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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 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.Öğe Secondary metabolites: Tools for stress protection in plants(Elsevier Science Inc, 2007) Velikova, V.; Edreva, A.; Tsonev, T.; Gesheva, E.; Dagnon, S.; Loreto, F.; Guerel, A.; Jones, H.