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Analysis of selected parameters inbred and hybrid maize stressed by flooding
Čečetka, Petr ; Kočová, Marie (advisor) ; Hnilička, František (referee)
Flooding is an important stress factor that influences the growth of plants and their production. Anthropogenic activity is causing gradual changes in the climate, consequently triggering changes in the distribution of precipitation. This leads to the conditions alternating between optimal, draughts, and excessive flooding that the plants have to cope with. The aim of my diploma thesis was to evaluate the consequences of flooding and the subsequent restoration of normal cultivating conditions of two inbred lines of maize (Zea mays L.) (2023 and CE704) and their reciprocal hybrids (2023xCE704, CE704x2023) that were exposed to the stress of flooding and subsequent restoration during several phases of their ontogenetic growth. For both the plants exposed to flooding and the subsequent restoration and the plants grown in optimal conditions only, there were several morphologic and physiological parameters, parameters related to the water status, and parameters that determine the extent of the damage done to the cellular structure or characterize the defense mechanisms employed by the plant in reaction to the stress. Flooding of the plants often led to an increase in their transpiration speed, stomatal conductivity, MDA and H2O2 contents, and catalase activity. For other parameters, the flooding usually...
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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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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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Response of maize lines and hybrids to hypoxia stress depending on plant development
Čečetka, Petr ; Kočová, Marie (advisor) ; Hniličková, Helena (referee)
Flooding-induced hypoxia is one of the significant abiotic stress factors that influence the development of plants. The ongoing climate change leads to changes in the distribution of precipitation, causing excessive droughts followed by torrential rains and, consequently, flooding. Inappropriate agronomic practices and the choice and rotation of the cultivated crops also greatly influence the duration of the drought or flooding. The plants must either be able to adapt to these conditions, or the agricultural production must only select suitable genotypes that are tolerant of these conditions. The aim of this thesis was the comparison of the reaction of 4 genotypes (2023, CE704, 2023xCE704 and CE704x2023) of maize (Zea mays L.) grown in flood conditions to which they were exposed at different stages of their ontogenic development, as compared to plants grown under optimal water supply conditions. Various parameters showing the general condition and significant functions of the plants (morphological parameters, plant-water relations parameters, photosynthetic parameters, and cell damage parameters) were measured. Among the plants exposed to flooding, the reactions differed greatly based on the age of the plants. Younger plants showed an increase in transpiration speed values, stomatal conductivity,...
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Analysis of selected parameters inbred and hybrid maize stressed by flooding
Čečetka, Petr ; Kočová, Marie (advisor) ; Hnilička, František (referee)
Flooding is an important stress factor that influences the growth of plants and their production. Anthropogenic activity is causing gradual changes in the climate, consequently triggering changes in the distribution of precipitation. This leads to the conditions alternating between optimal, draughts, and excessive flooding that the plants have to cope with. The aim of my diploma thesis was to evaluate the consequences of flooding and the subsequent restoration of normal cultivating conditions of two inbred lines of maize (Zea mays L.) (2023 and CE704) and their reciprocal hybrids (2023xCE704, CE704x2023) that were exposed to the stress of flooding and subsequent restoration during several phases of their ontogenetic growth. For both the plants exposed to flooding and the subsequent restoration and the plants grown in optimal conditions only, there were several morphologic and physiological parameters, parameters related to the water status, and parameters that determine the extent of the damage done to the cellular structure or characterize the defense mechanisms employed by the plant in reaction to the stress. Flooding of the plants often led to an increase in their transpiration speed, stomatal conductivity, MDA and H2O2 contents, and catalase activity. For other parameters, the flooding usually...
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