Low Salinity Levels Research Articles

Differential impacts of salinity on antibiotic resistance genes during cattle manure stockpiling are linked to mobility potentials revealed by metagenomic sequencing

Livestock manure is an important source of antibiotic resistance genes (ARGs), and its salinity level can change during stockpiling. To understand how the salinity changes affect the fate of ARGs, cattle manure was adjusted of salinity and stockpiled in laboratory microcosms at low (0.3% salt), moderate (3.0%) and high salinity levels (10.0%) for 44 days. Amongst the five ARGs (tetO, blaTEM, sul1, tetM, and ermB) and the first-class integrase (intI1) monitored by qPCR, the relative abundance of tetO and blaTEM exhibited no clear trend in response to salinity levels, while that of sul1, tetM, ermB and intI1 showed clear downward trends over time at the lower salinity levels (0.3% and 3%) but not at the high salinity level (10%). Metagenomic contig construction of cattle manure samples revealed that sul1, tetM and ermB genes were more likely to associate with mobile genetic elements (MGEs) than tetO and blaTEM, suggesting that their slower decay at higher salinity levels was either caused by horizontal gene transfer or co-selection of ARGs and osmotic stress resistant determinants. Further analysis of metagenomic contigs showed that osmotic stress resistance can also be located on MGEs or in conjunction with ARGs.

Chlorophyll fluorescence changes, as plant early state indicator under different water salinity regimes on the invasive macrophyte Elodea canadensis (Michx., 1803)

Analysis of the photosynthetic apparatus provides information on the physiological state of plants. The changes of metabolites in plant cells analysed with the pulsed chlorophyll fluorometer make it possible to determine these changes in plant cells even in the presence of insignificant cell damage. The possible effects of different salinity levels, 0.584, 1.461, 2.922 and 5.844 PSU (denoting Practical Salinity Unit) on the fluorescence properties of the pigment complexes of the aquatic invasive E. canadensis photosynthetic apparatus were investigated. Information about E. canadensis macrophyte photosynthetic systems (PSI and PSII) was obtained. After a prolonged impact, the results indicate that high salinity levels in substrates 2.922 and 5.844 PSU seriously affect plant photosynthetic apparatus inhibition. The decrease in ∆Fv/Fm΄ values at 2.922 and 5.844 PSU indicates general deterioration in macrophytes' physiological state. In the post-stress period, photosynthesis intensified. An interesting feature was noted: a low water salinity level (0.584) stimulates chlorophyll formation and increases the FvFm parameter. The research revealed the influence of salinity levels in the substrate on the photosynthesis processes in plants. The PSII system of submerged macrophytes responds rapidly to high salinity levels, probably due to the inhibition of protein synthesis. These data provide information for further bio-diagnosis of overall plant health and prediction of exposure levels, as well as the ability to make predictions of invasive plant growth and spread. The invasion of this plant macrophyte causes the most serious concern in Europe nowadays.

Castor bean cake increases osmoprotection and oil production in basil (Ocimum basilicum) under saline stress

Water salinity is a major abiotic stress that impacts plant growth and metabolism, reducing crop production. However, the adequate use of organic fertilizers rich in nitrogen (N) can attenuate the damages caused by saline stress. In this context, the castor bean cake (CBC), a co-product of the castor oil production chain, has shown great potential as organic fertilizer and stress mitigator, however, the mechanisms involved in these responses remain unclear. Thus, this study aimed to investigate the effects of different doses of CBC and electrical conductivities of irrigation water (EC) on the photochemical efficiency of photosystem II, the accumulation of organic solutes, and the oil production in basil. The experimental design was randomized blocks in a 5 × 5 factorial scheme, combining levels of EC (0.5, 1.2, 3.0, 4.7, 5.5 dS m−1) with doses of CBC (0.0, 1.4, 5.0, 8.5 and 10 t ha−1), in a matrix generated by the Box Central Compound. The contents of proline, glycine-betaine, proteins, amino acids, reducing sugars, non-reducing sugars, total sugars, photosynthetic pigments, electrolyte leakage, chlorophyll a fluorescence, and oil production were evaluated. The highest photochemical efficiency and oil content was found in basil irrigated with EC up to 3 dS m−1 and supplemented with 5 t ha−1 of CBC, which was followed by lower electrolyte leakage. In addition, CBC induced osmoregulation under saline conditions, as shown by the increase in free amino acids, proteins, proline, glycine-betaine, and sugars. However, high doses of CBC combined with high EC reduced photosynthetic pigment content, chlorophyll a fluorescence, and oil content. In conclusion, CBC induced osmoprotection, maintaining cell membrane integrity and increasing photochemical efficiency of basil. In addition, the use of 5 t ha−1 of CBC combined with low levels of water salinity can be employed to enhance oil production in basil.

Colloidal Stability of CA, SDS and PVA Coated Iron Oxide Nanoparticles (IONPs): Effect of Molar Ratio and Salinity.

Iron Oxide Nanoparticles (IONPs) have received unprecedented interest in various applications. The main challenges in IONPs are fluid stability due to agglomeration in a saline condition. This paper aims to investigate the colloidal stability of citric acid (CA), sodium dodecyl sulphate (SDS) and polyvinyl alcohol (PVA) under various molar ratios and levels of salinity. Firstly, the IONPs were synthesized using a facile co-precipitation approach. Secondly, the IONPs were coated using a simple dip-coating method by varying the molar ratio of CA, SDS and PVA. Next, the coated IONPs were characterized by using an X-ray Diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), and a Field Emission Scanning Electron Microscope (FESEM) for the morphological and crystallographic study of coated IONPs. Finally, the coated IONPs were characterized for their zeta potential value and hydrodynamic size using a Zetasizer and their turbidity was measured using a turbidity meter. It was found that at a low salinity level, 0.07 M of CA-IONPs, a high zeta potential value, a smaller hydrodynamic size, and a high turbidity value of -40.9 mV, 192 nm and 159 NTU were observed, respectively. At a high salinity level, 1.0 M SDS-IONPs recorded a high zeta potential value of 23.63 mV, which corresponds to a smaller hydrodynamic size (3955 nm) and high turbidity result (639 NTU). These findings are beneficial for delivering cutting-edge knowledge, especially in enhanced oil recovery (EOR) applications.

Mechanisms of Na+ uptake from freshwater habitats in animals.

Life in fresh water is osmotically and energetically challenging for living organisms, requiring increases in ion uptake from dilute environments. However, mechanisms of ion uptake from freshwater environments are still poorly understood and controversial, especially in arthropods, for which several hypothetical models have been proposed based on incomplete data. One compelling model involves the proton pump V-type H+ ATPase (VHA), which energizes the apical membrane, enabling the uptake of Na+ (and other cations) via an unknown Na+ transporter (referred to as the "Wieczorek Exchanger" in insects). What evidence exists for this model of ion uptake and what is this mystery exchanger or channel that cooperates with VHA? We present results from studies that explore this question in crustaceans, insects, and teleost fish. We argue that the Na+/H+ antiporter (NHA) is a likely candidate for the Wieczorek Exchanger in many crustaceans and insects; although, there is no evidence that this is the case for fish. NHA was discovered relatively recently in animals and its functions have not been well characterized. Teleost fish exhibit redundancy of Na+ uptake pathways at the gill level, performed by different ion transporter paralogs in diverse cell types, apparently enabling tolerance of low environmental salinity and various pH levels. We argue that much more research is needed on overall mechanisms of ion uptake from freshwater habitats, especially on NHA and other potential Wieczorek Exchangers. Such insights gained would contribute greatly to our general understanding of ionic regulation in diverse species across habitats.

Spatial Distribution Characteristics of Coal Mine Drainage Water Quality in China

Coal mine drainage (CMD) reuse is an important method for optimizing water resource supply in arid/semi-arid regions. This study analyzed the spatial distribution of water quality, management, and utilization strategies for CMD in China. In northwest, northeast, and north China, CMD was characterized by high levels of suspended solids, high salinity, neutral/weakly alkaline pH, and low levels of Fe/Mn. Based on existing water treatment processes, mine water reuse is safe and can support local water supply in these areas. In southern China, especially the southwestern regions, the CMD was characterized by low pH, high salinity, and high levels of Fe/Mn. These areas face high costs associated with mine water reuse and ecological and environmental risks. Therefore, the prevention and control of water pollution should be the focus of mine water management in these areas. To maximize the utilization of CMD, improving the norms and standards for mine water utilization is necessary, policy support for CMD reuse should be fortified, and a complete chain of coal mine water utilization should be developed. This study provides a reference for implementing water environmental protection strategies and mine water reuse policies.

The effects of hydrological connectivity blocking on Suaeda salsa development in the Yellow River Delta, China

Blocking of hydrological connectivity could greatly impact the sediment deposition process and change water and salinity conditions, which in turn affect plant germination, growth, and development in delta wetlands. A 2-year experiment, which included the effects of soil burial, water, and salinity on germination, growth, and production, was conducted to examine the function of hydrological connectivity blocking on the development of Suaeda salsa, a halophyte species. The results demonstrated that soil burial, water, and salinity all had significant effects on seed germination, plant growth, and production (p < 0.05). Seed germination decreased as soil buried depth increased (< 4 cm), and seeds did not germinate successfully when the buried depth was > 4 cm. Seed germination was the highest at 0 cm burial. However, moderate burial was beneficial for seedling emergence; therefore, the survival rate was the lowest when seeds were distributed at the surface (0 cm). Water and salinity both significantly affected the germination, growth, and productivity of S. salsa. Moderate salinity (10–20 g/kg) and fluctuating water (0–10 cm water depth) were suitable for seed germination and plant growth. Low salinity (< 10 g/kg), High salinity (>20 g/kg), drought, and high water levels (long-term flooding with water depth > 10 cm) were not conducive to the growth of S. salsa, and biomass and seed yield were also reduced. As a halophyte, salinity that is too low or too high is unsuitable for S. salsa population. Water and salinity also significantly affected S. salsa population (p < 0.05). In particular, water can offset the hazards of high salt concentrations. Blocking of hydrological connectivity can influence seed germination, yield, and vitality. In this case, S. salsa may have died out from the coastal wetland due to the lack of hydrological connectivity restoration.

Foliar-sprayed calcium-tryptophan mediated improvement in physio-biochemical attributes and nutritional profile of salt stressed Brassica oleracea var. italica

Chelated mineral supplements are a combination of minerals with amino acids (AAs), putatively more efficient as fertilizers, especially for enhancing nutrient absorption. This study aimed at investigating the efficacy of foliar-applied calcium (Ca) and its complex with tryptophan to improve the vegetative growth, biochemical attributes and nutritional value of salt stressed broccoli (Brassica oleracea L. var. italica) plants. Treatments comprised of 2 mM Ca [as CaCl2], tryptophan 1% [Trp] and Ca-chelated with tryptophan 1% [Ca-Trp] at four salinity stress levels, i.e., S1 [0 mM NaCl], S2 [50 mM NaCl], S3 [100 mM NaCl] and S4 [150 mM NaCl]. With increasing salinity, growth indices decreased, however a significant improvement was witnessed under Ca-Trp-treatment for S2 and S3 levels. Coherently, leaf nitrogen (N) concentration was higher than urea and nitrate (NO3), with S1 and S2 displaying comparatively higher N levels than S3 and S4. Both Ca-Trp and tryptophan alone slightly increased nitrate reductase (NR) activity under non-saline treatment, while an inversely proportional relation between NO3 and NR was found in S2 and S4. Chlorophyll index values, internal CO2 of stomata and photosynthesis enhanced under Ca-Trp with increasing salinity levels (from S2 to S3) when compared to control plants. As opposed to Ca-Trp, the highest abscisic acid contents were seen in S3xTrp followed by S4 × Ca. The stress indices increased with increasing salinity, especially under alone Ca and Trp-treatments; moreover, growth attributes thrived in the absence of salinity, particularly under Ca-Trp. Enrichment of glucobrassicin and progoitrin amino acids represented improved nutritional characteristics of broccoli, which increased in low salinity levels with Ca-Trp application. It is, therefore advisable to apply Ca-tryptophan chelate to broccoli plants under low (S2) and moderate (S3) salt stress for a burgeoning effect and enhanced nutritional value.

Deeper insight into the effect of salinity on the relationship of enzymatic activity, microbial community and key metabolic pathway during the anaerobic digestion of high strength organic wastewater

The threshold salt concentration to inhibit the anaerobic digestion (AD) has been intensively investigated, but its insight mechanism is not fully revealed. Therefore, this study systematically investigated the effect of salinity on acidogenesis and methanogenesis and its mechanism. Results showed that low salinity level (i.e. 0.6%) had stimulatory effect on volatile fatty acids (VFA) and methane production, while significant inhibition was observed with further increased salinity. Moreover, high salinity limited the butyric acid degradation at acidogenesis process. The decreases of enzymes (AK and PTA) activity and functional genes (ackA, pta and ACOX) expression that related to β-oxidation explained the butyric acid accumulation at high salinity levels. Microbial community analysis revealed high salinity levels significantly inhibited the proliferation of Syntrophomonas sp., which are known to be associated with butyric acid degradation. Similarly, the relative abundance of acetoclastic methanogen (Methanothrix sp.) and methylotrophic methanogen (Methanolinea sp.) significantly decreased at salinity condition.

Salinity impact on the metabolic and taxonomic profiles of acid and alkali treated inoculum for hydrogen production from food waste

This study evaluated the combined impact of salinity (2.5, 13, and 19.3 g NaCl/L) and inoculum pretreatment (acid/alkali) on the genomic and metabolic profiles of mesophilic fermentative bacteria for hydrogen (H2) production from food waste. Experimental results revealed that acid-treated inoculum showed the highest H2 yield (201.12 ± 13.84 mL H2/g of volatile solids added) under medium salinity levels compared to other experimental conditions. A 7–56% increase in H2 yield was observed for pretreated inoculum than untreated inoculum. Genomic analysis and metabolic pattern revealed that the H2 production was mainly through Clostridial-type fermentation under medium to high salinity levels, whereas Enterococcus-type fermentation under low salinity levels. Further, the genomic analysis uncovered that phyla Firmicutes (69.71–96.81%) and genus Clostridium sensu stricto 1 (33.28–94.04%) dominated during the exponential gas production phase. Overall, this study showed the significance of inoculum pretreatment for the bioconversion of food waste at different salinity levels.

Radium radioactivity in soil profiles following long term irrigation with high radioactivity fossil groundwater

High radioactivity in a relatively saline confined aquifer water in different locations of the Disi area (South East of Jordan) was reported by some authors who recommended further investigation on the impact of that water on irrigated soils. Five well water samples (jointly used for irrigation and drinking) and 28 surface and subsurface soil samples from five profiles were collected from that area for the purpose of this study. Selected mineralogical, chemical, and physical properties of the soil samples were determined. Mineralogical compositions of the 28 soil samples were identified using x-ray diffraction, x-ray fluorescence, and ICP-MS techniques. Determination of activity concentrations of 238U, 226Ra and 228Ra in the five well waters and 22 soil samples from 4 sites (including a native soil) were determined using γ-ray spectroscopy. The results showed low salinity levels of both soil and water samples and low clay and organic matter contents in all soil samples. Kaolinite and mica were the dominant clay minerals with Fe substituting Al in the octahedral layer of these minerals. The average activity concentration of 226Ra and 228Ra in the well-water samples were 0.31 ± 0.09 and 1.74 ± 0.12 BqL−1, respectively. Such a high specific activity could be ascribed to the water enrichment with 228Ra diffusing from 232Th-rich sandstone geologic strata. Average concentrations of 238U and 232Th in the soil samples (0–120 cm depth) were 1.48 ± 0.38 mg kg−1 and 4.78 ± 1.55 mg kg−1, respectively. High correlation between these two radionuclides (R2 = 0.90) indicated no specific enhancement of these two metals from external sources, especially through chemical precipitation from irrigation water. Average activity concentration of 238U, 226Ra, and 228Ra in the soil samples were substantially low (20.8 ± 5.6, 16.94 ± 4.48, and 20.7 ± 6.2 Bq kg−1, respectively). No particular changes were observed when comparing concentration or radioactivity of these radionuclides with depth of a given soil or between irrigated and native soil samples at comparable depths. This could lead to the conclusion that there was no appreciable precipitation or adsorption of these radioactive metals from the percolating irrigation water onto the sandy soil complex.

Bacterial Communities Along Environmental Gradients in Tropical Soda Lakes.

Soda lake environments are known to be variable and can have distinct differences according to geographical location. In this study, we investigated the effects of different environmental conditions of six adjacent soda lakes in the Pantanal biome (Mato Grosso do Sul state, Brazil) on bacterial communities and their functioning using a metagenomic approach combined with flow cytometry and chemical analyses. Ordination analysis using flow cytometry and water chemistry data from two sampling periods (wet and dry) clustered soda lakes into three different profiles: eutrophic turbid (ET), oligotrophic turbid (OT), and clear vegetated oligotrophic (CVO). Analysis of bacterial community composition and functioning corroborated this ordination; the exception was one ET lake, which was similar to one OT lake during the wet season, indicating drastic shifts between seasons. Microbial abundance and diversity increased during the dry period, along with a considerable number of limnological variables, all indicative of a strong effect of the precipitation-evaporation balance in these systems. Cyanobacteria were associated with high electric conductivity, pH, and nutrient availability, whereas Actinobacteria, Alphaproteobacteria, and Betaproteobacteria were correlated with landscape morphology variability (surface water, surface perimeter, and lake volume) and with lower salinity and pH levels. Stress response metabolism was enhanced in OT and ET lakes and underrepresented in CVO lakes. The microbiome dataset of this study can serve as a baseline for restoring impacted soda lakes. Altogether, the results of this study demonstrate the sensitivity of tropical soda lakes to climate change, as slight changes in hydrological regimes might produce drastic shifts in community diversity.

Role of composted organic material in reducing hazardous effect of salinity stress on biological nitrogen fixation and plant growth in salt affected soils of arid region

Application of organic matter (OM) has shown positive effects on growth and yield of crop grown under soil salinity stress. The present study was conducted to estimate effectiveness of OM in enhancing Biological Nitrogen Fixation (BNF) in soil and in return improving growth and yield of cowpea. Therefore, role of (OM) in alleviating impact of salinity stress on (BNF) in soils of arid region was evaluated in medium textured soils of different content of salts content. Experiment was conducted in pots under greenhouse conditions. Salinity range studied was 3.5, 8.2 and 12.4 dSm-1 in J1, J2, and J3 soil respectively. Compost as OM was added at 15, 25 and 50 g Kg-1 soil. Cowpea local variety was used as a test crop. Total nitrogen in soils without the addition of organic matter after harvesting was the least at the highest salinity level and the highest was in the soil of the least salinity level. Number of root nodules reduced by 27.0% and 49.0% when soil salinity increased to 8.2 and 12.4 dSm-1, respectively, compared to that in soil of 3.5 dSm-1. Total N in Cowpea plant linearly increase with the increase of level of (OM) addition. Rate of Increase in total N was the highest at the lowest salinity level soil and was the least at the highest salinity level soil. Weight of root nodules decreased by 45% when soil salinity increased by 42%. Addition of OM at a rate of 25 g OM Kg-1 soil to J1 soil of (3.5 dSm-1) and soil J3 of 12.4 dSm-1 weight of root nodules increased by 47.0%. and 21.7%, respectively. Dry weight of Cowpea plant grown in the three soils received different levels of OM decreased with the increase of soil salinity irrespective of level of OM addition. Addition of OM at a rate of 15, 25, and 50 g kg-1 soil of 3.5 dSm-1 seed yield increased by 65%,130%, and 136% respectively. These results had confirmed the role of OM in alleviating salinity stress on BNF process in soil.

Intraspecific Trait Variability of a Diatom and a Dinoflagellate Along a Salinity Gradient

The phytoplankton community is a highly diverse group of microscopic, photosynthetic organisms responsible for 50% of the global primary production. The predicted shift in ocean salinity due to climate change threatens phytoplankton, resulting in compositional shifts and changing biodiversity patterns. This study investigates intraspecific multi-trait variability and plasticity of Alexandrium ostenfeldii and Skeletonema marinoi along a salinity gradient. Multiple traits were measured for five strains of each species grown at six salinity levels (0, 5, 15, 20, 30, and 35 psu) and combined in the principal component analysis. Cell size contributed 52% to the total variation in traits composition and significantly differed between species. The trait plasticity of A. ostenfeldii was significantly higher than S. marinoi, and the highest trait plasticity was observed at 15 psu in both species. In addition to morphological traits, A. ostenfeldii was characterized by high plasticity of cellular carbon content and a higher C:P ratio at low salinity levels. Overall, the results suggest a high variation in traits plasticity between phytoplankton strains, emphasizing the importance of intraspecific diversity to maintain ecosystem functions under changing environmental conditions.

Effects of salinity on germination dynamics and seedling development in two amaranth genotypes.

Amaranth (Amaranthus caudatus L.), commonly known as "kiwicha", is a pseudo-cereal considered as the crop of future regarding its excellent nutritional value. It has also beensuggested as a robust alternative to traditional cereal crops in arid and semi-arid regions where abiotic stresses such as drought and salinity have increased due to climate change. In order to study the seedling behavior and germination dynamics of this species against salinity stress, two amaranth genotypes (Red and Green) were randomly chosen among others and our investigation focused on both morphological and physiological traits. Salt stress was applied for 10days. Our results show that Red genotype was more tolerant to salinity compared to Green since that the first gave a higher final germination rate and produced higher biomass. Moreover, the germination parameters are less affected in Red compared to those in Green genotype. The radicules of the first genotype accumulated more Na+ compared to those of the second one. Moreover, at low level of salinity (50mM NaCl), Red genotype showed significant increase in the volatile polyphenol compound content, as well as in the total antioxidant activity, compared to the control (0mM NaCl). Even if the inhibitory action of the methanoic extracts of both Red and Green genotypes was affected by the salinity, they showed an important activity against P. aeruginosa pathogen.

Biomass Production and Predicted Ethanol Yield Are Linked with Optimum Photosynthesis in Phragmites karka under Salinity and Drought Conditions.

Plant photosynthesis and biomass production are closely associated traits but critical to unfavorable environmental constraints such as salinity and drought. The relationships among stress tolerance, photosynthetic mechanisms, biomass and ethanol yield were assessed in Phragmites karka. The growth parameters, leaf gas exchange and chlorophyll fluorescence of P. karka were studied when irrigated with the control and 100 and 300 mM NaCl in a nutrient solution and water deficit conditions (drought, at 50% water holding capacity). The plant shoot fresh biomass was increased in the low NaCl concentration; however, it significantly declined in high salinity and drought. Interestingly the addition of low salinity increased the shoot biomass and ethanol yield. The number of tillers was increased at 100 mM NaCl in comparison to the control treatment. High salinity increased the photosynthetic performance, but there were no significant changes in drought-treated plants. The saturated irradiance (Is) for photosynthesis increased significantly in low salinity, but it declined (about 50%) in high salt-stressed and (about 20%) in drought-treated plants compared to the control. The rates of dark respiration (Rd) and compensation irradiance (Ic) were decreased significantly under all treatments of salinity and drought, with the exception of unchanged Rd values in the control and drought treatments. A-Ci curve analyses revealed a significant improvement in the Jmax, Vc, max, and triose-phosphate utilization (TPU) at lower salinity levels but decreased at 300 mM NaCl and drought treatments compared to the control. In the chlorophyll fluorescence parameters (Fv/Fm, maximum photochemical quantum yield of PSII, and Y(NO)), the non-photochemical yields were not affected under the salt and drought treatments, although an effective photochemical quantum yield (YII) and electron transport rate (ETR) were significantly enhanced in water deficit compared to control plants. P. karka regulates an efficient photosynthesis mechanism to grow in saline and arid areas and can therefore be used as a sustainable biofuel crop.

Effect of Foliar Application of Manganese on Plant Growth, Nodulation and Biochemical Attributes of Mungbean (Vigna radiata L.) under Salinity Stress

Background: Salinity is one of the considerable factors which wanes crop productivity especially in arid and semi-arid realms of the world. The stress created by high soil salinity can cause osmotic stress, specific ion toxicity, nutritional imbalance, hormonal dysfunction and oxidative damage. A study was carried out to determine the effect of manganese (Mn) on growth rate index (GRI), Nodulation status, total nitrogen content, total amino acid content and total protein content of mungbean plants under salinity. Methods: Three indices were used to evaluate the effect of salt stress on development of mungbean plants (100, 200 and 300 mM NaCl). Untreated plants served as control expect. Mn was supplied to the plants in form of manganese chloride (MnCl2). The plant samples were analyzed for 65 days at every 10-day interval. Result: The results revealed that low level of salinity (100 mM NaCl) showed a significant increment in all the above observed parameters, while higher concentrations (200 mM and 300 mM) decreased the mentioned attributes. Foliar spraying with Mn (0.15%) mitigated the deleterious impacts of salinity and enhanced growth, nodulation and biochemical parameters. Thus, foliar treatment with Mn can be used in increasing the tolerance capacity of the plant and to enhance the nitrogen fixing ability of the plant under salinity.

Effect of seawater salinity stress on Sporobolus pungens (Schreb.) Kunth, a halophytic grass of the mediterranean embryonic dunes

Sporobolus pungens (Schreb.) Kunth is a perennial rhizomatous grass which develops at several coastal habitats, being relevant in the embryonic dune communities. Considering its importance for dune ecosystem and its fragile situation in the face of changes in sea level derived from global warming, the present study aimed to evaluate S. pungens response to increased salinity. One-year-old plants were exposed to different seawater (SW) dilutions (None, 1/16SW, 1/8SW, 1/4SW, 1/2 W and Full-SW). Gas exchange measurements and oxidative stress biomarkers were determined after two months of treatment. Stress conditions were maintained until flowering finished in order to assess the potential effects on the reproductive effort. Strong delay and inhibition of flowering were observed at low salinity levels and full inhibition for further treatments. Gas exchange measurements showed little effect until 1/8SW and a decreased assimilation rate due to mainly stomatal limitations at 1/4SW. Further decreases at higher salinity levels were related to both stomatal and metabolic limitations. As salinity increased, there was a progressive increase in the activity of glutathione peroxidase and glutathione reductase, while catalase activity remained stable. Superoxide dismutase did not vary except for Full-SW, where the activity significantly decreased. The levels of malondialdehyde, a marker of lipid peroxidation, remained unchanged and only increased in Full-SW level. In addition, the concentration of osmolytes, proline and soluble sugars, increased progressively with increasing salinity. In conclusion, S. pungens showed strong tolerance to salinity, through physiological adjustments at low levels of salinity, and activating glutathione-dependent enzymes at the highest concentrations. Evidence of oxidative damage was only observed after Full-SW exposure, although no death rate was recorded.

Response of Fenugreek (Trigonella foenum-graecum L.) Genotypes for their Germination and early Seedling Parameters Grown Under Different Saline levels

Seedling establishment is a most critical stage that determined the crop production at later stages. An in vitro investigation was carried out at the Laboratory of the Department of Plant Breeding and Genetics, Sri Karan Narendra College of Agriculture, Jobner (Rajasthan) in Rabi season 2016-17 to study the response of fenugreek genotypes for their germination and early seedling parameters under five salt stress levels viz. 0.0 mM, 40 mM, 80 mM, 120 mM and 160 mM. Fifteen seeds of each genotype were sown in sterilized Petridish and seedling observations were recorded. Results revealed that the average value was found maximum in the control and minimum at higher salinity level for most of traits. Higher reduction was found at higher salinity levels for most of the characters viz., plumule length, radicle length, seedling length, plumule to radicle length ratio, plumule fresh weight, radicle fresh weight, plumule dry weight, radicle dry weight and seedling vigour index but germination percentage showed less reduction. The contrast between mean of various genotypes in control conditions (S0) versus Sm (mean of S1, S2, S3 and S4) for each character also showed that overall mean was highest in control as compared to the overall mean of salinity levels for all the traits. This investigation concluded that higher level of salinity (above 60 mM) adversely most affected to seed germination and other early seeding traits rather than (below 40 mM) lower salinity levels. Based upon the rank totals of genotype over different salinity levels S1, S2, S3 and S4 (Sm) and characters, the RMt-303 was found to be most desirable genotype followed by UM-385, RMt-143 and RMt-305. These lines would be used as a viable option under saline conditions and better exploit in hybridization programme.

Nutrient uptake, physiological responses and growth of tobacco (Nicotiana tabacum L.) in soil under composite salt stress

Higher soil salinity imposes osmotic stress and ion toxicity in plants, leading to substantial crop yield loss worldwide. Understanding of the quantitative and dynamic physiological responses to composite soil salinity (CSS) is limited and needs to be expanded. In this study, physiological, nutritional, and biomass yield parameters of tobacco ( Nicotiana tabacum L.) grown in soil with five levels of CSS, basal CSS level (untreated control, CK) and 3 (T 1 ), 6 (T 2 ), 9 (T 3 ), and 12 (T 4 ) times the basal CSS level, grown under greenhouse were determined and studied at 30-, 60-, and 90-d growth periods. Leaf dry biomass was significantly ( P < 0.05) increased by the low salinity levels applied (T 1 and T 2 ) at all three time points, whereas it progressively declined as the CSS level further increased. The leaf physiological and photosynthetic responses were more adversely affected by CSS at the early growth stage (day 30). A path-coefficient analysis demonstrated that leaf proline concentration had the largest direct effect (–0.66), and leaf Cu content had the most significant indirect effect (0.49) on leaf dry biomass of plants. The results suggest that lower CSS levels (T 1 and T 2 ) could stimulate tobacco growth (leaf biomass yield, in particular), and higher leaf proline and Cu levels at the early growth stage may potentially increase the ability of tobacco plants to withstand the adverse effects of salinity, which could be considered for future research and development of salinity management strategies.