High Salinity Treatments Research Articles

Combined transcriptomics and metabolomics analysis reveals salinity stress specific signaling and tolerance responses in the seagrass Zostera japonica.

Multiple regulatory pathways of Zostera japonica to salt stress were identified through growth, physiological, transcriptomic and metabolomic analyses. Seagrasses are marine higher submerged plants that evolved from terrestrial monocotyledons and have fully adapted to the high saline seawater environment during the long evolutionary process. As one of the seagrasses growing in the intertidal zone, Zostera japonica not only has the ability to quickly adapt to short-term salt stress but can also survive at salinities ranging from the lower salinity of the Yellow River estuary to the higher salinity of the bay, making it a good natural model for studying the mechanism underlying the adaptation of plants to salt stress. In this work, we screened the growth, physiological, metabolomic, and transcriptomic changes of Z. japonica after a 5-day exposure to different salinities. We found that high salinity treatment impeded the growth of Z. japonica, hindered its photosynthesis, and elicited oxidative damage, while Z. japonica increased antioxidant enzyme activity. At the transcriptomic level, hypersaline stress greatly reduced the expression levels of photosynthesis-related genes while increasing the expression of genes associated with flavonoid biosynthesis. Meanwhile, the expression of candidate genes involved in ion transport and cell wall remodeling was dramatically changed under hypersaline stress. Moreover, transcription factors signaling pathways such as mitogen-activated protein kinase (MAPK) were also significantly influenced by salt stress. At the metabolomic level, Z. japonica displayed an accumulation of osmolytes and TCA mediators under hypersaline stress. In conclusion, our results revealed a complex regulatory mechanism in Z. japonica under salt stress, and the findings will provide important guidance for improving salt resistance in crops.

Fouling behavior of nanofiltration membrane during the refining treatment of morphlines-dominant reverse osmosis concentrate

Nanofiltration (NF) has been proven to be with great potential for the separation of morpholines with molecular weight less than 200 Da in refining reverse osmosis concentrate (ROC), but its application is significantly restricted by the membrane fouling, which can reduce the rejection and service time. To enable the long-term operation stability of nanofiltration, this work focuses on the fouling behavior of each substance in the hydrosaline organic solution on nanofiltration membrane, aiming to give insight into the fouling mechanism. To this end, in this work, the effects of salts (i.e NaCl and Na2SO4), organic substances (including N-(2-hydroxypropyl)morpholine(NMH) and 4-morpholineacetate(MHA)) and representative divalent ions (Ca2+ and Mg2+) on the performance and physicochemical properties of DK membrane were systematically investigated. The results show that both salts and organics can induce DK membrane swelling, leading to an increase of the mean effective pore size. After the filtration of Na2SO4–NaCl–H2O, the mean pore size increased by 0.002 nm, resulting in the decrease of the removal ratio of NMH and MHA for 3.82% and 13.10%, respectively. With static adsorption of NMH and MHA, the mean pore size of DK membrane increased by 0.005 and 0.003 nm. The swelling slowed the entrance of more organic molecules into membrane pores. Among them, MHA led to the terrible irreversible pore blocking. As the concentration of Ca2+ increased, gypsum scaling was formed on the membrane surface. During this process, NMH and MHA played different roles, i.e. NMH accelerated the CaSO4 crystallization while MHA inhibited. As a conclusion, the fouling behavior of substances in the high saline organic wastewater on DK membrane were systematically revealed with the fouling mechanisms proposed, which could provide an insightful guidance for membrane fouling control and cleaning in the treatment of high salinity and organic wastewater.

Research Progress on High Salinity and High COD Industrial Wastewater Treatment Technology

In the production process of chemical products such as ethylene and epichlorohydrin, a large amount of industrial wastewater is generated, which has high salt content (over 3.5%), high COD value (over 10000mg·L-1), and characteristics such as biological inhibition and toxicity. At present, it is difficult for sewage treatment plants to effectively treat this type of wastewater. Therefore, the treatment of this type of industrial wastewater has become one of the main obstacles to the green development of the chemical industry. This article reviews the research progress on the generation and treatment technology of high salinity and high COD industrial wastewater, including physicochemical, biological, and physicochemical biological coupling methods. The next steps in the treatment of such industrial wastewater are proposed.

Thriving under Salinity: Growth, Ecophysiology and Proteomic Insights into the Tolerance Mechanisms of Obligate Halophyte Suaeda fruticosa.

Studies on obligate halophytes combining eco-physiological techniques and proteomic analysis are crucial for understanding salinity tolerance mechanisms but are limited. We thus examined growth, water relations, ion homeostasis, photosynthesis, oxidative stress mitigation and proteomic responses of an obligate halophyte Suaeda fruticosa to increasing salinity under semi-hydroponic culture. Most biomass parameters increased under moderate (300 mmol L-1 of NaCl) salinity, while high (900 mmol L-1 of NaCl) salinity caused some reduction in biomass parameters. Under moderate salinity, plants showed effective osmotic adjustment with concomitant accumulation of Na+ in both roots and leaves. Accumulation of Na+ did not accompany nutrient deficiency, damage to photosynthetic machinery and oxidative damage in plants treated with 300 mmol L-1 of NaCl. Under high salinity, plants showed further decline in sap osmotic potential with higher Na+ accumulation that did not coincide with a decline in relative water content, Fv/Fm, and oxidative damage markers (H2O2 and MDA). There were 22, 54 and 7 proteins in optimal salinity and 29, 46 and 8 proteins in high salinity treatment that were up-regulated, down-regulated or exhibited no change, respectively, as compared to control plants. These data indicate that biomass reduction in S. fruticosa at high salinity might result primarily from increased energetic cost rather than ionic toxicity.

Photosynthetic carbon allocation in native and invasive salt marshes undergoing hydrological change

Biogeochemical processes mediated by plants and soil in coastal marshes are vulnerable to environmental changes and biological invasion. In particular, tidal inundation and salinity stress will intensify under future rising sea level scenarios. In this study, the interactive effects of flooding regimes (non-waterlogging vs. waterlogging) and salinity (0, 5, 15, and 30 parts per thousand (ppt)) on photosynthetic carbon allocation in plant, rhizodeposition, and microbial communities in native (Phragmites australis) and invasive (Spartina alterniflora) marshes were investigated using mesocosm experiments and 13CO2 pulse-labeling techniques. The results showed that waterlogging and elevated salinity treatments decreased specific root allocation (SRA) of 13C, rhizodeposition allocation (RA) 13C, soil 13C content, grouped microbial PLFAs, and the fungal 13C proportion relative to total PLFAs-13C. The lowest SRA, RA, and fungal 13C proportion occurred under the combined waterlogging and high (30 ppt) salinity treatments. Relative to S. alterniflora, P. australis displayed greater sensitivity to hydrological changes, with a greater reduction in rhizodeposition, soil 13C content, and fungal PLFAs. S. alterniflora showed an earlier peak SRA but a lower root/shoot 13C ratio than P. australis. This suggests that S. alterniflora may transfer more photosynthetic carbon to the shoot and rhizosphere to facilitate invasion under stress. Waterlogging and high salinity treatments shifted C allocation towards bacteria over fungi for both plant species, with a higher allocation shift in S. alterniflora soil, revealing the species-specific microbial response to hydrological stresses. Potential shifts towards less efficient bacterial pathways might result in accelerated carbon loss. Over the study period, salinity was the primary driver for both species, explaining 33.2–50.8 % of 13C allocation in the plant-soil-microbe system. We propose that future carbon dynamics in coastal salt marshes under sea-level rise conditions depend on species-specific adaptive strategies and carbon allocation patterns of native and invasive plant-soil systems.

Temporal Changes in Biochemical Responses to Salt Stress in Three Salicornia Species.

Halophytes adapt to salinity using different biochemical response mechanisms. Temporal measurements of biochemical parameters over a period of exposure to salinity may clarify the patterns and kinetics of stress responses in halophytes. This study aimed to evaluate short-term temporal changes in shoot biomass and several biochemical variables, including the contents of photosynthetic pigments, ions (Na+, K+, Ca2+, and Mg2+), osmolytes (proline and glycine betaine), oxidative stress markers (H2O2 and malondialdehyde), and antioxidant enzymes (superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase) activities of three halophytic Salicornia species (S. persica, S. europaea, and S. bigelovii) in response to non-saline, moderate (300 mM NaCl), and high (500 mM NaCl) salinity treatments at three sampling times. Salicornia plants showed maximum shoot biomass under moderate salinity conditions. The results indicated that high Na+ accumulation in the shoots, coupled with the relative retention of K+ and Ca2+ under salt stress conditions, contributed significantly to ionic and osmotic balance and salinity tolerance in the tested Salicornia species. Glycine betaine accumulation, both constitutive and salt-induced, also seems to play a crucial role in osmotic adjustment in Salicornia plants subjected to salinity treatments. Salicornia species possess an efficient antioxidant enzyme system that largely relies on the ascorbate peroxidase and peroxidase activities to partly counteract salt-induced oxidative stress. The results also revealed that S. persica exhibited higher salinity tolerance than S. europaea and S. bigelovii, as shown by better plant growth under moderate and high salinity. This higher tolerance was associated with higher peroxidase activities and increased glycine betaine and proline accumulation in S. persica. Taking all the data together, this study allowed the identification of the biochemical mechanisms contributing significantly to salinity tolerance of Salicornia through the maintenance of ion and osmotic homeostasis and protection against oxidative stress.

Fluid dynamics and energy efficiency of submerged combustion process for treating wastewater with high salinity and COD concentration

Focusing on submerged combustion technology for the treatment of high salinity and high chemical oxygen demand (COD) wastewater, this study explores the characteristics of gas-liquid two-phase flow and heat transfer during the submerged combustion process, employing both experimental and numerical simulation methods.Consequently, the impact of essential parameters on the efficacy of submerged combustion in treating wastewater was analyzed. The experimental results show that increasing the fuel flow rate and immersion depth is beneficial to improve the temperature rise rate and shorten the evaporation time. With the increase of the organic solution flow rate and the initial COD value of the organic solution, the COD removal rate decreased, and the effect of the organic solution flow rate on the COD removal efficiency was more obvious. The use of a flat orifice plate or tapered orifice plate immersed tube structure can improve the thermal efficiency by over 10%. However, it is not conducive to the stability of the pressure in the combustor, increasing the fluctuation of the liquid level. Compared with that of traditional single-effect evaporation crystallization, the energy consumption of the submerged combustion device is decreased, and the total operation cost is reduced by 22.5%.

A novel Populus euphratica DUB gene, PeMINDY3, enhances drought and salt tolerance by promoting ROS scavenging

Deubiquitinating enzymes (DUBs) are essential for plant responses to abiotic stress. However, the function of these genes in Populus euphratica, an ideal woody plant species for investigating abiotic stress response mechanisms, is largely unknown. In our previous study, a novel DUB gene, PeMINDY3, was revealed to contribute to the resistance of seeds to salinity stress. In the current study, PeMINDY3 was cloned and functionally characterized. A phylogenetic analysis indicated PeMINDY3 belongs to the MINDY subfamily of DUBs. Subcellular localization results showed that PeMINDY3 is located in chloroplasts. According to the qRT-PCR and GUS staining analyses, PeMINDY3 expression was induced in response to drought and high salinity treatment. The ectopic expression of PeMINDY3 in Arabidopsis thaliana increased the tolerance to drought and salt stress. Moreover, compared with the wild-type (WT) plants, A. thaliana plants ectopically expressing PeMINDY3 had longer primary roots and higher fresh weights, relative water contents, and antioxidant enzyme activities, but lower relative electrical conductivities. Additionally, stress-related genes were more highly expressed in the PeMINDY3 ectopically expressing plants than in the WT plants after the abiotic stress treatments. Furthermore, yeast one-hybrid and luciferase assays identified PeRAV2 as a regulator of PeMINDY3 expression. These findings suggest that PeMINDY3 positively modulates drought and salt stress tolerance, providing a foundation for further exploration of the function of DUB.

Fatty acid production and associated gene pathways are altered by increased salinity and dimethyl sulfoxide treatments during cryopreservation of Symbiodinium pilosum (Symbiodiniaceae)

The Symbiodinium genus is ancestral among other Symbiodiniaceae lineages with species that are both symbiotic and free living. Changes in marine ecosystems threaten their existence and crucial ecological roles. Cryopreservation offers an avenue for their long-term storage for future habitat restoration after coral bleaching. In our previous study we demonstrated that high salinity treatments of Symbiodiniaceae isolates led to changes in their fatty acid (FA) profiles and higher cell viabilities after cryopreservation. In this study, we investigated the role of increased salinity on FA production and the genes involved in FA biosynthesis and degradation pathways during the cryopreservation of Symbiodinium pilosum. Overall, there was a twofold increase in mass of FAs produced by S. pilosum after being cultured in medium with increased salinity (54 parts per thousand; ppt). Dimethyl sulfoxide (Me2SO) led to a ninefold increase of FAs in standard salinity (SS) treatment, compared to a fivefold increase in increased salinity (IS) treatments. The mass of the FA classes returned to baseline during recovery. Transcriptomic analyses showed an acyl carrier protein gene was significantly upregulated after Me2SO treatment in the SS cultures. Cytochrome P450 reductase genes were significantly down regulated after Me2SO addition in SS treatment preventing FA degradation. These changes in the expression of FA biosynthesis and degradation genes contributed to more FAs in SS treated isolates. Understanding how increased salinity changes FA production and the roles of specific genes in regulating FA pathways will help improve current freezing protocols for Symbiodiniaceae and other marine microalgae.

Optimizing cotton yield through appropriate irrigation water salinity: Coordinating above- and below-ground growth and enhancing photosynthetic capacity

The employment of brackish water for irrigation holds considerable potential for addressing the shortfall of freshwater resources in arid regions. It is crucial to discern the impact of salinity on agricultural output and its mechanisms when irrigating with brackish water. Here, a two-year field experiment (2021–2022) was undertaken in Xinjiang, China to assess the effects of water salinity (0.85 g L−1, CK; 3 g L−1, S1; 5 g L−1, S2; and 8 g L−1, S3) on the growth, photosynthesis, carbon accumulation, and cotton yield under mulched drip irrigation. Results showed that, compared to CK, the S1 treatment led to increased biomass, the boll capacity of the root system (BCR), and a reduced root-to-shoot ratio (R/S). In addition, the S1 treatment enhanced the net photosynthetic rate (Pn) and chlorophyll content (Chl) of cotton, enhancing the total carbon accumulation of boll (Cboll) and consequently, the seed cotton yield. However, the higher salinity treatments, S2 and S3, demonstrated a detrimental impact on these indicators. In comparison to CK, the S1 treatment showed a yield increase of 5.92% and 4.76% in the respective two years, yet the S2 and S3 treatments showed a yield decrease of 5.55–15.77% and 5.06–16.74%. The application of a structural equation model (SEM) elucidated a direct effect of photosynthetic parameters (Pn and Chl) and biomass characteristics (total biomass, R/S, and BCR) on yield. These factors also indirectly modulated seed cotton yield through the Cboll/Croot ratio. These results suggest that irrigation with brackish water of 3 g L−1 optimizes cotton production by coordinating crop growth of aboveground and underground parts. This study offers practical strategies for the cotton industry to enhance yields under brackish water irrigation.

Nonuniform salinity regulate leaf characteristics and improve photosynthesis of cherry tomatoes under high salinity

Cherry tomato (Lycopersicon esculentum var. cerasiforme) is a relatively salt-tolerant fruit and vegetable widely planted worldwide. In this study, the growth and physiological responses and the different regulatory of cherry tomatoes under high, low salinity, and partial root zone salinity conditions were investigated. Cherry tomatoes grown under nonuniform salinity (0/20, 0/100 mM NaCl) conditions in a split-root pot were compared with seedlings grown under uniform salinity (20, 100 mM NaCl) conditions, and their growth and physiological parameters were determined. Our results showed that the growth was not hindered under a low salinity (20 mM NaCl), and the fruit quality was improved without a yield reduction; this was caused by promoted root growth and better leaf function maintenance. The relief effects under the higher salt stress (100 mM NaCl) conditions were more significant than those under a lower salt stress condition (20 mM NaCl). Compared with uniform high salinity conditions, nonuniform salinity conditions could improve photosynthetic characteristics and maintain better leaf function. The apparent quantum efficiency (AQE), carboxylation efficiency (CE) and light saturation irradiance (LSP) increased, while the light compensation point (LCP) and CO2 compensation point (CCP) decreased; this enhanced the light energy and CO2 utilization. Chlorophyll content (Chl), including Chl a and b and the carotenoids (Car), and the chlorophyll fluorescence parameters, including the maximum quantum efficiency of photosystem II (PSII) reaction centers (Fv/Fm), the quantum efficiency of PSII (Y(II)) and electron transport rate through PSII (ETR), were increased; this significantly promoted the net photosynthetic rate (Pn) and water use efficiency (WUE). Compared with a uniform high salt stress treatment, the leaf relative water content (RWC) and water potential (Ψ) increased by 22.57% and 13.71%, respectively, the electrolyte leakage rate decreased by 36.13%, and the final yield increased by 2.89 times under a nonuniform high salinity treatment. These results indicated that nonuniform salinity conditions regulated the leaf water relations and the antioxidant system and maintained better anatomical structure to improve photosynthesis in cherry tomato under a high salinity environment. Finally, our results can aid in the improvement of tomato productivity from salt-affected lands.

Salinity alleviates arsenicstress-induced oxidative damage via antioxidative defense and metabolic adjustment in the root of the halophyte Salvadora persica.

Arsenic tolerance in the halophyte Salvadora persica is achieved by enhancing antioxidative defense and modulations of various groups of metabolites like amino acids, organic acids, sugars, sugar alcohols, and phytohormones. Salvadora persica is a facultative halophyte that thrives under high saline and arid regions of the world. In present study, we examine root metabolic responses of S. persica exposed to individual effects of high salinity (750mM NaCl), arsenic (600µM As), and combined treatment of salinity and arsenic (250mM NaCl + 600µM As) to decipher its As and salinity resistance mechanism. Our results demonstrated that NaCl supplementation reduced the levels of reactive oxygen species (ROS) under As stress. The increased activities of antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), and glutathione reductase (GR) maintained appropriate levels of ROS [superoxide (O2•-) and hydrogen peroxide (H2O2)] under salinity and/or As stress. The metabolites like sugars, amino acids, polyphenols, and organic acids exhibited higher accumulations when salt was supplied with As. Furthermore, comparatively higher accumulations of glycine, glutamate, and cystine under combined stress of salt and As may indicate its role in glutathione and phytochelatins (PCs) synthesis in root. The levels of phytohormones such as salicylate, jasmonate, abscisic acid, and auxins were significantly increased under high As with and without salinity stress. The amino acid metabolism, glutathione metabolism, carbohydrate metabolism, tricarboxylic acid cycle (TCA cycle), phenylpropanoid biosynthesis, and phenylalanine metabolism are the most significantly altered metabolic pathways in response to NaCl and/or As stress. Our study decoded the important metabolites and metabolic pathways involved in As and/or salinity tolerance in root of the halophyte S. persica providing clues for development of salinity and As resistance crops.

Unveiling the impact of flooding and salinity on iron oxides-mediated binding of organic carbon in the rhizosphere of Scirpus mariqueter

The abundant Fe (hydr-) oxides present in wetland sediments can form stable iron (Fe)-organic carbon (OC) complexes (Fe-OC), which are key mechanisms contributing to the stability of sedimentary OC stocks in coastal wetland ecosystems. However, the effects of increased flooding and salinity stress, resulting from global change, on the Fe-OC complexes in sediments remain unclear. In this study, we conducted controlled experiments in a climate chamber to quantify the impacts of flooding and salinity on the different forms of Fe (hydr-) oxides binding to OC in the rhizosphere sediments of S. mariqueter as well as the influence on Fe redox cycling bacteria in the rhizosphere. The results of this study demonstrated that prolonged flooding and high salinity treatments significantly reduced the content of organo-metal complexes (FePP) in the rhizosphere. Under high salinity conditions, the content of FePP-OC increased significantly, while flooding led to a decrease in FePP-OC content, inhibiting co-precipitation processes. The association of amorphous Fe (hydr-) oxides (FeHH) with OC showed no significant differences under different flooding and salinity treatments. Prolonged flooding significantly increased the relative abundance of Fe-reducing bacteria (FeRB) Deferrisoma and Geothermobacter and decreased polyphenol oxidase in the rhizosphere, while the relative abundance of Fe-oxidizing bacteria (FeOB) Paracoccus and Pseudomonas decreased with increasing salinity and duration of flooding. Overall, short-term water and salinity stress promoted the binding of FeDH to OC in the rhizosphere of S. mariqueter, leading to a reduction in the OC content held by FePP. However, there were no significant differences observed in the OC stocks or the total Fe-OC content in the rhizosphere sediments. The findings suggest a degree of consistency in the Fe-OC of the “plant-soil” complex system within tidal flat wetlands, showing resilience to abrupt shifts in flooding and salinity over short periods.

Salinity and cultivar effects on alfalfa forage yield and nutritive value in a Mediterranean climate

AbstractBackgroundSoil and water salinity are increasing problems worldwide, causing significantly reduced crop yields. Alfalfa (Medicago sativa L.) is often listed as salt‐sensitive, but field testing of improved cultivars is limited. Forage systems and improved high‐quality alfalfa varieties are needed to enable crop production under high salinity (HS) conditions.MethodsThe objective of this study was to measure the yield and quality response of alfalfa to high saline conditions in the field and to document the relative saline tolerance of its varieties. HS irrigation water (electrical conductivity of water, or ECw 8.0–11.0 dS m−1) was applied to 33 nondormant alfalfa cultivars and were compared with low salinity (LS) treatments (ECw 0.5–1.2 dS m−1) over 4 years in a Mediterranean environment on a clay loam soil utilizing a split‐plot design. Crops were harvested seven to eight times per year, and the forage quality was measured on selected harvests utilizing near‐infrared spectroscopy.ResultsThe average yield loss due to HS treatment was 23.9% compared with LS treatment, but yields averaged 23.4 Mg ha−1 under HS over the 3 full years of production. This level of production is considered to be economically viable in this region. Differences in salinity tolerance between lines were identified in the field; individual cultivars lost 5%–35% of their LS yield when grown under HS conditions. Forage quality was significantly improved under HS versus LS conditions, but improvements were negatively correlated with biomass yield (R2 > 0.81), similar to responses observed in drought‐stressed alfalfa.ConclusionsThese yield results confirm greenhouse studies, indicating that alfalfa is highly salt tolerant once established in the field, with potential for further improvement with tolerant cultivars. Salinity tolerance should be chosen based on total biomass yield as well as on the salinity tolerance index (HS yield relative to LS yield). Agronomic practices to mitigate salinity and sodicity are critical, along with improved cultivars.

The Impact of Salinity and Nutrient Regimes on the Agro-Morphological Traits and Water Use Efficiency of Tomato under Hydroponic Conditions

The effects of saline water on three greenhouse tomato cultivars (Feisty-Red, Ghandowra-F1, and Valouro-RZ) under three salinity concentrations (S1, ~2.5 dS m−1; S2, ~6.0 dS m−1; and ~9.0 dS m−1) and four nutrient regimes (N1–N4) were studied by evaluating the vegetative growth, chlorophyll content, leaf area, water use efficiency (WUE), and fruit yield of the cultivars. Vegetative growth parameters, such as plant height, leaf area, and stem diameter, were negatively correlated with increased levels of salinity. Also, the lowest WUE was noted for the high-salinity (~9.0 dS m−1) treatments. The Valouro-RZ cultivar performed better in terms of vegetative growth parameters when compared to both the Ghandowra-F1 and Feisty-Red cultivars. The plants grafted onto Maxifort rootstock showed more tolerance to salinity stress, with significant differences in plant growth, tomato yield, and WUE when compared with the non-grafted plants. The use of a modified nutrient solution (N2) in combination with moderately saline water (S2, ~6.0 dS m−1) resulted in a high mean yield (30.7 kg m−2), with a reduction of about ~1.6% compared with the mean yield of the control (i.e., the combination of S1 and N1), which was estimated to be about 31.2 kg m−2. High salinity significantly affected the mean WUE, which was the highest at 31.3 kg m−3 for the control plants (low salinity—S1), followed by the moderate-salinity (S2) plants at 30.4 kg m−3, and the lowest mean WUE was recorded for the high-salinity (S3) plants at 17.7 kg m−3. These results indicate that a combination of grafting onto rootstocks and using an appropriate nutrient recipe (i.e., N2 in this study) can mitigate the negative effects of salt stress on tomato plants grown under hydroponic conditions.

Electrically conductive membrane distillation via an alternating current operation for zero liquid discharge

Membrane distillation (MD) shows promise for achieving high salinity treatment and zero liquid discharge (ZLD) compared to conventional water treatment processes due to its unique characteristics, including low energy consumption and high resulting water quality. However, performance degradation due to fouling and scaling under high recovery conditions remains a challenge, particularly considering the need to control both cations and anions for maximum scaling mitigation. Accordingly, in this study, alternating current (AC) operation for electrically conductive membrane distillation (ECMD) is newly proposed, based on its potential for controlling both cations and anions, in contrast to conventional direct current (DC) operation. Systematic experiments and theoretical analysis show that water recovery in ECMD can be increased by 27% through AC operation. The proposed modification and effective AC operation of ECMD increase the practicality of using MD in desalination for a high recovery rate, perhaps even for ZLD.

Difference of high-salinity-induced inhibition of ammonia-oxidising bacteria and nitrite-oxidising bacteria and its applications

The difficulty in achieving stable partial nitritation (PN) is a challenge that limits the application of mainstream anaerobic ammonium oxidation (anammox). This study proposes high-salinity treatment as a novel strategy for inactivating nitrite-oxidising bacteria (NOB). The study indicated that NOB are more sensitive to high salinity than ammonia-oxidising bacteria (AOB). The inhibitory effect on the nitrifier gradually increased with increasing salinity from 0 to 100 g NaCl/L. After 24 h and 35 g NaCl/L inhibition, the AOB and NOB activities were 36.65% and 7.15% of their original activities, respectively. After one high-salinity treatment, nitrite accumulation rate (NAR) was above 33% during nitrification. Moreover, the sludge characteristics remained almost unchanged after suppression. A novel process for achieving mainstream PN was proposed and evaluated based on the results. An energy consumption analysis showed that mainstream PN/anammox based on the ex situ high-salinity treatment can achieve higher energy self-sufficiency compared with activated sludge.

Do various levels of salinity change chlorophyll fluorescence, nutrient uptake, and physiological characteristics of Mentha ecotypes?

Mint (Lamiaceae) is an economically important crop with many uses in the herbal, ornamental, culinary, pharmaceutical and food industries. To expand global cultivation, a better understanding of the growth and physiological responses of mint to soil salinity conditions is increasingly a strategic necessity. This study was aimed to investigate the NaCl (0, 2.5, 5, and 7.5 dS m−1) salinity stress effects on chlorophyll fluorescence, nutrient uptake, and physiological characteristics of different mint species [(18 ecotypes(E)] under the greenhouse environment. Based on the results obtained, the highest and the lowest soluble sugar contents (93.41 and 39.61 mg g−1 dry matter, respectively) were found in E15 at 7.5 dS m−1 salinity and in E6 under non-saline conditions that was raised by 57.5% upon 7.5 dS m−1 NaCl treatment over the control. The leaf relative water content was decreased in response to increasing salinity levels with the lowest values occurring at the highest salinity treatment by 42.2%, where ecotype 16 had the highest relative water content (53.2%) in the same salinity levels. Although, stomatal conductivity decreased as salinity intensity increased, the amount of this increase varied among ecotypes. At the highest level of salinity, E16 and E6 showed maximum and minimum stomatal conductivity, 7.23 and 4.13 mmol (H2O) m−2 s−1, respectively, which was a 42.8% difference between them. By increasing salinity levels, the nitrogen content of the plants was significantly decreased, which varied from 0.74 mg g−1 dry matter for ecotype 1–0.98 mg g−1 DW for ecotype 16. In term of 7.5 dS m−1 NaCl, the highest level of phosphorus (0.25 mg g−1 dry matter) was observed in ecotype 18. As salinity levels increased, the amount of potassium in shoot was decreased in a dose dependent manner in the mint ecotypes tested. At the highest salinity level, E8 and E15 had the highest, and E6 and E16 had the lowest level of potassium in shoot (1.34 mg g−1 dry matter and 1.24 mg g−1 dry matter, respectively). Overall, this research indicates that the mint E14, E10, and E18 are the most tolerant ecotypes displaying a high Fv/Fm index at all employed NaCl salinity levels. Thus, saline conditions may change the physiological processes and defense pathway resulting in dramatic changes in plant nutrients, photosynthesis efficiency and essential oil content of Mentha species.

Function of Soybean miR159 Family Members in Plant Responses to Low Phosphorus, High Salinity, and Abscisic Acid Treatment

MicroRNAs (miRNAs) regulate plant growth and development and plant responses to biotic and abiotic stresses. Although extensive studies show that miR159 family members regulate leaf and flower development in Arabidopsis thaliana, the roles of miRNAs in soybean (Glycine max) are poorly understood. Here, we identified six MIR159 genes in soybean, MIR159a–MIR159f, and investigate their expression patterns in plants under low-phosphorus (low-P), NaCl, or abscisic acid (ABA) treatments. In soybean leaves, MIR159e and MIR159f expression was induced by low-P treatment, while in roots, MIR159b, MIR159c, MIR159e, and MIR159f expression was upregulated. In flowers, low-P led to upregulation of MIR159a, MIR159b, MIR159c, and MIR159f but downregulation of MIR159d and MIR159e. In soybean nodules, MIR159b was upregulated but MIR159a, MIR159c, and MIR159d was downregulated under P deficiency. NaCl treatment induced MIR159a, MIR159b, MIR159c, and MIR159e expression in leaves and MIR159a–MIR159f expression in roots. ABA treatment upregulated MIR159a, MIR159b, and MIR159c but downregulated MIR159d, MIR159e, and MIR159f in leaves. These results suggest that miR159 family members function in plant abiotic stress responses. Moreover, total P content in leaves was significantly lower in plants overexpressing MIR159e than in the wild type, suggesting that miR159e may regulate P absorption and transport in soybean plants.

Effect of high salinity and of priming of non-germinated seeds by UV-C light on photosynthesis of lettuce plants grown in a controlled soilless system.

High salinity results in a decrease in plant photosynthesis and crop productivity. The aim of the present study was to evaluate the effect of UV-C priming treatments of lettuce seeds on photosynthesis of plants grown at high salinity. Non-primed and primed seeds were grown in an hydroponic system, with a standard nutrient solution, either supplemented with 100 mM NaCl (high salinity), or not (control). Considering that leaf and root K+ concentrations remained constant and that chlorophyll fluorescence parameters and root growth were not affected negatively in the high salinity treatment, we conclude that the latter was at the origin of a moderate stress only. A substantial decrease in leaf net photosynthetic assimilation (Anet) was however observed as a consequence of stomatal and non-stomatal limitations in the high salinity treatment. This decrease in Anet translated into a decrease in growth parameters; it may be attributed partially to the high salinity-associated increase in leaf concentration in abscisic acid and decrease in stomatal conductance. Priming by UV-C light resulted in an increase in total photosynthetic electron transport rate and Anet in the leaves of plants grown at high salinity. The increase of the latter translated into a moderate increase in growth parameters. It is hypothesized that the positive effect of UV-C priming on Anet and growth of the aerial part of lettuce plants grown at high salinity, is mainly due to its stimulating effect on leaf concentration in salicylic acid. Even though leaf cytokinins' concentration was higher in plants from primed seeds, maintenance of the cytokinins-to-abscisic acid ratio also supports the idea that UV-C priming resulted in protection of plants exposed to high salinity.