Ionic NaCl Research Articles

Cytogenetic impact of sodium chloride stress on root cells of Vigna radiata L. seedlings

Abstract Objectives The high salinization stress to seedling is the substantial ecological problem in the ongoing era. It negatively influences the growth that retard mitotic division by enhancing aberrations in nuclear chromatin. In the light of these views, the current work was designed to investigate the response of Vigna seedlings root tip cells to the presence of NaCl ions. Materials and methods NM-92 and NM19-19 seeds were imbibed separately in distilled water for 24 h and allowed to grow into 0, 50, 150, 250, and 350 mM NaCl solution for 24 h. Excised root tips were stained, and slides were scored at 100× objective for the mitotic index (MI) and chromosomal aberrations. Results Our data demonstrated that as NaCl molarity increased, the MI was declined along with various chromatin abnormalities. The 150 mM of NaCl showed more lagging (69%) of chromosomes during anaphase in NM19-19. The highest stickiness at metaphase stage (68%) was found in 250 mM NaCl in variety NM19-19. However, both varieties were differed non-significantly for c-mitosis that was recorded 99% at 350 mM NaCl concentration. Conclusions The NaCl ions toxicity induced various cytological anomalies in seedling roots that adversely affect the growth of Vigna seedlings.

The behaviour of hyaluronan solutions in the presence of Hofmeister ions: A light scattering, viscometry and surface tension study

Dynamic light scattering (DLS), viscosity and surface tension (SFT) measurements were used to characterize influence of salts containing ions of Hofmeister series (Na2SO4, (NH4)2SO4, NaSCN, NH4SCN and NaCl) on the behaviour of hyaluronan in diluted solutions at a temperature range of 15–45 °C. The results of the study showed that chaotropic and kosmotropic ions notably influenced the folding and unfolding of hyaluronan coils due to interactions between a respective ion and hydrophilic or hydrophobic patches present in the backbone of the polymer chains. This was mainly proved by viscosity and light scattering measurements. The temperature dependence of the hydrodynamic diameter of the hyaluronan coil determined by DLS demonstrated that combinations of chaotropic and kosmotropic ions in one salt (NaCl, NaSCN and (HN4)2SO4) can stabilize the size of the coil in a wide range of temperatures. Tensiometry measurements indicated that certain types of ions present in the solution caused an unfolding of the hyaluronan coils, leading to a decrease of SFT.

Effects of sulfate and magnesium ion on the chloride transportation behavior and binding capacity of Portland cement mortar

The chloride diffusion induced reinforcement corrosion seriously threatens the durability of concrete construction in marine environments. This paper investigates the effects of sulfate and magnesium ion in simulated seawater on the chloride transportation behavior and binding capacity of Portland cement mortar with and without fly ash (FA) and ground blast furnace slag (BFS). Chloride ion transport profile, binding capacity and corrosion products of mortar specimens exposed to NaCl, NaCl + MgCl2, NaCl + Na2SO4 and NaCl + MgCl2 + Na2SO4 solutions at different penetration depths were conducted respectively. Results indicate that the samples exposed to NaCl + MgCl2 solutions show the highest chloride content at the outmost layer (0–5 mm). The presence of magnesium ion and combined sulfate and magnesium ion in chloride salt accelerates chloride ingress and increase apparent chloride diffusion coefficient, while reduces the content of calcium hydroxide thus results in a reduction of the chloride binding. However, the sulfate ion in NaCl + Na2SO4 solutions inhibits the chloride diffusion, enhances bound chloride and refined the pore size due to the formation of Friedel’s salt (Fs) with chloride ion. Furthermore, the addition of BFS significantly improves the resistance to chloride ingress into mortar specimens.

Combined wicking and drying of a NaCl solution in porous building materials

Salt weathering is a major cause of destruction of many valuable monuments. The salt damage of historical porous materials is mainly due to the crystallization of soluble salts due to drying. A special situation which occurs often in marine environments, the case where there is a permanent supply of sea water at one side of a material, whereas the other side is exposed to continuous drying in the open air. A well-known example is the historic city of Venice. Evaporation from the air exposed side provides a continuous moisture sink which is compensated by capillary suction, i.e., wicking of the sea water. As a result there will be a continuous flux of NaCl ions towards the surface. As soon as the concentration at the surface reaches the maximum solubility, crystallization will start which can give rise the damage. A simple analytic model was developed to describe this process. In order to verify this model non-destructive measurements were made of the moisture and ion transport during an experiment with limestone. In order to do so, we make use of a specially designed Nuclear Magnetic Resonance setup where we are able to measure quasi-simultaneously the 1H and 23Na content. Hence this method gives us the possibility for real-time monitoring of transport processes of the ions during experiments. It is seen that the concentration rise at the drying surface can be described by a simple analytic model.

Mechanical Characterization of Low Permeable Siltstone under Different Reservoir Saturation Conditions: An Experimental Study

Hydro-fracturing is a common production enhancement technique used in unconventional reservoirs. However, an effective fracturing process requires a precise understanding of a formation’s in-situ strength behavior, which is mainly dependent on the formation’s in-situ stresses and fluid saturation. The aim of this study is to identify the effect of brine saturation (concentration and degree of saturation (DOS)) on the mechanical properties of one of the common unconventional reservoir rock types, siltstone. Most common type of non-destructive test: acoustic emission (AE) was used in conjunction with the destructive tests to investigate the rock properties. Unconfined compressive strength (UCS) and splitting tensile strength (STS) experiments were carried out for 78 varyingly saturated specimens utilizing ARAMIS (non-contact and material independent measuring system) and acoustic emission systems to determine the fracture propagation. According to the experimental results, the increase in degree of pore fluid saturation (NaCl ionic solution) causes siltstone’s compressive and tensile strengths to be reduced through weakening and breakage of the existing bonding between clay minerals. However, increasing NaCl concentration in the pore fluid generally enhances the compressive strength of siltstone through associated NaCl crystallization effect and actually reduces the tensile strength of siltstone through the corrosive influence of the NaCl ions. Moreover, results show that AE capture and analysis is one of the most effective methods to understand crack propagation behavior in rocks including the crack initiation, crack propagation, and final failure. The findings of this study are important for the identification of fluid saturation dependent in-situ strength conditions for successful hydro-fracturing in low permeable reservoirs.

Effect of surface area of carbon nanotubes on membrane performance for effective water desalination

Carbon nanotubes (CNTs) have emerged as promising novel membrane materials for enhancing desalination performance. So far, the salt rejection mechanism of these materials has been through the narrow diameter of these nanotubes that exclude salt and allow the transfer of water. It is challenging to control the inner diameter of all the nanotubes and there is the problem of low permeation after several measurements due to the narrow channels that water molecules have to travel through. There is also the problem of fouling after a few measurements, because even if a low percentage of ions leak through some of the channels, they can easily get stuck there and eventually block the channels. Here, the rejection mechanism of various CNTs, grown on Si hole arrays, is based on the effective surface area of the nanotubes. The rejection of NaCl and MgSO4 ions and the permeability of water were measured across CNT structures grown on micro-fabricated Si hole arrays in a gravity-driven pressure setup. The electric conductivity of the feed and permeate solutions was measured and showed acceptable values for salt rejection and high values for water permeation. A comparison between the performance of bare Si surface and those decorated with CNTs shows the effectiveness of surface modification with CNTs in salt rejection.

Spontaneous Imbibition Test of Low Salinity Injection at Low Saline Waxy Crude Carbonate

Low salinity waterflooding (LSW) is categorized as one of emerging EOR technologies. It is done by injecting water with different salt composition and/or concentration. The research has been carried out for both sandstone and carbonate with the results looks promising. However, most of this research still concentrated in the north sea, middle east and North America region. This article discusses the applicability of low salinity waterflooding methodology in Indonesia. Spontaneous imbibition test is carried out to observe the recovery gain from a various combination of concentration and composition of the injected brine. The change of pH of the brine is also examined in order to confirm the pH effect mechanism. Three different concentration of brine (500 ppm, 5.000 ppm, and 10.000 ppm), three different brine composition (NaCl, CaCl2, and MgCl2) and high paraffinic crude oil are used as the fluid sample. It is found that the increased oil recovery is significant at a salinity of 10,000 ppm for MgCl2 and 5,000 ppm for NaCl ions. While the lowest recovery was shown by the test at a salinity of 500 ppm

Geochemical occurrence of arsenic, vanadium and fluoride in groundwater of Patagonia, Argentina: Sources and mobilization processes

Contamination of groundwater in different parts of the world is a result of natural and/or anthropogenic sources, leading to adverse effects on human health and the ecosystem. In Península Valdés, where groundwater is the only source of supply, high concentrations of As and F- were registered. Since it is a region without industrial activity, an analysis of possible natural sources of contamination is necessary. The aim of this study is to analyse the hydrological processes that determines the presence and mobilization of those elements through the analysis of the mineralogy of the aquifer sediments and the ionic water relationships. The productive aquifer, dominated by psamites, coquinas and siltstone is located between 29 and 42 m below ground surface. The hydrochemistry studied from 105 sampling points, shows that groundwater is dominated by Na-Cl ions and, in the fresh water sectors, the ionic type is Na-HCO3 to Na-Cl. In 17 of these samples, Zn, Cr, Mn, As, V, Sr, Fe, F ions were measured and As and F contents above the potability limit were recorded. These contents vary between 0.01 and 0.40 mg/L in As and between 0.31 and 4 in F- which are both associated with elevated V values. The optical petrographic microscope observations and the X-ray diffraction measurements show that the sediments are dominated by volcanic lithic fragments, volcanic glass shards and quartz, plagioclase, pyroxenes and magnetite clasts. The scanning electron microscopy, combined with the energy dispersive X-ray analysis, shows that the highest concentrations of As are associated with volcanic shards and iron oxides. The combined analysis of all these elements leads to conclude that the processes which explain the presence of those ions are a result of the interaction of groundwater with the components of the aquifer sediments. At alkaline pH, the high solubility of the amorphous silica of vitreous shards allows the release of As, V and F- ions towards the solution. Thus, adsorption-desorption processes can also control the presence of these ions in groundwater. Both As and V (in solution in the form of oxyanions) can be adsorbed by iron oxides, while F- anions have more affinity to be adsorbed by the carbonate facies, some of them re-precipitated as a result of the increase in pH. The identified hydrogeological processes provide information for the planning of water purification measures that tend to improve the water resources management in a large arid region of Patagonia.

A simulation study of water property changes using geometrical alteration in SPC/E**Project supported by the National Natural Science Foundation of China (Grant Nos. 11635003, 11025524, and 11161130520), the National Basic Research Program of China (Grant No. 2010CB832903), and the European Commission’s 7th Framework Programme (Fp7-PEOPLE-2010-IRSES) (Grant Agreement Project No. 269131).

We present a systematic investigation of the impact of changing the geometry structure of the SPC/E water model by performing a series of molecular dynamic simulations at 1 bar (1 bar = 105 Pa) and 298.15 K. The geometric modification includes altering the H–O–H angle range from 90° to 115° and modifying the O–H length range from 0.90 Å to 1.10 Å in the SPC/E model. The former is achieved by keeping the dipole moment constant by modifying the O–H length, while in the latter only the O–H length is changed. With the larger bond length and angle, we find that the liquid shows a strong quadrupole interaction and high tetrahedral structure order parameter, resulting in the enhancement of the network structure of the liquid. When the bond length or angle is reduced, the hydrogen bond lifetime and self-diffusion constant decrease due to the weakening of the intermolecular interaction. We find that modifying the water molecular bond length leading to the variation of the intermolecular interaction strength is more intensive than changing the bond angle. Through calculating the average reduced density gradient and thermal fluctuation index, it is found that the scope of vdW interaction with neighbouring water molecules is inversely proportional to the change of the bond length and angle. The effect is mainly due to a significant change of the hydrogen bond network. To study the effect of water models as a solvent whose geometry has been modified, the solutions of ions in different solvent environments are examined by introducing NaCl. During the dissolving process, NaCl ions are ideally dissolved in SPC/E water and bond with natural water more easily than with other solvent models.

Application of multi-method approach to assess groundwater–surface water interactions, for catchment management

Globally, the dependence of river systems to delayed discharge of subsurface water to augment flows during dry seasons is well documented. Discharge of fresh subsurface water can dilute concentrated river flow quality during reduced flow. Observed and reported results on the Berg River’s declining water quantity and quality are a concern to the regions socio-economic growth and environmental integrity. Understanding the role of subsurface water discharges on the quantity and quality of receiving surface water courses can improve their management during dry periods. A case study was designed and implemented in the upper Berg River catchment in the Western Cape Province of South Africa to assess the influence of groundwater–surface water interaction on water quantity and quality. This study aimed to quantify and characterize the quality of subsurface water available in the upper catchment to improve observed declining water quality downstream. Hydrograph separation provided estimates of water fluxes during 2012–2014 low and high flow periods, while hydrochemical analysis provided insights on impacts of major land use activity in this catchment on water resources. Hydrograph separation analysis indicated that the Berg River is 37.9% dependent on subsurface water discharges annually. Dominant Na–Cl-type water indicates the quality of water from the upper Berg River is largely affected by natural processes including short residence times of aquifer water, rock–water interactions and atmospheric deposition of NaCl ions. These results provide insights for suggesting management options to be implemented to protect subsurface water for continued dilution and water resources management in the lower catchments.

Halotolerance (ionic NaCl) and chaotolerance (ionic MgCl2) of the human pathogen Wallemia mellicola isolated, for the first time, from indoor air in Poland

We isolated the human pathogen <em>Wallemia mellicola</em> from the class Wallemiomycetes for the first time in Poland. The fungus was isolated from indoor dust in Cracow. The strain belonged to the genus <em>Wallemia</em>, as confirmed by molecular methods (i.e., ITS1-5.8S-ITS2 nrDNA sequencing). We compared the halotolerance and chaotolerance of <em>W. mellicola</em> to other those of halotolerant fungi (<em>Talaromyces diversus</em> and <em>Aureobasidium pullulans</em>) isolated from an anchialine cave. The <em>W. mellicola</em> strain tolerated up to 20% NaCl and up to 15% MgCl<sub>2</sub>. As the concentration of NaCl in the culture medium increased, the colony diameter of <em>W. mellicola</em> decreased slightly. Dose–response curves for the two reference fungi <em>T. diversus</em> and <em>A. pullulans</em> revealed much lower tolerance of these fungi to increasing concentrations of NaCl. Our results indicated that <em>W. mellicola</em> is an advanced kosmotrope that is distinctly adapted to saline environments.

Forward osmosis membranes modified with laminar MoS2 nanosheet to improve desalination performance and antifouling properties

Internal concentration polarization (ICP) and membrane fouling are factors limiting the performance of forward osmosis (FO) membranes. Aiming at alleviating these problems, this study demonstrated the fabrication of FO membrane incorporated with MoS2 by layer-by-layer assembly with the synergistic effects of surface hydrophilicity, porosity and fouling-release properties. The grafting of MoS2 on the membrane surface was confirmed through the SEM, EDS and AFM analysis. The results demonstrated that the MoS2-coated-FO membrane could achieve transmembrane water flux of 27.15 LMH which was 35.34% higher than that obtained from a commercial polyethersulfone (PES) FO membrane. The reverse flux of NaCl ions was 16.42 gMH for the MoS2-coated-FO, 35.91% less than blank FO membrane. Meanwhile, coating MoS2 nanosheets endowed the resultant composites with higher water flux and lower reverse solute diffusion. In addition, the results of dynamic operation in a cross-flow test cell demonstrated that MoS2-coated-FO membrane exhibited good antifouling and fouling-release properties. This study indicates that use of MoS2 nanosheet is an attractive and feasible approach for the development of a dual-functional FO membrane by simultaneously improving the antifouling performance and reducing the ICP issues.

Ion association in binary mixtures of water-CO2 in supercritical conditions through classical molecular dynamics simulations

The structural and thermodynamic properties of Na+ - Cl− ion-pair association in water-CO2 binary mixtures in supercritical conditions for infinitely dilute solutions are studied using constrained molecular dynamics simulations over a wide range of compositions. It is found that solvation structure varies dramatically with the solvent composition. Contact ion pairs (CIPs) are found to be more stable than all other configurations as seen from the potentials of mean force (PMFs). PMFs of the NaCl ion pair in pure CO2 look almost like the pair potential between the ion pair. Stabilities of CIPs increase with increase in the mole fraction of CO2. An increment in the average number of hydrogen bonds with an increase in the mole fraction of H2O in the bulk as well as in the solvation shell of the ions is observed. Ion-pair association in aqueous CO2 mixtures in supercritical conditions is found to be endothermic and driven by entropy. Preferential solvation analysis shows that both Na+ and Cl− ions are preferentially solvated by water and even a small percentage of water in the mixture prevents CO2 molecules from entering the first solvation shell of ions due to the strong hydrophilicity of the ions.

A preliminary assessment of the geochemical factors affecting groundwater and surface water quality around the rural communities in Al-Anbar, Western Desert of Iraq

This study aims to assess the suitability of surface water and groundwater resources for irrigation and potable use by the rural communities in the Western Desert of Iraq. Sampling was conducted during the wet season (Jan 2012). Duplicate water and sediment samples were collected from the Euphrates River, connate water springs and meteoric groundwater. Water samples were analyzed for a suite of physicochemical parameters and heavy metals (Fe, Cu, Pb, Co, Cd and Ni). The H2S content of water samples was also determined as were heavy metals levels in riverine sediments. The water in the Euphrates River is fresh (701 ppm) dominated by Ca–Na–Cl ions with elevated concentrations of PO4, Pb and Cd (2.0, 0.023 and 0.02 ppm, respectively) due to the effects of agricultural land uses in the region. Shallow groundwater in the region is fresh to brackish due to the water–aquifer interaction that resulted in heterogeneity groundwater dominated by Cl, Ca–Mg–Cl and Ca–HCO3. Connate water springs in the region are associated with deep circulation of groundwater. Springs are characterized by brackish to saline water type dominated by Na–Cl and typically have acidic pH values. They are not suitable for irrigation or potable use due to the high TDS (7182 ppm) and dissolved H2S gas contents (120–865 ppm). Low concentrations of H2S gas (4.0 ppm) were detected in the Euphrates River, while they were not detected in the meteoric groundwater. The meteoric waters from the Euphrates River and some groundwater wells are suitable for potable use, but all are suitable for irrigation with attention to the potential-Mg hazard.

Interactions between hsian-tsao gum and chitosan in aqueous solution

The interactions of 0.05 wt% chitosan (CS) in admixture with different amounts of hsian-tsao gum (HG) in aqueous solutions were studied under different pH and ionic strength by the analysis of state diagram, turbidity, particle size and distribution, zeta potential and microstructure. Results obtained suggested that interactions between CS and HG could form soluble/insoluble complexes mainly through electrostatic attractions which significantly affected by HG concentration, pH and ionic strength. Particularly, varying pH or increasing HG concentration affected the zeta potential of CS-HG mixtures, which further influenced the complexes formation and caused phase separation. Furthermore, the formation of soluble complexes occurred between individual CS and HG molecules at pH away form pKa of CS, near which insoluble complexes with bigger size formed between HG and aggregate CS, except the 0.005 wt% HG molecules interacted with aggregate CS to form soluble complexes with smaller size than CS alone at pH 6.5. Additionally, added NaCl ions changing the charge density of two biopolymers further affected their electrostatic interactions, which were enhanced at lower concentrations but suppressed at higher concentrations. Optical measurements indicated the CS-HG complexes formed at pH 6.5 presented a coarsening phenomenon with increase of HG concentration. This study provided information regarding the effects of HG concentration, pH and ionic strength on the formation of electrostatic complexes between CS and HG in aqueous solution, which could be an available reference for preparation of electrostatic complexes.

Electrochemical Response of Bound Electrolyte Ions at Oriented Hematite Surfaces: A Local Electrochemical Impedance Spectroscopy Study

The electrochemical response of millimeter-sized hematite (α-Fe2O3) electrode surfaces to bound ions of NaCl, NH4Cl, and NaHCO3 salts was monitored by alternating current scanning electrochemical m ...

Ion-induced modification of the sucrose network and its impact on melting of freeze-dried liposomes. DSC and molecular dynamics study

Disaccharides play an important role in survival of anhydrobiotic organisms during extreme environmental conditions. A key protection feature is their capability to form the hydrogen bond (HB) network in a similar fashion as the one made by water. Since various ions also affect the HB network in completely hydrated systems, it is of a great interest to understand how they impact preservation when incorporated in a disaccharide network. To address this, we employ a combination of experimental and modeling techniques to study behavior of multilamellar 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) liposomes freeze-dried with sucrose in presence of NaCl or NaH2PO4·H2O at various concentrations (0.01–1M). Differential scanning calorimetry (DSC) was employed in order to determine the cooperative unit size (CUS), the number of lipid molecules that constitute a domain of cooperative motion in the liposome, and the melting temperature (Tm). In the absence of salt CUS was estimated to be 122±12, whereas in the presence of NaCl CUS increases more (347±34 for c=1M) than for NaH2PO4·H2O (193±26 for 1M). When it comes to Tm, the situation is reversed; NaCl induces increase by about 1K, while NaH2PO4·H2O by about 10K. These findings clearly demonstrate how different interaction forces−hydrogen bonding, charge pairing, and van der Waals interactions between acyl chains−affect CUS and Tm. Their interplay and contribution of particular interaction was further analyzed with molecular dynamics (MD) simulations. This analysis demonstrated that the HB network of DMPC and sucrose is partially disrupted in the presence of NaCl ions, and even to a greater extent in the case of NaH2PO4·H2O ions. Notably, H2PO4− ions outcompete and replace the sucrose molecules at the DMPC surface, which in turn alters the nature of the DMPC-surrounding interactions, from a weaker HB-dominated to a stronger CP-dominated interaction network.

Simultaneous removal of malachite green and hexavalent chromium by Cunninghamella elegans biofilm in a semi-continuous system

The present study was conducted to evaluate the potential of the fungus Cunninghamella elegans for simultaneous decolourisation of a triphenylmethane dye malachite green (MG) and hexavalent chromium [Cr(VI)] in the same media. This fungus can degrade MG through its reduction into leucomalachite green and then demethylation followed by oxidative cleavage. Along with MG degradation, C. elegans biofilm could effectively and repeatedly remove Cr(VI) from the liquid cultures even in the presence of high concentrations (40 g L−1) of NaCl and various other metal ions. C. elegans biofilm was also found to adsorb different dyes (reactive black-5, acid orange 7, direct red 81 and brilliant blue G) concurrently with Cr(VI). Based on its potential for simultaneous removal of dyes and Cr(VI) as well as reusability, C. elegans biofilm is envisaged as an efficient bioresource to devise strategies for treatment of wastewaters loaded with multiple pollutants.

Submicrometer Emitter ESI Tips for Native Mass Spectrometry of Membrane Proteins in Ionic and Nonionic Detergents.

Native mass spectrometry (native-MS) of membrane proteins typically requires a detergent screening protocol, protein solubilization in the preferred detergent, followed by protein liberation from the micelle by collisional activation. Here, submicrometer nano-ESI emitter tips are used for native-MS of membrane proteins solubilized in both nonionic and ionic detergent solutions. With the submicrometer nano-ESI emitter tips, resolved charge-state distributions of membrane protein ions are obtained from a 150 mM NaCl, 25 mM Tris-HCl with 1.1% octyl glucoside solution. The relative abundances of NaCl and detergent cluster ions at high m /z are significantly reduced with the submicrometer emitters compared with larger nano-ESI emitters that are commonly used. This technique is beneficial for significantly decreasing the abundances (by two to three orders of magnitude compared with the larger tip size: 1.6 μm) of detergent cluster ions formed from aqueous ammonium acetate solutions containing detergents that can overlap with the membrane protein ion signal. Resolved charge-state distributions of membrane protein ions from aqueous ammonium acetate solutions containing ionic detergents were obtained with the submicrometer nano-ESI emitters; this is the first report of native-MS of membrane proteins solubilized by ionic detergents. Graphical Abstract.

EFFECT OF DIFFERENT CALCIUM CONCENTRATIONS IN SOIL ON SURVIVAL PERCENT AND UPTAKE OF Na+ AND Cl- IONS BY RICE PLANT

Salinity is a stress factor affecting the production of crop in many regions. Calcium can reduce Na+ transport to shoots in rice. Two greenhouse experiments were conducted in Faculty of Agriculture, Cairo University, Egypt, during 2015 growing season of rice to evaluate the effect of different calcium concentrations on survival percent along with uptake of Na+ and Cl- ions by two varieties of rice (Oryza sativa L.) differing in salt-tolerance. The first experiment was undertaken to study the effect of different calcium concentrations on survival percent of IR28 (salt-sensitive) and Nona Bokra (Salt-tolerant) seedlings which were transferred to salinized nutrient solution containing 0.5% NaCl and a variable calcium concentrations at 4, 40, 100 and 200 ppm; plants were grown up to 40 days. The second experiment investigated the effect of different calcium concentrations on growth, uptake and transport of Na+ and Cl- ions in the two rice varieties differing in salt-tolerance. The seedlings were transferred to salinized nutrient solution containing 0.5% NaCl and calcium ion concentrations at two levels, 4 and 40 ppm. Plants were harvested at 0, 1, 3, 5 and 7 days from salinization. The results indicated that the salt-tolerant variety (Nona Bokra) survived for more than 40 days under exposure to 0.5% NaCl when calcium concentration of the culture solution ranged from 40 to 200 ppm Ca++. The low calcium ion concentration (4 ppm) depressed the growth of plants at 5 and 7 days after salinization. In Nona Bokra, the shoot had less sodium and Cl than the root. This implies that the salt tolerance of Nona Bokra may be attributed to the restricted translocation of Na+ and Cl- from the root to the shoot. Sodium as well as cloride content in the shoot of IR28 was more than twice that of Nona Bokra. An adequate amount of Ca+2 tended to lower the salt injury caused by high levels of salinity in rice plants. The effect of calcium ion on salt tolerance varied greatly between Nona Bokra and IR28 varieties.