Silicon Amendment Research Articles

Effects of active silicon amendment on Pb(II)/Cd(II) adsorption: Performance evaluation and mechanism

In this study, a high-Si (Si) adsorbent (APR@Sam) was prepared by acid leaching slag (APR) from lead-zinc (Pb-Zn) tailings based on high-temperature alkali melting technology. The synthesized Si-based materials were applied to aqueous solutions contaminated with Pb and cadmium (Cd) to investigate the crucial role of active Si in sequestering heavy metals. The adsorption capacities of APR@Sam and the Si-depleted material (APR@Sam-NSi) were studied under different pH and temperature conditions. The results showed that as the pH increased from 3 to 7, the adsorption capacity increased, the active Si content in the solution increased by 63 %, and the maximum pH of the solution after adsorption was 7.12. After the removal of active Si, the Pb (II) and Cd (II) adsorption capacities of APR@Sam decreased by 45 % and 11.96 %, respectively. OH- promoted the release of Si into the solution, enhancing the material's adsorption efficiency. The reaction mechanism is mainly attributed to surface complexation guided by Si-O and Si-O-Si bonds, metal cation exchange, and bidentate coordination. The results indicated that the Si component is critical for the removal of Pb (II) and Cd (II) by APR@Sam and provide valuable insights into resource recovery strategies from leaching residues.

Impact of Nitrogen and Silicon Amendments on Hopper Population in Rice

Present study showed that total dry weight values of rice plants were significantly higher in the plant with high nitrogen (N) application (100kg/ ha) as compared to low nitrogen (30 kg/ ha) treatment whereas the silicon (Si) amendment had very little effect on biomass accumulation but both the elements are associated with hopper pest population densities in rice. Here the correlation coefficient values were high- r= 0.759 to 0.999 and r= 0.726 to 0.996 for brown planthopper Nilaparvata lugens (Stål) and green leafhopper Nephotettix virescens (Dist.) respectively when the calculation was made between insect population and plant biomass after application of nitrogen 0 to 100 kg/ ha. However, when calcium silicate was added 140 kg/ ha or above with high doses of nitrogen the N. lugens and N. virescens incidence reduced in comparison to others. Consequently, the interaction between nitrogen and silicon play a significant role in resistance to these hopper pests.

Silicon Amendment Escalates Cellular Si Deposition and Antioxidant Enzyme Defense against Scirpophaga incertulas (Walker) Attack in Rice

Silicon Amendment Escalates Cellular Si Deposition and Antioxidant Enzyme Defense against Scirpophaga incertulas (Walker) Attack in Rice

Effect of Silicon Amendment on Growth and Nitrogen Status of Common Landscaping Plants

Effect of Silicon Amendment on Growth and Nitrogen Status of Common Landscaping Plants

Root Silicon Amendment Enhances Barley’s Resistance to Fusarium Head Blight in the Field

Background: Silicon (Si) amendment plays an important role in enhancing the resistance of several plant species to diverse pathogens. To date, a few studies have focused on how Si application helps barley, a higher Si absorber and accumulator monocot, to resist fungal diseases, including Fusarium head blight (FHB), which reduces the quality and safety of harvested products worldwide. However, no study has ever been conducted to demonstrate Si's ability to suppress FHB development in barley heads under uncontrolled climatic conditions. Materials and Methods: This 2-year field study elucidated the effect of multiple Si applications at 1.7 mM via roots in two barley cultivars, Arabi Aswad (AS moderately resistant) and Arabi Abiad (AB moderately susceptible), to control four Fusarium species with diverse pathogenicity. The incidence of FHB (DI type I resistance), severity of FHB (DS type II), and Fusarium-damaged kernels (FDK type III) were also tested to describe the nature of the Si-enhanced barley resistance. Results: Si treatment at 1.7 mM under soil culture decreased FHB development by enhancing all resistance types measured in the present research. DI, DS, and FDK were reduced by 18.7%, 20.3%, and 20.2%, respectively, in Si-Fusarium-inoculated treatments relative to fungal-inoculated controls. Si absorption in barley strengthened the defense system measured by type I and type II on AB to a level comparable to AS not amended with Si. Irrespective of the barley cultivar, however, Si resulted in a quasi-similar reduction of FDK. Importantly, Si treatment at 1.7 mM decreased the damage of FHB in previous analyses conducted on AS and AB under in vitro and growth chamber environments, showing that Si enhanced the expression of resistance to FHB infection in seedlings and adult barley plants. Conclusion: All of these results are promising outcomes for the application of Si as a safe and effective method against Fusarium species. This study provides new insights into the potential of multiple Si applications at 1.7 mM via roots for boosting barley’s resistance to FHB with a bright prospect for Si use in barley cultivation under field conditions.

Probing the effects of silicon amendment on combined stressors on rice: Lead pollution and blast fungus (Magnaporthe oryzae) infection

As agroecology deteriorates, agricultural production is threatened by the combined stressors of exposure to environmental pollutants and pathogenic microbes. Proper agronomic practices for crop growth management and fertilization require understanding plant tolerance strategies. Both rice blast and heavy metals substantially impair rice crops, while silicon (Si) is an effective amendment to alleviate the combined stressors. Herein, this study was conducted to investigate the rice physiology and pathology perspective on the mechanism of Si alleviation against both lead (Pb) toxicity and Magnaporthe oryzae infection, utilizing pot experiments with inoculation of the virulent Magnaporthe oryzae strain. Exogenous Si reduced the phyto-availability and plant absorption of Pb, resulting in a 73.5% reduction in exchangeable Pb concentration in soil and a 40.23% reduction in rice plants. Furthermore, Si addition boosted the plant antioxidant system by increasing the activities of related enzymes, as the activities of catalase, superoxide dismutase, and polyphenol oxidase were significantly improved while the activity of peroxidase in rice panicles decreased. As a result, an improvement in dry matter quantity by 19.19% was observed compared to treatments without Si application, and the panicle blast severity (PBS) was reduced by 0.4–37.52%. Notwithstanding the interaction between the combined stressors, this study revealed that the speciation of Pb formation in the rhizosphere was the primary contributor to the alleviation of abiotic stresses, whereas the regulation of oxidative stress by enzymatic antioxidants played a dominant role in alleviating Magnaporthe oryzae colonization and impairments. The regulation process may reveal the mechanism of siliceous fertilizer functioning in the paddy system. Thereby the role of exogenous Si in anti-fungal, heavy metal toxicology, and plant physiology needs further study to fully elucidate the role of Si amendment, which is proposed to be considered from the perspective of soil chemistry and plant physiology.

Silicon amendment – influence on sorghum growth, yield, and nutrient uptake under water stress

Silicon enhances plant growth and development, alleviating the effects of biotic and abiotic stresses. Drought severe abiotic stress that hampers plant growth and production globally, posing threat to food security. Mass production of sorghum is crucial to eradicating the present increasing food insecurity in water-stressed regions. The study evaluated the effects of silicon on nutrients uptake, growth and yield of sorghum under different water regimes. A two-season field trial was carried out to evaluate two sorghum varieties (seredo and Machakos local red), silicon (with silicon and without silicon) under three irrigation regimes (20%, 40% and 60%) laid out in Randomized Completely Block Design in a factorial arrangement replicated thrice. Data was collected on growth, yield and nutrients uptake, which was subjected to analysis of variance using R software. Results showed that Seredo variety had the highest root dry weight (123.5 g) and longest roots (51.4 cm). At 60% water regime and silicon amendment enhanced sorghum growth better than other treatments. Seredo variety recorded the highest grain yield (4.82tha−1), phosphorus (95.53 kg ha−1), nitrogen (32.16 kg ha−1), K (76.06 kg ha−1), calcium (3919.00 kg ha−1) and magnesium (165.02 kg ha−1). Seredo had the maximum harvest index of 0.41. At 40% water regime, Seredo variety amendment with Si produced the highest grain yields and nutrients uptake. Si amendment can improve sorghum growth and yield under water stress conditions, as indicated by high grain yield and nutrients uptake achieved at 40% water regime. The use of Silicon is recommended for improving sorghum productivity in regions experiencing low rainfall.

Varietal Resistance and Chemical Ecology of the Rice Stink Bug, Oebalus pugnax, on Rice, Oryza sativa.

The rice stink bug, Oebalus pugnax F. (Hemiptera: Pentatomidae), is a key pest of heading rice in the southern United States. Chemical insecticide application is currently the primary method of control of O. pugnax, warranting an improved management program for this species. The potential other management tactics for O. pugnax include eco-friendly measures such as host-plant resistance, silicon application, and the use of semiochemicals. In this study, the feeding preference and performance of O. puganx on cultivated and non-cultivated rice varieties were examined. Choice tests showed that the rice varieties Cheniere and Kaybonnet were most and least preferred by O. pugnax for feeding, respectively. The results of a no-choice experiment showed that the number of nymphs surviving to the adult stage did not differ among rice varieties, although the percent survival was low on the varieties Kaybonnet and Jazzman. Here, we also showed for the first time that silicon application had a significant negative impact on O. pugnax performance, increasing the nymph development time and reducing survival by almost 40% relative to the control. Based on these results, it could be suggested that silicon amendment is a promising management strategy for this pest. Further research is needed to examine whether silicon application also reduces the feeding damage caused by O. puganx. In addition, the chemical compositions of the metathoracic gland and dorsal abdominal gland extracts were also characterized for the first time in this study, and their biological roles and potential use in pest management are discussed.

Silicon amendment improves wheat defence against Fusarium graminearum and complements the control by fungicide of Fusarium head blight

AbstractA three‐year field experiment with two wheat cultivars evaluated the effect of soil‐applied silicon (Si), with and without fungicide spraying, on Fusarium head blight (FHB) control. Silicon treatment alone reduced FHB severity and the percentage of damaged wheat kernels, regardless of the cultivar. The best disease control was obtained for the cultivar with moderate disease resistance (MR), supplied with silicon and treated with fungicide during flowering. Silicon treatment alone promoted an increase in deoxynivalenol (DON) concentration in the disease‐susceptible cultivar; however, in the MR cultivar, silicon amendment associated with fungicide treatment led to a reduction in DON concentration. Greenhouse experiments evaluated the effect of silicon combined with different timings of fungicide application on wheat defences against Fusarium graminearum. Plants supplied with silicon had a longer pathogen incubation period, lower FHB severity and lower DON concentration when compared to plants without silicon. In addition, silicon‐supplied plants had higher soluble phenolic content and altered antioxidant enzyme activities (SOD, CAT, POX and PPO) that favoured early accumulation of hydrogen peroxide when compared to plants without silicon. Greater control of FHB and lower DON concentration in plants treated with silicon and fungicide before inoculation and up to 1 day after inoculation was associated with increased levels of defence‐associated metabolites. Silicon contributed to the reduction of FHB and DON concentration in wheat, especially for the MR cultivar and, when combined with fungicide spraying, both MR and disease‐susceptible cultivars had enhanced performances upon silicon amendment.

Defense response induced by silicon amendment against Scirpophaga incertulas (Walker) and Cnaphalocrocis medinalis (Guenee) infestation in rice

Considering silicon (Si) amendment as an eco-holistic approach in insect pest management, an attempt was made to optimize the dose of diatomaceous earth (DAE), an organic silicate fertilizer and study the mechanism of resistance against stem borer and leaf folder infesting rice. Basal application of this product at 50-500 kg ha-1 effectively restricted damage by both the insects in rice cv.TN1 and increased the crop yield by 22-80% over control as against 74% increase in standard check, calcium silicate applied at 2000 kg ha-1. An enhancement of plant resistance to these pests was conspicuously observed at different doses of DAE. The best performance was exhibited at 300 kg ha-1 with a record average of 9.46% dead heart and 3.26% white ears due to stem borer and 1.84% leaf damage by leaf folder compared to corresponding damage of 22.34, 19.40 and 3.33%, respectively in untreated control. This induction of plant resistance was attributed to higher silicon deposit supported by marked impact of feeding stimuli from stem borer in altering the chlorophyll, phenol and protein contents of the rice plant.

Silicon fertilizer mediated structural variation and niche differentiation in the rhizosphere and endosphere bacterial microbiome and metabolites of sugarcane.

The microbiomes of plant are potential determinants of plant growth, productivity, and health. They provide plants with a plethora of functional capacities, namely, phytopathogens suppression, access to low-abundance nutrients, and resistance to environmental stressors. However, a comprehensive insight into the structural compositions of the bacterial abundance, diversity, richness, and function colonizing various microenvironments of plants, and specifically their association with bioactive compounds and soil edaphic factors under silicon (Si) amendment remains largely inconclusive. Here, high-throughput sequencing technology and nontargeted metabolite profiling method were adopted to test the hypotheses regarding microbiome niche abundance, diversity, richness, function, and their association with bioactive compounds and soil edaphic factors within different ecological niches (leaf, stem, root, rhizosphere, and bulk soils) under Si amendment during cane growth were we addressed. Our results demonstrated that Si correspondingly increased sugarcane theoretical production and yield, and remarkably enhanced soil nutrient status, especially Si, AP, and AK. It was also observed that bacterial diversity demonstrated tissue-dependent distribution patterns, with the bulk soil, rhizosphere soil, and root endosphere revealing the highest amount of bacterial diversity compared with the stem and leaf tissues. Moreover, Si exhibited the advantage of considerably promoting bacterial abundance in the various plant compartments. Co-occurrence interactions demonstrated that Si application has the potential to increase bacterial diversity maintenance, coexistence, and plant–soil systems bacteria connections, thereby increasing the functional diversity in the various plant tissues, which, in turn, could trigger positive growth effects in plants. Network analysis further revealed that metabolite profiles exhibited a strong association with bacterial community structures. It was also revealed that Si content had a considerable positive association with bacterial structures. Our findings suggest that the dynamic changes in microbe’s community composition in different plant and soil compartments were compartment-specific. Our study provides comprehensive empirical evidence of the significance of Si in agriculture and illuminated on differential metabolite profiles and soil microbe’s relationship.

Silicon amendment induces resistance in rice to Diatraea saccharalis (Lepidoptera: Crambidae)

Silicon amendment induces resistance in rice to Diatraea saccharalis (Lepidoptera: Crambidae)

Effect of Silicon Amendment on Herbivore Induced Plant Volatiles of Rice Plant Infested by Brown Planthopper Nilaparvata Lugens (Stål)

Silicon (Si) is known to play a very important role in a plant’s direct and indirect defense. In rice plants, its impact on induced volatiles released upon Brown planthopper (BPH), Nilaparvata lugens feeding is less understood. The BPH-induced volatile compounds from Si amended rice plants were analyzed using Gas Chromatography-Mass Spectrometry (GC-MS). The alteration in Herbivore Induced Plant Volatiles (HIPV’s) blend was observed, wherein, total 38 HIPVs were found to be differentially released. The HIPV mainly belongs to alkane, alkene, alcohol and terpene groups. Overall, Si amendment caused a significant effect on the composition of HIPVs in rice, some of which are involved in tri-trophic interaction.

Effect of silicon and fungicide on photosynthetic responses in barley leaves challenged by Bipolaris sorokiniana

The effect of silicon (Si) amendment in the soil, combined with fungicide application 7 or 15 days before plant inoculation, was evaluated on barley plants challenged by Bipolaris sorokiniana. For this, the disease control, the gas exchange parameters, and the concentration of photosynthetic pigments were evaluated on two barley cultivars (AnaG01 and BRS Cauê). The higher spot blotch severity occurred on plants not supplied with Si and without fungicide application. The disease reduced the net assimilation of CO2 (A), the stomatal conductance (gs), internal CO2 concentration (Ci) and transpiration rate (E). The concentration of photosynthetic pigments was significantly altered in inoculated leaves. The plants supplied with Si showed an increase in leaf Si concentration, which was associated with a reduction of up to 15% in spot blotch, and increase in A, gs, Ci, and E, and concentration of pigments (Chlorophylls a and b, and carotenes). The fungicide reduced disease intensity and increased A and gs, and the concentration of pigments. Higher control of the disease by fungicide occurred on plants supplied with Si, especially when application occurred at 15 day before inoculation. In conclusion, the association of Si and fungicide provided a greater reduction in spot blotch and maintained a better physiological state of the plant when affected by B. sorokiniana.

Bioorganic and silicon amendments alleviate early defoliation of pear trees by improving the soil nutrient bioavailability, microbial activity, and reshaping the soil microbiome network

Pear trees with severe early defoliation usually suffer from weakened aboveground growth and a serious decrease of fruit quality and yield. Soil fertility and its microbial community and functional activity are significant factors impacting plant growth and yield, which also might be the very factors that influence the early defoliation of pear trees. To address the problems caused by chemical fertilizers, bioorganic fertilizer (BIO) and silicon amendment (SOA) are increasingly used as amendments to improve soil microbial activity and increase soil nutrient availability. However, how effective BIO and SOA are at improving the health of soils and reducing early defoliation remains unclear. Here, we conducted a 4-year field experiment (2016–2019) in a 25-year-old ‘Cuiguan’ pear orchard in Jianning county, Fujian province, comparing local custom fertilization (CK), local custom fertilization supplemented with SOA (CK-SOA), BIO, and BIO supplemented with SOA (BIO-SOA). At the end of the 4-year study we found that BIO and BIO-SOA treatments resulted in reduced leaf nitrogen content and increased leaf potassium (K), calcium (Ca), silicon (Si), and manganese (Mn) content. BIO and BIO-SOA treatments also resulted in a 50% reduction of the early deciduous rate and a 47% increase in pear yield. Compared with CK treated soil, BIO and BIO-SOA treated soils had higher nitrate nitrogen content (NO3−-N), available Si, Fe, Mn, and Zn content, and significantly improved microbial biomass nitrogen content (MBN), geometric mean enzyme activity (GMEA) and ecosystem multifunctionality (EMF). Network analysis revealed that BIO and BIO-SOA treatments had significantly altered the bacterial and fungal community composition in the orchard soil. Redundancy analysis (RDA) and the Mantel test indicated that soil available K, exchangeable Ca and Mg, and available Si, Fe, Mn and Zn content were the main factors influencing bacterial and fungal communities. The increased nutrient availability (e.g., NO3−-N and microelement contents), MBN, GMEA and EMF had negative effects on the early defoliation rate. Random Forest model identified soil available Si content, microbial biomass nitrogen content, EMF, and GMEA as the main predictors of early defoliation rate. Overall, this study demonstrates that application of BIO or BIO mixed with SOA can alleviate the early defoliation rate of pear trees by increasing the availability of microelements, microbial functional activity, and changing the soil microbial community composition.

Silicon alleviates antimony phytotoxicity in giant reed (Arundo donax L.).

Silicon enhances photosynthetic efficiency, biomass, and lignification of root structures possibly limiting antimony translocation and mitigating phytotoxicity in giant reed plants. Antimony (Sb) is a non-essential metalloid causing toxic effects in plants. Silicon has been reported to impart tolerance against biotic and abiotic stress in plants. Fast-growing plant, giant reed (Arundo donax L.) is a promising energy crop, can be a suitable plant for phytoremediation. However, information regarding the tolerance capacity with respect to Sb toxicity and potential of Si to mitigate the Sb phytotoxicity in giant reed are very scarce. Rhizomes of giant reed were grown for ten weeks in hydroponics exposed to Sb, Si, and their combination wherein treatment without Sb/Si served as control. Effect of these treatments on rate of net photosynthesis and photosynthetic pigments, phytoextraction ability of Sb, Si and Sb uptake, plant biomass, and lignification and suberization of roots along with localization of Sb and Si were analysed. We found that Si considerably improved the growth and biomass of giant reed under Sb toxicity. Antimony reduced the photosynthesis and decreased the content of photosynthetic pigments, which was completely alleviated by Si. Silicon amendment to Sb treated plants enhanced root lignification. Silicon enhanced lignification of root structures probably restricted the Sb translocation. However, co-localization of Sb with Si has not been observed neither at the shoot nor at the root levels. Similarly, Sb was also not detected in leaf phytoliths. These findings suggest that Si treatment promotes overall plant growth by improving photosynthetic parameters and decreasing Sb translocation from root to shoot in giant reed by improving root lignification.

Silicon Amendment Enhances Agronomic Efficiency of Nitrogen Fertilization in Maize and Wheat Crops under Tropical Conditions

Sustainable management strategies are needed to improve agronomic efficiency and cereal yield production under harsh abiotic climatic conditions such as in tropical Savannah. Under these environments, field-grown crops are usually exposed to drought and high temperature conditions. Silicon (Si) application could be a useful and sustainable strategy to enhance agronomic N use efficiency, leading to better cereal development. This study was developed to explore the effect of Si application as a soil amendment source (Ca and Mg silicate) associated with N levels applied in a side-dressing (control, low, medium and high N levels) on maize and wheat development, N uptake, agronomic efficiency and grain yield. The field experiments were carried out during four cropping seasons, using two soil amendment sources (Ca and Mg silicate and dolomitic limestone) and four N levels (0, 50, 100 and 200 kg N ha−1). The following evaluations were performed in maize and wheat crops: the shoots and roots biomass, total N, N-NO3−, N-NH4+ and Si accumulation in the shoots, roots and grain tissue, leaf chlorophyll index, grain yield and agronomic efficiency. The silicon amendment application enhanced leaf chlorophyll index, agronomic efficiency and N-uptake in maize and wheat plants, benefiting shoots and roots development and leading to a higher grain yield (an increase of 5.2 and 7.6%, respectively). It would be possible to reduce N fertilization in maize from 185–180 to 100 kg N ha−1 while maintaining similar grain yield with Si application. Additionally, Si application would reduce N fertilization in wheat from 195–200 to 100 kg N ha−1. Silicon application could be a key technology for improving plant-soil N-management, especially in Si accumulator crops, leading to a more sustainable cereal production under tropical conditions.

Silicon amendment to rice plants reduces the transmission of southern rice black-streaked dwarf virus by Sogatella furcifera.

Plant viruses are transmitted mainly by piercing-sucking herbivores, and viral disease management relies on chemical control of vectors. Southern rice black-streaked dwarf virus (SRBSDV) is transmitted by the white-backed planthopper (WBPH), Sogatella furcifera. This study aimed to evaluate the potential of silicon (Si) amendment for reducing SRBSDV transmission. The settling and ovipositional preferences of WBPH females decreased significantly by 14.6-43.7% for plants treated with either 0.16 g or 0.32 g SiO2 kg-1 soil during SRBSDV acquisition and by 26.2-28.3% for plants treated with 0.32 g SiO2 kg-1 soil during SRBSDV inoculation, compared with controls. Adding either 0.16 or 0.32 g SiO2 kg-1 soil significantly reduced SRBSDV inoculation rate by 31.3% and 45.3%, respectively, and acquisition rate by 25.5% and 66.0%, respectively. Silicification was intensified more in plants treated with 0.32 g SiO2 kg-1 soil than in controls. The nonprobing (np) duration increased, and the phloem sap ingestion (N4-b) duration decreased significantly in the WBPHs feeding on high-rate-Si-supplemented plants compared with control plants during both inoculation and acquisition access. This study showed that Si amendment to rice plants decreased the WBPH settling and ovipositional preference and the SRBSDV acquisition and inoculation rates, thereby reducing SRBSDV transmission. The intensified plant silicification and the altered WBPH feeding behaviors (i.e. prolonged np and shortened N4-b) may explain the reduced SRBSDV transmission in Si-amended plants. © 2021 Society of Chemical Industry.

Enhancing Climate Resilience of Rain-Fed Potato Through Legume Intercropping and Silicon Application

A large portion of sub-Saharan Africa is situated in belts of uncertain rainfall and are characterized by low soil fertility with limited capacity to adapt to and mitigate the impacts of climate change. A field study was conducted in the semi-humid potato-growing belt of Kenya to test the effect of legume intercropping and water soluble silicon (orthocilicic acid) on soil erosion, and use efficiency of light and water. Potato (Solanum tuberosum L.) was grown singly and intercropped with dolichos (Lablab purpureus L.) or hairy vetch (Vicia sativa L.). Each cropping system was subjected to granular water-soluble silicon (Si) amendment at two rates (2.5 kg Si ha-1 (+Si) vs 0 kg Si ha-1 (-Si)). Plants receiving Si maintained significantly higher (p < 0.05) percent relative leaf water content (62–89% vs 52–72% in controls) and exhibited higher concentrations of proline (1.99–2.91 vs 1–1.19 մmol g-1), soluble carbohydrates (28–59 vs 10–28 մmol g-1) and electrolyte conductance (1409–3903 vs 746–2307 mS cm-1). Legume intercropping enhanced groundcover establishment and reduced soil and nutrient losses by 45–80% compared with sole potato. Crop yields were 2–3 fold greater in intercropping relative to sole potato and were significantly greater in treatments subjected to Si application. Land equivalent ratios were above unity in intercropping but less than unity in sole potato, and were 8–20% increased by Si application. Use efficiency of water (5.99–9.09 Kg ha-1 m-3) and light (1.98–2.98 g MJ-1) were significantly greater under legume intercropping compared with sole potato (1.13–3.23 Kg ha-1 m-3 and 0.77–0.98 g MJ-1 respectively) and increased with Si application. Integrative use of Si and legume intercropping presents the smallholder farmers an opportunity to increase productivity of potato while enhancing resource use efficiency and soil fertility in the semi-humid tropics.

Silicon-regulated antioxidant and osmolyte defense and methylglyoxal detoxification functions co-ordinately in attenuating fluoride toxicity and conferring protection to rice seedlings

The objective of this manuscript was to demonstrate the efficacy of silicon supplementation in relieving the fluoride-induced damages in rice cultivar, Khitish. The exposure of seedlings to two different concentrations of fluoride, viz., 25 and 50 mg L−1 NaF caused increase in fluoride accumulation, as a result of which the seedlings suffered severe oxidative stress, as evident from growth inhibition, reduction in seed germination, tissue biomass, root and shoot length, decline in chlorophyll content, increases in electrolyte leakage, H2O2 content, lipid peroxidation (malondialdehyde content and lipoxygenase activity), protein carbonylation and protease activity. The extent of damage was more at higher fluoride concentration. Silicon amendment, irrespective of fluoride concentrations, led to large build-up of endogenous silicon level and brought considerable improvement in all the parameters examined with respect to fluoride stress. The fluoride-mediated enhancement in methylglyoxal level was lowered by silicon, because of the prominent activation of glyoxalase I and glyoxalase II. While the stress-mediated induction in antioxidative enzymes like GPOX, APX, SOD, GPX and GR was lowered by silicon, the inhibition in CAT activity was relieved. The antioxidative defense mechanism was also boosted up via enhanced content of total phenolics and carotenoids. However, the fluoride-mediated increase in anthocyanins, flavonoids, xanthophyll, ascorbate and reduced glutathione, and osmolytes like total amino acids, proline and glycine-betaine, were all lowered in presence of silicon, together with reduced PAL and P5CS activity. Overall, silicon reduced oxidative damages to develop fluoride-tolerant rice plants through augmentation of different antioxidant and osmolyte defense and methylglyoxal detoxification system.