Exogenous Application Of Silicon Research Articles

Assessment of yield and quality management with the exogenous application of silicon in contrasting wheat varieties under salinity stress

Assessment of yield and quality management with the exogenous application of silicon in contrasting wheat varieties under salinity stress

Exogenous application of silicon and selenium improves the tolerance of tomato plants to calcium nitrate stress

Silicon (Si) and selenium (Se) can improve the tolerance of plants to NaCl-induced salt stress. However, few studies are available on their regulatory effects on plants’ tolerance to calcium nitrate stress, which often occurs in protected facilities, causing secondary soil salinization. In this study, we report the effects of Si (6 mM) and Se (20 μM) applied separately or in combination on the growth, photosynthesis, oxidative damage, and nitrogen metabolism of tomato plants, as well as fruit quality under calcium nitrate stress. The results showed that applications of Si or Se alone or in combination improved the plant growth and photosynthetic performance and reduced oxidative damage of the stressed plants. Applications of Si and Se did not decrease the calcium accumulation in leaves of the stressed plants. Under calcium nitrate stress, the concentrations of NO3−, NO2− and NH4+ in leaves were significantly increased, while the activities of nitrogen assimilation-related enzymes (including nitrate reductase, nitrite reductase, glutamine synthase, glutamine-2-oxoglutarate aminotransferase and glutamate dehydrogenase) were decreased. Applications of Si and Se, especially their combined treatment, decreased the NO3−, NO2−, and NH4+ concentrations and enhanced the activities of nitrogen assimilation-related enzymes in the stressed plants. Applied Si and Se also decreased the nitrate and titratable acid concentrations and increased vitamin levels in tomato fruits under calcium nitrate stress. It is suggested that Si and Se improved the tomato plant growth and fruit quality under calcium nitrate stress by alleviating oxidative damage and promoting both photosynthesis and nitrogen assimilation.

Exogenous Application of Silicon and Sulfate Improved Drought Tolerance in Sunflowers Through Modulation of Morpho-physiological and Antioxidant Defense Mechanisms

Exogenous Application of Silicon and Sulfate Improved Drought Tolerance in Sunflowers Through Modulation of Morpho-physiological and Antioxidant Defense Mechanisms

Amelioration of Salt-Induced Damage on Paeonia ostii ‘Fengdan’ by Exogenous Application of Silicon

To investigate the amelioration of salt-induced damage on Paeonia ostii ‘Fengdan’ by exogenous silicon, we analyzed the photosynthetic and physiological characteristics of 1.5-year-old ‘Fengdan’ seedlings under NaCl stress by applying exogenous silicon (0, 0.75, and 1.5 mmol/L). Our results showed that the contents of the photosynthetic pigments chlorophyll a, chlorophyll b, and carotene, the transpiration rate, stomatal conductance, and intercellular CO2 were significantly enhanced under salt stress when silicon treatment was applied, implying that the net photosynthetic rate was greatly improved. In addition, the plant height, stem thickness, and above-ground dry biomass of tree peony seedlings were effectively increased under salt stress with low-concentration silicon (0.75 mmol/L) treatment, along with osmotic substance (SS, SP, and Pro) content, total polyamine (TP) contents, and the activities of antioxidant-related enzymes (SOD, POD, and CAT) and polyamine-related synthetases (ADC, ODC, and SAMDC). In the low-concentration silicon treatment, malondialdehyde (MDA), hydrogen peroxide (H2O2), and superoxide anions (O2−) were transformed quickly, which eventually reduced cell oxidative damage and improved seedling tolerance. This is an important finding in the understanding of how exogenous low-concentration silicon can alleviate salt-induced damage and promote the growth of tree peony seedlings, thus providing a new perspective on tree peony cultivation.

Modulation of Antioxidant Defense Mechanisms and Morpho-Physiological Attributes of Wheat through Exogenous Application of Silicon and Melatonin under Water Deficit Conditions

Although the individual influences of silicon (Si) and melatonin (MT) have been widely studied under various abiotic stresses, little is known about their interaction under drought stress. In this study, an experiment in pots was carried out to investigate the potential of an individual or combined foliar application of silicon (Si) and melatonin (ML) (control (ck), water spray, 4.0 mM Si, 200 µM ML, and 4.0 mM Si + 200 µM ML) on wheat grown at two different water-holding capacity levels (80% well-water condition and 40% drought stress) in order to check of grain yield and some important physiological characteristics. Under drought stress conditions, grain yield and yield attributes, water content and photosynthetic efficiency of wheat crops were significantly decreased. Application of Si+ ML significantly improved leaf pigments (Chl a, Chl b and Chll a + b), leaf relative water content (RWC), proline, total soluble sugars, and total soluble protein. As well as, the activities of important antioxidant enzymes, including catalase (CAT), superoxide dismutase (SOD), peroxidase (POD) and ascorbate peroxidase (APX) were effectively boosted through the combined application of Si + ML. This improvement was correlated with an obvious decrease in the levels of MDA, H2O2, and electrolyte leakage and increased water use efficiency. Conclusively, the combination of Si + ML significantly enhanced the 20.21% yield and various morpho-physiological attributes of drought-stressed wheat plants and can be recommended as a promising treatment to enhance wheat productivity in drought-affected regions. Additionally, the results of this study may open up a whole new area of research opportunities at the transcriptional level to further understand the mechanisms underlying how Si + ML integrates and interacts with plants under drought stress.

Silicon-Induced Morphological, Biochemical and Molecular Regulation in Phoenix dactylifera L. under Low-Temperature Stress.

Climate changes abruptly affect optimum growth temperatures, leading to a negative influence on plant physiology and productivity. The present study aimed to investigate the extent of low-temperature stress effects on date palm growth and physiological indicators under the exogenous application of silicon (Si). Date palm seedlings were treated with Si (1.0 mM) and exposed to different temperature regimes (5, 15, and 30 °C). It was observed that the application of Si markedly improved fresh and dry biomass, photosynthetic pigments (chlorophyll and carotenoids), plant morphology, and relative water content by ameliorating low-temperature-induced oxidative stress. Low-temperature stress (5 and 15 °C), led to a substantial upregulation of ABA-signaling-related genes (NCED-1 and PyL-4) in non Si treated plants, while Si treated plants revealed an antagonistic trend. However, jasmonic acid and salicylic acid accumulation were markedly elevated in Si treated plants under stress conditions (5 and 15 °C) in comparison with non Si treated plants. Interestingly, the upregulation of low temperature stress related plant plasma membrane ATPase (PPMA3 and PPMA4) and short-chain dehydrogenases/reductases (SDR), responsible for cellular physiology, stomatal conductance and nutrient translocation under silicon applications, was observed in Si plants under stress conditions in comparison with non Si treated plants. Furthermore, a significant expression of LSi-2 was detected in Si plants under stress, leading to the significant accumulation of Si in roots and shoots. In contrast, non Si plants demonstrated a low expression of LSi-2 under stress conditions, and thereby, reduced level of Si accumulation were observed. Less accumulation of oxidative stress was evident from the expression of superoxide dismutase (SOD) and catalase (CAT). Additionally, Si plants revealed a significant exudation of organic acids (succinic acid and citric acid) and nutrient accumulation (K and Mg) in roots and shoots. Furthermore, the application of Si led to substantial upregulation of the low temperature stress related soybean cold regulated gene (SRC-2) and ICE-1 (inducer of CBF expression 1), involved in the expression of CBF/DREB (C-repeat binding factor/dehydration responsive element binding factor) gene family under stress conditions in comparison with non Si plants. The current research findings are crucial for exploring the impact on morpho-physio-biochemical attributes of date palms under low temperature and Si supplementation, which may provide an efficient strategy for growing plants in low-temperature fields.

Exogenous application of silicon alleviates boron toxicity in rice seedlings

Exogenous application of silicon alleviates boron toxicity in rice seedlings

Exogenous application of silicon improves the performance of wheat under terminal heat stress by triggering physio-biochemical mechanisms

Due to climate change, temperature in late February and early March raised up which cause heat stress at reproductive stage (terminal growth phase of wheat crop) which has become the major causative factor towards low wheat production in arid and semiarid regions. Therefore; strategies need to be adopted for improving terminal heat stress tolerance in wheat. In this study, we assessed whether foliar application of silicon (Si) (2 and 4 mM) at terminal growth phase i.e. heading stage of wheat imposed to heat stress (37 ± 2 °C) under polythene tunnel could improve the performance of wheat. Results of the study revealed that heat stress significantly reduced the photosynthetic pigments (chlorophyll a, b and a + b and carotenoids) leading to a lower grain yield. However, a 4 mM Si application (foliar applied) at heading stage prominently increased the chlorophyll a, b and a + b and carotenoids of flag leaf by improving the activities of enzymatic antioxidants (catalase, peroxidase and superoxide dismutase) and osmoprotectants (soluble sugar protein and proline) under terminal heat stress. Improvements in the performance of wheat (chlorophyll contents, carotenoids, soluble sugar and proteins and proline and yield) with foliar application of Si were also observed under control conditions. Correlation analysis revealed strong association (r > 0.90) of chlorophyll contents and carotenoids with grain and biological yield. Negative correlation (−0.81 < r > −0.63) of physio-biochemical components (antioxidants, proline, soluble sugars and proteins) with yield revealed that under heat stress these components produced in more quantities to alleviate the effects of heat, and Si application also improved these physio biochemical components. In crux, foliar application of Si alleviates the losses in the performance of wheat caused by terminal heat stress by improving the antioxidant mechanism and production of osmoprotectants.

Amelioration of salt‐induced damage on alfalfa by exogenous application of silicon

AbstractThe present study was aimed to investigate the protective role of silicon (Si) from salt‐induced damages in alfalfa. Seedlings were treated with 200 mM NaCl plus three silicon levels (0, 0.75 and 1.5 mM) for 1 week. We observed that salt stress impacted plant growth remarkably, including height, root length, stem and leave weight, aboveground biomass and total biomass, chlorophyll a (chl a), chlorophyll b (chl b), total chlorophyll (total chl), chlorophyll fluorescence, K concentration and K/Na ratio. Consequently, electrolyte leakage (EL), superoxide dismutase (SOD) activity, Na concentration, proline, malondialdehyde (MDA), soluble sugar (SS) and soluble protein (SP) content were found to be raised significantly. After exogenously applying Si under salt stress, the EL, MDA, proline and Na content, except SOD activity, were observed to be dropped. Meanwhile, the chl a, chl b, and total chl and SS content, and chlorophyll fluorescence were found to be elevated. In terms of Si concentration, we found that the protective effects of Si were considerably better at lower concentration (0.75 mM) than higher (1.5 mM) one. Collectively, our results suggested that Si alleviate salt‐induced damage and promote alfalfa growth by changing physiological characteristics.

Interactive effect of silicon and mycorrhizal inoculation on growth, yield and water productivity of rice under water-deficit stress

Drought is a major abiotic stress limiting growth and productivity of field and horticultural crops. Exogenous application of silicon (Si) and arbuscular mycorrhizal fungi (AMF) inoculation has the potential to alleviate the adverse effect of drought stress on plant. A factorial experiment consisting of four monosilicic acid (MSA) doses (0, 75, 150 and 300 kg ha−1), two levels of AMF inoculation (inoculation of AMF [+AMF] and without inoculation of AMF [–AMF]) and three soil moisture regimes (100%, 75% and 50% field capacity [FC]) was conducted to evaluate the effect of Si and AMF inoculation on growth, yield and water productivity of rice under water-deficit stress. The soil moisture regimes of 75% and 50% FC indicate a 25% and 50% depletion of the maximum amount of water held in the soil, respectively, whereas 100% FC refers to the maximum amount of water held in the soil after gravitational water drainage stops. An overall reduction in growth and yield of rice was observed with decreasing soil moisture regime; however, application of 300 kg MSA ha−1 increased shoot dry matter by 28% compared with 0 kg MSA ha−1 under limited soil moisture availability of 75% and 50% FC. Similarly, grain yield was increased by 37% and 39% at 300 kg MSA ha−1 compared with the control in the –AMF and + AMF plants, respectively, under moderate soil moisture level of 75% FC. The corresponding increase at 50% FC was 52% and 55%, respectively. The present results demonstrated a synergistic effect of exogenous application of MSA at 300 kg ha−1 (60 kg ha−1 soluble Si) and AMF inoculation on rice under water-deficit stress.

Silicon-induced antioxidant defense and methylglyoxal detoxification works coordinately in alleviating nickel toxicity in Oryza sativa L.

Nickel (Ni), an essential nutrient of plant but very toxic to plant at supra-optimal concentration that causes inhibition of seed germination emergence and growth of plants as a consequence of physiological disorders. Hence, the present study investigates the possible mechanisms of Ni tolerance in rice seedlings by exogenous application of silicon (Si). Thirteen-day-old hydroponically grown rice (Oryza sativa L. cv. BRRI dhan54) were treated with Ni (NiSO4.7H2O, 0.25 and 0.5 mM) sole or in combination with 0.50 mM Na2SiO3 for a period of 3 days to investigate the effect of Si supply for revoking the Ni stress. Nickel toxicity gave rise to reactive oxygen species (ROS) and cytotoxic methylglyoxal (MG), accordingly, initiated oxidative stress in rice leaves, and accelerated peroxidation of lipids and consequent damage to membranes. Reduced growth, biomass accumulation, chlorophyll (chl) content, and water balance under Ni-stress were also found. However, free proline (Pro) content increased in Ni-exposed plants. In contrast, the Ni-stressed seedlings fed with supplemental Si reclaimed the seedlings from chlorosis, water retrenchment, growth inhibition, and oxidative stress. Silicon up-regulated most of the antioxidant defense components as well as glyoxalase systems, which helped to improve ROS scavenging and MG detoxification. Hence, these results suggest that the exogenous Si application can improve rice seedlings' tolerance to Ni-toxicity.

Exogenous Silicon Modulates Growth, Physio-Chemicals and Antioxidants in Barley (Hordeum vulgare L.) Exposed to Different Temperature Regimes

The exogenous application of silicon (Si) is reported to enhance tolerance of plants against various environmental stresses. Therefore, the present study was carried out to examine the influence of foliar applied Si (1.5 mM) on growth, physiochemical processes and antioxidant defense system of barley plants (cvs. Jow-83 and B-12026) under different regimes of temperature (20 °C (control), 25 °C, 30 °C, and 35 °C). High temperature (HT) regimes caused a significant (P < 0.001) decline in shoot (68% and 84%) and root (44% and 77%) dry masses, leaf area (66% and 81%), chlorophyll (Chl) a (11% and 70%), Chl b (69% and 71%), carotenoids (60% and 62%), anthocyanins (56%), total soluble proteins (62%) and phenolics (36% and 50%) contents in both cvs. Jow-83 and B-12026, respectively. A significant (P < 0.001) increase in superoxide dismutase (205% and 133%), peroxidase (128% and 88%) and catalase (127% and 87%) activities was recorded in stressed plants of both cultivars, respectively. Moreover, HT stress markedly (P < 0.001) increased hydrogen peroxide (H2O2) (54% and 75%) and malondialdehyde (MDA) (52% and 149%) levels in both cultivars that activated the oxidative stress. But, plants treated with Si showed better growth and had higher total soluble proteins (18% and 12%), anthocyanins (74% and 39%), flavonoids (31% and 27%) and phenolics (39% and 19%) as well as the activities of SOD (43% and 29%), POD (46% and 40%) and CAT (24% and 63%) enzymes. Application of Si reduced HT-mediated oxidative stress by decreasing the concentration of MDA (39% and 49%) and H2O2 (14% and 56%) and increased shoot (49% and 46%) and root (40% and 34%) dry masses, Chl a (10% and 86%), Chl b (82% and 81%), and carotenoids (53% and 33%) in both barley cultivars. Plants of cv. Jow-83 showed more tolerance to temperature regimes than that of cv. B-12026 as evident from higher plant dry masses. Thus, our findings exhibited that foliar-applied Si is an efficient strategy that can be used to enhance the tolerance of barley plants to HT stress.

Productivity, chemical composition and sensory quality of “Martaínha” chestnut variety treated with Silicon

ABSTRACTThe increasing demand for healthy products rises the pressure on the chestnut production due to their nutritional qualities and beneficial health effects. Martaínha chestnut variety is most well-adapted with great economic importance due to its precocity and technological properties. The exogenous application of Silicon has an important role in agriculture because of improvement of plants nutrition. Nevertheless, the knowledge of impact of Silicon application in the production, sensory quality and chemical composition of chestnut fruits is limited. The application of Si in leaves (SL) and soil (SS) have important action on the prophylactic properties and the promotion of chestnuts health. Moreover, higher number of healthy fruits, caliber, fruits without rotten and tortrix infection and lower water loss in post-harvest chestnuts, in SL and SS samples, highlights the Si positive action. Additionally this study emphasizes some positive effects of Silicon on the chemical and sensory profile.

Separate and combined effects of silicon and selenium on salt tolerance of wheat plants

Soil salinity is the leading global abiotic stress which limits agricultural production with an annual increment of 10%. Therefore; a pot experiment was conducted with the aim to alleviate the salinity effects on wheat seedlings through exogenous application of silicon (Si) and selenium (Se). Treatments included in the study were viz. (Ck) control (no NaCl nor Si and Se added), only salinity (50 mM NaCl), salinity + Si (50 mM NaCl with 40 mM Si), salinity + Se (50 mM NaCl with 40 mM Se) and salinity + Si + Se (50 mM NaCl + 40 mM Si + 40 mM Si). The salt stress impaired the growth (root and shoot dry weight, root: shoot ratio, seedlings biomass), water relations, photosynthetic attributes, transpiration rate and chlorophyll contents of wheat seedlings. Nonetheless, the foliar application of Si and Se alone and in combination improved the growth, water relations, photosynthetic attributes, transpiration rate and chlorophyll contents of wheat seedlings under stressed conditions. Moreover, an increase in antioxidant enzyme activity and accumulation of osmo-protectants (proline, soluble protein and soluble sugar) was noted under stressed conditions, which was more pronounced in wheat seedling which experienced combined application of Si and Se. To conclude that, foliar application of Si alone mitigated the adverse effect of salinity, while the combined application of Si and Se was proved to be even more effective in alleviating the toxic effects of salinity stress on wheat seedlings.

The effect of exogenous silicon on seed germination and seedling growth of wheat cultivars under salt stress conditions

ABSTRACT- Seed germination and early seedling growth are critical stages for plants establishment and production, particularly under salinity conditions. Exogenous application of silicon (Si) can enhance germination as well as seedling growth. In this experiment, the effect of priming with Si (0, 0.75, 1.5 and 2.25 mM sodium silicate) on seed germination and seedling growth under NaCl (0, 100 and 150 mM) conditions was studied in two wheat cultivars of Kavir (salt tolerant) and Shiraz (salt sensitive). The experiment was designed as a factorial based on completely randomized design with three replications in the laboratoryof college of Agriculture, Shiraz University, in 2012. Results showed that seed priming by Si improved germination percentage, germination rate, vigor index, shoot and root length and seedling dry weight in both stress and non-stress conditions. Moreover, Si increased K+ uptake and K+/Na+ ratio and decreased Na+ content of cultivars with the effect of 2.25 mM being more pronounced. On the contrary, salt stress reduced the above traits andK+ uptake and K+/Na+ ratio and increased mean germination timeand Na+ uptake in both cultivars with the negative effects of 150 mMNaCl being more severe. However, the tolerant cultivar (Kavir) accumulated less Na+ and more K+ and had greater K+/Na+ ratio compared to non-tolerant cultivar (Shiraz). Although the salinity adversely affected seed germination and seedling growth in both cultivars, Kavir (tolerant cultivar) was less affected. It was concluded that priming with Si may promote germination and subsequent seedling growth of wheat cultivars under salinity conditions by reducing Na+ in favor of K+ accumulation.

Exogenous application of silicon at the boot stage decreases accumulation of cadmium in wheat (Triticum aestivum L.) grains

A pot experiment was conducted to assess role of added silicon (Si) in alleviating cadmium-induced oxidative stress in wheat cultivars (AARI-2011, Cd-sensitive and FSD-2008, Cd-tolerant). Plants were exposed to different levels of CdCl2 (0, 25, 50, and 75 μM Cd/kg) along with sodium silicate (0 and 1.5 mM) at the boot stage. Cadmium stress resulted in a marked decline in various growth attributes, photosynthetic pigments, and the activities of some enzymatic antioxidants, particularly in Cd-sensitive wheat cultivar. Application of Si reduced Cd-mediated oxidative stress and increased photosynthetic pigments and proline contents in both wheat cultivars. Although Si application affected the shoot and grain Cd2+ concentrations differently in both cultivars, it decreased Cd2+ concentrations in the grains in both wheat cultivars. However, at higher Cd2+ concentrations, Si was very effective in decreasing Cd2+ concentrations in the grains of Cd-tolerant cultivar. The alleviatory effects of Si on Cd2+ concentrations in grain could be attributed to the altered Cd2+ uptake and translocation, particularly at higher Cd2+ concentrations in both wheat cultivars. The effectiveness of Si to reduce grain-Cd2+ concentrations in diverse wheat cultivars suggested its use as soil amendments in the Cd-polluted environments.

Foliar spray of phyto-extracts supplemented with silicon: an efficacious strategy to alleviate the salinity-induced deleterious effects in pea (Pisum sativum L.)

A pot culture study was conducted to assess the ameliorative effect of silicon, Melia azadirachta leaf extract, and sugar beet root extract, each applied individually or in different combinations, on salinity-induced detrimental effects in pea (Pisum sativum L.). Salinity markedly inhibited the growth, various gas exchange attributes, total phenol contents, membrane stability index, and productivity. On the other hand, lipid peroxidation, electrolyte leakage, H2O2 content, antioxidant activities, and leaf free proline and glycinebetaine contents were significantly enhanced by salinity. However, exogenously applied Si and phyto-extracts markedly alleviated the salinity-induced drastic effects on growth, gas exchange attributes, and productivity. Both phyto-extracts supplemented with silicon gave highly salinity mitigating effects by markedly improving growth, gas exchange attributes, enzymatic activities, osmolytes, and yield. The phyto-extracts and Si suppressed lipid peroxidation, electrolyte leakage, and H2O2 content by strengthening the enzymatic and nonenzymatic (proline and glycinebetaine) antioxidant defense system. The phyto-extracts and Si application also checked the root/leaf sodium and chloride contents, but improved the silicon contents. Thus, it can be concluded that exogenous application of silicon in combination with phyto-extracts of M. Azadirachta and sugar beet is a highly effective ameliorative approach to alleviate salinity-induced hazardous effects in plants, especially in pea, grown under a saline regime.

Influence of Exogenous Application of Silicon and Potassium on Physiological Responses, Yield, and Yield Components of Salt-Stressed Wheat

To investigate the effect of exogenous application of silicon and potassium on some physiological responses, yield, and yield components of two wheat cultivars (Pishgam and Alvand) grown under salt-stress conditions, a field experiment was conducted at the Agricultural and Natural Resources Research Centre in East Azerbaijan, Iran, during 2012 and 2013 growing seasons. The experiment was arranged in factorial design based on randomized complete blocks design with three replications in each year. Wheat seeds were sown in saline soil (10 dS m−1) and irrigated with saline water (4 dS m−1). The plants were sprayed with silicon and potassium solutions at 0, 2, and 4 mM and 0, 100, 200, and 300 mM concentrations, respectively. The results demonstrated that silicon and potassium application improved antioxidant enzyme activity, chlorophyll content, photosynthesis rate, potassium uptake, yield, and yield components in both wheat cultivars. Although silicon and potassium had significant effects on all studied traits, there was a great interactive effect between them. When these two elements were applied on plants, the positive effect was more pronounced. Among all treatments, the most effective treatment was 4 mM silicon and 300 mM potassium. The greatest enzyme activity, chlorophyll content, photosynthesis rate, potassium uptake, yield, and yield components and the lowest proline, malondialdehyde, and sodium accumulations were observed in this treatment.

Interactive Effects of Silicon and Potassium Nitrate in Improving Salt Tolerance of Wheat

Adequate regulation of mineral nutrients might be effective to ameliorate the deleterious effects of salts and help to sustain crop productivity, particularly in glycophytes, under salt stress. In this study, laboratory and greenhouse experiments were carried out at Agricultural and Natural Resources Research Centre in East Azerbaijan, Iran, to investigate the interactive effects of silicon and potassium nitrate in alleviating NaCl induced injuries in wheat (Triticum aestivum L.). In the laboratory experiment, three winter wheat cultivars Pishgam, Afagh and Alvand were grown on sterile filter paper moistened with 20, 40, 60, 80, and 100 mmol L−1 NaCl solution. Results revealed that wheat cultivars were significantly different in their growth response to different concentrations of NaCl and Pishgam was found to be the most tolerant to NaCl stress, and used in the second part of study. In the greenhouse experiment, Pishgam was grown in a hydroponic system subjected to different NaCl levels (20, 60 and 100 mmol L−1) and treated by silicon (0, 2 and 4 mmol L−1, final concentration in nutrient solution using K2SiO3) and potassium nitrate (0, 0.5, 1, and 2 mmol L−1, foliar application). The experimental design was factorial based on a completely randomized design with three replications. It was found that NaCl stress significantly increased proline accumulation and sodium content in the plant tissues while decreased potassium uptake and accumulation by plants. Moreover, plant weight, 100-seed weight, relative water content, chlorophyll content, and photosynthesis were also significantly affected by varying levels of NaCl. However, exogenous application of silicon and potassium nitrate reduced sodium uptake, increased potassium and consequently improved plant weight, 100-seed weight, seed yield, ear length, and photosynthesis rate. This study suggested that utilization of the salt-tolerant cultivar (Pishgam) combined with proper foliar application of potassium nitrate (2 mmol L−1) and silicon (4 mmol L−1) at the wheat booting stage might be a promising approach to obtain higher grain yield on saline lands.

Enhancement of Biocontrol Activity of Cryptococcus laurentii by Silicon and the Possible Mechanisms Involved

ABSTRACT Exogenous application of silicon (Si) in the form of sodium metasilicate reduced disease development caused by Penicillium expansum and Monilinia fructicola in sweet cherry fruit at 20 degrees C. The inhibition of fruit decay was correlated closely with Si concentrations. Silicon at concentrations of 1%, in combination with the biocontrol agent Cryptococcus laurentii at 1 x 10(7) cells per ml, provided synergistic effects against both diseases. Population dynamics of C. laurentii were stimulated by Si 48 h after the yeast treatment in the wounds of sweet cherry fruit. Silicon strongly inhibited spore germination and germ tube elongation of P. expansum and M. fructicola in vitro. Based on results with scanning electron microscopy, growth of both pathogens was significantly inhibited by Si in the wounds of sweet cherry fruit. Compared with the wounded water control, Si treatment induced a significant increase in the activities of phenylalanine ammonia-lyase, polyphenoloxidase, and peroxidase in sweet cherry fruit but did not increase the levels of lignin. Application of Si activated a cytochemical reaction and caused tissue browning near the site of wounding. Based on our studies, the improvement in biocontrol efficacy of antagonistic yeast when combined with Si may be associated with the increased population density of antagonistic yeast by Si, the direct fungitoxicity property of Si to the pathogens, and the elicitation of biochemical defense responses in fruit.