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The effect of 24-epibrassinolide on selected parameters of maize and faba bean genotypes varying in drought sensitivity
Řehořová, Kateřina ; Kočová, Marie (advisor) ; Hniličková, Helena (referee)
Brassinosteroids are plant hormones which are also known for their pleiotropic effects on plants exposed to various biotic and abiotic stress factors. The aim of this study was to evaluate the role of 10-8 M 24-epibrassinolide in Zea mays L. and Vicia faba L., grown under conditions of drought stress (6, 10, 14, 18 days) with an emphasis on different answer to their drought sensitive and resistant genotypes. Net photosynthetic rate (PN) and transpiration rate (E), stomatal conductance (gs), osmotic potential (ψs), proline (Pro) and malondialdehyde (MDA) content and membrane injury index (MI) were measured in stressed plants and plants grown under controlled conditions. The most important factor influencing these parameters was drought, which led to a gradual decrease of PN, E, gs, ψs and increase of Pro, MDA a MI. The effect of 24-epibrassinolid was significant rather exceptionally and in these cases, more pronounced response was observed in drought stressed plants compared with plants grown under controlled conditions. Plants showed intraspecific variability in their reactions, which in sensitive and tolerant genotypes were not clear and differed depending on the studied parameters and conditions of plant cultivation.
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Antioxidant enzymes response to abiotic stress. Impact of decreased cytokinin level.
Lubovská, Zuzana ; Wilhelmová, Naďa (advisor) ; Prášil, Ilja (referee) ; Kočová, Marie (referee)
Charles University in Prague, Faculty of Science Department of Experimetnal Plant Biology Ph.D. study program: Plant physiology and anatomy Abstract Antioxidant enzymes response to abiotic stress. Impact of decreased cytokinin level. Zuzana Lubovská Supervisor: RNDr. Naďa Wilhelmová, CSc. Supervisor-consultant: RNDr. Helena Štorchová, CSc. Praha, 2015 The response of the antioxidant enzyme system to drought, heat and a combination of these stresses was followed in tobacco plants overexpressing cytokinin oxidase/dehydrogenase1 (CKX1) under the root-specific WRKY6 promoter (W6:CKX1 plants) and under the constitutive 35S promoter (35S:CKX1 plants) and in the corresponding wild type (WT). CKX1 over-producing lines developed a bigger root system, which contributed to their stress tolerance. The high stress tolerance of 35S:CKX1 plants was also associated with a dwarf shoot phenotype and changed leaf morphology. The genes for chloroplastic antioxidant enzymes, stroma ascorbate peroxidase (sAPX), thylakoid ascorbate peroxidase (tAPX) and chloroplastic superoxide dismutase (FeSOD), which are responsible for scavenging of reactive oxygen species produced via electron transfer during photosynthesis, were all strongly transcribed in control conditions. All the tested stresses down-regulated expression of these genes...
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Analysis of antioxidant systems, morphological and physiological parameters in two faba bean (Vicia faba L.) cultivars during drought stress
Jelénková, Iva ; Kočová, Marie (advisor) ; Wilhelmová, Naďa (referee)
Knowledge of physiological and morfological mechanisms which are related to drought tolerance is essential in breeding high-yielding and tolerant plants, which would not suffer unfavourable environmental conditions. Drought stress can lead to oxidative damage which causes serious disorders in physiological and biochemical processes in plant cells. Antioxidants can reduce those negative effects. Morphological (dry mass of shoot and roots, height of shoot, number of leaves), physiological (photosynthetic efficiency, pigment content, relative water content-RWC) and antioxidative (catalase-CAT, ascorbate peroxidase-APX, proline) parameters were evaluated in this study using two genotypes of Vicia faba L. differing in drought susceptibility. Drought resistant (Merkur) and sensitive (Piešťanský) genotypes were exposed to 10 days of drought. Activity of CAT and APX of stressed plants rather decreased. Proline content oscillated and no evident trend or significant differences were observed in relation to drought stress. Decrease in RWC was expressed more at susceptible plants, electron-transport chain activity and pigment content were not affected much by drought. Drought susceptible genotype expressed more serious negative effects of drought in morphological parameters, however this genotype was a bit bigger than...
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Photosynthetic parameters as secondary selection traits during plant breeding for salt stress tolerance
Hlavatá, Věra ; Kočová, Marie (advisor) ; Lhotáková, Zuzana (referee)
High salt concentration is important abiotic stress factor that negatively affect plant growth and development and finally also their yield. Increase of plant tolerance to this stress factor is thus one of the most important goals in breeding programmes, particularly in areas with saline environment. Various physiological traits have been suggested for the testing of plant tolerance to improved salinity. Photosynthetic parameters play undoubtedly the main role, because of their rapid response to stress conditions. Generally, photosynthetic rate, chlorophyll content and chlorophyll fluorescence belong to the photosynthetic parameters, that are usually recommended for the evaluation of stress tolerance. All of them were also used for study of salt tolerance in crop plants. The advantages of these measurements are rapidity, non-invasive techniques and particularly, the possibility to test wide collection of genotypes during the short period. Although some of the parameters were recommended for the evaluation of stress tolerance, the results are still ambiguous. The aim of this study was to briefly describe the changes of selected photosynthetic parameters of different plant species in consequence of salt stress and assess the usefulness of these parameters for reliable screening for salt tolerance.
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Intraspecific variability in plant antioxidant systems and its impact on drought tolerance
Jelénková, Iva ; Kočová, Marie (advisor) ; Zelenková, Sylva (referee)
Drought is one of the major factors limiting agricultural production. Reactive oxygen species (eg. superoxide radical, hydroxyl radical, hydrogen peroxide) generated during stress in plant cells activate antioxidant mechanisms, which scavenge those toxic substances. The positive correlation between activity of enzymatic (eg. catalase, superoxide dismutase, glutathione reductase, peroxidases) and nonenzymatic (eg. glutathione, ascorbic acid) antioxidants and stress tolerance was confirmed in various studies. Both interspecific and intraspecific variability was found in activities of antioxidant systems of plants. Higher activity was also observed in F1 generation in relation to positive heterosis, or in plants treated with supportive substances such as abscisic acid, brassinosteroids and nitrogen. The increase in the activity of antioxidants was also proved in relation to the ploidy level or to intensity of drought. It was observed the positive effect of previous drought exposition on tolerance to other abiotic stressors. The complex response of plants to stress factors depends on many other internal and external factors.
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Srovnání C3 a C4 plodin z hlediska tolerance k salinitnímu a vodnímu stresu
Kholová, Jana ; Kočová, Marie (advisor) ; Pospíšilová, Jana (referee) ; Prášil, Ilja (referee)
The main objective of the thesis work was the detailed characterization of pearl millet (Pennisetum glaucum (L.) R. Br.) genotypes contrasting for terminal drought tolerance. For that work, we used a set of near isogenic lines (NIL-QTLs; carrying terminal drought tolerance quantitative trait locus (QTL) from a drougth tolerant donor parent on the genetic background of a sensitive parent) and a recombinant inbred lines population (RIL; developed from a cross between the tolerant and sensitive genotype). In these contrasting genotypes we investigated following physiological traits. Transpiration rate (Tr), transpiration efficiency (TE), transpiration response to increased vapor pressure deficit, threshold in volumetric soil moisture where transpiration begins to decline (FTSW threshold), stomatal density (SD), sensitivity of plants' growth to VPD below and above 2kPa. Regarding biochemical traits, we followed content of chlorophyll (Chl), carotenoids (Car), abscisic acid (ABA), proline (Pro), we conducted isozyme analysis of antioxidative enzymes [superoxid dismutase (SOD), ascorbic peroxidase (APX), catalase (CAT)]. The main leading thread for understanding the drought tolerance mechanisms of pearl millet came from the analysis of traits related to the control of water losses under fully irrigated...
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