Comparing lactate and glycerol as a single-electron donor for sulfate reduction in fluidized bed reactors

Among the greatest challenges to the full implementation of biological sulfate reduction are the cost and availability of the electron source. With the development of the biofuel industry, new organic substrates have become available. Therefore, this work sought to compare the performance of a sulfidogenic process utilizing either lactate or glycerol as the substrate for sulfate-reducing bacteria (SRB) growth. Although sulfate reduction is energetically more favorable with lactate, glycerol is a less expensive alternative because excess production is forecasted with the worldwide development of the biodiesel industry. Continuous experiments were performed in a fluidized bed (FB) reactor containing activated carbon as a carrier for a mixed bacterial population composed of sulfate-reducing and fermentative bacteria. During the lactate-fed phases, incomplete oxidation of lactate to acetate by SRB was the dominant metabolic pathway resulting in as much as 90 % sulfate reduction and high acetate concentrations (2.7 g L^?1). Conversely, in the glycerol-fed phases, glycerol degradation resulted from syntrophic cooperation between sulfate-reducing and fermentative bacteria that produce butyrate along with acetate (1.0 g L^?1) as oxidation products. To our knowledge, this is the first report of butyrate formation during sulfate reduction in a glycerol-fed continuous-flow reactor. Sulfate concentrations were reduced by about 90 % (from 2,000 to 100–300 mg L^?1) when glycerol was being fed to the reactor. Since the FB reactor was able to stand a change from lactate to glycerol, this reactor is recommended as the preferred option should glycerol be selected as a cost-effective alternative to lactate for continuous sulfate reduction.     

Butanol production from concentrated lactose/whey permeate: Use of pervaporation membrane to recover and concentrate product

In these studies, butanol (acetone butanol ethanol or ABE) was produced from concentrated lactose/whey permeate containing 211 g L^?1 lactose. Fermentation of such a highly concentrated lactose solution was possible due to simultaneous product removal using a pervaporation membrane. In this system, a productivity of 0.43 g L^?1 h^?1 was obtained which is 307 % of that achieved in a non-product removal batch reactor (0.14 g L^?1 h^?1) where approximately 60 g L^?1 whey permeate lactose was fermented. The productivity obtained in this system is much higher than that achieved in other product removal systems (perstraction 0.21 g L^?1 h^?1 and gas stripping 0.32 g L^?1 h^?1). This membrane was also used to concentrate butanol from approximately 2.50 g L^?1 in the reactor to 755 g L^?1. Using this membrane, ABE selectivities and fluxes of 24.4–44.3 and 0.57–4.05 g m^?2 h^?1 were obtained, respectively. Pervaporation restricts removal of water from the reaction mixture thus requiring significantly less energy for product recovery when compared to gas stripping.     

A Review of: “North-Holland Publishing Company,Amsterdam, New York,Oxford, 1976; Softbound, 290 pages, $ 19.25.”

Several factors affecting erythritol production from glycerol by Yarrowia lipolytica Wratislavia K1 strain were examined in batch fermentations. Ammonium sulfate, monopotassium phosphate, and sodium chloride were identified as critical medium components that determine the ratio of polyols produced. The central composite rotatable experimental design was used to optimize medium composition for erythritol production. The concentrations of ammonium sulfate, monopotassium phosphate, and sodium chloride in the optimized medium were 2.25, 0.22, and 26.4 g L^?1, respectively. The C:N ratio was found as 81:1. In the optimized medium with 100 g L^?1 of glycerol the Wratislavia K1 strain produced 46.9 g L^?1 of erythritol, which corresponded to a 0.47 g g^?1 yield and a productivity of 0.85 g L^?1 hr^?1. In the fed-batch mode and medium with the total concentration of glycerol at 300 g L^?1 and C:N ratio at 81:1, 132 g L^?1 of erythritol was produced with 0.44 g g^?1 yield and a productivity of 1.01 g L^?1 hr^?1.     

Complete and simultaneous removal of ammonium and m-cresol in a nitrifying sequencing batch reactor

The kinetic behavior, oxidizing ability and tolerance to m-cresol of a nitrifying sludge exposed to different initial concentrations of m-cresol (0–150 mg C L^?1) were evaluated in a sequencing batch reactor fed with 50 mg NH₄ ⁺-N L^?1 and operated during 4 months. Complete removal of ammonium and m-cresol was achieved independently of the initial concentration of aromatic compound in all the assays. Up to 25 mg m-cresol-C L^?1 (C/N ratio of 0.5), the nitrifying yield (Y-NO₃ ^?) was 0.86 ± 0.05, indicating that the nitrate was the main product of the process; no biomass growth was detected. From 50 to 150 mg m-cresol-C L^?1 (1.0 ≤ C/N ≤ 3.0), simultaneous microbial growth and partial ammonium-to-nitrate conversion were obtained, reaching a maximum microbial total protein concentration of 0.763 g L^?1 (247 % of its initial value) and the lowest Y-NO₃ ^? 0.53 ± 0.01 at 150 mg m-cresol-C L^?1. m-Cresol induced a significant decrease in the values of both specific rates of ammonium and nitrite oxidation, being the ammonium oxidation pathway the mainly inhibited. The nitrifying sludge was able to completely oxidize up to 150 mg m-cresol-C L^?1 by SBR cycle, reaching a maximum specific removal rate of 6.45 g m-cresol g^?1 microbial protein-N h^?1. The number of SBR cycles allowed a metabolic adaptation of the nitrifying consortium since nitrification inhibition decreased and faster oxidation of m-cresol took place throughout the cycles.     

Desodification from calcareous saline sodic soil through phytoremediation with Phragmites australis (Cav.) Trin. ex Steud. and gypsum

The reclamation of saline sodic soils requires sodium removal and the phytoremediation is one of the proven low-cost, low-risk technologies for reclaiming such soils. However, the role of Phragmites australis in reclaiming saline sodic soils has not been evaluated extensively. The comparative reclaiming role of P. australis and gypsum was evaluated in a column experiment on a sandy clay saline sodic soil with EC_e 74.7 dS m^?1, sodium adsorption ratio (SAR) 63.2, Na⁺ 361 g kg^?1, and pH 8.46. The gypsum at 100% soil requirement, planting common reed (P. australis) alone, P. australis + gypsum at 50% soil gypsum requirements, and leaching (control without plant and gypsum) were four treatments applied. After 11 weeks of incubation, the results showed that all treatments including the control significantly reduced pH, EC, exchangeable Na⁺, and SAR from the initial values, the control being with least results. The gypsum and P. australis + gypsum were highly effective in salinity (EC_e) reduction, while sodicity (SAR) and Na⁺ reductions were significantly higher in P. australis + gypsum treatment. The reclamation efficiency in terms of Na⁺ (83.4%) and SAR (86.8%) reduction was the highest in P. australis + gypsum. It is concluded that phytoremediation is an effective tool to reclaim saline sodic soil.     

Characterization and application of bioflocculant prepared by Rhodococcus erythropolis using sludge and livestock wastewater as cheap culture media

A new bioflocculant was produced by culturing Rhodococcus erythropolis in a cheap medium. When culture pH was 7.0, inoculum size was 2 % (v/v), Na₂HPO₄ concentration was 0.5 g L^?1, and the ratio of sludge/livestock wastewater was 7:1 (v/v), a maximum flocculating rate of 87.6 % could be achieved. Among 13 different kinds of pretreatments for sludge, the optimal one was the thermal-alkaline pretreatment. Different from a bioflocculant produced in a standard medium, this bioflocculant was effective over a wide pH range from 2 to 12 with flocculating rates higher than 98 %. Approximately, 1.6 g L^?1 of crude bioflocculant could be harvested using cold ethanol for extraction. This bioflocculant showed color removal rates up to 80 % when applied to direct and disperse dye solutions, but only 23.0 % for reactive dye solutions. Infrared spectrum showed that the bioflocculant contained functional groups such as –OH, –NH₂, and –CONH₂. Components in the bioflocculant consisted of 91.2 % of polysaccharides, 7.6 % of proteins, and 1.2 % of DNA. When the bioflocculant and copper sulfate (CuSO₄) were used together for decolorization in actual dye wastewater, the optimum decolorization conditions were specified by the response surface methodology as pH 11, bioflocculant dosage of 40 mg/L, and CuSO₄ 80 mg/L, under which a decolorization rate of 93.9 % could be reached.     

Treatment of old landfill leachate with high ammonium content using aerobic granular sludge

Background

Aerobic granular sludge has become an attractive alternative to the conventional activated sludge due to its high settling velocity, compact structure, and higher tolerance to toxic substances and adverse conditions. Aerobic granular sludge process has been studied intensively in the treatment of municipal and industrial wastewater. However, information on leachate treatment using aerobic granular sludge is very limited.

Methods

This study investigated the treatment performance of old landfill leachate with different levels of ammonium using two aerobic sequencing batch reactors (SBR): an activated sludge SBR (ASBR) and a granular sludge SBR (GSBR). Aerobic granules were successfully developed using old leachate with low ammonium concentration (136 mg L^?1 NH₄ ⁺-N).

Results

The GSBR obtained a stable chemical oxygen demand (COD) removal of 70% after 15 days of operation; while the ASBR required a start-up of at least 30 days and obtained unstable COD removal varying from 38 to 70%. Ammonium concentration was gradually increased in both reactors. Increasing influent ammonium concentration to 225 mg L^?1 N, the GSBR removed 73 ± 8% of COD; while COD removal of the ASBR was 59 ± 9%. The GSBR was also more efficient than the ASBR for nitrogen removal. The granular sludge could adapt to the increasing concentrations of ammonium, achieving 95 ± 7% removal efficiency at a maximum influent concentration of 465 mg L^?1 N. Ammonium removal of 96 ± 5% was obtained by the ASBR when it was fed with a maximum of 217 mg L^?1 NH₄ ⁺-N. However, the ASBR was partially inhibited by free-ammonia and nitrite accumulation rate increased up to 85%. Free-nitrous acid and the low biodegradability of organic carbon were likely the main factors affecting phosphorus removal.

Conclusion

The results from this research suggested that aerobic granular sludge have advantage over activated sludge in leachate treatment.

     

Effects of 5-aminolevulinic acid on Swiss chard (Beta vulgaris L. subsp. cicla) seedling growth under saline conditions

Salinity is a widespread adverse environmental problem globally, and significantly limits crop production. In this study, the possibility of enhancing salinity stress tolerance of Swiss chard (Beta vulgaris L. var. cicla) by 5-aminolevulinic acid (ALA) foliar application was investigated. The Swiss chard plants were grown in hydroponic culture. Twelve-week-old uniform seedlings were treated by 0 and 40 mM saline regimes generated by the mixture of sodium chloride and sodium sulfate (molar ratio NaCl:Na₂SO₄ = 9:1), and were foliar-sprayed with 0 and 60 μM L^?1 ALA (every 3 days) for 6 days; then the plants were treated for another 7 days (every 3 day) with increased concentration of salinity and ALA, 80 mM and 120 μM L^?1. Salinity without ALA application significantly decreased plant growth [43 % in shoot dry weight (DW), 21 % in root DW, 24 % in relative growth rate (RGR), 43 % in leaf area (LA)], water uptake [20.8 % in relative water content (RWC), 47.9 % in osmotic potential (OP)], chlorophyll (Chl) a content (10 %), P_n (36 %), G_s (72 %) and T_r (59 %) compared with those in control plants; however, under saline conditions, ALA foliar application improved plant growth (49.7 % in shoot DW, 27 % in root DW, 42.3 % in RGR, 72.1 % in LA) and increased RWC (12 %), Chl a content (10 %) and photosynthetic parameters (27 % in P_n, 28 % in G_s, 14 % in T_r) compared with those in untreated plants. Salinity significantly increased Na⁺ content, resulting in the reduction of Mg²⁺ and K⁺ contents. ALA foliar application alleviated ionic toxicity through the reduction of Na⁺ content and Na⁺/K⁺ ratio. On the other hand, it increased total nitrogen and glycine betaine (GB) content. ALA foliar application slightly reduced malondialdehyde (MDA) content, indicating that ALA has the potential to alleviate oxidative stress in salinity-stressed Swiss chard.     

Salt accumulation and depletion in the root-zone of the halophyte Atriplex nummularia Lindl.: influence of salinity,leaf area and plant water use

Background and aims

Salt is known to accumulate in the root-zone of Na⁺ excluding glycophytes under saline conditions. We examined the effect of soil salinity on Na⁺ and Cl^? depletion or accumulation in the root-zone of the halophyte (Atriplex nummularia Lindl).

Methods

A pot experiment was conducted in soil to examine Na⁺ and Cl^? concentrations adjacent to roots at four initial NaCl treatments (20, 50, 200 or 400 mM NaCl in the soil solution). Plant water use was manipulated by leaving plants with all leaves intact, removing approximately 50 % of leaves, or removing all leaves. Daily evapotranspiration was replaced by watering undrained pots to weight with deionised water. After 35-38 days, samples were taken of the bulk soil and of soil loosely- and closely-adhering to the roots.

Results

In plants with leaves intact grown with 200 and 400 mM NaCl, average Na⁺ and Cl^? concentrations in the closely adhering soil were about twice the concentrations of the bulk soil. Ion accumulation increased with final leaf area and with cumulative transpiration over the duration of the trial. By contrast, in plants grown with the lowest salinity treatment (20 mM NaCl), Na⁺ and Cl^? concentrations decreased in the closely adhering soil with increasing leaf area and increasing cumulative water use.

Conclusions

Our data show that Na⁺ and Cl^? are depleted from the root-zone of A. nummularia at low salinity but accumulate in the root-zone at moderate to high salinity, and that the ions are drawn towards the plant in the transpiration stream.     

Nickel,manganese and copper removal by a mixed consortium of sulfate reducing bacteria at a high COD/sulfate ratio

The use of sulfate-reducing bacteria (SRB) in passive treatments of acidic effluents containing heavy metals has become an attractive alternative biotechnology. Treatment efficiency may be linked with the effluent conditions (pH and metal concentration) and also to the amount and nature of the organic substrate. Variations on organic substrate and sulfate ratios clearly interfere with the biological removal of this ion by mixed cultures of SRB. This study aimed to cultivate a mixed culture of SRB using different lactate concentrations at pH 7.0 in the presence of Ni, Mn and Cu. The highest sulfate removal efficiency obtained was 98 %, at a COD/sulfate ratio of 2.0. The organic acid analyses indicated an acetate accumulation as a consequence of lactate degradation. Different concentrations of metals were added to the system at neutral pH conditions. Cell proliferation and sulfate consumption in the presence of nickel (4, 20 and 50 mg l^?1), manganese (1.5, 10 and 25 mg l^?1) and copper (1.5, 10 and 25 mg l^?1) were measured. The presence of metals interfered in the sulfate biological removal however the concentration of sulfide produced was high enough to remove over 90 % of the metals in the environment. The molecular characterization of the bacterial consortium based on dsrB gene sequencing indicated the presence of Desulfovibrio desulfuricans, Desulfomonas pigra and Desulfobulbus sp. The results here presented indicate that this SRB culture may be employed for mine effluent bioremediation due to its potential for removing sulfate and metals, simultaneously.     

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

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

Effects of stationary phase elongation and initial nitrogen and phosphorus concentrations on the growth and lipid-producing potential of Chlorella sp. HQ

Higher lipid production and nutrient removal rates are the pursuing goals for synchronous biodiesel production and wastewater treatment technology. An oleaginous alga Chlorella sp. HQ was tested in five different synthetic water, and it was found to achieve the maximum biomass (0.27 g L^?1) and lipid yield (41.3 mg L^?1) in the synthetic secondary effluent. Next, the effects of the stationary phase elongation and initial nitrogen (N) and phosphorus (P) concentrations were investigated. The results show that the algal characteristics were affected apparently under different N concentrations but not P, which were verified by Logistic and Monod models. At the early stationary phase, the algal biomass, lipid and triacylglycerols (TAGs) yields, and P removal efficiency increased and reached up to 0.19 g L^?1, 46.7 mg L^?1, 14.3 mg L^?1, and 94.3 %, respectively, but N removal efficiency decreased from 86.2 to 26.8 % under different N concentrations. And the largest TAGs yield was only 6.4 mg L^?1 and N removal efficiency was above 71.1 % under different P concentrations. At the late stationary phase, the maximal biomass, lipid and TAGs yields, and P removal efficiencies primarily increased as the initial N and P concentrations increase and climbed up to 0.49 g L^?1, 99.2 mg L^?1, 54.0 mg L^?1, and 100.0 %, respectively. It is concluded that stationary phase elongation is of great importance and the optimal initial N/P ratio should be controlled between 8/1 and 20/1 to serve Chlorella sp. HQ for better biodiesel production and secondary effluent purification.     

Effect of different media on exopolysaccharide and biomass production by the green microalga Botryococcus braunii

Botryococcus braunii is a colonial green microalga with recognized potential to synthesize lipids and hydrocarbons for biofuel production. Besides this ability, this microalga also produces exopolysaccharides (EPS). Nevertheless, there are few reports about their biotechnological aspects and industrial applications. In this study, the effect of the nutritional conditions was examined by using two different culture media (BG11 and D medium). To our knowledge, the latter has not been reported before for culturing B. braunii. After 49 days of incubation, the final production of EPS was found to be statistically higher (P < 0.05) in the D medium (0.549?±?0.044 g L^?1) than in BG11 (0.336?±?0.009 g L^?1). On the contrary, the biomass production was found to be higher in BG11 (1.019?±?0.051 g L^?1) than in the D medium (0.953?±?0.056 g L^?1). However, this difference was not statistically significant. The difference in salinity and nitrogen concentration between both media is suggested as the main factor involved in the EPS and biomass results. FTIR spectra of B. braunii EPS from both media revealed presence of uronic acids and absence of amino and sulfate groups. Despite the similarity between both spectra, there were some different signals (at 1,921.52 and 720.60 cm^?1) which may mean a difference in glycosyl composition.     

Biogeochemical regime shifts in coastal landscapes: the contrasting effects of saltwater incursion and agricultural pollution on greenhouse gas emissions from a freshwater wetland

Many coastal plain wetlands receive nutrient pollution from agricultural fields and are particularly vulnerable to saltwater incursion. Although wetlands are a major source of the greenhouse gases methane (CH₄) and nitrous oxide (N₂O), the consequences of salinization for greenhouse gas emissions from wetlands with high agricultural pollution loads is rarely considered. Here, we asked how saltwater exposure alters greenhouse gas emissions from a restored freshwater wetland that receives nutrient loading from upstream farms. During March to November 2012, we measured greenhouse gases along a ~2 km inundated portion of the wetland. Sampling locations spanned a wide chemical gradient from sites receiving seasonal fertilizer nitrogen and sulfate (SO₄ ^2?) loads to sites receiving seasonal increases in marine salts. Concentrations and fluxes of CH₄ were low (<100 µg L^?1 and <10 mg m^?2 h^?1) for all sites and sampling dates when SO₄ ^2? was high (>10 mg L^?1), regardless of whether the SO₄ ^2? source was agriculture or saltwater. Elevated CH₄ (as high as 1,500 µg L^?1 and 45 mg m^?2 h^?1) was only observed on dates when air temperatures were >27 °C and SO₄ ^2? was <10 mg L^?1. Despite elevated ammonium (NH₄ ⁺) for saltwater exposed sites, concentrations of N₂O remained low (<5 µg L^?1 and <10 µg m^?2 h^?1), except when fertilizer derived nitrate (NO₃ ^?) concentrations were high and N₂O increased as high as 156 µg L^?1. Our results suggest that although both saltwater and agriculture derived SO₄ ^2? may suppress CH₄, increases in N₂O associated with fertilizer derived NO₃ ^? may offset that reduction in wetlands exposed to both agricultural runoff and saltwater incursion.     

Phosphate solubilization by stress-tolerant soil fungus <Emphasis Type="Italic">Talaromyces funiculosus</Emphasis> SLS8 isolated from the Neem rhizosphere

A promising biotechnological strategy in the management of phosphorus (P) fertilization is the use of phosphate-solubilizing fungi to solubilize rock phosphates and allow the recovery of unavailable P fixed to soil particles. Phosphate-solubilizing rhizosphere fungus, Talaromyces funiculosus SLS8, isolated from Neem (Azadirachta indica) on saline soil, was tolerant to environmental stressors, salinity and agricultural systemic fungicides. Phosphate solubilization under different nutritional conditions was investigated by culturing T. funiculosus SLS8 in Pikovskaya liquid medium containing different nitrogen sources (ammonium sulfate, casein, urea, potassium nitrate or sodium nitrate) and carbon sources (glucose, fructose, galactose or sucrose), NaCl, and three systemic fungicides. The highest concentration of solubilised phosphate (187 mg P L^?1) was achieved after 5 days of incubation in the medium with glucose and ammonium sulphate. The culture pH decreased from 6.5 to 4.2 and HPLC demonstrated organic acid production. Phosphate solubilized was highly negatively correlated with pH (r?=??0.96). Increasing salinity had no effect on phosphate solubilization. The maximum tolerance limits to systemic fungicides carbendazim, mancozeb, and hexaconazole were 12.5 μg mL^?1, 2,000 μg mL^?1 and 250 μl mL^?1 respectively. At these concentrations carbendazim, mancozeb and hexaconazole were found to decrease phosphate solubilization by 55 %, 37 %, and 30 %, respectively. Our results indicate that T. funiculosus SLS8 may be a potential candidate for the development of a biofertilizer for maintaining available phosphate levels in environmentally stressed soils such as saline agricultural soils impacted by systemic fungicide application or seed treatment.     

Seed priming with sorghum extracts and benzyl aminopurine improves the tolerance against salt stress in wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis> L.)

Salt stress impedes the productivity of wheat (Triticum aestivum L.) in many parts of the world. This study evaluated the potential role of benzyl aminopurine (BAP) and sorghum water extract (SWE) in improving the wheat performance under saline conditions. Seeds were primed with BAP (5 mg L^?1), SWE (5% v/v), BAP + SWE, and distilled water (hydropriming). Soil filled pots maintained at the soil salinity levels of 4 and 10 dS m^?1 were used for the sowing of primed and non-primed seeds. Salt stress suppressed the wheat growth; seed priming treatments significantly improved the wheat growth under optimal and suboptimal conditions. Total phenolics, total soluble sugars and proteins, α-amylase activity, chlorophyll contents, and tissue potassium ion (K⁺) contents were increased by seed priming under salt stress; while, tissue sodium ion (Na⁺) contents were decreased. Seed priming with SWE + BAP was the most effective in this regard. Under salt stress, the tissue Na⁺ contents were reduced by 5.78, 28.3, 32.2, 36.7% by hydropriming, seed priming with SWE, seed priming with BAP, and seed priming with SWE + BAP, respectively over the non-primed control. Effectiveness of seed priming techniques followed the order SWE + BAP > BAP > SWE > Hydropriming. In conclusion, seed priming with SWE + BAP may be opted to improve the tolerance against salt stress in wheat.     

Salt sensitivity in chickpea is determined by sodium toxicity

Main conclusion

Salt sensitivity in chickpea is determined by Na⁺ toxicity, whereas relatively high leaf tissue concentrations of Cl^? were tolerated, and the osmotic component of 60-mM NaCl was not detrimental.Chickpea (Cicer arietinum L.) is sensitive to salinity. This study dissected the responses of chickpea to osmotic and ionic components (Na⁺ and/or Cl^?) of salt stress. Two genotypes with contrasting salt tolerances were exposed to osmotic treatments (?0.16 and ?0.29 MPa), Na⁺-salts, Cl^?-salts, or NaCl at 0, 30, or 60 mM for 42 days and growth, tissue ion concentrations and leaf gas-exchange were assessed. The osmotic treatments and Cl^?-salts did not affect growth, whereas Na⁺-salts and NaCl treatments equally impaired growth in either genotype. Shoot Na⁺ and Cl^? concentrations had markedly increased, whereas shoot K⁺ had declined in the NaCl treatments, but both genotypes had similar shoot concentrations of each of these individual ions after 14 and 28 days of treatments. Genesis836 achieved higher net photosynthetic rate (64–84 % of control) compared with Rupali (35–56 % of control) at equivalent leaf Na⁺ concentrations. We conclude that (1) salt sensitivity in chickpea is determined by Na⁺ toxicity, and (2) the two contrasting genotypes appear to differ in ‘tissue tolerance’ of high Na⁺. This study provides a basis for focus on Na⁺ tolerance traits for future varietal improvement programs for salinity tolerance in chickpea.

     

Salt dynamics in Tamarix ramosissima in the lower Virgin River floodplain, Nevada

Tamarisk (Tamarix spp.) is a halophyte with salt glands on its leaves and is an invasive riparian plant in the US. To increase our understanding of the effects of Tamarix on soil salinity, we conducted a year-long field investigation to evaluate the salt dynamics of a stand of Tamarix ramosissima along the lower Virgin River floodplain, NV, USA. We examined salt accumulation in the biomass and studied salt return to the soil by litter fall, throughfall and stemflow from September 2009 to September 2010. We also investigated soil salinity concentrations inside and outside of the stand where native shrub species was sparsely distributed. The average Na⁺ accumulated in the plant biomass was estimated at 23.4 g m^?2. The Na⁺ returned to the soil through litter fall, throughfall and stemflow during the investigation was similar with that accumulated in the plant biomass. More than 90 % of Na⁺ leached to the soil was from throughfall and stemflow. Soil salinity was significantly lower inside than outside of the stand. Salt secretion from Tamarix is generally expected to increase soil salinity in stands. However, our results suggest that surface soil salinity does not necessarily increase in the Tamarix stand along the lower Virgin River floodplain that is subjected to occasional flooding.     

Improvement of biomass and fatty acid productivity in ocean cultivation of <Emphasis Type="Italic">Tetraselmis</Emphasis> sp. using hypersaline medium

In this study, hypersaline media were used for ocean cultivation of the marine microalga Tetraselmis sp. KCTC12432BP for enhanced biomass and fatty acid (FA) productivity. Hypersaline media (55, 80, and 105 PSU) were prepared without sterilization by addition of NaCl to seawater obtained from Incheon, Korea. The highest biomass productivity was obtained at 55 PSU (0.16 g L^?1 day^?1) followed by 80 PSU (0.15 g L^?1 day^?1). Although the specific growth rate of Tetraselmis decreased at salinities higher than 55 PSU, prevention of contamination led to higher biomass productivity at 80 PSU than at 30 PSU (0.03 g L^?1 day^?1). FA content of algal biomass increased as salinity increased to 80 PSU, above which it declined, and FA productivity was highest at 80 PSU. Ocean cultivation of Tetraselmis was performed using 50-L tubular module photobioreactors and 2.5-kL square basic ponds, closed- and open-type ocean culture systems, respectively. Culturing microalgae in hypersaline medium (80 PSU) improved biomass productivities by 89 and 152% in closed and open cultures, respectively, compared with cultures with regular salinity. FA productivity was greatly improved by 369% in the closed cultures. The efficacy of salinity shift and N-deficiency to enhance FA productivity was also investigated. Lowering salinity to 30 PSU with N-starvation following cultivation at 80 PSU improved FA productivity by 19% in comparison with single-stage culture without N-deficiency at 30 PSU. The results show that salinity manipulation could be an effective strategy to improve biomass and FA productivity in ocean cultivation of Tetraselmis sp.