Leaf Antioxidant Enzyme Activities Research Articles

Changes in Secondary Metabolites Content and Antioxidant Enzymes Activity in Leaves of Two Prunus avium L. Genotypes During Various Phenological Phases.

In addition to its fruit, the sweet cherry (Prunus avium L.) has other parts that can be used as a source of compounds with beneficial biological activity. The content of these metabolites is affected by different inner and outer factors, often as a response to plant defense against various stresses. Leaves of two P. avium. genotypes, Kordia and Regina, grafted on the same rootstock, were analyzed from trees grown in orchards in six different phenological phases for two years. The content of several groups of phenolic compounds, lipid peroxidation, antioxidant activity of the extracts, and enzyme activity were observed via colorimetric methods on a UV/Vis spectrophotometer. The obtained data showed that the content of metabolites and other parameters in these two genotypes are dependent on the term of harvest, as well as environmental conditions, mainly temperature, but sunshine duration and rainfall also had a certain effect on the compounds in the leaves of Kordia and Regina. Even though the differences between these genotypes were not always significant, it is important to consider the right time to harvest the leaves of the sweet cherry, as their content could vary as a result of the reaction to various other conditions and could reflect the resistance of the chosen genotype.

Revealing the size effect mechanisms of micro(nano)plastics on nitrogen removal performance of constructed wetland

Micro(nano)plastics (MPs) in aquatic environments can disrupt wastewater treatment, particularly nitrogen removal in constructed wetlands (CWs). However, their broader effects on microbial and plant nitrogen metabolism remain unclear. This study investigated the effects of different-sized MPs (4 mm, 100 µm, and 100 nm) on nitrogen transformation in CWs. Results revealed that 4 mm- and 100 µm-MPs did not significantly affect total nitrogen (TN) removal, although 100 µm-MPs significantly increased leaf antioxidant enzyme activities and reduced plant uptake of nitrogen by 12.95 % (p < 0.05). In contrast, 100 nm-MPs decreased the TN removal efficiency by 7.97 % via inhibiting both nitrification and denitrification, since 100 nm-MPs penetrated cell membranes, disrupted reactive oxygen species balance, and reduced bacterial viability, thus suppressing microbial nitrogen degradation by 8.07 % (p < 0.05). Additionally, 100 nm-MPs significantly inhibited plant growth and reduced plant nitrogen uptake by 16.05 % (p < 0.05). Furthermore, 100 µm-MPs increased the abundance of nitrifiers but reduced denitrifiers and functional genes, whereas 100 nm-MPs reduced the abundance of both nitrifiers and denitrifiers along with their functional genes (p < 0.05). These findings highlight the need to improve waste management to mitigate the adverse effects of MPs on nitrogen removal.

Effects of nutritional stress on soil fertility and antioxidant enzymes of rice in different growth periods.

Stress in plants denotes the detrimental impact of alterations in external environmental conditions on regular plant growth and development. Plants employ diverse mechanisms to mitigate or evade nutritional stress-induced damage. In order to investigate the physiological response mechanism of plants to nutritional stress and assess its impact on soil nutrient content and antioxidant enzyme activity in rice, a field experiment was conducted applying five treatments: control, nitrogen (N) deficiency, phosphorus (P) deficiency, potassium (K) deficiency, and full fertilization. Rice leaf and soil samples were concurrently gathered during both the vegetative and reproductive growth stages of rice. Analysis was conducted on soil N, P, and K levels, as well as leaf antioxidant enzyme activities, to investigate the impact of nutrient stress on rice antioxidant enzymes and soil fertility. The research findings indicate that full fertilization treatment enhanced the agronomic properties of the soil compared to the control treatment. In the N-deficiency treatment, reactive oxygen species (ROS) levels increased by 16.53-33.89% during the reproductive growth period compared to the vegetative growth period. The peroxidase (POD) activity decreased by 41.39% and superoxide dismutase (SOD) activity increased by 36.22% under K-deficiency treatment during the reproductive growth period compared to the vegetative growth period. Consequently, applying N and P fertilizer during the vegetative growth period can decrease membrane lipid peroxidation levels by 7.34-72.53%. The full fertilization treatment markedly enhanced rice yield compared to other treatments and increased the Nitrogen activation coefficient (NAC) and Phosphorus activation coefficient (PAC) in the soil, while decreasing the PAC. Elevating NAC levels can stimulate the activity or content of PRO, MDA, and RPS during the vegetative growth stage, whereas in the reproductive growth stage, it will decrease the content of ROS, PRO, and MDA. This data offers valuable insights and theoretical support for nutritional stress research.

Mycorrhization of three cultivars of Colocasia esculenta L. Schott and evaluation of their resistance to mildew caused by Phytophthora colocasiae

The objective of this work was to evaluate the effect of arbuscular mycorrhizal fungi on the development of taro leaf blight during the interaction of Colocasia esculenta - Phytophthora colocasiae. Three cultivars of C. esculenta were used with local names, Ekwanfre, Macoumba, and Banlah. The experimental device was a complete randomized block with two repetitions. Four treatments were applied (Control, Mycorrhizal, Infected, and Mycorrhizal+infected). After one month of growth, an artificial infection was carried out with a solution of spores of P. colocasiae of 5x104 sporangia/ml. Disease severity was assessed every 5 days for 20 days. On D20, cytological analysis, mycorrhizal status, metabolite content, and leaf antioxidant enzyme activity were determined. The results showed that the incidence of the disease is 100% from D10 for the treatment infected with the Macoumba cultivar. Mycorrhization inhibited the action of the pathogen. The incidence and severity of the disease are low and less than 50%, in the Mycorrhizal+infected treatment plants compared to the Infected treatment. Cytological analysis revealed fungal, and mycorrhizal structures in the leaves and roots. The maximum frequency and intensity of mycorrhization were 73.33±02.51 and 12.83±04.75% in the mycorrhizal plants of the Macoumba treatment. The total chlorophyll content is less than 1 mg.g-1 of WF, in the three cultivars in infection condition. The contents of total soluble proteins, amino acids, and proline are higher in the plants of the infected treatment compared to mycorrhizal and Mycorrhizal+infected. The H2O2 produced was scavenged by APX and G-POD compared to CAT. These results make it possible to note that the AMFs used contribute to the protection of the C. esculenta plants against the harmful effects linked to the presence of P. colocasiae

Thermotolerance of tomato plants grafted onto wild relative rootstocks.

Heat stress is a major environmental constraint limiting tomato production. Tomato wild relatives Solanum pennellii and S. peruvianum are known for their drought tolerance but their heat stress responses have been less investigated, especially when used as rootstocks for grafting. This study aimed to evaluate the physiological and biochemical heat stress responses of tomato seedlings grafted onto a commercial 'Maxifort' and wild relative S. pennellii and S. peruvianum rootstocks. 'Celebrity' and 'Arkansas Traveler' tomato scion cultivars, previously characterized as heat-tolerant and heat-sensitive, respectively, were grafted onto the rootstocks or self-grafted as controls. Grafted seedlings were transplanted into 10-cm pots and placed in growth chambers set at high (38/30°C, day/night) and optimal (26/19°C) temperatures for 21 days during the vegetative stage. Under heat stress, S. peruvianum-grafted tomato seedlings had an increased leaf proline content and total non-enzymatic antioxidant capacity in both leaves and roots. Additionally, S. peruvianum-grafted plants showed more heat-tolerant responses, evidenced by their increase in multiple leaf antioxidant enzyme activities (superoxide dismutase, catalase and peroxidase) compared to self-grafted and 'Maxifort'-grafted plants. S. pennellii-grafted plants had similar or higher activities in all antioxidant enzymes than other treatments at optimal temperature conditions but significantly lower activities under heat stress conditions, an indication of heat sensitivity. Both S. pennellii and S. peruvianum-grafted plants had higher leaf chlorophyll content, chlorophyll fluorescence and net photosynthetic rate under heat stress, while their plant growth was significantly lower than self-grafted and 'Maxifort'-grafted plants possibly from graft incompatibility. Root abscisic acid (ABA) contents were higher in 'Maxifort' and S. peruvianum rootstocks, but no ABA-induced antioxidant activities were detected in either leaves or roots. In conclusion, the wild relative rootstock S. peruvianum was effective in enhancing the thermotolerance of scion tomato seedlings, showing potential as a breeding material for the introgression of heat-tolerant traits in interspecific tomato rootstocks.

Correction notice: Measurements of Proline and Malondialdehyde Contents and Antioxidant Enzyme Activities in Leaves of Drought Stressed Cotton.

Correction notice: Measurements of Proline and Malondialdehyde Contents and Antioxidant Enzyme Activities in Leaves of Drought Stressed Cotton.

Foliar Application of Melatonin Improves the Salt Tolerance, Ion and Redox Homeostasis and Seed Oil Fatty Acid Profile in Camelina sativa.

Salinity affects the yield and quality of oilseed crops. The effects of a single foliar application of solutions with different concentrations (0, 30, 60 or 90 µM) of melatonin (MEL) to camelina (Camelina sativa) plants grown in soil in a greenhouse and irrigated at four salinity levels (0.5, 4, 8 and 16 dS m-1) were assessed. Increasing salinity decreased leaf chlorophyll and photosynthetic rates, decreased K concentrations and increased Na concentrations in roots and shoots, and increased oxidative marker levels and the activity of protective antioxidant enzymes in leaves. Under severe salinity stress, the MEL90 treatment resulted in increases in chlorophyll, gas exchange attributes, leaf antioxidant enzyme activities, and decreases in leaf oxidative markers and Na. Salinity decreased seed yield, with no seeds being produced at salinities above 8 dS m-1. The MEL90 treatment resulted in increases in seed yield and poly- and mono-unsaturated fatty acid contents and decreases in saturated fatty acid contents. The MEL90 treatment was more effective in alleviating salinity effects than those including lower MEL concentrations. The highest concentrations of K and K/Na ratios were observed with the MEL90 treatment under non-stressed conditions. Data suggest that MEL foliar applications could increase salinity stress tolerance in camelina.

Physio-biochemical responses of grafted tomatoes differing in thermotolerance to heat stress and recovery

The aim of this study was to evaluate the physiological and biochemical heat responses of grafted tomato (Solanum lycopersicum L.) seedlings and their changes during the post-stress recovery period. Heat-tolerant ‘Celebrity’ and heat-sensitive ‘Arkansas Traveler’ tomatoes were grafted onto a commercial ‘Maxifort’ rootstock, and transplants were grown in growth chambers for 14 days of heat treatment (38/30 °C, day/night) followed by 7 days of recovery (25/18 °C). Results showed significant differences between ‘Maxifort’-grafted and ungrafted seedlings in antioxidant enzyme activities with increased leaf ascorbate peroxidase (APX), root superoxide dismutase (SOD) and catalase (CAT), and decreased root guaiacol peroxidase (POD) in ‘Maxifort’-grafted plants when heat stress was imposed. ‘Maxifort’-grafted plants had lower chlorophyll:carotenoid ratios and higher leaf total soluble protein than ungrafted controls under heat stress. Heat stress increased leaf chlorophyll, carotenoid, electrolyte leakage (EL), malondialdehyde (MDA) and leaf and root proline content, and reduced leaf chlorophyll fluorescence (Fv/Fm) during the stress period. Antioxidant enzymes were up-regulated by heat stress in leaves, while those in roots were selectively regulated with increased glutathione reductase (GR) and CAT, and decreased POD and APX activities in heat stressed plants. After the recovery period, chlorophyll, carotenoid, EL and proline contents showed partial or full recovery from the stress, whereas the heat responses of MDA and Fv/Fm remained constant. Cultivar effects were detected in leaf antioxidant enzyme activities of heat stressed plants after recovery as ‘Arkansas Traveler’ had higher POD, GR, CAT and lower SOD activities than ‘Celebrity’. These results demonstrate the potential for using ‘Maxifort’ rootstocks to enhance the thermotolerance of tomato plants during the vegetative stage, although the beneficial traits did not lead to a significant alleviation of heat stress.

Screening of Key Indices and the Gene Transcriptional Regulation Analysis Related to Salt Tolerance in Salix matsudana Seedlings

Pot experiments were performed to comparatively study the differences in 16 salt tolerance indices between the seedlings of six Salix matsudana clones under the stress of various concentrations of NaCl (0, 0.1%, 0.3%, 0.5%, and 0.7%), including the salt injury index, shoot fresh weight, root fresh weight, leaf water content, relative conductivity, malondialdehyde content, and antioxidant enzyme activity. The salt-tolerant clones and key indices of salt tolerance were selected. Transcriptome sequencing analysis was performed on the selected salt-tolerant and salt-sensitive clones under salt stress, and the links between the physiological indices of salt tolerance and gene expression were analyzed. Results: (1) Superoxide dismutase (SOD), peroxidase (POD), chlorophyll, and net photosynthetic rate were closely related to the salt tolerance of Salix matsudana at the seedling stage. The regression equation was constructed as follows: salt tolerance index (y) = 0.224x10 + 0.216x11 + 0.127x12 + 0.191x7 − 0.187 (x10 = chlorophyll, x11 = SOD, x12 = POD, x7 = net photosynthetic rate). (2) The number of differentially expressed genes between the seedlings of salt-tolerant and salt-sensitive clones varied with the time of exposure (0 h, 4 h, 12 h, and 24 h) to 200 mmol·L−1 NaCl stress. The most differentially expressed genes in Sm172 were detected upon 24 h vs. 4 h of salt treatment, while the most in Sm6 were in the 24 h vs. 0 h comparison. Gene Ontology analysis and Kyoto Encyclopedia of Genes and Genomes analysis showed that several differentially expressed genes were involved in carotenoid biosynthesis and plant mitogen-activated protein kinase signaling pathways. The nine highly expressed transcription factor genes (Sm172-f2p30-2392, Sm172-f2p28-2386, Sm6-f8p60-2372, Sm6-f2p39-2263, Sm6-f16p60-2374, Sm6-f3p60-931, Sm6-f2p60-1067, Sm172-f3p54-1980, and Sm172-f3p54-1980) were closely correlated with the four key indices of salt tolerance. These genes could become genetic resources for salt tolerance breeding of Salix matsudana.

Combined effects of green manure and zinc oxide nanoparticles on cadmium uptake by wheat (Triticum aestivum L.)

Cadmium (Cd) toxicity in agricultural soils is serious concern these days which needs continuous attention. Little is known about the combined use of berseem and/or maize residues soil applied as a green manure alone or along with foliar dressing of zinc oxide nanoparticles (ZnONPs) on Cd accumulation in wheat (Triticum aestivum L.). A pot experiment under ambient conditions with wheat grown in Cd-contaminated soil was performed after soil applied different green manure amendments and foliar dressing of ZnONPs was done during plant growth and plants were harvested at full maturity. Compared with control, plant growth attributes and biomass of above ground parts substantially increased with applied amendments being maximum with combined use of ZnONPs + B75 (berseem residue, 75 mg/kg) followed by ZnONPs + M75 (maize residue, 75 mg/kg). All the treatments improved the leaf chlorophyll contents and improved the leaf antioxidant enzyme activities thereby reduced the leaf electrolyte leakage. The Cd accumulation in roots and aboveground parts of the wheat was reduced especially in ZnONPs + B75 followed by ZnONPs + M75. The higher rate of soil applied amendments along with NPs minimized the available Cd in soil extracts but soil post-harvest pH was not much affected by the applied amendments. In conclusion, incorporation of berseem and maize residues as a green manure applied in Cd-contaminated soil combined with foliar NPs may decrease Cd phytoavailability and its accumulation in wheat grains. However, substantial field studies are required under various environmental conditions before final recommendations at field levels.

Growth, phytochemical parameters and glycyrrhizin production in licorice (Glycyrrhiza glabra L.) grown in the field with saline water irrigation

Salinity is a worldwide problem in crops that can be managed using salt-tolerant species. Wild licorice (Glycyrrhiza spp.), a genus of the Fabaceae family that is considered medicinal and contains many secondary metabolites, including the triterpenoid glycyrrhizin, can grow in saline conditions. The effects of irrigating five different field-grown genotypes of Glycyrrhiza glabra with two levels of salinity (75/37.5/37.5 and 150/75/75 mM NaCl/CaCl2/MgSO4) have been studied, looking at some plant physiological and biochemical characteristics. Salinity led to decreases in leaf and root biomass and leaf relative water content, increases in leaf antioxidant enzyme activities (peroxidase, superoxide dismutase and polyphenol oxidase), and increases in osmolyte levels (soluble sugars, glycine betaine and proline) in leaves and roots. Salinity caused decreases in root glycyrrhizin concentrations in three of the genotypes and in glycyrrhizin contents in all of them (decreases ranging from 26% to 73% with intense salinity), likely as a result of the large decreases in root biomass. The glycyrrhizin content was only moderately affected by salinity in one of the genotypes (‘Kerman’). In this salinity-tolerant genotype, the expression of some glycyrrhizin biosynthesis genes (bAS, SQS1, SQS2, CYP72A154, CYP88D6 and UGT73) was increased by salinity, but this did not result in increases in glycyrrhizin contents. These results indicate that the genetic background of licorice affects glycyrrhizin contents and its response to salinity stress, and also that one of the genotypes studied can be used by farmers in soils affected by salinity.

Responses of photosynthesis and antioxidants to simulated acid rain in mulberry seedlings

Acid rain, which has negative impacts on the vegetation of ecological systems, is widespread in Northern and Southern China. However, relatively little is known about the effects of acid rain on the growth and yield of economically important tree species in China. To address this issue, we studied the responses of mulberry seedlings to simulated acid rain (SAR) at different pH values. At pH 4.5, SAR induced increased antioxidant activities, total antioxidant capacity, and the accumulation of reactive oxygen species (OFR) relative to controls. However, the growth of the seedlings under SAR treatments at pH 4.5 and pH 5.6 was greater than controls. No significant differences in photosynthesis and chlorophyll a fluorescence quenching parameters were observed between the SAR treatments at pH 4.5 and pH 5.6 and controls. However, the SAR treatment at pH 3.5 resulted in altered leaf surface characteristics and changes to chloroplast ultrastructure, together with an increase in membrane electrical conductivity and an accumulation of OFR and malondialdehyde. In contrast, leaf antioxidant enzyme activities were decreased, together with electron transport parameters and photosynthesis. Taken together, these results show that the effects of acid rain on the growth and leaf physiology of mulberry seedling are dependent on pH. Moreover, mulberry seedlings had a high tolerance to acid rain at pH 4.5.

Hormopriming instigates defense mechanisms in Thyme (Thymus vulgaris L.) seeds under cadmium stress

Seed germination and root development are vital phases of the plant growth process; however, these steps are strongly influenced by the seed characteristics and environmental conditions. Seed priming provides a condition for uniform and rapid germination and plant establishment. Limited studies are available on the effect of seed priming to ameliorate cadmium (Cd) stress in thyme plants. Hence, the effect of seed hormopriming (salicylic acid and jasmonic acid, 100 mg.l−1) was evaluated. Hydropriming was done using double distilled water. Seed priming significantly increased the seed germination percentage (GP) and germination rate (GR) at all stress levels of Cd contamination. SA-primed seed showed the greatest increase in GP and GR at 30 mg.l−1 Cd by 26 and 37 %, respectively, compared with the control. Salicylic acid (SA) increased plumule and radicle length 29 and 43 %, respectively, at 30 mg.l−1 of Cd concentration compared with the control seeds. SA pretreatment increased plumule dry weight more than radicle dry weight. The leaf antioxidant enzyme activity was increased with increasing Cd concentration. Seed priming with SA increased superoxide dismutase (SOD) and peroxidase (POX) activity by 14 and 15 %, respectively. Leaf malondialdehyde (MDA) content was increased 15 % at 30 mg.l−1 Cd concentration compared with the control plants, but SA priming reduced leaf MDA content 18 % compared with the control seeds. The greatest leaf proline content was observed at 30 mg.l−1 Cd concentration and SA priming. Regardless of the priming treatment, the greatest leaf protein content was observed at 10 mg.l−1 Cd concentration compared with the control. Seed priming with SA diminished the adverse effects of Cd on germination process via enhancing the antioxidant activities and accumulation of osmolytes. Therefore, hormopriming of thyme seeds by SA can enhance the resistance of this valuable medicinal herb to cadmium stress.

The developmental and metabolic effects of different magnesium dozes in pepper plants under salt stress

Morphological and biochemical effects of different magnesium (Mg) doses on pepper plants under salt stress were investigated in this study. Experiments were conducted under controlled conditions of a climate cabin at 25 oC temperature, 70% relative humidity and 16/8 hours light/dark photoperiod. The developmental and metabolic effects of different magnesium doses in plants under salt stress were investigated by examining leaf antioxidant enzyme activities, Malondialdehyde (MDA) levels and chlorophyll contents. Seedlings of ‘Demre’ pepper cultivar (Capsicum annuum L. cv. ‘Demre’) were grown in Hoagland nutrient solution supplemented with 100 mM NaCl to generate salt stress. Besides salt treatments, different Mg doses (Mg 1 = 24.64 ppm, Mg 2 = 49.28 ppm, Mg 3 = 73.92 ppm, Mg 4 = 98.56 ppm, Mg 5 = 123.20 ppm) were applied to plants. On the 20th day of salt treatments, the total weight of the plants which is one of the growths and development parameters of pepper plants was measured, and plant samples were taken for analyses. A slight increase was observed in total weights of salt-treated plants with increasing Mg doses. The greatest plant weight was obtained from Mg 4 + salt treatments. It was observed that increasing Mg doses had positive effects on the development of plants under salt stress. Chlorophyll contents and antioxidant enzymes activities increased and MDA (malondialdehyde) levels, the product of lipid peroxidation, which indicates the amount of damage to plant cells, decreased with increasing Mg doses. Present measurements and analyses and resultant findings revealed that Mg treatments at increasing doses partially alleviated negative effects of salt stress on pepper seedlings.

Evaluation of glycyrrhizin contents in licorice (Glycyrrhiza glabra L.) under drought and soil salinity conditions using nutrient concentrations and biochemical traits as biomarkers

Drought and salinity limit crop yields throughout the world, and understanding the plant response mechanisms to these stresses can provide new insights into how to breed stress-tolerant genotypes. The leaf and root responses of five different licorice (Glycyrrhiza glabra) genotypes to drought and salinity stresses were investigated in field conditions, using control conditions and five stress levels (slight, moderate and intense drought; moderate and intense salinity). Parameters measured include leaf and root macronutrient concentrations, leaf photosynthetic pigment concentrations, leaf and root total antioxidant and phenolic compound concentrations and root concentrations of the secondary metabolites glycyrrhizin and glabridin. Drought and salt stresses caused progressive decreases in leaf photosynthetic pigment concentrations, accompanied by major changes in macronutrient concentrations in leaves (including increases in Na, Cl, K and Ca and decreases in Mg) and roots (including increases in Na and Cl, and decreases in K, Ca and Mg). Increases in leaf antioxidant enzyme activities (CAT and APX), leaf and root total antioxidant activity and total phenolics were also observed with both stresses. Multiple regression analysis suggest that it could be possible to make a fair estimation of the root glycyrrhizin concentrations using parameters that can be measured more easily, such as the leaf concentrations of macronutrients and photosynthetic pigments.

Effects of mycorrhizae and water conditions on perennial ryegrass growth in rare earth tailings.

Mycorrhizal symbioses, which include plant roots and arbuscular mycorrhizal fungi (AMF), can significantly enhance plant resistance and promote the absorption of soil nutrients by plants. A greenhouse experiment was conducted to investigate the effects of three AMF species (Glomus mosses, Glomus etunicatum and Glomus versiforme) on the height, biomass, malondialdehyde (MDA) and proline contents and antioxidant enzyme activities of perennial ryegrass (Lolium perenne) under different water supply treatments. Potted experimental soil samples were collected from the abandoned rare earth tailings in Ganzhou, Jiangxi. The results showed that all three AMF species infected ryegrass under the different treatments. Under severe drought stress, G. mosses had the most significant effects on the promotion of ryegrass performance. After inoculation, the height and whole-plant biomass of ryegrass increased by 60.44% and 150%, respectively. In addition, inoculation with AMF significantly reduced the content of MDA and proline in the ryegrass leaves in all water supply treatments except the moderate drought stress treatment, in which there was no effect. The leaf antioxidant enzyme activity was also measured. The results showed that under severe drought stress, inoculation with Glomus mosses significantly increased the activities of CAT and SOD in ryegrass and enhanced the resistance of plants. A possible reason that AMF promotes host plant growth and enhances drought resistance is that AMF directly increases the absorption of soil water and minerals by host plant roots and indirectly improves the physiological metabolism of plants.

Effects of metalaxyl enantiomers stress on root activity and leaf antioxidant enzyme activities in tobacco seedlings.

The objective of this experiment was to study the effects of metalaxyl enantiomers on the activity of roots and antioxidative enzymes in tobacco seedlings. Water culture experiment was conducted to analyze the effects of different concentrations of metalaxyl enantiomers (30 and 10mgL-1 ) on root activity and leaf superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities and malondialdehyde (MDA) content of tobacco seedlings. The results showed that metalaxyl significantly inhibited root activity and significantly improved leaf SOD, POD, and CAT activities and MDA content. A better physiological response in tobacco seedlings was observed at 30mgL-1 than at 10mgL-1 metalaxyl. The stereoselectivity for different enantiomers had no obvious effect on root activity and the leaf POD activity, but it affected significantly the SOD and CAT activities and MDA content. The SOD activity was promoted more by R-enantiomer than by S-enantiomer at 30mgL-1 metalaxyl, and the same effect was observed on CAT activity from the beginning to the end of the stress period. The MDA content under the stress by R-enantiomer was higher than that under the stress by S-enantiomer at 10mgL-1 metalaxyl.

Response of water deficit-stressed Vigna unguiculata performances to silicon, proline or methionine foliar application

Abstract Environmental stresses are increasing over time adversely affecting crop productivity. To face these stresses, plants adopt endogenous mechanisms, but they are not enough in most cases. Therefore, the effect of exogenous application of proline, silicon (Si) or methionine on growth and yield criteria, leaf physio-biochemical properties and leaf anatomical structure of cowpea plants grown under three levels of water deficit (W0; 60, W1; 40 and W2; 20% of soil water holding capacity) was investigated. The water level W0 was adequate to optimum cowpea plant growth and specified as a control. Results obtained indicated that growth criteria (i.e., shoot dry weight, plant height, leaf area and number of branches per plant), yield characteristics (i.e., dry seed weight and biological yield per plant, and 100-seed weight), contents of leaf chlorophylls a and b, total carotenoids, shoot and seed nutrients (i.e., N, P and K), and leaf relative water content and membrane stability index were significantly decreased, while activity of leaf antioxidant enzymes such as peroxidase (POX), superoxide dismutase (SOD) and catalase (CAT), content of leaf proline and electrolyte leakage, and shoot Si were significantly increased under water deficit stress (W1 and W2) conditions compared to the control (W0). However under water deficit stress, foliar application of proline, Si or methionine seemed to overcome the harmful effects of water deficit stress, at varying degrees, on the abovementioned cowpea plants characters, which were improved, compared to the corresponding controls. The Si was the most helpful one, where it increased growth criteria (i.e., shoot dry weight, plant height, leaf area and number of branches per plant), yield characteristics (i.e., dry seed weight and biological yield per plant, and 100-seed weight), contents of leaf chlorophylls a and b, total carotenoids, shoot and seed nutrients (i.e., N, P and K), and leaf relative water content and membrane stability index, and further increased shoot Si content and leaf antioxidant enzyme activities of cowpea plants compared to those of either proline or methionine application. For leaf anatomical features, the width of midvein and xylem, and the thickness of midvein, phloem and xylem tissues, and palisade and spongy tissues of leaf blade were decreased with increasing the water deficit stress; however, foliar spray of Si improved all histological features compared to those of untreated plants.

Measurements of Proline and Malondialdehyde Content and Antioxidant Enzyme Activities in Leaves of Drought Stressed Cotton

Measurements of Proline and Malondialdehyde Content and Antioxidant Enzyme Activities in Leaves of Drought Stressed Cotton

Antioxidant Activity in Salt‐Stressed Barley Leaves: Evaluating Time‐ and Age‐Dependence and Suitability for the Use as a Biochemical Marker in Breeding Programs

AbstractSoil salinity disturbs the equilibrium between reactive oxygen species (ROS) production and removal, leading to a dramatic increase in ROS concentration and oxidative damage. Enzymatic scavenging is one of the two main mechanisms involved in ROS detoxification in plants. This study has investigated the role of major antioxidant (AO) enzymes in mitigating salinity‐induced oxidative stress in plant shoots. Firstly, two barley varieties were used to evaluate the activity of major AO enzymes in different leaves and at different times after salt treatment. Our results showed that AO enzyme activities had strong tissue and time specificity. A further study was conducted using six barley varieties contrasting in salinity tolerance. AO enzyme activities and proline contents were measured in the third leaves of seedlings after plants were treated with 240 mm NaCl for 10 days. No significant correlation was revealed between leaf AO activity and either plant grain yield or plant survival rate under salt stress. In contrast, a significant increase in leaf proline content under salt stress was found in all sensitive varieties, while in most tolerant varieties, salt stress did not change leaf proline level. It is concluded that although salinity induces changes in leaf AO enzyme activities, the changes cannot be used as biochemical indicators in breeding for salinity tolerance.