Salicylic Acid (SA) Induced Alterations in Growth,Biochemical Attributes and Antioxidant Enzyme Activity in Faba Bean (<Emphasis Type="Italic">Vicia faba</Emphasis> L.) Seedlings under NaCl Toxicity

In the present study we tried to evaluate the effect of salicylic acid (SA) in alleviating the negative effects of salinity stress. NaCl stress (50 and 100 mM) declines the shoot and root length and maximum decrease was observed at 100 mM concentration of NaCl. Similarly shoot dry weight decreased by 57.14% and root dry weight by 67.24% with 100 mM NaCl stress. The pigments and leaf relative water content (LRWC) were also observed to decline with increase in NaCl concentration. However, supplementation of SA to NaCl stressed seedlings showed enhanced length and dry weight of shoot and root. The pigment and LRWC also increased by the application of SA in the present study. NaCl stress also enhanced proline and glycine betaine (GB) by 3.01 and 2.04 folds, respectively; further enhancement was recorded by the application of SA. Hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) content also showed rise in accumulation, however, seedlings treated with SA and NaCl (100 mM + SA) declines the H₂O₂ accumulation to 1.90 from 2.45 folds and MDA to 1.69 from 2.34 folds over the control. Antioxidants were observed to increase with NaCl concentration and further increase was recorded by the application of SA. Indoleacetic acid (IAA) and indole butyric acid (IBA) decreased by 36.60 and 44.16%, respectively, and ABA increased by 750% with 100 mM NaCl. Addition of SA to NaCl stressed seedlings enhanced the IAA and IBA and decreased the ABA concentration to appreciable level. NaCl is also responsible for the higher accumulation of Na⁺ and Na⁺/K⁺ ratio and decreased uptake of Ca²⁺ and K⁺. Supplementation of SA decreased the Na⁺ accumulation and enhanced the uptake of Ca²⁺ and K⁺ in NaCl stressed seedlings. In conclusion, SA supplementation mitigates the negative effects of NaCl toxicity in faba bean seedlings through the modulation of different osmoprotectants, antioxidants and nutrients uptake.     

Effects of exogenous glucose on seed germination and antioxidant capacity in wheat seedlings under salt stress

Glucose (Glc) is an essential signaling molecule that controls plant development and gene expression, but little is known about its role in salt stress resistance on seed germination and plant growth. Here we report the effects of exogenous Glc on wheat seed germination and seedling growth under salt stress. The treatments used were 0 and 200?mM NaCl solutions supplemented with each of four Glc concentrations of 0, 0.1, 0.5 and 50 mM. The results showed that salt alone significantly inhibited seeds germination and reduced the growth of wheat seedlings. Addition of exogenous Glc in the salt solution attenuated the salt stress effects in a dose-dependent manner of Glc, as indicated by enhancement of the growth of celoeptile and radicle. Glc addition also showed significant reversal of salt stress in chlorophyll decay, water loss, dry weight, root length and accumulation of proline. The Glc-induced salt stress resistance was associated with enhanced K⁺ and K⁺/Na⁺ ratio in leaves, and activated antioxidant enzymes activities, thus decreasing thiobarbituric acid reactive substances (TBARS) and malondialdehyde (MDA) contents. As our knowledge this is the first report to show the protective effects of exogenous Glc against salt-induced oxidative damage in wheat seedlings associating with the evidences of ion homeostasis in cells and a better antioxidant system.     

Changes in growth,photosynthetic capacity and ionic relations in spring wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.) due to pre-sowing seed treatment with polyamines

The influence of pre-sowing seed treatment with polyamines (2.5 mM putrescine, 5.0 mM spermidine and 2.5 mM spermine) on growth, photosynthetic capacity, and ion accumulation in two spring wheat (Triticum aestivum L.) cultivars MH-97 (intolerant) and Inqlab-91 (tolerant) was examined. The primed seeds of each treatment and non-primed seeds were sown in a field containing 15 dS m⁻¹ NaCl. Although all three polyamines were effective in improving shoot growth and grain yield in both cultivars under saline conditions, the effect of spermine was very pronounced particularly in improving grain yield. Different priming agents did not affect the net CO₂ assimilation rate and transpiration rate of either cultivar. However, pre-treatment with spermidine increased stomatal conductance (g_s) in the tolerant cultivar, whereas with spermine stomatal conductance decreased in the intolerant cultivar under salt stress. Priming agents had different effects on the accumulation of different ions in wheat plant tissues. When spermidine and distilled water were used as priming agents, they were effective in reducing shoot [Na⁺] in the tolerant and intolerant cultivars, respectively under saline conditions. Although all priming agents caused an increase in shoot [K⁺], distilled water was more effective in improving shoot [K⁺] in both cultivars under salt stress. Pre-treatment with spermidine was very effective in reducing shoot [Cl⁻] under saline conditions particularly in the tolerant cultivar. However, the pattern of accumulation of different ions in roots due to different seed priming treatments was not consistent in either cultivar except that root Na⁺ decreased due to priming with spermine and spermidine in the intolerant and tolerant cultivars under saline conditions. In conclusion, although all three priming agents, spermine, spermidine and putrescine, were effective in alleviating the adverse effect of salt stress on wheat plants, their effects on altering the concentration of different ions and growth were different in the two cultivars differing in salt tolerance.     

SOS1 gene overexpression increased salt tolerance in transgenic tobacco by maintaining a higher K(+)/Na(+) ratio

Crop productivity is greatly affected by soil salinity, so improvement in salinity tolerance of crops is a major objective of many studies. We overexpressed the Arabidopsis thaliana SOS1 gene, which encodes a plasma membrane Na⁺/H⁺ antiporter, in tobacco (Nicotiana tabacum cv. Xanthi-nc). Compared with nontransgenic plants, seeds from transgenic tobacco had better germination under 120 mM (mmol L⁻¹) NaCl stress; chlorophyll loss in the transgenic seedlings treated with 360 mM NaCl was less; transgenic tobacco showed superior growth after irrigation with NaCl solutions; and transgenic seedlings with 150 mM NaCl stress accumulated less Na⁺ and more K⁺. In addition, roots of SOS1-overexpressing seedlings lost less K⁺ instantaneously in response to 50 mM NaCl than control plants. These results showed that the A. thaliana SOS1 gene potentially can improve the salt tolerance of other plant species.     

Growth and ion uptake in <Emphasis Type="Italic">Annona muricata</Emphasis> and <Emphasis Type="Italic">A. squamosa</Emphasis> subjected to salt stress

The effects of treatment with NaCl (3, 100 and 300 mM) for 1, 2, 3 and 7 d on plant growth and ion accumulation were analyzed in 2-week and 8-week-old Annona muricata and A. squamosa plants. Fresh mass and root growth inhibition were directly related to the increase in salinity, particularly for A. squamosa. Two-weeks old seedlings were sensitive to 100 and 300 mM NaCl particularly after 7 d, whereas 8-week-old plants were shown to be more resistant to NaCl even at 300 mM NaCl. Na⁺ and Cl^– mostly accumulated in young leaves. Our results suggest that A. squamosa is more sensitive than A. muricata to salt stress and that older seedlings of both species are more tolerant than younger seedlings.     

Triacontanol modulates photosynthesis and osmoprotectants in canola (Brassica napus L.) under saline stress

Abstract

An experiment was conducted to assess the effect of pre-sowing seed treatment with triacontanol (TRIA) in canola (Brassica napus L.) cultivar (RBN-3060) under saline stress. Canola seeds were soaked in three levels of TRIA (0, 0.5, and 1 mg L^?1) for 12 hours. Three levels of salt stress (0, 100, and 150 mM NaCl) in full strength Hoagland's nutrient solution were applied to 56-days-old plants. Salt stress caused a significant reduction in growth, gas exchange, photochemical quenching (qP), and shoot and root K⁺ contents, while increased leaf glycine betaine, free proline, and shoot Na⁺ contents. Pre-sowing seed treatment with TRIA increased shoot fresh weight, number of seeds per plant, photosynthetic rate, transpiration rate, ratio of chlorophyll a/b, qP, electron transport rate, shoot and root K⁺ contents, and free proline and glycine betaine contents of canola plants at various TRIA levels under nonsaline or saline conditions.     

Influence of exogenous application of glycinebetaine on antioxidative system and growth of salt-stressed soybean seedlings (Glycine max L.)

Glycinebetaine is one of the most competitive compounds which play an important role in salt stress in plants. In this study, the enhanced salt tolerance in soybean (Glycine max L.) by exogenous application of glycinebetaine was evaluated. To improve salt tolerance at the seedling stage, GB was applied in four different concentrations (0, 5, 25 and 50 mM) as a pre-sowing seed treatment. Salinity stress in the form of a final concentration of 150 mM sodium chloride (NaCl) over a 15 day period drastically affected the plants as indicated by increased proline, MDA and Na⁺ content of soybean plants. In contrast, supplementation with 50 mM GB improved growth of soybean plants under NaCl as evidenced by a decrease in proline, MDA and Na⁺ content of soybean plants. Further analysis showed that treatments with GB, resulted in increasing of CAT and SOD activity of soybean seedlings in salt stress. We propose that the role of GB in increasing tolerance to salinity stress in soybean may result from either its antioxidant capacity by direct scavenging of H₂O₂ or its role in activating CAT activity which is mandatory in scavenging H₂O₂.     

Counteraction of exogenous L-proline with NaCl in salt-sensitive cultivar of rice

The counteraction of exogenous L-proline at different concentrations with salinity (100 mM NaCl at sublethal concentration) were observed on germinating rice. Supplemented 30 mM L-proline was shown to be the most effective; at higher concentration it reduced seedling growth and K⁺/Na⁺ ratio. Thus 30 mM L-proline can alleviate the salinity stress in rice seedlings.     

Response of grape rootstocks to salinity: changes in root growth, polyamines and abscisic acid

Effects of salinity (0, 50, 100 and 250 mM NaCl) on growth, root:shoot dry mass ratio, osmotic potential (ψ_x), electrolyte leakage and contents of Na⁺ and K⁺, polyamines and abscisic acid (ABA) were studied in the grape rootstocks Dogridge, 1613, St. George and Salt Creek. In control rootstocks, the root length was highest in Dogridge and contents of K⁺ and ABA in Salt Creek. Salinity treatments increased root Na⁺ and decreased K⁺ content and St. George exhibited highest Na⁺ content and Na⁺:K⁺ ratio. The root:shoot dry mass ratio in all rootstocks increased upto 100 mM NaCl. With increasing NaCl concentration, putrescine, spermine and spermidine contents showed consistent increase and putrescine increase was highest in St. George and spermidine and spermine in the Dogridge and Salt Creek. Under salinity, the ABA content increased in all the rootstocks but more in Salt Creek and Dogridge than in St. George.     

Salt stress effects on growth,pigments, proteins and lipid peroxidation in <Emphasis Type="Italic">Salicornia persica</Emphasis> and <Emphasis Type="Italic">S. europaea</Emphasis>

The effects of NaCl stress on growth, water status, contents of protein, proline, malondialdehyde (MDA), various sugars and photosynthetic pigments were investigated in seedlings of Salicornia persica and S. europaea grown in vitro. Seeds were germinated under NaCl (0, 100, 200, 300, 400, 500 and 600 mM) on Murashige and Skoog medium for 45 d. The shoot growth of both species increased under low NaCl concentration (100 mM) and then decreased with increasing NaCl concentrations. In contrast to S. persica, root length in S. europaea reduced steadily with an increase in salinity. Proline content in S. persica was higher than in S. europaea at most NaCl concentrations. Proline, reducing saccharide, oligosaccharide and soluble saccharide contents increased under salinity in both species. In contrast, contents of proteins and polysaccharides reduced in both species under salt stress. MDA content remained close to control at moderate NaCl concentrations (100 and 200 mM) and increased at higher salinities. MDA content in S. europaea was significantly higher than S. persica at higher salinities. Salt treatments decreased K⁺ and P contents in seedlings of both species. Significant reduction in contents of chlorophylls and carotenoids due to NaCl stress was also observed in seedlings of both species. Some differences appeared between S. persica and S. europaea concerning proteins profile. On the basis of the data obtained, S. persica is more salt-tolerant than S. europaea.     

Assessment of salt tolerance of Nasturtium officinale R. Br. using physiological and biochemical parameters

Nasturtium officinale R. Br. seedlings were treated with a range of NaCl concentrations (0, 50, 100 and 150 mM) for 21 days after seedling emergence. Physiological analysis based on growth and mineral nutrition, showed a substantial decrease in leaf dry matter with 150 mM NaCl treatment. The growth decrease was correlated with nutritional imbalance and a reduction in potassium accumulation and transport to the leaves. At the same time, we noted an increase in leaf sodium and chloride accumulation and transport. Salt tolerance of N. officinale under 100 mM NaCl was associated with osmotic adjustment via Na⁺ and Cl^? and the maintenance of high K⁺/Na⁺ selectivity. Salt decreased carotenoid content more than chlorophylls and also disturbed membrane integrity by increasing malondialdehyde content and electrolyte leakage. At 150 mM NaCl, an increase in antioxidant enzyme-specific activities for superoxide dismutase, catalase and guaiacol peroxidase occurred in concert with a decrease in ascorbic acid, polyphenol, tannin and flavonoid content. These results indicate that N. officinale can maintain growth and natural antioxidant defense compounds such as, vitamin C, carotenoids, and polyphenols, when cultivated in 100 mM NaCl, but not at higher salt levels.     

Priming-induced changes in germination,morpho-physiological and leaf biochemical responses of fenugreek (Trigonella foenum-graecum) under salt stress

Abstract

Seed priming is a simple biotechnological tool which is potentially able to promote seed germination and invigoration as well as seedlings establishment and stress tolerance. In this study, the effects of seed pre-treatment with water (hydro-priming), 100 (HP-NaCl₁₀₀) and 200?mM (HP-NaCl₂₀₀) NaCl (halo-priming) for 6?h on some physiological and biochemical parameters of fenugreek was investigated under saline conditions (100?mM NaCl). For the three priming treatments, no significant changes in the final germination percentage were observed. However, a decrease in seed germination time was observed in hydro- and halo-primed (HP-NaCl₂₀₀) seeds. Salt stress (100?mM NaCl) reduced growth (shoot and root dry weight), pigment content, disturbed the ionic balance and enhanced malondialdehyde content. Salinity-induced changes in lipid metabolism towards synthesis/accumulation of saturated and monounsaturated fatty acids were observed in stressed plants. Seed priming ameliorated the negative effects of NaCl, ensuring significant amelioration on growth, pigment content, increased the activity of catalase and glutathione peroxidase and enhanced the synthesis of very long chain n-alkanes. Taken together, these data provide compelling evidence that priming is an effective alternative that can be used to promote germination and improves establishment and acclimation of fenugreek seedlings under saline conditions.     

Salinity tolerance of hydroponically grown <Emphasis Type="Italic">Pinus pinea</Emphasis> L. seedlings

The salinity tolerance and ion transport of 2-month-old seedlings of stone pine (Pinus pinea L.) grown in hydroponic solution containing various concentrations of NaCl (0–100 mM) were studied. The presence of salt of up to 100 mM did not significantly reduce growth. Seedling hydration was insensitive to salinity. High salt concentrations reduced K⁺ and Ca²⁺ uptake, root accumulation, and export to shoots. Na⁺ and Cl⁻ ions, representing the major part of the ionic uptake, were effectively compartmentalized in vacuoles. We concluded that seedlings of stone pine cultivated hydroponically were highly tolerant to salt concentrations of up to 100 mM for a culture period of 38 days. This tolerance was associated with the accumulation of Na⁺ and Cl⁻ ions in the shoots.     

Counteraction of Salinity Stress on Wheat Plants by Grain Soaking in Ascorbic Acid, Thiamin or Sodium Salicylate

The interactive effects of salinity stress (40, 80, 120 and 160 mM NaCl) and ascorbic acid (0.6 mM), thiamin (0.3 mM) or sodium salicylate (0.6 mM) were studied in wheat (Triticum aestivum L.). The contents of cellulose, lignin of either shoots or roots, pectin of root and soluble sugars of shoots were lowered with the rise of NaCl concentration. On the other hand, the contents of hemicellulose and soluble sugars of roots, starch and soluble proteins of shoots, proline of either shoots or roots, and amino acids of roots were raised. Also, increasing NaCl concentration in the culture media increased Na⁺ and Ca²⁺ accumulation and gradually lowered K⁺ and Mg²⁺ concentration in different organs of wheat plant. Grain soaking in ascorbic acid, thiamin or sodium salicylate could counteract the adverse effects of NaCl salinity on the seedlings of wheat plant by suppression of salt stress induced accumulation of proline.     

Contributions of arbuscular mycorrhizal fungi to growth,photosynthesis, root morphology and ionic balance of citrus seedlings under salt stress

A pot study was conducted to determine the effects of arbuscular mycorrhizal (AM) fungi (Glomus mosseae and Paraglomus occultum) and salt (NaCl) stress on growth, photosynthesis, root morphology and ionic balance of citrus (Citrus tangerine Hort. ex Tanaka) seedlings. Eighty-five-day-old seedlings were exposed to 100 mM NaCl for 60 days to induce salt stress. Mycorrhizal colonization of citrus seedlings was not affected by salinity when associated with P. occultum, but significantly decreased when with G. mosseae. Compared with the non-mycorrhizal controls, mycorrhizal seedlings generally had greater plant height, stem diameter, shoot, root and total plant biomass, photosynthetic rate, transpiration rate and stomatal conductance under the 0 and 100 mM NaCl stresses. Root length, root projected area and root surface area were also higher in the mycorrhizal than in the non-mycorrhizal seedlings, but higher root volume in seedlings with G. mosseae. Leaf Na⁺ concentrations were significantly decreased, but leaf K⁺ and Mg²⁺ concentrations and the K⁺/Na⁺ ratio were increased when seedlings with both G. mosseae and P. occultum. Under the salt stress, Na⁺ concentrations were increased but K⁺ concentrations decreased in the mycorrhizal seedlings. Under the salt stress, Ca²⁺ concentrations were increased in the seedlings with P. occultum or without AM fungi (AMF), but decreased with G. mosseae. Ratios of both Ca²⁺/Na⁺ and Mg²⁺/Na⁺ were also increased in seedlings with G. mosseae under the non-salinity stress, while only the Mg²⁺/Na⁺ ratio was increased in seedlings with P. occultum under the salt stress. Our results suggested that salt tolerance of citrus seedlings could be enhanced by associated AMF with better plant growth, root morphology, photosynthesis and ionic balance.     

Effect of arginine and urea on polyamines content and growth of bean under salinity stress

Prior to sowing, seeds of bean (Phaseolus vulgaris L.) were treated with 4 mM arginine or 0.1% urea, as nitrogen source. The seeds were then subjected to salinity stress. Arginine and urea treatments stimulated germination of both unstressed and salinity-stressed seeds. It was interesting to observe that the increased germination percentage in response to arginine and urea treatments was associated with increased content of polyamines, particularly putrescine (Put), spermidine (Spd) and spermine (Spm). Growth of the seedlings was also improved by application of arginine and urea, which was also associated with increased content of the polyamines Spd and Spm, while the Put content decreased. Total soluble sugars were much accumulated in response to arginine and urea treatments under salinity stress for cellular osmoregulation. The ratio of K⁺/Na⁺ increased in the leaves by application of arginine and urea, indicating a more alleviation to the adverse effects of salinity stress. Changes in proteinogenic amino acids were also investigated.     

Comparative evaluation of hydro-, chemo- , and hormonal-priming methods for imparting salt and PEG stress tolerance in Indian mustard (<Emphasis Type="Italic">Brassica</Emphasis><Emphasis Type="Italic">juncea</Emphasis> L.)

The present study was aimed to evaluate the effect of different seed priming methods to enhance the sodium chloride (NaCl) and polyethylene glycol-8000 (PEG-8000) stress tolerance in Indian mustard (Brassica juncea L.). Seeds subjected to different priming treatments such as water (hydro-priming), calcium chloride (CaCl₂) (chemo-priming), and abscisic acid (ABA) (hormonal-priming) showed increased rate of germination as compared to non-primed seeds. The primed and non-primed seeds were grown for 15 days and then the seedlings were independently subjected to iso-osmotic salt (150 mM NaCl) or PEG-8000 (20%) stress. The different biochemical responses were studied 10 days after treatment. Under NaCl and PEG stress, the dry weight and total chlorophyll content were higher in primed sets as compared to non-primed treatment which was also evident by the phenotype of the seedlings. In general, the higher activities of superoxide dismutase and glutathione reductase resulted in lower oxidative damage, in terms of malondialdehyde content, under NaCl and PEG stress in hydro-primed set as compared to non-primed, ABA-, and CaCl₂-primed treatments. Besides, the level of total phenolics and accumulation of osmolytes such as free proline, glycine betaine, and total soluble sugars was also lower in hydro-primed set as compared to other primed and non-primed treatments. The study thus suggests the use of hydro-priming as a simple and cost-effective strategy to alleviate the NaCl and PEG induced stress in B. juncea.     

Effects of foliar applications of nitric oxide and salicylic acid on salt-induced changes in photosynthesis and antioxidative metabolism of cotton seedlings

Nitric oxide (NO) is a plant signaling compound known to mitigate key physiological processes and salicylic acid (SA) is considered to be a signaling molecule that plays a key role in growth, development, and defense responses in plants under stress conditions. This work investigated the effects of sodium nitroprusside (SNP, a donor of NO) and SA on salt-tolerance of cotton (Gossypium hirsutum L.) seedlings by examining growth, photosynthetic performance, total osmoregulation substance content, antioxidative enzymes and H⁺-ATPase enzyme subjected to 100 mM NaCl. Addition of 100 mM NaCl inhibited the growth and photosynthetic parameters of cotton seedlings, and dramatically increased the electrolyte leakage, the plant contents of proline, lipid peroxidation (malondialdehyde), hydrogen peroxide (H₂O₂) and Na. Furthermore, antioxidant enzyme activities were restrained. Foliar applications of 0.1 mM SNP or/and 0.1 mM SA led to increase in the growth rate and photosynthesis, including photosystem II, net photosynthetic rate and transpiration rate, improvement of reactive oxygen species-scavenging enzymes activities and reduction of H₂O₂ accumulation in cotton seedlings induced by NaCl. In addition, membrane transport and function were facilitated by decreasing leaf electrolyte leakage, improving ion absorption and activating the osmotic-regulated substances metabolic. Further investigation also showed that SNP and SA alleviated the inhibition of H⁺-ATPase in plasma membrane induced by NaCl. The present study showed that foliar application of SNP and SA alone mitigated the adverse effect of salinity, while the combined application proved to be even more effective in alleviating the adverse effects of NaCl stress.     

Exogenous application of free polyamines enhance salt tolerance of pistachio (Pistacia vera L.) seedlings

The protective effects of free polyamines (PAs) against salinity stress were investigated for pistachio seedlings (Pistacia vera cv. Badami-Zarand) in a controlled greenhouse. Seedlings were treated with 25, 50, 100 and 150 mM of salts including NaCl, CaCl₂ and MgCl₂. Foliar treatments of putrescine, spermidine (Spd) and spermine (Spm) (0.1 and 1 mM) were applied during the salinity period. Results showed that growth characteristics of pistachio seedlings decreased under salinity stress and the application of PAs efficiently reduced the adverse effects of salt stress. PAs reduced the severe effects of salt stress in pistachio seedlings neither by increasing the activities of peroxidase and ascorbate peroxidase nor by increasing the proline content but by increasing the activities of superoxide dismutase and catalase and decreasing the hydrogen peroxide (H₂O₂) activity. PAs treated seedlings showed a lower Na⁺:K⁺ ratio and Cl^? in leaves suggesting the role of PAs in balancing the ion exchange and better Na⁺:K⁺ discrimination under salt stress condition. These results showed the promising potential use of PAs especially Spm and Spd for reducing the negative effects of salinity stress and improving the growth of pistachio seedlings.     

Effects of salt stress and exogenous Ca2+ on Na+ compartmentalization,ion pump activities of tonoplast and plasma membrane in Nitraria tangutorum Bobr. leaves

Nitraria tangutorum Bobr. is a typical halophyte with superior tolerance to salinity. However, little is known about its physiological adaptation mechanisms to the salt environment. In the present study, N. tangutorum seedlings were treated with different concentrations of NaCl (100, 200, 300 and 400 mmol L^?1) combined with five levels of Ca²⁺ (0, 5, 10, 15 and 20 mmol L^?1) to investigate the effects of salt stress and exogenous Ca²⁺ on Na⁺ compartmentalization and ion pump activities of tonoplast and plasma membrane (PM) in leaves. Na⁺ and Ca²⁺ treatments increased the fresh weight and dry weight of N. tangutorum seedlings. The absorption of Na⁺ in roots, stems and leaves was substantially increased with the increases of NaCl concentration, and Na⁺ was mainly accumulated in leaves. Exogenous Ca²⁺ reduced Na⁺ accumulation in roots but promoted Na⁺ accumulation in leaves. The absorption and transportation of Ca²⁺ in N. tangutorum seedlings were inhibited under NaCl treatments. Exogenous Ca²⁺ promoted Ca²⁺ accumulation in the plant. Na⁺ contents in apoplast and symplast of leaves were also significantly increased, and symplast was the main part of Na⁺ intracellular compartmentalization. The tonoplast H⁺-ATPase and H⁺-PPase activities were significantly promoted under salt stress (NaCl concentrations ≤300 mmol L^?1). PM H⁺-ATPase activities gradually increased under salt stress (NaCl concentrations ≤200 mmol L^?1) followed by decreases with NaCl concentration increasing. The tonoplast H⁺-ATPase, H⁺-PPase and PM H⁺-ATPase activities increased first with the increasing exogenous Ca²⁺ concentration, reached the maximums at 15 mmol L^?1 Ca²⁺, and then decreased. The tonoplast and PM Ca²⁺-ATPase activities showed increasing trends with the increases of NaCl and Ca²⁺ concentration. These results suggested that certain concentrations of exogenous Ca²⁺ effectively enhanced ion pump activities of tonoplast and PM as well as promoted the intracellular Na⁺ compartmentalization to improve the salt tolerance of N. tangutorum.