Salt Stress In Wheat Seedlings Research Articles

Coating seeds with purified-hydrocolloids extracted from conventional activated sludge affects the growth physiology of wheat under gradient salt stress

With continuous innovations in wastewater treatment technology, the use of excess sludge has become a research focus. Purified-hydrocolloids obtained from aerobic granular sludge (AGS) and conventional activated sludge (CAS) have many practical applications, including waterproofing, adsorption, flame retardance, slow-release properties, and seed coating. In this study, purified-hydrocolloids extracted from CAS was used as a new seed coating, which was uniformly sprayed onto the surface of wheat seeds. Purified-hydrocolloids was most effective in resisting salt stress in wheat seedlings at a NaCl concentration of 125 mmol/L (soil salinity 2.74 g/Kg). The germination percentage, plant height, K+/Na+ ratio, soluble sugar and soluble protein contents of purified-hydrocolloids-coated seeds increased by 13.33 %, 46.32 %, 37.25 %, 8.89 %, and 36.22 %, respectively, compared with wheat seeds without purified-hydrocolloids coating. Inhibition of O2− production activity and malondialdehyde content was reduced by 38.62 % and 48.00 %, respectively. Therefore, the purified-hydrocolloids coating had a mitigating effect on wheat seed germination and seedling growth in salt-stressed environments, and this application would be beneficial to the use of saline soil resources and the improvement of ecosystems in coastal areas.

Physiological mechanism of sodium salicylate and folcisteine on alleviating salt stress in wheat seedlings

Soil salinization substantially hampers the growth and development of wheat, potentially leading to plant death in severe cases, thus reducing grain yield and quality. This phenomenon poses a significant threat to food security in China. We investigated the effects of two exogenous plant growth regulators, sodium salicylate and folcisteine, on the wheat physiology and key characteristics under salt stress using hydroponics method. The results indicated that both regulators effectively mitigated the growth inhibition of wheat under salt stress. We assessed morphological and physiological indexes, including antioxidant enzyme activities (superoxide dismutase [SOD], catalase [CAT], peroxidase [POD]) and malondialdehyde (MDA) concentration in wheat after foliar application of sodium salicylate and folcisteine under salt stress. The findings revealed that sodium salicylate was more effective than folcisteine. However, folcisteine showed superior performance in reducing hydrogen peroxide (H2O2) content and superoxide anion (O2−) level compared to sodium salicylate. Simultaneously, Concurrent application of both regulators synergistically enhanced their efficacy, yielding the most favorable outcomes. In addition, this study noted that while the initial effects of these regulators were not pronounced, their sustained application significantly improved wheat growth in stressful condition and alleviated the detrimental impacts of salt stress. This approach could effectively guarantee the food security and production in China.

Hydropriming with Moringa Leaf Extract Mitigates Salt Stress in Wheat Seedlings

Salinity is the major constraint that decreases the yield and production of crops. Wheat has a significant value in agricultural food commodities. The germination and growth of wheat seedlings are a big challenge in salt-affected soils. The seed priming technique is used to mitigate salt stress and enhance the germination and growth of the crops. Therefore, the current study was conducted to evaluate the hydropriming of natural plant extract (moringa leaf extract) and water on wheat seeds and grown under different saline (0, 0.05, 0.1, 0.15, and 0.2 M NaCl) environments. The germination attributes (germination percentage, germination index, mean germination day, coefficient of variance, vigor index) and seedling growth (fresh weight, dry weight, root length, shoot length) were enhanced in the plants primed by moringa leaf extract. The germination percentage was observed 10% more at 0.2 M NaCl stress in seeds treated with moringa leaf extract than seeds treated with water. The nutrient (K, Ca, Mg, P, S, Fe, B, Mn, Zn, Cu) uptake was also observed more in the shoots and roots of wheat seedlings soaked in moringa leaf extract as compared to soaked in water. Controlled plants showed higher concentrations of toxic ions (Na) and reactive oxygen species (H2O2) in shoots and roots of wheat seedlings. The use of moringa leaf extract for priming wheat seeds will enhance their germination and growth by maintaining efficient nutrient uptake and restricting the toxic ions and reactive oxygen species accumulation.

Exogenous hydrogen sulfide alleviates salt stress by improving antioxidant defenses and the salt overly sensitive pathway in wheat seedlings

Hydrogen sulfide (H2S) has the ability to strengthen plant stress tolerance; however, the effects of H2S on wheat seedlings under salt stress and the underlying molecular mechanism are still unclear. This study examined the effects of exogenous NaHS as H2S donor on photosynthesis, antioxidant system, and the expression profile of genes related to antioxidant defense responses, the salt overly sensitive (SOS) and mitogen-activated protein kinase (MAPK) pathways in wheat seedlings treated with NaCl stress. H2S application improved photosynthesis, and decreased H2O2 and malondialdehyde (MDA) contents in wheat seedling leaves under NaCl stress. In addition, antioxidant enzyme activity and the content of ascorbic acid and reduced glutathione increased with H2S application. Moreover, H2S pretreatment up-regulated expression levels of genes related to antioxidant system, SOS pathway and MAPK pathway as well as the transcription factor dehydration-responsive element binding gene. Overall, these findings suggest that H2S alleviates salt stress in wheat seedlings not only by strengthening antioxidant defense systems, but by coordinating signal transduction pathways related to the stress response at a transcriptional level.

ACCD-producing rhizobacteria from an Andean Altiplano native plant (Parastrephia quadrangularis) and their potential to alleviate salt stress in wheat seedlings

1-Aminocyclopropane-1-carboxylate deaminase (ACCD)-producing rhizobacteria are widely studied as plant growth-promoting rhizobacteria (PGPR) to alleviate a variety of stresses in plants. However, the presence of ACCD-producing rhizobacteria in plants that naturally occur in stressful ecosystems as well as the potential PGPR activity in agriculturally relevant plants has been poorly explored thus far. We isolated and characterized ACCD-producing rhizobacteria from Parastrephia quadrangularis, a native plant from the Andean Altiplano in Chile. The effects of selected ACCD-producing rhizobacteria on biomass and superoxide dismutase (SOD) activity of wheat seedlings subjected to salt stress (0.25 M and 0.45 M NaCl) were also evaluated. Ten out of 30 isolates showed ACCD activity (0.83–3.32 μmol α-ketobutyrate mg−1h−1) and were identified as members of the Enterobacteriales order (mainly Serratia and Klebsiella). The ACCD-producing rhizobacteria also showed salt tolerance (from 2.5 to 7.5% NaCl) and other PGPR traits, such as the production of auxin (from 20.3 to 41 μg mL−1) and siderophores (from 3.35 to 67.7%). Wheat seedlings inoculated with two selected ACCD-producing Klebsiella isolates (8LJA and 27IJA) significantly (P ≤ 0.05) increased the biomass (45–62%) content and SOD activity in roots (18–35%) with and without salt stress. This study demonstrated that PGPR were associated with native plants in the Andean Altiplano and offers a promising potential source of novel PGPR to alleviate salt stress in plants.

Melatonin Mitigates Salt Stress in Wheat Seedlings by Modulating Polyamine Metabolism.

Melatonin, a small molecular weight indoleamine molecule, is involved in various biological processes and responses to environmental cues in plants. However, its function in abiotic stress response and the underlying mechanisms is less clear. In this study, we investigated the effect of melatonin on wheat seedlings growth under salt stress condition. Exogenous melatonin pretreatment partially mitigated the salt-induced inhibition of whole-plant growth as judged from shoot dry weight, IAA content, leaf photosynthesis rate, maximum photochemistry efficiency of photosystem II, and chlorophyll. The mitigation was also observed in reduced accumulation of H2O2 in melatonin-pretreated wheat seedlings exposed to salt stress. Exogenous melatonin increased endogenous melatonin content by evaluating the levels of TaSNAT transcript, which encodes a key regulatory enzyme in the melatonin biosynthetic pathway. Furthermore, melatonin increased polyamine contents by accelerating the metabolic flow from the precursor amino acids arginine and methionine to polyamines; melatonin also decreased the degradation of salt-induced polyamines. Taken together, these results provide the evidence that melatonin mitigates salt stress mainly through its regulation on polyamine metabolism of wheat seedlings.

Exogenously applied poly-γ-glutamic acid alleviates salt stress in wheat seedlings by modulating ion balance and the antioxidant system.

Salt stress is a main abiotic stress that limits agricultural productivity in many parts of the world. To investigate whether poly-γ-glutamic acid (γ-PGA) can alleviate the negative effects of salt stress on wheat, a foliar application of 400mg/L γ-PGA was applied to wheat seedlings, which were then subjected to 150mM NaCl. Our results showed that after application of γ-PGA, the plant height, the plant weight, and the antioxidant enzymes including superoxide dismutase, peroxidase, and catalase were significantly increased compared with the treatment of 150mM NaCl alone. Meanwhile, γ-PGA application also resulted in high accumulation of K+ and decreased storage of Na+ in wheat leaves. These results suggest that γ-PGA treatment may improve salt tolerance of wheat by diminishing ionic imbalances and enhancing antioxidant capacity. Our results indicate that exogenous γ-PGA could alleviate the damage caused by salt stress.

Exogenous hydrogen sulfide alleviates salt stress in wheat seedlings by decreasing Na+ content

Hydrogen sulfide (H2S) is an important gaseous molecule in a number of plant developmental processes and stress responses. Triticum aestivum L. (LM 15) is a salt-sensitive wheat cultivar that was used here to examine the effect of exogenous H2S on seedling growth, Na+ and K+ concentration, and Na+ transportation under NaCl stress. The results showed that pretreatment with 0.05 mM sodium hydrosulfide (NaHS), a H2S donor, for 12 h significantly alleviated the growth inhibition of wheat seedlings under 100 mM NaCl. In addition, pretreatment with NaHS decreased the Na+ concentration, Na+/K+ ratio, the selective absorption capacity for K+ over Na+ and Na+ efflux ratio, and increased the selective transport capacity for K+ over Na+ under salt stress. Additional experiments with CaCl2 (an inhibitor of nonselective cation channels—NSCCs), TEA+ (an inhibitor of low affinity K+ transporter) or amiloride (an inhibitor of salt overly sensitive 1—SOS1) showed that NSCCs and SOS1 were the major pathways by which H2S reduced Na+ concentration in wheat seedlings. These results showed that exogenous H2S alleviated growth inhibition by maintaining a lower Na+ concentration in wheat seedlings under NaCl stress via the regulation of NSCCs and SOS1 pathways.

Zinc improves salt tolerance by increasing reactive oxygen species scavenging and reducing Na<sup>+</sup> accumulation in wheat seedlings

Salt decreases the uptake of Zn and other minerals and causes nutritional disorders in plants. Zn is an essential micronutrient for all organisms and it is reasonable to hypothesize that Zn status is essential for maintaining salt tolerance in plants. In this study, the physiological and molecular mechanisms of Zn-based alleviation of salt stress in wheat seedlings were investigated. Our results indicate that sufficient Zn nutrition maintained antioxidative enzyme activities and decreased a reactive oxygen species over-accumulation in wheat seedlings. Our data also reveal that sufficient Zn nutrition improved the expression of Na+/H+ antiporter genes, TaSOS1 and TaNHX1, thereby decreasing the Na+ accumulation and subsequently improving salt tolerance in wheat seedlings.

Mitigation of salt stress in wheat seedlings by halotolerant bacteria isolated from saline habitats

Eighty four halotolerant bacterial strains were isolated from the saline habitats and screened for growth at different NaCl concentrations. All grew well at 5% NaCl, but only 25% isolates showed growth at 20% NaCl concentration. Five strains SL3, SL32, SL35, J8W and PU62 growing well in 20% NaCl concentrations were further characterized for multiple plant growth promoting traits such as indole −3- acetic acid (IAA) production, HCN and siderophore production, ACC deaminase activity and P-solubilization. None were positive for HCN production and PCR amplification of acdS, the structural gene for ACC deaminase enzyme was found negative. 16S rRNA gene sequencing analysis of the five strains showed them to belong to two genera Bacillus and Hallobacillus. In vitro experiments showed that salt concentrations had significant inhibitory effects on development of seedlings but not on the growth of the bacterial strains. Inoculation of the 5 halotolerant bacterial strains to ameliorate salt stress (80 mM, 160 mM and 320 mM) in wheat seedlings produced an increase in root length of 71.7% in comparison with uninoculated positive controls. In particular, Hallobacillus sp. SL3 and Bacillus halodenitrificans PU62 showed more than 90% increase in root elongation and 17.4% increase in dry weight when compared to uninoculated wheat seedlings at 320 mM NaCl stress indicating a significant reduction of the deleterious effects of NaCl. These results indicate that halotolerant bacteria isolated from saline environments have potential to enhance plant growth under saline stress through direct or indirect mechanisms and would be most appropriate as bioinoculants under such conditions.

Alleviation of salt stress in wheat seedlings by mammalian sex hormones

Salinity is one of the most serious constraints facing agriculture today. Some mechanical, chemical and biological approaches are being pursued to cope with soil salinity. Although exogenously treated mammalian sex hormones (MSHs), progesterone, β-estradiol and androsterone, activate significant effects in various biological aspects in plants growing under normal conditions, there is no report investigating their effects on plants growing under salt stress. The present study aimed to investigate whether MSHs could alleviate the destructive effect of salt stress on wheat seedlings and thereby increase their salt tolerance. Wheat leaves were sprayed with 10(-6), 10(-8) and 10(-10) mol L(-1) concentrations of MSH on the ninth day after sowing. MSH-treated seedlings (10-day-old seedlings) were subjected to salt stress for 5 days (between days 10 and 15). At all the concentrations tested, MSH treatment provided a significant protection against to detrimental effects of salt stress in wheat seedlings. It improved dry weight, sugar, proline, protein, chlorophyll and glutathione contents in comparison to salinity alone. Similarly, superoxide dismutase, peroxidase, catalase, ascorbate peroxidase and nitrate reductase activities also were augmented by MSH treatment. On the other hand, increases in lipid peroxidation level, superoxide production and hydrogen peroxide content arising from salt treatment were reduced by MSH treatment. The highest salt tolerance was obtained at the concentrations of 10(-6) mol L(-1) for progesterone and 10(-8) mol L(-1) for β-estradiol and for androsterone. MSHs could be used effectively to protect wheat seedlings from the destructive effects of salt stress by stimulating both enzymatic and non-enzymatic antioxidant mechanism and by promoting levels of osmotic protectants such as proline and sugars resulting in osmotic adjustment, carbon storage and radical scavenging in plants.

Weak Microwave Can Enhance Tolerance of Wheat Seedlings to Salt Stress

The aim of our investigation was to determine the effect of microwave pretreatment of wheat seeds on the tolerance of seedlings to salt stress. Selected parameters (for example, plant growth and biochemical parameters related to oxidative status) were measured. The results showed that microwave pretreatments for 5, 10, 15, or 20 s resulted in an increase in root length and shoot height in seedlings, with 10- and 15-s treatments giving the greatest effect. Salt stress, produced by treatment with 200 mM NaCl, reduced the length and fresh weight of shoots and roots, enhanced the leaf concentrations of malondialdehyde (MDA) and oxidized glutathione (GSSG), indicators of oxidative stress, while decreasing the activities of nitric oxide synthase (NOS), catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and glutathione reductase (GR). Furthermore, the salt treatment reduced the concentration of nitric oxide (NO) and glutathione (GSH) in the shoots. However, treatments of seeds with microwave radiation followed by salt stress restored all of these parameters close to those in non-salt-treated seedlings. The results indicate that application of a suitable dose of microwave radiation to seeds can enhance tolerance to salt stress in wheat seedlings.

Antioxidant defense mechanism under salt stress in wheat seedlings

The present study was carried out to study the effect of salt stress on cell membrane damage, ion content and antioxidant enzymes in wheat (Triticum aestivum) seedlings of two cultivars salt-tolerant KRL-19 and salt-sensitive WH-542. Seedlings (4-d-old) were irrigated with 0, 50 and 100 mM NaCl. Observations were recorded on the 3rd and 6th day after salt treatment and 2nd day after salt removal. The relative water content declined with induction of salt stress, more in WH-542 than in cv. KRL-19. K+/Na+ ratio in KRL-19 was higher than in WH-542. WH-542 suffered greater damage to cellular membranes due to lipid peroxidation as indicated by higher accumulation of H2O2, MDA and greater leakage of electrolytes than KRL-19. The activities of catalase, peroxidase and ascorbate peroxidase and glutathione reductase increased with increase in salt stress in both the cultivars, however, superoxide dismutase activity declined. Upon desalanization, partial recovery in the activities of these enzymes was observed in KRL-19 and very slow recovery in WH-542.

Mitigation of salt stress in wheat seedlings by a gfp-tagged Azospirillum lipoferum

Root colonization and mitigation of NaCl stress on wheat seedlings were studied by inoculating seeds with Azospirillum lipoferum JA4∷ngfp15 tagged with the green fluorescent protein gene (gfp). Colonization of wheat roots under 80 and 160 mM NaCl stress was similar to root colonization with this bacterial species under non-saline conditions, that is, single cells and small aggregates were mainly located in the root hair zone. These salt concentrations had significant inhibitory effects on development of seedlings, but not on growth in culture of gfp-A. lipoferum JA4∷ngfp15. Reduced plant growth (height and dry weight of leaves and roots) under continuous irrigation with 160 mM NaCl was ameliorated by bacterial inoculation with gfp-A. lipoferum JA4∷ngfp15. Inoculation of plants subjected to continuous irrigation with 80 mM NaCl or to a single application of either NaCl concentration (80 or 160 mM NaCl) did not mitigate salt stress. This study indicates that, under high NaCl concentration, inoculation with modified A. lipoferum reduced the deleterious effects of NaCl; colonization patterns on roots were unaffected and the genetic marker did not induce undesirable effects on the interaction between the bacterium and the plants.