Concentrations Of 24-epibrassinolide Research Articles

RNAi-Mediated Suppression of OsBBTI5 Promotes Salt Stress Tolerance in Rice.

This study explores the impact of RNAi in terms of selectively inhibiting the expression of the OsBBTI5 gene, with the primary objective of uncovering its involvement in the molecular mechanisms associated with salt tolerance in rice. OsBBTI5, belonging to the Bowman-Birk inhibitor (BBI) family gene, is known for its involvement in plant stress responses. The gene was successfully cloned from rice, exhibiting transcriptional self-activation in yeast. A yeast two-hybrid assay confirmed its specific binding to OsAPX2 (an ascorbate peroxidase gene). Transgenic OsBBTI5-RNAi plants displayed insensitivity to varying concentrations of 24-epibrassinolide in the brassinosteroid sensitivity assay. However, they showed reduced root and plant height at high concentrations (10 and 100 µM) of GA3 immersion. Enzyme activity assays revealed increased peroxidase (POD) and superoxide dismutase (SOD) activities and decreased malondialdehyde (MDA) content under 40-60 mM NaCl. Transcriptomic analysis indicated a significant upregulation of photosynthesis-related genes in transgenic plants under salt stress compared to the wild type. Notably, this study provides novel insights, suggesting that the BBI gene is part of the BR signaling pathway, and that OsBBTI5 potentially enhances stress tolerance in transgenic plants through interaction with the salt stress-related gene OsAPX2.

Brassinosteroids as promoters of seedling growth and antioxidant activity under heavy metal zinc stress in mung bean (Vigna radiata L.).

The escalation of harmful pollutants, including heavy metals, due to industrialization and urbanization has become a global concern. To mitigate the negative impacts of heavy metal stress on germination and early plant development, growth regulators have been employed. This study aimed to evaluate the response of mung bean (Vigna radiata L.) to zinc stress in the presence of brassinosteroids, focusing on seedling growth and antioxidant potential. Mung bean seedlings were treated with three concentrations of 24-epibrassinolide (EBL) (0.1, 0.2, and 0.4 PPM) with or without zinc. Results demonstrated that the application of brassinosteroids, combined with zinc stress, significantly enhanced germination percentage (about 47.06, 63.64, and 120%), speed of germination (about 39.13, 50, and 100%), seedling growth (about 38% in case of treatment combined 0.4 PPM 24-EBL and 1.5 mM ZnSO4) and seedling vigor index (204% in case of treatment combined 0.4 PPM 24-EBL and 1.5 mM ZnSO4) compared to zinc-treated seedlings alone after 24 h. The activities of antioxidative enzymes (catalase, ascorbate peroxidase, polyphenol oxidase, and peroxidase) and total soluble protein content decreased, while lipid peroxidation and proline content exhibited a significant increase (p ≤ 0.05) when compared to the control. However, the negative effects induced by heavy metal stress on these parameters were significantly mitigated by EBL application. Notably, the most effective concentration of EBL in overcoming zinc stress was found to be 0.4 PPM. These findings underscore the potential of exogenously applied brassinosteroids as a valuable tool in phytoremediation projects by ameliorating heavy metal stress.

Foliar-applied 24-epibrassinolide systemically triggers tolerance to magnesium stress in soybean plants: plausible responses focused on root and leaf structures

ABSTRACT The adverse effects caused by inadequate magnesium (Mg) supplies (deficiency or toxicity) cause disorders in root and leaf structures, compromising the uptake and transport of nutrients and gas exchange. However, 24-epibrassinolide (EBR) is a biodegradable and ecologically viable steroid that exhibits benefits on cell division and vascular differentiation. This study aimed to evaluate whether exogenous EBR application can attenuate the deleterious effects linked to inadequate Mg supplies on the anatomical structures of roots and leaves in soybean plants. The experiment followed a completely randomized factorial design with two concentrations of 24-Epibrassinolide (0 and 100 nM EBR, described as - EBR and + EBR, respectively) and three Mg supplies (0.0225, 2.25 and 225 mM Mg, described as low, control and high supplies of Mg). In general, low and high Mg supplies promoted negative changes in the anatomical variables evaluated. In root tissue, pretreatment with 100 nM EBR stimulated the root structures, confirming the systemic action of EBR and benefits related to the differentiation of these structures. Treatment with low Mg + EBR promoted increases in epidermis thickness from the abaxial leaf side (ETAb) and spongy parenchyma thickness (SPT) in 20% and 13%, respectively. High Mg and EBR were increased in ETAb (31%) and SPT (15%) compared with equal treatment without steroids, improving protection and CO2 fixation. Our results indicate that the foliar application of EBR mitigated the deleterious effects linked to inadequate Mg supply in the anatomical structures of the root and leaf, confirming the systemic action of this steroid.

Effects of 24-epibrassinolide on root-knot nematode, Meloidogyne incognita (Kofoid & White, 1919) Chitwood, 1949 (Tylenchida: Meloidogynidae) in tomatoes

In this study conducted in 2020, three concentrations (1, 5 and 10 µM) of 24-epibrassinolide were applied to seedlings of Lycopersicon esculentum Mill. (Solanales: Solanaceae) cv. H2274, which is susceptible to root-knot nematodes, by immersion, spray and irrigation, and its effects against root-knot nematode Meloidogyne incognita (Kofoid & White, 1919) Chitwood, 1949 (Tylenchida: Meloidogynidae) were investigated. One-thousand second stage juveniles of M. incognita , collected from cucumber roots in a greenhouse located in Çardak, Çanakkale were inoculated on the roots of the plants. After eight weeks, stem fresh weight, stem dry weight, root diameter and longest root length values, in addition to the stem length and stem diameter measured at the beginning and end of the experiment, were recorded. 24-Epibrassinolide, applied by an immersion method, gave similar or better results than the control even in the presence of nematodes. Distilled water plus nematode application showed the highest gall index whereas 5 µM 24-epibrassinolide plus nematode application gave the lowest gall index. The lowest number of egg mass was also obtained from the same concentration of 24-epibrassinolide applied by immersion. As a result, 24-epibrassinolide showed a beneficial effect in terms of reducing the damage caused by the nematodes in tomato plants, depending on the concentration and application method.

Influence of 24-Epibrassinolide on Water Exchange of Wheat Varieties Various in Dry Resistance under Osmotic Stress

We studied the effect of presowing treatment with 0.4 μM concentration of 24-epibrassinolide (EB) on water metabolism and leaf growth under osmotic stress simulated by 5% mannitol in two contrasting soft wheat (Triticum aestivum L.) varieties—Omskaya 35 (Om-35, drought-tolerant) and Salavat Yulaev (SYu, less drought-tolerant)—on the fifth and seventh days of germination. It was found that EB processing reduced the water deficit against the background of mannitol, which was more pronounced in the Om-35 variety than in the less tolerant variety SYu. The compensation by the seventh day of the influence of osmotic stress in the Om-35 cultivar was due to a lesser degree of increase in the leaf area, which led to a lower water loss as a result of transpiration, a decrease in the osmotic potential due to a higher accumulation of the osmoprotectant proline, and a decrease in the negative effect on the exosmosis of electrolytes.

24-Epibrassinolide induces protection against nickel excess in soybean plants: anatomical evidences

Nickel (Ni) excess delays plant growth due to damage to root and leaf structures, reducing nutrient uptake, and carbon fixation, respectively. 24-Epibrassinolide (EBR) is a biodegradable plant growth regulator extracted from plant tissues and is highly efficient against oxidative stress. The objective of this research is to determine whether EBR can improve tolerance to toxic metals and the possible mechanism involved by evaluating the root and leaf structures of soybean plants under high Ni concentrations. The experiment was randomized with four treatments, including two Ni concentrations (0 and 200 µM Ni, described as – Ni2+ and + Ni2+, respectively) and two concentrations of 24-epibrassinolide (0 and 100 nM EBR, described as – EBR and + EBR, respectively). Ni2+ excess provoked damage to root and leaf structures, causing anatomical disorders in these tissues. In roots, EBR increased the epidermis (27%), protecting the root against Ni2+ ions. For leaf tissue, significant increases in palisade (11%) and spongy parenchyma (29%) were detected in plants sprayed with EBR and exposed to Ni2+, which were intrinsically related to stomatal density and stomatal functionality. Our results confirm that pretreatment with 100 nM EBR clearly mitigated the anatomical disorders occasioned by excess Ni on the leaf and root structures of soybean plants.

24-epibrassinolide induces protection against waterlogging and alleviates impacts on the root structures, photosynthetic machinery and biomass in soybean

ABSTRACT Plants exhibit several restrictions under waterlogging conditions, including stomatal limitations, negative impacts on gas exchange, lower nutrient uptake and reduced growth. 24-epibrassinolide (EBR) is a polyhydroxylated steroid, with the advantages to be a natural and biodegradable molecule, presenting beneficial roles in metabolic and physiological processes. The aim of this research is to investigate whether EBR can protect soybean plants against damage caused by waterlogging and evaluate the responses associated with the root and leaf anatomy, photosynthetic machinery and biomass. This study used a completely randomized factorial design with two water conditions (control and waterlogging) and three concentrations of 24-epibrassinolide (0, 5 and 10 nM EBR). This steroid stimulated the activities of enzymes linked to the antioxidant system and resulted in minor damage to the chloroplast membranes. EBR maximized the efficiency of photosystem II and improved the gas exchange, which was explained by the higher density and index of the stomata in addition to the increased chlorophyll content and electron transport rate. In root structures, EBR mitigated the impact of waterlogging on vascular cylinder and metaxilem, suggesting maintenance and functions of these structures in plants stressed.

Putrescine metabolism modulates the biphasic effects of brassinosteroids on canola and Arabidopsis salt tolerance

Brassinosteroids (BRs) are known to improve salt tolerance of plants, but not in all situations. Here, we show that a certain concentration of 24-epibrassinolide (EBL), an active BR, can promote the tolerance of canola under high-salt stress, but the same concentration is disadvantageous under low-salt stress. We define this phenomenon as hormonal stress-level-dependent biphasic (SLDB) effects. The SLDB effects of EBL on salt tolerance in canola are closely related to H2 O2 accumulation, which is regulated by polyamine metabolism, especially putrescine (Put) oxidation. The inhibition of EBL on canola under low-salt stress can be ameliorated by repressing Put biosynthesis or diamine oxidase activity to reduce H2 O2 production. Genetic and phenotypic results of bri1-9, bak1, bes1-D, and bzr1-1D mutants and overexpression lines of BRI1 and BAK1 in Arabidopsis indicate that a proper enhancement of BR signaling benefits plants in countering salt stress, whereas excessive enhancement is just as harmful as a deficiency. These results highlight the involvement of crosstalk between BR signaling and Put metabolism in H2 O2 accumulation, which underlies the dual role of BR in plant salt tolerance.

Alleviation of Oxidative Stress Induced by 24-Epibrassinolide in Soybean Plants Exposed to Different Manganese Supplies: UpRegulation of Antioxidant Enzymes and Maintenance of Photosynthetic Pigments

Adverse effects promoted by inadequate manganese (Mn) supply (deficiency or toxicity) causes inefficiency of the antioxidant system and degradation of chlorophylls. However, 24-epibrassinolide (EBR) is a natural steroid that exhibits beneficial effects on antioxidant metabolism, chlorophyll levels and stress indicators. Therefore, this research aims to evaluate whether EBR application via spray can alleviate oxidative stress in soybean plants exposed to different Mn concentrations and to determine possible contributions of the antioxidant enzymes and photosynthetic pigments. Experiment followed a completely randomized factorial design with two concentrations of 24-epibrassinolide (0 and 100 nM EBR, described as − EBR and + EBR, respectively) and three Mn doses (0.25, 25 and 2500 µM Mn, described as low, control and high supply of Mn, respectively). Plants treated with low and high concentrations of Mn + EBR exhibit significant increases in all enzymes evaluated (superoxide dismutase, catalase, ascorbate peroxidase and peroxidase). To superoxide dismutase (SOD), EBR spray promoted increments of 77%, 38% and 76% under low, control and high Mn supplementation, respectively, compared to same treatment in absence of EBR. Clearly intense activity is linked to SOD contributed by dismutation of superoxide into hydrogen peroxide, being subsequently decomposed by other enzymes (catalase, ascorbate peroxidase and peroxidase). Concomitantly, plants with Mn deficiency and toxicity sprayed with 100 nM EBR presented maintenance of chlorophylls and carotenoids due to reduction of superoxide and hydrogen peroxide and consequently reduced chloroplast membrane damages as indicated by malondialdehyde levels and electrolyte leakage.

24-Epibrassinolide mitigates nickel toxicity in young Eucalyptus urophylla S.T. Blake plants: nutritional, physiological, biochemical, anatomical and morphological responses

Our research revealed that 24-epibrassinolide alleviated nickel toxicity in young Eucalyptus urophylla plants, inducing benefits on nutritional, physiological, biochemical, anatomical and morphological responses. Soil contamination by heavy metals may limit the Eucalyptus production. Disturbances caused by nickel (Ni) toxicity interfere with the absorption of other essential nutrients. 24-Epibrassinolide (EBR) is one form of brassinosteroid (BR) that provides benefits for plant metabolism under Ni toxicity. The aim of this study was to determine whether exogenous EBR can improve ionic homeostasis by evaluating nutrient concentrations, anatomical characteristics and chlorophyll fluorescence in young Eucalyptus urophylla plants subjected to Ni toxicity. The experiment was randomized into four treatments, including two Ni concentrations (0 and 600 μM Ni) and two 24-epibrassinolide concentrations (0 and 100 nM EBR). EBR significantly reduced Ni contents. Plants exposed to Ni2+ and sprayed with steroid had increases in the Ca2+/Ni2+ and Mn2+/Ni2+ ratios in the leaves of 38% and 15%, respectively, compared with the same treatment without EBR. The treatment of Ni2+ toxicity + EBR presented an increase of 42% in effective quantum yield of PSII photochemistry, when compared with plants exposed to Ni without EBR. Ni toxicity induced negative effects on stomatal functionality, but EBR application mitigated these effects. Benefits on effective quantum yield of PSII photochemistry after EBR spray can be related to increases in manganese contents. EBR reduced oxidative stress, alleviating the deleterious effects induced by Ni toxicity and inducing positive repercussions on antioxidant enzymes, photosynthetic pigments and biomass.

24-Epibrassinolide Improves Root Anatomy and Antioxidant Enzymes in Soybean Plants Subjected to Zinc Stress

The aim of this research was to determine whether 24-epibrassinolide can mitigate oxidative stress in soybean plants subjected to different zinc levels; to examine this, we evaluated the possible repercussions on anatomical, nutritional, biochemical, physiological and morphological behaviours. The experiment followed a completely randomized factorial design with two concentrations of 24-epibrassinolide (0 and 100 nM EBR, described as - EBR and + EBR, respectively) and three zinc supplies (0.2, 20 and 2000 μM Zn, described as low, control and a high supply of Zn). In general, low and high zinc supplies produced deleterious effects. However, plants exposed to high zinc +100 nM EBR presented increases of 25%, 7%, 9% 29% and 69% for root epidermis, root endodermis, root cortex, vascular cylinder and metaxylem, respectively, when compared to the same treatment without the steroid. The steroid spray alleviated the impact produced by zinc stress on nutritional status, and these results were intrinsically linked to incremental changes in root structure, mainly vascular cylinder and metaxylem. Antioxidant enzymes play crucial roles in the photosynthetic machinery of plants treated with 24-epibrassinolide and stressed by high and low zinc supply, modulating reactive oxygen species scavenging and protecting the chloroplast membranes, with clear positive repercussions on photosystem II efficiency and photosynthetic pigments. The stimulation induced by this steroid on gas exchange can be explained by the favourable conditions detected in stomatal performance and leaf anatomy, thus enhancing the diffusion of carbon dioxide.

Brassinosteroids Confer Tolerance to Salt Stress in Eucalyptus urophylla Plants Enhancing Homeostasis, Antioxidant Metabolism and Leaf Anatomy

The sodium ion (Na+) is potentially toxic to plants because it can cause K+/Na+ imbalances, oxidative stress and negatively affect growth. Brassinosteroids (BRs), including 24-epibrassinolide (EBR), is an organic substance, biodegradable and positively contributes to plant metabolism. The aim of this research was to investigate whether EBR application via the leaves can enhance homeostasis and to examine the impacts of EBR on the anatomical, physiological, biochemical and morphological behaviours of young Eucalyptus urophylla plants exposed to salt stress. The experiment had four treatments: two salt conditions (0 and 250 mM NaCl, described as − Na+ and + Na+, respectively) and two concentrations of 24-epibrassinolide (0 and 50 nM EBR, described as − EBR and + EBR, respectively). The results suggest that EBR mitigated the deleterious effects caused by salt stress in young E. urophylla plants, thereby improving homeostasis related to the K+/Na+ ratio and increasing the nutrient contents of the tissues. Plants exposed to both Na+ and EBR showed increases in photosynthetic pigments and photochemical efficiency. This result may be a result of the antioxidant system, specifically, the significant increases in the CAT (20%) and APX (51%) enzymes, which were comparable to plants receiving equal treatment without Na+. Additionally, this steroid had benefits for gas exchange and growth that were associated with leaf anatomy and were confirmed by increases in stomatal density (23%), palisade parenchyma (14%) and spongy parenchyma (25%). Therefore, our results confirm that the exogenous application of EBR resulted in tolerance to salt stress.

Influence of various concentrations of 24-epibrassinolide on the kinetic parameters during isothermal dehydration of two maize hybrids

24-epibrassinolide (24-EBL) is plant steroid hormone that can regulate several physiological effects in plants, including promotion of cell growth and induction of heat stress tolerance. The purpose of this work is to investigate the influence of various concentrations of 24-EBL on the dehydration mechanism of seedlings of two maize hybrids (ZP434 and ZP704). Control and treated samples were subjected to isothermal conditions for dehydration processes. The effects of carbohydrates and mineral contents on the possible changes in the dehydration mechanism (from kinetics standpoint) were investigated. Comparing control samples to samples treated with 24-EBL, it was found that different dehydration mechanisms exist. The differences arise from the influence of 24-EBL, that causes a significant increase of phosphorus values for ZP704, whilst the reverse was identified for ZP434. It was assumed that the plumule sensitivity to dehydration stress originates from the interaction of water with primary amino groups as cations in polyamines, for lower concentrations of 24-EBL. It was found that the temperature variation (105–130 °C) leads to situations where trehalose does not arrive fast enough to “replace the water”, because its handicap to binds (by hydrogen bonds) to biomolecules instead of water. It was found that 24-EBL cause changes of carbohydrates properties, which are important for the defense mechanism from environmental stresses.

New insights in dehydration stress behavior of two maize hybrids using advanced distributed reactivity model (DRM). Responses to the impact of 24-epibrassinolide.

Proposed distributed reactivity model of dehydration for seedling parts of two various maize hybrids (ZP434, ZP704) was established. Dehydration stresses were induced thermally, which is also accompanied by response of hybrids to heat stress. It was found that an increased value of activation energy counterparts within radicle dehydration of ZP434, with a high concentration of 24-epibrassinolide (24-EBL) at elevated operating temperatures, probably causes activation of diffusion mechanisms in cutin network and may increases likelihood of formation of free volumes, large enough to accommodate diffusing molecule. Many small random effects were detected and can be correlated with micro-disturbing in a space filled with water caused by thermal gradients, increasing capillary phenomena, and which can induce thermo-capillary migration. The influence of seedling content of various sugars and minerals on dehydration was also examined. Estimated distributed reactivity models indicate a dependence of reactivity on structural arrangements, due to present interactions between water molecules and chemical species within the plant.

Impact of Soil Drench and Foliar Spray of 24-Epibrassinolide on the Growth, Yield, and Quality of Field-Grown Moringa oleifera in Southwest China

The effects of soil drench (SD) (0.4 and 0.8 mg plant−1) and foliar spray (FS) (0.02, 0.04, and 0.08 ppm) of 24-epibrassinolide on the growth, yield, and quality of field-grown Moringa oleifera were evaluated. The results showed that all of the SD and FS treatments enhanced the net photosynthetic rate, stomatal conductance, transpiration rate, total chlorophyll content, and nitrate reductase activity in Moringa leaves. Both SD and FS promoted vegetative and reproductive growth of Moringa, but FS at an excessive concentration could suppress reproductive growth. Within a certain concentration range, the effect of FS on the reproductive growth was superior to that of SD, whereas the effect of SD on vegetative growth was better than that of FS. All of the 24-epibrassinolide treatments except for FS 0.08 ppm increased the number of seeds per fruit pod, the yield of fruit pods per tree, and the yield of seeds per tree, but the yield of the plants treated with SD was lower compared with FS. The FS 0.04 ppm treatment significantly increased the contents of oleic acid and eicosenoic acid and reduced the content of stearic acid in the seeds. All of the SD and FS treatments increased crude protein content in the leaf powder and seeds of Moringa as well as vitamin C in the leaves. Our results showed that the optimal concentration of 24-epibrassinolide for FS was 0.04 ppm, and the optimal concentration for SD was inferred to be higher than 0.8 mg plant−1.

Effect of environmental factors on the compounds of the essential oil of Lippia citriodora

Lippia citriodora is a member of the genus Lippia. The species is endemic to South America, while it is cultivated in the world for the lemon-like aroma emitted by its leaves. In the present study the effects of different NaCl as well as 24-epibrassinolide concentrations in the essential oil composition were investigated. In total, eleven treatments were studied. The major essential oil components in control plants were: Geranial (22.52%), Citral (15.88%) Germacrene D (7.42%), Caryophyllene (7.11%), Benzenamine (6.30%), Spathulenol (6.00%) and Curcumene (5.44%). Significant positive/negative correlations occurred between some components with salt concentration. Paired sample tests showed significant differences between major components of an essential oil with salt as well as with 24-epibrassinolide concentrations.

Optimization of the conditions for production of synthetic seeds by encapsulation of axillary buds derived from minituber sprouts in potato (Solanum tuberosum)

Synthetic seed technology is a convenient alternative to conventional multiplication in potato. In this work, we studied and optimized the process of alginate encapsulation of axillary buds derived from potato minituber sprouts (PMSs). We assayed different concentrations of sodium alginate, CaCl2 and matrix culture media, different explant sizes, different concentrations of 24-epibrassinolide (EBr) applied at different stages of the encapsulation process, different planting substrates and different cold storage periods in order to determine the best conditions for encapsulation in cvs. Sante and Agria. The conditions that resulted in the greatest regrowth rates and speed in both cultivars involved the choice of 2–3 mm-long buds, a 2 days pre-culture of buds in culture medium supplemented with 10−6 M EBr, encapsulation in 3 % sodium alginate with 1 % CaCl2 and full-strength MS culture medium, regrowth in solid MS culture medium and then transfer to coco peat (coir fiber pith) for conversion into plantlets. We also found that buds encapsulated under these conditions maintained the initial viability rates for up to 120 days in ‘Sante’ and 90 days in ‘Agria’, although regrowth speed decreased after 60 days in both cultivars. We demonstrate the possibility of producing synthetic seeds efficiently using axillary buds derived from PMSs.

Polyphenolic Profile of Maize Seedlings Treated with 24-Epibrassinolide

High-performance thin-layer chromatography (HPTLC) combined with image analysis and pattern recognition methods were used for fingerprinting of phenolic compounds present in seedlings of two maize genotypes ZP 434 (new generation hybrid, drought tolerant) and ZP 704 (older generation hybrid, drought sensitive) treated with different concentrations of 24-epibrassinolide. This is the first report of TLC chromatographic profile of phenolics’ mixtures in maize seed extracts influenced by brassinosteroid phytohormones. Nine samples of shoot of seedlings for the whole concentration range of phytohormones (5.2 × 10−7–5.2 × 10−15 M), one sample of root of seedlings treated with 5.2 × 10−15M 24-epibrassinolide, and the control samples of nontreated seedlings, for both genotypes, were analyzed. Phenolic profiles of root extracts indicate the absence of more polar compounds such as phenolic acids and glycosides present in shoot of seedlings. Also, hormones applied in higher concentrations have an inhibiting effect on the content of phenolics in ZP 434. Application of chemometric methods enables characterization of particular genotype of maize according to its phenolic profile.

Yield and quality of head lettuce after 24-epibrassinolide application under optimal and reduced irrigation

The aim of this work was evaluation of 24-epibrassinolide influence on yield and quality of head lettuce in optimal and reduced moisture conditions and work out recommendation of 24-brassinosteroids use for lettuce in growers praxis. Field trials were carried out on land belonging to the Demonstration and Research Station of CULS in Prague – Troja in 2009 and 2011. Planting on 27. 8. 2009 and 20. 8. 2011 was done at planting space 0.25 × 0.30 m, each variant in four repetition (single plot 4,5 m2). Seedlings of head lettuce (cultivar Santoro – Rijk Zwaan) were used. Irrigation was carried out by microspraying, and was based on current values of efficient water capacity (EWC); the critical value of the EWC was 80% for optimally irrigated fields (irrigation O), and 50% for variants with reduced levels of irrigation (irrigation S). The total amount of irrigation water during vegetation were as follows: the variant with optimal levels of irrigation (O) had 131 mm in 2009 and 123 mm in 2011; the variant with reduced levels of irrigation (S): 58 mm in 2009 and 63 mm in 2011 Three variants were in both (O and S) conditions: A – no application of 24-epibrassinolide, B – 1 × 24-epibrassinolide application immediately after planting, and C – application of 24-epibrassinolide 2 x (immediately after planting and then after 14 days after 1st application). Concentration of 24-epibrassinolide was 10−6. Following parameters of head lettuce were set after harvesting (10.–12. 10. 2009 and 14.–15. 10. 2011): weight of single heads, marketable heads, marketable yield (in pcs/ha and t/ha) and ascorbic acid and nitrate contents. Influence of 24-epibrassinolide on single lettuce head weight was not significant, decrease of head weight was evident after 24-epibrassinolide application in some variants. Significant increase of marketable heads number and their percentages were noted after 24-epibrassinolide application in optimal moisture conditions – in variant B of 12 261 heads/ha (11.1 %) and in variant C of 16 279 heads/ha (14.7 %) compared with non treated variant A. This trend was not visible in reduced moisture conditions. Increase (nonsignificant) of total marketable yield (in t/ha) was noted after 24-epibrassinolide application. No significant differences were founded among the ascorbic acid contents in each irrigation variant. A higher ascorbic acid content (by approximately 11.9 % in variant C compared with control A) is evident after application of 24-epibrassinolide in the variant with lower levels of irrigation – S. Contrarily, decrease ascorbic acid content is indicated in the optimal levels of irrigation – O (by approximately 16.8 % in variant C compared with control A). The influence of 24-epibrassinolide application on the nitrate content was not significant, but the trend of nitrates decrease in optimal irrigation conditions is evident.

Exogenous application of brassinosteroid offers tolerance to salinity by altering stress responses in rice variety Pusa Basmati-1

Plant steroidal hormones, brassinosteroids, play a pivotal role in variety of plant developmental processes and adaptation to various environmental stresses. The present work investigates the response of various stress markers upon exogenous application of 24-epibrassinolide (EBL) on Pusa Basmati-1, a commercially important rice variety, under salt stress conditions. Rice seeds after treatment with different concentrations of NaCl alone or in combination with different concentrations of 24-epibrassinolide (EBL) were analysed for various growth parameters, protein, proline and malondialdehyde content (MDA) and antioxidant enzymes activities. The seedlings exposed to NaCl exhibited a significant decline in growth parameters and changes in the levels of antioxidant enzymes, however, treatment with EBL showed an improvement in growth, levels of protein and proline content and antioxidant enzymes activity. The enhanced levels of MDA content during salt stress in rice seedlings was decreased with EBL treatment. Further, the treatment with EBL increased the expression of various oxidative stress marker genes, although to different levels. Expression of various brassinosteroids (OsBRI1, OsDWF4) and salt (SalT) responsive genes, revealed the down regulation of OsDWF4 with application of EBL and upregulation of SalT in presence of salt stress thereby confirming the efficacy of the treatments. Interestingly, a significant down regulation of SalT gene was observed on application of EBL along with salt compared to salt treatment alone. On the other hand, the application of EBL alone and in combination with salt has resulted in upregulation of OsBRI1.