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Evolution of genome size in streptophyte algae genus Zygnema and its ecological consequences
Lukeš, Jiří ; Čertnerová, Dora (advisor) ; Lučanová, Magdalena (referee)
Genome size is a trait that varies 64,000 × across eukaryotic diversity. However, this variability has nothing to do with the complexity of organisms. The amount of DNA itself is however related to a number of phenotypic traits of organisms. Specifically, studies conducted on plants look for possible connections between genome size and the ecological requirements of individual species. Similar studies in microscopic algae are not abundant and often face a number of methodological problems. This thesis presents genome size data obtained by flow cytometry for 129 representatives of the genus Zygnema belonging to 68 evolutionary lineages. Measurements revealed a genome size range within this genus from 0.22 to 5.06 pg. At the same time, several lines showing considerable variability in genome size were described, which in many cases indicates possible polyploidization in this genus. The identification of an identical GC base pair ratio in selected putative polyploid and monoploid representatives supported the hypothesis of polyploidization. The general correlation of cell size and genome size within this group was also validated. Due to the known phylogenetic relationships between the measured lineages, the genome size evolution in the genus Zygnema was reconstructed. Further, possible relationships...
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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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