geo-climatic and/or edaphic contexts.

Sodium hyperaccumulators in the Caryophyllales are characterized by both abnormally large shoot sodium concentrations and [Na]shoot/[Na]root quotients greater than unity.

Some Caryophyllales species accumulate abnormally large shoot sodium (Na) concentrations in non-saline environments. It is not known whether this is a consequence of altered Na partitioning between roots and shoots. This paper tests the hypotheses (1) that Na concentrations in shoots ([Na]shoot) and in roots ([Na]root) are positively correlated among Caryophyllales, and (2) that shoot Na hyperaccumulation is correlated with [Na]shoot/[Na]root quotients. Fifty two genotypes, representing 45 Caryophyllales species and 4 species from other angiosperm orders, were grown hydroponically in a non-saline, complete nutrient solution. Concentrations of Na in shoots and in roots were determined using inductively coupled plasma mass spectrometry (ICP-MS). Sodium concentrations in shoots and roots were not correlated among Caryophyllales species with normal [Na]shoot, but were positively correlated among Caryophyllales species with abnormally large [Na]shoot. In addition, Caryophyllales species with abnormally large [Na]shoot had greater [Na]shoot/[Na]root than Caryophyllales species with normal [Na]shoot. Sodium hyperaccumulators in the Caryophyllales are characterized by abnormally large [Na]shoot, a positive correlation between [Na]shoot and [Na]root, and [Na]shoot/[Na]root quotients greater than unity.

Combined Effect of Salinity and Zinc Nutrition on Some Physiological and Biochemical Properties of Rosemary

ABSTRACT Salinity and reducing its destructive effects on plant, soil, and water is among the most important challenges in agricultural lands. This study aims to evaluate the effect of zinc (Zn) and salinity on some physiological and biochemical properties of rosemary. A greenhouse experiment with two levels of Zn (0 and 20 mg kg−1) and salinity of sodium chloride (0, 60, and 120 mM) in a completely randomized design was used. Salinity decreased dry weight and concentrations of K, Ca, Mg, and Zn in rosemary shoots. However, it increased electrolyte leakage, shoot sodium concentration, phenolic compounds, and catalase activity. Zinc application increased rosemary dry weight by 13% and 9% under salinity levels of 0 and 60 mM NaCl, respectively. However, at higher salinity level (120 mM), it could not ameliorate the negative impact of salinity. Zinc improved the growth of rosemary under salinity stress by increasing the cell membrane stability, increasing shoot K, Ca, Mg, and Zn concentrations, and decreasing shoot Na concentration. The concentration of phenolic compounds in the leaves of rosemary grown under the salinity levels of 0 and 60 mM NaCl increased under the influence of Zn application. Nevertheless, the phenolic content remained unchanged under 120 mM NaCl salinity level. In this study, Zn addition increased catalase activity under all salinity levels. According to the results, optimum soil Zn application can be considered as an efficient and rapid solution for increasing rosemary growth and its tolerance to salinity stress.

Shoot sodium exclusion in salt stressed barley (Hordeum vulgare L.) is determined by allele specific increased expression of HKT1;5

High affinity potassium transporters (HKT) are recognized as important genes for crop salt tolerance improvement. In this study, we investigated HvHKT1;5 as a candidate gene for a previously discovered quantitative trait locus that controls shoot Na+ and Na+/K+ ratio in salt-stressed barley lines on a hydroponic system. Two major haplotype groups could be distinguished for this gene in a barley collection of 95 genotypes based on the presence of three intronic insertions; a designated haplotype group A (HGA, same as reference sequence) and haplotype group B (HGB, with insertions). HGB was associated with a much stronger root expression of HKT1;5 compared to HGA, and consequently higher K+ and lower Na+ and Cl− concentrations and a lower Na+/K+ ratio in the shoots three weeks after exposure to 200 mM NaCl. Our experimental results suggest that allelic variation in the promoter region of the HGB gene is linked to the three insertions may be responsible for the observed increase in expression of HvHKT1;5 alleles after one week of salt stress induction. This study shows that in barley - similar to wheat and rice - HKT1;5 is an important contributor to natural variation in shoot Na+ exclusion.

Transcriptional variation is associated with differences in shoot sodium accumulation in distinct barley varieties

Soil salinity causes large productivity losses for agriculture worldwide. Barley has been identified as one of the more salt tolerant staple crops compared to wheat and rice. Identification of genes and allelic variations underlying various salt tolerance mechanisms in barley will be a practical contribution towards the development of cereal lines with greater salinity tolerance. Here, RNA from six barley varieties with varying leaf blade and sheath Na+ accumulation following salt (NaCl) treatment were sequenced. Differential gene expression analysis, variant calling and gene co-regulatory network analysis was conducted to identify potential molecular components underlying the shoot Na+ phenotypes. We identified novel alleles of HKT1;5 that could be responsible for high Na+ accumulation in blade and sheath. Furthermore, through statistical modelling of gene expression, a Na+/H+ Exchanger (NHX) gene was identified as a candidate for high sheath Na+ accumulation. Through co-expression networks, we discovered expression pattern variation for genes related to terpenoid phenylpropanoid and flavonoid metabolism amongst the six varieties. The gene candidates identified in this study provide us with targets of interest for future characterisation of molecular mechanisms that may contribute to salt stress tolerance in barley.

Arbuscular mycorrhizal fungus and rhizobacteria affect the physiology and performance ofSulla coronariaplants subjected to salt stress by mitigation of ionic imbalance

AbstractSalt stress has become a major menace to plant growth and productivity. The main goal of this study was to investigate the effect of inoculation with the arbuscular mycorrhizal fungi (AMF;Rhizophagus intraradices) in combination or not with plant growth‐promoting rhizobacteria (PGPR;Pseudomonassp. (Ps) andBacillus subtilis) on the establishment and growth ofSulla coronariaplants under saline conditions. Pot experiments were conducted in a greenhouse andS. coronariaseedlings were stressed with NaCl (100 mM) for 4 weeks. Plant biomass, mineral nutrition of shoots and activities of rhizosphere soil enzymes were assessed. Salt stress significantly reduced plant growth while increasing sodium accumulation and electrolyte leakage from leaves. However, inoculation with AMF, whether alone or combined with the PGPRPseudomonassp. alleviated the salt‐induced reduction of dry weight. Inoculation with only AMF increased shoot nutrient concentrations resulting in higher K+: Na+, Ca2+: Na+, and Ca2+: Mg2+ratios compared to the non‐inoculated plants under saline conditions. The co‐inoculation with AMF andPseudomonassp. under saline conditions lowered shoot sodium accumulation, electrolyte leakage and malondialdehyde (MDA) levels compared to non‐inoculated plants and plants inoculated only with AMF. The findings strongly suggest that inoculation with AMF alone or co‐inoculation with AMF andPseudomonassp. can alleviate salt stress of plants likely through mitigation of NaCl‐induced ionic imbalance, thereby improving the nutrient profile.

Arbuscular mycorrhizal fungi alleviate boron toxicity in Puccinellia tenuiflora under the combined stresses of salt and drought

To investigate the effect of arbuscular mycorrhizal fungi (AMF) on boron (B) toxicity in plants under the combined stresses of salt and drought, Puccinellia tenuiflora was grown in the soil with the inoculation of Funneliformis mosseae and Claroideoglomus etunicatum. After three weeks of treatment, the plants were harvested to determine mycorrhizal colonization rates, plant biomass, as well as tissue B, phosphorus, sodium, and potassium concentrations. The results show that the combined stresses reduced mycorrhizal colonization. Mycorrhizal inoculation significantly increased plant biomass while reduced shoot B concentrations. Mycorrhizal inoculation also slightly increased shoot phosphorus and potassium concentrations, and reduced shoot sodium concentrations. F. mosseae and C. etunicatum were able to alleviate the combined stresses of B, salt, and drought. The two fungal species and their combination showed no significant difference in the alleviation of B toxicity. It is inferred that AMF is able to alleviate B toxicity in P. tenuiflora by increasing biomass and reducing tissue B concentrations. The increase in plant phosphorus and potassium, as well as the decrease in sodium accumulation that induced by AMF, can help plant tolerate the combined stresses of salt and drought. Our findings suggest that F. mosseae and C. etunicatum are potential candidates for facilitating the phytoremediation of B-contaminated soils with salt and drought stress.

Pomegranate Growth Affected by Arbuscular Mycorrhizae, Phosphorus Fertilizer, and Irrigation Water Salinity

ABSTRACTPomegranate (Punica granatum L.) symbiosis with arbuscular mycorrhizae fungi (AMF) is a strategy in saline soils. In this study, two AMF (+AMF and –AMF), two phosphorus (P) fertilizer (+ P and –P), and three irrigation salinity (1, 4, and 8 dS m−1) treatments were studied. The highest salinity level decreased the root colonization by hyphae. Plant growth parameters including shoot dry weight, leaf surface area, and plant height were negatively affected by salinity. However, the growth parameters improved in AMF treatments. Salinity decreased the shoot P concentration and increased the shoot chlorine (Cl). The root and shoot sodium (Na) concentrations were the greatest in unfertilized and P-fertilized treatments, respectively. AMF treatment improved the root and shoot P concentration and reduced the negative effect of salinity on shoot Cl concentrations. In conclusion, the effects of AMF symbiosis on growth and tissue elements concentration depend on irrigation water salinity and P fertilization.

Morphological and Physiological Responses of Ten Ornamental Taxa to Saline Water Irrigation

Because of limited supply of high-quality water, alternative water sources have been used for irrigation in water-scarce regions. However, alternative waters usually contain high salt levels, which can cause salt damage on salt-sensitive plants. A greenhouse study was conducted to evaluate the relative salt tolerance of 10 common ornamental taxa to saline water irrigation. The 10 taxa studied were Chaenomeles speciosa ‘Orange Storm’ and ‘Pink Storm’ (Chaenomeles Double Take™); Diervilla rivularis ‘G2X885411’, ‘G2X88544’ (Diervilla Kodiak®, Black, Orange, and Red, respectively), and ‘Smndrsf’; Forsythia ×intermedia ‘Mindor’ (Forsythia Show Off®); Hibiscus syriacus ‘ILVOPS’ (Hibiscus Purple Satin®); Hydrangea macrophylla ‘Smhmtau’ and ‘Smnhmsigma’ (Hydrangea Let’s Dance® Blue Jangles® and Rave, respectively); and Parthenocissus quinquefolia ‘Troki’ (Parthenociss quinquefolia Red Wall®). Plants were irrigated with a nutrient solution at an electrical conductivity (EC) of 1.2 dS·m−1 (control) or saline solutions at EC of 5.0 or 10.0 dS·m−1 (EC 5 or EC 10) eight times on a weekly basis. The results indicated that the 10 ornamental taxa had different morphological and physiological responses to salinity. The C. speciosa and D. rivularis plants in EC 5 had severe salt foliar damage, whereas those in EC 10 were dead. Hibiscus syriacus ‘ILVOPS’ performed well in EC 5 treatment with a shoot dry weight (DW) reduction of 26%, but those in EC 10 had severe foliar salt damage. Hydrangea macrophylla, F. ×intermedia ‘Mindor’ and P. quinquefolia ‘Troki’ were the most salt tolerant with minor foliar salt damage. The two H. macrophylla cultivars had the highest shoot sodium (Na) and chlorine (Cl) concentrations with a visual quality of 3 (scale 0 to 5 with 0 for dead plants and 5 for excellent performance), indicating that H. macrophylla plants adapted to elevated salinity by tolerating high Na and Cl concentrations in leaf tissue. Forsythia ×intermedia ‘Mindor’ and P. quinquefolia ‘Troki’ had relatively low leaf Na and Cl concentration, indicating that both taxa are capable of excluding Na and Cl. Chaenomeles speciosa and D. rivularis were sensitive to salinity with great growth reduction, severe foliar salt damage, and high Na and Cl accumulation in leaf tissue.

Nitrate-dependent shoot sodium accumulation and osmotic functions of sodium in Arabidopsis under saline conditions.

Improving crop plants to be productive in saline soils or under irrigation with saline water would be an important technological advance in overcoming the food and freshwater crises that threaten the world population. However, even if the transformation of a glycophyte into a plant that thrives under seawater irrigation was biologically feasible, current knowledge about Na+ effects would be insufficient to support this technical advance. Intriguingly, crucial details about Na+ uptake and its function in the plant have not yet been well established. We here propose that under saline conditions two nitrate-dependent transport systems in series that take up and load Na+ into the xylem constitute the major pathway for the accumulation of Na+ in Arabidopsis shoots; this pathway can also function with chloride at high concentrations. In nrt1.1 nitrate transport mutants, plant Na+ accumulation was partially defective, which suggests that NRT1.1 either partially mediates or modulates the nitrate-dependent Na+ transport. Arabidopsis plants exposed to an osmotic potential of -1.0 MPa (400 mOsm) for 24h showed high water loss and wilting in sorbitol or Na/MES, where Na+ could not be accumulated. In contrast, in NaCl the plants that accumulated Na+ lost a low amount of water, and only suffered transitory wilting. We discuss that in Arabidopsis plants exposed to high NaCl concentrations, root Na+ uptake and tissue accumulation fulfil the primary function of osmotic adjustment, even if these processes lead to long-term toxicity.

Evolutionary origins of abnormally large shoot sodium accumulation in nonsaline environments within the Caryophyllales.

Summary The prevalence of sodium (Na)‐‘hyperaccumulator’ species, which exhibit abnormally large shoot sodium concentrations ([Na]shoot) when grown in nonsaline environments, was investigated among angiosperms in general and within the Caryophyllales order in particular.Shoot Na concentrations were determined in 334 angiosperm species, representing 35 orders, grown hydroponically in a nonsaline solution.Many Caryophyllales species exhibited abnormally large [Na]shoot when grown hydroponically in a nonsaline solution. The bimodal distribution of the log‐normal [Na]shoot of species within the Caryophyllales suggested at least two distinct [Na]shoot phenotypes within this order. Mapping the trait of Na‐hyperaccumulation onto the phylogenetic relationships between Caryophyllales families, and between subfamilies within the Amaranthaceae, suggested that the trait evolved several times within this order: in an ancestor of the Aizoaceae, but not the Phytolaccaceae or Nyctaginaceae, in ancestors of several lineages formerly classified as Chenopodiaceae, but not in the Amaranthaceae sensu stricto, and in ancestors of species within the Cactaceae, Portulacaceae, Plumbaginaceae, Tamaricaceae and Polygonaceae.In conclusion, a disproportionate number of Caryophyllales species behave as Na‐hyperaccumulators, and multiple evolutionary origins of this trait can be identified within this order.

Effect of humic acid on some vegetative traits and ion concentrations of Mexican Lime (Citrus aurantifolia Swingle) seedlings under salt stress

Effects of humic acid on some vegetative characteristics and mineral concentrations of Mexican lime were investigated under different salinity concentrations. Four doses of humic acid (0, 1500, 3000 and 4000 mg/kg soil) and four salinity levels (1500, 2500, 3500 and 4500 µmos) were applied on Mexican lime seedlings. Experiment was conducted as a factorial arrangement based on a completely randomized design. The results showed that humic acid had a positive influence on plant height under salinity stress. Shoot number was significantly increased by application of humic acid under salinity stress conditions. In 4500 µmos salinity, application of 4500 mg/kg humic acid caused an increase in shoot fresh and dry weights, root dry weight and shoot potassium concentration. Percentage of sodium was decreased by application of 3000 mg/kg humic acid in the shoot of plants that were exposed to 4500 µmos salinity level. humic acid at 1500 mg/kg caused a reduction in shoot sodium percentage under 3500 µmos salinity level. When compared to the non-treated plants, application of humic acid led to a decline in chloride percentage in Mexican lime seedlings. In conclusion, 3000 and 4000 mg/kg humic acid can be used to reduce the toxic effects of salinity and also to decrease the uptake of toxic elements such as sodium and chloride in Mexican lime seedlings.

Growth and ion accumulation responses of four grass species to salinity

ABSTRACTIon inclusion or ion exclusion are the two main strategies developed by plants to tolerate saline environments. Shoot sodium (Na+), potassium (K+), and calcium (Ca2+) in four perennial grass species (tall wheatgrass, Nuttall's alkaligrass, creeping foxtail, and switchgrass) treated with nutrient solution salinity levels ranging from 2 to 32 dS m−1 were measured. As the nutrient solution salinity was increased from 2 to 10 dS m−1, tall wheatgrass, creeping foxtail and Nuttall's alkali grass had increased shoot Na+ and decreased Ca2+ concentration while maintaining growth suggesting that these species tolerated these changes in shoot ion concentration. In contrast, switchgrass excluded Na+ from the shoot and maintained K+ and Ca2+ concentrations but suffered dramatic shoot dry weight reduction. Thus, the Na+ exclusion mechanisms present in switchgrass were less efficient in maintaining growth under the 10 dS m−1 nutrient solution treatment than the Na+ inclusion mechanisms used by the other three species.

Alleviation Of Nacl Stress In Summer Squash ‘Eskandrani’ By Foliar Application Of Salicylic Acid

Abstract The experiment was performed to assess the possibility of overcoming NaCl salinity stress by foliar sprays of summer squash ‘Eskandrani’ with salicylic acid (SA) at the concentration of 10-6 M. NaCl treatment caused reduction of shoot fresh weight, leaf number per plant, fruit yield, concentrations of potassium in aerial parts, and the concentration of chlorophyll in leaves. Plants grown under salt stress conditions had higher shoot sodium concentrations than plants untreated with NaCl. Foliar application of SA ameliorated partly the negative effect of NaCl treatment. The beneficial effect of SA was also observed in non-stressed plants, increasing the shoot potassium accumulation and leaf photosynthetic pigments status, and decreasing sodium accumulation in shoots.

Quantitative gene expression analysis of some sodium ion transporters under salinity stress in Aeluropus littoralis

Plant sodium transporters activity is one of the most important salt tolerance mechanisms to keep normal status of cytosolic sodium content. In the present study, expression pattern of genes encoding Na+/H+ antiporters in the plasma membrane (SOS1 gene), vacuolar membrane (NHX1 gene) and H+-ATPase pump (VHA gene) in Aeluropus littoralis under different treatments of NaCl was measured by the semi-quantitative RT-PCR method. Our results indicated that root and shoot sodium contents were increased along with increasing salinity pressure. In response to 200 and 400mM NaCl, mRNA level of SOS1 and NHX1 was increased in the shoot and root tissues, while VHA transcripts were increased only under 400mM of NaCl. Transcripts of VHA-c and NHX1 in root were higher than shoot in all treatments. In general, our results indicated that transcriptional level of SOS1, and NHX1 genes induced in parallel with VHA expression may be involved in controlling cytosolic Na+ concentration in A. littoralis.