Exogenous Application Of Hydrogen Peroxide Research Articles

Reactive oxygen species act as the key signaling molecules mediating light-induced anthocyanin biosynthesis in Eucalyptus

Light plays a pivotal role in regulating anthocyanin biosynthesis in plants, and the early light-responsive signals that initiate anthocyanin biosynthesis remain to be elucidated. In this study, we showed that the anthocyanin biosynthesis in Eucalyptus is hypersensitive to increased light intensity. The combined transcriptomic and metabolomic analyses were conducted on Eucalyptus leaves after moderate (ML; 100 μmol m−2 s−1) and high (HL; 300 μmol m−2 s−1) light intensity treatments. The results identified 1940, 1096, 1173, and 2756 differentially expressed genes at 6, 12, 24, and 36 h after HL treatment, respectively. The metabolomic results revealed the primary anthocyanin types, and other differentially accumulated flavonoids and phenylpropane intermediates that were produced in response to HL, which well aligned with the transcriptome results. Moreover, biochemical analysis showed that HL inhibited peroxidase activity and increased the ROS level in Eucalyptus leaves. ROS depletion through co-application of the antioxidants rutin, uric acid, and melatonin significantly reduced, and even abolished, anthocyanin biosynthesis induced by HL treatment. Additionally, exogenous application of hydrogen peroxide efficiently induced anthocyanin biosynthesis within 24 h, even under ML conditions, suggesting that ROS played a major role in activating anthocyanin biosynthesis. A HL-responsive MYB transcription factor EgrMYB113 was identified to play an important role in regulating anthocyanin biosynthesis by targeting multiple anthocyanin biosynthesis genes. Additionally, the results demonstrated that gibberellic acid and sugar signaling contributed to HL-induced anthocyanin biosynthesis. Conclusively, these results suggested that HL triggers multiple signaling pathways to induce anthocyanin biosynthesis, with ROS acting as indispensable mediators in Eucalyptus.

Elevated tolerance of both short-term and continuous drought stress during reproductive stages by exogenous application of hydrogen peroxide on soybean

The global production of soybean, among other drought-susceptible crops, is reportedly affected by drought periods, putting more pressure on food production worldwide. Drought alters plants’ morphology, physiology and biochemistry. As a response to drought, reactive oxygen species (ROS) concentrations are elevated, causing cellular damage. However, lower concentrations of ROS were reported to have an alleviating role through up-regulating various defensive mechanisms on different levels in drought-stressed plants. This experiment was set up in a controlled environment to monitor the effects of exogenous spray of different (0, 1, 5 and 10 mM) concentrations of H2O2 on two soybean genotypes, i.e., Speeda (drought-tolerant), and Coraline (drought-susceptible) under severe drought stress conditions (induced by polyethylene glycol) during flowering stage. Furthermore, each treatment was further divided into two groups, the first group was kept under drought, whereas drought was terminated in the second group at the end of the flowering stage, and the plants were allowed to recover. After 3 days of application, drought stress significantly decreased chlorophyll-a and chlorophyll-b, total carotenoids, stomatal conductance, both optimal and actual photochemical efficiency of PSII (Fv/Fm and Df/Fm, respectively), relative water content, specific leaf area, shoot length and dry weight, and pod number and fresh weight, but significantly increased the leaf concentration of both proline and total soluble sugars, the root length, volume and dry weight of both genotypes. The foliar application of 1 mM and 5 mM H2O2 on Speeda and Coraline, respectively enhanced most of the decreased traits measurably, whereas the 10 mM concentration did not. The group of treatments where drought was maintained after flowering failed to produce pods, regardless of H2O2 application and concentration, and gradually deteriorated and died 16 and 19 days after drought application on Coraline and Speeda, respectively. Overall, Speeda showed better performance under drought conditions. Low concentrations of foliar H2O2 could help the experimented soybean genotypes better overcome the influence of severe drought during even sensitive stages, such as flowering. Furthermore, our findings suggest that chlorophyll fluorescence and the cellular content of proline and soluble sugars in the leaves can provide clear information on the influence of both drought imposition and H2O2 application on soybean plants.

Peróxido de hidrogênio como atenuante do estresse salino em quiabeiro (Abelmoschus esculentus L.)

ABSTRACT: Okra is a vegetable that stands out for its low production cost, high yield, high nutritional and value and socioeconomic importance in income generation, especially in family farming. In this context, the present study evaluated the physiology, production and water use efficiency of okra under irrigation with saline water and exogenous application of hydrogen peroxide. The treatments were distributed in a randomized block design, in a 5 × 3 factorial arrangement, with five levels of electrical conductivity of irrigation water - ECw (0.3; 1.3; 2.3; 3.3 and 4.3 dS m-1) and three concentrations of hydrogen peroxide - H2O2 (0, 25 and 50 μM), with five replicates, totaling 75 plants. Irrigation with ECw above 0.3 dS m-1 negatively affected stomatal conductance, transpiration, number of fruits, total production and water use efficiency of okra cv. Clemson Americano 80. Hydrogen peroxide at concentration of 22 μM mitigated the effects of salt stress on CO2 assimilation rate, number of fruits, average fruit weight and total production of okra cv. Clemson Americano 80. Water use efficiency is favored by H2O2 application at concentration of 12 μM, especially in plants irrigated with ECw of 0.3 dS m-1.

Irrigação com águas salinas e aplicação foliar de H2O2 altera a homeostase iônica do maracujazeiro-azedo

ABSTRACT Qualitative and quantitative scarcity of water sources is a reality in the Brazilian semi-arid region and restricts the expansion of irrigated areas in this region, where high levels of soluble salts are common. Thus, it is extremely important to seek strategies to enable the production of fruit crops such as sour passion fruit. In this context, the objective of this study was to evaluate the levels of NPK, Na+ and Cl- in leaf and stem tissues of sour passion fruit cv. BRS Rubi do Cerrado as a function of irrigation with saline water and exogenous application of hydrogen peroxide. The experiment was carried out in drainage lysimeters under greenhouse conditions in Campina Grande, PB, Brazil. The design was completely randomized in split plots, with five levels of electrical conductivity of water - ECw (0.6, 1.2, 1.8, 2.4 and 3.0 dS m-1) considered plots and four concentrations of hydrogen peroxide – H2O2 (0, 15, 30 and 45 µM) considered subplots, with three repetitions. Sodium content in the leaves decreased when the H2O2 concentration of 45 µM was applied. N/P and N/Na ratios in the leaves of sour passion fruit cv. BRS Rubi do Cerrado decreased with the increase in irrigation water salinity from 2.76 and 2.03 dS m-1, respectively. Chloride content in the leaves of sour passion fruit increased as a function of irrigation water salinity, regardless of H2O2 application.

Cooperative antioxidative defense of the blue-green alga Arthrospira (Spirulina) platensis under oxidative stress imposed by exogenous application of hydrogen peroxide

Hydrogen peroxide (H2O2) is an environmentally-safe algaecide used to control harmful algal blooms and as a disinfectant in various domestic and industrial applications. It is produced naturally in sunny-water or as a by-product during growth, and metabolism of photosynthetic organisms.To assess the impact of H2O2 on Arthrospira platensis, several biochemical components, and antioxidant enzymes were analysed. The growth and biomass of A. platensis were decreased under the effect of H2O2. Whereas, the concentration up to 40 μM H2O2 non-significantly induced (at P < 0.05) the Chl a, C-phycocyanin (C-PC), total phycobiliprotein (PBP), and the radical scavenging activity of A. platensis. The half-maximal effective concentrations (EC50) for H2O2 were 57, 65, and 74 μM H2O2 with regards to the biomass yield, Chl a, and C-PC content, respectively. While, the total soluble protein, and soluble carbohydrates contents were significantly induced. However, the higher concentrations (60 and 80 μM) were lethal to these components, in parallel to the initiation of the lipid peroxidation process. Surprisingly, the carotenoids content was non-significantly increased by H2O2. Despite the relative consistency of catalase (CAT), the activities of superoxide dismutase (SOD) and peroxidase (POD) enzymes were boosted by all of the tested concentrations of H2O2. The relative transcript abundance of selected regulatory genes was also investigated. Except for the highest dose (80 μM), the tested concentrations had almost inhibitory effect on the relative transcripts of heat shock protein (HSP90), glutamate synthase (GOGAT), delta-9 desaturase (desC), iron-superoxide dismutase (FeSOD) and the Rubisco (the large subunit, rbcL) genes. The results demonstrated the importance of the non-enzymatic and enzymatic antioxidants for the cumulative tolerance of A. platensis.

Effect of Hydrogen Peroxide and Soil Amendments on the Physiological Characteristics of Ranunculus Asiaticus in Saline Soils

This study was conducted in a greenhouse at research station (A) of the College of Agricultural Engineering Sciences - University of Baghdad - Jadiriyah during the autumn season of 2020 to study the impact of exogenous application of hydrogen peroxide and soil amendments (zeolite and Disper osmotic regulator) and their interactions in the physiological traits of the Ranunculus asiaticus L. grown in saline soils. The experiment was carried in a split-split block (2*5*3) according to an RCBD randomized complete block design with three replications and an average of 6 plants in the experimental unit The results showed that the growth of Ranunculus asiaticus L in saline soils caused a significant decrease in the leaf content of relative water content (RWC), membrane stability index (MSI), chlorophyll content. While a significant increase in the leaf content of hydrogen peroxide was observed, and the increase in the electrolytic leaching of the plant is an indicator of oxidative stress. The addition of soil amendments to plants grown under salinity stress caused a significant increase in the leaf content relative to water content, membrane stability, decreased electrolytic leaching, and hydrogen peroxide content. Exogenous application of hydrogen peroxide at a concentration (5 mmol l-1) had a positive effect on most of the physiological characteristics. The interaction between soil amendments and hydrogen peroxide contributed to the avoidance of plants from oxidative stress resulting from the high concentration of effective oxygen radicals (ROS) in the cells of plants exposed to salt stress, and stimulating the activity of the enzymatic and non enzymatic defense system in addition to the increase of chlorophyll and physiological characteristics.

Effect the Different Concentrations of Hydrogen Peroxide and Addition Soil Amendments on Growth and Nutrient Balance in Ranunculus Asiaticus L. Grown under Salinity Conditions

An experiment was conducted in a greenhouse at research station (A) / College of Agricultural Engineering Sciences / University of Baghdad to study the impact of exogenous application of hydrogen peroxide and soil amendments (zeolite and Disper osmotic regulator) in the physiological traits of the Ranunculus asiaticus L. grown in saline soils. The experiment included three factors, soil (S) at two kinds (2.17, 5.8 dsm), soil amendments at includes 3 levels of zeolite (0,4,8 gm kg-1 soil), and two levels Disper Osmotic (1,2 gm l-1), hydrogen peroxide application (0,5,10 mmol l-1). results showed saline soils caused a significant decrease in vegetative and flowering growth, and the leaf content of N, P, K. While a significant increase in the leaf content of Na was observed, is an indicator of oxidative stress. The addition of soil amendments (M3) (1 gm l) to plants grown under salinity stress caused a significant increase in the leaf content of N, P, K and plant height, leaf area and all flowering growth characteristics. Exogenous application of hydrogen peroxide at a concentration (5 mmol l-1) had a significant effect on most of the vegetative and flowering growth characteristics.

Comparative physiological responses and transcriptome analysis revealing the metabolic regulatory mechanism of Prunella vulgaris L. induced by exogenous application of hydrogen peroxide

Comparative physiological responses and transcriptome analysis revealing the metabolic regulatory mechanism of Prunella vulgaris L. induced by exogenous application of hydrogen peroxide

ANÁLISE MULTIVARIADA DE GRAVIOLEIRA SOB ESTRESSE SALINO E APLICAÇÃO EXÓGENA DE PERÓXIDO DE HIDROGÊNIO

ABSTRACT The objective of this study was to evaluate, through multivariate data analysis, the effect of exogenous application of hydrogen peroxide on the photosynthetic pigments, gas exchange and growth of soursop seedlings under salt stress. The study was conducted in a greenhouse, at Federal University of Campina Grande - Paraíba. The assay was carried out from May to October 2018. The treatments were distributed in a randomized block design, in a 5 × 5 factorial arrangement, corresponding to five levels of irrigation water electrical conductivity - ECw (0.6-control, 1.2, 1.8, 2.4, and 3.0 dS m-1) and five concentrations of hydrogen peroxide - H2O2 (0, 10, 20, 30, and 40 μM), with two plants per plot and four replicates. Irrigation water salinity from 1.2 dS m-1 negatively affected the biosynthesis of photosynthetic pigments, gas exchange and growth of soursop. Application of hydrogen peroxide at the concentration of 20 μM resulted in attenuation of salt stress effects on the biosynthesis of photosynthetic pigments, gas exchange and growth of soursop. Hydrogen peroxide concentrations above 30 μM intensified the deleterious effect of irrigation water salinity on the photosynthetic pigments, gas exchange and growth of soursop.

GCR1 Positively Regulates UV-B- and Ethylene-Induced Stomatal Closure via Activating GPA1-Dependent ROS and NO Production.

Heterotrimeric G proteins function as key players in guard cell signaling to many stimuli, including ultraviolet B (UV-B) and ethylene, but whether guard cell G protein signaling is activated by the only one potential G protein-coupled receptor, GCR1, is still unclear. Here, we found that gcr1 null mutants showed defects in UV-B- and ethylene-induced stomatal closure and production of reactive oxygen species (ROS) and nitric oxide (NO) in guard cells, but these defects could be rescued by the application of a Gα activator or overexpression of a constitutively active form of Gα subunit GPA1 (cGPA1). Moreover, the exogenous application of hydrogen peroxide (H2O2) or NO triggered stomatal closure in gcr1 mutants and cGPA1 transgenic plants in the absence or presence of UV-B or ethylene, but exogenous ethylene could not rescue the defect of gcr1 mutants in UV-B-induced stomatal closure, and gcr1 mutants did not affect UV-B-induced ethylene production in Arabidopsis leaves. These results indicate that GCR1 positively controls UV-B- and ethylene-induced stomatal closure by activating GPA1-dependent ROS and NO production in guard cells and that ethylene acts upstream of GCR1 to transduce UV-B guard cell signaling, which establishes the existence of a classic paradigm of G protein signaling in guard cell signaling to UV-B and ethylene.

CATIONIC NATURE OF WATER AND HYDROGEN PEROXIDE ON THE FORMATION OF PASSION FRUIT SEEDLINGS1

ABSTRACT This study was carried out with the objective of evaluating the water relations, photosynthetic pigments and growth of passion fruit cv. BRS Rubi do Cerrado, as a function of the cationic nature of irrigation water and exogenous application of hydrogen peroxide. The experiment was carried out under greenhouse conditions in Pombal – PB, Brazil. The experimental design was randomized blocks, in a 6 × 4 factorial scheme, corresponding to six cationic nature of water - CNW (S1 - Control; S2 - Na+; S3 - Ca2+; S4 - Na++Ca2+; S5 - Mg2+ and S6 - Na++Ca2++Mg2+) and four concentrations of hydrogen peroxide - H2O2 (0, 20, 40 and 60 μM), distributed in a randomized block design with four replicates. Plants in the control treatment (S1) were irrigated using water with electrical conductivity (ECw) of 0.3 dS m-1, while those of the other treatments (S2; S3; S4; S5 and S6) were subjected to ECw of 3.0 dS m-1, prepared with different cation(s). Application of 60 μM of H2O2 reduced the percentage of intercellular electrolyte leakage in plants irrigated with water of calcic composition. Salinity of water composed of sodium, sodium+calcium and sodium+calcium+magnesium, and H2O2 concentrations of 40 and 60 μM resulted in lower leaf water potential. The biomass accumulation of passion fruit was more sensitive to the variation of the electrical conductivity of the water. Regardless of the cationic nature, the use of water with electrical conductivity of 3.0 dS m-1 produced passion fruit seedlings with a Dickson quality index higher than 0.2, considered acceptable.

Foliar application of H2O2 as salt stress attenuator in ‘BRS Rubi do Cerrado’ sour passion fruit

Irrigation with saline water causes a reduction in yield, especially in semi-arid regions. Cultivation strategies have been developed to mitigate salt stress on plants, such as the use of hydrogen peroxide. The objective of this study was to evaluate the attenuating effect of hydrogen peroxide on the gas exchange and growth of ‘BRS Rubi do Cerrado’ sour passion fruit cultivated under irrigation with saline water. The design was completely randomized in split-plot plots, with water salinity levels ECw (0.6, 1.2, 1.8, 2.4, and 3.0 dS m-1) considered the plots and the concentrations of hydrogen peroxide H2O2 (0, 15, 30, and 45 μM) considered the subplots, with three replicates. Gas exchange (stomatal conductance, transpiration, CO2 assimilation rate, intercellular CO2 concentration, instantaneous water use efficiency, and instantaneous carboxylation efficiency), and absolute and relative growth rates in stem diameter were evaluated. An increase in irrigation water salinity from 0.6 dS m-1 reduced gas exchange, and exogenous application of hydrogen peroxide did not promote a significant effect on gas exchange. However, foliar application of hydrogen peroxide at 15 μM increased the growth of ‘BRS Rubi do Cerrado’ sour passion fruit.

Exogenous application of hydrogen peroxide in different resistant bean cultivars of Phaseolus vulgaris to Tetranychus urticae (Acari: Tetranychidae)

The enhancement of plant resistance to pest infestation, improving plant growth parameters and productivity is in sustainable agriculture programs. Hydrogen peroxide (H2O2) is among the most effective compounds acts as a messenger molecule involved in acclimatory signaling and triggering tolerance against various biotic and abiotic stresses. In this study, three cultivars of common bean (Phaseolus vulgaris L.), Nebraska, Paulista, and Valentino were treated with H2O2 to evaluate some vegetative parameters, yield and the natural infestations Tetranychus urticae Koch. Leaf area scored the highest size in Valentino cultivar in (742.5 and 722.3 cm2) in response to 1.5 and 1 mM of H2O2 respectively compared to 416.3 cm2 in the control. However, the Paulista cultivar reached the highest size 722.3 cm2 in response to 1.5 mM H2O2 followed by 702.3 cm2 in response to 1 mM H2O2 compared to 401.8 cm2 in the control. Valentino cultivar scored the highest plant heights 81.8 cm in response to 1.5 mM H2O2 followed by 79.2 cm in response to 1 mM H2O2 compared to 43.2 cm in the untreated plants. Valentino cultivar scored the highest number of seeds, pods, and branches compared to the other two cultivars, while Nebraska scored the lowest number of seeds, pods, and branches in response to 1.5 mM hydrogen peroxide compared to control. Nebraska cultivar scored the lowest number of spider mites, T. urticae compared to the other two cultivars in response to 1.5 mM compared to control. An increase in ROS or hydrogen peroxide in the cells in response to exogenous application of hydrogen peroxide could be toxic to the T. urticae and affect its feeding and subsequently mite reproduction. Results from the existing investigation showed that exogenic application of hydrogen peroxide enhanced the resistance of common beans in response to T. urticae feeding.

INDUCED SEED TREATMENT WITH HYDROGEN PEROXIDE (H2O2) PROMOTES PHYSIOLOGICAL, BIOLOGICAL CHANGES AND SALT-TOLERANCE IN WHEAT (TRITICUM AESTIVUM L.)

The present study was undertaken to study the effect of exogenously applied six hydrogen peroxide H2O2 concentrations (0, 20, 40, 60, 80 and 100 µM) as seed primer on two wheat varieties (Khirman and Inqalab) under salt and non-salt water levels (0 and 100 mM NaCl). The oxidizing effects were measured and estimated using the wheat index of different salt and non-salt water levels, as well as H2O2 soaking seed at varying fixations and concentrations. The H2O2 as a seed primer impacted on growth, yield and physiological and biochemical aspects such as moisture content, sodium potassium substance and sodium potassium content under H2O2 and NaCl levels. The results revealed that the exogenous application of hydrogen peroxide was effective in increasing tolerance of wheat under salt stress. The Khirman and Inqalab varieties could be established and cultivated under saline conditions. 60?M treatment of H2O2 is seen with the strongest impacts. Progress has contributed to enhance physiological and biochemical features of stress outflow, which promote growth.

Hydrogen peroxide in the acclimation of yellow passion fruit seedlings to salt stress

ABSTRACT The objective of the present study was to evaluate the effect of exogenous application of hydrogen peroxide on the emergence, growth and gas exchange of yellow passion fruit seedlings subjected to salt stress. The experiment was conducted in pots (Citropote®) under greenhouse conditions, in the municipality of Campina Grande, PB, Brazil. Treatments were distributed in a randomized block design, in a 4 x 4 factorial arrangement, with four levels of electrical conductivity of irrigation water (0.7, 1.4, 2.1 and 2.8 dS m-1) associated with four concentrations of hydrogen peroxide (0, 25, 50 and 75 μM), with four replicates and two plants per plot. Irrigation using water with electrical conductivity above 0.7 dS m-1 negatively affects the emergence and growth of passion fruit. Hydrogen peroxide concentrations between 10 and 30 μM induce the acclimation of passion fruit plants to salt stress, mitigating the deleterious effects of salinity on the relative growth rate in stem diameter and leaf area, stomatal conductance, transpiration, CO2 assimilation rate and instantaneous carboxylation efficiency. Irrigation water salinity combined with hydrogen peroxide concentrations above 30 μM causes reduction in passion fruit growth and physiology.

Physiological changes and growth of soursop plants under irrigation with saline water and H2O2 in post-grafting phase

The low availability of water associated with high salt concentrations in irrigation water has become one of the leading challenges for agricultural production in the semiarid region of Northeastern Brazil. Thus, the study of strategies to enable the use of saline water in agriculture is essential. From this perspective, this study aimed to evaluate alterations in gas exchange, chloroplast pigments, and cell damage in soursop (Anonna muricata L.) irrigated with saline water and under exogenous application of hydrogen peroxide (H2O2) in the post-grafting phase. A study was conducted in Campina Grande, PB, under greenhouse conditions. The treatments were distributed in a randomized block design, in a 4 × 2 factorial arrangement, consisting of four levels of electrical conductivity of water (ECw; 1.6; 2.4; 3.2 and 4.0 dS m-1) and two concentrations of H2O2 (0 and 20 µM) with four replications. Irrigation water salinity from 1.6 dS m-1 caused changes in the stomatal conductance, respiration, and internal CO2 concentration of soursop plants. A 20 µM concentration of H2O2 reduced the effects of salinity on transpiration and CO2 assimilation values, in addition to promoting the biosynthesis of photosynthetic pigments and reducing cell damage in soursop plants, at 150 days after transplantation. The exogenous application of 20 µM H2O2 reduced the deleterious effects of salinity on the stem diameter of both rootstock and scion in soursop plants irrigated with ECw of 1.6 dS m-1. The exogenous application of 20 µM H2O2 was not efficient in mitigating the damage caused by salinity on the stem diameter of the soursop at grafting point.

Induction of tolerance to salt stress in soursop seedlings using hydrogen peroxide

The exogenous use of hydrogen peroxide is an alternative in the acclimatization of plants to salt stress due to the greater activity of antioxidant enzymes. In this perspective, this study aimed to evaluate the gas exchange and the growth of soursop seedlings under salt stress using hydrogen peroxide. The study was conducted under greenhouse conditions. The treatments were distributed in randomized blocks, in a 5 x 2 factorial arrangement, related to five levels of electrical conductivity of the irrigation water - ECw (0.6, 1.2, 1.8, 2.4, and 3.0 dS m-1) and two concentrations of hydrogen peroxide - H2O2 (0 and 20 μM), with four replicates and two plants per plot. The effects of the treatments were evaluated by the variables of gas exchange and growth. The increase in water salinity negatively affected the gas exchange and the growth of the soursop seedlings. The gas exchange and growth variables presented deleterious effects caused by the salinity of the irrigation water, mitigated by the exogenous application of hydrogen peroxide at the concentration of 20 μM. The exogenous use of hydrogen peroxide at the concentration of 20 μM can be used to induce salt tolerance in soursop seedlings.

Gas exchanges and growth of passion fruit under saline water irrigation and H2O2 application

ABSTRACT The study was carried out to evaluate the photosynthetic efficiency and growth of yellow passion fruit, cultivated under different levels of irrigation water salinity and exogenous application of hydrogen peroxide. The experiment was carried out in greenhouse of the Universidade Federal de Campina Grande, PB, Brazil, using drainage lysimeters with capacity for 100 dm3, filled with Entisol of sandy texture. The experimental design was randomized blocks using a 4 x 4 factorial scheme, with three repetitions, corresponding to four water salinity (0.7; 1.4; 2.1 and 2.8 dS m-1) and four concentrations of hydrogen peroxide (0, 20, 40 and 60 µM). The different concentrations of hydrogen peroxide were applied by soaking the seed for a period of 24 h and spraying the leaves on the adaxial and abaxial sides. At 35 days after transplanting, the interaction between water salinity and hydrogen peroxide concentrations did not significantly interfere with plant physiology and growth, except for the number of leaves. The hydrogen peroxide did not cause significant effects on any of the evaluated plant variables. Increasing salinity of irrigation water led to reduction in gas exchanges at 61 and 96 days after transplanting. Water salinity inhibited the CO2 assimilation, transpiration, stomatal conductance, instantaneous carboxylation efficiency and stem diameter of passion fruit plants.

Impact of Hydrogen Peroxide on the Secondary Metabolites, Enzyme Activities and Photosynthetic Pigment Accumulation of Vigna unguiculata L. (Walp)

The effects of exogenous application of hydrogen peroxide on the secondary metabolites, enzyme activities and photosynthetic pigment accumulation of Vigna unguiculata was investigated. The hereby study was carried out under a screen house to minimize extraneous factors. The experiment was laid down in completely randomized design (CRD) with eight replicates. After two weeks of sowing when the seedlings become fully established, the sample pots were divided into two regimes. The first regimes were supplied daily with 500 mL of 0.1 mM of hydrogen peroxide and the second regime was watered daily with tap water. After fifth week of sowing, the leaves of Vigna unguiculata from each regime were randomly selected and harvested. Secondary metabolites, enzyme assay and photosynthetic pigment screening was carried out on the harvested leaves. The impact of hydrogen peroxide on the parameters studied was done using one way analysis of variance. Mean values were separated using Fisher’s LSD at p≤0.05. The results showed that hydrogen peroxide strongly increased the accumulation of secondary metabolites such as flavonoids, glycosides, saponins, carbohydrates and alkaloids. It also induced α-amylase and lipase activities than the control plants and promotes the accumulation and biosynthesis of chlorophylls and carotenoids. In conclusion, hydrogen peroxide could be used as potential molecule to improve some secondary metabolites (flavonoids, glycosides, saponins, carbohydrates and alkaloids), α-amylase and lipase activities and photosynthetic pigments.

Hydrogen peroxide on acclimation of soursop seedlings under irrigation water salinity

The Brazilian Northeast region provides favorable conditions for the exploitation of several crops, but the high salt concentration in irrigation water constitutes a limiting factor for production in most cases. In this context, this study aimed to evaluate the emergence, growth and partition of photoassimilates in soursop seedlings, cv. ‘Morada Nova’, subjected to irrigation with water of increasing salinity levels and to exogenous application of hydrogen peroxide. The study was carried out in plastic bags under greenhouse conditions, using a sandy loam Regolithic Neosol, in the municipality of Campina Grande, PB, Brazil. Treatments were distributed in randomized blocks, in a 5 x 5 factorial arrangement, relative to five levels of irrigation water electrical conductivity - ECw (0.7, 1.4, 2.1, 2.8 and 3.5 dS m-1) and five concentrations of hydrogen peroxide - H2O2 (0, 25, 50, 75 and 100 µM), with four replicates and three plants per plot. Increasing salt concentration compromised all variables analyzed and leaf area was most sensitive. As irrigation water electrical conductivity increased, the deleterious effects of water salinity on the emergence percentage, emergence speed index, stem diameter and leaf area were attenuated by the exogenous application of hydrogen peroxide, with highest efficiency at the concentration of 50 µM. Hydrogen peroxide concentrations above 38 µM inhibited the specific leaf area of soursop, cv. ‘Morada Nova’.