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Öğe Exogenous Nitric Oxide (as Sodium Nitroprusside) Ameliorates Polyethylene Glycol-Induced Osmotic Stress in Hydroponically Grown Maize Roots(SPRINGER, 2014) Yildiztugay, Evren; Ozfidan-Konakci, Ceyda; Kucukoduk, MustafaThe present study was designed to examine whether exogenous sodium nitroprusside (SNP) supplementation has any ameliorating action against PEG-induced osmotic stress in Zea mays cv. FRB-73 roots. Twenty percent or 40 % polyethylene glycol (PEG6000; -0.5 MPa and -1.76 MPa, respectively) treatment alone or in combination with 150 and 300 mu M SNP was applied to hydroponically grown maize roots for 72 h. Although only catalase (CAT) activity increased when maize roots were exposed to PEG-induced osmotic stress, induction of this antioxidant enzyme was inadequate to detoxify the extreme levels of reactive oxygen species, as evidenced by growth, water content, superoxide anion radical (O (2) (aEuro cent a') ), hydroxyl radical (OHaEuro cent) scavenging activity, and TBARS content. However, supplementation of PEG-exposed specimens with SNP significantly alleviated stress-induced damage through effective water management and enhancement of antioxidant defense markers including the enzymatic/non-enzymatic systems. Exogenously applied SNP under stress resulted in the up-regulation of glutathione peroxidase (GPX), glutathione S-transferase (GST), ascorbate peroxidase (APX), glutathione reductase (GR), total ascorbate, and glutathione contents involved in ascorbate-glutathione cycle. On the other hand, growth rate, osmotic potential, CAT, APX, GR, and GPX increased in maize roots exposed to both concentrations of SNP alone, but activities of monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase decreased. Based on the above results, an exogenous supply of both 150 and 300 mu M SNP to maize roots was protective for PEG-induced toxicity. The present study provides new insights into the mechanisms of SNP (NO donor) amelioration of PEG-induced osmotic stress damages in hydroponically grown maize roots.Öğe Halophytes as a source of salt tolerance genes and mechanisms: a case study for the Salt Lake area, Turkey(CSIRO PUBLISHING, 2016) Ozfidan-Konakci, Ceyda; Uzilday, Baris; Ozgur, Rengin; Yildiztugay, Evren; Sekmen, A. Hediye; Turkan, IsmailThe worst case scenario of global climate change predicts both drought and salinity would be the first environmental factors restricting agriculture and natural ecosystems, causing decreased crop yields and plant growth that would directly affect human population in the next decades. Therefore, it is vital to understand the biology of plants that are already adapted to these extreme conditions. In this sense, extremophiles such as the halophytes offer valuable genetic information for understanding plant salinity tolerance and to improve the stress tolerance of crop plants. Turkey has ecological importance for its rich biodiversity with up to 3700 endemic plants. Salt Lake (Lake Tuz) in Central Anatolia, one of the largest hypersaline lakes in the world, is surrounded by salty marshes, with one of the most diverse floras in Turkey, where arid and semiarid areas have increased due to low rainfall and high evaporation during the summer season. Consequently, the Salt Lake region has a large number of halophytic, xerophytic and xero-halophytic plants. One good example is Eutrema parvulum (Schrenk) Al-Shehbaz & Warwick, which originates from the Salt Lake region, can tolerate up to 600mM NaCl. In recent years, the full genome of E. parvulum was published and it has been accepted as a model halophyte due to its close relationship (sequence identity in range of 90%) with Arabidopsis thaliana (L. Heynh.). In this context, this review will focus on tolerance mechanisms involving hormone signalling, accumulation of compatible solutes, ion transporters, antioxidant defence systems, reactive oxygen species (ROS) signalling mechanism of some lesser-known extremophiles growing in the Salt Lake region. In addition, current progress on studies conducted with E. parvulum will be evaluated to shed a light on future prospects for improved crop tolerance.Öğe The humic acid-induced changes in the water status, chlorophyll fluorescence and antioxidant defense systems of wheat leaves with cadmium stress(ACADEMIC PRESS INC ELSEVIER SCIENCE, 2018) Ozfidan-Konakci, Ceyda; Yildiztugay, Evren; Bahtiyar, Mustafa; Kucukoduk, MustafaThe using of bio-stimulant in plants grown under stress conditions for enhancing nutrition efficiency and crop quality traits is an effective approach. One of the bio-stimulants, humus material, is defined as humic acid (HA). HA application as a promotion of plant growth to plants grown in the heavy metals-contaminated soils has promised hope in terms of effects on plants but the its limiting effect is the application dose. Therefore, the wheat seedlings were grown in hydroponic culture for 21 d and the various concentrations of humic acid (HA; 750 or 1500 mg L-1) were treated alone or in combination with cadmium (Cd) stress (100 or 200 mu M) for 7 d. The results showed that after Cd stress treatment, water content (RWC), osmotic potential (psi(Pi)) and chlorophyll fluorescence parameters decreased and proline content (Pro) increased for 7 d. In spite of activated peroxidase (PDX) and ascorbate peroxidase (APX), stress induced the toxic levels of hydrogen peroxide (H2O2) accumulation. Cd stress triggered lipid peroxidation (TBARS content). HA application successfully eliminated the negative effects of stress on RWC, psi(Pi) and photosynthetic parameters. In the presence of HA under stress, the increased activation of superoxide dismutase (SOD), catalase (CAT) and NADPH-oxidase (NOX) enzymes and ascorbate, glutathione and GSH/GSSG ratio observed. Only 750 mg L-1 HA under stress conditions induced the activities of monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR), and dehydroascorbate (DHA) content. After the combined application of HA and Cd stress, the low contents of H2O2 and TBARS maintained in wheat leaves. Hence, HA successfully eliminated the toxicity of Cd stress by modulating the water status, photosynthetic apparatus and antioxidant activity in wheat leaves.Öğe The impact of selenium application on enzymatic and non-enzymatic antioxidant systems in Zea mays roots treated with combined osmotic and heat stress(TAYLOR & FRANCIS LTD, 2017) Yildiztugay, Evren; Ozfidan-Konakci, Ceyda; Kucukoduk, Mustafa; Tekis, Seyit AhmetSelenium (Se), regarded as an antioxidant, has been found beneficial for plants growing under stressed conditions. To investigate whether the Se application helps to improve stress tolerance, sodium selenite (Na2SeO3 . 5H(2)O, 5-15 mu M)was hydroponically applied to Zea mays variety OSSK-713-roots under heat and/or PEG-induced osmotic stress (25% PEG-6000) for 8 h. The individual/combined stress caused accumulation of reactive oxygen species (ROS). While only superoxide dismutase (SOD) increased with heat stress alone, the activities of SOD, catalase (CAT) and ascorbate peroxidase (APX) increased under PEG exposure. The combination of these stresses resulted in an induction of both SOD and CAT activities. Lipid peroxidation (TBARS) levels were also high in all the stress treatments, especially under the combination treatment. Addition of Se not only improved the activities of SOD, APX and glutathione reductase (GR) in stress-treated roots, but it also changed the activities of monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR). The findings reveal that Se has a positive effect on heat and/or osmotic stress mitigation mainly by regulating the ascorbate-glutathione cycle, especially in PEG-treated plants. Under the combined stress treatment, addition of 5 mu M of exogenous Se was most effective.Öğe Improvement of cold stress resistance via free radical scavenging ability and promoted water status and photosynthetic capacity of gallic acid in soybean leaves(SOC CHILENA CIENCIA SUELO, 2017) Yildiztugay, Evren; Ozfidan-Konakci, Ceyda; Kucukoduk, MustafaPlant polyphenols exhibit a wide variety of biological activities such as antimutagenicity, anticarcinogenicity and antioxidative activity. There is no report whether gallic acid (GLA), a naturally occurring plant phenol, is able to activate the plant defense system under cold stress. For this purpose, after soybean (Glycine max) was hydroponically grown for 3 weeks, seedlings were treated with gallic acid (GLA; 1 and 2 mM) and cold stress (5 oC and 10 degrees C) and GLA and stress combination for 72 h. The inhibition in growth, water content (RWC), osmotic potential (Psi II) and photosynthetic activity observed under stress and was more at the lowest temperature. Stress also elicited the accumulation of proline (Pro) only at 5 degrees C. While the capacity to maintain high growth, RWC,.. and photosynthetic efficiency was observed in GLA-treated plants under stress, Pro accumulation could not achieve with GLA plus stress. Any increase in total activities of superoxide dismutase (SOD) and catalase (CAT) induced by stress treatments determined. The lower cold stress caused an increase in the activities of ascorbate peroxidase (APX), glutathione reductase (GR) and NADPH oxidase (NOX). GLA treatment under stress (especially at 5 degrees C) could supply the increased activities of SOD, CAT, APX and GR. Also, exogenous GLA application to stress-treated plants increased the enzyme activities in ascorbate-glutathione cycle such as monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) and, contents of ascorbate (AsA) and glutathione. After GLA application under stress, it is observed reduction in hydrogen peroxide (H2O2) and the levels of lipid peroxidation (TBARS), and induction of hydroxyl radical (OH.) scavenging. Our results suggest that GLA is a potent inducer for induction of the scavenging activity of radicals as well as effectively usage of water status and photosynthetic capacity.Öğe Modulation of osmotic adjustment and antioxidant status in salt-stressed leaves of Thermopsis turcica(SPRINGER HEIDELBERG, 2014) Yildiztugay, Evren; Ozfidan-Konakci, Ceyda; Kucukoduk, MustafaThermopsis turcica is distributed naturally in saline soils. Interestingly, how T. turcica can live in harsh salt conditions is unknown. To study its defense responses under salinity, T. turcica was grown in a medium containing 100 and 200 mM NaCl for 7 and 14 days. Physiological parameters, ion contents, reactive oxygen species accumulation, activities of antioxidant enzymes/isozymes, NADPH oxidase enzyme/isozyme, lipid peroxidation (TBARS) and osmolyte contents were investigated. Stress caused a rapid decline in relative growth rate, relative water content and chlorophyll fluorescence (F (v)/F (m)) under both NaCl treatments. These traits were more suppressed at 200 mM NaCl. The decline in osmotic potential (I (I) ) with salinity increased the gradient for water flux into the cell and assisted in turgor maintenance. The increased membrane permeability under stress caused the entrance of excess Na+ and K+ into the cell. Stress decreased superoxide dismutase, catalase and peroxidase after 14 days of growth in 200 mM NaCl, whereas glutathione reductase (GR) increased throughout the experiment. While ascorbate peroxidase (APX) increased by 44 % at 7 days, it decreased after 14 days exposure to 200 mM NaCl. 200 mM NaCl caused the highest increase in TBARS at 14 days, indicating a decrease in OH center dot scavenging activity. Increasing concentrations of salinity caused an increase in glycine betaine (GB) and choline (Cho), though an increase in proline was only observed at 200 mM NaCl for 14 days. Briefly, H2O2 was more efficiently eliminated in 100 mM-treated plants by the ascorbate-glutathione cycle in which APX acts a strong catalyst together with GR. Also, Cho and GB help to maintain osmotic adjustment and cytoplasmic function.Öğe Profiling of rutin-mediated alleviation of cadmium-induced oxidative stress in Zygophyllum fabago(WILEY, 2015) Yildiztugay, Evren; Ozfidan-Konakci, CeydaZygophyllum fabago grows in arid, saline soil, or disturbed sites, such as former industrial or mining areas. This species is able to grow in coarse mineral substrates contaminated with heavy metals. To investigate the effects of the flavonoid rutin (Rtn) on certain heavy metal stress responses such as antioxidant defense systems and water status, seedlings were subjected to 100 and 200 M CdCl2 treatment without or with 0.25 and 1 mM Rtn for 7 and 14 d (days). Cd stress decreased growth (RGR), water content (RWC), leaf osmotic potential (), and chlorophyll fluorescence, all of which could be partly alleviated by addition of Rtn. Activities of superoxide dismutase, peroxidase (POX), ascorbate peroxidase, and glutathione reductase increased within the first 7 d after exposure to Cd. However, failure of antioxidant defense in the scavenging of reactive oxygen species (ROS) was evidenced by an abnormal rise in superoxide anion radical ( O2 center dot-) and hydrogen peroxide contents and a decline in hydroxyl radical (OH center dot) scavenging activity, resulting in enhancement of lipid peroxidation (TBARS) as a marker of Cd-induced oxidative stress. However, exogenously applied Rtn considerably improved the stress tolerance of plants via a reduction in Cd accumulation, modulation of POX activity, increase of proline (Pro) content, decrease in TBARS and ROS content and consequent lowering of oxidative damage of membrane. Overall, 0.25 and 1 mM Rtn could protect Z. fabago from the harmful effects of 100 M Cd-induced oxidative stress throughout the experiment. (c) 2014 Wiley Periodicals, Inc. Environ Toxicol 30: 816-835, 2015.Öğe Protective roles of exogenously applied gallic acid in Oryza sativa subjected to salt and osmotic stresses: effects on the total antioxidant capacity(SPRINGER, 2015) Ozfidan-Konakci, Ceyda; Yildiztugay, Evren; Kucukoduk, MustafaThe aim of our study was to examine whether exogenously applied with gallic acid (GA) enhances the tolerance of rice cultivars to polyethylene glycol (PEG)induced osmotic stress or salt (NaCl) stress. After two Oryza sativa L. cultivars, tolerant cultivar Pokkali and sensitive cultivar IR-28, were hydroponically-grown for 3 weeks, seedlings were treated with GA (0.75 and 1.5 mM), 120 mM NaCl and 20 % PEG-6000 producing the same osmotic potential (-0.5 MPa) and GA and stress combination for 72 h. PEG had greater reduction in growth rate (RGR) and water content (RWC) than that of NaCl in both cultivars. Salt and PEG decreased the maximum photochemical efficiency (F-v/F-m), the photochemical quenching coefficient (qP) and the actual quantum yield (Phi(PSII)), even more pronounced at NaCl in IR-28. Also, a notable increase in lipid peroxidation (TBARS) and hydrogen peroxide (H2O2) content was observed with PEG as compared to NaCl treatment. Activities of superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase in Pokkali and, catalase (CAT) and peroxidase (POX) in IR-28 were induced to a greater extent by PEG. The sensitivity of plants to stress was higher in IR-28 than in Pokkali. Also, comparing the injury between the NaCl and PEG stresses, it was greater under PEG-mediated osmotic stress. However, compared with the stress-treated plants alone, GA added to NaCl-stressed Pokkali significantly decreased H2O2 and TBARS contents, and enhanced the activities of SOD, CAT, POX and APX as well as increase of RGR, osmotic potential (Psi(Pi)), F-v/F-m and proline. In PEG-treated IR-28, GA strongly suppressed H2O2 and TBARS contents, up-regulated SOD and APX activities and increased RGR, RWC and Psi(Pi). It could be concluded that the both GA concentrations alleviated NaCl and PEG toxicity by increased the level of antioxidant activity and photosynthetic efficiency in rice.Öğe The role of antioxidant responses on the tolerance range of extreme halophyte Salsola crassa grown under toxic salt concentrations(ACADEMIC PRESS INC ELSEVIER SCIENCE, 2014) Yildiztugay, Evren; Ozfidan-Konakci, Ceyda; Kucukoduk, MustafaSalsola crassa (Amaranthaceae) is an annual halophytic species and naturally grows in arid soils that are toxic to most plants. In order to study the effects of salinity on their antioxidant system and to determine the tolerance range against salt stress, S. crassa seeds were grown with different concentrations of NaCl (0, 250, 500, 750, 1000, 1250 and 1500 mM) for short (15 d) and long-term (30 d). Results showed that growth (RGR), water content (RWC) and osmotic potential (Psi(Pi)) decreased and, proline content (Pro) increased at prolonged salt treatment. Unlike K+ and Ca2+ contents, S. crassa highly accumulated Na+ and Cl- contents. Chlorophyll fluorescence (F-v/F-m) only decreased in response to 1500 mM NaCl at 30 d. No salt stimulation of superoxide anion radical (O-2(center dot-)) content was observed in plants treated with the range of 0-500 mM NaCl during the experimental period. NaCl increased superoxide dismutase (SOD) activity depending on intensities of Mn-SOD and Fe-SOD isozymes except in 1500 mM NaCl-treated plants at 30 d. In contrast to catalase (CAT), peroxidase (POX) activity increased throughout the experiment. Also, salinity caused an increase in glutathione reductase (GR) and glutathione peroxidase (GPX) and decreased in ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) at 15 d. Both total ascorbate (tAsA) and glutathione (tGlut) contents significantly increased in treated plants with 1000-1500 mM NaCl at 15 d. After 0-1000 mM NaCl stress, H2O2 and TBARS contents were similar to control groups at 15 d, which were consistent with the increased antioxidant activity (PDX, GR and GPX). However, H2O2 content was more pronounced at 30 d. Therefore, S. crassa exhibited inductions in lipid peroxidation (TBARS content) in response to extreme salt concentrations. These results suggest that S. crassa is tolerant to salt-induced damage at short-term treatments as well as extreme salt concentrations. (C) 2014 Elsevier Inc. All rights reserved.Öğe Sphaerophysa kotschyana, an endemic species from Central Anatolia: antioxidant system responses under salt stress(SPRINGER JAPAN KK, 2013) Yildiztugay, Evren; Ozfidan-Konakci, Ceyda; Kucukoduk, MustafaSphaerophysa kotschyana is a Turkish endemic and endangered plant that grows near Salt Lake, in Konya, Turkey. However, little is known about the ability of this plant to generate/remove reactive oxygen species (ROS) or its adaptive biochemical responses to saline environments. After exposure of S. kotschyana to 0, 150, and 300 mM NaCl for 7 and 14 days, we investigated (1) the activities and isozyme compositions of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), peroxidase (POX), ascorbate peroxidase (APX), and glutathione reductase (GR); (2) the oxidative stress parameters NADPH oxidase (NOX) activity, lipid peroxidation (MDA), total ascorbate (tAsA) content, and total glutathione content (tGlut); and (3) ROS levels for superoxide anion radical (O (2) (center dot-) ), hydrogen peroxide (H2O2), hydroxyl radicals (OH center dot), and histochemical staining of O (2) (center dot-) and H2O2. H2O2 content increased after 14 days of salt stress, which was consistent with the results from histochemical staining and NOX activity measurements. In contrast, oxidative stress induced by 150 mM NaCl was more efficiently prevented, as indicated by low malondialdehyde (MDA) levels and especially at 7 days, by increased levels of SOD, POX, APX, and GR. However, at 300 mM NaCl, decreased levels of protective enzymes such as SOD, CAT, POX, and GR, particularly with long-term stress (14 days), resulted in limited ROS scavenging activity and increased MDA levels. Moreover, at 300 mM NaCl, the high H2O2 content caused oxidative damage rather than inducing protective responses against H2O2. These results suggest that S. kotschyana is potentially tolerant to salt-induced damage only at low salt concentrations.Öğe Upregulation of antioxidant enzymes by exogenous gallic acid contributes to the amelioration in Oryza sativa roots exposed to salt and osmotic stress(SPRINGER HEIDELBERG, 2015) Ozfidan-Konakci, Ceyda; Yildiztugay, Evren; Kucukoduk, MustafaThe aim of this study is to elucidate the influence of the exogenous application of gallic acid (GLA) in alleviating the detrimental effects of salinity (NaCl), osmotic stress (polyethylene glycol; PEG), and their combination in Oryza sativa L. roots. To produce same osmotic potential (-0.5 MPa), 3-week-old rice seedlings were treated with 120 mM NaCl and/or 20 % PEG6000 with/without GLA (0.75 and 1.5 mM) treatments for 72 h. Both alone and combination of stresses decreased growth (RGR) and osmotic potential (I (I) ). Moreover, stress caused a significant increase in proline (Pro) and hydrogen peroxide (H2O2) contents. Also, Pokkali and IR-28 had higher H2O2-scavenging enzyme activities including catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) activities in NaCl-treated roots. Only CAT activity was induced in both cultivars with PEG. Therefore, the enhanced levels of lipid peroxidation (thiobarbituric acid reactive substances (TBARS)) were more pronounced under PEG than NaCl. However, GLA significantly mitigated NaCl and/or PEG-induced stress injury. Under salinity, TBARS was lesser in GLA-applied rice that was associated with greater activities of superoxide dismutase (SOD), peroxidase (POX), and APX. GLA in the presence of PEG improved the activities of CAT and POX. According to these findings, GLA alleviated the damaging effects of NaCl and/or PEG (especially under NaCl) by improving the antioxidative system in rice. This is the first study elucidating the effects of GLA on tolerance to salinity, osmotic stress, and their combination in plants.Öğe Variations in osmotic adjustment and water relations of Sphaerophysa kotschyana: Glycine betaine, proline and choline accumulation in response to salinity(SPRINGEROPEN, 2014) Yildiztugay, Evren; Ozfidan-Konakci, Ceyda; Kucukoduk, Mustafa; Duran, YagmurBackground: Sphaerophysa kotschyana Boiss. is naturally distributed in overly salty regions. The key to the completion of the life cycles of S. kotschyana in harsh saline soils may be hidden in changes of its osmo-protectants, but there is currently no information about the interaction between osmotic adjustment and water relations in adaptation to saline conditions. The aim of this article was to determine growth, relative growth rate (RGR), relative water content (RWC), osmotic potential (psi(Pi)), photosynthetic efficiency (F-v/F-m), thiobarbituric acid-reactive substances (TBARS) and osmo-protectant contents [proline (Pro), choline (Cho) and glycine betaine (GB)] in S. kotschyana leaves and roots exposed to 0, 150 or 300 mM NaCl for 7 and 14 d (days). Results: The results clearly showed that the reductions in growth, RWC, F-v/F-m, RGR and psi(Pi) were more pronounced at 300 mM, especially after 14 d. In the same group, the highest increase in TBARS was recorded in roots (126%) and leaves (31%). The induction at 150 mM was not as high. Therefore, roots appear to be the most vulnerable part of this plant. Moreover, S. kotschyana was able to withstand short-term low salinity. Conclusions: The osmo-protectant accumulation in S. kotschyana as a salinity acclimation or adaptation was sufficient for toleration of low salt concentration (150 mM). In contrast, the plants exposed to the highest NaCl concentration (300 mM) were not able to maintain the ability to prevent water loss because of further decrease in root/shoot ratio of fresh weight (FW) and dry weight (DW), RWC and RGR.
