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Öğe Bioreactor systems for large scale micropropagation for fruit tree rootstocks(Elsevier Science Bv, 2012) Fedakar, S. Orhan; Bayraktar, M.; Gurel, A.Öğe Direct plant regeneration from different explants through micropropagation and determination of secondary metabolites in the critically endangered endemic Rhaponticoides mykalea(Taylor & Francis Ltd, 2017) Hayta, S.; Bayraktar, M.; Erel, S. Baykan; Gurel, A.Direct plant regeneration from different explants, micropropagation and determination of secondary metabolites were studied in the critically endangered endemic Rhaponticoides mykalea (Hub.-Mor.) M.V. Agab & Greuter. Seed germination was achieved by damaging the seed coat and cultivating the embryos on Woody Plant Medium (WPM), of which 40% germinated. The epicotyls and cotyledonary petioles of seedlings were used as initial explants and direct shoot regeneration was obtained on WPM containing 2.22M 6-benzyladenine (BA). WPM medium supplemented with 2.22M BA and 4.92M indole-3-butyric acid (IBA) significantly improved the production of multiple shoots, resulting in an average of 5.6 shoots per explants. The highest rooting of shoots (35.6%) was observed with WPM medium containing 19.68M IBA with 990M putrescine. Plantlets with well-developed roots were transferred to soil and acclimatised within a plant growth chamber. Acclimatised plants showed 100% survival rate and remained healthy. As a part of our study, the content of secondary metabolites in three tissue culture regenerated lines were determined by HPLC analysis. Chlorogenic acid, Quercetin and scutellarin were confirmed secondary metabolites of R. mykalea.Öğe Drought Tolerance in Cotton: Involvement of Non-enzymatic ROS-Scavenging Compounds(Wiley, 2009) Yildiz-Aktas, L.; Dagnon, S.; Gurel, A.; Gesheva, E.; Edreva, A.Compounds with reactive oxygen species (ROS)-scavenging ability were studied. High-performance liquid chromatography (HPLC) pattern of polyphenols, contents of proline and carotenoids, and antiradical (AR) capacity were determined. The malonyldialdehyde (MDA) level was also assessed. Tolerant and sensitive cotton genotypes were compared, grown in the Aegean region of Turkey at normal (field capacity) and limited (1/3 field capacity) water supply. Chlorogenic acid isomers and flavonoids were identified in HPLC pattern of polyphenols. At normal water supply, the tolerant genotype was distinguished by a higher content of all polyphenol types, higher proline, carotenoids and AR capacity and lower MDA level compared with the sensitive genotype. In plants subjected to water deficit, a decline of all polyphenol compounds, carotenoids and AR capacity was observed. However, this response was less pronounced in the tolerant than in the sensitive genotype, i.e. despite the stress conditions imposed, the tolerant plants maintained a more effective defence system. The data are corroborated by the weaker structural membrane damage in the drought-exposed tolerant vs. sensitive genotype, according to the MDA test. Hence, diverse chemical types are involved in the non-enzymatic ROS-scavenging system of cotton plants and can be related to the drought tolerance of this important crop.Öğe Drought Tolerance in Cotton: Involvement of Non-enzymatic ROS-Scavenging Compounds(Wiley, 2009) Yildiz-Aktas, L.; Dagnon, S.; Gurel, A.; Gesheva, E.; Edreva, A.Compounds with reactive oxygen species (ROS)-scavenging ability were studied. High-performance liquid chromatography (HPLC) pattern of polyphenols, contents of proline and carotenoids, and antiradical (AR) capacity were determined. The malonyldialdehyde (MDA) level was also assessed. Tolerant and sensitive cotton genotypes were compared, grown in the Aegean region of Turkey at normal (field capacity) and limited (1/3 field capacity) water supply. Chlorogenic acid isomers and flavonoids were identified in HPLC pattern of polyphenols. At normal water supply, the tolerant genotype was distinguished by a higher content of all polyphenol types, higher proline, carotenoids and AR capacity and lower MDA level compared with the sensitive genotype. In plants subjected to water deficit, a decline of all polyphenol compounds, carotenoids and AR capacity was observed. However, this response was less pronounced in the tolerant than in the sensitive genotype, i.e. despite the stress conditions imposed, the tolerant plants maintained a more effective defence system. The data are corroborated by the weaker structural membrane damage in the drought-exposed tolerant vs. sensitive genotype, according to the MDA test. Hence, diverse chemical types are involved in the non-enzymatic ROS-scavenging system of cotton plants and can be related to the drought tolerance of this important crop.Öğe Effect of water deficit and potassium fertilization on photosynthetic activity in cotton plants(Taylor & Francis Ltd, 2011) Tsonev, T.; Velikova, V.; Yildiz-Aktas, L.; Gurel, A.; Edreva, A.Physiological mechanisms that can contribute to drought tolerance and the role of potassium fertilization in cotton were studied by evaluation of parameters describing photosynthetic performance. Gas-exchange and chlorophyll fluorescence characteristics were measured on leaves of two cotton genotypes, one drought sensitive (Nazilli 84-S) and the other drought tolerant (Sahin 2000), grown in field conditions in the Aegean region of Turkey under different regimes of water and potassium supply. It was shown that under drought conditions without potassium fertilization Sahin 2000 had a higher photosynthetic rate and stomatal conductance than Nazilli 84-S. Potassium fertilization to a great extent compensated for the inhibitory effect of drought on photosynthesis. Application of the JIP test by using chlorophyll fluorescence data revealed that the drought sensitive Nazilli 84-S was more responsive to potassium fertilization than Sahin 2000, as judged by a number of parameters representing quantum efficiency of the processes and energy fluxes in photosystem (PS) II. The observed decrease in photosynthetic CO2 assimilation in both cotton cultivars under drought conditions was not accompanied by any significant decrease in the electron transport flux in PSII and maximum quantum yield of primary photochemistry.Öğe Growth and antioxidant defence in hypocotyl-derived calli of two cotton cultivars with contrasting salt tolerance(Springer Science and Business Media B.V., 2023) Sacu, M.; Aktas, L.Y.; Bayraktar, M.; Gurel, A.Soil salinity is one of the major abiotic stress factors that limits cotton (Gossypium hirsutum L.) production worldwide. Although cotton is categorised as a salt-tolerant plant, its tolerance level can vary depending on the cultivar. The present study aimed to evaluate the growth and biochemical responses of two cotton cultivars (Carmen and NM-503) to salt stress under tissue culture conditions by using an in vitro selection technique. Hypocotyl explants were cultured on callus formation medium (full-strength MS (Murashige and Skoog medium) macro- and micro-salts + B5 (Gamborg medium) vitamins + 0.1 mg/L 2,4-D (2,4-dichlorophenoxyacetic acid) + 0.5 mg/L kinetin) containing 0, 100, 200 or 400 mM NaCl for 4 weeks. Compared to Carmen cultivar, NM-503 cultivar showed an improved growth performance under non-stress control conditions; however, both cultivars showed similar growth and browning tendencies when exposed to salinity stress. Although both cultivars showed a significant decrease in biomass accumulation and relative growth rate following treatment with 200 and 400 mM NaCl, they were tolerant to NaCl stress up to 200 mM in terms of callus survival rate. Carmen cultivar showed the lowest photosynthetic pigment content after treatment with 400 mM NaCl; however, both cultivars showed no significant differences in the photosynthetic pigment content between NaCl concentrations. Furthermore, in contrast to Carmen cultivar, NM-503 cultivar did not accumulate proline in response to 200 and 400 mM NaCl treatment. Under salinity stress, NM-503 cultivar exhibited lower lipid peroxidation level than Carmen cultivar. Both cultivars showed no significant differences in superoxide dismutase activity in control and NaCl-treated groups, except for the 400 mM NaCl-treated group in Carmen cultivar. Apart from constitutive enzyme activity, both cultivars showed similar catalase activities at all concentrations of NaCl treatment. In both cultivars, peroxidase and ascorbate peroxidase activities increased in response to an increase in NaCl concentrations. While glutathione reductase activity gradually increased in NM-503 cultivar in response to NaCl treatment, it gradually decreased in Carmen cultivar. In conclusion, both cultivars showed similar growth response under salinity stress, and this growth response was significantly restricted by 200 and 400 mM NaCl treatment. Among all studied parameters, the most distinct response of the cultivars to salinity stress was reflected by the lipid peroxidation level, which indicates the differences in the mechanism of cellular antioxidant protection between the cultivars. Despite the absence of a salt exclusion mechanism used by intact plants, the high level of resilience shown by the calli of NM-503 cultivar against severe salt stress conditions may be attributed to its effective cellular antioxidant defence mechanism. © 2023, The Author(s), under exclusive licence to Springer Nature B.V.Öğe Reddening of cotton (Gossypium hirsutum L.) leaves: analysis of the polyphenol complex(Ist Chimica Agraria, 2006) Edreva, A.; Dagnon, S.; Gurel, A.; Gesheva, E.; Hakerlerler, H.The polyphenol complex of cotton leaves, expressing an abnormal red coloration under abiotic stress, was analysed by using high performance liquid chromatography (HPLQ. Different polyphenol types - cinnamic acid derivatives (C-6-C-3), flavonoids (C-6-C-3-C-6) and anthocyanins (C-6-C-3-C-6(+)) were separated. It was shown that reddening of cotton leaves was related to an increased formation of anthocyanin pigments, mainly cyanidin glycosides, while cinnamic acid derivatives and flavonoids were not significantly changed. The plausible protective role of anthocyanins is discussed, particularly taking into account the shift from malvidin to cyanidin aglycones, i.e. to o-dihydroxy substitution in the B-ring of the anthocyanins during cotton leaf reddening that may determine a higher antioxidant and antiradical capacity.
