NaCl-induced Salt Stress Research Articles

Interventional Effect of Zinc Oxide Nanoparticles with Zea mays L. Plants When Compensating Irrigation Using Saline Water.

High salinity reduces agriculture production and quality, negatively affecting the global economy. Zinc oxide nanoparticles (ZnO-NPs) enhance plant metabolism and abiotic stress tolerance. This study investigated the effects of 2 g/L foliar Zinc oxide NPs on Zea mays L. plants to ameliorate 150 mM NaCl-induced salt stress. After precipitation, ZnO-NPs were examined by UV-visible spectroscopy, transmission electron microscopy, scanning transmission electron microscopy, energy dispersive X-ray, and particle size distribution. This study examined plant height, stem diameter (width), area of leaves, chlorophyll levels, hydrolyzable sugars, free amino acids, protein, proline, hydrogen peroxide, and malondialdehyde. Gas chromatographic analysis quantified long-chain fatty acids, and following harvest, leaves, stalks, cobs, seeds, and seeds per row were weighed. The leaves' acid and neutral detergent fibers were measured along with the seeds' starch, fat, and protein. Plant growth and chlorophyll concentration decreased under salt stress. All treatments showed significant changes in maize plant growth and development after applying zinc oxide NPs. ZnO-NPs increased chlorophyll and lowered stress. ZnO-NPs enhanced the ability of maize plants to withstand the adverse conditions of saline soils or low-quality irrigation water. This field study investigated the effect of zinc oxide nanoparticles on maize plant leaves when saline water is utilized for growth season water. This study also examined how this foliar treatment affected plant biochemistry, morphology, fatty acid synthesis, and crop production when NaCl is present and when it is not.

NaCl Kaynaklı Tuz Stresinin Lotus corniculatus L. cv. 'Leo'nun Çimlenmesi ve İlk Fide Büyümesi Üzerindeki Etkisi

Lotus corniculatus L. is one of the agronomically and economically important perennial legume forage species with moderately salt-tolerant. It is well known that even the cultivars of the same species in plants have different responses in salinity. However, studies on the salt response of L. corniculatus and its cultivars, which are more advantageous than other forage crops such as white clover (Trifolium repens) and alfalfa (Medicago sativa L.), in the use of marginal agricultural lands affected by abiotic stress factors such as salinity, are limited. Under salt stress, the most crucial phases of the plant life cycle that are directly related to the survival of the plant are seed germination, growth, and vigour. Therefore, this study was carried out to determine the germination and growth responses of L. corniculatus cultivar 'Leo', which is known to have higher tannin content than other cultivars, under NaCl-derived salt stress in vitro. For this purpose, L. corniculatus seeds were cultured in MS (Murashige and Skoog/Gamborg) medium containing 0, 40, and 80 mM NaCl for 14 days. Seed germination percentage, mean germination time, germination rate index, shoot-root length, root to shoot length ratio, shoot-root fresh dry weight, shoot-root dry matter, the ratio of root to shoot dry matter, shoot-root water content and seedling vigour index parameters were measured. According to the results of the research, the germination percentage did not change in the applied NaCl treatments, but the germination rate decreased. However, shoot length decreased and root length increased. Although there was no statistically significant change in shoot and root fresh-dry weight, both decreased in 80 mM NaCl treatment. The shoot and root dry matter increased and the water content decreased. Also, the seedling viability index decreased. In 40 mM NaCl treatment, on the other hand, there was an increase in shoot fresh-dry weight, dry matter ratio and seedling viability index with the positive effect of low dose. Within the scope of this study, comprehensive information was presented for L. corniculatus (cultivar 'Leo'), an important forage plant, in terms of germination and seedling growth under salt stress.

Melatonin enhances salt tolerance in sorghum by modulating photosynthetic performance, osmoregulation, antioxidant defense, and ion homeostasis.

Melatonin is a potent antioxidant that can prevent plant damage caused by adverse stresses. It remains unclear whether exogenous melatonin can mitigate the effects of salt stress on seed germination and seedling growth of sorghum (Sorghum bicolor (L.) Moench). The aim of this study was to decipher the protective mechanisms of exogenous melatonin (100 μmol/L) on sorghum seedlings under NaCl-induced salt stress (120 mmol/L). Plant morphological, photosynthetic, and physiological characteristics were analyzed at different timepoints after sowing. Results showed that salt stress inhibited seed germination, seedling growth, and plant biomass accumulation by reducing photosynthetic pigment contents, photosynthetic efficiency, root vigor, and mineral uptake. In contrast, seed priming with melatonin enhanced photosynthetic pigment biosynthesis, photosynthetic efficiency, root vigor, and K+ content under salt stress. Melatonin application additionally enhanced the activities of antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase) and increased the levels of non-enzymatic antioxidants (reduced glutathione, ascorbic acid) in the leaves. These changes were accompanied by increase in the leaf contents of soluble sugars, soluble proteins, and proline, as well as decrease in hydrogen peroxide accumulation, malondialdehyde content, and electrolyte leakage. Our findings indicate that exogenous melatonin can alleviate salt stress-induced damage in sorghum seedlings through multifaceted mechanisms, such as improving photosynthetic performance and root vigor, facilitating ion homeostasis and osmoregulation, and promoting antioxidant defense and reactive oxygen species scavenging.

Responses of two strawberry cultivars to NaCl-induced salt stress under the influence of ZnO nanoparticles

Salinity stress is one of the most serious impacts of climate changes on agriculture production, especially in salt sensitive crop plants, like strawberry. Currently, the utilization of nanomolecules in agriculture is thought to be a useful strategy to compact abiotic and biotic stresses. This study aimed to investigate the effect of zinc oxide nanoparticles (ZnO-NPs) on the in vitro growth, ions uptake, biochemical and anatomical responses of two strawberry cvs (Camarosa and Sweet Charlie) under NaCl-induced salt stress. A 2x3x3 factorial experiment was conducted, with three levels of ZnO-NPs (0, 15 and 30 mg 1-l) and three levels of NaCl-induced salt stress (0, 35 and 70 mM). The results showed that increased levels of NaCl in the medium had led to decrease in shoot fresh weight and proliferative potential. The cv Camarosa was found to be relatively more tolerant to salt stress. Additionally, salt stress leads to an accumulation of toxic ions (Na + and Cl-), as well as a decrease in K + uptake. However, application of ZnO-NPs at a concentration of 15 mg 1-l was found to alleviate these effects by increasing or stabilizing growth traits, decreasing the accumulation of toxic ions and the Na+/K + ratio, and increasing K + uptake. Additionally, this treatment led to elevated levels of catalase (CAT), peroxidase (POD) and proline content. The positive impacts of ZnO-NPs application were reflected on the leaf anatomical features, being better adapted to salt stress. The study highlighted the efficiency of utilizing tissue culture technique in screening of strawberry cultivars for salinity tolerance under the influence of NPs.

Overexpression of gibberellin 2-oxidase 4 from tall fescue affected plant height, tillering and drought tolerance in rice

Gibberellin (GA) is an important phytohormone that regulates plant growth and development. GA-2-oxidases (GA2oxs) have been found to affect plant height, tillering and stress tolerance by inactivating endogenous bioactive GAs. The present study aimed to isolate GA2oxs genes from tall fescue (Festuca arundinacea), analyze their expression level under abiotic stresses (10% PEG6000 induced drought stress, 150 mM NaCl induced salt stress, heat stress at 38 °C, and cold stress at 4 °C) and search for valuable genes for improving stress tolerance. Among eight FaGA2ox genes, FaGA2ox4 was found to represent a highest expression level at 24 h of PEG-induced drought stress and was chosen for further analysis. Compared with wildtype plants, transgenic rice plants overexpressing FaGA2ox4 exhibited a dwarf and high-tillering phenotype and the dwarf phenotype was partially compensated by foliar application of 10 μM GA3. In addition, transgenic plants showed improved drought stress tolerance, as manifested by higher leaf relative water content and lower electrolyte leakage than wildtype. Further qRT-PCR analysis demonstrated that the enhanced drought stress tolerance may be associated with decreased expression levels of genes involved in chlorophyll degradation (OsSGRL) and GA synthesis (OsGA3ox1) as well as increased expression of ABA-synthesizing gene (OsNCED3) in transgenic plants overexpressing FaGA2ox4.

Quantitative Proteomics Analysis Reveals Proteins Associated with High Melatonin Content in Barley Seeds under NaCl-Induced Salt Stress.

Soil salinization limits hull-less barley cultivation in the Qinghai-Tibet Plateau of China. However, some wild hull-less barley seeds accumulate high melatonin (MEL) during germination with improved salt tolerance; but the mechanism of melatonin-mediated salt tolerance in hull-less barley is not well understood at the protein level. This study investigated proteome changes resulting in high melatonin content in germinating hull-less barley seeds under high saline conditions. The proteome profiles of seed treatment with 240 mM-NaCl (N), water (H), and control (C) taken 7 days after germination were compared using the TMT-based quantitative proteomics. Our results indicate that salt stress-induced global changes in the proteomes of germinating hull-less barley seeds, altering the expression and abundance of proteins related to cell cycle and control, carbohydrate and energy metabolism, and amino acid transport and metabolism including proteins related to melatonin production. Furthermore, proteins associated with cellular redox homeostasis, osmotic stress response, and secondary metabolites derived primarily from amino acid metabolism, purine degradation, and shikimate pathways increased significantly in abundance and may contribute to the high melatonin content in seeds under salt stress. Consequently, triggering the robust response to oxidative stress occasioned by the NaCl-induced salt stress, improved seed germination and strong adaptation to salt stress.

Growth and nitrogen metabolism in Sophora japonica (L.) as affected by salinity under different nitrogen forms

Sophora japonica is a leguminous tree species native to China. To explore the nitrogen (N) source preference and its impact on stress tolerance, a hydroponic experiment was designed in which S. japonica seedlings were supplied with sole ammonium (NH4+) or sole nitrate (NO3−) nutrition under 75 mM NaCl-induced salt stress. The growth and N metabolism performance were investigated. In the absence of NaCl, plants fed NH4+ showed better root growth than those fed NO3−, but there was no difference in aerial part growth. Salinity inhibited the root growth of NH4+-fed plants and the shoot growth of NO3−-fed plants, while the total N accumulation was suppressed under either N form. Specifically, in NH4+-fed plants, salinity significantly increased the net photosynthetic rate, root NH4+ content and root antioxidant enzyme activities. Higher nitrate reductase (NR) activities but lower glutamate synthetase (GS) activities were observed in both leaves and roots. Leaf AMT1.1 and AMT2.1a in NH4+-fed plants positively reacted to salt stress, whereas the expression of four AMTs was reduced or remained unchanged in roots. In contrast, salinity suppressed the net photosynthetic rate, antioxidant enzyme activities, and GS activity in the leaves of NO3−-fed plants. Upregulation of NPF1.2, NPF2.11, NPF4.6 and NPF7.3, as well as unaltered NR activity, caused higher NO3− content in the leaves. Moreover, NR and glutamate synthase (GOGAT) activities together with the transcription of most NRTs were promoted by salinity in the roots of NO3−-fed plants. Additionally, compared to those treated with NH4+, in response to salinity, NO3−-treated seedlings showed more intensive repression of the net photosynthetic rate, chlorophyll content, and both shoot and root growth. Overall, these results suggest that S. japonica plants grew better in NH4+ medium than in NO3− medium, and the different N metabolism responses improved S. japonica tolerance to salinity with NH4+ application. This study provides new insights for understanding the mechanism of salt tolerance, breeding resistant varieties of S. japonica, and developing scientific fertilization management strategies during the seedling cultivation period.

Assessment of selenium contribution to salt and water stress tolerance in hydroponically grown cotton (Gossypium barbadense L.)

Selenium (Se) is a trace element but its basic role in plant physiology is still poorly known. An experiment to investigate the role of Se in enhancing cotton growth and its efficiency in alleviating PEG-induced water stress and NaCl-induced salt stress under controlled conditions was conducted. The hydroponically grown cotton was supplied with selenium dioxide (SeO2) as a source of Se. The study included six treatments (control, 80 mM NaCl, 50 g/L PEG-6000, 10 µM Se, Se + NaCl and Se + PEG). All treatments were grown hydroponically in frequently aerated Hogland’s solution for 15 days. The experiment was repeated once again to validate the results. The results demonstrated that NaCl and PEG decreased cotton biomass, photosynthetic pigments and the essential macro-nutrients significantly. However, H2O2, OH˙ and MDA over-accumulated, CAT, POD and PPO activities up-regulated and SOD activity down-regulated by stress treatments. Plant biomass, pigments content and ionic balance were improved by Se supplementation to the growth medium. Nonetheless, ROS accumulation, Na uptake and the activities of CAT, POD and PPO were retrieved. The current work suggests Se as a potent treatment to counteract the detrimental effects of water and salt stresses on growth and metabolic activity of cotton.

TMT based proteomic profiling of Sophora alopecuroides leaves reveal flavonoid biosynthesis processes in response to salt stress

Salt stress is the major abiotic stress worldwide, adversely affecting crop yield and quality. Utilizing salt tolerance genes for the genetic breeding of crops is one of the most effective measures to withstand salinization. Sophora alopecuroides is a well-known saline-alkaline and drought-tolerant medicinal plant. Understanding the underlying molecular mechanism for Sophora alopecuroides salt tolerance is crucial to identifying the salt-tolerant genes. In this study, we performed tandem mass tag (TMT) based proteomic profiling of S. alopecuroides leaves under 150 mM NaCl induced salt stress condition for 3 d and 7 d. Data are available on ProteomeXchange (PXD027627). Furthermore, the proteomic findings were validated through parallel reaction monitoring (PRM). We observed that the expression levels of several transporter proteins related to the secondary messenger signaling pathway were altered under salt stress conditions induced for 3 d. However, the expression of the certain transferase, oxidoreductase, dehydrogenase, which are involved in the biosynthesis of flavonoids, alkaloids, phenylpropanoids, and amino acid metabolism, were mainly alerted after 7 d post-salt-stress induction. Several potential genes that might be involved in salt stress conditions were identified; however, it demands further investigation. Although salt stress affects the level of secondary metabolites, their correlation needs to be investigated further. SignificanceSalinization is the most severe abiotic adversity, which has had a significant negative effect on world food security over the time. Excavating salt-tolerant genes from halophytes or medicinal plants is one of the important measures to cope with salt stress. S. alopecuroides is a well-known medicinal plant with anti-tumor, anti-inflammatory, and antibacterial effects, anti-saline properties, and resistance to drought stress. Currently, only a few studies have explored the S. alopecuroides’ gene function, and regulation and these studies are mostly related to the unpublished genome sequence information of S. alopecuroides. Recently, transcriptomics and metabolomics studies have been carried on the abiotic stress in S. alopecuroides roots. Multiple studies have shown that altered gene expression at the transcript level and altered metabolite levels do not correspond to the altered protein levels. In this study, TMT and PRM based proteomic analyses of S. alopecuroides leaves under salt stress condition induced using 150 mM NaCl for 3 d and 7 d was performed. These analyses elucidated the activation of different mechanisms in response to salt stress. A total of 434 differentially abundant proteins (DAPs) in salt stress conditions were identified and analyzed. For the first time, this study utilized proteomics technology to dig out plentiful underlying salt-tolerant genes from the medicinal plant, S. alopecuroides. We believe that this study will be of great significance to crop genetics and breeding.

Transcriptome revealed the molecular mechanism of Glycyrrhiza inflata root to maintain growth and development, absorb and distribute ions under salt stress

BackgroundSoil salinization extensively hampers the growth, yield, and quality of crops worldwide. The most effective strategies to counter this problem are a) development of crop cultivars with high salt tolerance and b) the plantation of salt-tolerant crops. Glycyrrhiza inflata, a traditional Chinese medicinal and primitive plant with salt tolerance and economic value, is among the most promising crops for improving saline-alkali wasteland. However, the underlying molecular mechanisms for the adaptive response of G. inflata to salinity stress remain largely unknown.ResultG. inflata retained a high concentration of Na+ in roots and maintained the absorption of K+, Ca2+, and Mg2+ under 150 mM NaCl induced salt stress. Transcriptomic analysis of G. inflata roots at different time points of salt stress (0 min, 30 min, and 24 h) was performed, which resulted in 70.77 Gb of clean data. Compared with the control, we detected 2645 and 574 differentially expressed genes (DEGs) at 30 min and 24 h post-salt-stress induction, respectively. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses revealed that G. inflata response to salt stress post 30 min and 24 h was remarkably distinct. Genes that were differentially expressed at 30 min post-salt stress induction were enriched in signal transduction, secondary metabolite synthesis, and ion transport. However, genes that were differentially expressed at 24 h post-salt-stress induction were enriched in phenylpropane biosynthesis and metabolism, fatty acid metabolism, glycerol metabolism, hormone signal transduction, wax, cutin, and cork biosynthesis. Besides, a total of 334 transcription factors (TFs) were altered in response to 30 min and 24 h of salt stress. Most of these TFs belonged to the MYB, WRKY, AP2-EREBP, C2H2, bHLH, bZIP, and NAC families.ConclusionFor the first time, this study elucidated the salt tolerance in G. inflata at the molecular level, including the activation of signaling pathways and genes that regulate the absorption and distribution of ions and root growth in G. inflata under salt stress conditions. These findings enhanced our understanding of the G. inflata salt tolerance and provided a theoretical basis for cultivating salt-tolerant crop varieties.

Universal stress protein-like gene from mulberry enhances abiotic stress tolerance in Escherichia coli and transgenic tobacco cells.

Universal stress proteins (USPs) are a conserved group of proteins initially identified and characterized in bacteria. USPs are induced under multiple stresses, and are important for stress acclimation. We cloned a USP-like gene designated as MaUSP1-like from mulberry and expressed in bacteria and tobacco to examine its relevance in abiotic stress tolerance. Escherichia coli and tobacco cells expressing MaUSP1-like gene were exposed to different abiotic stresses, and cell survival and growth was recorded to assess the stress effects. MaUSP1-like gene conferred tolerance to E.coli cells under NaCl-induced salt stress, PEG8000-induced desiccation stress, cadmium chloride-induced heavy metal stress, and heat stress. Overexpression of MaUSP1-like sustained cell division and growth in tobacco cells under salt stress. The results demonstrate that MaUSP1-like gene is capable of conferring cellular level tolerance in both prokaryotic and eukaryotic systems, under abiotic stress. The finding opened up an option to argue that maintenance of cellular level tolerance is crucial for sustenance of growth under stress and cellular level tolerance can be improved by overexpressing genes like USPs.

Morphological, physiological, and biochemical responses to NaCl-induced salt stress in mungbean (Vigna radiata L.) varieties

Seventeen mungbean varieties [Vigna radiata (L.) R. Wilczek] were subjected to 100-400 mM salinity stress at the germination stage, and the indices of seed germination and early seedling growth were analysed. With the increasing salinity, seed germination and seedling growth attributes were affected in all varieties. Principal component analysis and hierarchical cluster analysis of varietal responses on the germination and seeding growth attributes at 400 mM NaCl separated seventeen varieties into four distinct clusters. Principal component analysis at lower salt stress levels indicated that the attributes of germination and early seedling growth are reliable to identify salt-tolerant mungbean varieties. In contrast, only germination attributes are reliable at higher salinity levels. Two salt-susceptible and salt-tolerant varieties were further assessed for NaCl-induced physiological and biochemical changes. Levels of proteins, secondary metabolites, osmolyte, and antioxidants were increased at lower salt concentrations but reduced at higher salt concentrations. Photosynthetic pigments decreased and membrane damage increased under salinity. Varieties that showed tolerance to salt stress can be used in salinity-affected agriculture fields after validating their salt tolerance in field experiments.

Stress tolerance of Xerocomus badius and its promotion effect on seed germination and seedling growth of annual ryegrass under salt and drought stresses

Comparative evaluations were conducted to assess the effects of different pH levels, NaCl-induced salt stress, and PEG-induced drought stress on the mycelial growth of Xerocomus badius. The results showed that X. badius mycelium grew well at a wide pH range of 5.00 ~ 9.00. Although the mycelium remained viable, mycelial growth of X. badius was significantly inhibited with increasing salt and drought stresses. Furthermore, a soilless experiment in Petri dishes was performed to investigate the potential of X. badius to induce beneficial effects on seed germination and seedling growth of annual ryegrass (Lolium multiflorum Lam.) under salt and drought stresses. Seed priming with X. badius enhanced the seedling growth of L. multiflorum Lam. under NaCl-induced salt stress and PEG-induced drought stress. However, X. badius did not significantly improve the seed germination under non-stress and mild stress conditions. It suggested that X. badius inoculation with seeds was not essential for seed germination under non-stress and mild stress conditions, but contributed highly to seedling growth under severe stress conditions. Therefore, seed priming with X. badius on ryegrass could be an effective approach to enhance plant tolerance against drought and salt stresses. X. badius could be a good candidate for the inoculation of ectomycorrhizal plants cultivation programs in mild saline and semiarid areas.

Crosstalk between grapevine leafroll-associate virus-3 (GLRaV-3) and NaCl-induced salt stress in in vitro cultures of the red grape ‘Cabernet Sauvignon’

Crosstalk between grapevine leafroll-associate virus-3 (GLRaV-3) and NaCl-induced salt stress in in vitro cultures of the red grape ‘Cabernet Sauvignon’

Methyl jasmonate improves physiological and biochemical responses of Anchusa italica under salinity stress

Jasmonates are key signaling compounds in plant responses to biotic and abiotic stresses as well as in development. We studied the salt-tolerance capacity and the role of methyl jasmonate (MeJA) in alleviating NaCl-induced salt stress of Anchusa italica through evaluating its growth, physiological and biochemical attributes in a pot-culture. Accordingly, plants were exposed to the salinity concentrations of 1.86 (control), 5, 10 and 15 dS m−1 for 2 weeks, 24 h after foliar application of 0, 60 and 120 µM MeJA. Salt stress induced a significant reduction in leaf fresh weight, leaf area, leaf relative water content (RWC) and concentrations of chlorophyll a (Chl a), total chlorophyll (TChl), soluble sugars, total protein and K+, while an increase in proline, Na+ and Ca2+ contents. However, exogenous application of MeJA enhanced contents of Chl a, TChl, proline, soluble sugars, protein, K+ and Ca2+ while declined Na+ content in salt-stressed plants. In addition, pretreatment with 120 µM MeJA improved the growth attributes such as leaves and roots fresh weights, leaves and plant dry weights, leaf area and RWC. In summary, our results indicated that A. italica could tolerate the moderate levels of salinity (5 and 10 dS m−1). Also, foliar application of MeJA could reduce the adverse effects of salinity stress in A. italica.

Influence of NaCl induced salt stress on the seedling growth of citrus species

Salinity is a commonly occurring abiotic stress and poses as a major impediment in citrus production as the crop has less tolerance ability to this stress. It causes severe osmotic stress restraining overall performance of the plant. One month old seedlings of Rangpur lime, Rough lemon and Indian wild orange were established in sand media and later exposed to stress for 48 hrs in a low cost polyhouse. The different levels of sodium chloride (0 mM, 75 mM and 100 mM) was used for simulating salt stress. The morpho-physiological parameters viz., shoot and root length, fresh and dry weight of shoot and root and Relative water content (RWC) were reduced on exposing to stress with severity being in 100 mM NaCl. On comparing citrus species, Rangpur lime performed better at both stress levels than Rough lemon and Indian wild orange exhibiting its tolerance towards salinity.

Biochemical changes in Cicer arietinum L. under NaCl-induced salt stress

Biochemical changes in Cicer arietinum L. under NaCl-induced salt stress

Nuclear Migration: An Indicator of Plant Salinity Tolerance in vitro.

In order to understand the mechanisms underlying acquisition of tolerance to salinity, we recently produced callus tissues of tobacco and Medicago truncatula resistant to NaCl-induced salt stress following application of a step-up recurrent selection method. The effects of salinity on cell size are known, but those on cell morphometry including cell and nuclear surface area and position of nuclei within salt stress resistant cells were never studied before. This work fills that gap, using suspension cultured cells of M. truncatula A17 initiated from callus, and Nicotiana tabacum BY-2 cell line resistant to increasing NaCl concentrations up to 150 mM NaCl. The surface area of salinity resistant cells of M. truncatula A17 and N. tabacum BY2 and their nuclei, produced by step-up recurrent selection, were reduced, and cells elongated as NaCl increased, but these parameters proved to be unreliable in explaining cell survival and growth at high NaCl. Conversely, nuclei of resistant cells migrated from the center to the periphery of the cytoplasm close to the walls. Nuclear marginalization was for the first time observed as a result of salt stress in plant cells, and could be a novel helpful morphological marker of acquisition of salinity tolerance.

Mitigation of adverse effects of salt stress on germination, growth, photosynthetic efficiency and yield in maize (Zea mays L.) through magnetopriming

The efficiency of magnetopriming was evaluated for mitigation of the detrimental effects of salt stress on maize germination, growth, photosynthesis, and yield of maize plants. Maize seeds were pretreated with 200 mT of static magnetic field (SMF) for 1 h to assess the impact of SMF on the germination, seedling vigor, growth of plant, photosynthetic performance, ROS content, and yield under salt stress. The seedling characteristics of maize were negatively influenced by salt stress. However, SMF-pretreated maize seeds showed relatively higher germination percentage and germination stress tolerance index as compared to untreated seeds in saline and nonsaline conditions. The detrimental effect of NaCl induced salt stress was also observed on growth, yield, and different physiological characteristic of maize plants. The results showed that SMF-pretreated seeds enhanced seedling vigor, growth parameters such as plant height, leaf area, and biomass accumulation at different concentrations of NaCl (0, 25, 50, 75, and 100 mM) as compared to untreated seeds. Photosynthetic pigments, quantum yield of PSII photochemistry (Fv/Fm), phenomenological fluxes such as electron transport per leaf CS (ETo/CSm) and density of reaction centers (RC/CSm), the performance index (PI) were high in the leaves of plants that emerged from SMF-pretreated seeds as compared to untreated seeds. This stimulatory effect of SMF treatment of seeds was also revealed in the rate of photosynthesis and stomatal conductance, which results in improved yield of maize plants under saline conditions. The leaves from plants of SMF-treated seeds showed decreased hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) when compared with untreated seeds in both conditions. SMF ameliorates the adverse effect of salt stress in maize plants, by reducing H<sub>2</sub>O<sub>2</sub> and increasing growth, photosynthetic performance, and yield under salt stress. For improvement of salt tolerance, magnetopriming with SMF of 200 mT for 1 h to dry seeds of maize can be efficiently used as a presowing treatment.

Halo-tolerant rhizospheric Arthrobacter woluwensis AK1 mitigates salt stress and induces physio-hormonal changes and expression of GmST1 and GmLAX3 in soybean

In the present study rhizospheric bacteria were isolated from sand dune-dwelling Artemisia princeps, Chenopodium ficifolium, Oenothera biennis, and Echinochloa crus-galli and evaluated the ability of the bacterial isolates to produce jasmonic acid (JA) and abscisic acid (ABA) under NaCl-induced salt stress. We observed that 7 of 126 bacterial isolates were capable of producing siderophores, gibberellic acid (GA), indole-3-acetic acid (IAA), phosphate solubilisation, organic acids e.g., quinic acid, succinic acid, acetic acid and butyric acid. A bioassay of the seven selected isolates on rice showed that the isolate AK1 significantly promoted rice growth. Moreover, AK1 produced IAA and ABA in broth spiked with elevated levels of NaCl (100 mM, 200 mM, 300 mM, and 400 mM). The isolate AK1 was further investigated for plant growth promotion and mitigation of NaCl-induced salt stress in soybean grown under 100 mM, 200 mM, and 300 mM stress. Application of AK1 upregulated the expression of GmLAXs, and GmST genes in plants exposed to salt stress as compared to uninoculated plants. Interestingly, the bacteria-treated soybean showed significant increase in growth attributes with or without salinity stress. The endogenous ABA and JA level of inoculated soybean plants declined under elevated salt stress, thus showing an enhanced stress mitigation. A similar ameliorative trend was observed for total proteins, polyphenol oxidase, and peroxidase activity under saline conditions. The isolate AK1 was identified as Arthrobacter woluwensis AK1 based on its 16S rDNA gene sequencing and subsequent phylogenetic analysis.