Role Of Salicylic Acid Research Articles

The role of salicylic acid in the plant defense mechanism

Pollution and climate change negatively affect plant health. The growing demand for global food production in the agricultural sector is a decisive driving force for the development of new disease control methods that are effective against known pathogens. Plants possess specialized structures, chemicals, and complex defense mechanisms against pathogens. Understanding these defense mechanisms and pathways is critical to developing innovative approaches to protecting crops from disease. Plant stress can be reduced by applying salicylic acid, which is involved in plant signaling. Salicylic acid induces pathogenetic gene expression and the synthesis of protective compounds involved in local and systemic acquired resistance. For this reason, salicylic acid can be used against pathogens, heavy metal stress, and salt stress. The applied salicylic acid enhances photosynthesis, growth, and various morphological, physiological, and biochemical mechanisms in stressed plants. In this article, we look at the use of exogenous salicylic acid for the relief of bacterial, fungal, and viral diseases.

The role of salicylic acid in elicitation for production of secondary metabolites in Cayratia trifolia cell suspension culture

Cayratia trifolia (L.) Domin has been used in Ayurveda traditional medicine due to broad-spectrum medicinal activity to manage various ailments such as fever, rheumatic arthritis, rheumatic fever, anti-inflammatory, and antimitotic activity. In the present study, C. trifolia cell suspension cultures were utilized to establish the effects of salicylic acid on elicitation of the secondary metabolites. The cells treated with 100 μM concentration of salicylic acid elicitor showed an increase in flavanoids, phytosterols, and steroids content, i.e., 1.707±0.021, 2.35±0.020, and 2.547±0.040 mg/g dry weight, respectively.

Influences of mycorrhizal inoculum on Cd and Pb uptake by wheat plant

Influences of mycorrhizal inoculum on Cd and Pb uptake by wheat plant

Efficacy of salicylic acid in modulating physiological andbiochemical mechanisms to improve postharvest longevity in cut spikes of Consolida ajacis (L.) Schur.

Postharvest losses of cut flowers is one of the considerable challenges restricting their efficient marketability. Consequently, such challenges have triggered a constant hunt for developing compatible postharvest treatments to mitigate postharvest losses. Interestingly, recent studies entrench extensive role of salicylic acid (SA) in mitigating postharvest losses in various flower systems. The current investigation focusses on role of SA in augmenting physiological and biochemical responses to mitigate postharvest senescence in cut spikes of Consolida ajacis. The cut spikes of C. ajacis were supplemented with various SA treatments viz, 2 mM, 4 mM, 6 mM. The effects of these treatments were evaluated against control set of spikes placed in distilled water. Our study indicates considerable increment in postharvest longevity of cut spikes, besides an increase in solution uptake, sugar and protein content of tepal tissues.SA augmented antioxidant system via upsurge in phenolic content and antioxidant enzymes viz, superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) to forfend reactive oxygen species (ROS) related oxidative damage. SA profoundly reduced lipoxygenase (LOX) activity to preserve the membrane integrity and thus prevented seepage of solutes from tepal tissues. These results authenticate SA particularly 4 mM concentration as effective postharvest treatment to preserve the postharvest quality of C. ajacis cut spikes.

Biosynthesis and Roles of Salicylic Acid in Balancing Stress Response and Growth in Plants.

Salicylic acid (SA) is an important plant hormone with a critical role in plant defense against pathogen infection. Despite extensive research over the past 30 year or so, SA biosynthesis and its complex roles in plant defense are still not fully understood. Even though earlier biochemical studies suggested that plants synthesize SA from cinnamate produced by phenylalanine ammonia lyase (PAL), genetic analysis has indicated that in Arabidopsis, the bulk of SA is synthesized from isochorismate (IC) produced by IC synthase (ICS). Recent studies have further established the enzymes responsible for the conversion of IC to SA in Arabidopsis. However, it remains unclear whether other plants also rely on the ICS pathway for SA biosynthesis. SA induces defense genes against biotrophic pathogens, but represses genes involved in growth for balancing defense and growth to a great extent through crosstalk with the growth-promoting plant hormone auxin. Important progress has been made recently in understanding how SA attenuates plant growth by regulating the biosynthesis, transport, and signaling of auxin. In this review, we summarize recent progress in the biosynthesis and the broad roles of SA in regulating plant growth during defense responses. Further understanding of SA production and its regulation of both defense and growth will be critical for developing better knowledge to improve the disease resistance and fitness of crops.

Transcriptome analysis of Clavibacter michiganensis subsp. michiganensis-infected tomatoes: a role of salicylic acid in the host response

Bacterial canker of tomato (Solanum lycopersicon) caused by the Gram-positive bacterium Clavibacter michiganensis subsp. michiganensis (Cmm) is an economically important disease. To understand the host defense response to Cmm infection, transcriptome sequences in tomato cotyledons were analyzed by RNA-seq. Overall, 1788 and 540 genes were upregulated and downregulated upon infection, respectively. Gene Ontology enrichment analysis revealed that genes involved in the defense response, phosphorylation, and hormone signaling were over-represented by the infection. Induced expression of defense-associated genes suggested that the tomato response to Cmm showed similarities to common plant disease responses. After infection, many resistance gene analogs (RGAs) were transcriptionally upregulated, including the expressions of some receptor-like kinases (RLKs) involved in pattern-triggered immunity. The expressions of WRKYs, NACs, HSFs, and CBP60s encoding transcription factors (TFs) reported to regulate defense-associated genes were induced after infection with Cmm. Tomato genes orthologous to Arabidopsis EDS1, EDS5/SID1, and PAD4/EDS9, which are causal genes of salicylic acid (SA)-deficient mutants, were upregulated after infection with Cmm. Furthermore, Cmm infection drastically stimulated SA accumulation in tomato cotyledons. Genes involved in the phenylalanine ammonia lyase pathway were upregulated, whereas metabolic enzyme gene expression in the isochorismate synthase pathway remained unchanged. Exogenously applied SA suppressed bacterial growth and induced the expression of WRKYs, suggesting that some Cmm-responsive genes are regulated by SA signaling, and SA signaling activation should improve tomato immunity against Cmm.

Salicylic acid in combination with kinetin or calcium ameliorates heavy metal stress in Phaseolus vulgaris plant

It has been well documented that phytohormones plays a pivotal role in combating ill effects of various abiotic stresses in crop plants. Out of various phytohormones, worldwide researcher has recognized salicylic acid as potent stress alleviator through modulation in plant metabolic processes. Therefore, present study was designed with an aim to dissect out the role of salicylic acid (through seed) mediated amelioration of heavy metal stress in the presence and absence of kinetin or calcium in Phaseolus vulgaris plants. Seeds were soaked in salicylic acid (0.1 mM) either alone or in combination with kinetin (30 ppm) or calcium chloride (40 mM) before sowing and then seedlings were exposed to toxic concentration of nickel (2.5 mM) and lead (0.5 mM). Salicylic acid alone and in combination with kinetin or calcium improved growth traits, photosynthetic pigment, carbohydrate contents, and nitrogenous constituents along with activities of carbonic anhydrase, nitrate reductase, catalase, peroxidase, and superoxide dismutase of Phaseolus vulgaris plants. However, nickel and/or lead showed oxidative damage through increased electrolyte leakage, malondialdehyde and reduced uptake of mineral ions. Moreover, plants raised from seeds soaked in salicylic acid in combination with kinetin or calcium showed enhanced activities of antioxidant enzymes and proline accumulation under nickel and/or lead stress in Phaseolus vulgaris plants. This study revealed the efficiency of pre-sowing seed soaked in salicylic acid either alone or in alternate combination with kinetin and calcium on neutralizing the toxic effect generated from nickel and/or lead in Phaseolus vulgaris plants and could be employed as sustainable agricultural technique in removal of nickel and lead stresses from plants.

Enhancement of yield by application of salicylic acid in two cotton varieties grown in semi-arid tropics of Nizamabad

The research experiments conducted on the role of salicylic acid (SA) sprayed in three concentrations viz., 0.5 mM, 1.0 mM and 3.0 mM on the yield in terms of buds/plant, flowers/plant, number of bolls/plant, boll weight, fibre length, number of seeds/plant, 100 seed weight and cotton seed oil contents of two varieties of cotton (Gossypium herbaceum L.) viz., Bt- cotton and non-Bt plants grown in the semi-arid tropics of Nizamabad was studied. Nizamabad district soil is known for its salinity and the black soil which is largely responsible for the drought and saline stresses which hampers plant growth and metabolism. Application of three concentrations of SA stimulated the yield of both Bt-cotton and non-Bt cotton varieties. The Bt-cotton variety showed better performance over non-Bt varieties. SA at 3.0 mM conc. was found most effective in increasing the yield of both cotton varieties of over 1.0mM SA, 0.5mM SA applications as well as untreated controls. The enhancement of yield in terms of buds/plant, flowers/plant, number of bolls/plant, boll weight, fibre length, number of seeds/plant, 100 seed weight and cotton seed oil contents in both cotton varieties is an indicator that SA mitigated the negative effect of the semi-arid conditions of the soils in Nizamabad district.

Jasmonic acid and salicylic acid play minor roles in stomatal regulation by CO2, abscisic acid, darkness, vapor pressure deficit and ozone

Jasmonic acid (JA) and salicylic acid (SA) regulate stomatal closure, preventing pathogen invasion into plants. However, to what extent abscisic acid (ABA), SA and JA interact, and what the roles of SA and JA are in stomatal responses to environmental cues, remains unclear. Here, by using intact plant gas-exchange measurements in JA and SA single and double mutants, we show that stomatal responsiveness to CO2 , light intensity, ABA, high vapor pressure deficit and ozone either did not or, for some stimuli only, very slightly depended upon JA and SA biosynthesis and signaling mutants, including dde2, sid2, coi1, jai1, myc2 and npr1 alleles. Although the stomata in the mutants studied clearly responded to ABA, CO2 , light and ozone, ABA-triggered stomatal closure in npr1-1 was slightly accelerated compared with the wild type. Stomatal reopening after ozone pulses was quicker in the coi1-16 mutant than in the wild type. In intact Arabidopsis plants, spraying with methyl-JA led to only a modest reduction in stomatal conductance 80min after treatment, whereas ABA and CO2 induced pronounced stomatal closure within minutes. We could not document a reduction of stomatal conductance after spraying with SA. Coronatine-induced stomatal opening was initiated slowly after 1.5-2.0h, and reached a maximum by 3h after spraying intact plants. Our results suggest that ABA, CO2 and light are major regulators of rapid guard cell signaling, whereas JA and SA could play only minor roles in the whole-plant stomatal response to environmental cues in Arabidopsis and Solanum lycopersicum (tomato).

Role of Salicylic Acid and Yeast Extract in Wheat Production Under Saline Soils Conditions

To investigate the effect of foilar application of salicylic rates and yeast extracton yield and quality of wheat, in this respect the two experiments were carried out at the Experimental Farm, Faculty of Agriculture, Saba Basha, Alexandria University, Alexandria Governorate, Egypt, during the two winter seasons of 2019/2020 and 2020/2021. This factorial experiment was laid out in randomized complete block design (RCBD) with three replications in both seasons. The first factor was salicylic acid concentrations (spray water, 150, 300 and 450 ml/l), while the second factor was yeast (water = control, 2, 4 and 6 g/l water) was in both seasons. The obtained results showed that foliar application of salicylic acid (SA) and yeast extract of wheat significantly affected yield and its component, whereas increasing of SA and yeast extract increased yield and yield component characters of wheat in both seasons. The interaction between SA and yeast was significant on all the studied characters, where planting Giza 171 with foliar application of 450 ppm SA/L and 4 and 6 g yeast/L recorded the highest ones in the two seasons under the study conditions.

Modulation of the toxic effects of zinc oxide nanoparticles by exogenous salicylic acid pretreatment in Chenopodium murale L.

Due to many uses of zinc oxide nanoparticles (ZnO NPs) in various industries, the release of these particles in the environment and their effects on living organisms is inevitable. In this study, the role of salicylic acid (SA) pretreatments in modulating the toxicity of ZnO NPs was investigated using a hydroponic system. After pretreatment with different concentrations of SA (0, 25, 75, and 150 μM), Chenopodium murale plants were exposed to ZnO NPs (50 mg L-1). The results showed that exogenous SA increased the length, weight, chlorophyll, proline, starch, and soluble sugars in the plants. Besides, SA pretreatments improved water status in the plants treated with ZnO NPs. In SA-pretreated plants, increased activity of catalase (CAT), guaiacol peroxidase (GPX), and superoxide dismutase (SOD) was associated with a decline in electrolyte leakage (EL %) and membrane peroxidation. Under NPs stress, SA pretreatments increased the content of phenolic compounds by increasing the activity of phenylalanine ammonia-lyase (PAL). Exogenous SA reduced the translocation of larger amounts of Zn to the shoots, with more accumulation in the roots. This result can be used to produce healthy food from plants grown in environments contaminated with nanoparticles. It seems that all concentrations of SA reduced the symptoms of ZnO NPs toxicity in the plant by strengthening the function of the antioxidant system and increasing the content of some metabolites. Findings also suggest that SA pretreatment can compensate for the growth reduction caused by ZnO NPs.

The role of salicylic acid and benzothiadiazole in decreasing phytoplasma titer of sugarcane white leaf disease

The objective of this research was to study the effect of Benzothiadiazole (BTH) and Salicylic acid (SA) on the systemic acquired resistance (SAR) of sugarcane the phytoplasma associated with the sugarcane white leaf (SCWL) disease. The experiment was conducted on plants of the sugarcane variety Khon Kaen 3 (KK3) infected with SCWL phytoplasma using insect vectors. Biochemical changes related to the SAR such as SA and total phenolic compounds were followed according to 4 different timepoints: 7, 14, 21 and 28 days after inoculation. Together, phytoplasma were quantified by RT-qPCR using the secA gene of phytoplasma. According to our results, the spraying of BTH and SA tended to increase the amounts of SA, total phenolic compounds and a lower presence of phytoplasma in the plants in comparison with the inoculated control. Spraying BTH at a concentration of 2.4 mM and SA at a concentration of 2.4 mM exhibited the best efficiency to reduce the concentration of phytoplasma. According to RT-qPCR results, the inoculated plants sprayed with BTH displayed a significantly lower concentration of phytoplasma compared to the inoculated controls. Overall, our results indicated that the spray of BTH and SA could induce an efficient SAR response to the phytoplasma associated with the SCWL disease. We expect these results will give support to the development of new products for controlling white leaf disease in sugarcane.

Role of salicylic acid in heat stress tolerance in tri-genomic Brassica napus L.

Tri-genomic Brassica napus L.wasdeveloped by the cross between Brassica napusand Brassica nigra. The crop is animportant source of vegetable seed oil in Pakistan,after cotton. The low oilseed rape yield is attributed to high temperature in the production zones. Interspecific hybridization using these two speciescan be helpful to produce heat resistant hybrids. On the other hand, it has been found that foliar application of different plant growth regulators can be used to reduce the heat stress in Brassica. The objectiveof this studywas to test the response of three different tri-genomic hybrids to high temperature stressat seedling stage. Seedlings were foliar sprayed with 0.13 mM salicylic acid (SA) prior to exposure tohigh temperatureat two true leaf stage. The plants were harvested after 30 days of sowing for growth and biochemical analysis. Plants ofV38 showed the highest values for all morphological traits and biochemical activities among the threehybrids. In general, plants exposed to the temperature stress exhibited a significant decline in growth, chlorophyll content and enzyme activity.Foliar application of SA significantly improved leaf and root biomass under heat stress.Further, antioxidativeenzyme activities significantly increased in response to SA either compared to control or to plants exposed to temperature stress.It is concluded thatapplication of salicylic acid elevated activity of antioxidative enzymes and was helpful in mitigating the detrimental effects of high temperature inoil seed rape.

Exogenous salicylic acid alleviates the accumulation of pesticides and mitigates pesticide-induced oxidative stress in cucumber plants (Cucumis sativus L.)

Salicylic acid (SA) is an important signal molecule, regulating oxidative stress response in plants. In this study, we evaluated the influences of SA (1 mg L−1, 10 mg L−1 and 50 mg L−1) on the accumulation of clothianidin (CLO), dinotefuran (DFN) and difenoconazole (DFZ) (5 mg L−1) and pesticide-induced (CLO-10 mg L−1, DFN-20 mg L−1, and DFZ-10 mg L−1) oxidative stress in cucumber plants. Exogenous SA at 10 mg L−1 significantly reduced the half-lives of three pesticides in nutrient solution and prevented the accumulation of pesticides in roots and leaves. And the role of SA in reducing residues was related to the major accumulation sites of pesticides. By calculating the root concentration factor (RCF) and translocation factor (TF), we found that SA at 10 mg L−1 reduced the ability of roots to absorb pesticides and enhanced the translocation ability from roots to leaves. Roots exposed to high concentrations of three pesticides could reduce biomass, low chlorophyll content, increase the accumulation of reactive oxygen species (ROS) and proline, promote lipid peroxidation, and alter the activities of a range of antioxidant enzymes, respectively. Exogenous SA at low concentrations (1 mg L−1 and 10 mg L−1) significantly mitigated these negative effects. Hence, application of exogenous SA at 10 mg L−1 could effectively alleviate the accumulation of pesticides and induce stress tolerance in cucumber planting systems.

Physiological responses of plants and mites to salicylic acid improve the efficacy of spirodiclofen for controlling Tetranychus urticae (Acari: Tetranychidae) on greenhouse tomatoes.

Salicylic acid (SA) is a signaling molecule that can induce plant resistance to certain herbivores. Although the role of jasmonic acid in mediating mite-tomato plant interactions has been well studied, the role of salicylic acid has not. This study examined how the application of exogenous SA, via its effects on tomato plant physiology, alters the activity of mite digestive enzymes, mite energy reserves, and mite susceptibility to spirodiclofen. Enzymatic activity-including superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase, polyphenol oxidase, and phenylalanine ammonia-lyase-along with contents of total phenolic, hydrogen peroxide, and total chlorophyll significantly increased in plants 24h after treatment with 2mM of SA. In contrast, catalase activity significantly decreased in treated plants, and malondialdehyde content was unaffected. Mites fed on tomato plants treated with SA had significantly lower glutathione S-transferase, esterase, α-amylase, and aminopeptidase activities than those fed on control plants. Energy reserve analyses demonstrated a significant decrease in contents of lipid, protein, and glycogen in mites fed on SA-treated plants, whereas carbohydrate content significantly increased. The LC50 of spirodiclofen was decreased 1.8-fold for Tetranychus urticae fed on SA-treated tomato plants compared to controls. Treatment of adult mites with 2mM SA on leaf discs did not cause any direct mortality after 24h. Finally, a greenhouse bioassay confirmed that spider mite mortality following exposure to spirodiclofen was significantly higher on SA plants than on control plants. Mortality of mites exposed to half of the recommended rate of spirodiclofen was similar to those exposed to the recommended rate when they were held on treated plants. These results have valuable implications for T. urticae management programs in tomato production.

Involvement of salicylic acid in cold priming-induced freezing tolerance in wheat plants

Freezing is one of the most damaging abiotic stress factors. Cold priming has been shown to enhance freezing tolerance in wheat. However, the underlying mechanisms are unclear. Salicylic acid (SA) is an important signal molecule involved in plant responses to abiotic and biotic stresses. This study aims to investigate the role of SA in cold priming-induced freezing tolerance in wheat plants. The results showed that the expression of gene encoding phenylalanine ammonia-lyase (PAL, a key enzyme involved in SA biosynthesis) and the level of endogenous SA (both free and conjugated) were significantly up-regulated following cold priming treatment. The role of SA in cold priming-induced freezing tolerance was further explored using the donor and inhibitor of endogenous SA. l-α-aminooxy-β-phenylpropionic acid (AOPP, a specific inhibitor of PAL) pretreatment reversed the increment of SA level induced by cold priming treatment, attenuated the positive effects of cold priming on antioxidant capacity (as indicated by the contents of MDA, ASA and GSH, and the activities of APX, GR, DHAR and MDHAR) and cold-responsive genes expression (such as AOX1a, IRI2 and HSP70) under the later freezing stress as well as the freezing tolerance (as indicated by the photochemical activity, electrolyte leakage and biomass). The application of exogenous SA could obviously counteract the negative effects of AOPP. Findings of the present study suggested that the roles of SA in cold priming-induced freezing tolerance in wheat might involve regulation of antioxidant capacity and cold-responsive gene expression.

Phospholipid Signaling Is a Component of the Salicylic Acid Response in Plant Cell Suspension Cultures.

Salicylic acid (SA) is an important signaling molecule involved in plant defense. While many proteins play essential roles in SA signaling, increasing evidence shows that responses to SA appear to involve and require lipid signals. The phospholipid-generated signal transduction involves a family of enzymes that catalyze the hydrolysis or phosphorylation of phospholipids in membranes to generate signaling molecules, which are important in the plant cellular response. In this review, we focus first, the role of SA as a mitigator in biotic/abiotic stress. Later, we describe the experimental evidence supporting the phospholipid–SA connection in plant cells, emphasizing the roles of the secondary lipid messengers (phosphatidylinositol 4,5-bisphosphate (PIP2) and phosphatidic acid (PA)) and related enzymes (phospholipase D (PLD) and phospholipase C (PLC)). By placing these recent finding in context of phospholipids and SA in plant cells, we highlight the role of phospholipids as modulators in the early steps of SA triggered transduction in plant cells.

Direct Binding of Salicylic Acid to Pectobacterium N-Acyl-Homoserine Lactone Synthase.

Salicylic acid (SA) is a hormone that mediates systemic acquired resistance in plants. We demonstrated that SA can interfere with group behavior and virulence of the soft-rot plant pathogen Pectobacterium spp. through quorum sensing (QS) inhibition. QS is a population density-dependent communication system that relies on the signal molecule acyl-homoserine lactone (AHL) to synchronize infection. P. parmentieri mutants, lacking the QS AHL synthase (expI-) or the response regulator (expR-), were used to determine how SA inhibits QS. ExpI was expressed in DH5α, the QS negative strain of Escherichia coli, revealing direct interference of SA with AHL synthesis. Docking simulations showed SA is a potential ExpI ligand. This hypothesis was further confirmed by direct binding of SA to purified ExpI, shown by isothermal titration calorimetry and microscale thermophoresis. Computational alanine scanning was employed to design a mutant ExpI with predicted weaker binding affinity to SA. The mutant was constructed and displayed lower affinity to the ligand in the binding assay, and its physiological inhibition by SA was reduced. Taken together, these data support a likely mode of action and a role for SA as potent inhibitor of AHL synthase and QS.

Salicylic acid regulates photosynthetic electron transfer and stomatal conductance of mung bean (Vigna radiata L.) under salinity stress

Abstract The role of salicylic acid (0, 1 and 1.5 mM) on photosynthetic electron transfer chain of mung-bean plants grown under salt stress (0, 3, 6 and 9 dS/m2) was studied using chlorophyll a fluorescence (ChlF) measurements. Results indicated that accumulation of K+ content decreased but, Na+ content increased with increasing salt stress. SA-treated plants had more K+ and less Na+ content compared with the non-SA treated plants. Application of SA, especially with 1 mM, increased the I–P step of the OJIP transient curve of fluorescence. Salt stress decreased gs, CCI, FV, FM, SM and PIabs in plants. However, the time taken to reach FM (TFM) increased with increasing salt stress. Application of different concentrations of SA significantly improved gs, CCI, FV, SM, and PIabs of plants. Photosynthetic efficiency of plants improved as a result of SA application via decreasing Fo and increasing FV/FM, FV/Fo, SM/TFM and Area under both saline and non-saline conditions. Accumulation of Na+ had negative, but K+ had a positive correlation with gs, CCI and most of the chlorophyll a fluorescence parameters (except, Fo and TFM). A positive correlation was found between gS and CCI with PIabs. This research indicated that low gs under saline condition seems to cause losses in PSII efficiency, but the application of SA with 1 mM concentration is the best treatment for the alleviation of salt stress injuries on PSII activity of mung bean plants.

Digitalized pencil trace modified electrodes for real time evaluation of salicylic acid in detached Arabidopsis thaliana leaves during regeneration

Plants have excellent abilities to regenerate from detached tissues, in which various phytohormones play critical roles. It has been reported that jasmonate and auxin appeared sequentially during direct de novo root regeneration (DNRR) after leave detachment. However, the role of salicylic acid (SA) is still unknown in this procedure although it is another important plant hormone. We have demonstrated the potential of electrochemical sensors for real time screening of SA but the stability still needed to be improved. Herein a digital plotter was used to modify the carbon tape modified electrodes with pencil traces in order to improve the reproducibility. The modified electrodes in paper-based analytical devices were applied to monitor SA during direct DNRR. The drawing routines and the distances between two close traces were optimized. Our results showed that the carbon tape modified electrodes achieved more reproducible responses of SA. Combined with in vivo sampling, the results using our approach demonstrated that amounts of SA in the wild Arabidopsis thaliana leaves during direct DNRR reached highest at around 72 h after detachment and then decreased, implying that the wave of SA contents might follow that of auxin during direct DNRR. The application of the digital plotter offered a cost-effective and more reproducible method for preparation of disposable working electrodes, which might be extended for other biochemical assays.