Increasing Salt Stress Research Articles

Grain filling and yield of mung bean affected by salicylic acid and silicon under salt stress

ABSTRACTTwo experiments were carried out in 2013 and 2014, to investigate changes in grain filling rate (GFR), grain filling duration (GFD) and yield of mung bean in response to salicylic acid (SA) and silicon (Si) under salt stress (0, 3, 6 and 9 dS m−1). In experiment 1, four levels of SA (0, 0.5, 1 and 1.5 mM), but in experiment 2, two levels of SA (0 and 1 mM) and Si (0 and 2 mM) were applied. In experiment 1, GFR, GFD, yield components, biological and grain yields and harvest index were decreased with increasing salt stress. Application of different levels of SA, especially 1 mM, increased GFR, but decreased GFD. In experiment 2, GFD under salinity was shorter than that under non-saline condition, resulting in comparatively smaller grains. Application of Si and particularly SA accelerated grain development under all salinity treatments. The superiority of SA treated plants in GFR, grain weight and grains per plant resulted in greater grain yield per plant under saline and non-saline conditions.

Photosynthetic Traits of Plants and the Biochemical Profile of Tomato Fruits Are Influenced by Grafting, Salinity Stress, and Growing Season.

Changes in the photosynthetic traits of plants and metabolic composition of fruits of two tomato cultivars, grafted onto two rootstocks, grown in three salinity levels were studied in two growing periods during the season. Increased salinity stress conditions lowered water potential, stomatal conductance, and transpiration rate of grafted tomato plants, in both growing periods. Water deficit induced stomatal closure, which resulted in stomatal limitation of photosynthesis. The proline content in tomato leaves increased and was closely correlated with salinity. Some of the quality parameters of tomato fruits were affected by rootstock. The sugar/acid ratio was the highest in fruits of 'Belle'/'Maxifort' grafts. With increasing salt stress conditions from 40 to 60 mM NaCl, the lycopene content increased and ascorbic acid content decreased in fruits of 'Gardel'/'Maxifort' grafts, indicating the ability of this scion/rootstock combination to mitigate the toxicity effect of salinity stress. A higher phenolics concentration in fruits from the first growing period may be an additional indicator of stress, caused by higher temperatures and solar radiation, compared with the later period.

VvWRKY30, a grape WRKY transcription factor, plays a positive regulatory role under salinity stress

High salinity severely inhibits the growth and productivity of grape plants. However, knowledge of salt-stress regulation remains limited in WRKY members of grapes. Here, we isolated a novel VvWRKY30 gene from Vitis vinifera L. and studied its role in salt-stress resistance. The VvWRKY30 protein fused with green fluorescent protein localized to the nucleus and the transcriptional activation activity of VvWRKY30 was confirmed in yeast. Moreover, VvWRKY30 showed key transcriptional activity domain at the N-terminal and specifically binds to the W-BOX. VvWRKY30 showed the highest expression in the shoot tip and functional leaves of grape plants. VvWRKY30 expression was induced by salt as well as stress signaling molecules H2S and H2O2. Overexpression of VvWRKY30 in Arabidopsis increased its resistance to salt stress at different stages of growth. Under salinity stress, VvWRKY30 overexpressing lines had higher antioxidant activities and lower reactive oxygen species contents. Soluble sugar and proline concentrations also increased in VvWRKY30 overexpressing lines in the presence of NaCl. In addition, the transcription of genes related to antioxidant biosynthesis, glyco-metabolism and proline biosynthesis increased in the VvWRKY30 overexpressing lines. Taken together, this study confirmed the important role of VvWRKY30 in increasing salt stress resistance by regulating reactive oxygen species-scavenging and the accumulation of osmoticum.

Ectopic Expression of GsSRK in Medicago sativa Reveals Its Involvement in Plant Architecture and Salt Stress Responses.

Receptor-like kinases (RLK) play fundamental roles in plant growth and stress responses. Compared with other RLKs, little information is provided concerning the S-locus LecRLK subfamily, which is characterized by an extracellular G-type lectin domain and an S-locus-glycop domain. Until now, the function of the G-type lectin domain is still unknown. In a previous research, we identified a Glycine soja S-locus LecRLK gene GsSRK, which conferred increased salt stress tolerance in transgenic Arabidopsis. In this study, to investigate the role of the G-type lectin domain and to breed transgenic alfalfa with superior salt stress tolerance, we transformed the full-length GsSRK (GsSRK-f) and a truncated version of GsSRK (GsSRK-t) deleting the G-type lectin domain into alfalfa. Our results showed that overexpression of GsSRK-t, but not GsSRK-f, resulted in changes of plant architecture, as evidenced by more branches but shorter shoots of GsSRK-t transgenic alfalfa, indicating a potential role of the extracellular G-type lectin domain in regulating plant architecture. Furthermore, we also found that transgenic alfalfa overexpressing either GsSRK-f or GsSRK-t showed increased salt stress tolerance, and GsSRK-t transgenic alfalfa displayed better growth (more branches and higher fresh weight) than GsSRK-f lines under salt stress. In addition, our results suggested that both GsSRK-f and GsSRK-t were involved in ion homeostasis, ROS scavenging, and osmotic regulation. Under salt stress, the Na+ content in the transgenic lines was significantly lower, while the K+ content was slightly higher than that in WT. Moreover, the transgenic lines displayed reduced ion leakage and MDA content, but increased SOD activity and proline content than WT. Notably, no obvious difference in these physiological indices was observed between GsSRK-f and GsSRK-t transgenic lines, implying that deletion of the GsSRK G-type lectin domain does not affect its physiological function in salt stress responses. In conclusion, results in this research reveal the dual role of GsSRK in regulating both plant architecture and salt stress responses.

Comparative Assessment of salt tolerance in five Indian varieties of Rice (Oryza sativa L.)

Drought and salt stress are the two major abiotic determinants of plant growth and productivity. This study deals with comparative assessment of drought and salt responses of five rice varieties namely ‘Karuna’, ‘Neeraja’, ‘Thekkancheera’, ‘Rasmi’ and ‘Aryan’ under varying concentrations of sodium chloride (50mM, 100mM, 150mM, and 200mM), respectively. Germination percentage, root length and shoot length were determined after two weeks. As expected, in all the three varieties, the seed germination percentage, shoot and root length decreased with the increase in salt stress. The highest values of the aforementioned parameters were observed in the untreated controls and lowest values were recorded in the test samples subjected to 200 mM NaCl, respectively. The response of the varieties to increasing salt tolerance was in order ‘Rasmi’ > ‘Karuna’, ‘Neeraja’ > ‘Thekkancheera’ > ‘Aryan’. During the experiment, ‘Rashmi’ showed less decrease in germination percentage, root and shoot length as compared to the other varieties. These results indicate that ‘Rashmi’ variety is more tolerant to salt stress. Thus, in future, after further physiological and molecular evidences, this variety can be strategically grown as an alternative to other cereal crops, under salt-stressed environments.

SALINITY STRESS AMELIORATION USING HUMIC ACID AND MYCORRHIZAE ON PEPPER PLANTS

Salinity is destructive factor and one of various abiotic stresses which strongly affects crop productivity and limits marketable yield of vegetable crops, for example pepper plants. This work studied the effects of sole application of each of Humic Acid (HA) and Arbuscular Mycorrizal Fungi (AMF), Glomus fasciculatum inoculation and their combinations in order to reduce the harmful effects of salinity stress on growth, yield and endogenous bio-constituents in pepper cultivar top star. Growth parameters at 75 days after transplanting and yield components were decreased under levels of salt stress (2000 or 4000 ppm). Applied of humic acid and mycorrhizae, partially counteracted the harmful effects of salinity stress levels. By increasing salt stress levels, proline, peroxidase and catalase activities and Na content were increased, but photosynthetic pigments in leaves and N, P, K content in shoots of pepper plants were decreased. In addition, all treatments of humic acid and mycorohizae either alone or in combination under different salt stress levels, slightly increased the content of proline, N, P, K and photosynthetic pigments, peroxidase and catalase activities while, Na content was decreased in pepper plants. It was observed that, the interaction between humic acid and mycorohizae increased the positive effect of mycorohizae inoculation. Results indicated also that, mycorrhizal inoculation help in ameliorating the damage caused by salt stress conditions in pepper plants. Application of humic acid combined with mycorrhizae, promote much more plant growth. These results provide support for the field application of humic acid and mycorrhizae to decline the harmful effects of salty soils.

Effects of NaCl on Germination and Seedling Growth in Macrotyloma uniflorum and Vigna mungo

Among abiotic stresses, drought and salinity are two major determinants due to high magnitude of their impact and wide occurrence. Salinity considerably limits the productivity of crops and thus, considered as the most destructive abiotic factor. In the present study, response of Macrotyloma uniflorum and Vigna mungo to salt (NaCl) stress imposed at germination and seedling growth stages was investigated. The aim of the study was identify the physiological and morphological responses of selected leguminous crop. Seeds were obtained from the healthy plants, surface sterilized and placed under six salt stress levels (0, 4, 8, 12, 16, 20 dsm-1). Complete randomized design with three replicates was used for this experiment and the experiments were conducted during the year 2015 in the glasshouse of Department of Botany, DSB, Campus, Kumaun University, Nainital. In comparison to Macrotyloma uniflorum (77%), higher germination percentage was observed in Vigna mungo (99%) at all salinity levels. In both the species, germination percentage and seedling growth decreased with the increase in salinity stress. Though Vigna mungo showed higher values for root (0.17 g) and shoot dry mass (0.27 g) the dry weight percentage reduction was higher in this species as compared to Macrotyloma uniflorum. Decrease in biomass of seedling with increasing salt stress indicated that the stress not only affected germination but also the growth of seedlings, which indicates that the synthetic ability of seed and biomass of the seedlings was also affected. Seed vigor index declined with the increase in salt concentrations. Outcomes from the study could be helpful in understanding the plant’s nature against different levels of salt stress and that could be economically exploited by various able agencies. At each salinity level, M. uniflorum showed higher salt tolerance index as compared to V. mungo so it can be cultivated in fields with salty soil.

Morphological and biochemical response to salinity stress on Setariaitalicaseedlings

Salinity is considered as the most important abiotic stress limiting the crop production.The present investigation was made to study the impact of different concentrations of sodium chloride on growth, biochemical constituents and antioxidant enzymes of the seedlings of Setaria italica. Seeds were grown at different concentrations of NaCl [(0,25,50,75, and 100mM] for twenty five days. Salt stress influenced a significant modification in the level of osmolyte accumulation.The accumulation level of osmolytes such as proline, glycine betaine,phenol and antioxidant enzyme such as catalase (CAT) and hydrogen peroxide increased significantly with increasing salt stress conditionwhen compared to the control. A statistically significant decreaseof seed germination percentage,root and shoot length,photosynthetic pigments like chlorophyll a, chlorophyll b and proteins when higher concentration of NaCl added were recorded. From this experiment it was found that the foxtail millet crops can be sustained in optimum (75 mM) salinity condition. It was concluded that these osmolytes play a key role in generating tolerance against salt stress.

Salicylic Acid and Fish Flour Pre-treatments Affect Wheat Phenolic and Flavonoid Compounds, Lipid Peroxidation Levels under Salt Stress

The potential effect of combined salicylic acid and fish flour to improve plant tolerance to salt stress was investigated. This pre-treatment improved the growth of wheat seedlings under salinity when compared to control (untreated wheat seedlings). Moreover, combined pre-treatment improved significantly phenylalanine ammonia lyase (PAL) and peroxidase (POD) enzyme activities, also phenolic-flavonoid content in the shoots of salt stressed seedlings. One of the most important consequences of increase in salt stress is the oxidative tissue damage. In our study, salt stress increased lipid peroxidation levels (LPO) and also the loss of chlorophylls levels during stress might also be related to photo-oxidation resulting from oxidative stress. Whereas phenylalanine ammonia-lyase (PAL) activities of wheat shoots increased by a 2.1-fold under salt stress, the activities of shoots grown from seeds primed with salicylic acid and fish flour (SA + FF) increased by a 4-fold for 0.05 mM SA + FF, 4.8- fold for 0.1 mM SA + FF and 3.7-fold for 2.5 mM SA + FF combined pre-treatment under salt stress. Also, the combined salicylic acid + fish flour primed seedlings showed higher content of the scopoletin, and salicylic, syringic, vanilic and gallic acids under both salt and non-salinity stress conditions.

16S rRNA gene high-throughput sequencing reveals shift in nitrogen conversion related microorganisms in a CANON system in response to salt stress

Salinity is an important factor affecting the activity and community structure of nitrogen transformation-related microorganisms in natural and engineered ecosystems. However, salinity’s impact on microbial diversity in completely autotrophic nitrogen removal over nitrite (CANON) processes remains poorly described. In this study, the microbial community dynamic of a CANON system was comprehensively evaluated in response to increasing salt stress using 16S rRNA gene high-throughput sequencing technology. The CANON system can treat ammonia-rich (200mg/L) wastewater with salinity up to 15gNaCl/L after gradual acclimation to salt, and the maximum total nitrogen removal rate achieved was 0.23kg/m3/d at 10gNaCl/L. Salinity of 20gNaCl/L caused rapid deterioration of the nitrogen removal performance because of a sharp decline in the ammonia oxidation rate. Beta diversity with elevated salinity by redundancy analysis proved that salinity played an important role in the microbial community dynamics of the functional microbes in the CANON system. “Candidatus Kuenenia” anaerobic ammonia oxidation (anammox) bacteria and “Nitrosomonas europaea” ammonia oxidation bacteria were robust under salt stress and could survive at salinity up to 15gNaCl/L, while “Candidatus Jettenia” anammox bacteria were sensitive to salinity and even 5gNaCl/L caused a sharp decline in their abundance. The nitrite oxidation rate showed extreme sensitivity to 5gNaCl/L salinity; however, overgrowth of “Nitrospira” nitrite oxidation bacteria even at elevated salinity is a matter of concern for successful CANON operation. 16S rRNA gene high-throughput analyses offer new insights at high resolution and depth into the stability and dynamics of functional microbial communities in CANON systems under increasing salt stress, highlighting the importance of microbial diversity and balance in the CANON process.

Effects of salt stress on astaxanthin accumulation, gene expression of astaxanthin synthesis-related enzymes, and antioxidant indices in Haematococcus pluvialis

PDF HTML阅读 XML下载 导出引用 引用提醒 盐胁迫对雨生红球藻虾青素累积、虾青素合成相关酶基因表达和抗氧化指标的影响 DOI: 作者: 作者单位: 1. 河南师范大学水产学院, 河南 新乡 453007;2. 宁德师范学院 生物系, 福建 宁德 352100;3. 河南师范大学 生命科学学院, 河南 新乡 453007 作者简介: 江红霞(1974-),女,副教授,研究方向为水生生物资源与环境.E-mail:jianghongxia2007@126.com 通讯作者: 中图分类号: S96 基金项目: 河南省重点科技攻关项目（102102210181）；河南省水产学重点学科基金项目（2012）. Effects of salt stress on astaxanthin accumulation, gene expression of astaxanthin synthesis-related enzymes, and antioxidant indices in Haematococcus pluvialis Author: Affiliation: 1. College of Fisheries, Henan Normal University, Xinxiang 453007, China;2. Department of Biology, Ningde Normal University, Ningde 352100, China;3. College of Life Sciences, Henan Normal University, Xinxiang 453007, China Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为探讨盐胁迫对雨生红球藻（）虾青素合成的影响与机理，以及雨生红球藻各抗氧化机制之间的关系，本研究采用生化和分子生物学方法研究了不同浓度（0.04 mol/L、0.08 mol/L、0.12 mol/L和0.16 mol/L）和不同时间（3 d、6 d和9 d）的盐（NaCl）胁迫对雨生红球藻生长、虾青素积累、番茄红素-胡萝卜素酮化酶（Bkt）基因表达、超氧化物歧化酶（SOD）、过氧化氢酶（CAT）和谷胱甘肽过氧化物酶（GSH-Px）的活性以及丙二醛（MDA）含量的影响。结果表明，各胁迫时间的雨生红球藻的密度均随着盐胁迫浓度的增加而不断下降，在盐胁迫的第9天，雨生红球藻的死亡率和孢子比例均随着盐胁迫浓度的增加而不断升高；雨生红球藻虾青素含量、基因表达量均随着盐胁迫浓度和时间的增加而不断提高；雨生红球藻SOD、CAT和GSH-Px活性以及MDA含量在不同浓度和不同时间的盐胁迫下与对照组（0.00 mol/L NaCl）相比均升高，且在不同时间的0.12 mol/L NaCl胁迫下与对照组相比均显著升高（基因表达量在盐胁迫的早期（第3天）和中期（第6天）阶段较低，在盐胁迫的后期（第9天）阶段较高，而SOD、CAT和GSH-Px活性以及MDA含量在盐胁迫的早期和中期阶段较高，在盐胁迫的后期阶段较低。实验结果说明了适当浓度和时间的盐胁迫能促进雨生红球藻累积虾青素，雨生红球藻在盐胁迫下主要是通过提高虾青素合成相关酶基因的转录水平来促进虾青素的合成，其虾青素和抗氧化酶的抗氧化活性可能互为补充，共同保护雨生红球藻免受盐胁迫的氧化损伤。 Abstract:(Chlorophyceae, Order Volvocales), a freshwater green microalgal species, has commercial value owing to its ability to accumulate high concentrations of astaxanthin (up to 5% of dry weight). Astaxanthin (3,3'-dihydroxy--carotene-4,4'-dione) is a red ketocarotenoid which has many important biological functions, including antioxidant activity, regulation of immune responses, and disease resistance, and has the potential for application in the aquacultural, nutraceutical, pharmaceutical, and cosmetic industries. has a distinctive lifecycle as it exhibits a green motile stage and a red non-motile resting stage called an aplanospore. In general, astaxanthin accumulation in is restricted to the aplanospore stage. Astaxanthin is accumulated in extra-plastidic lipid vesicles as a secondary carotenoid, and it is believed to be synthesized in response to oxidative stress in the red aplanospore stage under unfavorable environmental conditions such as high light, temperature, and salinity, or low nutrient availability. Several enzymes such as lycopene -carotene ketolase (Bkt) are involved in the astaxanthin bios-y-n-thesis pathway in -carotene from lycopene, and CrtR-B and Bkt cat-alyze further steps leading to astaxanthin synthesis. Changes in expression of the genes encoding these three enzymes can critically affect the biosynthesis and accumulation of astaxanthin in . In addition, various ant-i-oxidant enzymes including superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) also have important protective effects for combating oxidative stress under unfavourable environmental conditions. We aimed to explore the effect of salt stress on astaxanthin accumulation in , by examining the mechanism of astaxanthin synthesis and the relationship between the different antioxidant mechanisms in at high salinity. We examined its growth rate; astaxanthin content; gene expression levels; SOD, CAT, and GSH-Px activities; and malondialdehyde (MDA) content at four salinity levels (0.04 mol/L, 0.08 mol/L, 0.12 mol/L, and 0.16 mol/L) over three timescales (3 days, 6 days, and 9 days). Our results showed that the density of decreased under increasing salinity over different periods of time, while its mortality rate and aplanospore proportion increased with increasing salt stress concentration by the ninth day of stress. Asta-xanthin content, gene expressions increased over time with increasing salinity. SOD, CAT, and GSH-Px activities and MDA content also increased in comparison to grown at the control level of 0 mol/L NaCl, and significantly increased at the 0.12 mol/L NaCl level ( gene expressions were lower during the early and mid-stages of salt stress (e.g., on the third and sixth days of observation), and increased by the ninth day. Meanwhile, SOD, CAT, and GSH-Px activities and MDA content were higher during early and mid-stage stress, but were lower by the ninth day. These results suggest that salt stress can improve astaxanthin accumulation over time in at the appropriate level of salt stress, despite its negative effects on growth. Astaxanthin synthesis in is promoted mainly through an increase in the transcription level of astaxanthin synthesis-related enzyme genes under salt stress, and the antioxid-ant activities of astaxanthin and antioxidant enzymes complement one other to protect from oxidative damage under salt stress. This study provides a new insight into the astaxanthin synthesis and antioxidant mechanisms in . 参考文献 相似文献 引证文献

Lavandula multifida response to salinity: Growth, nutrient uptake, and physiological changes

AbstractFern leaf lavender (Lavandula multifida L.) is a perennial shrub native to Almería with known medicinal properties, which grows in saline soils that are increasingly present in the Mediterranean region. However, the effects of salinity on the mineral nutrition and physiology of L. multifida are unknown. In the present study, we evaluated the salt resistance of this species and compared it with other members of the Lamiaceae. Plants of L. multifida were grown in pots in a mixture of sphagnum peat‐moss and Perlite, and treated with five different NaCl concentrations [10 (control), 30, 60, 100, and 200 mM NaCl] over a period of 60 d. The effects of different levels of salinity on mineral nutrient and osmolyte concentrations and on biomass were evaluated. Our results show that L. multifida plants were able to grow with 60 mM NaCl without significant biomass reduction. Na+ and Cl− were the main contributors to the osmotic potential in both roots and leaves, whereas total soluble sugars (TSS) and proline made only a small contribution. The concentrations of TSS and proline showed different trends in the different organs: in roots, both showed the highest concentrations at 60 mM NaCl, whereas in leaves TSS increased and proline decreased with increasing salt stress. To survive salinity, L. multifida plants increased salt excretion (Na+ and Cl−) by leaves at 100 and 200 mM NaCl and leaf succulence at 60, 100, and 200 mM NaCl. Excessive accumulation of Na+ and Cl− was avoided by shedding leaves. Our results indicate that L. multifida is better adapted to salinity compared to other members of the Lamiaceae¸ a consideration that is particularly relevant for their growth in arid saline areas.

Factors Affecting Seed Germination of Feather Fingergrass (Chloris virgata)

Laboratory experiments were carried out to determine the effect of several environmental factors on seed germination of feather fingergrass, one of the most significant emerging weeds in warm regions of the world. Seed germination occurred over a broad range of temperatures (17/7, 25/10, and 30/20 C), but germination being highest at alternating temperatures of 30/20 C under both 12 h light/12 h dark and 24 h dark conditions. Although seed germination was favored by light, some seeds were capable of germinating in the dark. Increasing salt stress decreased seed germination until complete inhibition was reached at 250-mM sodium chloride. Germination decreased from 64 to 0.7% as osmotic potential decreased from 0 to −0.4 MPa, and was completely inhibited at −0.6 MPa. Higher seed germination (> 73%) was observed in the range of pH 6.4 to 8 than the other tested pH levels. Heat shock had a significant effect on seed germination. Germination of seeds placed at 130 C for 5 min was completely inhibited for both dry and presoaked seeds. The results of this study will help to develop protocols for managing feather fingergrass, and to thus avoid its establishment as a troublesome weed in economically important cropping regions.

Inhibition of putrescine biosynthesis enhanced salt stress sensitivity and decreased spermidine content in rice seedlings

The effect of polyamine biosynthesis inhibitors on the salt stress response of rice seedlings was investigated. For this, DL-α-difluoromethylarginine (DFMA) and DL-α-difluoromethylornithine (DFMO), two competitive inhibitors of arginine decarboxylase (ADC) and ornithine decarboxylase (ODC), were used. The ADC and ODC are rate-limiting enzymes involved in synthesis of putrescine. The effective quantum yield of photosynthetic energy conversion (ΦPSII) decreased with the salt stress, and this decrease was highly significant in the treatments with DFMA and DFMO. Interestingly, addition of exogenous putrescine reduced the decline of ΦPSII. Putrescine content strongly decreased after one day of the inhibitor treatment. Although the content of spermidine (converted from putrescine) also showed an initial decrease in response to the inhibitors, it recovered to a similar level to that in the control after 3 d of treatment. Under the salt stress, the effect of the inhibitors on the different compounds was similar. Moreover, the addition of exogenous putrescine partially suppressed the decrease in spermidine and spermine content. A positive correlation between the spermidine and spermine content and the ΦPSII was observed. The results suggest that, under salt stress, a decrease in polyamine biosynthesis and/or polyamine content has a strong negative effect on leaves and increases salt stress sensitivity.

Influence of salicylic acid (SA) and ascorbic acid (ASA) on in vitro propagation and salt tolerance of date palm (Phoenix dactylifera L.) cv. ‘Nersy’

This study was carried out to investigate the antioxidant effects of salicylic acid (SA) and ascorbic acid (ASA) under two stress levels (75 and 150 mM NaCl) on growth and some biochemical constituents of date palm cv. Nersy cultured in vitro. Micro-propagated shoots of cv. Nersy at length 2.5-3 cm was excised from the proliferation medium and were separately cultured on MS medium. The data indicated that maximum growth and chlorophyll content of shoots was observed after 75 days of culturing in the medium supplemented with 50 mgl -1 salicylic acid and 100 mgl -1 ascorbic acid in both stress and non-stress conditions. It was also observed that the in vitro-grown plants resulted increased activities of antioxidant enzymes SOD and APX in medium containing of salicylic acid (75 mgl -1 ) and ascorbic acid (100 mgl -1 ) with increasing salt stress (up to 150 mM of NaCl) compared with other treatments. The study of shoot protein patterns using SDS-PAGE showed some remarkable changes in protein expression. The results suggests that the stress induced the synthesis of proteins bands with MW of 15, 29, 43 kD and 15, 22.6, 35 and 46 kD in medium supplement with 75 and 150 mM NaCl, respectively, compared with control treatment (20.9, 28.39, 37, 40 and 48.6) kD. Supplementing salicylic acid (75mgl -1 ) and ascorbic acid (100 mgl -1 ) under salt stress condition induced the synthesis of additional protein bands with MW of 19.28, 28.50, 32.61, 59.12 and 72.00 KD at 75 mM NaCl; and 17.96,22.6, 31.95 54.50 and 68.0 at 150 mM NaCl.

Overaccumulation of glycine betaine makes the function of the thylakoid membrane better in wheat under salt stress

Wheat (Triticum aestivum L.) lines T1, T4, and T6 were genetically modified to increase glycine betaine (GB) synthesis by introduction of the BADH (betaine aldehyde dehydrogenase, BADH) gene from mountain spinach (Atriplex hortensis L.). These transgenic lines and WT of wheat (T. aestivum L.) were used to study the effect of increased GB synthesis on wheat tolerance to salt stress. Salt stress due to 200mmolL−1 NaCl impaired the photosynthesis of the four wheat lines, as indicated by declines in net photosynthetic rate (Pn), stomatal conductance (Gs), maximum photochemical efficiency of PSII (Fv/Fm), and actual photochemical efficiency of PSII (ФPSII) and an increase in intercellular CO2 concentration (Ci). In comparison with WT, the effect of salinity on the three transgenic lines was mild. Salt stress caused disadvantageous changes in lipids and their fatty acid compositions in the thylakoid membrane of the transgenic lines and WT. Under salt stress, the three transgenic lines showed slightly higher chlorophyll and carotenoid contents and higher Hill reaction activities and Ca2+-ATPase activity than WT. All the results suggest that overaccumulation of GB resulting from introduction of the BADH gene can enhance the salt tolerance of transgenic plants, especially in the protection of the components and function of thylakoid membranes, thereby making photosynthesis better. Changes in lipids and fatty acid compositions in the thylakoid membrane may be involved in the increased salt stress tolerance of the transgenic lines.

MicroRNA and target gene responses to salt stress in grafted cucumber seedlings

Grafting is widely applied to enhance cucumber growth and tolerance to various biotic and abiotic adversities. Except for regulating plant growth and plant development, microRNAs (miRNAs) respond to various adversities through negative mediation of target gene expression at the post-transcriptional level. In the present study, cucumber (Cucumis sativus) scions were grafted onto pumpkin (Cucurbita moschata) rootstocks to characterize the molecular mechanisms of miRNAs and target regulatory networks that confer increased salt stress tolerance. The expression levels of 17 miRNAs and their predicted target genes were determined by quantitative real-time PCR using auto-grafted (self-grafted cucumber seedlings) and hetero-grafted (cucumber scion grafted onto pumpkin rootstock) cucumber seedlings after 24 h of 100 mmol l−1 NaCl treatment. Compared with that of auto-grafted cucumber seedlings, the expression level of most miRNAs in the leaves of hetero-grafted cucumber seedlings increased under normal conditions, decreased considerably after 2 h of salt stress, and increased after 6 and 24 h of salt stress. The expression level of most miRNAs in the roots of hetero-grafted cucumber seedlings increased under normal conditions and salt-stressed conditions. Compared with that of auto-grafted cucumber seedlings, the expression level of most target genes in the leaves of hetero-grafted cucumber seedlings decreased under normal and salt-stressed conditions. However, the expression level of most target genes in the roots of hetero-grafted cucumber seedlings increased significantly. These results provide useful information relevant to the functional analysis of miRNAs mediating graft-dependent salt tolerance.

Heterologous expression of ACC deaminase from Trichoderma asperellum improves the growth performance of Arabidopsis thaliana under normal and salt stress conditions

Transgenic Arabidopsis thaliana plants expressing the 1-aminocyclopropane-1-carboxylate deaminase gene (ACCD) of Trichoderma asperellum ACCC30536 (TaACCD) were created and their growth performance was assessed under normal and salt stress conditions. In order to characterize their growth, root length, root number, fresh weight (FW), relative water content (RWC), seed production, and seed number were measured. Under normal growing condition, all growth parameters except for dry weight (DW) of the transgenic plants increased significantly compared to WT plants. Furthermore, the transgenic line also exhibited higher tolerance and faster growth than WT plants in the presence of 150 mM NaCl. The increased salt stress tolerance of the transgenic plants is attributed to a greater RWC, root weight, root length, root number and FW under salt stress, and to reduced reactive oxygen species (ROS) level, cell death and electrolyte leakage compared to WT plants. The reduction in ROS levels could be explained by increased activity of several antioxidant enzymes, including peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT). Thus, we propose that heterologous expression of TaACCD could be used to improve salt stress tolerance in plants.

Adverse effect of urease on salt stress during seed germination in Arabidopsis thaliana

Seed germination is a critical stage in the development of crops that grow in saline soils. We noticed that seeds of an Arabidopsis urease mutant have significantly increased salt stress tolerance. To understand why, we treated the wild type (WT) with a urease inhibitor and found that its salt stress tolerance was also improved. We hypothesized that urease acting on urea generates NH4+, which probably exacerbates salt stress. As expected, the urease inhibitor significantly decreased the NH4+ level in WT seeds. These findings suggest that blocking urease activity improves salt tolerance during seed germination by lowering the concentration of NH4+.

Some nutritional characteristics and mineral contents in barley (Hordeum vulgare L.) seeds cultivated under salt stress

Barley (Hordeum vulgare L.) is an important food crop grown worldwide and it is important to investigate the quality of its grain as affected by various environmental conditions. In this study, barley was grown under increasing salt stress (0, 40, 80, and 120 mmol/l of NaCl) and the nutritional quality of its seeds was evaluated for their proximate composition, phenolic compounds and micro- and macro-mineral contents. Phenolic compounds of barley seeds increased significantly from 1.75 (control) to 1.95 mg gallic acid equivalent/g dry weight of barley seed in 120 mmol/l NaCl. Cu, Mg, and Ni contents were decreased whereas Fe, Mo, and Zn contents were increased significantly by increasing salinity. Among the macro-minerals in barley seeds cultivated under salt stress only K contents increased whereas Ca, Mg, P, and S contents were decreased significantly.