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Mechanisms of extreme drought tolerance in resurrection plants
Termanini, Sebastian ; Lipavská, Helena (advisor) ; Lhotáková, Zuzana (referee)
Drought is one of the abiotic stresses that plants have to fight with from the beginning of their transition to land. However, there is a systematically incoherent group of plants that can solve extreme water scarcityand still effectivelyprosper. A high degree of dehydration involves a number of problems including osmotic stress, the accumulation of reactive oxygen species (ROS), or protein degradation. However, drought-tolerant plants have evolved mechanisms to deal with these problems. For protection against ROS they activate antioxidant enzymes and accumulate non-enzymatic antioxidants, which can quench ROS. These plants use a wide spectrum of amino acids and carbohydrates against the osmotic stresses, ranging from the ubiquitous and abundant carbohydrates like sucrose, till the trehalose scarce in plants. None of the plants relies on a single substance, instead, plants depend on species-specific cocktails of protective agents, through which they acquire their tolerance. The studies of those plants and their mechanisms of tolerance seem to be a perspective way for selection of preferable target genes suitable for the development of crops tolerant to desiccation. Key words: antioxidant systems, dehydration, drought, LEA, octulose, polyols, RFO, resurrection plants, sucrose, trehalose
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Increasing plant drought resistance by priming methods: the role of antioxidant capacity changes
Popelářová, Anna ; Lipavská, Helena (advisor) ; Lhotáková, Zuzana (referee)
When there is a lack of water in the soil, the plant is subject to stress during which reactive oxygen species (ROS) are formed and the water content in the tissues decreases. ROS cause oxidative damage, which the plant tries to prevent by antioxidation systems action. The osmotic adjustment process ensures water maintenance in the plant. Priming can be thought of as a treatment of plants aimed at increasing stress resistance. This thesis is mainly focused on summarizing information related to priming in connection with drought tolerance improvement and related changes in the activities and amount of antioxidation systems and osmolytes. So far, seed priming methods are probably the most explored, these include hydropriming, osmopriming and priming with elicitors. Priming in the vegetative phase of growth is mainly associated with the application of elicitors. Transgenerational priming has an impact on the progeny of treated plants. Priming-induced changes are species-specific and in some cases may affect the plants for a longer period.
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Orchids as a model for research in ecophysiological adaptations of mycoheterotropic plants
Ponert, Jan ; Lipavská, Helena (advisor) ; Gryndler, Milan (referee) ; Chrtek, Jindřich (referee)
Perhaps all orchids are mycotrophic at early developmental stages, while majority of species photosynthesize at adulthood and only about 200 species remain fully mycotrophic for the whole life. Mycotrophy affects orchids at many levels. In this thesis, I focus on four aspects of orchid biology, which could be connected with mycotrophy: (i) systematics, (ii) genome size and endoreduplication, (iii) regulation of seed germination and (iv) mechanism of transfer of carbon and energy from fungi to orchids. There are over 27,000 recently recognized orchid species, nevertheless new ones are still discovering and old ones are revisiting. In this work I present a description of new species, Cleisostoma yersinii, and its morphological, anatomical, ecological and systematic characterization. Phylogeny reconstruction confirmed relationship with C. birmanicum. In the subtribe Podochileae, I reappraised the genus Campanulorchis to establish monophyletic but also morphologically defined group. For both abovementioned genera I prepared the artificial identification key. In the genus Dactylorhiza I revised taxa present in our country and I prepared an identification key which firstly mentions D. maculata subsp. elodes from Czech Republic. Orchid species diversity is probably reflected in genome structure. Results...
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Regulation of morphogenic processes in potato - the role of sugar metabolism
Ševčíková, Hana ; Lipavská, Helena (advisor) ; Navrátil, Oldřich (referee) ; Langhansová, Lenka (referee)
Potato (Solanum tuberosum) tuberization is a complex, strictly regulated morphogenic process. Since potato is one of the most important crops in the world, understanding the regulation of this process is gaining in importance not only from a theoretical but also from a practical point of view. This work focuses on the role of sugars, which can serve not only as an energy and building material sources, but also as an important signal regulating many developmental processes including the tuberization. As a primary experimental material potato cv. Lada (WT) and its spontaneously tuberizing (ST) mutant was used. Since the previous results with ST plants suggested altered carbohydrate partitioning between plant organs and significant difference in total carbohydrate contents between ST plants and the WT (Fischer et al. 2008), in the first manuscript presented, the aim was to examine in detail the sugar metabolism of ST plants grown in vitro mixotrophically (MT) and photoautotrophically (PA). We observed changes in soluble carbohydrate allocation and starch deposition, favouring basal stem part in ST. Even thought, gibberellins (GAs) are considered to be the main tuberization inhibitors, ST potato plants had surprisingly high GAs levels. The determination of tuber-inducing marker gene expressions...
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Role of carbohydrate metabolism in defence against oxidative stress induced by arsenic
Kofroňová, Monika ; Lipavská, Helena (advisor) ; Száková, Jiřina (referee) ; Kovalíková, Zuzana (referee)
Heavy metal contamination significantly reduces crop yields, causing serious problems in agriculture and having a major impact on human health if these contaminants enter the food chain. Understanding the mechanisms of plant responses could help to increase their resistance to heavy metals as well as their potential use in phytoremediation. Carbohydrates play an important role in plant growth and development as well as in defense reactions. This work summarizes the results of four publications focused on the effects of arsenic and thorium on antioxidant mechanisms in tobacco plants and horseradish root crops. Attention is paid, among other things, to the dynamics of sugar contents, which are potentially important molecules involved in the fight against oxidative stress. The first publication summarizes arsenic effects on plant physiological parameters, focusing on arsenic tolerance-enhancing mechanisms as well as summarizing the ability of plants to cope with arsenic-induced oxidative and nitrosative stress. Emphasis was placed on, among other things, a topic that was unjustly neglected in previous publications - i.e. carbohydrate metabolism. Further work was already experimental and dealt with the study of arsenic as a trigger of oxidative stress in the root culture of horseradish and...
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Physiological responses of woody species to urban environment
Petrouová, Lenka ; Lhotáková, Zuzana (advisor) ; Lipavská, Helena (referee)
Trees are an important functional element in urban ecosystems. The urban environment has a number of abiotic stress factors for trees and their interactions are based on the overall physiological condition of the trees. Abiotic stress factors include air pollution, space constraints, reduced water availability, increased temperature, and precipitation. In addition to abiotic factors, trees in the city face stressful conditions brought on by climate change, which are increasing in severity and have a measurable impacts on urban tree growth. Climate change is manifested mainly by elevated air temperatures, changes in quantity and distribution of precipitation, and increased concentrations of carbon dioxide in the atmosphere. This bachelor's thesis is focused on the responses of selected woody species in urban environments and their adaptive abilities in the context of changing climatic conditions. Growth is the main observable response of woody species to environmental changes. In particular, increased growth has been recorded in relation to rising temperature and carbon dioxide levels. Specific differences between woody species in functional parameters can be utilized to improve quality of life in human environments Trees are highly valuable in urban ecosystems and perform a range of functions,...
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