Silicon Improves Rice Salinity Resistance by Alleviating Ionic Toxicity and Osmotic Constraint in an Organ-Specific Pattern

Silicon mitigates salinity effects on sorghum-sudangrass (Sorghum bicolor × Sorghum sudanense) by enhancing growth and photosynthetic efficiency

The aim of this study was to investigate whether silicon (Si) supply was able to alleviate the harmful effects caused by salinity stress on sorghum-sudangrass (Sorghum bicolor ×Sorghum sudanense ), a species of grass raised for forage and grain. Plants were grown in the presence or absence of 150mM NaCl, supplemented or not with Si (0.5mM Si). Biomass production, water and mineral status, photosynthetic pigment contents, and gas exchange parameters were investigated. Special focus was accorded to evaluating the PSI and PSII. Salinity stress significantly reduced plant growth and tissue hydration, and led to a significant decrease in all other studied parameters. Si supply enhanced whole plant biomass production by 50%, improved water status, decreased Na+ and Cl- accumulation, and even restored chlorophyll a , chlorophyll b , and carotenoid contents. Interestingly, both photosystem activities (PSI and PSII) were enhanced with Si addition. However, a more pronounced enhancement was noted in PSI compared with PSII, with a greater oxidation state upon Si supply. Our findings confirm that Si mitigated the adverse effects of salinity on sorghum-sudangrass throughout adverse approaches. Application of Si in sorghum appears to be an efficient key solution for managing salt-damaging effects on plants.

Comparing the Potential of Silicon Nanoparticles and Conventional Silicon for Salinity Stress Alleviation in Soybean (Glycine max L.): Growth and Physiological Traits and Rhizosphere/Endophytic Bacterial Communities

In this study, 20-day-old soybean plants were watered with 100 mL of 100 mM NaCl solution and sprayed with silica nanoparticles (SiO2 NPs) or potassium silicate every 3 days over 15 days, with a final dosage of 12 mg of SiO2 per plant. We assessed the alterations in the plant's growth and physiological traits, and the responses of bacterial microbiome within the leaf endosphere, rhizosphere, and root endosphere. The result showed that the type of silicon did not significantly impact most of the plant parameters. However, the bacterial communities within the leaf and root endospheres had a stronger response to SiO2 NPs treatment, showing enrichment of 24 and 13 microbial taxa, respectively, compared with the silicate treatment, which led to the enrichment of 9 and 8 taxonomic taxa, respectively. The rhizosphere bacterial communities were less sensitive to SiO2 NPs, enriching only 2 microbial clades, compared to the 8 clades enriched by silicate treatment. Furthermore, SiO2 NPs treatment enriched beneficial genera, such as Pseudomonas, Bacillus, and Variovorax in the leaf and root endosphere, likely enhancing plant growth and salinity stress resistance. These findings highlight the potential of SiO2 NPs for foliar application in sustainable farming by enhancing plant-microbe interactions to improve salinity tolerance.

The adsorption-diffusion model and biomimetic simulation reveal the switchable roles of silicon in regulating toxic metal uptake in rice roots

Soil contamination by heavy metals has become a serious threat to global food security. The application of silicon (Si)-based materials is a simple and economical method for producing safe crops in contaminated soil. However, the impact of silicon on the heavy-metal concentration in plant roots, which are the first line in the chain of heavy-metal entering plants and causing stress and the main site of heavy-metal deposition in plants, remains puzzling. We proposed a process-based model (adsorption-diffusion model) to explain the results of a collection of 28 experiments on alleviating toxic metal stress in plants by Si. Then we evaluated the applicability of the model in Si-mitigated trivalent chromium (Cr[III]) stress in rice, taking into account variations in experimental conditions such as Cr(III) concentration, stress duration, and Si concentration. It was found that the adsorption-diffusion model fitted the experimental data well (R2 > 0.9). We also verified the binding interaction between Si and Cr in the cell wall using SEM-EDS and XPS. In addition, we designed a simplified biomimetic device that simulated the Si in cell wall to analyze the dual-action switch of Si from increasing Cr(III) adsorption to blocking Cr(III) diffusion. We found that the adsorption of Cr(III) by Si decreased from 58% to 7% as the total amount of Cr(III) increased, and finally the diffusion blocking effect of Si dominated. This study deepens our understanding of the role of Si in mitigating toxic metal stress in plants and is instructive for the research and use of Si-based materials to improve food security.

The Physiological and Molecular Mechanisms of Silicon Action in Salt Stress Amelioration

Salinity is one of the most common abiotic stress factors affecting different biochemical and physiological processes in plants, inhibiting plant growth, and greatly reducing productivity. During the last decade, silicon (Si) supplementation was intensively studied and now is proposed as one of the most convincing methods to improve plant tolerance to salt stress. In this review, we discuss recent papers investigating the role of Si in modulating molecular, biochemical, and physiological processes that are negatively affected by high salinity. Although multiple reports have demonstrated the beneficial effects of Si application in mitigating salt stress, the exact molecular mechanism underlying these effects is not yet well understood. In this review, we focus on the localisation of Si transporters and the mechanism of Si uptake, accumulation, and deposition to understand the role of Si in various relevant physiological processes. Further, we discuss the role of Si supplementation in antioxidant response, maintenance of photosynthesis efficiency, and production of osmoprotectants. Additionally, we highlight crosstalk of Si with other ions, lignin, and phytohormones. Finally, we suggest some directions for future work, which could improve our understanding of the role of Si in plants under salt stress.

Unveiling mechanisms of silicon-mediated resistance to chromium stress in rice using a newly-developed hierarchical system

Silicon (Si) has been well-known to enhance plant resistance to heavy-metal stress. However, the mechanisms by which silicon mitigates heavy-metal stress in plants are not clear. In particular, information regarding the role of Si in mediating resistance to heavy-metal stress at a single cell level is still lacking. Here, we developed a hierarchical system comprising the plant, protoplast, and suspension cell subsystems to investigate the mechanisms by which silicon helps to alleviate the toxic effects of trivalent chromium [Cr(III)] in rice. Our results showed that in whole-plant subsystem silicon reduced shoot Cr(III) concentration, effectively alleviating Cr(III) stress in seedlings and causing changes in antioxidant enzyme activities similar to those observed at lower Cr(III) concentrations without silicon added. However, in protoplast subsystem lacking the cell wall, no silicon deposition occurred, leading to insignificant changes in cell survival or antioxidation processes under Cr(III) stress. Conversely, in suspension cell subsystem, silicon supplementation substantially improved cell survival and changes in antioxidant enzyme activities under Cr(III) stress. This is due to the fact that >95% of silicon was on the cell wall, reducing Cr(III) concentration in cells by 7.7%-10.4%. Collectively, the results suggested that the silicon deposited on the cell wall hindered Cr(III) bio-uptake, which consequently delayed Cr(III)-induced changes in antioxidant enzyme activities. This research emphasizes the significance of cell walls in Si-alleviated heavy-metal stress and deepens our understanding of silicon functioning in plants. Furthermore, the hierarchical system has great potential for application in studying the functioning of other elements in plant cell walls.

Adsorption of Sodium Ions by Exopolysaccharides from Pseudomonas simiae MHR6 and Its Improvement of Na+/K+ Homeostasis in Maize under Salt Stress

Exopolysaccharides (EPS) are macromolecular substances with environmentally beneficial properties. At present, some reports have focused on the effects of EPS on plants salt stress; however, few studies have carried out a deeper characterization of the EPS components involved in Na+ binding. We investigated the mechanism of Na+ adsorption by Pseudomonas simiae MHR6 EPS and the regulation of ion homeostasis in maize under salt stress. The results showed that NaCl at 6% significantly inhibited MHR6 growth but enhanced EPS secretion. The chemical composition of the EPS varied in response to an increased NaCl concentration, and the proportion of polysaccharides was consistently higher than that of proteins. The highest Na+ adsorption was observed for 6% NaCl. The FTIR, SEM, and EDX results further indicated that EPS effectively biosorbed Na+. Furthermore, adding EPS improved Na+/K+ homeostasis in maize under salt stress. These results suggest that MHR6 EPS has potential for future development and utilization as a plant growth biostimulant in saline-alkali land.

Comparative effects of silicon and silicon nanoparticles on the antioxidant system and cadmium uptake in tomato under cadmium stress

Cadmium (Cd) pollution is an important threat to agricultural production globally. Silicon (Si) and silicon nanoparticles (Si NPs) can mitigate Cd stress in plants. However, the mechanisms underlying the impacts of Si and Si NPs on Cd resistance, particularly in low-Si accumulators, remain inadequately understood. Accordingly, we conducted a comparative investigation into the roles of Si and Si NPs in regulating the antioxidant system (enzymes and antioxidants) and Cd uptake (influx rate, symplastic and apoplastic pathways) in tomato (a typical low-Si accumulator). The results revealed that Si and Si NPs improved tomato growth under Cd stress, and principal component analysis (PCA) demonstrated that Si NPs were more effective than Si. For oxidative damage, redundancy analysis (RDA) results showed that Si NPs ameliorated oxidative damage in both shoots and roots, whereas Si predominantly alleviated oxidative damage in roots. Simultaneously, Si and Si NPs regulated antioxidant enzymes and nonenzymatic antioxidants with distinct targets and strengths. Furthermore, Si and Si NPs decreased Cd concentration in tomato shoot, root, and xylem sap, while Si NPs induced a more significant decline in shoot and xylem sap Cd. Noninvasive microtest and quantitative estimation of trisodium-8-hydroxy-1,3,6-pyrenetrisulfonic (PTS, an apoplastic tracer) showed that Si and Si NPs reduced the Cd influx rate and apoplastic Cd uptake, while Si NPs induced a more significant reduction. Moreover, Si regulated the expression of genes responsible for Cd uptake (NRAMP2 and LCT1) and compartmentalization (HMA3), while Si NPs reduced the expression of NRAMP2. In conjunction with RDA, the results showed that Si and Si NPs decreased Cd uptake mainly by regulating the symplastic and apoplastic pathways, respectively. Overall, our results indicate that Si NPs is more effective in promoting tomato growth and alleviating oxidative damage than Si in tomato under Cd stress by modulating the antioxidant system and reducing apoplastic Cd uptake.

Cobalt and Titanium Alleviate the Methylglyoxal-Induced Oxidative Stress in Pennisetum divisum Seedlings under Saline Conditions

Salinity is considered to be a global problem and a severe danger to modern agriculture since it negatively impacts plants' growth and development at both cellular- and whole-plant level. However, cobalt (Co) and titanium (Ti), multifunctional non-essential micro-elements, play a crucial role in improving plant growth and development under salinity stress. In the current study, Co and Ti impact on the morphological, biochemical, nutritional, and metabolic profile of Pennisetum divisum plants under three salinity levels which were assessed. Two concentrations of Co (Co-1; 15.0 mg/L and Co-2; 25.0 mg/L), and two concentrations of Ti (Ti-1; 50.0 mg/L and Ti-2; 100.0 mg/L) were applied as foliar application to the P. divisum plants under salinity (S1; 200 mM, S2; 500 mM, and S3; 1000 mM) stress. The results revealed that various morphological, biochemical, and metabolic processes were drastically impacted by the salinity-induced methylglyoxal (MG) stress. The excessive accumulation of salt ions, including Na+ (1.24- and 1.21-fold), and Cl- (1.53- and 1.15-fold) in leaves and roots of P. divisum, resulted in the higher production of MG (2.77- and 2.95-fold) in leaves and roots under severe (1000 mM) salinity stress, respectively. However, Ti-treated leaves showed a significant reduction in ionic imbalance and MG concentrations, whereas considerable improvement was shown in K+ and Ca2+ under salinity stress, and Co treatment showed downregulation of MG content (26, 16, and 14%) and improved the antioxidant activity, such as a reduction in glutathione (GSH), oxidized glutathione (GSSG), Glutathione reductase (GR), Glyoxalase I (Gly I), and Glyoxalase II (Gly II) by up to 1.13-, 1.35-, 3.75-, 2.08-, and 1.68-fold under severe salinity stress in P. divisum roots. Furthermore, MG-induced stress negatively impacted the metabolic profile and antioxidants activity of P. divisum's root and leaves; however, Co and Ti treatment considerably improved the biochemical processes and metabolic profile in both underground and aerial parts of the studied plants. Collectively, the results depicted that Co treatment showed significant results in roots and Ti treatment presented considerable changes in leaves of P. divism under salinity stress.

Silicon mitigates the negative impacts of salt stress in soybean plants

BACKGROUND

Soybean is widely cultivated around the world, including regions with salinity conditions. Salt stress impairs plant physiology and growth, but recent evidence suggests that silicon (Si) is able to mitigate this stressful condition. Therefore, the purpose of this study was to evaluate how different strategies of Si application impact on salt stress tolerance of an intermediate Si accumulator species (soybean). Therefore, we applied four treatments: Si-untreated plants (Si 0); foliar spraying at 20 mmol L^-1 (Si F); nutritive solution addition at 2.0 mol L^-1 (Si R), and combined foliar spraying at 20 mmol L^-1 plus nutritive solution at 2.0 mmol L^-1 (Si F + R). We investigated how Si application modified growth, leaf gas exchange, photosynthetic pigments, chlorophyll fluorescence, relative water content (RWC), nutrient accumulation, and ion homeostasis of soybean plants submitted to different levels of salt stress (50 and 100 mmol L^-1 NaCl).

RESULTS

Salinity induced an expressive reduction in ion accumulation, plant water status, and growth of soybean, while Si application promoted contrary effects and increased potassium (K⁺ ) accumulation, water status, photosynthetic pigment content, chlorophyll fluorescence parameters, and gas exchange attributes. Additionally, Si application enhanced Si accumulation associated with decreased Na⁺ uptake and improved morpho-physiological growth.

CONCLUSION

The use of exogenous Si can be an efficient strategy to attenuate the harmful effects of salt stress in soybean plants. The best application strategy was observed with combined foliar spraying with Si included in the nutritive solution (Si F + R). © 2023 Society of Chemical Industry.

Differential response of nano zinc sulphate with other conventional sources of Zn in mitigating salinity stress in rice grown on saline-sodic soil

Salinization causes the degradation of the soil and threatening the global food security but the application of essential micronutrients like zinc (Zn), improve the plant growth by stabilizing the plant cell and root development. Keeping in view the above-mentioned scenario, an experiment was conducted to compare the efficiency of conventional Zn fertilizers like zinc sulphate (ZnSO₄), zinc ethylene diamine tetra acetic acid (Zn-EDTA) and advance nano Zn fertilizers such as zinc sulphate nanoparticles (ZnSO₄NPs), and zinc oxide nanoparticles (ZnONPs) (applied at the rate of 5 and 10 mg/kg) in saline-sodic soil. Results revealed that the maximum plant height (67%), spike length (72%), root length (162%), number of tillers (71%), paddy weight (100%), shoot dry weight (158%), and root dry weight (119%) was found in ZnSO₄NPs applied at the rate of 10 mg/kg (ZnSO₄NPs-10) as compared to salt-affected control (SAC). Similarly, the plants physiological attributes like chlorophyll contents (91%), photosynthesis rate (113%), transpiration rate (106%), stomatal conductance (56%) and internal CO₂ (11%) were increased by the application of ZnSO₄NPs-10, as compared to SAC. The maximum Zn concentration in root (153%), shoot (205%) and paddy (167%) found in ZnSO₄NPs-10, as compared to control. In the body of rice plants, other nutrients like phosphorus and potassium were also increased by the application of ZnSO₄NPs-10 and soil chemical attributes such as sodium and sodium adsorption ratio were decreased. The current experiment concluded that the application of ZnSO₄NPs at the rate of 10 mg/kg in salt-affected paddy soil increased the growth, physiology, up take of essential nutrients and yield of rice by balancing the cationic ratio under salt stress.

Humic Acid Modulates Ionic Homeostasis, Osmolytes Content, and Antioxidant Defense to Improve Salt Tolerance in Rice

The sensitivity of rice plants to salinity is a major challenge for rice growth and productivity in the salt-affected lands. Priming rice seeds in biostimulants with stress-alleviating potential is an effective strategy to improve salinity tolerance in rice. However, the mechanisms of action of these compounds are not fully understood. Herein, the impact of priming rice seeds (cv. Giza 179) with 100 mg/L of humic acid on growth and its underlaying physiological processes under increased magnitudes of salinity (EC = 0.55, 3.40, 6.77, 8.00 mS/cm) during the critical reproductive stage was investigated. Our results indicated that salinity significantly reduced Giza 179 growth indices, which were associated with the accumulation of toxic levels of Na⁺ in shoots and roots, a reduction in the K⁺ and K⁺/Na⁺ ratio in shoots and roots, induced buildup of malondialdehyde, electrolyte leakage, and an accumulation of total soluble sugars, sucrose, proline, and enzymic and non-enzymic antioxidants. Humic acid application significantly increased growth of the Giza 179 plants under non-saline conditions. It also substantially enhanced growth of the salinity-stressed Giza 179 plants even at 8.00 mS/cm. Such humic acid ameliorating effects were associated with maintaining ionic homeostasis, appropriate osmolytes content, and an efficient antioxidant defense system. Our results highlight the potential role of humic acid in enhancing salt tolerance in Giza 179.

Organic Amendments Improved the Productivity and Bio-Fortification of Fine Rice by Improving Physiological Responses and Nutrient Homeostasis under Salinity Stress

Salinity stress (SS) is major abiotic stress that is seriously limiting crop production across the globe. The application of organic amendments (OA) mitigate the effects of salinity and improves soil health and crop production on a sustainable basis. However, limited studies are conducted to determine the impact of farmyard manure (FYM) and press mud (PM) on the performance of rice crop. Therefore, we performed this study to determine the impacts of FYM and PM on the growth, physiological and biochemical attributes, yield, and grain bio-fortification of rice crop under SS. The experiment was comprised of SS levels; control, 6 and 12 dS m^-1 SS and OA; control, FYM: 5%, press mud 5% and combination of FYM (5%) + PM (5%). Soil salinity imposed deleterious impacts on the growth, yield, and grain quality of rice, however, OA appreciably offset the deleterious impacts of SS and improved the growth, yield, and grain bio-fortification of rice crop. The combined application of FYM + PM improved the growth and yield of rice through an increase in chlorophyll contents, leaf water contents, anti-oxidant activities (ascorbate peroxidise: APX; catalase: CAT, peroxidise: POD and ascorbic acid: AsA), K⁺ accumulation and decrease in Na⁺/K⁺ ratio, electrolyte leakage, malondialdehyde (MDA), hydrogen peroxide (H₂O₂), Na⁺ accumulation. Moreover, the combined application of FYM + PM significantly improved the grain protein (5.84% and 12.90%), grain iron (40.95% and 42.37%), and grain zinc contents (36.81% and 50.93%) at 6 and 12 dS m^-1 SS. Therefore, this study suggested that the application of FYM and PM augmented the growth, yield, physiology, biochemistry, and grain bio-fortification of rice and proved to be a good practice for better rice production in salt-affected soils.

Silicon Actuates Poplar Calli Tolerance after Longer Exposure to Antimony

The presence of antimony (Sb) in high concentrations in the environment is recognized as an emerging problem worldwide. The toxicity of Sb in plant tissues is known; however, new methods of plant tolerance improvement must be addressed. Here, poplar callus (Populus alba L. var. pyramidallis) exposed to Sb(III) in 0.2 mM concentration and/or to silicon (Si) in 5 mM concentration was cultivated in vitro to determine the impact of Sb/Si interaction in the tissue. The Sb and Si uptake, growth, the activity of superoxide dismutase (SOD), catalase (CAT), guaiacol-peroxidase (G-POX), nutrient concentrations, and the concentrations of photosynthetic pigments were investigated. To elucidate the action of Si during the Sb-induced stress, the impact of short and long cultivations was determined. Silicon decreased the accumulation of Sb in the calli, regardless of the length of the cultivation (by approx. 34%). Antimony lowered the callus biomass (by approx. 37%) and decreased the concentrations of photosynthetic pigments (up to 78.5%) and nutrients in the tissue (up to 21.7%). Silicon supported the plant tolerance to Sb via the modification of antioxidant enzyme activity, which resulted in higher biomass production (increased by approx. 35%) and a higher uptake of nutrients from the media (increased by approx. 10%). Silicon aided the development of Sb-tolerance over the longer cultivation period. These results are key in understanding the action of Si-developed tolerance against metalloids.

Involvement of abscisic acid in silicon-mediated enhancement of copper stress tolerance in Artemisia annua

Heavy metal (HM) toxicity is a well-known hazard which causes deleterious impact on the growth and development of plants. The impact of abscisic acid (ABA) in presence of silicon (Si) on plant development and quality traits has largely gone unexplored. The effects of ABA and Si on the growth, yield, and quality characteristics of Artemisia annua L. plants growing under copper (Cu) stress (20 and 40 mg kg^-1) were investigated in a pot experiment. During this investigation, Cu stress caused severe damage to the plants but exogenous administration of Si and ABA ameliorated the harmful effects of Cu toxicity, and the plants displayed higher biomass and improved physio-biochemical attributes. Copper accumulated in the roots and shoots and its toxicity caused oxidative stress as demonstrated by the increased 2-thiobarbituric acid reactive substance (TBARS) content. It also resulted in the increased activity of antioxidant enzymes, however, the exogenous Si and ABA supplementation decreased the buildup of reactive oxygen species (ROS) and lipid peroxidation, alleviating the oxidative damage produced by HM stress. Copper toxicity had a considerable negative impact on glandular trichome density, ultrastructure as well as artemisinin production. However, combined Si and ABA enhanced the size and density of glandular trichomes, resulting in higher artemisinin production. Taken together, our results demonstrated that exogenous ABA and Si supplementation protect A. annua plants against Cu toxicity by improving photosynthetic characteristics, enhancing antioxidant enzyme activity, protecting leaf structure and integrity, avoiding excess Cu deposition in shoot and root tissues, and helping in enhanced artemisinin biosynthesis. Our results indicate that the combined application of Si and ABA improved the overall growth of plants and may thus be used as an effective approach for the improvement of growth and yield of A. annua in Cu-contaminated soils.

Sly-miR398 Participates in Cadmium Stress Acclimation by Regulating Antioxidant System and Cadmium Transport in Tomato (Solanum lycopersicum)

Cadmium (Cd) pollution is one of the major threats in agricultural production, and can cause oxidative damage and growth limitation in plants. MicroRNA398 (miR398) is involved in plant resistance to different stresses, and the post-transcriptional regulation of miR398 on CSDs plays a key role. Here, we report that miR398 was down-regulated in tomato in response to Cd stress. Simultaneously, CSD1 and SOD were up-regulated, with CSD2 unchanged, suggesting CSD1 is involved in miR398-induced regulation under Cd stress. In addition, the role of miR398 in Cd tolerance in tomato was evaluated using a transgenic line overexpressing MIR398 (miR398#OE) in which the down-expression of miR398 was disrupted. The results showed that Cd stress induced more significant growth inhibition, oxidative damage, and antioxidant enzymes disorder in miR398#OE than that in wild type (WT). Moreover, higher Cd concentration in the shoot and xylem sap, and net Cd influx rate, were observed in miR398#OE, which could be due to the increased Cd uptake genes (IRT1, IRT2, and NRAMP2) and decreased Cd compartmentalization gene HMA3. Overall, our results indicate that down-regulated miR398 plays a protective role in tomato against Cd stress by modulating the activity of antioxidant enzymes and Cd uptake and translocation.

Applied Selenium as a Powerful Antioxidant to Mitigate the Harmful Effects of Salinity Stress in Snap Bean Seedlings

Selenium (Se) plays several significant roles in regulating growth, development and plant responses to various abiotic stresses. However, its influence on sulfate transporters (SULTRS) and achieving the harmony with other salt-tolerance features is still limited in the previous literatures. This study elucidated the effect of Se supplementation (5, 10 and 20 µM) on salt-stressed (50 mM NaCl) snap bean seedlings. Generally, the results indicated that Se had dual effects on the salt stressed seedlings according to its concentration. At a low level (5 µM), plants demonstrated a significant improvement in shoot (13.8%) and root (22.8%) fresh weight, chlorophyll a (7.4%), chlorophyll b (14.7%), carotenoids (23.2%), leaf relative water content (RWC; 8.5%), proline (17.2%), total soluble sugars (34.3%), free amino acids (FAA; 18.4%), K (36.7%), Ca (33.4%), K/Na ratio (77.9%), superoxide dismutase (SOD; 18%), ascorbate peroxidase (APX;12.8%) and guaiacol peroxidase (G-POX; 27.1%) compared to the untreated plants. Meanwhile, most of these responses as well as sulfur (S), Se and catalase (CAT) were obviously decreased in parallel with increasing the applied Se up to 20 µM. The molecular study revealed that three membrane sulfate transporters (SULTR1, SULTR2 and SULTR 3) in the root and leaves and salinity responsive genes (SOS1, NHX1 and Osmotin) in leaves displayed different expression patterns under various Se treatments. Conclusively, Se at low doses can be beneficial in mitigating salinity-mediated damage and achieving the functioning homeostasis to tolerance features.

Silicon-Induced Mitigation of NaCl Stress in Barley (Hordeum vulgare L.), Associated with Enhanced Enzymatic and Non-Enzymatic Antioxidant Activities

Salt stress obstructs plant's growth by affecting metabolic processes, ion homeostasis and over-production of reactive oxygen species. In this regard silicon (Si) has been known to augment a plant's antioxidant defense system to combat adverse effects of salinity stress. In order to quantify the Si-mediated salinity tolerance, we studied the role of Si (200 ppm) applied through rooting media on antioxidant battery system of barley genotypes; B-10008 (salt-tolerant) and B-14011 (salt-sensitive) subjected to salt stress (200 mM NaCl). A significant decline in the accumulation of shoot (35-74%) and root (30-85%) biomass was observed under salinity stress, while Si application through rooting media enhancing biomass accumulation of shoots (33-49%) and root (32-37%) under salinity stress. The over-accumulation reactive oxygen species i.e., hydrogen peroxide (H2O2) is an inevitable process resulting into lipid peroxidation, which was evident by enhanced malondialdehyde levels (13-67%) under salinity stress. These events activated a defense system, which was marked by higher levels of total soluble proteins and uplifted activities of antioxidants enzymatic (SOD, POD, CAT, GR and APX) and non-enzymatic (α-tocopherol, total phenolics, AsA, total glutathione, GSH, GSSG and proline) in roots and leaves under salinity stress. The Si application through rooting media further strengthened the salt stressed barley plant's defense system by up-regulating the activities of enzymatic and non-enzymatic antioxidant in order to mitigate excessive H2O2 efficiently. The results revealed that although salt-tolerant genotype (B-10008) was best adopted to tolerate salt stress, comparably the response of salt-sensitive genotype (B-14011) was more prominent (accumulation of antioxidant) after application of Si through rooting media under salinity stress.

Assessing Silicon-Mediated Growth Performances in Contrasting Rice Cultivars under Salt Stress

Silicon (Si) application has great potential to improve salt tolerance in a variety of crop plants. However, it is unclear how Si influences the responses of contrasting rice cultivars when exposed to excessive salt. Here, we investigated the functions of Si in alleviating the negative effects of salt stress on two contrasting rice cultivars, namely BRRI dhan48 (salt-sensitive) and Binadhan-10 (salt-tolerant). Rice seedlings was pre-treated with three doses of Si (as silicic acid; 0, 1 and 2 mM) for 14 days at one-day interval before being exposed to salt stress (10 dSm⁻¹) in a sustained water bath system. The results demonstrated that the seedlings of BRRI dhan48 and Binadhan-10, respectively exhibited substantial reductions in shoot height (16 and 9%), shoot fresh weight (64 and 43%) and shoot dry weight (50 and 39%) under salinity. Intriguingly, BRRI dhan48 pre-treated with 1 and 2 mM Si, respectively, showed a higher increase in shoot height (SH) (by 25.90 and 26.08%) as compared with Binadhan-10 (by 3 and 8%) under salt stress compared with their respective controls. Data revealed that a comparatively higher improvement in the growth performances of the salt-induced Si pre-treated BRRI dhan48 than that of Binadhan-10. For example, 1 and 2 mM of Si treatments significantly attributed to elevated leaf relative water content (RWC) (13 and 22%), proline (138 and 165%), chlorophyll a (42 and 44%), chlorophyll b (91 and 72%), total chlorophyll (58 and 53%) and carotenoids (33 and 29%), and recovery in the reductions of electrolyte leakage (13 and 21%), malondialdehyde content (23 and 30%) and shoot Na⁺/K⁺ ratio (22 and 52%) in BRRI dhan48 compared with Si-untreated control plants under salt stress. In addition, we found salt-tolerant Binadhan-10 also had enhanced RWC (9 and 19%), proline (12 and 26%) with pre-treatment with 1 and 2 mM of Si, respectively, under salt stress, while no significant differences were noticed in the case of photosynthetic pigments and Na⁺/K⁺ ratio. Our results showed that Si supplementation potentiated higher salt-tolerance ability in the salt-sensitive BRRI dhan48 as compared with salt-tolerant Binadhan-10. Thus, Si application could be highly beneficial in the growth recovery of the salinity-affected salt-sensitive high yielding rice cultivars in the saline-prone areas.

TMT-based comparative proteomics reveals the role of acyl-CoA oxidase 4 in enhancing the drought stress tolerance in common buckwheat (Fagopyrum esculentum)

Drought stress has been the main abiotic factor affecting the growth, development and production of common buckwheat (Fagopyrum esculentum). To explore the response mechanisms of regulating buckwheat drought stress on the post-transcriptional and translational levels, a comparative proteomic analysis was applied to monitor the short-term proteomic variations under the drought stress in the seedling stage. From which 593 differentially abundant proteins (DAPs) were identified using the TMT-based proteomics analysis. A number of DAPs were found to be intimately correlated with the styrene degradation, phenylpropanoid biosynthesis and stimulus response, within which. The acyl-CoA oxidase 4 (ACX4), a key regulator in plant abiotic stress response, was selected for further elucidation. Overexpression of the FeACX4 not only conferred drought and salt tolerance in the Arabidopsis, but also significantly increased the root length and fresh weight in the overexpression lines plant relative to the wild type (WT) plant, accompanied by the elevated activities of catalase (CAT) and lowered malonaldehyde (MDA) and H₂O₂ contents, therefore allowing plants to better adapt to adverse environments. Our results provided information in the exploring of the molecular regulation mechanism responding to drought tolerance in common buckwheat.

Silicon improves ion homeostasis and growth of liquorice under salt stress by reducing plant Na+ uptake

Silicon (Si) effectively alleviates the effects of salt stress in plants and can enhance salt tolerance in liquorice. However, the mechanisms by which Si improved salt tolerance in liquorice and the effects of foliar application of Si on different liquorice species under salt stress are not fully understood. We investigated the effects of foliar application of Si on the growth, physiological and biochemical characteristics, and ion balance of two liquorice species, Glycyrrhiza uralensis and G. inflata. High salt stress resulted in the accumulation of a large amount of Na⁺, decreased photosynthetic pigment concentrations, perturbed ion homeostasis, and eventually inhibited both liquorice species growth. These effects were more pronounced in G. uralensis, as G. inflata is more salt tolerant than G. uralensis. Foliar application of Si effectively reduced the decomposition of photosynthetic pigments and improved gas exchange parameters, thereby promoting photosynthesis. It also effectively inhibited lipid peroxidation and leaf electrolyte leakage and enhanced osmotic adjustment of the plants. Furthermore, Si application increased the K⁺ concentration and reduced Na⁺ absorption, transport, and accumulation in the plants. The protective effects of Si were more pronounced in G. uralensis than in G. inflata. In conclusion, Si reduces Na⁺ absorption, improves ion balance, and alleviates the negative effects of salt stress in the two liquorice species studied, but the effect is species dependent. These findings may help to develop novel strategies for protecting liquorice plants against salt stress and provide a theoretical basis for the evaluation of salt tolerance and the scientific cultivation of liquorice.

Silicon enhanced the resistance of Chinese cabbage (Brassica rapa L. ssp. pekinensis) to ofloxacin on the growth, photosynthetic characteristics and antioxidant system

The negative impact of the misuse of antibiotics on agriculture and human health has become a popular research topic with the increasing usage of antibiotics; however, little information is available about the mechanisms of OFL (ofloxacin) and Si (silicon). In this experiment, we applied 7 OFL concentrations to two Chinese cabbage cultivars (Qinghua and Biyu) to screen proper OFL concentrations. OFL concentrations of 0, 1, 2.5 and 5 mg L-1 were selected for the subsequent test and 1.2 mmol L-1 Si was used as mitigation. The results showed that Biyu suffered more damage than Qinghua and the injury degree increased in a concentration-dependent manner. With increasing OFL concentrations, the photosynthetic fluorescence was weakened significantly; under 1, 2.5 and 5 mg L-1 OFL, the Pn reduced by 5.35%, 35.92% and 43.62% in Qinghua and 33.98%, 41.94% and 64.66% in Biyu, respectively. The production rate of O2-, H2O2 and the MDA content were increased and Biyu appeared higher increase rates. In addition, the antioxidant enzymes contents first increased and then decreased and that of Qinghua increased more than Biyu. Si ensured the growth under OFL and protected its photosynthetic ability. Under the OFL1+Si, OFL2.5 + Si and OFL5+Si treatments, Pn increased by 3.91%, 15.95 and 15.69% in Qinghua and 28.82%, 20.40% and 39.01% in Biyu. Si also maintained the structural integrity of leaf organelles and improved the scavenging ability of ROS by increasing the activity and relative gene expression of antioxidant enzymes. Moreover, varietal differences may play a more important role than Si.

MADS-box transcription factors determine the duration of temporary winter dormancy in closely related evergreen and deciduous Iris spp

Winter dormancy (WD) is a crucial strategy for plants coping with potentially deadly environments. In recent decades, this process has been extensively studied in economically important perennial eudicots due to changing climate. However, in evergreen monocots with no chilling requirements, dormancy processes are so far a mystery. In this study, we compared the WD process in closely related evergreen (Iris japonica) and deciduous (I. tectorum) iris species across crucial developmental time points. Both iris species exhibit a 'temporary' WD process with distinct durations, and could easily resume growth under warm conditions. To decipher transcriptional changes, full-length sequencing for evergreen iris and short read RNA sequencing for deciduous iris were applied to generate respective reference transcriptomes. Combining results from a multipronged approach, SHORT VEGETATIVE PHASE and FRUITFULL (FUL) from MADS-box was associated with a dormancy- and a growth-related module, respectively. They were co-expressed with genes involved in phytohormone signaling, carbohydrate metabolism, and environmental adaptation. Also, gene expression patterns and physiological changes in the above pathways highlighted potential abscisic acid and jasmonic acid antagonism in coordinating growth and stress responses, whereas differences in carbohydrate metabolism and reactive oxygen species scavenging might lead to species-specific WD durations. Moreover, a detailed analysis of MIKCCMADS-box in irises revealed common features described in eudicots as well as possible new roles for monocots during temporary WD, such as FLOWERING LOCUS C and FUL. In essence, our results not only provide a portrait of temporary WD in perennial monocots but also offer new insights into the regulatory mechanism underlying WD in plants.

The Ability of Silicon Fertilisation to Alleviate Salinity Stress in Rice is Critically Dependent on Cultivar

Silicon (Si) fertiliser can improve rice (Oryza sativa) tolerance to salinity. The rate of Si uptake and its associated benefits are known to differ between plant genotypes, but, to date, little research has been done on how the benefits, and hence the economic feasibility, of Si fertilisation varies between cultivars. In this study, a range of rice cultivars was grown both hydroponically and in soil, at different levels of Si and NaCl, to determine cultivar variation in the response to Si. There was significant variation in the effect of Si, such that Si alleviated salt-induced growth inhibition in some cultivars, while others were unaffected, or even negatively impacted. Thus, when assessing the benefits of Si supplementation in alleviating salt stress, it is essential to collect cultivar-specific data, including yield, since changes in biomass were not always correlated with those seen for yield. Root Si content was found to be more important than shoot Si in protecting rice against salinity stress, with a root Si level of 0.5-0.9% determined as having maximum stress alleviation by Si. A cost-benefit analysis indicated that Si fertilisation is beneficial in mild stress, high-yield conditions but is not cost-effective in low-yield production systems.

A Global Metabolic Map Defines the Effects of a Si-Based Biostimulant on Tomato Plants under Normal and Saline Conditions

The ongoing unpredictability of climate changes is exponentially exerting a negative impact on crop production, further aggravating detrimental abiotic stress effects. Several research studies have been focused on the genetic modification of crop plants to achieve more crop resilience against such stress factors; however, there has been a paradigm shift in modern agriculture focusing on more organic, eco-friendly and long-lasting systems to improve crop yield. As such, extensive research into the use of microbial and nonmicrobial biostimulants has been at the core of agricultural studies to improve crop growth and development, as well as to attain tolerance against several biotic and abiotic stresses. However, the molecular mechanisms underlying the biostimulant activity remain enigmatic. Thus, this study is a liquid chromatography-mass spectrometry (LC-MS)-based untargeted metabolomics approach to unravel the hypothetical biochemical framework underlying effects of a nonmicrobial biostimulant (a silicon-based formulation) on tomato plants (Solanum lycopersium) under salinity stress conditions. This metabolomics study postulates that Si-based biostimulants could alleviate salinity stress in tomato plants through modulation of the primary metabolism involving changes in the tricarboxylic acid cycle, fatty acid and numerous amino acid biosynthesis pathways, with further reprogramming of several secondary metabolism pathways such as the phenylpropanoid pathway, flavonoid biosynthesis pathways including flavone and flavanol biosynthesis. Thus, the postulated hypothetical framework, describing biostimulant-induced metabolic events in tomato plants, provides actionable knowledge necessary for industries and farmers to, confidently and innovatively, explore, design, and fully implement Si-based formulations and strategies into agronomic practices for sustainable agriculture and food production.

Soil Salinity, a Serious Environmental Issue and Plant Responses: A Metabolomics Perspective

The effects of global warming have increasingly led to devastating environmental stresses, such as heat, salinity, and drought. Soil salinization is a serious environmental issue and results in detrimental abiotic stress, affecting 7% of land area and 33% of irrigated lands worldwide. The proportion of arable land facing salinity is expected to rise due to increasing climate change fuelled by anthropogenic activities, exacerbating the threat to global food security for the exponentially growing populace. As sessile organisms, plants have evolutionarily developed mechanisms that allow ad hoc responses to salinity stress. The orchestrated mechanisms include signalling cascades involving phytohormones, kinases, reactive oxygen species (ROS), and calcium regulatory networks. As a pillar in a systems biology approach, metabolomics allows for comprehensive interrogation of the biochemistry and a deconvolution of molecular mechanisms involved in plant responses to salinity. Thus, this review highlights soil salinization as a serious environmental issue and points to the negative impacts of salinity on plants. Furthermore, the review summarises mechanisms regulating salinity tolerance on molecular, cellular, and biochemical levels with a focus on metabolomics perspectives. This critical synthesis of current literature is an opportunity to revisit the current models regarding plant responses to salinity, with an invitation to further fundamental research for novel and actionable insights.

Seed Priming with Silicon as a Potential to Increase Salt Stress Tolerance in Lathyrus odoratus

Water shortage is a major problem limiting the expansion of green areas and landscapes. Using seawater as an alternative source of potable water is not a novel idea, but the issue of salt stress needs to be resolved. Salinity has a negative impact on growth and the aesthetic value of ornamental plants. In order to overcome these challenges, Lathyrus odoratus seeds were hydro-primed and halo-primed with silicon (Si) and silicon nanoparticles (SiNPs), and exposed to seawater levels. Seawater markedly reduced seed germination and growth of Lathyrus seedlings, but halo-priming was shown to significantly alleviate its negative effects. Broadly, SiNPs increased the germination percentage, reduced photosynthetic pigments and carbohydrates decrease, and enhanced water relations, despite having a negative effect on germination speed. Halo-priming significantly increased the proline content and the activities of certain enzymatic (SOD, APX and CAT) and nonenzymatic (phenolic and flavonoids) compounds, that positively influenced oxidative stress (lower MDA and H₂O₂ accumulation), resulting in seedlings with more salt stress tolerance. Halo-priming with Si or SiNPs enhanced the Si and K⁺ contents, and K⁺/Na⁺ ratio, associated with a reduction in Na⁺ accumulation. Generally, halo-priming with Si or SiNPs increased Lathyrus seedlings salt stress tolerance, which was confirmed using seawater treatments via improving germination percentage, seedlings growth and activation of the antioxidant machinery, which detoxifies reactive oxygen species (ROS).

Silicon augments salt tolerance through modulation of polyamine and GABA metabolism in two indica rice (Oryza sativa L.) cultivars

Polyamines (PA) have multifarious roles in plant-environment interaction and stress responses. In conjunction with GABA shunt, they regulate induction of tolerance under salinity stress in plants. Here, we tested the hypothesis that silicon improves salt tolerance through mediating vital metabolic pathways rather than acting as a mere mechanical barrier. Seedlings of two rice (Oryza sativa L.) cultivars MTU 1010 (salt-sensitive) & Nonabokra (salt-tolerant) growing in hydroponic culture were treated with NaCl (0, 25, 50 & 100 mM) combined with or without Si (2 mM). NaCl stress enhanced PA synthesizing enzymes activity and PA production in salt tolerant cultivar Nonabokra, whereas in the sensitive cultivar, MTU 1010 both declined. Enhanced activities of GABA synthesizing enzymes along with a decline in the activities of GABA degrading enzymes under NaCl exposure led to GABA accumulation in both the cultivars. The interactive effects of silicon and NaCl also induced the activities of the enzymes related to polyamine biosynthesis and inhibited polyamine degrading enzymes that enhanced PA contents in the cultivars. Supplemental Si decreased endogenous GABA levels by modulating GABA metabolising enzymes under NaCl stress. On the basis of all tested parameters cv. MTU 1010 was proven to be more responsive towards silicon application than cv. Nonabokra. Such study of silicon-induced polyamine accretion and reduced GABA accumulation may lower oxidative damage in rice cultivars under NaCl stress and thereby form a successful strategy to boost tolerance.

Coumarin improves tomato plant tolerance to salinity by enhancing antioxidant defence, glyoxalase system and ion homeostasis

Salinity is a severe threat to crop growth, development and even to world food sustainability. Plant possess natural antioxidant defense tactics to mitigate salinity-induced oxidative stress. Phenolic compounds are non-enzymatic antioxidants with specific roles in protecting plant cells against stress-mediated reactive oxygen species (ROS) generation. Coumarin (COU) is one of these compounds, however, to date, little is known about antioxidative roles of exogenous COU in enhancing plant tolerance mechanisms under salt stress. The involvement of COU in increasing tomato salt tolerance was examined in the present study using COU as a pre-treatment at 20 or 30 µM for 2 days against salt stress (100 or 160  NaCl; 5 days). The COU-mediated stimulation of plant antioxidant defence and glyoxalase systems to suppress salt-induced ROS and methylglyoxal (MG) toxicity, respectively, were the main hypotheses examined in the present study. Addition of COU suppressed salt-induced excess accumulation of ROS and MG, and significantly reduced membrane damage, lipid peroxidation and Na⁺ toxicity. These results demonstrate COU-improved plant growth, biomass content, photosynthetic pigment content, water retention and mineral homeostasis upon imposition of salinity. Finally, this present study suggests that COU has potential roles as a phytoprotectant in stimulating plant antioxidative mechanisms and improving glyoxalase enzyme activity under salinity stress.

Silicon Stimulates Plant Growth and Metabolism in Rice Plants under Conventional and Osmotic Stress Conditions

Exogenous silicon (Si) can enhance plant resistance to various abiotic factors causing osmotic stress. The objective of this research was to evaluate the application of 1 and 2 mM Si to plants under normal conditions and under osmotic stress. Morelos A-98 rice seedlings, were treated with 1 and 2 mM SiO2 for 28 d. Subsequently, half of the plants were subjected to osmotic stress with the addition of 10% polyethylene glycol (PEG) 8000; and continued with the addition of Si (0, 1 and 2 mM SiO2) for both conditions. The application of Si under both conditions increased chlorophyll b in leaves, root volume, as well as fresh and dry biomass of roots. Interestingly, the number of tillers, shoot fresh and dry biomass, shoot water content, concentration of total chlorophyll, chlorophyll a/b ratio, and the concentration of total sugars and proline in shoot increased with the addition of Si under osmotic stress conditions. The addition of Si under normal conditions decreased the concentration of sugars in the roots, K and Mn in roots, and increased the concentration of Fe and Zn in shoots. Therefore, Si can be used as a potent inorganic biostimulant in rice Morelos A-98 since it stimulates plant growth and modulates the concentration of vital biomolecules and essential nutrients.

Silicon alleviates salt stress-induced potassium deficiency by promoting potassium uptake and translocation in rice (Oryza sativa L.)

Under salt stress, plants suffer from potassium (K) deficiency caused by excess salts in growth substrate. Silicon (Si) can promote K status in many plant species under salt stress, however, the underlying mechanisms remain unclear. In this study, we assessed the effects of Si on K homeostasis in rice under salt stress and investigated the mechanisms behind using two low-Si rice mutants (lsi1 and lsi2) and their wild types (WTs). After five days' treatment with Si, plant growth was improved and salt stress-induced K deficiency was alleviated in WTs but not in mutants. Simultaneously, Si significantly enhanced K accumulation content, K uptake index and shoot K distribution rate in WTs but not in mutants. Besides, Si enhanced K concentration in xylem sap in WTs but not in mutants. Scanning ion-selected electrode technique (SIET) analysis showed net K influx rate was raised by Si addition under salt stress in WTs but not in mutants. Moreover, Si up-regulated the expression of genes responsible for K uptake (OsAKT1 and OsHAK1) and xylem loading (OsSKOR) in WTs but not in mutants. Overall, our results strongly indicate that Si can improve K uptake and translocation by up-regulating the expression of relevant genes, thereby promoting K status and alleviating salt stress in rice.

Silicon alleviates salinity stress in licorice (Glycyrrhiza uralensis) by regulating carbon and nitrogen metabolism

Salt stress is one of the key factors that limits the cultivation of Glycyrrhiza uralensis Fisch. (G. uralensis) in the northern part of China. In this study, three salt treatments (including 21, 42 and 63 ds/m NaCl/kg dry soil) and four Si (silicon) concentrations (including 0, 1.4, 2.8 and 4.2 ds/m SiO₂/kg K₂SiO₃ in dry soil) were tested using G. uralensis as the plant material in a pot experiment with three replications. The results showed that the application of various concentrations of Si increased sucrose synthetase (SS), sucrose phosphate synthetase (SPS) and glutamine synthetase (GS), as well as nitrate reductase (NR) activities, and promoted carbon and nitrogen metabolism. Si application also increased the root dry weight of G. uralensis. Multilevel comparative analysis showed that the application of 2.8 ds/m SiO₂ was the optimum rate for improved growth and yield of G. uralensis under different salt levels. This study provides important information that can form the basis for the cultivation of high-yielding and high-quality G. uralensis in saline soils.

Ameliorative role of Bacillus subtilis FBL-10 and silicon against lead induced stress in Solanum melongena

The continuous deterioration of arable lands by metal pollution compels finding suitable strategies to increase plant tolerance under contaminated regimes. Current study was designed to examine the synergistic role of Bacillus subtilis FBL-10 and silicon (Si) with respect to mitigation of lead (Pb) induced phytotoxicity in Solanum melongena L. Lead stress (75 mg kg^-1) reduced chlorophyll (Chl) content, photosynthetic rate and gas exchange characteristics of S. melongena plants. The Si and B. subtilis FBL-10 individually upgraded all the above-mentioned growth attributes. However, co-application of Si (50 mg kg^-1) and B. subtilis FBL-10 significantly improved biochemical and growth attributes of Pb challenged plants. The abridged levels of oxidative markers including hydrogen peroxide (H₂O₂), and malondialdehyde (MDA) besides reduced Pb accumulation in foliage tissues, were recorded in Si and microbe assisted plants. Furthermore, plants inoculated with B. subtilis FBL-10 alone or in combination with Si showed increment in total soluble proteins, photosynthetic rate and gas exchange attributes. The inoculated plants treated with Si exhibited higher level of auxins and improved activity of antioxidant enzymes under Pb stress. Present research elucidates interactive role of B. subtilis FBL-10 and Si in reduction of Pb toxicity in S. melongena plants. Alone application of Si or B. subtilis FBL-10 was less effective for attenuation of Pb stress; however, synergism between both phyto-protectants demonstrated fabulous ability for Pb stress assuagement. Consequently, executions of field studies become indispensable to comprehend the efficacy of Si applied alone or in combination with plant growth promoting bacteria (PGPB) like B. subtilis FBL-10. From current research, it is concluded that the interaction of Si and PGPB seems an auspicious technique and eco-friendly approach to enhance metal tolerance in crop plants.

Silicon mediated improvement in the growth and ion homeostasis by decreasing Na+ uptake in maize (Zea mays L.) cultivars exposed to salinity stress

Silicon (Si), a major contributing constituent for plant resistance against abiotic stresses. In spite of this, the detailed mechanisms underlying the potential of Si in mitigating salt toxicity in maize (Zea mays L.) are still poorly understood. The present study deals with the response of Si application on growth, gaseous exchange, ion homeostasis and antioxidant enzyme activities in two maize cultivars (P1574 and Hycorn 11) grown under saline conditions. Salt stress remarkably reduced the plant tissue (roots and shoots) biomass, relative water contents (RWC), membrane stability index (MSI), gaseous exchange characteristics, and antioxidant enzymatic activities i.e., superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX) and catalase (CAT). However, salt-induced phytotoxicity increased the plant tissue concentration of malondialdehyde (MDA), hydrogen peroxide (H₂O₂), Na⁺/K⁺ ionic ratio, Na⁺ translocation (root to shoot), and its uptake. The detrimental effects were more prominent in Hycorn 11 cultivar than the P1574 cultivar at higher salinity level (S2; 160 mM NaCl). The addition of Si alleviated salt toxicity, which was more obvious in P1574 relative to Hycorn 11 as demonstrated by an increasing trend in RWC, MSI, and activities of SOD, POD, APX and CAT. Besides, Si-induced mitigation of salt stress was due to the depreciation in Na⁺/K⁺ ratio, Na⁺ ion uptake at the surface of maize roots, translocation in plant tissues and thereby significantly reduced Na⁺ ion accumulation. The findings showed a new dimension regarding the beneficial role of Si in maize plants grown under salt toxicity.