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Phenotypic plasticity and morphogenesis of desmids (Desmidiales, Zygnematophyceae)
Figallová, Klára ; Neustupa, Jiří (advisor) ; Ráček, Jan (referee)
Desmids are green streptophyte algae classified in the order of Desmidiales. The cells of desmids are notable for the presence of mirror-symmetrical ornamented semicells connected by a plasmatic bridge, the isthmus. This group of organisms is characterised by a rather high ecological specificity, causing them to respond to changes in environmental conditions by modifying their morphological characteristics. The ability of an organism to exhibit several different phenotypes in response to environmental transformations is called phenotypic plasticity. This has often been the subject of morphometric studies, which provide more specific description of the phenotypic changes in desmids. Due to their ability to respond to alterations in external conditions, desmids have shown the potential for practical use as bioindicators.
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Streptophytic Algae with a Focus on the Class Zygnematophyceae
Špička, Jan ; Soldán, Zdeněk (advisor) ; Ráček, Jan (referee)
This bachelor's thesis deals with streptophyte algae, with special attention given to the class Zygnematophyceae. The thesis is written as a literature review, aiming to summarize existing knowledge about streptophyte algae, particularly focusing on the class Zygnematophyceae. Additionally, the thesis elucidates the phylogenetic relationships within this group, which historically have been challenging. The thesis primarily focuses on the description, ecology, and taxonomy of streptophyte lineages, emphasizing their significance in the study of terrestrialization, or the colonization of land. A significant part of this thesis is therefore to highlight the ecological and evolutionary role of streptophyte algae, especially in the context of their adaptation to terrestrial environments. An additional aim of the thesis is to address the issues associated with the group of algae, given their inconsistent definition. The thesis points out that algae do not form a monophyletic group, as they encompass various taxonomic lineages. This thesis can serve as a foundation for further research in the field of algology, thereby contributing to a better understanding and orientation in the process of terrestrialization. It also indicates the need for more phylogenetic studies to enhance understanding of the...
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Photosynthetically produced hydrogen
Osipenko, Elena ; Němcová, Yvonne (advisor) ; Ráček, Jan (referee)
Bio-hydrogen from microalgae and cyanobacteria has attracted commercial awareness due to its potential as an alternative, reliable and renewable energy source. Photosynthetic hydrogen production from algae and cyanobacteria can be interesting and promising options for clean energy, because hydrogen is produced at ambient temperature and pressure and releases only water as a by-product. The energy of sunlight is used to split the water molecule into protons (H+), electrons (e-) and O2. The protons and electrons are then recombined with the help of the enzymes hydrogenase or nitrogenase (in the case of cyanobacteria) to form H2. Both of these enzymes are sensitive to O2 and therefore require the processes of H2 formation and CO2 fixation to be separated. This bachelor's thesis aims to describe the principle of H2 formation in different cyanobacterial and algal systems and mention the problems and limitations. The thesis also presents recent approaches, including genetic and metabolic engineering of cyanobacteria and algae or co-culturing of algae and bacteria, where an anaerobic environment is created by enhanced bacterial respiration.
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Accumulation of phenolic compounds in Spirogyra in stress conditions
Ráček, Jan ; Pichrtová, Martina (advisor) ; Procházková, Lenka (referee)
Phenolic substances represent one of the major groups of secondary metabolites of higher plants that play a role in a number of biotic and abiotic interactions. Among algal groups, these substances are produced, for example, by conjugating algae (Zygnematophyceae), which are currently considered to be the closest living relatives of higher plants. The common function of phenolic substances is protection against the harmful effects of ultraviolet radiation, or even an excessive amount of photosynthetically active radiation, which was supported by the induction of their synthesis after exposure to UV radiation in several ecophysiological studies. However, the range of applied stress factors and their effect on changes in phenol levels is limited. In this diploma thesis, the genus Spirogyra, for which the chemical structure of a number of specific phenolic substances is known, was exposed to selected stress factors and their influence on cell morphology, maximum quantum yield Fv/Fm and quantity of phenolic substances was monitored. A significant increase was observed after application of UV-B radiation, higher level of PAR, low temperature and osmotic stress, while at high temperature this effect was not evident. Increased production upon UV-B exposure further underlines the importance of phenolic...
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Phenolic substances in algae
Ráček, Jan ; Pichrtová, Martina (advisor) ; Pilátová, Jana (referee)
Phenolic substances are considered to be a group of secondary metabolites, known primarily from land plants (Embryophyta). Their function is to absorb harmful ultraviolet radiation, to protect plants from grazing and to attract pollinators and seed spreaders. However, these compounds have also been reported in some phylogenetically unrelated algal groups, the most important of which are brown algae (Phaeophyceae), siphonous green algae from the Dasycladaceae family and conjugating algae (Zygnematophyceae). The aim of this work is to summarize the current knowledge about phenolic compounds of these groups with an emphasis on their significance for the biology of the species. The first part describes phenolic compounds in general and also outlines the way they are biosynthesized. The next chapters then deal with the three algae groups. The most explored ones in this area are brown algae, which contain a unique type of tannins called phlorotannins in their thallus. This is followed by green siphonous algae from the family Dasycladaceae, which synthesize sulphated coumarins and then conjugating algae in which gallic acid-based phenolic compounds have been found. The common feature of these substances is, as with land plants, the ability to absorb radiation from the ultraviolet part of the spectrum and...
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