Adverse Effects Of Salt Stress Research Articles

Does jasmonic acid mitigate the adverse effects of salt stress on wheat through the enhancement of ascorbate biosynthesis and the induction of glutamate dehydrogenase activity?

AbstractBackgroundSalt stress is one of the most common abiotic stresses, reducing plant growth and productivity. Thus, the development of suitable management practices to minimize the deleterious effects of salt stress has become necessary.AimsThis study was conducted to investigate the possible mechanisms underlying salt tolerance conferred by jasmonic acid (JA).MethodsSalt‐stressed wheat seedlings were supplemented with 1 mM JA and/or 1 mM ibuprofen (IBU), an inhibitor of endogenous JA biosynthesis, in the culture medium.ResultsThe obtained results showed that salt stress significantly decreased shoot and root dry weight production and relative water contents. This was associated with a noteworthy reduction in leaf and root ascorbate (AsA) concentrations, as well as glutamine synthetase (GS), glutamate synthase (GOGAT), and glutamate dehydrogenase (GDH) activities. Exogenously supplied JA did not affect GS and GOGAT activities in leaves and roots of salt‐treated seedlings. However, noticeable enhancements were observed in growth, AsA concentrations, as well as GDH activities. Likewise, the inhibition of JA biosynthesis by IBU application was accompanied by a significant decrease in seedlings’ growth associated with a noticeable reduction in AsA concentrations and GDH activities. The decreases in growth and GDH activities were also obtained following inhibition of AsA biosynthesis by lycorine (Lyc) application. By contrast, increased GDH activities and enhanced growth were obtained following exogenous AsA supplementation, with or without JA biosynthesis inhibition.ConclusionsThe findings implied that exogenous JA enhanced AsA biosynthesis and induced GDH activity, which further promoted the growth of wheat seedlings in salt‐stressed conditions. Therefore, the stimulation of AsA biosynthesis and GDH activity through JA application in the rhizosphere may be suggested as a vital strategy for strengthening the salt tolerance of wheat plants, at least at the seedling stage.

Effect of polyamine precursors and antioxidants on growth and metabolism of salt-stressed barley

Background Salt stress, a significant environmental problem was studied in barley cultivars Giza 124 and Giza 119 at various stages (seedling, pre-flowering, and yield). This study aimed to investigate the impact of salt stress on these cultivars, examine the effects of polyamine precursors (arginine, methionine, and ornithine) on their response to salt stress, and assess the efficacy of antioxidants (glutathione and ascorbic acid) in alleviating the harmful effects of salt stress on barley plants. Methods Barley grains were germinated and subjected to salinity stress, with subsequent treatment using glutathione, ascorbic acid, or an amino acid mixture. Growth criteria, photosynthetic pigments, metabolites, antioxidant enzymes, mineral content, and polyamines were analyzed. Results The impact of 100Mm NaCl, with or without glutathione, ascorbic acid, or amino acid mixtures, on various physiological parameters in G124 and G119 were investigated. The levels of chlorophyll a, chlorophyll b, and carotenoids significantly varied under different treatments. For instance, chlorophyll a in G 124 exhibited a 23% reduction under salt stress compared to the control, while the addition of glutathione mitigated this effect, resulting in a 17% increase compared to the NaCl treatment. Similar trends were observed for chlorophyll b and carotenoids. At the yield stage, both cultivars demonstrated a significant decrease in the the weight of grains per plant under salinity, which was alleviated by the addition of ascorbic acid, glutathione, or amino acid mixtures. Conclusion The application of glutathione, ascorbic acid, or an amino acid mixture mitigated the adverse effects of salt stress on various parameters. The results highlight the potentail of these compounds in enhancing plant tolerance to salinity stress and offer insights into the physiological response of barley cultivars under adverse conditions.

ZnO quantum dots alleviate salt stress in Salvia miltiorrhiza by enhancing growth, scavenging reactive oxygen species, and modulating stress-responsive genes

Experiments were conducted to investigate the alleviating effects of ZnO quantum dots (ZnO QDs) on salt stress in Salvia miltiorrhiza by comparing them with conventional ZnO nanoparticles (ZnO NPs). The results demonstrated that compared with salt stress alone, foliar application of ZnO QDs significantly improved the biomass as well as the total chlorophyll and carotenoids contents under salt stress. ZnO QDs reduced H2O2 and MDA levels, decreased non-enzymatic antioxidant (ASA and GSH) content, and improved antioxidant enzyme (POD, SOD, CAT, PAL, and PPO) activity under salt stress. Metal elemental analysis further demonstrated that the ZnO QDs markedly increased Zn and K contents while decreasing Na content, resulting in a lower Na/K ratio compared to salt stress alone. Finally, RNA sequencing results indicated that ZnO QDs primarily regulated genes associated with stress-responsive pathways, including plant hormone signal transduction, the MAPK signaling pathway, and metabolic-related pathways, thereby alleviating the adverse effects of salt stress. In comparison, ZnO NPs did not exhibit similar effects in terms of improving plant growth, enhancing the antioxidant system, or regulating stress-responsive genes under salt stress. These findings highlight the distinct advantages of ZnO QDs and suggest their potential as a valuable tool for mitigating salt stress in plants.

Metabolic Adaptations in Rapeseed: Hemin-Induced Resilience to NaCl Stress by Enhancing Growth, Photosynthesis, and Cellular Defense Ability.

This study aimed to investigate whether presoaking with hemin (5 μmol·L-1) could alleviate NaCl stress during rapeseed seedlings' growth and its role in the regulation of photosynthesis. In this experiment, 'HUAYOUZA 62 (HYZ 62)' and 'HUAYOUZA 158R (158R)' were used as materials for pot experiments to study the morphology, photosynthetic characteristics, antioxidant activity, and osmoregulatory factors of seedlings under different salt concentrations, as well as the regulatory effects of hemin-presoaked seeds. Our findings revealed that, compared the control, NaCl stress inhibited the growth of two rapeseed varieties, decreased the seedling emergence rate, and increased the content of malondialdehyde (MDA), the electrolyte leakage rate (EL) and antioxidant enzyme activity. Hemin soaking alleviated the adverse effects of salt stress and increased plant height, root elongation and dry matter accumulation. Compared with all NaCl treatments, hemin significantly enhanced photosynthetic indexes, including a percent increase of 12.99-24.36% and 5.39-16.52% in net photosynthetic rate (Pn), 17.86-48.08% and 8.6-23.44% in stomatal conductivity (Gs), and 15.42-37.94% and 11.09-19.08% in transpiration rate (Tr) for HYZ62 and 158R, respectively. Moreover, hemin soaking also increased antioxidant enzyme activities, including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX), reducing the malondialdehyde, and thus resulting in the alleviation of oxidative damage caused by NaCl stress. Furthermore, hemin stimulated the formation of soluble protein, which effectively regulated the osmo-protective qualities. The current findings strongly elucidate that hemin soaking could effectively alleviate the negative impacts of NaCl stress by regulating the morphological, photosynthetic, and antioxidant traits. This study provides a new idea regarding the effect of Hemin on the salt tolerance of rapeseed, and provides a basis for the practical application of Hemin in saline-alkali soil to improve the salt tolerance of cultivated rapeseed.

Low apoplastic Na+ and intracellular ionic homeostasis confer salinity tolerance upon Ca2SiO4 chemigation in Zea mays L. under salt stress.

Salinity is known to have a greater impact on shoot growth than root growth. Na+ buildup in plant tissue under salt stress has been proposed as one of the main issues that causes growth inhibition in crops via ionic imbalances, osmotic stress and pH disturbances. However, the evidence for apoplastic Na+ buildup and the role of silicon in Na+ accumulation at the subcellular level is still enigmatic. The current study focuses on the accumulation of Na+ in the apoplast and symplast of younger and older leaves of two maize varieties (Iqbal as salt-tolerant and Jalal as salt-sensitive) using hydroponic culture along with silicon supplementation under short-term salinity stress. Subcellular ion analysis indicated that silicon nutrition decreased Na+ concentration in both apoplastic washing fluid and symplastic fluid of maize under salt stress. The addition of silicon under NaCl treatment resulted in considerable improvement in fresh biomass, relative water content, chlorophyll content, and concentration of important subcellular ions (i.e., Ca2+, Mg2+, and K+). Knowledge of subcellular ion analysis is essential for solving the mechanisms underlying vital cellular functions e.g. in the current study, the soluble Na+ concentration in the apoplast of older leaves was found to be significantly greater (36.1 mM) in the salt-sensitive variety under NaCl treatment, which was 42.4% higher when compared to the Na+ concentration in the salt-tolerant variety under the same treatment which can influence permeability of cell membrane, signal transduction pathways and provides insights into how ion compartmentalization can contributes to salt tolerance. Calcium silicate enrichment can contribute to increased growth and improved ionic homeostasis by minimizing leaf electrolyte leakage, improving mechanical functions of cell wall and reducing water loss, and improved photosynthetic function. In current investigation, increased water content and intracellular ionic homeostasis along with reduced concentration of Na+ in the maize leaf apoplast suggest that calcium silicate can be used to ameliorate the adverse effects of salt stress and obtain yield using marginal saline lands.

Salinity-responsive key endophytic bacteria in the propagules of Kandelia obovata enhance salt tolerance in rice

Salinity is a major environmental stress affecting crop growth and productivity globally. The application of halo-tolerant plant growth-promoting bacteria (HT-PGPB) has been widely recognized to promote crop growth and reduce the adverse effects of salt stress. Herein, key endophytic bacteria that can respond to salinity changes were identified by analysis of the microbial community in propagules of Kandelia obovate. Delftia tsuruhatensis DYX29, a strain able to grow normally under high salinity conditions with a sodium chloride (NaCl) concentration of 5% (w/v), was obtained by pure culture. DYX29 has the ability to produce siderophores with a siderophore unit value of 87.6% and ACC (1-aminocyclopropane-1-carboxylate) deaminase with 29 U L-1 and can synthesize intracellular amino acids and auxin induced by high salinity. Inoculation with DYX29 can remarkably promote the salt tolerance of rice. Under salt stress, the addition of DYX29 effectively promoted the growth of rice seedlings through a variety of approaches. It increased the biomass of rice seedlings by 32.9% (dry weight) and promoted the accumulation of soluble sugars by 23.1%. It also increased CAT and POD activities in rice leaves by 37.8 and 88.2%, respectively. Moreover, it maintained ionic homeostasis in roots and leaves. In addition, it upregulated the expression of growth-promoting hormones in roots, such as IAA, BL, ABA and SA, in rice roots by 27.8, 69.5, 123.7 and 28.6%, respectively. This study provides inspiration for screening valuable salt-tolerant pro-biotic bacteria from mangrove ecosystems for crop growth promotion under salt stress. It may also provide useful references for the development of new salt-tolerant and pro-biotic biofertilizers and the investigation of the related mechanism.

β-Aminobutyric acid enhances salt tolerance of African marigold by increasing accumulation rate of salicylic acid, γ-Aminobutyric acid and proline

African marigold (Tagetes erecta L.) is one of most cultivated warm-season flowers which is used as cut flower, potted flower or margin flower. Nowadays, one of the most common issues of landscaping is sensitivity of ornamental plants to salinity of soil or irrigation water. In order to investigate the role of β-Aminobutyric acid (BABA) treatments in alleviation of adverse effects of salt stress on African marigold, a factorial experiment was conducted based on completely randomized design with 3 replications during 2022–2023. The experimental treatments included different concentrations of BABA (0, 4, 8 and 12 mM) and different levels of salinity (0, 50, 100 and 150 mM NaCl). Results demonstrated that the negative effects of salinity on marigold characteristics increased by increasing the salinity level, but BABA treatments effectively alleviated the adverse effects. Fresh and dry weight of shoots and root, leaf relative water content, total chlorophyll and carotenoid content, the activity rate of phenylalanine ammonia lyase, catalase and superoxide dismutase, and the accumulation rate of salicylic acid, γ-Aminobutyric acid (GABA) and proline were significantly increased by treatment of marigold plants with BABA 8 mM. Also, this treatment maintained plant phenol and protein content, and reduced H2O2 content, malondialdehyde content and electrolyte leakage under salinity conditions. Accumulation of salicylic acid, GABA and proline caused by BABA treatment could probably be one of most important mechanisms of enhancing salt tolerance rate of marigold plants in this study, therefore, it is recommended to use this treatment as innovative and efficient technique to overcome salinity effects on African marigold plants.

Exogenous γ-Aminobutyric Acid Can Improve Seed Germination and Seedling Growth of Two Cotton Cultivars under Salt Stress.

Excessive salt content in soil has adverse effects on cotton production, especially during the germination and seedling stages. γ-aminobutyric acid (GABA) is an important active substance that is expected to improve the resistance of plants to abiotic stresses. This study focused on two cotton cultivars (Gossypium hirsutum L.: Tahe 2 and Xinluzhong 62) and investigated the impact of exogenous GABA (0, 1, 2, 3, and 4 mM) on seed germination, seedling growth, and related morphological, physiological, and biochemical indicators under salt stress (150 mM NaCl). The results showed that salt stress significantly reduced the germination rate and germination index of cotton seeds (decreased by 20.34% and 32.14% for Tahe 2 and Xinluzhong 62, respectively), leading to decreased seedling height and biomass and causing leaf yellowing. Salt stress induced osmotic stress in seedlings, resulting in ion imbalance (marked reduction in K+/Na+ ratio) and oxidative damage. Under salt stress conditions, exogenous GABA increased the germination rate (increased by 10.64~23.40% and 2.63~31.58% for Tahe 2 and Xinluzhong 62, respectively) and germination index of cotton seeds, as well as plant height and biomass. GABA treatment improved leaf yellowing. Exogenous GABA treatment increased the content of proline and soluble sugars, with varying effects on betaine. Exogenous GABA treatment reduced the Na+ content in seedlings, increased the K+ content, and increased the K+/Na+ ratio (increased by 20.44~28.08% and 29.54~76.33% for Tahe 2 and Xinluzhong 62, respectively). Exogenous GABA treatment enhanced the activities of superoxide dismutase and peroxidase, and reduced the accumulation of hydrogen peroxide and malondialdehyde, but had a negative impact on catalase activity. In conclusion, exogenous GABA effectively improved cotton seed germination. By regulating osmoprotectant levels, maintaining ion homeostasis, and alleviating oxidative stress, GABA mitigated the adverse effects of salt stress on cotton seedling growth.

Effect of copper oxide and zinc oxide nanoparticles on photosynthesis and physiology of Raphanus sativus L. under salinity stress

The study evaluates the impact of two metal oxide nanoparticles: copper oxide (CuO) and zinc oxide (ZnO) on the growth and physiology of Raphanus sativus L. (radish) under salinity stress. Fifteen days old seedlings of R. sativus were subjected to different concentrations of salt stress (0 mM, 150 mM, and 300 mM NaCl) alone and in interaction with 100 mgL−1 metal oxide nanoparticle treatments (CuO and ZnO NPs via foliar spray) for 15 days. The results confirmed the severe effects of salinity stress on the growth and physiology of radish plants by decreasing nutrient uptake, leaf area, and photosystems photochemistry and by increasing proline accumulation, anthocyanin, flavonoids content, and antioxidant enzyme activities which is directly linked to increased oxidative stress. The foliar application of CuO and ZnO NPs alleviated the adverse effects of salt stress on radish plants, as indicated by improving these attributes. Foliar spray of ZnO NPs was found efficient in improving the leaf area, photosynthetic electron transport rate, the PSII quantum yield, proton conductance and mineral content in radish plants under NaCl stress. Besides, ZnO NPs decreased the NaCl-induced oxidative stress by declining proline, anthocyanin, and flavonoids contents and enzymatic activities such as superoxide dismutase (SOD), ascorbate peroxidase (APX) and guaiacol peroxidase (GOPX). Thus, our study revealed that ZnO NPs are more effective and have beneficial effects over CuO NPs in promoting growth and reducing the adverse effects of NaCl stress in radish plants.

Using Bacillus megaterium as a bio-fertilizer alleviates salt stress, improves phosphorus nutrition, and increases cauliflower yield

The traditional crop production system involves the use of large amounts of chemical fertilizers, which negatively impacts the ecological environment by increasing soil degradation and salinity, threatening sustainable agricultural production. Therefore, there is an urgent need for agricultural practices that increase plant productivity and reduce negative impacts on the environment. Phosphate-solubilizing microorganisms can enhance nutrient availability and plant uptake. This study investigated the effect of Bacillus megaterium as a bio-fertilizer (inoculated and non-inoculated) combined with phosphorus fertilizer (40, 60, and 80 kg. ha−1) on the growth and yield of cauliflower grown under saline conditions, saline soil (9.68 dS.m−1) and saline irrigation water (7.12 dS.m−1). Salt-stressed cauliflower inoculated with Bacillus and fertilized with 60 or 80 kg. ha−1 P2O5 showed improved growth and higher yield compared to other treatments, without significant differences between them. However, Bacillus-treated plants fertilized with 60 P2O5 showed increases in superoxide dismutase (SOD) by 29.3%, catalase (CAT) by 13.9, chlorophyll by 10.4%, N by 7.8%, and P by 8.6%, while Na decreased by 7.8%, resulting in significant increases in cauliflower yield (head weight by 9.3%, and total yield by 8.3%) compared with the control treatment (recommended P fertilizer, 80 kg P2O5. ha−1). The results indicated that the inoculation of salt-stressed plants with Bacillus megaterium is a promising and feasible approach to reduce phosphorus fertilizer use by up to 25% and enhance membrane stability (MSI), relative water content (RWC), nutrient availability, and growth performance, thus mitigating the adverse effects of salt stress exacerbated by climate change.

Reactive oxygen species (ROS) scavenging and methylglyoxal (MG) detoxification confers salinity tolerance in mustard cultivars inoculated with Piriformospora (Serendipita) indica

Salinization has become a major concern for the growth and development of plants, resulting in significant crop losses. Beneficial microbial symbionts are utilized as promising tools in alleviation of adverse effects of salt stress. Piriformospora (Serendipita) indica is one of the cost-effective, eco-friendly, and stress relieving biostimulant that positively regulates the growth of a broad host range of plants. The present study was to investigate the impact of P. indica on Indian mustard (Brassica juncea L.) cultivars (Pusa Jaikisan and Pusa Bold) under different levels of salinity stress (0, 50, 100, 150, 200 and 300 mM NaCl) by analyzing morphological, physiological and biochemical attributes. Results revealed that the plant biomass, chlorophyll content, and relative water content were reduced and Na+ and Cl‒ ions uptake increased with increasing NaCl concentrations. The maximum reduction in the measured traits was observed at 300 mM NaCl in both cultivars [tolerant (Pusa Jaikisan) and sensitive (Pusa Bold)]. Additionally, the oxidative stress markers (TBARS, MG, H2O2, and EL) accumulation were increased with increasing salt concentrations. However, P. indica colonization enhanced the plant performance by improving the biomass, chlorophyll, and water content, and reduced levels of oxidative stress markers (TBARS, MG, H2O2, and EL) in both cultivars comparatively more in Pusa Jaikisan than Pusa Bold under salinity stress. Additionally, the maximum activities of methyl glyoxal detoxifying enzymes (Gly I & Gly II) along with the components of ROS scavenging machinery (SOD, APX, GPX, GR, AsA, and GSH) in the P. indica colonized plants conferred salt tolerance in comparison to non-colonized cultivars under salinity stress. The results indicate that P. indica promotes the growth and tolerance of mustard plants under salinity stress, thus providing opportunity for further assessment in terms of use in sustainable agriculture.

Moringa leaf extract increases tolerance to salt stress, promotes growth, increases yield, and reduces nitrate concentration in lettuce plants

The use of large amounts of synthetic chemicals in plant cultivation harms the environment and reduces food quality. Therefore, natural alternatives should be used to protect the environment, increase food quality, and decrease food contamination. This study investigated the effect of moringa leaf extract (MLE) as a plant stimulator to enhance growth, yield, and quality of lettuce grown in a saline environment. To examine the effect of application method and extract concentration, this experiment included three levels of seed priming (0, 5 %, and 10 % MLE) and three levels of foliar spray (0, 5 %, and 10 % MLE). MLE application, either by seed priming or foliar spraying, reduced the adverse effects of salt stress and increased lettuce growth, yield, and quality. However, the combined treatment of 5 % seed soaking and 10 % foliar spray showed the best results in increasing antioxidant levels (catalase (CAT), ascorbate peroxidase (APX), and ascorbic acid), relative water content (RWC %), nutrient concentration (N, P, and K), and chlorophyll content, and maintaining membrane integrity by reducing electrolyte leakage (EL %) and sodium accumulation, leading to improved yield parameters (head diameter, head weight, and total yield), and increasing lettuce head quality by reducing nitrate concentration. The results suggest that MLE (5 % seed soaking and 10 % foliar spray) is a practical, effective, and inexpensive approach to alleviate salt stress and improve lettuce yield and quality under saline conditions. However, despite the observed positive effects, further studies are needed to understand the factors determining the response of plants to MLE application.

Potassium and Brackish Water Irrigation Influence Electrical Conductivity, Potassium Dynamic, and Maize Yield in Coastal Saline Soil

ABSTRACT Brackish water irrigation builds up salinity in the root zone of crops resulting in osmotic stress, nutritional imbalance, and specific ion effect. The development of agro-technology to ameliorate the adverse effects of salt stress has received considerable attention. In this pot culture experiment, we used two types of irrigation water (SW0- normal water, EC- 0.5 dS m−1 and SW1-brackish water, EC- 4 dS m−1), two sources of potassium (K) fertilizers (F1-KCl and F2-K2SO4) and three doses of K (K1–0, K2–30, K3–60 mg kg−1) to study the effect of brackish water irrigation and K on soil saturated paste electrical conductivity (ECe), K dynamic and maize biomass yield in saline soil. The ECe in SW1 was increased significantly (P < .001) by 182% over SW0 but decreased with K application. The SW1 treatment significantly increased the release of non-exch.K by 27% over SW0 at 21 DASE (the day after seedling emergence). The addition of K3 significantly increased the water-soluble K (ws.K), exchangeable K (exch.K) and non-exch.K by 54, 93, and 9%, respectively over K1. The SW1K3 treatment significantly reduced ECe and increased maize biomass yield (24%) over SW1K1. The outcome of the study suggested that SW1 with K3 supports maize production in saline soil during winter.

Impacts of plant growth-promoting bacteria, compost and biodynamic compost preparations for alleviating the harmful effects of salinity on essential oil characteristics of lavender

BackgroundBiodynamic agriculture and the use of plant growth-promoting bacteria (PGPBs) have been demonstrated to offer various benefits for achieving agricultural sustainability. The aim of this study was to evaluate the effects of PGPBs Azotobacter and Azospirillum, compost, and compost with biodynamic preparations (BD) on the essential oil (EO) characteristics of lavender under salinity stress.Research methodsThe experiment was carried out in a greenhouse for 2 years and involved three factors: four PGPBs, three types of compost, and three levels of salinity stress.ResultsThe results indicated that the essential oil (EO) characteristics increased with 50 mM NaCl but decreased with 100 mM NaCl. Salt stress reduced the cell membrane stability (CMS) and auxin content, while increasing proline contents. However, the application of PGPBs, compost, and compost with biodynamic preparations had an opposite effect on CMS, auxin, and proline parameters compared to salt stress. Based on the results, the treatment that combined compost + BD with Azotobacter was found to be the most effective in enhancing the EO characteristics under both mild and severe salinity stress conditions.ConclusionsThe results of this study suggest that compost, biodynamic compost preparations, and PGPBs could be useful in enhancing the EO in medicinal plants and alleviating the adverse effects of salt stress on plants.Graphical

Silicon application mitigated the adverse effects of salt stress and deficit irrigation on drip-irrigated greenhouse tomato

Tomato (Solanum lycopersicum L.) is an important vegetable crop around the world, and water scarcity and soil salinization are two major unfavorable factors limiting the fruit yield and quality of greenhouse tomato in arid and semi-arid regions. The application of exogenous silicon has been reported to enhance tomato yield under salt or drought stress, but its effect under combined salt-drought stress remains unclear. A two-season (autumn 2021 and spring 2022) experiment was conducted with three irrigation levels (I1, 90%−100% θf, where θf is the field capacity; I2, 70%−80% θf; I3, 50%−60% θf), two soil salinity levels (S0, 0.1%, g/g; S1, 0.4%, g/g) and two silicon application rates (T0, 0 mM; T1, 2.4 mM) to explore their combined effects on leaf silicon content, photosynthetic parameters, fruit yield, nutrient yield, crop water productivity (WP), nitrogen uptake and utilization, nutrient water productivity (NWP) and economic benefit of drip-irrigated greenhouse tomato. The results showed that deficit irrigation and salt stress exerted significant inhibiting effects on leaf silicon content, photosynthetic parameters, tomato yield, and water-nitrogen productivity, but the inhibition was alleviated by silicon application, which increased leaf silicon content by 67.0%, net photosynthetic rate (Pn) by 25.3%, fruit yield by 12.3%, WP by 11.9%, nutrient yield by 10.0% (titratable acids) - 27.4% (soluble sugars) and NWP by 9.2% (titratable acids) - 26.1% (soluble sugars) on average. The average fruit yield over the two growing seasons was 66.01, 54.29 and 44.31 t ha−1 under I1, I2 and I3, and the silicon application increased average leaf silicon content by 71.9%, 65.2% and 63.0%, Pn by 11.1%, 12.9% and 7.6%, and fruit yield by 12.8%, 16.2%, and 8.1% at the three irrigation levels, respectively. Plant nitrogen uptake (NU) and nitrogen partial factor productivity (NPFP) increased but nitrogen use efficiency (NUE) tended to decrease with the increasing irrigation level, while silicon application improved NUE by 3.9% and 2.2% and NPFP by 13.8% and 11.7% in the two growing seasons, respectively. Silicon application significantly increased net profit by 24.3% and 17.7% in autumn 2021 and spring 2022, respectively. According to the principal component analysis, I1T1S0 ranked first in both growing seasons. The correlation matrix showed that fruit yield was positively correlated with leaf silicon content, Pn, stomatal conductance, WP, NU, NUE, NPFP, nutrient yield and net profit, while it had negative correlation with NWP. In conclusion, exogenous silicon application can improve the fruit yield and nutrient yield of drip-irrigated greenhouse tomato by enhancing leaf silicon content and photosynthetic capability under drought-stressed and salt-affected conditions.

Nitrate reductase regulation in wheat seedlings by exogenous nitrate: A possible role in tolerance to salt stress

AbstractBackgroundSoil salinity is a major abiotic stress causing severe damage to plants. Thus, proper management approaches need to be developed to lessen the detrimental effect of salinity on crop growth and productivity.AimsThis study was conducted to investigate the putative role of nitrate (NO3−) and nitrate reductase (NR) in mitigating the adverse effects of salt stress on the growth of durum wheat seedlings.MethodsNitrogen nutrition has been modified, in the presence of 100 mM NaCl, either by increasing the NO3− availability, the deprivation of NO3− or by the addition of sodium tungstate—an inhibitor of NR—in the culture medium.ResultsObtained results showed that, in the presence of 2.5 mM NO3−, salt stress significantly decreased all studied growth traits (biomass production, relative growth rate, and water content). This was associated with a noteworthy reduction in total chlorophyll pigment, total carbohydrates, and protein contents. Concomitantly, NR activity was remarkably decreased. However, proline and malondialdehyde (MDA) were significantly accumulated. In the absence of NO3− as well as in the presence of tungstate, NR activities were noticeably reduced, and wheat seedling growth was further disturbed in comparison to salt‐stressed seedlings grown under 2.5 mM NO3−. Increasing the NO3− availability to 7.5 mM significantly restricted Cl− uptake, markedly increased root and leaf NR activities, and alleviated salt stress–induced seedling growth inhibition as compared to salt‐stressed seedlings grown under 2.5 mM NO3−. Such effects were associated with an increase in leaf chlorophyll and protein concentrations and in root and leaf carbohydrate concentrations. Nevertheless, MDA concentrations were sharply decreased.ConclusionsThis study provides strong arguments highlighting the potential role of NO3− reduction in mitigating the adverse effects of salt stress on the growth of wheat plants at the early seedling stage. The enhancement of the NR activity through increasing the NO3− availability may, therefore, represent a potential strategy to overcome the salinity‐mediated impairment of wheat seedlings to some extent.

Vermicompost Improves Tomato Yield and Quality by Promoting Carbohydrate Transport to Fruit under Salt Stress

To explore the effect of vermicompost on the yield and quality of tomato cultivated in salty soil, we investigated the soil chemical properties, the yield, vitamin C, organic acid, soluble solids, and nitrate of fruit, photosynthesis, and carbohydrates of plants grown under various salt levels applied with the application of either commercial chemical fertilizers, cow manure, or vermicompost. Results showed that the tomato yield was not increased from the chemical fertilizer application, while there was an increase from the cow manure and vermicompost (increased 31.7% and 65.2%, respectively) under salt stress. Compared to no salt stress, the contents of vitamin C, organic acid, soluble solids, and nitrate increased 26.55%, 40.59%, 46.31%, and 35.08%, respectively, under salt stress (2 g NaCl·kg−1 soil). Compared with the Control, the application of chemical fertilizers failed to improve the sugar/acid ratio but increased nitrate content, while cow manure and vermicompost improved the sugar/acid ratio by 42.0% and 73.1%, respectively. Particularly, vermicompost increased vitamin C and reduced nitrate to the greatest extent among the different fertilizer treatments. The decrease in sodium (Na+) in the roots and leaves, increase in carbohydrates in fruit, and photosynthetic efficiency of leaves imply an amendment effect of vermicompost on salt stress. Moreover, vermicompost also facilitated the transit of carbohydrates from leaves to fruits by increasing the accumulation of nitrogen, phosphate, and potassium in fruits, leaves, and roots, while decreasing proline and soluble protein accumulation in leaves and roots. In conclusion, vermicompost could alleviate the adverse effect of salt stress and improve tomato yield and fruit quality by improving the photosynthetic capacity and promoting carbohydrate transport to fruit. The findings give a new perspective on the beneficial effect of vermicompost on tomato yield and quality.

Comparative transcriptomic profiling reveals differentially expressed genes and important related metabolic pathways in shoots and roots of a Saudi wheat cultivar (Najran) under salinity stress.

High salinity of soil is a threatening constraint for agricultural output worldwide. The adverse effects of salt stress on plants can be revealed in different manners, from phenotypic to genetic changes. A comparative RNA-Sequencing analysis was done in roots and shoots of bread wheat, Najran cultivar between plants grown under unstressed control condition (0 mM NaCl) and salt treatment (200 mM NaCl). More than 135 million and 137 million pair-end reads were obtained from root and shoot samples, respectively. Of which, the mapped reads to Triticum aestivum genome IWGSC_V51 ranged from 83.9% to 85% in the root and 71.6% to 79% in the shoot. Interestingly, a comparison of transcriptomic profiling identified that total number of significantly differentially expressed genes (DEGs) examined in the roots was much higher than that found in the shoots under NaCl treatment, 5829 genes were differentially expressed in the roots whereas 3495 genes in the shoots. The salt-induced change in the transcriptome was confirmed by RT-qPCR using a set of randomly selected genes. KEGG enrichment analysis classified all DEGs in both roots and shoots into 25 enriched KEGG pathways from three main KEGG classes: Metabolism, organismal systems and genetic information processing. According to that, the most significantly regulated pathways in the root and shoot tissues were glutathione metabolism and biosynthesis of secondary metabolites such as phenylpropanoids and galactose metabolism suggesting that these pathways might participate in wheat salt tolerance. The findings highlight the importance of the control of oxidative stress via Glutathione and phenylpropanoids and the regulation of galactose metabolism in the roots and shoots for salt-tolerance in wheat. They open promising prospects for engineering salt-tolerance in this important crop via targeted improvement of the regulation of key genes in the production of these compounds.

Salt stress responses and alleviation strategies in legumes: a review of the current knowledge.

Salinity is one of the most significant environmental factors limiting legumes development and productivity. Salt stress disturbs all developmental stages of legumes and affects their hormonal regulation, photosynthesis and biological nitrogen fixation, causing nutritional imbalance, plant growth inhibition and yield losses. At the molecular level, salt stress exposure involves large number of factors that are implicated in stress perception, transduction, and regulation of salt responsive genes' expression through the intervention of transcription factors. Along with the complex gene network, epigenetic regulation mediated by non-coding RNAs, and DNA methylation events are also involved in legumes' response to salinity. Different alleviation strategies can increase salt tolerance in legume plants. The most promising ones are Plant Growth Promoting Rhizobia, Arbuscular Mycorrhizal Fungi, seed and plant's priming. Genetic manipulation offers an effective approach for improving salt tolerance. In this review, we present a detailed overview of the adverse effect of salt stress on legumes and their molecular responses. We also provide an overview of various ameliorative strategies that have been implemented to mitigate/overcome the harmful effects of salt stress on legumes.

Diversity and potential plant growth promoting capacity of seed endophytic bacteria of the holoparasite Cistanche phelypaea (Orobanchaceae)

Salt marshes are highly dynamic, biologically diverse ecosystems with a broad range of ecological functions. We investigated the endophytic bacterial community of surface sterilized seeds of the holoparasitic Cistanche phelypaea growing in coastal salt marshes of the Iberian Peninsula in Portugal. C. phelypaea is the only representative of the genus Cistanche that was reported in such habitat. Using high-throughput sequencing methods, 23 bacterial phyla and 263 different OTUs on genus level were found. Bacterial strains belonging to phyla Proteobacteria and Actinobacteriota were dominating. Also some newly classified or undiscovered bacterial phyla, unclassified and unexplored taxonomic groups, symbiotic Archaea groups inhabited the C. phelypaea seeds. γ-Proteobacteria was the most diverse phylogenetic group. Sixty-three bacterial strains belonging to Bacilli, Actinomycetes, α-, γ- and β-Proteobacteria and unclassified bacteria were isolated. We also investigated the in vitro PGP traits and salt tolerance of the isolates. Among the Actinobacteria, Micromonospora spp. showed the most promising endophytes in the seeds. Taken together, the results indicated that the seeds were inhabited by halotolerant bacterial strains that may play a role in mitigating the adverse effects of salt stress on the host plant. In future research, these bacteria should be assessed as potential sources of novel and unique bioactive compounds or as novel bacterial species.