Journal of Plant Process and Function

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Rozita Kabiri, Fatemeh Nasibi*, Hassan Farahbakhsh 1Department of Agronomy, Faculty of Agriculture, 2Department of Biology, Faculty of Sciences and 3Horticultural Research Institute, Shahid Bahonar University of Kerman (Received: 01 October 2012 Accepted: 17 March 2013) Abstract: Drought stress is one of the main stresses that inhibits the growth of plants due to mainly disturbance of the balance between production of reactive oxygen species and antioxidant defense and thereby causing oxidative stress. Evaluation of medicinal plants tolerance to drought stress in order to plant them in dry region is very important. In this research, oxidative parameters of drought stress induced by different concentration of polyethylene glycol solutions in Nigella plant were investigated. To control experimental conditions including the inhibitory effects of the other factors such as soil nutrition the hydroponic medium was used. In this study, drought stress significantly increased the H2O2 content, lipid peroxidation and lipoxygenase activity which were showed the oxidative stress induced by drought in Nigella plants. Study of the defense mechanisms, through the measurement of the antioxidant enzymes activities indicated that drought stress increased the activity of ascorbate peroxidase, catalase and guaiacol peroxidase. However in this research, we observed that the increment in drought level had no significant effects on catalase and guaiacol peroxidase activity. It seemed that in this investigation the increment of proline might be related to both osmotic and antioxidant characteristic of this compound. Increase of lipid peroxidation and H2O2 content in drought stress showed that the scavenging and quenching of ROS were out of the plant ability and the induction of plant defense mechanism against oxidative damages was not effective. Therefore, the application of exogenous protect compound could increase the antioxidant capacity of plant against stress condition. *Corresponding author:

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The effects of different concentrations of walnut leaf extract on physiological and biochemical characteristics of parsley plants inoculated with mycorrhizal fungus Glomus versiforme and non-mycorrhizal plants were studied under greenhouse conditions. In the present study, three different concentrations of walnut extract (full extract, half and quarter concentration levels) were used. The results of the 45 day-old plants showed that the increasing of the concentration of walnut extract decreased amounts of chlorophyll a and b but increased the carotenoids content. This increase was more pronounced in mycorrhizal plants than non-mycorrhizal ones. When ¼ concentration of extract was applied the total protein content in mycorrhizal and non-mycorrhizal plant shoots was increased and then decreased at higher concentrations with increasing in concentrations of aqueous extract of walnut leaves. The free amino acids and proline content in plants were increased but such effects in non-mycorrhizal plants were greater than in mycorrhizal ones. Ascorbate peroxidase (APX) and Guaiacol peroxidase (GPX) activities in mycorrhizal and non-mycorrhizal plants also increased due to walnut extract, but the increased activity of these enzymes was higher in the inoculated plants. Results of this study indicated that by inoculating mycorrhizal fungi with root of parsley adverse potential effects of allelopathic extract on the physiological and biochemical characteristics of these plants.

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Because of water and soil salinity, there are many problems for turfgrass in Iran. use of salt tolerant native plants is one of the appropriate way for solving these problems. This study was undertaken to evaluate effect of four levels of salinity (less than2, 4, 8 and 16 ds/m) on morphological and physiological characteristics in naitive grass, Wheatgrass (Agropyron desertorum). The experiment was performed based on randomized complete block design with three replications. The results showed that salinity stress decreased turfgrass qualiy (TQ), fresh and dry weight of shoots and roots, relative water content (RWC) and root and shoot potassium contents. Also, salinity stress increased shoot and root sodium contents, electrolyte leakage (EL), proline contents and activity of enzymes. According to reduction in TQ and RWC and increase in EL under salinity stress, it seems that increasing in proline contents and enzymes activities could not be able to reduce the damage caused by stress. All of the measured parameters in this study showed the significant differences with control plant in 4 ds/m salinity level. The results showed the wheatgrass is salt-sensitive and salt tolerance it was less than 4 (ds/m).

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5-aminolevulinic acid is the key precursor of all tetrapyrrole compounds such as heme, chlorophylls, bacteriochlorophyll, phytochrome and vitamin B12. In this study, the effect of 5-aminolevulinic acid, in reduction of salt stress in Lycopersicun esculentum Mill. var. Falcato were studied. Salinity at three levels (0, 50 and 75 mM NaCl) and ALA treatment at three levels (0, 1 and 2 mM) were investigated in this study. Salinity reduced growth parameters, phenolics content and phenylalanine ammonialyase activity, and increased lipid peroxidation, ion leakage and the activity of superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase and guaiacol peroxidase. 5-aminolevulinic acid application in two levels increased the growth parameters, phenolics content, and the activity of phenylalanine ammonialyase, superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase and guaiacol peroxidase, and decreased lipid peroxidation and ion leakage. These results show that the application of 5-aminolevulinic acid, via enhancing the activity of enzymatic antioxidant system, is effective in salt tolerance of tomato plants.

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Water deficit is one of the most important environmental stresses limiting plant growth and productivity around the world including Iran. Plants adapted to environmental stress with several strategies such as changes in antioxidant enzyme metabolism. Pennyroyal (Mentha pulegium L.) is an aromatic and medicinal plant of the Labiatae family that is widely used in traditional medicine. In this research, the effects of water deficit stress on growth, photosynthesis and antioxidant enzyme activities in leaf and root organs of M. pulegium plants were studied. Complete randomized block design have been used with four replications. Water deficit was studied at four field capacity levels (100, 75, 50 and 25%). Results showed that the growth, productivity and photosynthesis parameters significantly decreased under water deficit stress. Water deficit significantly increased the activity of antioxidant enzyme such as superoxide dismutase, peroxidase and ascorbate peroxidase in both organs, but the level of increase was more in roots than leaves of plant. Unlike to other enzymes, catalase activity decreased with the increase of water deficit levels, and highest activity was observed in leaves. It seems that pennyroyal plants can tolerate water deficit stress by dedicating less carbon source for growth, increase of antioxidant enzyme activity and regulation of antioxidant enzyme distribution in different organs.

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Nitric oxide (NO) has signaling property in plants, therefore the effect of nitroprusside (SNP) as an NO producing agent on viability in the cell culture, lipid peroxidation and activity of superoxide dismutase, catalase and peroxidase in the callus of Catharantus roseus was investigated. Cell suspension was prepared from callus of Catharantus roseus, and the cells were treated with 0, 10, 50, 100, 150, 200 and 250 μM of sodium nitroprusside for 1, 3 and 6 days to determined the cell viability(based on trypan blue staining as well as MTT colorimetric assay). Then using 100 and 200 mM of sodium nitroprusside as selected dose, the cell suspension was used to investigate the cell morphological changes. In addition the callus tissue was treated with the same dose to estimate the level of lipid peroxidation and the activity of superoxide dismutase, catalase and guaiacol peroxidase. Comparison of the data from trypan blue and MTT methods showed that the significant (p<0.05) differences in viability was concentration dependent with respect to control. Base on the morphology, SNP caused changes in the shape and size of the cell nuclei as well as disturbance in the chromatin. In addition changes in the cytoplasm such as shrinkage and cell border deform was observed in the treated cells compare to control. Also activity of the investigated enzymes following the oxidative stress increased significantly (p<0.05). The level of malondialdehyde as an indicator of lipid peroxidation also increased significantly. Sodium nitroprusside as an NO producing agent caused cellular membrane damage which results in cell viability reduction in the callus of catharantus roseus. Although the activity of the antioxidant enzymes increased significantly with respect to the oxidative stress but the produced cellular response was not able to compensate the damages.

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In this research the effect of four concentrations of nickel and copper (25, 50, 100, and 200 µM) on root and shoot length, fresh and dry weight, leaf surface, and photosynthetic pigments (Chlorophyll a, b and carotenoids), sugar, malondialdehyde, hydrogen peroxide content and antioxidant enzyme activity (CAT and APX) in Okra plants were evaluated. The results showed that in those plants which were treated with all concentrations of copper and nickel, the content of photosynthetic pigments and leaf surface were reduced significantly in comparison with control. In this investigation it was found that shoot and root length, dry weight and fresh weight of shoot and root which were treated with concentrations 50, 100, and 200 µM of cupper and 100 and 200 µM of nickel were reduced significantly when compared with the control. Content of soluble sugars in shoot and root plants which were treated with all concentrations of nickel and concentrations 50, 100, and 200 µM of cupper increased significantly in comparison with the control. Also, content of malondialdehyde, hydrogen peroxide content and antioxidant enzyme activity (CAT and APX) increased significantly in shoot and root plants which were treated with concentrations 50, 100, and 200 µM of copper and nickel when compared with control.

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To find out the biochemical and physiological responses of purple coneflower (Echinacea purpurea L.) medicinal plant to low temperature stress, a compeletly randomized design with three replications was conducted at Sari Agricultural Sciences and Natural Resources University in 2013. Five months old of coneflower seedlings exposure to three temperature levels of 23 ºC (control), 4 and 4 ºC for 6 h and then electrolyte leakage and malondialdehyde (MDA), enzyme activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) and polyphenol oxidase (PPO), protein oxidation of the leaves, total phenols and flavonoids contents, percentage of DPPH free radical inhibition, as well as chlorophyll fluorescence parameters included F'm, F'v/F'm, qp, NPQ and ФPSII were determined. Results of experiment showed a significant increment of electrolyte leakage and malondialdehyde (MDA) content in leaves where the highest electrolyte leakage (55.7%) and MDA (12.3 nanomol/ g FW) were obtained at 4 ºC. In this study, the maximun activity of antioxidant enzymes (SOD, CAT and APX) were recorded when coneflower seedlings exposure to temperature lower than 4 ºC. Activity of POD and PPO enzymes, however, were decreased when temperature reduced to 4 ºC. The highest total protein content was calculated at 4 ºC that showes about 65% increment than control. Low temperature stress reduced total phenolic and flavonoid content of seedlings. Also, the highest antioxidant capacity of leaves (0.93%) were measures in control seedlings. No significant differences were observed between the fluorescence parameters in dark-adapted leaves. In light-adapted leaves, F'm and F'v/F'm content decreased with increasing stress and the highest content of the NPQ and qP were recorded at 4 ºC. Meanwhile, the lowest ФPSII was obtained at 4 ºC. In conclusion, it seems that the coneflower plant relatively had good tolerance to low temperature stress to 4 ºC.

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Tuberosa (Polianthes tuberosa L.) is one of the most important cut flowers in Iran and word wide which the increment of postharvest life of this flower is very important. In this research proline as an antioxidant compound was used in 0(control), 1 and 10 micro molar concentrations and the effects of this compound on some morphological and physiological characteristics and vase life of tuberosa cut flower were investigated. The experiments were performed in a completely randomized design with 3 replicates. Results showed the significant effect of proline on vase life of tuberosa in both concentrations. The percentage of open flower increased in both proline concentrations. Finding showed the significant decrease in the wilted percentage of flower in both concentration of proline when compared with control flowers. The abscission percentage of flower also is very lower than the control flower. In according to the results, proline in both concentrations decreased the water loss and membrane leakage and the 10µM proline had the most effect. In flowers which were treated with proline, the activity of guaiacol peroxidase, catalase, ascorbate peroxidase and phenyalanine ammonialyase enzymes increased while the activity of polyphenol oxidase enzyme decreased. It seems that proline increment the postharvest life of tuberosa flower through the increase of antioxidant enzymes and decrease of polyphenol oxidase activity.

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Water deficit is a common and major constrain for agricultural production in arid and semi-arid parts of the world like Iran, to the extent that it might threaten the nation’s food security in years to come. Seed germination is a crucial growth stage that is often affected by environmental stresses, including drought. This study investigated the effects of four levels of water potential (i.e. 0, -0.2, -0.4 and -0.6 MPa) on germination, seedling characteristics, soluble carbohydrates, proline and polyphenols contents, and antioxidant enzymes activities of 12 fennel genotypes. Low water potentials reduced germination percentage and speed of germination, seedling fresh and dry masses, shoot length and superoxide dismutase specific activity, though it led to increases in root length, soluble carbohydrates, proline and polyphenols contents, and catalase specific activity. The 12 genotypes according to the degree of decreases in germination percentage at -0.6 MPa compared to control, were classified into three groups, including drought-tolerant (Shiraz, Yazd, Kerman and Mashhad), moderately-tolerant (Hamadan, Kashan, Bushehr and Urmia) and drought-sensitive (Birjand, Ardabil, AviSina and Isfahan). Mashhad, as a drought-tolerant genotype, indicated the greatest germination percentage, seedling fresh and dry masses, root length, soluble carbohydrates, proline and polyphenols contents, and catalase and superoxide dismutase specific activities among 12 genotypes studied. The results obtained in this study demonstrate some key aspects of the drought tolerance-related characteristics of fennel at germination stage that may help elucidate the whole plant performance of fennel at drought-stricken areas, when integrated with results from field studies.

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Abstract Thioredoxins are invoved in redox regulation of many cellular processes. In this study the role of NADP+-Thioredoxin reductase C (NTRC) in the control of leaf senescence was investigated by biochemical characterization of Arabidopsis ntrc mutants. Forty days old wild type and two ntrc mutant lines were incubated either under normal dark-light or continous darkness regimes for 6 days as control and senescence treatment, respectively. Growth parameters, the contents of carbohydrates, pigments and the activity of some antioxidant enzymes were compared between wild type and ntrc mutant lines during dark induced senescence. Darkness led to decreased fresh and dry weights, chlorophylls and carotenoides, starch and protein contents in both wild type and mutant plants and there were no significant differences in the interactions of genotypes and treatments regarding to theses parameters. Darkness also induced the accumulation of anthocyanins, total and non-reducing sugars however, the accumulation of the carbohydrates in mutant lines was more pronounciated than wild type plants and again there were no significant differences in response of wild type and mutants to dark treatment. The activities of catalase, peroxidase and polyphenol oxidase of mutant lines were significantly greater than wild type plants. While darkness decreased the activities of ascorbate peroxidase and catalase it led to increased activities of peroxidase and polyphenol oxidase especially in the mutant lines. There were significant differences in the activities of all four enzymes between mutant and wild type plants in response to darkness. Thus, it appears that defects in NTRC mainly affects the activities of antioxidant enzymes rather than the other studied biochemical parameters of plants during the senescence process. This study might be useful in future breeding programs for controlling senecence process to achieve better performance of crop plants.

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Air pollution is a serious problem at recent years which progressively increases. This study was accomplished in order to more understanding of morphological and physiological responses of acid rain on Persian maple trees as an ornamental and industrial plant. Accordingly, three-year old Persian maple seedlings were submitted based on completely randomized design to four different acid rain regimes: pH 3, 4, 5 and near neutral (pH 6) as control, in tree replications, during 10 days. At the end of experiment, some visible changes such as necrotic spots and leaf marginal wrinkle were observed in the plant leaves sprayed only with AR of pH 3. Results showed that electrolyte leakage (EL) and lipidperoxidation (LPO) amount significantly increased as pH values of AR decreased. However, reducing of AR had no effect on leaf chlorophyll content by pH 4.0, whereas AR of pH 3.0 dramatically degraded it. In addition, AR did not significantly affect superoxide dismutase (SOD) activity. On the contrary, it enhanced peroxidase (POD) and ascorbate peroxidase (APX) activities by pH 4.0, but AR of pH 3.0 markedly decreased them, thereby, the antioxidative system was weakened and injury appeared. Overall, our results cleared that Persian maple was resistant to AR by pH 4.0, while it is certainly susceptible to pH 3.0 and lower pH values.

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Drought is one of the most significant a biotic stresses that affecting plant’s growth and development wild barley, H.spontaneum, the progenitor of cultivated barley has a high potential in terms of tolerance to environmental stresses. This research was performed on nine genotypes of Hordeum spontaneum, to study drought tolerance in a split plot experiment based on Randomized Complete Block Design with three replications under field shelter in 2011-2012. The main plot included three levels of water stress as normal irrigation, water withholding at flowering stage and no irrigation and sub-plots comprised the studied genotypes. The results indicated that the effect of drought stress on plant height, grain yield, biomass, relative water content, osmotic adjustment, stomatal conductivity, chlorophyll content, catalase, ascorbate peroxidase and peroxidase, protein, malondialdehyde, and proline was significant (P<0.01). The results of principal component analysis on the whole evaluated traits in drought stress condition located the studied genotypes in four groups. The first and second group comprised genotypes 6, 4 and 5. These genotypes had significantly higher grain yield, relative water content, chlorophyll content, enzymatic activity of peroxidase and ascorbate peroxidase and lower content of malondialdehyde, leaf temperature and osmotic potential (more negative) and therefore, were identified as tolerant genotypes.

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Drought stress stimulates the production of reactive oxygen species (ROS) in chloroplasts. ROS laed to lipid peroxidation and damage to the cell membrane. In the current study, the effect of different concentrations of silicon were examined on oxidative stress caused by drought in fennel plant. The experimental design was a split plot based on RCBD with three replications in which irrigation regimes includingirrigation at 100%, 70% and 40% of field capacity were assigned as main plots and five levels of silicon foliar sprays (0, 2.5, 5, 7.5 and 10 mM) were allocated to sub plots. The experiment was conducted in 2009 at the Zabol University research farm, Zabol, Iran. The results showed that drought stress significantly decreased chlorophyll a, chlorophyll b, carotenoids, leaf relative water content and catalase activity. In drought conditions, malondialdehyde levels and electrolyte leakage showed a 2 -fold increase over the control. Silicon treatment (7.5 mM) accompanied by drought, increased the activity of peroxidase and ascorbate peroxidase, proline and soluble sugars by 18, 25, 14 and 28%, respectively and decreased malondialdehyde and electrolyte leakage by 30 and 28%, respectively over the control, suggesting that silicon spraying (5 and 7.5 mM) could increase the ability of plants in response to drought stress by strengthening the antioxidant system of the plant and increasing osmolytes, and have protective effect against lipid peroxidation, induced by stress.

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Salinity stress is one of the limiting factor determining plant growth and development through negative effects on plant physiological processes. Interaction of salinity and certain plant growth regulators such as gibberellin affected physiological and biochemical responses in plants. In present research, the effects of different concentrations of sodium chloride (0, 30, 60, 90 and 120 mM NaCl) and gibberellin (0 and 100 µg L-1) on anthocyanin, prolin contents and activity of catalase and peroxidase enzymes, were studied. Results showed that different concentrations of NaCl caused significant increase in anthocyanin and proline contents. The individual concentrations of NaCl increased the activity of catalase and peroxidase considerably. Changes in the activity of the antioxidant enzymes, catalase and peroxidase, indicated that NaCl causes oxidative stress in Savory (Satureja hortensis L.) plant. With adding GA3 in medium, activity of these enzymes increased more than those of control and NaCl single treatments. The results showed that GA3 alleviates adverse effects of NaCl and could increase the tolerance of Satureja hortensis to salinity stress by increasing activities of antioxidants.

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It is essential to identify and determine the properties of native plants as natural genetic resources. The present study was performed to identify the Mindium (Michauxi) laevigata species using molecular and biochemical procedures such as genomic DNA extraction, sequencing, and antioxidant capacity and protein content determination at both vegetative and generative phases in various parts of the plant. For this purpose, Mindium laevigata plants were collected from natural habitats and their genomic DNAs were extracted and purified. This was followed by the extraction of 18S ribosomal DNA sequence from the genomic DNA by PCR and its analysis to determine the antioxidant enzymes (peroxidase, ascorbate peroxidase, and catalase). Accordingly, the proteins were quantitatively and qualitatively assayed at both vegetative and reproductive stages in the different plant organs of roots, stems, and leaves. Ascorbate peroxidase and catalase activities were detected in  the stem samples at the vegetative and generative phases, respectively. Gel electrophoresis bands of the total protein were found to be different in various parts and at different developmental stages of the plant. Another aspect of the study involved the use of the phylogenetic tree for the biosystematic investigations of Mindium laevigata. Molecular analyses resulted in the inscription of a new gene in GenBank under the accession number KC294445.1. Mindium laevigata seems to be a rich source of antioxidant enzymes and proteins and as such it is recommended for further research.

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Carum copticum L. is a medicinal plant of the Apiaceae family with medicinal properties. In this study, the effects of drought stress on the photosynthetic pigments and essential oils as well as the enzymatic and non-enzymatic mechanisms of the seedlings and callus of C. copticum were investigated within the framework of a controlled experiment under in vitro conditions. For this purpose, the seedlings of C. copticum were cultured in the Murashige and Skoog medium containing three levels (0, 3, and 6%) of either sorbitol or mannitol. Furthermore, its calli were independently cultured in the Murashige and Skoog (MS) medium containing 0.25 mg.L^-1 2, 4-dichlorophenoxyacetic acid, 1 mg.L^-1 benzyl amino purine, and different levels (0, 3, and 6%) of either sorbitol or mannitol. Both sorbitol and mannitol were found to reduce the photosynthetic pigments and carotenoid contents but increased the anthocyanin and flavonoid contents significantly. However, these effects were significantly more severe in plants submitted to mannitol, as compared to the sorbitol-treated ones. With the exception of the mannitol-treated leaf samples whose phenolic contents decreased with increasing drought concentration in the culture media, the phenolic contents in the other samples increased relative to those in the control samples. The ascorbate peroxidase activity was found to decrease in all the treated samples while the catalase activity greatly increased, particularly in the mannitol-stressed plants. Compared to the control, drought led to a significant increase in superoxide dismutase activity in all the samples treated with 6% sorbitol and in the calli samples treated with 3% mannitol, whereas the seedlings grown under mannitol treatment showed almost no difference with the control plants. In addition, drought stress changed the essential oil compounds of both the seedlings and the calli of C. copticum. Analysis of the essential oil constituents by Gas chromatography–Mass Spectrometry (GC–MS) showed thymol, gamatherpinen, and parasimen to be the main essential oil components which increased in quantity under high stress conditions. These bioactive compounds have many industrial and medicinal applications.

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Borage (Borago officinalis L.) is a valuable medicinal plant and its production to meet the needs of the pharmaceutical industry has a high value. The objectives of this work were to evaluate water quality and different fertilizer systems on some physiological and biochemical characteristics of borage. The experiment was conducted as a split-plot arrangement based on compelet block design with three replications in 2012 at the research farm of Zabol University, Zabol, south Iran. The treatments were two irrigation sources: irrigation with fresh and saline water as main-plot, and four fertilization system: application of NPK at 80:40:30 kg ha-1, 40 ton of manure ha-1, NPK at 40:20:15 kg ha-1 plus 20 ton of manure ha-1 and no soil fertility as sub-plot. Salt irrigation water significantly increased antioxidant enzymes, carbohydrates and proline contents. The low quality of irrigation water reduces plant protein, chlorophyll fluorescence and moisture content, however mucilage content did not influence. Application of fertilization significantly increased all studied traits compared with the control except chlorophyll fluorescence. Combination of organic and inorganic fertilizer was more effective than sole application. Interaction of water quality by fertilization was significant only on ascorbate peroxidase. These results suggested that although irrigation with saline water decreased quantitatve and qualitative characteristics of borage, however, replacement part of chemical fertilizers with organic fertilizers can reduce environmental pollution.

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  Water deficit can be considered as one of the most important abiotic factors limiting plant function, which has also adverse affects on growth and production of medicinal plants. In this research, in order to evaluate the effects of water deficit stress on of Artemisia dracunculus plant, a completely randomized design with three replications was performed in greenhouse conditions. The experimental treatments were different levels of irrigation based on control (90% of field capacity), T1: 60% of field capacity and T2: 40% of field capacity. Four weeks after treatment, physiological and biochemical indices were measured. Results showed that, water deficit stress had significant effects on measured traits and the average value of some traits such as: fresh and dry weight, leaf area, relative water content and shoot length were decreased under stress in both A. dracunculus collections in compare to control plants. The least average value of these traits was observed in T2 plants. Analysis of biochemical data also showed that, enzyme activity of peroxidase, proline and soluble sugars contents and the specific activity of peroxidase were increased in both A. dracunculus collections under water stress condition. However, enzyme activity of catalase, content of photosynthetic pigments (chl a, chl b and carotenoides), soluble protein content and the specific activity of catalase were decreased under stress. As a conclusion, Irrigation level at 40% of field capacity can be considered as stress level for this plant. Furthermore, A. dracunculus can respond to water deficit stress by increasing of the contents of proline and soluble sugars and the activity of peroxidase as one of antioxidant enzymes.

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Salinity is one of the environmental factors that has a critical influence on plant growth and development.  Researchers have shown that some plant growth regulators such as nitric oxide improves the plants resistance to environmental stresses such as salinity, heat, cold and drought. Sodium nitroprusside (SNP) commonly was used as a nitric oxide (NO) donor in plants. The aim of this research was to evaluate the role of SNP on salt tolerance of Zinnia elegans and its effects on some morphological, physiological and biochemical characteristics of this plant. A factorial experiment based on completely randomized design was conducted with five levels of salinity 0 (control), 25, 50, 75 and 100 mM NaCl and four levels of sodium nitroprusside (SNP) (foliar spray) 0.0 (control), 0.25, 0.50 and 0.75 mM with 3 replications. In salinity level of 50 mM, the length of stem and root was reduced 41.22 and 29.63 percent in compared to control. In salinity level of 50 mM, application of 0.5 mM sodium nitroprusside, increased total antioxidant capacity, glycine betain and proline 1.93, 3.98 and 2.12 times respectively compared to control. It also increased ascorbate peroxidase, catalase and guaiacol peroxidase 5.15, 4.69 and 2.78 times respectively compared to control. The application of SNP (especially at salt concentrations lower than 50 mM) ameliorated the adverse effects of salt stress, in Zinnia elegans plant.