Concentrations Of Methyl Jasmonate Research Articles

Exogenous methyl jasmonate enhanced kenaf (Hibiscus cannabinus) tolerance against lead(Pb) toxicity by improving antioxidant capacity and osmoregulators.

In this study, the effects of exogenous methyl jasmonate (MeJA) on metal uptake and its ability to attenuate metal toxicity in kenaf plants under Pb stress were investigated. The experiment was conducted with five different MeJA concentrations (0, 40, 80, 160, and 320 μM) as a foilar application to kenaf plants exposed to 200 μM Pb stress. The results revealed that pretreatmen of MeJA significantly increased plant dry weight, plant height, and root architecture at all concentrations tested, with the most significant increase at 320 μM. Foliar application of MeJA at 160 μM and 320 μM increased the Pb concentrations in leaves and stems as well as the translocation factor (TF) from root to leaf. However, the bioaccumulation factor in the shoot initially decreased and then increased with increasing MeJA concentration. By increasing enzymatic (SOD, POD, and CAT) and non-enzymatic (AsA and non-protein thiols) antioxidants, MeJA pretreatment decreased lipid peroxidation, O2- and H2O2 accumulation and recovered photosynthetic pigment content under Pb stress. Increased osmolytes (proline, sugar, and starch) and protein content after MeJA pretreatment under Pb stress restore cellular homeostasis and improved kenaf tolerance. Our results suggest that MeJA pretreatment modifies the antioxidant machinery of kenaf and inhibits stress-related processes that cause lipid peroxidation, hence enhancing plant tolerance to Pb stress.

Jasmonate Promotes Ester Aroma Biosynthesis during Nanguo Pears Storage

Volatile organic compounds (VOCs) have been known to confer the flavor of fruits, characterizing the quality of fruits. Nanguo pear (Pyrus ussuriensis Maxim.) is widely popular among consumers due to its excellent ‘fruity’ aroma derived from ester aroma substances. Jasmonate (JAs) plays an indispensable role in the formation of many qualities in fruit. Therefore, the present study aimed to explore the effect of jasmonate on the VOCs in the Nanguo pear fruit during storage. During storage, the fruits were treated with various concentrations of methyl jasmonate (MeJA) and sodium diethyldithiocarbamate (DIECA, a JAs inhibitor), the inhibitors of JAs biosynthesis. Subsequently, the composition and levels of VOCs in the fruits were determined using GC-MS. The results showed that 100 uM MeJA treatment could promote the accumulation of ester aroma compounds in Nanguo pear fruits, while 100 mM DIECA had the opposite effect. Meantime, MeJA treatment significantly promoted peel degreening, soluble solids content (SSC), fruit softening, and ethylene formation. The RT-qPCR results showed that JAs stimulated the expression of PuAAT1 and repressed the expression of PuCXEs, leading to an increased accumulation of ester aroma compounds. Overall, these results provide a reference for further research on the effect of JAs on fruit aroma.

Methyl jasmonate improves resistance in scab-susceptible Red Delicious apple by altering ROS homeostasis and enhancing phenylpropanoid biosynthesis

Apple (Malus domestica) is an economically important rosaceous fruit crop grown at temperate climate zones. Nevertheless, its production is severely affected by scab disease caused by the ascomycetous fungus Venturia inaequalis (VI). Methyl jasmonate (MeJA) is a stress induced plant hormone, shown to induce resistance against wide range of pathogens. The current study investigated the role of MeJA in promoting scab tolerance in susceptible apple varieties through exogenous application of optimized (100 μM) MeJA concentration, followed by VI infection. According to our analysis, applying MeJA exogenously onto leaf surfaces resulted in increased membrane stability and decreased malondialdehyde levels in Red Delicious, suggesting that MeJA is capable of protecting tissues against oxidative damage through its role in restoring membrane stability. In addition, the changes in the levels of key antioxidative enzymes and reactive oxygen species (ROS) showed that exogenous MeJA maintains ROS homeostasis as well. Higher phenylalanine ammonia-lyase activity and increased accumulation of phenylpropanoids in MeJA-treated VI-infected plants indicated the MeJA reprogrammed phenylpropanoid biosynthesis pathway for scab tolerance. Our study of scab tolerance in apples induced by MeJA provides new insights into its physiological and biochemical mechanisms.

Exogenous methyl jasmonate regulates endogenous hormone synthesis of soilless cultivated Chinese chive to promote growth physiology and photosynthesis

Methyl jasmonate (MeJA) is involved in regulating various growth and development processes of plants, yet the underlying mechanisms remain unclear. Therefore, the objective of this study was to investigate the effects of exogenous MeJA on physiological growth, photosynthesis, and endogenous hormones in soilless cultivated Chinese chives. Four concentrations of MeJA (0, 300, 500, and 800 μM) were applied to the leaves of substrate-grown and hydroponics Chinese chives. The results showed that MeJA increased the leaf tissues water content and SPAD values of hydroponically Chinese chives, and 500 μM MeJA significantly enhanced the root activity and leaf carotenoids content of soilless cultivated Chinese chive, and promoted the activities of key enzymes of chlorophyll synthesis (ChlM and POR), thereby increasing chlorophyll a, chlorophyll b and total chlorophyll contents. Meanwhile, MeJA (500 μM) enhanced the activity of key enzymes in the Calvin cycle (Rubisco, FBA, FBPase, GAPDH, and TK), promoted CO2 fixation, improved photosynthetic carbon assimilation efficiency, and promoted Gs, Tr, and Pn, thereby enhancing photosynthesis. Moreover, MeJA (500 μM) significantly enhanced the instantaneous distribution (I-P) of the OJIP curve, enhanced the ability of the plastoquinone pool (PQ) to accept electrons, increased the quantum yield, promoted the apparent quantum flux per unit leaf area and energy flux ratio per unit PSII active reaction center, improved the electron transfer efficiency while reducing the heat dissipation energy flux per unit PSII active reaction center, and thus enhanced PSII activity. Additionally, exogenous MeJA (500 μM) promoted the accumulation of endogenous ZT, GA3, IAA, and ABA, but inhibited the upstream substrates for OPDA synthesis (MGDG and DGDG) in the JA synthesis pathway, and decreased the activities of JA synthases (LOX, AOC, and OPR), which in turn inhibited the synthesis of JA and MeJA. Changes in the relative content of MGDG/DGDG altered the membrane lipid composition of the photosynthetic membrane, which in turn altered the energy balance of the light reaction and improved the efficiency of electron transfer within the photosynthetic membrane, thereby enhancing the photosynthetic capacity. In conclusion, our study demonstrates that exogenous MeJA improves root activity and chlorophyll accumulation in soilless cultured Chinese chives, and adjusting the composition of photosynthetic membrane lipids by regulating the levels of endogenous hormones and JA-synthesizing substrates, promoting the efficiency of electron transfer, enhancing PSII activity, and promoting photosynthetic carbon fixation, thereby enhancing photosynthesis and promoting growth.

Different Effects and Application of Methyl Jasmonate on Triticum aestivum L. by aphid Attack

Wheat (Triticum aestivum L.) widely grown in Pakistan during winter season. Aphid is one of the biological factors that inhibits seed germination and plant development. Methyl jasmonate is a plant growth regulator known to take part in defense responses against different types of stresses including Aphid attack. The current study was conducted to improve the growth of the wheat by the foliar application of Methyl jasmonate. Two wheat varieties (Shafaq and Gold) were be sown in plastic pots filled with 6 kg soil in each pot. After germination, wheat plants were treated with different Aphids. After three weeks of treatment data about survival percentage, root attributes, shoot attributes and nutrient analysis was be recorded using standard procedure. The experiment was be conducted under a complete randomized design (CRD) with three replicates and results was be deducted after statistical analysis. Different concentrations of methyl jasmonate (100 micromolar and 1mM) were applied to 20 days old wheat plant. Rhopalosiphum padi was allowed to infest the methyl jasmonate treated plants as well as non-treated plants. Control plants were covered with net and no concentration of methyl jasmonate were applied. Aphids were allowed to infest the plant for 48 hours, after that the plant from all treatments were sampled for all physiological studies. Methyl jasmonate treated plants as well as control plants were used for direct aphid population count after every week. Concluded results depicted that plants exposed to different concentrations of methyl jasmonate affected the root and shoot length, plant height which was further improved through MeJA supplementation.

Methyl jasmonate reduces cadmium toxicity by enhancing phenol and flavonoid metabolism and activating the antioxidant defense system in pigeon pea (Cajanus cajan)

Cadmium (Cd) is absorbed by plant roots from soil along with essential nutrients and affects plant growth and productivity. Methyl jasmonate (Me-JA) play important roles to mitigate Cd toxicity in plants. We have investigated the role of Me-JA to ameliorate Cd toxicity in Pigeon pea (Cajanus cajan). Plant root growth, biomass, cellular antioxidant defense system and expression of key regulatory genes in molecular and signaling process have been analyzed. Two Cajanus cajan varieties AL-882 and PAU-881 were grown at 25 °C, 16/8h light/dark conditions in three biological replicates at 5 mM Cd concentration, three concentration of Me-JA (0, 10 nM, 100 nM) and two concentrations in combination of Me-JA + Cd (10 nM Me-JA +5 mM Cd, 100 nM Me-JA +5 mM Cd). The seedlings were exposed to Cd stress consequently plants showed decrease in primary root growth (60.71%, in AL-882 and 8.33%, in PAU-881), shoot and root biomass and antioxidant enzymes activities. Me-JA treatment resulted in increased primary root growth (63.64%, in AL-882) and overall plant biomass. Oxidative stress generated due to Cd stress was counter balanced by Me-JA treatment. Me-JA reduced H2O2 free radicals formation and enhanced antioxidant enzyme activities and phenolic content in stressed seedlings. Me-JA treatment increased expression of CALM, IP3, CDPK2, MPKs (involved in calcium and kinase signaling pathways) and reduced expression of metal transporters (IRT1 and HMA3) genes. This reduction in metal transporters gene expression is a probable reason for low toxicity effect of Cd in root after Me-JA treatment which has potential implications in reducing the risk of Cd in the food chain.

Cell culture of Euphorbia fischeriana and enhancement of terpenoid accumulation through MeJA elicitation

Euphorbia fischeriana Steud is a perennial medicinal plant belonging to the Euphorbiaceae family, but its clinical application has been limited due to the scarcity of natural raw materials. Therefore, this study attempted to provide a new method for producing plant materials of E. fischeriana by cell culture. During cell culture, the effects of concentrations of plant growth regulators and sucrose were investigated to improve the culture efficiency. The results showed that the combination of 1.5 mg/L 6-benzylaminopurine and 0.2 mg/L naphthaleneacetic acid, together with a sucrose concentration of 20 g/L in the medium was appropriate for cell growth and terpenoid accumulation. Furthermore, this study applied an elicitation strategy with methyl jasmonate (MeJA) to enhance terpenoid production and investigated the involvement of signaling molecules, such as nitric oxide (NO) and hydrogen peroxide (H2O2). The results indicated that terpenoid accumulation depended on the concentration and treatment duration of MeJA. The maximum total terpenoid content was obtained when the cells were treated with 100 μM MeJA for 4 days. The levels of NO and H2O2 in the cells increased after MeJA treatment and peaked at 8 h and 18 h, respectively, suggesting the involvement of NO and H2O2 in MeJA-induced terpenoid synthesis. The findings of this study demonstrated the potential of cell culture as a method for obtaining plant materials of E. fischeriana.

Preharvest application of MeJA enhancing the quality of postharvest grape berries via regulating terpenes biosynthesis and phenylpropanoid metabolisms

Methyl jasmonate (MeJA) is an important phytohormone that regulates the development of grape, but the effect and underpin mechanism of its preharvest application on secondary metabolites accumulation in postharvest grape berries are still unclear. In this study, the transcriptome profiles combined with metabolic components analysis were used to determine the effect of preharvest MeJA application on the quality formation of postharvest rose-flavor table grape Shine Muscat. The results indicated that preharvest MeJA treatment had no significant effect on TSS content, but had a down-regulation effect on the accumulation of reducing sugar and titratable acid in the berries. The content of chlorophylls and carotenoids in treated berries was significantly higher than that of the control. Many phenolic components, such as trans-ferulic acid, resveratrol, quercetin, and kaempferol, were sensitive to MeJA and their contents were also significantly higher than that of the control under MeJA treatments during the shelf life. Compared with other volatile aroma components, terpenoid components were more sensitive to preharvest MeJA signals, the content of which presented an overall upward trend with increasing MeJA concentration and prolonging storage time. Furthermore, most of the differentially expressed genes in the general phenylpropanoid pathway and terpenoid biosynthesis pathway were up-regulated responding to MeJA signals. The most upregulated regulatory factors, such as VvWRKY72, VvMYB24, and VvWRI1, may be involved in MeJA signal transduction and regulation. Preharvest MeJA may be an effective technique for enhancing the quality of postharvest Shine Muscat grape berries, with its positive effect on enhancing the characteristic aroma and nutritional components.

Nanoparticles doped with methyl jasmonate: Foliar application to Monastrell vines under two watering regimes. An alternative to improve the grape volatile composition?

Elicitors induce defense mechanisms triggering the synthesis of secondary metabolites. Irrigation has implications for a more sustainable viticulture and for grape composition. The aim was to investigate the influence of foliar applications of amorphous calcium phosphate (ACP) nanoparticles and ACP doped with methyl jasmonate (ACP-MeJ), as elicitor, under rainfed and regulated deficit irrigation (RDI) grapevines, on grape aroma composition during 2019 and 2020. In both seasons, nearly all terpenoids, C13 norisoprenoids, benzenoid compounds and alcohols increased with ACP-MeJ under the RDI regimen. In 2019, under the rainfed regime, ACP treatments increased limonene, p-cymene, α-terpineol, TDN, 2-ethyl-1-hexanol, (E,E)-2,4-heptadienal and methyl jasmonate concentration respect to control. In 2020, rainfed regime treated with ACP-MeJ, only increased nonanoic acid content. Grape volatile compounds were most influenced by season and watering status, while the foliar application mainly affected the terpenoids. A RDI regime combined with the elicitor ACP-MeJ application could improve the synthesis of certain important volatile compounds, such as p-cymene, linalool, α-terpineol, geranyl acetone, β-ionone, 2-phenylethanol, benzyl alcohol and nonanoic acid in Monastrell grapes. This article is protected by copyright. All rights reserved.

Transcriptome analysis of Artemisia argyi following methyl jasmonate (MeJA) treatment and the mining of genes related to the stress resistance pathway.

Artemisia argyi Lev. et Vant. (A. argyi) is a perennial grass in the Artemisia family, the plant has a strong aroma. Methyl jasmonate (MeJA) is critical to plant growth and development, stress response, and secondary metabolic processes. The experimental material Artemisia argyi was utilized in this study to investigate the treatment of A. argyi with exogenous MeJA at concentrations of 100 and 200μmol/L for durations of 9 and 24h respectively. Transcriptome sequencing was conducted using the Illumina HiSeq platform to identify stress resistance-related candidate genes. Finally, a total of 102.43Gb of data were obtained and 162,272 unigenes were identified. Differential analysis before and after MeJA treatment resulted in the screening of 20,776 differentially expressed genes. The GO classification revealed that the annotated unigenes were categorized into three distinct groups: cellular component, molecular function, and biological process. Notably, binding, metabolic process, and cellular process emerged as the most prevalent categories among them. The results of KEGG pathway statistical analysis revealed that plant hormone signal transduction, MAPK signaling pathway-plant, and plant-pathogen interaction were significant transduction pathways in A. argyi's response to exogenous MeJA-induced abiotic stress. With the alteration of exogenous MeJA concentration and duration, a significant upregulation was observed in the expression levels of calmodulin CaM4 (ID: EVM0136224) involved in MAPK signaling pathway-plant and auxin response factor ARF (ID: EVM0055178) associated with plant-pathogen interaction. The findings of this study establish a solid theoretical foundation for the future development of highly resistant varieties of A. argyi.

Exogenous methyl jasmonate affects genes involved in monoterpene biosynthetic pathway, phyto-biochemical accumulation, and enzymatic activity of Satureja hortensis L.

Satureja hortensis L. (SH) is a medicinal and aromatic herb utilized markedly in the food, pharmaceutical, and cosmetic industries because of its specific secondary metabolites (SMs), especially monoterpenoids. However, the impact of elicitors on the expression of monoterpene synthase genes in SH remains unexplored. Therefore, the supreme objective of this research was to elucidate the phyto-biochemical and targeted genes expression responses of SH to the exogenous application of methyl jasmonate (MeJA). Accordingly, having chosen four concentrations of MeJA, they sprayed at the five-leaf stage for two weeks, and then leaves were harvested at two exposure times of 24 and 48 hrs for further analysis, using spectrophotometric, real time-quantitative polymerase chain reaction (RT-qPCR), and gas chromatography−mass spectrometric (GC–MS) methods. The results highlight that not only were the highest contents of phenolic, flavonoids, peroxidase, superoxide dismutase, proline, and malondialdehyde in the elicited SHs but also the highest expression of β-farnesene synthase (BFS) and 1-deoxy-D-xylulose 5-phosphate reductase (DXR) genes together with the highest amount of carvacrol were up-regulated in them compared to their respective control. In conclusion, these findings demonstrate the great industrial potential of MeJA in improving the production of phytochemicals in medicinal plants, particularly in SH.

Study on the impact of exogenously applied methyl jasmonate concentrations on Solanum lycopersicum under low temperature stress

BackgroundTo decipher the capability of Methyl Jasmonate (MeJA) in resisting cold stress in Solanum lycopersicum assessment regarding various physiological parameters in response to diverse doses of MeJA was done. Low temperature (LT) were given to the plants with MeJA (J1C, J2C, J3C) or without MeJA (LT) application. MeJA in the form of foliar spray was given before stress, during stress and after stress. Three concentrations of MeJA were used under normal and LT stress conditions that includes of J1 (0.5 µM), J2 (10 µM), and J3 (15 µM).ResultsOxidative stress, growth characteristics, stress tolerance parameters, antioxidant response and photosynthetic parameters were investigated. In our current study we observed that oxidative stress markers declined by MeJA supplementation under cold stress conditions. MeJA boosted antioxidant enzyme activity along with photosynthetic parameters. The best concentration of MeJA was J2 based on results obtained. This is the first study related to MeJA best dose screening in Solanum lycopersicum under LT stress conditions.ConclusionThe LT stress in the Solanum lycopersicum plant was reduced by MeJA. The adverse consequences of LT stress can be significantly attenuated by the J2 concentration of MeJA. So, the optimal concentration of MeJA supplied exogenously to LT stressed Solanum lycopersicum can be a smart strategy to mitigate harmful impact of LT stress on detox system and overall growth of plant.

Methyl jasmonate and iron oxide nanoparticles act as elicitors to stimulate production of bioactive antioxidants and metabolites in the in vitro callus cultures of Bergenia ciliata (haw.) Sternb

In vitro callus cultures of Berginia ciliata were used to evaluate different ratios of iron oxide nanoparticles and methyl jasmonate for elicitation, with the goal of improving callus morphological features and bergenin biosynthesis. Shoot explants were cultured using MS (Murashige and Skoog) media supplemented with three elicitation concentrations of iron oxide nanoparticles (30, 60, and 90 ug/l) and three elicitation concentrations of methyl jasmonate (50, 75, and 100 uM). The results were compared to the control without elicitor treatment. All the elicitation treatments significantly enhanced the phytochemical contents. In vitro callus elicitation with 75 uM MeJ and 90 ug/l iron oxide nanoparticles proved as the best among tested elicitation concentrations. The elicitation improved the water contents and fresh and dry weights of the callus. The callus elicitation with 90 ug/l iron oxide nanoparticles increased the callus moisture contents by 16%. The elicitation treatments affected callus color traits and improved the callus compactness. Callus elicitation increased the activities of bioactive antioxidants such as phenylalanine ammonia-lyase, superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase. The contents of bergenin, a major phytochemical, were found enhanced under elicitor treatments. Furthermore, contents of total phenolics and flavonoids improved upon elicitation. The in vitro callus elicitation resulted in better antioxidant potential for B. ciliata as assessed through the DPPH free radical scavenging protocol. The callus elicitation with 90 ug/l iron oxide nanoparticles increased DPPH scavenging percentage by 68%. In vitro callus elicitation with iron oxide nanoparticles and methyl jasmonate is an effective measure to enhance bergenin contents and bioactive antioxidants in the callus cultures of B. ciliata.

Impact of paclobutrazol on storage root number and yield of sweet potato (Ipomoea batatas L.)

Increasing storage root number is an important way to improve the yield of sweet potato. Here, two-year field experiments were conducted to study the effect of 0 (CK), 10, 20 and 30 mg kg−1 paclobutrazol (PBZ) on the phytohormones and lignin biosynthesis, and root growth and yield of sweet potato. The current study found that PBZ10 decreased the concentration of phytohormones gibberellin 3 (GA3), indole acetic acid (IAA) and abscisic acid (ABA) in the subterranean stem, whereas increased the concentration of zeatin riboside (ZR) and methyl jasmonate (MeJA), resulting in lower root length, volume and tip number at 3 and 5 days after planting (DAP). At 5 DAP, PBZ10 decreased GA3, MeJA and ABA concentration in adventitious root, and increased IAA and ZR concentrations, resulting in increased root length, volume, tip number and surface area at 10 DAP. By 5–30 DAP, PBZ10 decreased the concentration of GA3 and ABA in potential storage roots and increased the concentration of IAA, ZR and MeJA, thus increasing root number. At 10–20 DAP, PBZ10 decreased the lignin concentration in the potential storage root along with the expression of IbEXP1 and the enzymatic activities of phenylalanine ammonialyase, 4-coumaric acid CoA ligase and peroxidase, which are involved in the regulation of lignin biosynthesis, resulting in increased potential storage root diameter; interestingly, the opposite pattern was observed by 25–30 DAP. Then, PBZ10 increased the SR number at 40 DAP, and the yield of sweet potato at harvest time, and no PBZ was detected in SRs of PBZ10. But excessive concentration of PBZ is unfavorable to root development and led to a decrease of yield. These results indicated that a moderate PBZ (10 mg kg−1) application could reasonably regulate phytohormones and lignin biosynthesis, then increase storage root number and yield of sweet potato.

Effect of stress hormones on the metabolome of a suspension culture of the aromatic medicinal plant Cymbopogon schoenanthus subsp. proximus

The current study aimed to evaluate and compare the effect of different concentrations (0.0–200.0 µM) of jasmonic acid (JA), methyl jasmonate (MeJA), and salicylic acid (SA) on suspension culture mass production and untargeted metabolic profiling of the medicinal plant Cymbopogon schoenanthus subsp. proximus. The addition of 50 µM MeJA improved the fresh weight of embryogenic tissue significantly. MeJA and SA did not affect tissue dry weight, whereas JA significantly decreased it. Based on 1H and 1H–13C NMR data and NMR databases, 50 compounds were identified. The addition of stress hormones resulted in the biosynthesis of novel metabolites like theophylline and syringate that were absent in control samples. In addition, significant variations in the concentrations of numerous compounds, including sugars, amino acids, organic acids, phenols, and alkaloids, were observed. The upregulation of trigonelline concentration was observed upon the addition of a higher concentration of MeJA (200 µM), whereas all tested concentrations of SA resulted in its upregulation. Addition of JA and SA causes significant changes in aminoacyl-tRNA biosynthesis pathway and amino acid metabolism pathways, such as alanine-aspartate and glutamate metabolism and arginine and proline metabolism. MeJA had significant impacts on glycolysis and starch-glucose metabolism pathways in addition to amino acids metabolism pathways. The present findings were successful in demonstrating a correlation and distinction between the effects of JA, MeJA, and SA, on the metabolome of Cymbopogon schoenanthus, a valuable medicinal plant. The identified metabolites and their associated pathways would be valuable in future biotechnology applications of the genus Cymbopogon.

Methyl jasmonate, salicylic acid, and oxalic acid affects growth, inducible defenses, and pine weevil resistance in Norway spruce.

The large pine weevil (Hylobius abietis) is a major regeneration pest in commercial forestry. Pesticide application has historically been the preferred control method, but pesticides are now being phased out in several countries for environmental reasons. There is, thus, a need for alternative plant protection strategies. We applied methyl jasmonate (MeJA), salicylic acid (SA) or oxalic acid (OxA) on the stem of 2-year-old Norway spruce (Picea abies) plants to determine effects on inducible defenses and plant growth. Anatomical examination of stem cross-sections 9 weeks after application of 100 mM MeJA revealed massive formation of traumatic resin ducts and greatly reduced sapwood growth. Application of high concentrations of SA or OxA (500 and 200 mM, respectively) induced much weaker physiological responses than 100 mM MeJA. All three treatments reduced plant height growth significantly, but the reduction was larger for MeJA (~55%) than for SA and OxA (34-35%). Lower MeJA concentrations (5-50 mM) induced comparable traumatic resin duct formation as the high MeJA concentration but caused moderate (and non-significant) reductions in plant growth. Two-year-old spruce plants treated with 100 mM MeJA showed reduced mortality after exposure to pine weevils in the field, and this enhanced resistance-effect was statistically significant for three years after treatment.

Changes in Phytohormone and Antioxidant Enzyme Activities during the Healing Process of Different Crabapple Rootstock–Scion Combinations

By measuring the changes in phytohormones and related enzyme activities of Malus ‘Huabiao’ scions and different rootstocks during the healing process of grafting, this study aims to analyze the effects of different rootstocks on the physiological metabolism of the grafting healing site, thereby providing reference for the selection of M. ‘Huabiao’ grafting rootstocks. The live seedlings of 1-0 M. hupehensis, M. robusta and M. baccata were chosen as rootstocks, and M. ‘Huabiao’ scions were grafted with these seedlings in spring by pasting method. The dynamic changes in activities of indole acetic acid, zeatin riboside, methyl jasmonate content and peroxidase, polyphenol oxidase and L-phenylalanine ammonia-lyase at the healing site of grafting were measured, and the effects of different grafting combinations on the phytohormone and related enzyme activities at the grafted site were investigated. It was found that the M. ‘Huabiao’/M. hupehensis and M. ‘Huabiao’/M. robusta grafting combinations had significantly higher survival rate than M. ‘Huabiao’/M. baccata which only had a success rate of 63%. At the beginning of graft healing, the contents of three phytohormones in healing sites of all the three grafting combinations exhibited a significant decrease. However, in the mid and late stages, great differences were shown in phytohormone content. During the grafting healing process, the changes in three enzyme activities in healing sites of the three grafting combinations showed some regularities. In conclusion, M. hupehensis and M. robusta have strong grafting compatibility with M. ‘Huabiao’; thus, they are suitable to be selected as rootstocks for grafting and propagation of M. ‘Huabiao’. In addition, the changes in phytohormone content and enzyme activity in different grafting combinations reflect the strong affinity relationship between rootstock and scion grafting.

Putrescin modulates metabolic and physiological characteristics of Thymus daenensis under drought stress

This experiment was conducted to understand the protective impact of exogenous putrescine (Put) in Thymus daenensis under drought stress. Plants of T. daenensis were subjected to drought stress (15% polyethylene glycol) and Put (0.2 mM). Drought stress lowered growth attributes and photosynthetic pigments in T. daenensis plants. The increase in the content of malondialdehyde (MDA) and hydrogen peroxide (H2O2) as oxidative stress indicators showed that drought stress caused oxidative stress in T. daenensis plants. Drought stress augmented proline content, phenylalanine ammonia-lyase activity, tyrosine ammonia-lyase activity, indole-3-acetic acid content and methyl jasmonate content in T. daenensis plants. Put treatment improved growth and regulated adaptative mechanisms in T. daenensis plants. Decrease in H2O2 and lipid peroxidation (MDA content) by Put displayed that Put helped to alleviate drought-trigged oxidative stress in T. daenensis plants. Put application strengthened the antioxidant system as a resistance response in the drought-treated T. daenensis plants thereby induction in enzymes activities (superoxide dismutase, catalase and peroxidase) and non-enzymatic antioxidants (total phenol and flavonoid). Put treatment increased coumaric acid and resveratrol content in stressed plants. These results propose a multifaceted contribution of Put on adaptative mechanisms in T. daenensis plants under drought stress.

The Impact of Chemical Fertilizer Application on Ascorbic Acid-Glutathione Cycle, Methyl Jasmonate and Nitrosoglutathione Related Substances of Antioxidant Systems in Tobacco

The unreasonable application of chemical fertilizer as abiotic stress can affect the production of reactive oxygen species (ROS) and the synthesis of related substances, thereby affecting the antioxidant systems mediated by Ascorbate-glutathione (AsA-GSH) cycle, Methyl jasmonate (MeJA), S-Nitrosothiols (SNOs) in tobacco plants. Up to now, further research is needed on the impact of chemical fertilizer application on the above antioxidant system in tobacco plants. In this study, the flue-cured tobacco cultivar ‘Yunyan 87’ (Nicotiana tabacum L.) was used as the material. The content of non-enzyme antioxidants and related enzyme activities of AsA-GSH cycle system, the content of MeJA and SNOs in tobacco leaves, as well as tobacco yield were detected, to study the effects of different amount of fertilizer application (T1 = 30 g/plant, T2 = 45 g/plant, T3 = 60 g/plant) on related indicators of antioxidant system. The results indicated that the content of non-enzymatic antioxidants (AsA and GSH) and the activities of related enzymes in the AsA-GSH cycle, including ascorbate peroxidase (APX), glutathione reductase (GR) and monodehydroascorbate reductase (MDHAR) exhibited first increased and then decreased with increasing amount of fertilizer application. Most of the treatments showed significant differences. T3 treatment markedly reduced MeJA content compared to T1 and T2 treatments. With the increase of fertilizer application, the content of SNOs and the activity of S-Nitrosoglutathione reductase (GSNOR) in tobacco leaves exhibited an initial increase, followed by a decrease, and finally increasing trend, with notable differences among most treatments. Tobacco yield markedly decreased in the T1 treatment compared to the T2 and T3 treatments; however, no obvious difference between T2 and T3 treatments. Altogether, the fertilizer application of T1 (30 g/plant) was too low, which was not conducive to the synthesis of antioxidant substances in tobacco leaves. However, the fertilizer application amount of T3 (60 g/plant) was attributed to excessive application, which caused high salt stress on the growth of tobacco plants. This study provides a basic reference for optimizing fertilizer application in tobacco production.

Methyl jasmonate (MeJA) enhances salt tolerance of okra (Abelmoschus esculentus L.) plants by regulating ABA signaling, osmotic adjustment substances, photosynthesis and ROS metabolism

Methyl jasmonate (MeJA), as a plant growth regulator, which is involves in many morphological and physiological processes, plays an important role in defense systems of plants under stress conditions. However, the roles of physiological and biochemical mechanisms of enhancing salt tolerance of okra plants based on application of MeJA is poorly understood. In this study, the application of the investigated 50 μM MeJA significantly improved salt tolerance of okra plants based on the germination rates and culture pot experiment under salt stress. Based on optimal concentration of MeJA inducing salt tolerance of okra plants, application of 5 mM diphenyleneiodonium (NADPH oxidase inhibitor, DPI) and 50 μM MeJA + 5 mM DPI, respectively, significantly increased salt tolerance of okra plants. Assays on the content of component matter indicated the significant increases of JA, ABA, proline, soluble protein, soluble sugar, photosynthetic pigment and relative water, glutathione (GSH) and ascorbic acid (AsA) content and the significant decreases of hydrogen peroxide (H2O2), superoxide radicals (O2−) and malondialdehyde (MDA) content and electrolyte leakage rates were observed in okra plants with 50 μM MeJA under salt stress. The activities of superoxide dismutase (SOD), glutathione peroxidase (GPX), catalase (CAT), glutathione reductase (GR), ascorbate peroxidase (APX) and peroxidase (POD) related to ROS scavenging were also enhanced in okra plants by applied MeJA under salt stress. Furthermore, the marked decreases of H2O2, O2- and MDA content, and the significant increases of CAT, GR and APX activities and GSH and ASA content involved in ASA-GSH cycle were observed in MeJA-okra, DPI-okra and MeJA+DPI-okra plants under salt stress. H2O2 acted a toxic accumulation of ROS rather than as a second messenger for signal transduction in okra plants. These results demonstrate that exogenous MeJA increases the accumulation of JA, ABA and proline, which enhances salt tolerance of okra plants, by regulating osmotic balance and protecting membrane integrity and photosynthesis and activating ROS scavenging system. As a conclusion, treating okra plants with 50 μM MeJA could alleviate the harmful effects of abiotic stresses.