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Factors limiting the distribution of the mycoheterotrophic plants in fragmented landscape
KOTILÍNEK, Milan
This thesis investigates the influence of habitat, dispersal abilities and evolution on distribution of mycoheterotrophic plants represented by six orchid species. Several methods including seed trapping, in situ seed germination, fungal barcoding, gene flow study and stable isotopes analyses were used to examine this topic. The final synthesis of these approaches shows lower limitation by dispersal abilities and stronger limitation by habitat.
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Adaptations of orchid roots to epiphytism
Ungrová, Anna ; Ponert, Jan (advisor) ; Soukup, Aleš (referee)
The evolutionary success of orchids is to a large extent driven by the ability to colonize epiphytic habitats. This ability is based on a number of adaptations at different levels, and the adaptive features of aerial roots can play a key role because the roots are practically the only organ providing water and nutrient uptake. The main aim of this work is to review available information about roots of epiphytic orchids (Orchidaceae), especially their adaptations to the epiphytic way of life. The roots of epiphytes must deal with a periodic lack of water and nutrients, often in conjunction with high irradiation. The roots of epiphytic orchids adapt to these conditions on many levels. Rhizodermis forms a velamen capable to retain water and nutrients and protecting roots against environmental conditions including UV radiation. Root cortex contains chloroplasts, which can perform photosynthesis at least in some orchid species. Exodermis is well differentiated with thick secondary cell walls and acts as a selective barrier for the transport of substances with the use of passage and aeration cells. The function of some adaptive structures is still unclear, for example, tilosomes could regulate transpiration. Epiphytism evolved multiple times in orchids, and some root adaptations therefore originated...
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Interactions of initially mycoheterotrophic plants with environment
Figura, Tomáš ; Ponert, Jan (advisor) ; Kolařík, Miroslav (referee) ; Janoušková, Martina (referee)
Initially mycoheterotrophic plants have recently been declining in the wild, even without apparent causes. They are affected by a number of biotic and abiotic factors. The aim of this work is to investigate how selected factors, such as nitrate or symbiotic fungi, may influence their distribution in nature. In particular, the work applies in vitro experiments, molecular determination of fungal symbionts and stable isotope analyses. It describes both the effects of abiotic factor, specifically nitrate, and biotic interactions of initially mycoheterotrophic plants with fungal symbionts. The inhibition of germination by extremely low concentrations of nitrate in asymbiotic in vitro cultures was observed in several orchid species. The degree of sensitivity of each species to nitrate corresponds with the nitrate content of the soil and the nutrient availability requirements of the species according to Ellenberg indicator values. The inhibitory effect of nitrate on orchid germination was also observed in symbiotic in vitro cultures. Out of five tested fungal strains, only one Ceratobasidium was capable of eliminating the inhibitory effect of nitrate. Furthermore, the work reveals that green mixotrophic orchids use photosynthates to nourish the aboveground parts, whereas the belowground parts are...
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The role of chloroplasts in the stele of epiphytic orchid roots
Ungrová, Anna ; Ponert, Jan (advisor) ; Lhotáková, Zuzana (referee)
The photosynthesis of the aerial roots of epiphytic orchids has been the subject of numerous studies. However, the roots are always evaluated as a homogeneous structure, even though they actually consist of significantly different areas. This work deals for the first time with the possibility of the spatial distribution of photosynthesis between the root layers, specifically the cortex and the stele. A combination of various microscopic techniques, the histochemical characterization of the apoplastic barriers and the immunohistochemical localization of the photosynthetic enzyme phosphoenolpyruvate carboxylase has been used. The results show that well-developed chloroplasts in the stele probably occur in the subfamily Epidendroideae in all epiphytic representatives, while in the subfamily Vanilloideae they occur occasionally. The ultrastructure of chloroplasts from both areas is systematically different, so it is likely that their functions also differ. Apoplastic barriers are prominent in the roots and differentiate early during root development, which can effectively isolate chloroplasts in the stele from the cortex. Chloroplasts also occur in the sclerenchyma cells of the stele, where were identified hitherto unknown pits in cell walls that could provide gas exchange within the stele....
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Adaptations of orchid roots to epiphytism
Ungrová, Anna ; Ponert, Jan (advisor) ; Soukup, Aleš (referee)
The evolutionary success of orchids is to a large extent driven by the ability to colonize epiphytic habitats. This ability is based on a number of adaptations at different levels, and the adaptive features of aerial roots can play a key role because the roots are practically the only organ providing water and nutrient uptake. The main aim of this work is to review available information about roots of epiphytic orchids (Orchidaceae), especially their adaptations to the epiphytic way of life. The roots of epiphytes must deal with a periodic lack of water and nutrients, often in conjunction with high irradiation. The roots of epiphytic orchids adapt to these conditions on many levels. Rhizodermis forms a velamen capable to retain water and nutrients and protecting roots against environmental conditions including UV radiation. Root cortex contains chloroplasts, which can perform photosynthesis at least in some orchid species. Exodermis is well differentiated with thick secondary cell walls and acts as a selective barrier for the transport of substances with the use of passage and aeration cells. The function of some adaptive structures is still unclear, for example, tilosomes could regulate transpiration. Epiphytism evolved multiple times in orchids, and some root adaptations therefore originated...
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Evolutionary history of Orchidaceae in the Mediterranean basin
Jankolová, Lucie ; Ponert, Jan (advisor) ; Chrtek, Jindřich (referee)
The matter of this text is the Orchidaceae family occuring mainly in the Mediterranean basin. The selected genera from the Orchidinae subtribe are discuted, namely it is about Anacamptis, Neotinea, Ophrys, Orchis and Serapias genera. Different genera of this family have tendency to diversify to a different extent, some of them content thousands of taxa, another have orderly onely few dozens of them. The work is therefore focused on the genera themselves and on the factors, that may have had any influence on their diversification. Key words: evolution, radiation, mediterranean climate, Orchidaceae, diversification, diversity, Mediterranean basin
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Seed dormancy mechanisms of mycoheterotrophic plants
Figura, Tomáš ; Ponert, Jan (advisor) ; Weiser, Martin (referee)
Seeds of mycoheterotrophic plants known as dust seeds which are typical for the family Orchidaceae and 11 other families have inner (physiological, morphological) and outer (physical) dormancy. Dormancy breaking it is a necessary step for a seed to germinate. For breaking the exogenous dormancy it is necessary to break both inner and outer testa, which can be done by scarification. Chemical scarification, mostly done by chlorine, is commonly used and it seems to be the best way for breaking dormancy and also for sterilization of seeds. Other sterilization agents as ethanol and sulfuric acid are also commonly used. For breaking the inner (physical) dormancy, application of growth regulators can be useful, especially in the case of cytokinins, specifically kinetine. Abscisic acid induces dormancy and ethylene induces germination. Anorganic forms of nitrogen have also inhibitory effects for germination at least for some species. Seeds of most orchid species also need a period of chilling after sowing and for germination they mostly need temperature around 23řC.
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Does it differ the germinability of the chosen orchids on the natural and renewed meadows?
SUCHÁČEK, Pavel
The survey presented in this thesis focused on germination of six orchid species in the Protected landscape area White Carpathians; specifically Platanthera bifolia, Neottia ovata, Anacamptis pyramidalis, Gymnadenia conopsea subsp. conopsea, Traunsteinera globosa, Orchis militaris on restored medows of various age. As the control, two National Protected Areas (Zahrady pod Hájem and Čertoryje) were used. The initial stage of germination was detected on both restored and control meadows. The advanced stage of germination (protocorm) was recorded in three species (GC, NO, PB) on restored meadows, and in all species on kontrol meadows. The other aim of the thesis was to determine via molecular methods, which species of mycorrhizal fungi are associated with the model orchid species.
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