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Flexibility of cyclitol metabolism as a component of effective plant defense against water scarcity
Skulníková, Barbora ; Konrádová, Hana (advisor) ; Lhotáková, Zuzana (referee)
This bachelor thesis is focused on plant defence mechanisms against drought stress and salinity stress associated with the production of compatible solutes, while attention is paid to the accumulation of cyclic sugar alcohols, myo-inositol and its methylated derivatives. It describes the occurrence of these substances, their biosynthesis and function in plants. Another part of this thesis focuses on the crystalline ice plant (Mesembranthemum crystallinum), which is an important producer of these substances and serves as a model used to study the stress response in plants. It describes its life cycle and especially the mechanisms that makes it resistant to drought stress and salinity. The last chapter is dedicated to the knowledge gained through the study of transgenic plants, which were prepared using genes from crystalline ice plant and other stress tolerant plants.
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Utilization of selected fungal saccharides by orchids and possibility of their transport in mycorrhiza
Dostálová, Magdalena ; Ponert, Jan (advisor) ; Votrubová, Olga (referee)
Orchideoid mycorrhizal symbiosis (OM) can be found in nearly one tenth of higher plant species. This symbiosis is absolutely critical for orchids as they are unable to grow from seeds without external energy which is in nature provided by symbiotic fungi. The mechanism of transport between symbionts remains unknown. It is supposed that trehalose is one of the substances transported from fungi to plants as the source of energy. This thesis mainly aims to find out which other fungal saccharides could contribute to the process. The ability to utilize selected compounds was tested on protocorms of the common marsh orchid, Dactylorhiza majalis. The results showed that arabitol, erythritol, mannitol and sucralose are not utilized, while xylitol, sorbitol, glycerol and mannose are. Glutamin, an amino acid also suspected of participation in the OM transport, does not suffice as a source of energy. In orchids there were identified three groups of sequences coding for manitol dehydrogenase and two groups of sequences coding for sorbitol dehydrogenase. Key words: orchideoid mycorrhizal symbiosis, sugar alcohols, mannose, glutamine, carbon flow, energy flow, sorbitol dehydrogenase, in vitro
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