Biomass, lipid content, and fatty acid composition of freshwater Chlamydomonas mexicana and Scenedesmus obliquus grown under salt stress

Two freshwater microalgae including Chlamydomonas mexicana and Scenedesmus obliquus were grown on Bold Basal Medium (BBM) with different levels of salinity up to 100 mM NaCl. The dry biomass and lipid content of microalgae were improved as the concentration of NaCl increased from 0 to 25 mM. Highest dry weight (0.8 and 0.65 g/L) and lipid content (37 and 34 %) of C. mexicana and S. obliquus, respectively, were obtained in BBM amended with 25 mM NaCl. The fatty acid composition of the investigated species was also improved by the increased NaCl concentration. At 50 mM, NaCl palmitic acid (35 %) and linoleic acid (41 %) were the dominant fatty acids in C. mexicana, while oleic acid (41 %) and α-linolenic acid (20 %) were the major fractions found in S. obliquus.     

Effects of two sodium salts on fatty acid and essential oil composition of basil (Ocimum basilicum L.) leaves

The effects of two sodium salts on growth, fatty acids, and essential oil compositions were investigated in a medicinal and aromatic plant, Ocimum basilicum cultivated in hydroponic medium. Plants were subjected to an equimolar concentration of Na₂SO₄ (25 mM) and NaCl (50 mM) for 15 days. Our results showed that leaf growth rate was more depressed by 25 mM Na₂SO₄ than by 50 mM NaCl. The total fatty acid contents did not show any change in plants. α-Linolenic, palmitic, and linoleic acids were the major fatty acids. The identification of basil leaf fatty acids has not been previously studied and this work revealed the predominance of polyunsaturated fatty acids. Under both salts, leaf fatty acid composition remained unchanged. Regarding the essential oil yield, it decreased significantly by 28 % under 25 mM Na₂SO₄ and showed an increase by 27 % under 50 mM NaCl. The major volatile compound in leaves was linalool with 34.3 % of total essential oil constituents, followed by eugenol (19.8 %), 1.8-cineole (14.4 %) and methyl eugenol (5.2 %). Further, levels of eugenol and methyl eugenol were most modulated by salt, and the negative correlation between these two compounds reflects the stimulation of O-methyltransferase activity under both salts.     

Antioxidants and unsaturated fatty acids are involved in salt tolerance in peanut

To explore the possible physiological mechanism of salt tolerance in peanut, we investigated the effect of salinity on antioxidant enzyme activity, fatty acid composition, and chlorophyll fluorescence parameters. Seedlings at the initial growth stage had been treated with 0, 100, 150, 200, 250, and 300 mM NaCl for 7 days. Results showed that fresh mass and dry mass decreased with the rise of the NaCl concentration. They decreased significantly when the NaCl concentration was more than 200 mM. The PSII’s highest photochemical efficiency (F _v/F _m) was not affected before treating 250 mM NaCl. However, the PSII (ΦPSII)’s actual photochemical efficiency of decreased after treating 200 mM NaCl. Both the initial fluorescence (F _o) and non-photochemical quenching (NPQ) increased after 200 mM NaCl treatment. PSI oxidoreductive activity (ΔI/I _o) was not affected before 200 mM NaCl. The malondialdehyde (MDA) content increased with the rise of the NaCl concentration. The activities of ascorbate peroxidase (APX) and superoxide dismutase (SOD) activities increased first and then decreased, while the content of H₂O₂ and O ₂ ^?· decreased first and then increased. Treated with 150 mM NaCl, the linolenic acid (18:3) and linoleic acid (18:2) of monogalactosyldiacylglycerols (MGDG), digalactosyldiacylglycerols (DGDG), sulphoquinovosyldiacylglycerols (SQDG) as well as phosphatidylglycerols (PG), the ratio of DGDG/MGDG increased, and the opposite results were obtained with 300 mM NaCl. The double bond index (DBI) of MGDG, DGDG, SQDG, and PG also increased after treating 150 mM NaCl. These conclusions verified that increased unsaturated fatty acid content in membrane lipid of peanut leaves could improve salt tolerance by alleviating photoinhibition of PSII and PSI.     

Modulation in fatty acid composition influences salinity stress tolerance in Frankia strains

Frankia strains, isolated from Hippöphae salicifolia D. Don, were utilized to examine the utility of lipid amendments in the strains’ strategic survival against salinity. Frankia strains are known to withstand severe temperature fluctuations (?20 °C to +30 °C), nitrogen deprivation and low soil water content. It was interesting to note that these strains were also able to tolerate a considerable range of salinity. Strains were subjected to 250 mM (500 mM for HsIi10) and 750 mM NaCl treatment, which were the critical and inhibitory NaCl concentrations, respectively, for the experimental strains. Their lipid profiles showed dynamic modifications in saline environment; 16–18 carbon chain fatty acids were of predominant occurrence in the lipid membrane. In the critical NaCl environment, there was an increase in fatty acid unsaturation (measured in terms of MUFA/PUFA ratio), which preserved normal membrane fluidity. Conversely, at the inhibitory salinity level, increased fatty acid saturation made the membrane highly rigid and susceptible to breakage and electrolyte loss. The differential capability of fatty acid desaturation could be a major factor in variation of salt sensitivity/tolerance patterns among these strains. Also, management of the lipid profile in response to salinity was found to be a strain-specific character.     

Optimization of biomass and fatty acid productivity of Scenedesmus obliquus as a promising microalga for biodiesel production

Nowadays, microalgae are discussed as a promising feedstock for biodiesel production. The present study examines the possibility of enhancement of fatty acid productivity of Scenedesmus obliquus by modifications of the culture medium composition. The effect of different concentrations of sodium bicarbonate, salinity, potassium nitrate, glycerol and sugarcane molasses on the enhancement of biomass and esterified fatty acids production was studied. NaHCO₃ caused an increase in the biomass productivity at low concentrations (0.5 g L^?1), while negatively affected fatty acid productivity at all tested concentrations. Increase of salinity enhanced both biomass and fatty acid productivity. The optimum NaCl concentration and sea water ratio were 0.94 g L^?1 and 25 % which resulted in 56 and 39 % increase in fatty acid productivity, respectively. Nitrogen deficiency showed increase in fatty acid content by 54 % over control but fatty acid productivity was decreased as a result of growth inhibition. Nitrogen-free cultures and cultures treated with ?50 % concentrations of KNO₃ showed 96 and 42 % decrease in EFA productivity, respectively, as compared with the control. Addition of 0.05 and 0.1 M of glycerol increased the biomass productivity by 6 and 5 %, respectively but showed no significant effect on fatty acid productivity as a result of decrease in fatty acid content. Finally, usage of sugarcane molasses stimulated both biomass and fatty acid content. The increase in fatty acid productivity was 32, 65 and 73 % above the control level at 1, 3 and 5 g L^?1 of sugarcane molasses, respectively.     

Effect of NaCl on fatty acids, phenolics and antioxidant activity of Nigella sativa organs

The objective of this study was to investigate the effect of salinity on growth, fatty acid composition, phenol content and antioxidant activity of Nigella sativa organs. Plants were grown hydroponically under NaCl stress (0, 20 40 and 60 mM). The results indicated that salinity affected N. sativa growth. The fatty acid composition of the leaves and the roots was investigated for the first time and major fatty acids were linolenic acid (58.1%) in the leaves and linoleic (43.9%) and palmitic (33.3%) acids and in the roots. Total fatty acid (TFA) content of the leaves decreased at 60 mM NaCl while root TFA increased at 20 and 40 mM NaCl. Moreover, the fatty acid composition was affected by NaCl; in leaves, the double bond index (DBI) decreased accompanied by a decrease of the level of linolenic acid which reached 14% at 60 mM NaCl. However, root DBI degree increased at 40 at 60 mM NaCl provoked mainly by the increase of the amount of linoleic acid by 15 and 8%, respectively, and the decrease of the amount of palmitic acid by 20 and 14%, respectively. Salt stress increased total polyphenol and individual phenolic acid contents in shoots. Moreover, the antiradical activity of the shoots (DPPH) increased at 60 mM NaCl. However, in roots, the total polyphenol content and the antiradical activity decreased sharply with increasing NaCl doses. Data reported here revealed the variation of fatty acids and phenolic compound contents in different organs of N. sativa, and the possible role of theses changes in the plant salt response were discussed.     

Physiological and proteomic analysis of salinity tolerance of the halotolerant cyanobacterium <Emphasis Type="Italic">Anabaena</Emphasis> sp

The halotolerant cyanobacterium Anabaena sp was grown under NaCl concentration of 0, 170 and 515 mM and physiological and proteomic analysis was performed. At 515 mM NaCl the cyanobacterium showed reduced photosynthetic activities and significant increase in soluble sugar content, proline and SOD activity. On the other hand Anabaena sp grown at 170 mM NaCl showed optimal growth, photosynthetic activities and comparatively low soluble sugar content, proline accumulation and SOD activity. The intracellular Na⁺ content of the cells increased both at 170 and 515 mM NaCl. In contrast, the K⁺ content of the cyanobacterium Anabaena sp remained stable in response to growth at identical concentration of NaCl. While cells grown at 170 mM NaCl showed highest intracellular K⁺/Na⁺ ratio, salinity level of 515 mM NaCl resulted in reduced ratio of K⁺/Na⁺. Proteomic analysis revealed 50 salt-responsive proteins in the cyanobacterium Anabaena sp under salt treatment compared with control. Ten protein spots were subjected to MALDI-TOF–MS/MS analysis and the identified proteins are involved in photosynthesis, protein folding, cell organization and energy metabolism. Differential expression of proteins related to photosynthesis, energy metabolism was observed in Anabaena sp grown at 170 mM NaCl. At 170 mM NaCl increased expression of photosynthesis related proteins and effective osmotic adjustment through increased antioxidant enzymes and modulation of intracellular ions contributed to better salinity tolerance and optimal growth. On the contrary, increased intracellular Na⁺ content coupled with down regulation of photosynthetic and energy related proteins resulted in reduced growth at 515 mM NaCl. Therefore reduced growth at 515 mM NaCl could be due to accumulation of Na⁺ ions and requirement to maintain higher organic osmolytes and antioxidants which is energy intensive. The results thus show that the basis of salt tolerance is different when the halotolerant cyanobacterium Anabaena sp is grown under low and high salinity levels.     

Roots volatiles and fatty acids of coriander (<Emphasis Type="Italic">Coriandrum sativum</Emphasis> L.) grown in saline medium

An hydroponic culture was conducted to investigate the effect of saline stress on the essential oil and fatty acid composition of Tunisian coriander (Coriandrum sativum L.) roots. Ten days old coriander seedlings were treated during 3 weeks with different NaCl concentrations (0, 25, 50 and 75 mM). Roots volatile components and fatty acids were analyzed. The essential oil yield was 0.06% in the control, on the basis of dry matter weight, and did not changed at low concentration (25 mM), while it increased significantly with increasing NaCl concentrations to reach 0.12 and 0.21% at 50 and 75 mM NaCl, respectively. The major volatile component was (E)-2-dodecenal with 52% of total essential oil constituents, followed by decanal, dodecanal, (E)-2-tridecenal and (E)-2-dodecenal. Further, the amount of these compounds was affected differently by the NaCl level. Total fatty acid amount of coriander roots increased significantly only with 50 and 75 mM NaCl. Three major fatty acids: linoleic (43%), oleic (25.5%) and palmitic (21.6%) were identified. Linoleic acid amount remains unchanged at 25 mM, while it increased with raising NaCl concentrations. However, oleic acid amount decreased only at 25 mM and no effect was observed at 50 and 75 mM. Fatty acid percentages were differently affected by salt. The oleic/linoleic ratio was reduced with raising NaCl concentrations.     

Optimization of cultivation conditions for fatty acid composition and EPA production in the eustigmatophycean microalga Trachydiscus minutus

We determined the effects of cultivation conditions (nitrogen source, salinity, light intensity, temperature) on the composition of polyunsaturated fatty acids (PUFAs) and the production of eicosapentaenoic acid (EPA) in the laboratory cultured eustigmatophycean microalga, Trachydiscus minutus. T. minutus was capable of utilizing all nitrogen compounds tested (potassium nitrate, urea, ammonium nitrate, ammonium carbonate) with no differences in growth and only minor differences in fatty acid (FA) compositions. Ammonium carbonate was the least appropriate for lipid content and EPA production, while urea was as suitable as nitrates. Salinity (0.2 % NaCl) slightly stimulated EPA content and inhibited growth. Increasing salinity had a marked inhibitory effect on growth and PUFA composition; salinity at or above 0.8 % NaCl was lethal. Both light intensity and temperature had a distinct effect on growth and FA composition. The microalga grew best at light intensities of 470–1,070 μmol photons m^?2 s^?1 compared to 100 μmol photons m^?2 s^?1, and at 28 °C; sub-optimal temperatures (20, 33 °C) strongly inhibited growth. Saturated fatty acids increased with light intensity and temperature, whereas the reverse trend was found for PUFAs. Although the highest level of EPA (as a proportion of total FAs) was achieved at a light intensity of 100 μmol photons m^?2 s^?1 (51.1?± 2.8 %) and a temperature of 20 °C (50.9?±?0.8 %), the highest EPA productivity of about 30 mg L^?1?day^?1 was found in microalgae grown at higher light intensities, at 28 °C. Overall, for overproduction of EPA in microalgae, we propose that outdoor cultivation be used under conditions of a temperate climatic zone in summer, using urea as a nitrogen source.     

The role of salinity in seed maturation of the euhalophyte Suaeda salsa

Controlled conditions were used to investigate how salinity maintains the salt tolerance of seeds and seedlings of the euhalophyte Suaeda salsa. Seeds were harvested from S. salsa plants that had been treated with 1 or 500 mM NaCl for 113 days in a glasshouse. The results showed that high salinity (500 mM NaCl) increased chlorophyll concentration and oxygen production in embryos of maturing seeds. At 500 mM NaCl, the phosphatidylglycerol and sulfoquinovosyldiacylglycerol levels and the digalactosyldiacylglycerol/monogalactosyldiacylglycerol ratio were higher in young seedlings derived from seeds whose source plants were cultured in 500 mM rather than in 1 mM NaCl. When seeds were incubated with 600 mM NaCl, the conductivity and malondialdehyde concentration in the embryos was greater if the source plants had been cultured in 1 mM rather than in 500 mM NaCl. The opposite pattern was evident for seedling survival and shoot weight. In conclusion, salinity during seed maturation may increase the salt tolerance of seeds and seedlings by increasing the oxygen production in the embryos of the maturing seeds and by changing the lipid composition of membranes in the seedlings.     

Plant growth regulators ameliorate the ill effect of salt stress through improved growth,photosynthesis, antioxidant system,yield and quality attributes in <Emphasis Type="Italic">Mentha piperita</Emphasis> L.

The roles of plant growth regulators (PGRs) in plants are well documented. However, there is a little information regarding their roles in alleviating salt stress in plants, particularly peppermint. This necessitated the evaluation of the efficiency of three selected PGRs in counteracting the ill effect of salt stress by conducting a pot experiment on peppermint (Lamiaceae). Three uniform size suckers were transplanted in each pot containing proper nutrients. Thirty day old plants were subjected to 4 levels of salinity, viz. 0, 50, 100 or 150 mM NaCl. Salt stress was given at 30 days after their transplantation (DAT). Plants were sprayed twice, i.e., at 60 and 75 DAT with 10^?6 M each of gibberellic acid (GA₃), salicylic acid (SA) or triacontanol (Tria). The sampling was made at 100 DAT and harvesting at 120 DAT. The graded levels of salinity decreased growth, photosynthesis, carbonic anhydrase (CA) activity, NPK content, peltate glandular trichome (PGT) density, essential oil (EO) and menthol content and herb, EO and menthol yield, but increased catalase (CAT), peroxidase (POX) and superoxide dismutase (SOD) activities and proline content linearly. Spray of PGRs particularly SA improved all parameters under both salt and salt free conditions. The maximum values for yields of herb, EO and menthol were noted with 0 mM NaCl?×?SA. However, antioxidants, proline content, PGT density and EO content were found to be maximum with 150 mM NaCl?×?SA.     

Modulation of osmotic adjustment and antioxidant status in salt-stressed leaves of Thermopsis turcica

Thermopsis turcica is distributed naturally in saline soils. Interestingly, how T. turcica can live in harsh salt conditions is unknown. To study its defense responses under salinity, T. turcica was grown in a medium containing 100 and 200 mM NaCl for 7 and 14 days. Physiological parameters, ion contents, reactive oxygen species accumulation, activities of antioxidant enzymes/isozymes, NADPH oxidase enzyme/isozyme, lipid peroxidation (TBARS) and osmolyte contents were investigated. Stress caused a rapid decline in relative growth rate, relative water content and chlorophyll fluorescence (F _v/F _m) under both NaCl treatments. These traits were more suppressed at 200 mM NaCl. The decline in osmotic potential (Ψ _Π) with salinity increased the gradient for water flux into the cell and assisted in turgor maintenance. The increased membrane permeability under stress caused the entrance of excess Na⁺ and K⁺ into the cell. Stress decreased superoxide dismutase, catalase and peroxidase after 14 days of growth in 200 mM NaCl, whereas glutathione reductase (GR) increased throughout the experiment. While ascorbate peroxidase (APX) increased by 44 % at 7 days, it decreased after 14 days exposure to 200 mM NaCl. 200 mM NaCl caused the highest increase in TBARS at 14 days, indicating a decrease in OH^· scavenging activity. Increasing concentrations of salinity caused an increase in glycine betaine (GB) and choline (Cho), though an increase in proline was only observed at 200 mM NaCl for 14 days. Briefly, H₂O₂ was more efficiently eliminated in 100 mM-treated plants by the ascorbate–glutathione cycle in which APX acts a strong catalyst together with GR. Also, Cho and GB help to maintain osmotic adjustment and cytoplasmic function.     

Growth,pigments, and biochemical composition of marine red alga Gracilaria crassa

The marine red alga Gracilaria crassa was investigated for its proximate composition, minerals, fatty acids, amino acids, and agar content to decipher its nutritional implications. The growth performance and pigments were studied under different combinations of temperature and salinity. On a dry weight basis the total lipid content was 1.30?±?0.05 %, protein was 5.18?±?0.64 %, carbohydrate was 42.0?±?1.2 %, ash was 43.18?±?1.15 %, and agar content was 21.52?±?0.73 %. Appreciable amounts of macro-, micro-nutrients (K?>?Na, Ca, Mg, and Fe), and essential amino acids (Ileu, His, Thr, Leu, and Lys) were found. Palmitic, stearic acid, and arachidonic acid were major fatty acids detected. The alga showed maximum daily growth rate (DGR %) 5.8?±?0.09 % at 25 °C, 35 ‰ salinity. The highest content of pigment R-phycoerythrin (444.7?±?1.9 μg g^?1 fresh weight (FW) basis) was obtained at 25 ‰ salinity at 35 °C while that of R-phycocyanin (476.3?±?2.3 μg g^?1 DW) at 30 ‰ salinity at 30 °C. This study revealed that this alga can be utilized as a potential source for food and feed. The data generated on best growth conditions will be very useful for farming of G. crassa in open sea. This alga could be used for production of natural colorants at defined control condition.     

Development changes in calla lily plants due to salt stress

Soil salinity is mainly caused by excessive use of fertilizers and the use of poor quality water, and adversely affected crop growth especially when grown in protected environments. Soil salinity causes salt stress in plants, which inhibits plant growth, leading to morphological, metabolic and physiological changes. Though it is a major problem occurs more frequently, there is less information on the behavior of calla lily (Zantedeschia aethiopica) under these conditions, and most studies are conducted with other species of the genus Zantesdeschia. Therefore, this study aimed to evaluate ecophysiological, biochemical and anatomical growth responses of calla lily plants to salt stress. Rhizomes were grown in trays containing coconut fiber as a substrate and treated with 0, 25, 50, 75 and 100 mM NaCl to induce stress. A decrease in plant height was observed, as well as in the number of tillers and leaves, main root length, fresh and dry matter of the shoot and root system. A reduction in photosynthetic rate, stomatal conductance and transpiration rate was observed at 60 days. However, after 90 days, the photosynthetic rate was unchanged, with increased stomatal conductance and transpiration rate for plants exposed to 75 mM NaCl. Salt stress caused a higher accumulation of carbohydrates in shoots and roots. Thus, high concentrations of NaCl affect the development of calla lily, indicating that this species is susceptible to salt stress.     

Salinity improves chilling resistance in Suaeda salsa

Suaeda salsa L., a C3 euhalophytic herb, is native to saline soils, demonstrates high resistance to salinity stress. The effect of chilling stress on S. salsa under high salinity, particularly the change in unsaturated fatty acid content within membrane lipids, has not been investigated. After a 12 h chilling treatment (4 °C) performed under low irradiance (100 μmol m^?2 s^?1), the chlorophyll contents, maximal photochemical efficiency of photosystem II (F _v/F _m) and actual PSII efficiency (ΦPSII) were determined. These measurements were significantly decreased in S. salsa leaves in the absence of salt treatment yet there were no significant changes with a 200 mM NaCl treatment. Chlorophyll contents, F _v/F _m and ΦPSII in S. salsa under 200 mM NaCl were higher than those without salt treatment. The unsaturated fatty acid content and the double bond index (DBI) of major membrane lipids of monogalactosyldiacylglycerols, digalactosyldiacylglycerols (DGDG), sulphoquinovosyldiacylglycerols and phosphatidylglycerols (PG) significantly increased following the chilling treatment (4 °C) (with 12 h of low irradiance and 200 mM of NaCl). The DBI of DGDG and PG was decreased in the absence of the salt treatment. These results suggest that in the euhalophyte S. salsa, a 200 mM NaCl treatment increases chilling tolerance under conditions of low irradiance (100 μmol m^?2 s^?1).     

Physio-Biochemical Composition and Untargeted Metabolomics of Cumin (Cuminum cyminum L.) Make It Promising Functional Food and Help in Mitigating Salinity Stress

Cumin is an annual, aromatic, herbaceous, medicinal, spice plant, most widely used as a food additive and flavoring agent in different cuisines. The study is intended to comprehensively analyse physiological parameters, biochemical composition and metabolites under salinity stress. Seed germination index, rate of seed emergence, rate of seed germination, mean germination time, plant biomass, total chlorophyll and carotenoid contents decreased concomitantly with salinity. In contrast, total antioxidant activity, H₂O_2, proline and MDA contents increased concurrently with stress treatments. Total phenolic and flavonoid contents were decreased initially about 1.4-fold at 50 mM, and thereafter increased about 1.2-fold at 100 mM NaCl stress. Relative water content remained unchanged up to 50 mM NaCl stress, and thereafter decreased significantly. About 2.8-fold electrolyte leakage was found in 50 mM, which increases further 4-fold at 100 mM NaCl stress. Saturated fatty acids (FAs) increased gradually with salinity, whereas unsaturation index and degree of unsaturation change arbitrarily along with the percent quantity of unsaturated FAs. Total lipid and fatty acid composition were significantly influenced by salinity stress. A total of 45 differentially expressed metabolites were identified, including luteolin, salvianolic acid, kaempferol and quercetin, which are phenolic, flavonoid or alkaloids in nature and contain antioxidant activities. Additionally, metabolites with bioactivity such as anticancerous (docetaxel) and antimicrobial (megalomicin) properties were also identified. The study evidenced that plant shoots are a rich source of metabolites, essential amino acids, phenolic compounds and fatty acids, which unveil the medicinal potential of this plant, and also provide useful insight about metabolic responses under salinity stress.     

Salt effects on the growth, mineral nutrition, essential oil yield and composition of marjoram (Origanum majorana)

The aim of this work was to investigate the growth, mineral nutrition and essential oil composition of marjoram aerial part. Seedlings were cultivated for 20 days on nutrient solution, and then transferred to hydroponic solution with different NaCl concentrations (0, 50, 100, 150 mM). Plants were harvested after 17 days of treatment. Mineral nutrition and essential oil composition of shoots were determined. Results showed that growth, water content and development of the different organs of marjoram plant were affected just at the highest NaCl concentration (150 mM). Furthermore, salt did not seem to affect leaf area and root length but reduced the number of leaves. An increase in the total leaf surface and its thickness was observed at different NaCl concentrations. At 50 mM NaCl, sodium was primarily accumulated in roots but at 150 mM, it was strongly accumulated in leaves. However, Cl^? accumulation was lower at higher NaCl concentrations. Essential oil yield of marjoram shoots was 0.12% in the control and 0.10% at 50 mM but an important decrease was observed at 100 mM (0.05%). Thirty-three components were identified belonging to different chemical classes. In the control, the essential oil was found to be rich in trans-sabinene hydrate (47.67%), terpinen-4-ol (20.82%) and cis-sabinene hydrate (7.23%). The proportions of these main compounds were differently affected by salt.     

Spore associated bacteria of arbuscular mycorrhizal fungi improve maize tolerance to salinity by reducing ethylene stress level

The role of spore associated bacteria of arbuscular mycorrhizal fungi (AMF) in improving plant growth and alleviating salt stress is a potential area to explore. In the present study, 22 bacteria isolated from the spore walls of AMF were identified to contain 1-aminocyclopropane-1-carboxylate deaminase. These were tested for their ability to improve seed germination and alleviate salt stress in the early growth of maize. Among the isolates, 19 bacteria that were able to grow at 4?% NaCl were used for germination assay. Two bacteria and seven bacteria significantly improved maize seed germination at 100 mM NaCl and 200 mM NaCl, respectively. Based on the presence of plant growth promoting (PGP) characters and the ability to improve seed germination, five strains were chosen for further experiments. At 0 mM NaCl, all the strains were able to increase maize shoot and root growth significantly. At 25 mM NaCl, except for Bacillus aryabhattai S210B15, all the strains were able to increase shoot and root growth significantly. At 50 mM NaCl, Bacillus aryabhattai S110B3 and B. aryabhattai S210B15 significantly improved shoot length, whereas, Pseudomonas koreensis S2CB35 and B. aryabhattai S210B15 significantly increased root length. Although salinity increased ethylene production in maize, bacterial inoculation significantly reduced the ethylene level at 0, 25 and 50 mM NaCl. Among the five strains, only P. koreensis S2CB35 showed the presence of PGP functional traits of nifH, acdS and nodA genes.     

Response of Bur and Red oak seedlings to NaCl-induced salinity

Growth performance of Bur oak (Q. macrocarpa Michx.) and Red oak (Q. rubra L.) under salinity conditions was assessed by growing seedlings in the presence of increasing levels of NaCl. Salinity reduced root growth in both species, although its repressive effect was more pronounced in Red oak. Exposure to 75 mM NaCl for 3 weeks almost arrested root growth in Red oak, while it reduced it only by 40 % in Bur oak. Red oak roots showed extensive necrosis and limited branching. Salinity also induced leaf injury, which at a NaCl level of 25 mM was less severe in Bur oak possibly due the higher activity of catalase, superoxide dismutase, and dehydroascorbate reductase enzymes participating in the detoxification of reactive oxygen species. Relative to Red oak, a higher retention of photosynthetic rate was observed in Bur oak grown under saline conditions. Salinity also altered nutrient uptake and accumulation in root and leaf tissue. Compared to Red oak, the content of magnesium and calcium in Bur oak leaves exposed to NaCl remained elevated, while an opposite trend was observed in root tissue. This was in contrast to nitrogen which was not altered by salinity in Bur oak, while it increased in roots of Red oak. The better performance of Bur oak root tissue under salinity conditions was ascribed to structural modifications of the root system with maturation of casparian bands and suberinization occurring closer to the root tip. These structures are known to act as barriers enhancing ion selectivity. Collectively this study demonstrates that relative to Red oak, Bur oak is more tolerant to NaCl-induced salinity conditions.     

Physiological and epigenetic analyses of <Emphasis Type="Italic">Brassica napus</Emphasis> seed germination in response to salt stress

Salinity stress significantly affects plant growth and development because of osmotic stress, ion toxicity, and nutrient imbalance. Therefore, salinity stress becomes a serious threat to rapeseed production in agriculture. Plants evolved a series of complex mechanisms, including morphological changes, physiological adjustment, and gene expression regulation, at a molecular level to adapt to salt stress. Epigenetic regulations, including DNA methylation and histone modification, play a major role in tuning gene expression in plant response to environmental stimuli. Although many progresses have been reported in plant response to salt stress, the epigenetic changes in Brassica napus under salt stress are far from being understood. A series of physiological parameters, including water content, proline content, malondialdehyde content, electrolyte leakage, and antioxidant enzyme activities, under different concentrations (0, 25, 50, and 100 mM) of NaCl treatment in “Yangyou 9” was determined at the germination stage. Immunofluorescent staining and high-performance liquid chromatography-assisted quantification were conducted to analyze the level and distribution patterns of DNA and histone methylation under salt stress. Results of morphological and physiological analyses under salt stress indicated that 25 mM NaCl treatment promoted the growth of “Yangyou 9” seedlings, whereas 50 and 100 mM NaCl treatments inhibited the growth of “Yangyou 9” seedlings. Epigenetic investigations showed that 25 mM NaCl mediated the enrichment of H3K4me3, as well as decreases in H3K9me2 and 5-methylcytosine (5-mC), whereas 50 and 100 mM NaCl induced increases in H3K9me2 and 5-mC and a decrease in H3K4me3. Overall, this study offers new insights into the epigenetic changes in salt stress response in rapeseed, and this information would be propitious to engineer crops with enhanced salt tolerance.