Transcriptome Analysis Reveals an Essential Role of Exogenous Brassinolide on the Alkaloid Biosynthesis Pathway in Pinellia Ternata.

Pinellia ternata (Thunb.) Druce is a traditional medicinal plant containing a variety of alkaloids, which are important active ingredients. Brassinolide (BR) is a plant hormone that regulates plant response to environmental stress and promotes the accumulation of secondary metabolites in plants. However, the regulatory mechanism of BR-induced alkaloid accumulation in P. ternata is not clear. In this study, we investigated the effects of BR and BR biosynthesis inhibitor (propiconazole, Pcz) treatments on alkaloid biosynthesis in the bulbil of P. ternata. The results showed that total alkaloid content and bulbil yield was enhanced by 90.87% and 29.67% under BR treatment, respectively, compared to the control. We identified 818 (476 up-regulated and 342 down-regulated) and 697 (389 up-regulated and 308 down-regulated) DEGs in the BR-treated and Pcz-treated groups, respectively. Through this annotated data and the Kyoto encyclopedia of genes and genomes (KEGG), the expression patterns of unigenes involved in the ephedrine alkaloid, tropane, piperidine, pyridine alkaloid, indole alkaloid, and isoquinoline alkaloid biosynthesis were observed under BR and Pcz treatments. We identified 11, 8, 2, and 13 unigenes in the ephedrine alkaloid, tropane, piperidine, and pyridine alkaloid, indole alkaloid, and isoquinoline alkaloid biosynthesis, respectively. The expression levels of these unigenes were increased by BR treatment and were decreased by Pcz treatment, compared to the control. The results provided molecular insight into the study of the molecular mechanism of BR-promoted alkaloid biosynthesis.

Principal Component Analysis to Assess the Changes of Yield and Quality in Pinellia ternata at Different Stages after Brassinolide Treatments.

Brassinolide (BR) is the "sixth class" plant hormone, which plays an important role in various physiological and biochemical processes of plants. The wide variety of functions of Pinellia ternata means that there is huge demand for it and thus it is in short supply. This paper mainly assessed the changes of yield and quality in P. ternata at different stages after BR treatments by principal component analysis, in order to improve the yield and quality of P. ternata and at the same time determine the best harvest time. The results showed that the tuber yield of P. ternata was significantly increased by BR treatments at different stages (except for the 15th day). After the 15th, 45th, 60th, 75th, 90th, and 105th day of treatments, the tuber yield of P. ternata reached peak values at 0.10 (0.65 g), 0.50 (1.97 g), 0.50 (1.98 g), 1.00 (2.37 g), 1.00 (2.84 g), and 2.00 mg/L (3.76 g) BR treatment, respectively. The optimal harvest time was the 75th day after 0.10, 0.50, and 1.00 mg/L BR treatments, which not only significantly improved the yield of P. ternata, but also retained high level of total alkaloids in the tubers (20.89, 5.37, and 13.44%) and bulbils (9.74, 20.42, and 13.62%), high total flavone content in the tubers (17.66, 16.26, and 12.74%) and bulbils (52.63, 12.79, and 38.69%), and high ß-sitosterol content in the tubers (25.26, 16.65, and 0.62%) of P. ternata, compared with the control, respectively.

Brassinolide Soaking Reduced Nitrite Content and Extended Color Change and Storage Time of Toona sinensis Bud during Low Temperature and Near Freezing-Point Temperature Storage.

Low temperatures are often used to preserve fruits and vegetables. However, low-temperature storage also causes problems, such as chilling injury, nitrite accumulation, and browning aggravation in plants. This study investigated the effects of brassinolide (BR,1.0 mg L-1) solution soaking, storage temperatures (-2 ± 0.5 °C, 4 ± 0.5 °C, and 20 ± 1 °C), and their combinations on nitrite content, color change, and quality of stored Toona sinensis bud. The results showed that low temperature (LT, 4 ± 0.5 °C) and near freezing-point temperature (NFPT, -2 ± 0.5 °C) storage effectively inhibited the decay of T. sinensis bud compared to room temperature (20 ± 1 °C, the control). The combined treatments of BR with LT or NFPT reduced nitrite content and maintained the color and the contents of vitamin C, carotenoids, saponins, ß-sitosterol, polyphenol, anthocyanin, flavonoids, and alkaloids in T. sinensis bud. BR soaking delayed the occurrence of chilling injury during NFPT storage. Meanwhile, BR soaking enhanced the DPPH radical scavenging activity, ABTS activity, and FRAP content by increasing SOD and POD activity and the contents of proline, soluble, and glutathione, thus decreasing MDA and hydrogen peroxide content and the rate of superoxide radical production in T. sinensis bud during NFPT storage. This study provides a valuable strategy for postharvest T. sinensis bud in LT and NFPT storage. BR soaking extended the shelf life during LT storage and maintained a better appearance and nutritional quality during NFPT storage.

Incorporation of Na+/H+ antiporter gene from Aeluropus littoralis confers salt tolerance in soybean (Glycine max L..

To develop a salt-tolerant soybean (Glycine max L.) cultivar, a minimal linear Na+/H+ antiporter gene cassette (35S CaMV promoter, open-reading-frame of AINHX1 from Aeluropus littoralis and NOS terminator) was successfully expressed in soybean cultivar TF-29. Southern and Northern blot analysis showed that AlNHX1 was successfully incorporated into the genome and expressed in the transgenic plants. The AlNHX1 transgenic plant lines exhibited improved growth in severe saline condition (150 mM NaCl). The transgenic lines accumulated a lower level of Na+ and a higher level of K+ in the leaves than wild-type plants under saline condition (150 mM NaCl). Observations on the chlorophyll content, photosynthetic rates, malondialdehyde and relative electrical conductivity indicated that transgenic plants exhibited tolerance to salt stress, growing normally at salt concentrations up to 150 mM. These results demonstrated that AlNHX1 was successfully transferred into soybean and the salt-tolerance was improved by the overexpression of AlNHX1.

Waterlogging faced by bulbil expansion improved the growth of Pinellia ternata and its effect reinforced by brassinolide.

The bulbil expansion of P. ternata is a key period for its yield formation, and the process of bulbil expansion is often subjected to short-term heavy precipitation. It is not clear whether the short-term waterlogging can affect bulbil expansion. Brassinolide (BR) is widely believed to enhance plant tolerance to abiotic stress. The study investigated the effects of normal water (C), waterlogging (W), waterlogging + BR (W + B), waterlogging + propiconazole (W + P) on P. ternata at the bulbil expansion period in order to assess P. ternata's ability to cope with waterlogging during the bulbil expansion stage and the regulation effects of BR on the process. The biomass of P. ternata was significantly increased after waterlogging. W treatment significantly reduced the H2O2 and MDA contents, the rate of O2⋅- production and the activities of antioxidant enzymes compared with the C group. AsA and GSH contents were significantly reduced by W treatment. However, the ratios of AsA/DHA and GSH/GSSG were slightly affected by W treatment. The rate of O2∙- production and H2O2 content in W + B group were significantly lower than those in W group. The POD, APX, and GR activities, and GSH content in W + B group were evidently increased compared with the W group. Soluble sugar and active ingredients contents were significantly increased after waterlogging, and the enhancement was reinforced by BR. In conclusion, waterlogging reduced oxidative stress in P. ternata under the experimental conditions. BR treatment under waterlogging had a positive effect on P. ternata by enhancing antioxidant capacity and promoting the accumulation of soluble sugars and active ingredients.

Selenium alleviates the adverse effects of microplastics on kale by regulating photosynthesis, redox homeostasis, secondary metabolism and hormones.

Kale is a functional food with anti-cancer, antioxidant, and anemia prevention properties. The harmful effects of the emerging pollutant microplastic (MP) on plants have been widely studied, but there is limited research how to mitigate MP damage on plants. Numerous studies have shown that Se is involved in regulating plant resistance to abiotic stresses. The paper investigated impact of MP and Se on kale growth, photosynthesis, reactive oxygen species (ROS) metabolism, phytochemicals, and endogenous hormones. Results revealed that MP triggered a ROS burst, which led to breakdown of antioxidant system in kale, and had significant toxic effects on photosynthetic system, biomass, and accumulation of secondary metabolites, as well as a significant decrease in IAA and a significant increase in GA. Under MP supply, Se mitigated the adverse effects of MP on kale by increasing photosynthetic pigment content, stimulating function of antioxidant system, enhancing secondary metabolite synthesis, and modulating hormonal networks.

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.

Comparative analysis of the effects of microplastics and nitrogen on maize and wheat: Growth, redox homeostasis, photosynthesis, and AsA-GSH cycle.

Microplastics (MPs) pose a significant threat to the function of agro-ecosystems. At present, research on MPs has mainly focused on the effects of different concentrations or types of MPs on a crop, while ignoring other environmental factors. In agricultural production, the application of nitrogen (N) fertilizer is an important means to maintain the high yield of crops. The effects of MPs and N on growth parameters, photosynthetic system, active oxygen metabolism, nutrient content, and ascorbate-glutathione (AsA-GSH) cycle of maize and wheat were studied in order to explicit whether N addition could effectively alleviate the effects of MPs on maize and wheat. The results showed that MPs inhibited the plant height of both maize and wheat, and MPs effects on physiological traits of maize were more severe than those of wheat, reflecting in reactive oxygen metabolism and restriction of photosynthetic capacity. Under the condition of N supply, AsA-GSH cycle of two plants has different response strategies to MPs: Maize promoted enzyme activity and co-accumulation of AsA and GSH, while wheat tended to consume AsA and accumulate GSH. N application induced slight oxidative stress on maize, which was manifested as an increase in hydrogen peroxide and malonaldehyde contents, and activities of polyphenol oxidase and peroxidase. The antioxidant capacity of maize treated with the combination of MPs + N was better than that treated with N or MPs alone. N could effectively alleviate the adverse effects of MPs on wheat by improving the antioxidant capacity.

Brassinolide as potential rescue agent for Pinellia ternata grown under microplastic condition: Insights into their modulatory role on photosynthesis, redox homeostasis, and AsA-GSH cycling.

Microplastic (MP), as a new pollutant, not only affects the growth and development of plants but also may affect the secondary metabolites of plants. The anti-tumor role of Pinellia ternata is related to secondary metabolites. The role of brassinolide (BR) in regulating plant resistance is currently one of the research hotspots. The paper mainly explores the regulation of BR on growth and physiology of Pinellia ternata under MP stress. The experimental design includes two levels of MP (0, 1%) and two levels of BR (0, 0.1 mg/L). MP led to a marked reduction in plant height (15.0%), Fv/Fm (3.2%), SOD and APX activity (15.0%, 5.1%), whereas induced an evident raise in the rate of O2·- production (29.6%) and GSH content (4.4%), as well as flavonoids (6.8%), alkaloids (75%), and ß-sitosterol (26.5%) contents. Under MP addition, BR supply significantly increased plant height (15.7%), aboveground and underground biomass (16.1%, 10.3%), carotenoid and GSH content (11.8%, 4.2%), Fv/Fm (2.9%), and activities of SOD, GR, and MDHAR (32.2%, 21.08%, 20.9%). These results indicate that MP suppresses the growth of P. ternata, although it promotes secondary metabolism. BR can alleviate the inhibitory effect of MP on growth by improving photosynthesis, redox homeostasis, and the AsA-GSH cycle.

Exogenous brassinolide improves the antioxidant capacity of Pinellia ternata by enhancing the enzymatic and nonenzymatic defense systems under non-stress conditions.

Brassinolide (BR) improves the antioxidant capacity of plants under various abiotic stresses. However, it is not clear about the effect of BR on the antioxidant capacity in plants under non-stress conditions. In the present study, the antioxidant defense response of Pinellia ternata was to be assessed by applying BR and propiconazole (Pcz) under non-stress conditions. BR treatment enhanced the flavonoid content, peroxidase, and ascorbate peroxidase (APX) activity by 12.31, 30.62, and 25.08% and led to an increase in 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity by 4.31% and a decrease in malondialdehyde content by 1.04%. Exogenous application of BR improved the expression levels of PAL, CHS, CHI, and DFR genes by 3. 18-, 3. 39-, 2. 21-, and 0.87-fold in flavonoid biosynthesis, PGI, PMI, and GME genes by 6. 60-, 1437. 79-, and 3.11-fold in ascorbic acid (ASA), biosynthesis, and γECs and GSHS genes by 6.08- and 2.61-fold in glutathione (GSH) biosynthesis pathway, and the expression of these genes were inhibited by Pcz treatment. In addition, BR treatment promoted the ASA-GSH cycle by enhancing the expression of APX, DHAR, and MDHAR genes, which were enhanced by 3. 33-, 157. 85-, and 154.91-fold, respectively. These results provided novel insights into the effect of BR on the antioxidant capacity in bulbil of P. ternata under non-stress conditions and useful knowledge of applying BR to enhance the antioxidant capacity of plants.

The combined treatments of brassinolide and zeaxanthin better alleviate oxidative damage and improve hypocotyl length, biomass, and the quality of radish sprouts stored at low temperature.

The rot and deterioration of sprouts are closely related to their physiological state and postharvest storage quality. The study investigated the influences of brassinolide, zeaxanthin, and their combination on physiological metabolism, chlorophyll fluorescence, and nutritional quality of radish sprouts stored at 4 °C. The combined treatments enhanced hypocotyl length, fresh weight, contents of secondary metabolites, nutritional ingredients, glutathione, the photoprotective capacity of PSII, and FRAP level in radish sprouts compared with zeaxanthin alone. The combined treatments enhanced hypocotyl length, fresh weight, glutathione content, Fv/Fm value, and antioxidant capacity in sprouts compared to brassinolide alone. The combined treatment of zeaxanthin and brassinolide could make radish sprouts keep high biomass and antioxidant capacity by increasing the contents of stress-resistant metabolites and by weakening the photoinhibition of PSII in radish sprouts stored at 4 °C.

Brassinolide soaking and preharvest UV-B radiation influence the shelf life of small black bean sprouts.

This study explored the effects of brassinolide (BR) soaking, preharvest ultraviolet-B (UV-B) radiation, and their combined treatments on physiological characteristics, chlorophyll fluorescence, and quality of small black bean sprouts during storage. Results indicated that the combined treatments significantly enhanced contents of flavone, free amino acid, and photosynthetic pigment, and activities of phenylalanine ammonia lyase (PAL) and 2-diphenyl-1-picrylhydrazyl(DPPH) radical scavenging in sprouts stored for 5 days compared with BR treatment alone. The combined treatments significantly increased total phenols content and PAL activity, and reduced malonaldehyde content in sprouts compared with UV-B radiation alone. The inhibitory effect of BR or UV-B on fluorescence of photosystem II was weakened by their combined treatments. Comprehensive analysis indicated that the combined treatments could be used to maintain postharvest small black bean sprouts with high levels of nutritional ingredients by probably keeping high photosynthetic capacity, PAL activity, and DPPH radical scavenging rate in sprouts.

Inhibitory effect of paeoniflorin on IgE-dependent and IgE-independent mast cell degranulation in vitro and vivo.

The incidence of allergic diseases has increased to such a point that they have become common and have reached epidemic levels. However, their pathogenesis is not fully understood. Paeoniae Radix Rubra is a traditional Chinese medicine that is also used as a dietary supplement. Its main active ingredient is paeoniflorin. Paeoniflorin has good anti-inflammatory, immunomodulation, and antitumor effects. It is utilized in the treatment of various diseases in clinical settings. However, its effects on type I allergies and pseudoallergic reactions have not been comprehensively studied. In this study, we aimed to use DNP-IgE/DNP-BSA and C48/80 to simulate type I allergies and pseudoallergic reactions to evaluate the therapeutic effects of paeoniflorin to these diseases and identify its molecular mechanisms in cell degranulation both in vivo and in vitro. Results showed that paeoniflorin inhibited the degranulation of RBL-2H3 cells induced by these two stimuli (IgE-dependent and IgE-independent stimuli) in a dose-dependent manner. Moreover, qPCR and western blot analyses indicated that paeoniflorin may regulate the IgE/FcεR I, MRGPRB3, and downstream signal transduction pathways to exert its therapeutic effects on type I allergies and pseudoallergic reactions. In addition, DNP-IgE/DNP-BSA and compound 48/80 were used to induce the establishment of a passive cutaneous anaphylaxis mouse model. Paeoniflorin was found to suppress the extravasation of Evans Blue and tissue edema in the ears, back skin, and paws of the mice. This result further confirmed that paeoniflorin has a notable therapeutic effect on type I allergies and pseudoallergic reactions. Therefore, paeoniflorin could potentially be used as a drug for the treatment of type I allergies and pseudoallergic reactions. This study provides new insights into expanding the treatment range of paeoniflorin and its pharmacological mechanism.

Regulation Mechanism of Exogenous Brassinolide on Bulbil Formation and Development in Pinellia ternata.

The bulbil is the propagative organ of the P. ternata, which has a great effect on the yield of P. ternata. It is well known that plant hormones play important roles in bulbil formation and development. However, there is not clear about brassinolide (BR) regulation on bulbil formation and development. In this study, we revealed the effects of BR and BR biosynthesis inhibitors (propiconazole, Pcz) application on the histological observation, starch and sucrose metabolism, photosynthesis pathway, and hormone signaling pathway of P. ternata. The results showed that BR treatment reduced starch catabolism to maltodextrin and maltose in bulbil by decreasing BAM and ISA genes expression and increased cellulose catabolism to D-glucose in bulbil by enhancing edg and BGL genes expression. BR treatment enhanced the photosynthetic pigment content and potential maximum photosynthetic capacity and improved the photoprotection ability of P. ternata by increasing the dissipation of excess light energy to heat, thus reduced the photodamage in the PSII center. BR treatment increased the GA and BR content in bulbil of P. ternata, and decreased the ABA content in bulbil of P. ternata. Pcz treatment increased the level of GA, SL, ABA, and IAA in bulbil of P. ternata. BR regulated the signal transduction of BR, IAA, and ABA to regulate the formation and development of bulbil in P. ternata. These results provide molecular insight into BR regulation on bulbil formation and development.

The changes in quality ingredients of Qi chrysanthemum flowers treated with elevated UV-B radiation at different growth stages.

The paper mainly reported the changes in quality ingredients of Qi chrysanthemum flowers treated with elevated UV-B radiation at different growth stages. The experiment included two levels of UV-B radiation (ambient UV-B, a 10% increase in ambient UV-B). Elevated UV-B radiation was carried out for 10-days during seedling, vigorous growth, bud and flower stages of Qi chrysanthemum, respectively. Elevated UV-B treatments applied during four development stages did not significantly affect flower yield, the rate of superoxide radical production and malondialdehyde concentration in flowers, while increased free amino acid concentration. The amino acid concentration induced by elevated UV-B radiation applied during bud stage was higher than that during the other stages. Elevated UV-B radiation applied during vigorous growth (except for flavone), bud and flower stages of chrysanthemum significantly increased hydrogen peroxide concentration, phenylalanine ammonia lyase enzyme activity, vitamin C, chlorogenic acid and flavone concentrations in flowers. These results suggested that active and nutritional ingredients in flowers of chrysanthemum could be increased by elevated UV-B radiation applied during the later growth stages of chrysanthemum. The paper supplied a simple and environmental-friendly method to improve quality of medicinal plants.

Biochemical traits and proteomic changes in postharvest flowers of medicinal chrysanthemum exposed to enhanced UV-B radiation.

The article studied UV-B effects on biochemical traits and proteomic changes in postharvest flowers of medicinal chrysanthemum. The experiment about UV-B effects on biochemical traits in flowers included six levels of UV-B treatments (0 (UV0), 50 (UV50), 200 (UV200), 400 (UV400), 600 (UV600) and 800 (UV800) µWcm(-2)). UV400, UV600 and UV800 treatments significantly increased the contents of hydrogen peroxide, malondialdehyde and UV-B absorbing compounds, and the activity of phenylalanine ammonia lyase enzyme over the control. The contents of chlorogenic acid and flavone in flowers were significantly increased by UV-B treatments (except for UV50 and UV800). Two-dimensional gel electrophoresis was utilized to analyze proteomic changes in flowers with or without UV-B radiation. Results indicated that 43 protein spots (>1.5-fold difference in volume) were detected, including 19 spots with a decreasing trend and 24 spots with an increasing trend, and 19 differentially expressed protein spots were successfully indentified by MALDI-TOF MS. The indentified proteins were classified based on functions, the most of which were involved in photosynthesis, respiration, protein biosynthesis and degradation and defence. An overall assessment using biochemical and differential proteomic data revealed that UV-B radiation could affect biochemical reaction and promote secondary metabolism processes in postharvest flowers.

Effects of Enhanced UV-B Radiation on Biochemical Traits in Postharvest Flowers of Medicinal Chrysanthemum.

This article reported UV-B radiation effects on biochemical traits in postharvest flowers of chrysanthemum. The experiment included six levels of UV-B radiation (UV0, 0 µW cm(-2); UV50, 50 µW cm(-2); UV200, 200 µW cm(-2); UV400, 400 µW cm(-2); UV600, 600 µW cm(-2) and UV800, 800 µW cm(-2). Enhanced UV-B radiation significantly increased hydrogen peroxide content (except for UV50), but did not evidently affect malondialdehyde content in flowers. Chlorophyll b and total chlorophyll content were significantly increased by UV600 and UV800. UV400 and UV600 significantly increased anthocyanins, carotenoids and UV-B absorbing compounds content, and the activities of phenylalanine ammonia lyase (PAL) and cinnamic acid-4-hydroxylase (C4H) over the control. 4-coumarate CoA ligase (4CL) activity was significantly decreased by enhanced UV-B radiation (except for UV50). The relationships between UV-B radiation intensities and the activities of secondary metabolism enzymes were best described by a second-order polynomial. The R(2) values for UV-B radiation intensities and the activities of PAL, C4H and 4CL were 0.8361, 0.5437 and 0.8025, respectively. The results indicated that enhanced UV-B radiation could promote secondary metabolism processes in postharvest flowers, which might be beneficial for the accumulation of medically active ingredients in medicinal plants. The optimal UV-B radiation intensities in the study were between UV400-UV600.

The effects of UV-B radiation intensity on biochemical parameters and active ingredients in flowers of Qi chrysanthemum and Huai chrysanthemum.

The article studied UV-B effects on biochemical parameters and active ingredients in flowers of Qi chrysanthemum and Huai chrysanthemum during the bud stage. The experiment included four UV-B radiation levels (CK, ambient UV-B; T1, T2 and T3 indicated a 5%, 10% and 15% increase in ambient UV-BBE, respectively) to determine the optimal UV-B radiation intensity in regulating active ingredients level in flowers of two chrysanthemum varieties. Flower dry weight of two cultivars was not affected by UV-B radiation under experimental conditions reported here. UV-B treatments significantly increased the rate of superoxide radical production, hydrogen peroxide (H2O2) (except for T1) and malondialdehyde concentration in flowers of Huai chrysanthemum and H2O2 concentration in flowers of Qi chrysanthemum. T2 and T3 treatments induced a significant increase in phenylalanine ammonia lyase enzyme (PAL) activity, anthocyanins, proline, ascorbic acid, chlorogenic acid and flavone content in flowers of two chrysanthemum varieties, and there were no significant differences in PAL activity, ascorbic acid, flavone and chlorogenic acid content between the two treatments. These results indicated that appropriate UV-B radiation intensity did not result in the decrease in flower yield, and could regulate PAL activity and increase active ingredients content in flowers of two chrysanthemum varieties.

The effects of selenium on physiological traits, grain selenium content and yield of winter wheat at different development stages.

The paper evaluated the effects of Se application time and rate on physiological traits, grain Se content, and yield of winter wheat by field experiment. Se application significantly increased grain Se content and yield, and the increased amount treated with 20 and 30 mg Se L(-1) was the highest. At blooming-filling stage, Se application significantly increased grain Se content, but did not affect yield. Chlorophyll content was increased by Se application, and the increased amount at heading-blooming stage was higher than that in wheat leaves at the other stages. At four development stages, Se treatments (except for 10 mg Se L(-1) at jointing-heading stage) significantly decreased the rate of superoxide (O(2) (-)) radical production. At heading-blooming (except for 50 mg Se L(-1)) and blooming-filling stages, hydrogen peroxide (H(2)O(2)) content was significantly decreased by Se treatments. The rate of O(2) (-) production and H(2)O(2) content at 20 and 30 mg Se L(-1) was the lowest. Se treatments (except for 10 mg Se L(-1) at regreening-jointing and blooming-filling stages) also induced an evident decrease in malondialdehyde content. Proline content induced by Se treatments at jointing-heading and heading-blooming stages was higher than that in wheat leaves at regreening-jointing and blooming-filling stages. At four development stages, Se treatments all significantly increased glutathione peroxidase activity, and the treatments with 20 and 30 mg Se L(-1) also evidently increased reduced glutathione content. These results suggested that Se application at different development stages increased antioxidant capacity of wheat, reduced oxidant stress to some extent, and the effects of Se treatments was the best if Se concentration ranged between 20 and 30 mg Se L(-1). In addition, Se application time was more beneficial for Se accumulation and yield in wheat grain at heading-blooming stage.

Silicon improves the tolerance of wheat seedlings to ultraviolet-B stress.

Enhanced ultraviolet-B (UV-B) irradiation is one of the most important abiotic stresses that could influence the growth and physiological traits of plants. In this work, we reported the effects of silicon on the growth and physiological characteristics of wheat seedlings (Triticum aestivum L. cv Hengmai5229) subject to UV-B stress. Treatments with silicon significantly increased total biomass and chlorophyll (a + b) content, and reduced malondialdehyde (MDA) content and the rate of superoxide radical (O(2) (-) ) production in wheat seedlings subjected to UV-B stress. Silicon treatments also induced an increased in soluble sugar, anthocyanins, and flavonoid content. Leaf silicon concentration increased with the increasing of silicon supply to soil. Positive correlations were found in leaf silicon concentration with total biomass, chlorophyll (a + b), proline, and soluble protein content, respectively. MDA content and the rate of O(2)(-) production were negatively correlated with leaf silicon concentration in seedlings. The results demonstrated that silicon alleviated the damage caused by UV-B on wheat seedlings to some extent by the increase in antioxidant compounds content and leaf silicon concentration.