Salt-treated Plants Research Articles

Effects of Salinity on ‘Fino 95’ Lemon Trees Inoculated with Arbuscular Mycorrhizal Fungi

An experiment was conducted with two-year-old ‘Fino 95’ lemon plants (Citrus limon Burm. f. cv. Fino) grafted on C. macrophylla (Citrus macrophylla Wester) to study the effects of salinity on plants inoculated with arbuscular mycorrhizal fungi (AMF). Half of the inoculated (+AM) and non-inoculated (−AM) plants were irrigated with half-strength Hoagland solution, and the remainder were inoculated with half-strength Hoagland solution + 30 mM NaCl. Ninety-eight days later, results showed that AMF had alleviated the negative effect of salinity on growth. Inoculation with AMF provided some protection against the damage that salinity caused on cellular membranes and improved the plant water status and turgor under saline conditions (Ψx and Π increased by 16% and 48%, respectively). The responses of mineral nutrition to salinity and AMF treatments were complex. P concentrations in the leaves and roots of +AM plants were lower than in those of −AM plants, but inoculation improved Ca2+ (by 20%), Mg2+ (24%), Fe2+ (21%), and Zn2+ (7%) nutrition in roots and also the Mg2+/Na+ ratio in leaves (33%), reducing the antagonistic effect of Na+ on Mg2+ nutrition in salt-treated plants. AMF could protect plants against salt stress through the maintenance of the gas exchange capacity and due to a better antioxidant response. All these positive effects of AMF contributed to mitigating the harmful effects of salinity stress on the plant growth performance of lemon trees grafted on C. macrophylla rootstock under salinity conditions.

Physiochemical interaction between osmotic stress and a bacterial exometabolite promotes plant disease

Various microbes isolated from healthy plants are detrimental under laboratory conditions, indicating the existence of molecular mechanisms preventing disease in nature. Here, we demonstrated that application of sodium chloride (NaCl) in natural and gnotobiotic soil systems is sufficient to induce plant disease caused by an otherwise non-pathogenic root-derived Pseudomonas brassicacearum isolate (R401). Disease caused by combinatorial treatment of NaCl and R401 triggered extensive, root-specific transcriptional reprogramming that did not involve down-regulation of host innate immune genes, nor dampening of ROS-mediated immunity. Instead, we identified and structurally characterized the R401 lipopeptide brassicapeptin A as necessary and sufficient to promote disease on salt-treated plants. Brassicapeptin A production is salt-inducible, promotes root colonization and transitions R401 from being beneficial to being detrimental on salt-treated plants by disturbing host ion homeostasis, thereby bolstering susceptibility to osmolytes. We conclude that the interaction between a global change stressor and a single exometabolite from a member of the root microbiome promotes plant disease in complex soil systems.

ACC-Deaminase producing Pseudomonas putida RT12 inoculation: A promising strategy for improving Brassica juncea tolerance to salinity stress

An important abiotic stressor that hinders plant growth, nutrient uptake, and global agricultural productivity is soil salinity. Among the different strategies to overcome the issue of salinity in agriculture sector, plant growth-promoting rhizobacteria (PGPR) have gained recognition as promising beneficial microbes that can improve plants’ response to biotic and abiotic stressors. The salinity tolerance and traits that promote plant growth of eight PGPR strains (RT1, RT2, RT3, RT4, RT5, RT7, and RT12) were evaluated in this study. During screening, one strain, RT12, had the highest plant growth-promoting activity and salt tolerance in the group. The strain when subjected to NaCl stress showed quantitative ACC-deaminase activity, in the presence of NaCl at various concentrations, demonstrating extraordinary tolerance to salt stress by withstanding doses of up to 3M NaCl. In order to further investigate the effects of salt stress on Brassica juncea (mustard), RT12, which was identified as Pseudomonas putida using 16s RNA sequencing, was inoculated. Two salt treatments (100 and 150 mM) were applied to the mustard variety ‘Mingora’ in a greenhouse. The results revealed that through ACC utilization, PGPR directly induced plant growth in salt-stressed mustard plants by lowering excess ethylene production. All plant parameters were negatively impacted by an increase in NaCl concentration in uninoculated plants. However, P. putida RT12 inoculation enhanced all growth parameters, antioxidant production, total soluble sugar (TSS), total protein (TP), proline, relative water content (RWC), chlorophyll contents, and nutrient uptake in salt-treated plants. The inoculation with P. putida also caused a marked decline in Na+ uptake and an increase in K+ uptake in the shoot. By maintaining a greater K+/Na+ ratio in the tissues of RT12-inoculated plants compared to controls, this change in ion uptake helped to maintain nutritional balance of the plants. The findings suggest that inoculating plants with ACC deaminase-producing PGPR, such as P. putida RT12, may boost growth and stress resistance.

Mitigation of salt stress in lettuce by a biostimulant that protects the root absorption zone and improves biochemical responses.

Horticultural crops constantly face abiotic stress factors such as salinity, which have intensified in recent years due to accelerated climate change, significantly affecting their yields and profitability. Under these conditions, it has become necessary to implement effective and sustainable solutions to guarantee agricultural productivity and food security. The influence of BALOX®, a biostimulant of plant origin, was tested on the responses to salinity of Lactuca sativa L. var. longifolia plants exposed to salt concentrations up to 150 mM NaCl, evaluating different biometric and biochemical properties after 25 days of treatment. Control plants were cultivated under the same conditions but without the biostimulant treatment. An in situ analysis of root characteristics using a non-destructive, real-time method was also performed. The salt stress treatments inhibited plant growth, reduced chlorophyll and carotenoid contents, and increased the concentrations of Na+ and Cl- in roots and leaves while reducing those of Ca2+. BALOX® application had a positive effect because it stimulated plant growth and the level of Ca2+ and photosynthetic pigments. In addition, it reduced the content of Na+ and Cl- in the presence and the absence of salt. The biostimulant also reduced the salt-induced accumulation of stress biomarkers, such as proline, malondialdehyde (MDA), and hydrogen peroxide (H2O2). Therefore, BALOX® appears to significantly reduce osmotic, ionic and oxidative stress levels in salt-treated plants. Furthermore, the analysis of the salt treatments' and the biostimulant's direct effects on roots indicated that BALOX®'s primary mechanism of action probably involves improving plant nutrition, even under severe salt stress conditions, by protecting and stimulating the root absorption zone.

Compositional shifts in rhizobacterial communities of Brassica napus under salinity stress

Salinity stress severely limits crop production globally. The plant rhizosphere harbors diverse microbial communities that can positively influence plant growth and stress tolerance. Therefore, we examined the rhizosphere bacterial populations of Brassica napus under normal and saline conditions using high-throughput 16S rRNA gene sequencing. The objectives were set to identify key taxa enriched in the rhizosphere and evaluate variations in community structure between control and salt-stressed Brassica napus plants. Proteobacteria, Actinobacteria, Chloroflexi, and Bacteroidetes were the predominant phyla. Key genera enriched in the rhizosphere included Sphingomonas, Streptomyces, Bacillus, and Pseudomonas. Salinity stress increased the abundances of Chloroflexi and Acidobacteria while decreased Actinobacteria. Rhizosphere communities of salt-treated plants showed lower diversity but separate clusters from controls, indicating salinity-induced shifts. Predictive functional analysis revealed that amino acid/carbohydrate metabolism and membrane transport pathways in salt-stressed rhizospheres were elevated. This study provides novel insights into the rhizosphere bacteriome of Brassica napus under salinity, highlighting potential plant-growth-promoting taxa for stress amelioration.

Comparison between the impact of osmotic and NaCl treatments on the expression of genes coding for ion transporters in Oryza glaberrima Steud.

We analyzed the expression of genes coding for Na+ transporters (OsHKT1.5, OsHKT1.1, OsSOS1, OsSOS2, OsNHX1, OsNHX2), Cl- transporter (OsNRT1, OsCLC, OsCCC1) and gene coding for the transcription factor DREB (OsDREB2) involved in response to desiccation in two cultivars of O. glaberrrima differing in salt-resistance (salt-tolerant cultivar (TOG5307) and salt-sensitive (TOG 5949)) exposed to NaCl, PEG or both agents present simultaneously. Seedlings were grown in iso-osmotic nutrient solution (Ψs = -0.47±0.02 MPa) containing PEG 6,000 12.9% (water stress), NaCl 75 mM (salt stress) and PEG 6.4% + NaCl 37.5 mM (MIX-treatment) during 1 and 7 days. Plants were analyzed for gene expression, mineral nutrients, and photosynthetic-related parameters. Na+ and Cl- accumulations in salt-treated plants were lower in roots and shoots of TOG5307 comparatively to TOG5949 while water content decreased in TOG5307. TOG5307 exhibited tolerance to water stress and maintained higher net photosynthesis and water use efficiency than TOG5949 in response to all treatments, but was less efficient for osmotic adjustment. Dehydration tolerance of TOG5307 involves a higher OsDREB2 expression. TOG5307 also exhibited a higher OsSOS1, OsSOS2, OsNHX1 and OsNHX2 expression than TOG5949 in response to salinity. OsHKT1.5 was slightly induced in the shoot. OsHKT1.1 was recorded in the shoots but remained undetectable in the roots. Chloride and sodium accumulations were strongly reduced in the shoots when PEG was present. Salinity resistance in Oryza glaberrima implies tolerance to dehydration as well as complementary strategies of Na+ exclusion through the SOS system and Na+ tolerance through vacuolar sequestration.

Deciphering the role of zinc oxide nanoparticles on physiochemical attributes of Zea mays exposed to saline conditions through modulation in antioxidant enzyme defensive system

Use of zinc oxide nanoparticles (ZnONPs) has the potential to increase the plant growth and development in agricultural sectors. Mode of application of NPs to plants is also of considerable importance. In present study, zinc oxide nanoparticles were prepared by using black seed extract and zinc salt. Characterized zinc oxide nanoparticles were then used to treat Zea mays L. in two types of treatments namely nano-priming and foliar nano-spray of zinc oxide nanoparticles. For each treatment a range of concentration was used i.e., 100, 200, 400, and 1000 mg/L. Experiment was conducted in randomized complete block design. Hydro-priming was used as a control. Whereas foliar spray was given after 30, 45, and 60 days of sowing. Plants were harvested after 90 days and various growth, physiological, biochemical, yield and stress parameters were studied. Results showed that monodispersed nanoparticles of average size of 45.56 nm were synthesized. Priming with ZnONPs showed better results as compared to foliar spray of ZnONPs. Highest germination (100%), Leaf length (350 cm), plant height (65 cm), and no. of leaves (10 leaves per plant) were recorded for corn plants with seed priming treatment of 200 mg/L of ZnONPs. These values were significantly higher than comparative positive control treatment values (salt-treated plants) as well. Whereas biochemical analysis also supported the results of growth parameters i.e., ZnONPs treated plants (200–1000 mg/L) showed higher values of sugar (0.6 µg), chlorophyll (1800 µg) and carotenoid content (400 µg). Protein and proline content was higher for zinc salt-treated (positive control) plants. Photosynthetic rate, CO2 sub-stomatal conductance, stomatal conductance and rate of transpiration was also higher for ZnONPs treated plants particularly in nano-primed plants. Whereas study of yield attributes showed highest cob length (14 cm), cob weight (80 g), cobs per plant (4) in ZnONPs treated plants that was significantly higher than the both controls. Stress studies of plant samples showed that peroxidase activity was highest in plants treated with 1000 mg/L zinc salt-treated salts, both in case of priming and foliar spray. Whereas catalase activity was found highest in ZnONPs (200 mg/L) foliar spray treated plants. Zinc content analysis of plant sample showed significantly higher amount of zinc in ZnONPs treated corn plants. It is concluded from present study that ZnONPs in priming treatment significantly enhanced the growth and yield attributes of corn plants through the balance of biochemical and stress indicators. Priming and foliar spray of ZnONPs also fortified the crop with enhanced zinc content. Future study with combination of both priming and foliar spray may be further optimized.

Morpho-physiological effects of irrigation with saline water in ex vitro plants of Juglans regia ‘Sorrento’

Soil salinization is a global problem limiting growth and economical yield in fruit species including walnut. Knowledge of the response of varieties and cultivars to salinity can represent an important contribution to future walnut plantation in areas affected by soil salinization. Juglans regia ‘Sorrento’ is a commercially important Italian variety. The present work aimed to explore the morpho-physiological response to NaCl-induced stress in ‘Sorrento’ plants using clonally propagated ex vitro plantlets to reduce the impact of genetic variation. Ex vitro acclimatized plants were exposed to salinity conditions by irrigating pot soil with half-strength Hoagland solution containing 100 mM NaCl for 20 days. Salt-induced effects on plant growth, chlorophyll and carotenoid content, osmolality, membrane injury and on activities of antioxidant enzymes catalase and guaiacol peroxidase (G-POD) in leaves were evaluated. Morphological and growth parameters were not significantly altered by salt stress with respect to the control. Slight differences in leaf necrosis and absence of injury in the membranes, stable content of photosynthetic pigments, and an increase in G-POD activity were also found in salt-treated plants. These results collectively suggest that ‘Sorrento’ has potential for the cultivation in salinized environments.

Alleviative effects of Faradarmani Consciousness Field on Triticum aestivum L. under salinity stress.

Background: The Faradarmani Consciousness Field was founded by Mohammad Ali Taheri. It is a novel field and is described similarly to the field of gravity, or the electromagnetic field. This field is neither matter nor energy, and therefore does not possess a quantity. Even though there is no direct scientific evidence for the Consciousness Field, it is possible to investigate its effects on objects through controlled experiments. The aim of the present work was to study the alleviative effects of the Faradarmani Consciousness Field on common wheat Triticum aestivum L. var Star under salt stress. Methods: Plants were grown under 0 mM NaCl (control) and 150 mM NaCl with or without the influence of Faradarmani Consciousness Field for 3 weeks. Chlorophyll, hydrogen peroxide (H 2O 2), malondialdehyde (MDA) content and activity of antioxidant enzymes such as superoxide dismutase (SOD),polyphenol oxidase (PPO), and peroxidase (POX) were measured in all groups of plants. Results: In the salt-treated plants under the influence of the Faradarmani Consciousness Field, the contents of total chlorophyll, as well as a and b chlorophyll forms, were elevated compared with the salt-treated plants without Faradarmani CF (34.8%, 17.8%, and 169% respectively). Additionally, Faradarmani increased H 2O 2 (57%) and the activity of SOD and PPO by 220% and 168%, respectively, under salinity compared with the salt-treated plants without Faradarmani CF. MDA content and activity of peroxidase were decreased by 12.5% and 34%, respectively. Conclusion: These results suggest the Faradarmani Consciousness Field as a qualitative intervention strategy to withstand salt stress in plants, by increasing the contents of chlorophyll, antioxidant enzyme activities, and decreasing MDA content under salinity.

Exogenous zinc mitigates salinity stress by stimulating proline metabolism in proso millet (Panicum miliaceum L.).

Salinity is one of the most concerning ecological restrictions influencing plant growth, which poses a devastating threat to global agriculture. Surplus quantities of ROS generated under stress conditions have negative effects on plants' growth and survival by damaging cellular components, including nucleic acids, lipids, proteins and carbohydrates. However, low levels of ROS are also necessary because of their role as signalling molecules in various development-related pathways. Plants possess sophisticated antioxidant systems for scavenging as well as regulating ROS levels to protect cells from damage. Proline is one such crucial non-enzymatic osmolyte of antioxidant machinery that functions in the reduction of stress. There has been extensive research on improving the tolerance, effectiveness, and protection of plants against stress, and to date, various substances have been used to mitigate the adverse effects of salt. In the present study Zinc (Zn) was applied to elucidate its effect on proline metabolism and stress-responsive mechanisms in proso millet. The results of our study indicate the negative impact on growth and development with increasing treatments of NaCl. However, the low doses of exogenous Zn proved beneficial in mitigating the effects of NaCl by improving morphological and biochemical features. In salt-treated plants, the low doses of Zn (1 mg/L, 2 mg/L) rescued the negative impact of salt (150mM) as evidenced by increase in shoot length (SL) by 7.26% and 25.5%, root length (RL) by 21.84% and 39.07% and membrane stability index (MSI) by 132.57% and 151.58% respectively.The proline content improved at all concentrations with maximum increase of 66.65% at 2 mg/L Zn. Similarly, the low doses of Zn also rescued the salt induced stress at 200mM NaCl. The enzymes related to proline biosynthesis were also improved at lower doses of Zn. In salt treated plants (150mM), Zn (1 mg/L, 2 mg/L) increased the activity of P5CS by 19.344% and 21%. The P5CR and OAT activities were also improved with maximum increase of 21.66% and 21.84% at 2 mg/L Zn respectively. Similarly, the low doses of Zn also increased the activities of P5CS, P5CR and OAT at 200mM NaCl. Whereas P5CDH enzyme activity showed a decrease of 82.5% at 2mg/L Zn+150mM NaCl and 56.7% at 2mg/L Zn+200 mM NaCl. These results strongly imply the modulatory role of Zn in maintaining of proline pool during NaCl stress.

Circadian Clock Contributes to Modulate Salinity Stress-Responsive Antioxidative Mechanisms and Chloroplast Proteome in Spinacia oleracea

Extreme abiotic stresses such as drought, salinity, and temperature reduce crop productivity significantly and pose a serious threat to the area of land used for agriculture. Therefore, there is a pressing need to create crops that can thrive in these circumstances. It has been noted that plants can maintain defense mechanisms during any environmental changes and anticipate diurnal patterns correct to a circadian-based clock. Therefore, the main aim of this study was to investigate the role of circadian core oscillators in response to salinity stress in an important vegetable crop, spinach, and obtain evidence to better understand salinity stress adaptation for crop productivity. Therefore, the current study was carried out to examine the circadian clock-based (morning–evening loop) salinity stress defense mechanism in spinach (Spinacia oleracea), a leafy vegetable crop with significant economic importance and health benefits. In the presence of dawn and dusk, the circadian clock-based defense mechanism was observed using the genotypes “Delhi Green” and “Malav Jyoti.” A photoperiodic rhythm consists of 4-h intervals for 12 h (morning–evening loop) in spinach was demonstrated under the salinity stress treatments (20 mM and 50 mM). The clock-controlled a large fraction of growth parameters such as plant height, biomass, and root-shoot ratio under salinity stress. Conversely, salinity stress resulted in upregulation of antioxidative parameters such as superoxide dismutase, ascorbate peroxidase, catalase, and other stress markers such as thiobarbituric acid reactive substances, proline content, and localizations of H2O2 and O2−1 but was altered and maintained at a certain photoperiodic time interval of the circadian clock. In distinction to results observed from antioxidative measurements performed with an early and late circadian duration of salt-treated plants, 10 am and 2 pm were revealed to be the rhythmic times for controlling salinity stress. Likewise, comprehensive measurements of the photosynthetic system under salinity stress at specific photoperiodic circadian time intervals, including net-photosynthetic rate, transpiration, stomatal conductance, PSII quantum yield, and stomata structure, were made at 10 am and 2 pm. The salinity stress response was down-streamed and the clock also regulated chloroplastic protein expression. Thus, according to our findings, photoperiodic circadian rhythms, particularly the morning–evening loop, enhanced plant survival rates by modulating cellular antioxidant mechanisms and chloroplastic proteins that further helped to reduce the effects of salinity stress.

Palliating Salt Stress in Mustard through Plant-Growth-Promoting Rhizobacteria: Regulation of Secondary Metabolites, Osmolytes, Antioxidative Enzymes and Stress Ethylene.

The severity of salt stress is alarming for crop growth and production and it threatens food security. Strategies employed for the reduction in stress are not always eco-friendly or sustainable. Plant-growth-promoting rhizobacteria (PGPR) could provide an alternative sustainable stress reduction strategy owning to its role in various metabolic processes. In this study, we have used two strains of PGPR, Pseudomonas fluorescens (NAIMCC-B-00340) and Azotobacter chroococcum Beijerinck 1901 (MCC 2351), either singly or in combination, and studied their effect in the amelioration of salt toxicity in mustard cultivar Pusa Jagannath via its influence on plants' antioxidants' metabolism, photosynthesis and growth. Individually, the impact of Pseudomonas fluorescens was better in reducing stress ethylene, oxidative stress, photosynthesis and growth but maximal alleviation was observed with their combined application. MDA and H2O2 content as indicator of oxidative stress decreased by 27.86% and 45.18% and osmolytes content (proline and glycine-betaine) increased by 38.8% and 26.3%, respectively, while antioxidative enzymes (SOD, CAT, APX and GR) increased by 58.40, 25.65, 81.081 and 55.914%, respectively, over salt-treated plants through the application of Pseudomonas fluorescens. The combined application maximally resulted in more cell viability and less damage to the leaf with lesser superoxide generation due to higher antioxidative enzymes and reduced glutathione formation (GSH). Considering the obtained results, we can supplement the PGPR in combination to plants subjected to salt stress, prevent photosynthetic and growth reduction, and increase the yield of plants.

Integrated transcriptomics and metabolomics analyses provide insights into salt-stress response in germination and seedling stage of wheat (Triticum aestivum L.)

One of the key elements impacting the productivity of wheat production is soil salinity. Here, we characterize the metabolomic and transcriptome responses to salt stress in two distinct wheat cultivars with varying levels of salt tolerance. Cangmai 6005 (CM6005) is a new wheat variety bred in the Cangzhou Academy of Agriculture and Forestry Sciences. After salt treatment, the germination and seedling stage of CM6005 maintains green leaves and produces a longer bud length than the cultivar Kenong9204 (KN9204). In this study, we investigated genes/metabolite activity changes in both types subjected to salt and control treatments using integrated transcriptomics and metabolomics analyses. By comparing data from the salt-treated plants with the control, 5161 (3235 upregulated and 1926 downregulated) and 211 (29 up and 182 downregulated) DEGs(Differentially Expressed Genes) were identified in the germination and seedling stage of CM6005. A total of 2061 (898 upregulated and 1163 downregulated) and 99 (84 upregulated and 15 downregulated) DEGs were identified in the germination and seedling stage of KN9204. CM6005's germination and seedling stage saw the identification of 792 (492 upregulated and 300 downregulated) and 2217 (1195 upregulated and 1032 downregulated) DAMs(Differentially Accumulated Metabolites), while KN9204's germination and seedling stage saw the identification of 1999 (997 upregulated and 1002 downregulated) and 1702 (860 upregulated and 842 downregulated) DAMs. The effects of salt stress on glycerolipid metabolism, phenylalanine metabolism, and glycerophospholipid metabolism were significantly modulated under salt treatments in the germination and seedling stages of CM6005 and KN9204, respectively, according to an integrated analysis of gene expression and metabolite profiles, assessment of metabolic pathways, and KEGG enrichment. Our findings showed that salt treatments caused stress-induced significant alterations in both transcriptomes and metabolomes. Wheat salt tolerance was regulated by key pathways linked to glycerolipid and phenylalanine metabolism, and these pathways serve as a crucial guide for growing wheat in saline soil. GRAS and MYB transcription factors might also regulate Glycerolipid metabolism and Phenylalanine metabolism.

Seed priming and exogenous application of citric acid enhance seedling growth and photosynthetic pigments and mitigate oxidative damage of soybean (Glycine max) under salt stress

Seed priming and citric acid (CA) supplementation on germination and seedling growth of soybeans were investigated. Soybean seeds were primed with distilled water (control), 1 mM CA (CA1), or 2 mM CA (CA2) and then placed for germination in Petri dishes containing distilled water or 150 mM NaCl (SS), alone or in combination with 1 mM or 2 mM CA. Germinated seeds were placed in hydroponic pots using a similar treatment regimen to that specified for the Petri dishes to obtain seedling growth and biochemical parameters. Salt stress significantly lowered germination, growth traits, relative water content (RWC), and photosynthetic pigment. When soybean seeds were primed with CA under salt stress, the germination rate, final germination percentage, seed vigor index, and number of lateral roots significantly increased. Moreover, supplementation of CA significantly increased fresh and dry shoot and root weight, plant height, RWC, and photosynthetic pigments compared to salt-treated plants. The results also displayed that salt stress considerably increased hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents compared to control plants. Spraying of CA1 and CA2 significantly lowered the levels of H2O2 and MDA in salt-treated plants. Both hierarchical clustering and PCA revealed that the effects of salt stress and CA on germination, growth characteristics, photosynthetic pigments, H2O2, and MDA concentrations strongly interacted with one another. According to the findings, CA could be applied as a seed priming and exogenous agent to help soybeans grow more quickly when exposed to salt stress.

Diverse responses of halophyte and glycophyte Lepidium species to the salt-mediated amelioration of nickel toxicity and accumulation.

Tolerance mechanisms employed by plants under environmental stresses can protect them against other co-occurring stresses. In this study, the effect of pre-exposure and simultaneous salt treatment on nickel (Ni) toxicity tolerance in one halophyte (L. sativum) and one glycophyte (L. latifolium) Lepidium species in hydroponics was investigated. In order to compare the species independent from their salt and Ni tolerance level, the glycophyte was subjected to lower salt and Ni concentrations and for a shorter period of time than the halophyte. Salt (NaCl) was applied at 50 and 100mM concentrations and Ni was provided at an equal free Ni2+ activity by adding 100 and 200µM Ni as single stresses, but 130 and 300µM Ni for the treatment of its combination with salt in the glycophyte and halophyte, respectively. Temporal analyses of signaling molecules revealed that the halophyte is characteristically different from the glycophyte in that it exhibits a higher constitutive level of nitric oxide and hydrogen peroxide, a longer duration of response to Ni, and its augmentation by salt. In addition to higher biomass and less Ni accumulation in salt-treated plants, the concentrations of free thiol groups, leaf pigments, proline, free and cell wall-bound phenolics contents, and the activity of phenolic metabolizing enzymes were higher in L. latifolium under the combined salt and Ni treatments than under the single Ni stress. In contrast, the biomass and most biochemical parameters of Ni-stressed L. sativum plants were not enhanced by salt treatment but rather decreased. Our findings shed light on cross-tolerance mechanisms in halophytes and uncovered halophyte survival strategies under multiple stresses.

OsTZF1, a CCCH-tandem zinc finger protein gene, driven under own promoter produces no pleiotropic effects and confers salt and drought tolerance in rice

ABSTRACT Different abiotic stresses induce OsTZF1, a tandem CCCH-type zinc finger domain gene, in rice. Here, we report that transgenic rice plants overexpressing OsTZF1 under own promoter (POsTZF1:OsTZF1-OX [for overexpression]) transferred to soil showed normal growth similar to vector control plants. The POsTZF1:OsTZF1-OX produced normal leaves without any lesion mimic phenotype and exhibited normal seed setting. The POsTZF1:OsTZF1-OX plants showed significantly increased tolerance to salt and drought stresses and enhanced post stress recovery. Microarray analysis revealed a total of 846 genes up-regulated and 360 genes down-regulated in POsTZF1:OsTZF1-OX salt-treated plants. Microarray analysis of POsTZF1:OsTZF1-OX plants showed the regulation of many abiotic stress tolerance genes. These results suggest that OsTZF1-OX under own promoter show abiotic stress tolerance and produces no pleiotropic effect on phenotype of transgenic rice plant.

Proteomics of Salt Gland-Secreted Sap Indicates a Pivotal Role for Vesicle Transport and Energy Metabolism in Plant Salt Secretion.

Soil salinization is one of the major factors restricting crop growth and agricultural production worldwide. Recretohalophytes have developed unique epidermal structures in their aboveground tissues, such as salt glands or salt bladders, to secrete excess salt out of the plant body as a protective mechanism from ion damage. Three hypotheses were proposed to explain how salt glands secrete salts: the osmotic hypothesis, a hypothesis similar to animal fluid transport, and vesicle-mediated exocytosis. However, there is no direct evidence to show whether the salt gland-secreted liquid contains landmark proteins or peptides which would elucidate the salt secretion mechanism. In this study, we collected the secreted liquid of salt glands from Limonium bicolor, followed by extraction and identification of its constituent proteins and peptides by SDS-PAGE and mass spectrometry. We detected 214 proteins and 440 polypeptides in the salt gland-secreted droplets of plants grown under control conditions. Unexpectedly, the proportion of energy metabolism-related proteins increased significantly though only 16 proteins and 35 polypeptides in the droplets of salt-treated plants were detected. In addition, vesicle transport proteins such as the Golgi marker enzyme glycosyltransferase were present in the secreted sap of salt glands from both control and salt-treated plants. These results suggest that trans-Golgi network-mediated vesicular transport and energy production contributes to salt secretion in salt glands.

A transcriptomic study reveals salt stress alleviation in cotton plants upon salt tolerant PGPR inoculation

Soil salinity is a major constraint for reducing crop productivity worldwide. To combat this situation, the current project was aimed to examine the effect of plant growth-promoting rhizobacteria (PGPR) inoculation on the growth of cotton ( Gossypium hirsutum, var. Jin668) plants during salt stress and to identify salt stress-responsive genes in cotton plants. For this purpose, two bacteria, Bacillus subtilis and Bacillus pumilus were selected among the 20 strains isolated from the cotton rhizosphere under the salt stress (200 mM NaCl) and identified by 16 S rRNA sequencing. B. subtilis and B. pumilus were applied to Jin668 plants under salt stress which enhanced resistance to salt stress (leaf and root growth) compared to only salt-treated plants and control plants. Transcriptomic analysis revealed 556 differentially expressed genes (481 up-regulated and 75 down-regulated) in the B. subtilis + Salt versus Salt treatments and 943 (536 up-regulated and 407 down-regulated) genes in the B. pumilus + Salt versus Salt treatments. KEGG analysis of B. pumilus + Salt versus Salt and B. pumilus + Salt versus Salt revealed the pathways plant-pathogen interaction and plant hormone signal transduction were expressed in both treatments, while ascorbate and aldarate metabolism pathways and glyoxylate and dicarboxylate metabolism pathways were uniquely expressed in the B. pumilus + Salt versus Salt comparison, and the pentose and glucuronate interconversions pathway was uniquely expressed in the B. pumilus + Salt treatment versus Salt comparison. These data showed that B. subtilis and B. pumilus significantly enhance salt stress tolerance in cotton plants during salt stress conditions. • Two Bacteria, Bacillus subtilis and Bacillus pumilus were selected from the cotton rhizosphere under the salt stress. • B. subtilis and B. pumilus were applied to cottonplants under salt stress which enhanced resistance to salt stress. • Transcriptomic analysis revealed 556 DEGs in the B.subtilis vs Salt and 943 DEGS in the B.pumilus vs Salt treatments. • KEGG analysis of B. subtilis and B. pumilus versus Salt revealed the variouspathways were expressed in both treatments. • In conclusion, B. subtilis and B. pumilus significantly enhancetolerance in cotton plants during salt stress conditions.

Response of Common Ice Plant (Mesembryanthemum crystallinum L.) to Sodium Chloride Concentration in Hydroponic Nutrient Solution

Common ice plant (Mesembryanthemum crystallinum L.) is a novel edible succulent plant with savory flavor. It has epidermal bladder cells (EBCs) that store water and sodium chloride (NaCl) located on the epidermis of the leaves and stems. Ice plant is an obligatory halophyte that requires NaCl for optimum growth. The objective of this study was to determine the impact of NaCl on growth of ice plant for hydroponic production as an edible leafy green and to quantify the ability of ice plant to take up NaCl from the environment. Four-week-old seedlings of ice plant were transplanted into hydroponic systems, established for 1 week, and given five NaCl treatments [0 M (control), 0.05 M, 0.10 M, 0.20 M, 0.40 M NaCl]. Sequential destructive harvests to determine plant growth occurred at day 7, 14, and 21 after NaCl treatment. The 0.05 M NaCl had the greatest stimulating effect on biomass, increasing total fresh weight (FW) by 173% and shoot FW by 193% compared with the control plants. The 0.10 M NaCl also had stimulating effect as compared with 0 M, but plants were not as large as those receiving 0.05 M NaCl. The 0.20 M NaCl had little effect on plant growth compared with the control. The 0.40 M NaCl had a strong stunting effect on plant growth. All plants treated with NaCl had less root weight than the control, and higher NaCl concentration resulted in greater reduction in root weight. However, for the 0.05 and 0.10 M treatment, the gain in shoot weight exceeded the loss in root weight. Plants gained or lost water in a faster rate than dry mass, which resulted in larger differences among treatments in FW than in dry weight (DW). Plants treated with higher NaCl concentrations developed fewer, smaller, and thicker leaves but contained more EBCs per unit leaf surface area. There was high Na and Cl accumulation in leaf tissues of all salt-treated plants (e.g., 180,507 mg·kg−1 Na and 125,084 mg·kg−1 Cl in the 0.05 M treatment vs. 13,558 mg·kg−1 Na and 12,991 mg·kg−1 Cl in the 0 M treatment). This indicated potential for bioremediation of saline soil or hydroponic water. Concentrations of macronutrients such as nitrogen (N), phosphorus (P), calcium (Ca), magnesium (Mg), and sulfur (S) were reduced when plants received increasing NaCl treatments. In general, this study showed that growth of ice plant benefited from 0.05 and 0.10 M NaCl additions to the hydroponic nutrient solution. Ice plant deserves further work on its ability to reduce Na and Cl from accumulating in recirculating hydroponic nutrient solution.

Fennel outperforms ajwain and anise in saline environment: physiological response mechanisms in germinating seeds and mature plants

The potential of different medicinal species as alternative crops for saline conditions needs to be explored. Comparative physiological responses of germinating seeds and mature plants of three genotypes of anise (Pimpinella anisum L.), fennel (Foeniculum vulgare Mill.), and ajwain (Trachyspermum ammi L.) to salt were studied in a 2-year field experiment using 0 and 100 mcM, and a laboratory experiment using 0, 25, 50, 75, 100, and 125 mM NaCl. Catalase and ascorbate peroxidase activities increased in the salt-stricken plants of all genotypes, but only peroxidase activity of the salt-treated plants of anise genotypes and two of the fennel genotypes increased under field conditions. Chlorophyll and K+ concentrations of all genotypes decreased, but proline and Na+ concentrations and Na+/K+ increased under saline conditions. Dry mass, grain yield, and essential oil yield decreased in the salt-exposed plants across all genotypes and species. Germination, root, and shoot length were suppressed upon exposure to saline water. Despite the increasing trend of the proline and polyphenol concentrations and catalase and peroxidases activities, ascorbate peroxidase activity of germinating seeds decreased with an increase in NaCl concentration. Smaller adverse effects of salt on fennel germination attributes, grain and essential oil yields were evident. Moreover, greater activities of antioxidative enzymes and maintained Na+ and Na+/K+ of salt-stricken fennel plants were observed. These findings indicate that germinating seeds and mature plants of fennel have a greater ability to withstand salinity than the other examined species.