Si Treatment Research Articles

In vitro and in vivo Evaluations of the Antifungal Activity of Salicylic Acid and Silicon Against Ganoderma Boninense

Basal stem rot disease (BSR) in oil palms is one of the primary diseases that has led to the wide use of fungicides. This increased the development of fungal isolates resistant to fungicides and led to the search for alternative strategies to replace the use of fungicides. This study aimed to evaluate in vitro antifungal activity of salicylic acid (SA) and silicon (Si) in inhibiting mycelial growth of Ganoderma boninense using Poison Food Technique and to evaluate the in vivo efficacy of Si treatment on oil palm seedlings growth and resistance towards G. boninense. Percentage inhibition of radial mycelial growth (PIRG) was assessed, and Si treatment significantly reduced mycelial radial growth of G. boninenseup to 100% inhibition at concentrations of 200 and 250 mg/L. The half-maximal effective concentration (EC50) for Si was 68.57 mg/L, while for SiO2, it was 273.95 mg/L. The EC50 for salicylic acid was 381.33 mg/L. For in vivo evaluation, oil palm seedlings treated with Si at 150, 200, and 250 mg/L showed the lowest severity of leaf chlorosis and necrotic symptoms, which were 7.36%, 6.49%, and 4.05%, respectively. In contrast, the seedlings without Si showed the highest severity of leaf symptoms. Examination of internal bole tissues of oil palm seedlings treated with Si at a concentration of 250 mg/L also recorded a 3.0% mean percentage of disease severity compared to the untreated infected seedlings, which showed 35.0% disease severity. Our findings demonstrated the potential of Si application in controlling the BSR disease caused by Ganoderma boninense.

Silicon alleviates the toxicity of microplastics on kale by regulating hormones, phytochemicals, ascorbate-glutathione cycling, and photosynthesis

Kale is rich in various essential trace elements and phytochemicals, including glucosinolate and its hydrolyzed product isothiocyanate, which have significant anticancer properties. Nowadays, new types of pollutant microplastics (MP) pose a threat to global ecosystems due to their high bioaccumulation and persistent degradation. Silicon (Si) is commonly used to alleviate abiotic stresses, offering a promising approach to ensure safe food production. However, the mechanisms through which Si mitigates MP toxicity are unknown. In this study, a pot culture experiments was conducted to evaluate the morphogenetic, physiological, and biochemical responses of kale to Si supply under MP stress. The results showed that MP caused the production of reactive oxygen species, inhibited the growth and development of kale, and reduced the content of phytochemicals by interfering with the photosynthetic system, antioxidant defense system, and endogenous hormone regulation network. Si mitigated the adverse effects of MP by enhancing the photosynthetic capacity of kale, regulating the distribution of substances between primary and secondary metabolism, and strengthening the ascorbate-glutathione (AsA-GSH) cycling system. SummaryEffects of microplastic and silicon on key indicators of kale. Note: The red arrows and blue arrows indicate the MP treatment effect compared to the control and Si treatment effect compared to the MP treatment, respectively.

Silicon Modifies Photosynthesis Efficiency and hsp Gene Expression in European Beech (Fagus sylvatica) Seedlings Exposed to Drought Stress.

Background: Climate change is leading to severe and long-term droughts in European forest ecosystems. can have profound effects on various physiological processes, including photosynthesis, gene expression patterns, and nutrient uptake at the developmental stage of young trees. Objectives: Our study aimed to test the hypothesis that the application of silica (SiO2) influences photosynthetic efficiency and gene expression in 1- to 2-year-old Fagus sylvatica (L.) seedlings. Additionally, we aimed to assess whether silicon application positively influences the structural properties of leaves and roots. To determine whether the plant physiological responses are genotype-specific, seedlings of four geographically different provenances were subjected to a one-year evaluation under greenhouse conditions. Methods: We used the Kruskal-Wallis test followed by Wilcoxon's test to evaluate the differences in silicon content and ANOVA followed by Tukey's test to evaluate the physiological responses of seedlings depending on treatment and provenance. Results: Our results showed a significantly higher Si content in the roots compared with the leaves, regardless of provenance and treatment. The most significant differences in photosynthetic performance were found in trees exposed to Si treatment, but the physiological responses were generally nuanced and provenance-dependent. Expression of hsp70 and hsp90 was also increased in leaf tissues of all provenances. These results provide practical insights that Si can improve the overall health and resilience of beech seedlings in nursery and forest ecosystems, with possible differences in the beneficial role of silicon application arising from the large differences in wild populations of forest tree species.

Characterization and function of promoters of silicon transporter genes PeLsi1-1 and PeLsi1-2 from moso bamboo (Phyllostachys edulis).

Promoters of moso bamboo silicon transporter genes PeLsi1-1 and PeLsi1-2 contain elements in response to hormone, silicon, and abiotic stresses, and can drive the expression of PeLsi1-1 and PeLsi1-2 in transgene Arabidopsis. Low silicon 1 (Lsi1) transporters from different species have been shown to play an important role in influxing silicon from soil. In previous study, we cloned PeLsi1-1 and PeLsi1-2 from Phyllostachys edulis and verified that PeLsi1-1 and PeLsi1-2 have silicon uptake ability. Furthermore, in this study, the promoters of PeLsi1-1(1910bp) and PeLsi1-2(1922bp) were cloned. Deletion analysis identified the key regions of the PeLsi1-1 and PeLsi1-2 promoters in response to hormone, silicon, and abiotic stresses. RT-qPCR analysis indicated that PeLsi1-1 and PeLsi1-2 were regulated by hormones, salt stress and osmotic stress. In addition, we found that the driving activity of the PeLsi1-1 and PeLsi1-2 promoters was regulated by 2mM K2SiO3 and PeLsi1-1-P3 ~ P4 and PeLsi1-2-P4 ~ 5 were the regions regulated by silicon. Overexpression of PeLsi1-1 or PeLsi1-2 driven by 35S promoter in Arabidopsis resulted in a threefold increase of Si accumulation, whereas transgenic plants showed deleterious symptoms and dwarf seedlings and shorter roots under 2mM Si treatment. When the 35S promoter was replaced by PeLsi1-1 or PeLsi1-2 promoter, a similar Si absorption was achieved and the transgene plants grew normally. This study, therefore, demonstrates that the promoters of PeLsi1-1 and PeLsi1-2 are indeed effective in driving the expression of moso bamboo Lsi1 genes and leading to silicon uptake.

Mechanism of Bacillus pumilus cooperating with silicon to restore carbon metabolism of Glycyrrhiza uralensis Fisch. seedlings exposed to drought stress

Glycyrrhiza uralensis Fisch, widely used in traditional medicine, tobacco flavoring, and food sweetening, faces growth challenges due to drought stress in arid regions. Plant growth-promoting bacteria (PGPB) and silicon (Si) have emerged as effective solutions to mitigate drought effects by enhancing photosynthesis and balanced carbon metabolism, promoting plant growth. This study investigates the impact of Bacillus pumilus (G5), Si, and G5+Si on the carbon metabolism of G. uralensis seedlings under drought stress. Drought stress was induced by maintaining soil moisture at 35∼45 % saturation, and seedlings were treated with G5 (108 CFU mL−1), Si (2 mM), and both (D+G5, D+Si, D+G5+Si). Results showed that both G5 and Si treatments enhanced carbon metabolism, with the combined G5+Si treatment showing a synergistic effect. Specifically, G5+Si increased chlorophyll levels, boosting photosynthesis and promoting soluble sugar accumulation. This treatment also maintained carbohydrate balance by modulating starch and sucrose metabolism and improved energy conversion by activating glycolysis (EMP) and the pentose phosphate pathway (PPP). Additionally, G5+Si stimulated energy generation by accelerating the tricarboxylic acid (TCA) cycle, enhancing plant growth, and increasing biomass. These findings highlight the synergistic role of G5 and Si in enhancing the drought resilience of G. uralensis seedlings, offering promising strategies for sustainable agriculture and improved crop resilience to climate change.

Biofertilizer and biostimulant potentials of phosphate-solubilizing Bacillus subtilis subsp. subtilis M1 strain and silicon in improving low phosphorus availability tolerance in rosemary.

The present study aimed to evaluate the single and combined effects of Si exogenous treatment and Bacillus subtilis subsp. subtilis M1 strain inoculation on rosemary tolerance to low phosphorus (P) availability. Hence, rosemary plants were fertilized with 250µmol Ca3HPO4 (stressed plants) or 250µmol KH2PO4 (control plants) under Si treatment and B. subtilis M1 strain inoculation. P starvation negatively affected rosemary growth and its P nutrition. However, exogenous Si supply or B. subtilis M1 strain inoculation significantly (P<0.001) alleviated the deficiency-induced effects and significantly improved rhizogenesis, acid phosphatase activity, P uptake, and eventually dry weight of shoot and root. Moreover, Si-treatment and/or B. subtilis M1 strain inoculation significantly (P<0.001) reduced the oxidative damage, in terms of malondialdehyde and hydrogen peroxide accumulation. This was found positively correlated with the higher superoxide dismutase activity, and the elevated non-enzymatic antioxidant molecules accumulation, including total polyphenols in Si-treated and inoculated P-deficient plants. Taken together, Si supplementation and/or B. subtilis M1 strain inoculation could be a good strategy to sustain rosemary plant growth under P starvation conditions.

Mitigating citrus fruit cracking: the efficacy of chelated calcium or silicon foliar fertilizers in 'Okitsu no. 58' citrus fruit.

The 'Okitsu No. 58' citrus variety is highly prone to fruit cracking, which jeopardizes yield and results in economic losses. In this study, we investigated the impacts of spraying 5 distinct concentrations (0.1, 0.2, 0.3, 0.4, and 0.5 g/L) of chelated calcium (Ca) or silicon (Si) fertilizers at the young fruit stage (60-90 days after flowering, DAF) on fruit cracking and quality in the citrus variety 'Okitsu No. 58'. The results showed either Ca or Si fertilizer treatments reduced fruit cracking. We found that all Ca and partial Si treatments (0.4 and 0.5 g/L) significantly promoted the accumulation of Ca content in the peel. Notably, Ca or Si treatments significantly reduced polygalacturonase (PG) activity and inhibited the production of water-soluble pectin (WSP) in the peel. Additionally, Ca or Si treatments elevated the superoxide dismutase (SOD) activity and decreased the malondialdehyde (MDA) content of the peels. Changes in these parameters likely contributed to strengthening the durability of peel cell wall constituents, thus enhancing the fruit's resistance to fruit cracking. Overall, except for the C3 (0.3 g/L of Ca), Ca or Si fertilizers contributed to fruit conventional quality, mainly in terms of higher soluble sugars (SS) and SS/TA (titratable acid). Therefore, our findings will provide a reference for the prevention and control of citrus fruit cracking and the development of new fertilizers.

Harmonizing Growth Symphony: Unraveling the Intricacies of Apricot Seedling Enhancement Through Humic Acid and Silicon Applications

Understanding the physiological responses of apricot (Prunus armenica L.) seedlings to treatments involving Humic Acid (HA), Silicon (Si), and their combination (HA + Si) is crucial for advancing sustainable agricultural practices. Focused on growth parameters, physiological attributes, and leaf mineral concentrations, this study addressed critical knowledge gaps in the influence of these treatments on apricot seedlings. The study highlighted a significant increase in stomatal conductance (SC), with the combined HA + Si treatment displaying the highest SC value at 303.98 mmol.m-2s-1. In contrast, control seedlings of the Alyanak apricot cultivar showed the lowest SC, registering at 122.52 mmol.m-2s-1. Regarding chlorophyll concentrations, the Şekerpare apricot cultivar treated with HA + Si achieved the highest value of 43.74, while in the Alyanak apricot cultivar, the Si treatment alone marked the second highest concentration at 43.02. The combined treatment (HA + Si) also reduced leaf temperatures (32.28 °C), notably in apricot cultivar Hacıhaliloğlu. Visual evaluation analyses underscored significant increases in Leaf Area (LA), Total Leaf Number (TLN), Shoot Length (SL), and other parameters, with the combined HA + Si treatment consistently outperforming individual ones. Mineral analysis revealed elevated Nitrogen (N) and Phosphorus (P) with HA, increased Magnesium (Mg) with Si and HA + Si, and significant effects on Potassium (K) and Calcium (Ca). Principal Component Analysis (PCA) confirmed the positive impacts on overall plant performance, corresponding to a cumulative explanation of 53.82%. This study provided crucial insights for tailoring agricultural practices to optimize apricot seedlings growth, emphasizing the effectiveness of HA and Si treatments, particularly in combination, for enhanced physiological responses.

Effect of silicon spraying on rice photosynthesis and antioxidant defense system on cadmium accumulation

Cadmium (Cd) pollution is a serious threat to food safety and human health. Minimizing Cd uptake and enhancing Cd tolerance in plants are vital to improve crop yield and reduce hazardous effects to humans. In this study, we designed three Cd concentration stress treatments (Cd1: 0.20 mg·kg−1, Cd2: 0.60 mg·kg−1, and Cd3: 1.60 mg·kg−1) and two foliar silicon (Si) treatments (CK: no spraying of any material, and Si: foliar Si spraying) to conduct pot experiments on soil Cd stress. The results showed that spraying Si on the leaves reduced the Cd content in brown rice by 4.79–42.14%. Si application increased net photosynthetic rate (Pn) by 1.77–4.08%, stomatal conductance (Gs) by 5.27–23.43%, transpiration rate (Tr) by 2.99–20.50% and intercellular carbon dioxide (CO2) concentration (Ci) by 6.55–8.84%. Foliar spraying of Si significantly increased the activities of superoxide dismutase (SOD) and peroxidase (POD) in rice leaves by 9.84–14.09% and 4.69–53.09%, respectively, and reduced the content of malondialdehyde (MDA) by 7.83–48.72%. In summary, foliar Si spraying protects the photosynthesis and antioxidant system of rice canopy leaves, and is an effective method to reduce the Cd content in brown rice.

Silicon nonspecifically affects aggressiveness in Fusarium head blight pathogens

Silicon (Si) has been largely regarded to have no selection pressure on plant pathogens because it regulates plant defense system to reduce pathogen infection and development and does not directly affect pathogen itself; however, its effect seems to be specific in some pathogen-host plant interactions. In Fusarium head blight (FHB), associated with devastating agronomic effects on total yield and grain quality, which infects higher Si-absorbers and –accumulators wheat and barley plants; its effect on aggressiveness is unknown. To clarify the nature of reduction of FHB symptoms upon Si treatment at the earliest and latest development stages, we analyzed Si effect on nine aggressiveness components obtained under several experimental conditions. We used 16 fungal isolates of varying aggressiveness and eight bread wheat, durum wheat and barley cultivars with contrast susceptibility to disease. The positive effect of Si on enhancing host resistance against Fusarium infection in the young and adult host parts showed that the nine components evaluated in this study were negatively impacted by Si. Definitely, Si at 1.7 mM reduced equally FHB symptoms from the highest and least pathogenic isolates of the four tested Fusarium species regardless of botanical background for the used plant materials. This indicates for the first time that Si nonspecifically affects aggressiveness in FHB pathogens. Our results reveal that Si could be a valuable tool in integrated pathogen management by suppressing pathogen development on wheat and barley when affected by Fusarium. Most importantly, no hazard exists to emergence of Si-resistant pathogen populations upon Si applications on diverse FHB populations.

Silicon and Potassium-Induced Modulations in Leaf Carbohydrate Metabolism Confer Freezing Tolerance in Satsuma Mandarin

Freezing temperatures are a severe issue in North Florida, primarily due to occasional cold snaps and frost events in winter and early spring that cause damage to citrus groves, resulting in reduced fruit yield. The apoplasm is the primary cell component that interacts with environmental stress and is essential for plant tolerance to freezing temperatures. The present study was conducted to gain insight into how the application of silicon (Si) and potassium (K) are involved in the leaf apoplasm contributes to freezing stress tolerance, and regulates carbohydrate metabolism. We used Satsuma mandarin (Citrus unshiu Marc.), the most successful commercially grown citrus cultivar in North Florida, and treated trees with two concentrations of Si and K (50 and 100 ppm) both individually and combined as foliar spray to determine their effect as they relate to improving cold hardiness. Freezing stress (-6 °C) caused a severe reduction in photosynthesis, and modulations in leaf carbohydrate metabolism resulted in inhibited plant growth. The exogenous application of Si and K both improved the photosynthesis rate, soluble sugars, and activities of enzymes of carbohydrate metabolism such as fructokinase, phosphofructokinase, hexokinase, sucrose and phosphate synthase, and acid and neutral invertase. Applying Si (100 ppm) and combined treatment (Si + K-50) showed the best response by inducing the maximum tolerance to freeze stress. Our data demonstrated the ameliorative effect of Si and K under freezing stress in citrus is associated with modification in carbohydrate metabolism in the leaf apoplasm. This study provides direction for future research to investigate the effect of Si and K on the transcriptome and metabolome in citrus plants and their tissues under freezing stress.Graphical

Optimized silicon fertilization regime weakens cadmium translocation and increases its biotransformation in rice tissues

In acidic paddy fields of South China, rice (Oryza sativa L.) faces the dual challenges of cadmium (Cd) toxicity and silicon (Si) deficiency. Although previous studies have highlighted the functions of Si application timing and strategies in mitigating Cd-stressed rice, the precise mechanisms underlying the health restoration of Cd-toxic rice and the assurance of grain safety remain elusive. This study explored Cd translocation and detoxification in the shoots of rice regulated by various Si fertilization regimes: Si(T) (all Si added before transplanting), Si(J) (all Si added at jointing), and Si(TJ) (half Si added both before transplanting and at jointing). The findings revealed that the regime of Si(TJ) was more beneficial to rice health and grain safety than Si(T) and Si(J). The osmotic regulators such as proline, soluble sugars, and soluble proteins were significantly boosted by Si(TJ) compared to other Si treatments, and which enhanced membrane integrity, balanced intracellular pH, and increased Cd tolerance of rice. Furthermore, Si(TJ) was more effective than Si(T) and Si(J) on the Cd sequestration in the cell wall, Cd bio-passivation, and the down-regulated expression of the Cd transport genes. The concentrations of Cd in the xylem and phloem treated with Si(TJ) were reduced significantly. Additionally, Si(TJ) facilitated much more Cd bound with the outer layer proteins of grains, and promoted Cd chelation and complexation by phytic acid, phenolics, and flavonoids. Overall, Si (TJ) outperformed Si(T) and Si(J) in harmonizing the phycological processes, inhibiting Cd translocation, and enhancing Cd detoxification in rice plant. Thereby the split Si application strategy offers potential for reducing Cd toxicity in rice grain.

The physiological and biochemical role of silicon in enhancing the resistance of maize to root‐lesion nematode

AbstractSilicon (Si) plays an important role in enhancing the tolerance of plants to biotic and abiotic stress in soil ecosystems. Root‐lesion nematodes (Pratylenchus scribneri; RLNs) cause root damage and diseases that result in quality deterioration and economic loss. This study investigated the effects of Si application on maize plants and its interaction with RLN infection. We set up different treatments to evaluate the role of silicon application in maize root growth and RLN resistance. This study conducted analysis by combining measurements of the metabolism and root activity of maize under different conditions. The results suggested that Si application (0.5 g/kg) significantly promoted fresh shoot weight, plant height, SPAD value (chlorophyll content), and root activity of maize, regardless of RLN inoculation. The highest SPAD value was observed in the Si treatment, which was significantly higher than in the control (CK) and RLN (N) treatments. Analysis of enzyme activity revealed that nematode inoculation reduced catalase (CAT) activity and increased malondialdehyde (MDA) concentration, while Si application increased CAT activity and decreased MDA concentration. In the SiN treatment, there was increased CAT activity at 0, 12, 48, 72 and 96 h compared with the N treatment. In parallel, nematode inoculation increased phenylalanine ammonia‐lyase (PAL), and polyphenol oxidase (PPO) activities, while SiN treatment further enhanced their activities. These findings indicate that Si application enhances maize resistance to nematode infection and improves plant growth and antioxidant defence mechanisms.

Effect of exogenous silicon treatments on cell wall metabolism and textural properties of tomato fruits

This study investigated the effects of exogenous silicon (Si) treatment on cell wall metabolism in tomato fruits. The experiment was conducted with ‘Jinfan502’ tomato (Solanum lycopersicum L.) as the test material, which was cultivated in substrates with foliar sprays of the following different concentrations of Si treatments: 0 mmol·L−1 (CK), 0.6 mmol·L−1 (T1), 1.2 mmol·L−1 (T2), and 1.8 mmol·L−1 (T3). To study the effects of the treatment on the mature green, breaker, and red ripening stages of tomato fruit cell wall components, cell wall metabolism-related enzyme activities, textural properties, and the impact of ethylene production during the red ripening stage were assessed. The results showed that the cell wall components and textural properties of the T2 treatment were significantly higher than those of the CK treatment in the green mature, breaker, and red ripening stages. Among them, at the red ripening stage of fruiting, the content of cell wall components in the T2 treatment was significantly improved, and the contents of protopectin, cellulose, hemicellulose, and expansin were increased by 6.29 %, 10.04 %, 2.52 %, and 3.95 %, respectively, relative to the CK treatment; the firmness of the fruit was also significantly increased, by 13.23 %, compared with the CK treatment. Cell-wall-metabolism-related enzyme activity was significantly lower in the T2 treatment than in the CK treatment at the green mature, breaker, and red ripening stages. When Si (T2) was applied during the red ripening stage, the activities of cell wall metabolism-related enzymes were significantly inhibited; compared to the CK treatment, the activities of pectinase (PE), polygalacturonase (PG), pectin methylesterase (PME), β-galactosidase (β-Gal), lipoxygenase (LOX), pectin lyase (PL), and cellulase (CL) were reduced by 16.34 %, 19.37 %, 28.07 %, 10.73 %, 19.86 %, 8.47 %, and 6.53 %, respectively. Furthermore, the ethylene content of the red ripened fruits under the T2 treatment was significantly reduced by 21.59 % compared to the CK treatment. In addition, multiple sets of significant or extremely significant negative correlations existed among ethylene, cell wall components, and textural properties at red ripening stage. Finally, principal component analysis and hierarchical cluster analysis of cell-wall metabolism-related enzyme activities in the three stages of treatment with different Si concentrations showed that the models significantly separated the T2 treatment from the CK, T1, and T3 treatments. In conclusion, exogenous Si T2 treatment (1.2 mmol·L−1) had the greatest effect on delaying cell wall metabolism, which provides the theoretical and technical basis for the enhancement of storage and transport resistance in tomatoes.

Enhanced arsenic stress tolerance in landrace and improved rice cultivars through modulation of gibberellic acid (GA3) synthesis and antioxidant metabolism via phosphorus and silicon supplementation

Arsenic (As), an environmental pollutant, imposes toxic impacts on plant health. In recent years, researchers have focused on comprehending the As-induced intrusion in growth and metabolic components. However, the interactions between phosphorus (P) and silicon (Si) remain elusive, specifically in rice (Oryza sativa) cultivars. Therefore, the present study investigated the effects of P and Si on the defense mechanisms, nutrients accumulation, carbohydrate metabolism, gibberellic acid (GA3) synthesis, and growth responses in Indica rice cultivars (landrace and improved) under As stress. With this focus, our study potentially indicated that As stress (150 µM) negatively impacted the underlying physiological and growth traits, with more pronounced effects on the improved cultivar compared to the landrace. However, P (30 mg kg−1 soil) and/ or Si (1 mM) treatments have prominently reduced oxidative stress with improved defense mechanisms and GA synthesis. Modulation of enzymatic defense system increased in both cultivars but more pronounced in landrace, including superoxide dismutase (+36.47%, +24.43%), ascorbate peroxidase (+95.11%, +78.26%), along with non-enzymatic antioxidants such as ascorbate (+29.43%, +21.48%), and reduced glutathione (+75.45%, +62.34%) concentrations, respectively. Notably, GA concentration (+23.78%, +16.48%) was substantially increased by the cumulative application of P and Si under As stress in both cultivars but more conspicuous in the landrace, respectively. Further, employing GA biosynthesis inhibitor, paclobutrazol (PBZ; 10 µM), substantiated the input of GA-mediated As tolerance, wherein, PBZ reversed the impacts of P and Si on the endogenous GA concentration and defense metabolism. In summation, landrace outperformed improved cultivar leading to As tolerance. This implies that the landrace could be used for future breeding programs permitting in-depth considerations of P and Si-mediated GA3 synthesis under As stress conditions.

Nitrogen and Silicon Contribute to Wheat Defense's to Pyrenophora tritici-repentis, but in an Independent Manner.

Nitrogen (N) and silicon (Si) are mineral elements that have shown a reduction in the damage caused by tan spot (Pyrenophora tritici-repentis (Ptr)) in wheat. However, the effects of these elements were studied separately, and the N and Si interaction effect on wheat resistance to tan spot remains elusive. Histocytological and biochemical defense responses against Ptr in wheat leaves treated with Si (+Si) at low (LN) and high N (HN) inputs were investigated. Soil amendment with Si reduced the tan spot severity in 18% due to the increase in the leaf Si concentration (around 30%), but it was affected by the N level used. The superoxide dismutase (SOD) activity was higher in +Si plants and inoculated with Ptr, leading to early and higher H2O2 and callose accumulation in wheat leaf. Interestedly, phenylalanine ammonia-lyase (PAL) activity was induced by the Si supplying, being negatively affected by the HN rate. Meanwhile, catalase (CAT), and peroxidase (POX) activities showed differential response patterns according to the Si and N rates used. Tan spot severity was reduced by both elements, but their interaction does not evidence synergic effects in this disease's control. Wheat plants from -Si and HN and +Si and LN treatments recorded lower tan spot severity.

RELATIONS BETWEEN THE MASS OF THE FRUITS, THE NUMBER OF FRUITS PER PLANT AND THE AGRICULTURAL YIELD IN PEPPER, WITH INCREASING SILICON DOSES

&lt;p&gt;&lt;strong&gt;Background: &lt;/strong&gt;Statistical relations between the components of agricultural yield and the yield itself after Si treatment as possible non-destructive methods are important for predicting and monitoring the harvest. &lt;strong&gt;Objective:&lt;/strong&gt; To measure the relationships between the mass of the fruit, the number of fruits per plant and the agricultural yield in pepper, with increasing silicon doses. &lt;strong&gt;Methodology:&lt;/strong&gt; The research was carried out at Quevedo State Technical University, Ecuador in a completely randomized design and three repetitions per treatment. The treatments used were 0, 20, 25 and 30 g potassium silicate plant&lt;sup&gt;-1&lt;/sup&gt;. The variables evaluated were fruit weight, number of fruits per plant and agricultural yield at the time of harvest. Path analysis, multiple and single linear regressions, and nonlinear regressions were performed. &lt;strong&gt;Results:&lt;/strong&gt; The path analysis showed a greater direct effect of the number of fruits per plant with and without the presence of silicon. Fruit weight, number of fruits per plant, and agricultural yield increased linearly with increasing silicon dose. &lt;strong&gt;Implications:&lt;/strong&gt; The best adjustment of fruit weight both in the presence and absence of silicon when it is related to the yield corresponded to a non-linear model, specifically to a Hill sigmoidal function. &lt;strong&gt;Conclusion: &lt;/strong&gt;Through multiple linear regression, it was shown that both yield component variables, i.e. fruit weight and number of fruits per plant, have a greater influence on agricultural yield when fertilized with silicon. &lt;/p&gt;

Chitosan-GSNO Nanoparticles and Silicon Priming Enhance the Germination and Seedling Growth of Soybean (Glycine max L.).

Soybean, a major legume crop, has seen a decline in its production owing to challenges in seed germination and the development of seedlings. Thus, in this study, we systematically investigated the influence of various chitosan-S-nitrosoglutathione (chitosan-GSNO) nanoparticle (0, 25, 50, and 100 µM) and Si (0, 0.5, and 1 mM) priming concentrations on soybean seed germination and seedling growth over five different priming durations (range: 1-5 h at each concentration). Significant differences were observed in all parameters, except seedling diameter, with both treatments. Seed germination was significantly enhanced after 3 h of priming in both treatments. The final germination percentage (FGP), peak germination percentage (PGP), vigor index (VI), seedling biomass (SB), hypocotyl length (HL), and radical length (RL) of 100 μM chitosan-GSNO-nanoparticle-primed seeds increased by 20.3%, 41.3%, 78.9%, 25.2%, 15.7%, and 65.9%, respectively, compared with those of the control; however, the mean germination time (MGT) decreased by 18.43%. Si priming at 0.5 mM increased the FGP, PGP, VI, SB, HL, and RL by 13.9%, 55.17%, 39.2%, 6.5%, 22.5%, and 25.1%, respectively, but reduced the MGT by 12.29% compared with the control treatment. Chitosan-GSNO and Si treatment up-regulated the relative expression of gibberellic acid (GA)-related genes (GmGA3ox3 and GmGA2ox1) and down-regulated that of abscisic acid (ABA)-related genes (GmABA2, GmAAO3, and GmNCED5). Chitosan-GSNO and Si application increased bioactive GA4 levels and simultaneously reduced ABA content. Hence, the use of exogenous chitosan-GSNO nanoparticles and Si as priming agents had a beneficial effect on seed germination and seedling growth because of the up-regulation in the expression of GA and down-regulation in the expression of ABA. Additional research is needed to understand the combined impact of Si and chitosan-GSNO nanoparticles, including their effects on the expression levels of other hormones and genes even in the later growth stage of the crop.

Enhancing growth and Cadmium remediation in red alga, Gracilaria edulis through silicate intervention

This study investigates the potential of silicate to alleviate cadmium (Cd) toxicity in Gracilaria edulis, an agarophyte. Under various culture conditions spanning 21 days, alga was grown in control, Silicate (Si) medium, and different Cd concentrations (100, 200, and 300 µM) with or without Si100 µM and the effect was measured by photosynthesis O2 evolution, relative growth rate (RGR), biomass, biochemical compositions such as chlorophyll a, phycobilipigments (phycocyanin, allophycocyanin, and phycoerythrin), carbohydrate, protein, lipid peroxidation and Cd accumulation. Cd, a toxic heavy metal, negatively impacts plant and algal growth and metabolism. In contrast, traditionally considered non-essential, Si has growth-promoting properties under various stress conditions. The present study reveals that Si significantly enhances photosynthesis except for Cd300. In Cd100, the photosynthetic O2 evolution was 0.08 nM s−1, whereas in Cd100 + Si, it increased to 0.09 nM s−1. The Cd300 + Si treatment exhibited a rate of 0.07 nM s−1, but in Cd300, it was 0.05 nM s-1 on the 9th day of culture, and the rate was proportionately high on the 18th day of culture. The RGR and biomass significantly improved, particularly when Cd100 was combined with Si. Alga shows a decrease in the chlorophyll a, phycobilin pigments, carbohydrate, and protein content when grown at Cd300 concentration but significantly increased when combined with Si treatment. Alga showed less carbohydrate content (0.30 ± 0.02) at Cd300 µM exposure, of which was increased by adding Si (Cd300 + Si) to 0.34 ± 0.02 mg g−1 alga fresh wt. Cd uptake by the alga is high at Cd300 but considerably low at Cd100 + Si and Cd200 + Si concentrations. Malondialdehyde (MDA) level indicating lipid peroxidation-induced oxidative damage was significantly reduced in Si-treated Cd concentrations compared to heavy metal treatment alone. This study demonstrates that silicate can potentially mitigate the adverse effects of Cd on G. edulis by creating a favorable environment for its growth. Thus, it exhibits promise in alleviating Cd toxicity in G. edulis.

Improving the Yield and Quality of Tomato by Using Organic Fertilizer and Silicon Compared to Reducing Chemical Nitrogen Fertilization

Essential macronutrient nitrogen (N) is crucial for plant growth and yield, but excessive chemical N fertilizer not only increases unnecessary production costs but also causes environmental pollution. Therefore, reducing N fertilizer use by increasing organic fertilizer use is crucial for sustainable agriculture. In this study, we investigated the effects of three nitrogen levels—the recommended rate (N), a 20.0% reduced rate (0.8N), and a 40.0% reduced rate (0.6N)—and two levels of organic fertilizer—a normal dose (M) and a four-times the normal dose (4M)—combined with root application of the beneficial element silicon (Si) on the photosynthetic characteristics, yield, and fruit quality of the tomato cultivar ‘Tianxi No. 5’. Compared with M + N treatment, the longitudinal diameter, transverse diameter, fruit weight, and fruit yield of tomato fruit in 4M + 0.6N treatment significantly increased by 12.4%, 14.6%, 14.5%, and 12.8%, respectively, while the yield was further improved with Si application. In addition, a reduction in N fertilizer and an increase in organic fertilizer, combined with Si application, improved fruit quality parameters such as concentrations of vitamin C, lycopene, phenols, flavonoids, sucrose, fructose, etc., and promoted sugar metabolism-related enzyme activity (sucrose synthase, invertase, and sucrose phosphate synthase) and the accumulation of N in the fruit. The principal component analysis and three-factor analysis of variance (ANOVA) of the fruit quality and yield indices showed that nitrogen fertilizer, organic fertilizer, silicon fertilizer, and the interaction of the three had significant effects on the quality and yield of tomato fruits, and that the 4M + 0.6N + Si treatment had the best combined effect on the yield and quality of the tomatoes. Thus, a moderate reduction in chemical N fertilizer, combined with increased organic fertilizer and Si, could be an effective agronomic practice for improving the yield and quality of tomatoes.