|
|
Lichens on metal-rich substrates with emphasis on serpentinites
Ghlimová, Heda ; Steinová, Jana (advisor) ; Peksa, Ondřej (referee)
Serpentinite is an ultramafic rock covering about 1 % of the Earth's surface. Serpentinite contains a high content of heavy metals such as Ni, Cr, Co and, conversely, low content of major nutrients N, P, K. The high concentration of Mg reduces the availability of Ca to plants. Serpentinites are not distinguished only by their chemistry - they are also, for example, poorly thermally conductive and soils that form on the serpentine subsoil are considered infertile. This complex of properties causes the formation of so- called serpentinomorphoses in vascular plants and also promotes the development of endemism. However, these adaptations do not occur in fungi and in lichens and bryophytes they occur only partially. This bachelor thesis summarizes the basic physiological mechanisms by which myco- and photobionts ensure the survival of lichens on substrates with high content of heavy metals - it is above all extracellular absorption of metals (binding to cell wall ligands), intracellular absorption (and subsequent detoxification with metallothionein and phytochelatins), and exclusion of metals on the surface of mycobiont hyphae or on the surface of the thallus (binding to oxalates and secondary metabolites). The bachelor thesis also summarizes the morphological adaptations that occur in lichens in...
|
|
|
Gastropods, trees, pH, subsoil and epiphytic lichens
Pelant, Filip ; Svoboda, David (advisor) ; Peksa, Ondřej (referee)
Epiphytic lichens are under considerable grazing pressure due to invertebrate lichenivores, mostly gastropods. Preferences of tree-climbing gastropods affect vertical distribution of lichens, their habitat preferences and whole area of distribution. Higher grazing pressure is expected on sites with basic subsoil and sufficient sources of calcium, where the abundance of gastropods is higher. Most of researches about the topic of grazing pressure were therefore conducted on such sites, although this hypothesis has never been formally tested. Epiphytic communities are also affected by pH and other properties specific to its photophyte. Nevertheless, it is not known, if the same applies for grazing gastropods and how is the grazing pressure affected by tree species. I have addressed these questions in my thesis. I set an 80-days-long field transplantation experiment in the mixed forest of Moravský kras (South Moravia, Czech Republic). Glass fiber meshes with lichen thalli were placed on sixty trunks of three tree species (Carpinus betulus - hornbeam, Abies alba - fir, Fagus sylvatica - common beech) on both calcareous (limestone) and acidic (granodiorite) sites. Abundance and diversity of gastropods were measured. Determined grazing pressure was higher than pressure detected by other authors and was...
|
|
| |
|
| |
|
|
Photobiont diversity in lichen thallus Psora decipiens
Jadrná, Iva ; Škaloud, Pavel (advisor) ; Peksa, Ondřej (referee)
Psora decipiens is a characteristic species of the terricolous lichen community Toninio-Psoretum decipientis distributed mostly on calcareous or basic substrates. The community consists in various modifications of lichens Placidium squamulosum, Toninia sedifolia, T. opuntioides, Fulgensia fulgens, F. bracteata and others. Photobionts of the lichen Psora decipiens were determined. Psora decipiens shared with Placidium sp. the single photobiont species, a common terrestrial alga Myrmecia israeliensis. Cloning of ITS rDNA revealed high intrathalline variability in M. israeliensis within a single lichen thallus. Several genotypes were often found in a thallus, uncovering either a high mutation rate of the algae or constant relichenization processes. Saxicolous Psora species (P. testacea, P. himalayana, P. valesiaca and P. rubiformis) had M. biatorellae as a photobiont, indicating a possible photobiont influence on substrate specifity of Psora lichens. Finally, the proper methodology used for identification of lichen photobionts is discussed. For a correct photobiont identification, morphological investigations of intrathaline diversity combined with coherent molecular techniques are needed. Such procedure was not applied in the former studies of Psora decipiens, resulting in a poor characterization of...
|
|
|
The effect of heavy metals on the physiology of lichens
Hrdinová, Aneta ; Peksa, Ondřej (advisor) ; Svoboda, David (referee)
Lichens are known for their sensitivity to environmental changes, however, the tolerance to different changes may vary among particular taxa. There are lichen species extremely sensitive as well as very tolerant to pollution. The species growing in areas with a higher content of heavy metals belong to the second group. These sites may by of natural origin (ore), but very often they have arose as a result of anthropogenic activities (imissions in industrial and urban areas, various heaps etc.). The interaction between photobiont and mycobiont in the thallus can probably explain the success of lichens in environment enriched by heavy metals. The stress caused by heavy metals leads to increasing production of reactive oxygen species in cells of photobiont and mycobiont. Reactive oxygen species cause lipid peroxidation, damage of proteins and nucleic acids, and the degradation of chlorophylls. Although mycobiont provides the photobiont cells partial protection (particularly thanks to binding of metal ions to the cell wall and the formation of water-insoluble secondary metabolites), photobiont is exposed to high amounts of metals. Therefore, both symbionts have developed a range of detoxification mechanisms. The aim of this thesis was to summarize the findings on the effect of heavy metals on the...
|
|
|
Epiphytic lichens of the Czech Republic
Pelechová, Kateřina ; Svoboda, David (advisor) ; Peksa, Ondřej (referee)
This bachelor thesis researches the works of the years 1908-2013, which deal with the occurrence of epiphytic, i.e. growing on tree species, lichens in the Czech Republic. In the introduction there is briefly interpreted definition of lichens and epiphytes and the relationship between lichens and heir environment (with an emphasis on air pollution) is described. The main part is devoted to the processing of data found in the literature - when and on which tree species is the lichen growing - and is divided into two periods (1908-1970 and 1971-2013). The frequency of lichen species changes between periods - links between lichens and tree species and preference of the species and its changes over time, changes in preference of pH of bark of trees and tree species with the highest number of species of lichens. The study contains a list of 429 lichen species occurring on tree species in the Czech Republic. Powered by TCPDF (www.tcpdf.org)
|
|
|
The efect of environmental variables on diversity of lichen photobionts
Červenková, Tereza ; Škaloud, Pavel (advisor) ; Peksa, Ondřej (referee)
Lichens represent a synergistic combination of at least two organisms, a heterotrophic fungus and a photosynthetic alga or a cyanobacterium. This association has resulted in a symbiotic organism, which is well tolerant to environmental influences. In fact, symbiotic relationship provides mutual benefit for both organisms. It is generally well known that the fungal partners of lichens are far less sensitive to environmental conditions, such as the temperature, altitude, rainfall or the type and composition of the substrate, in comparison to their algal partners. Therefore, lichen forming fungi have much wider ecological valences than the photobionts interacting with them. Indeed, most of the photosyntetic genera and species are adapted only to certain environmental conditions. For this reason, the symbiotic algae and cyanobacteria probably play a major role during the initial lichen formation on the site. This thesis focuses on the adaptability of photoautotrophic symbionts of lichens, coccoid green algae and cyanobacteria, to environmental conditions. Ecological diversification of photobionts has a direct impact on their genetic differentiation and thus to differentiate lichen species themselves. Unfortunately, in many studies the authors mostly dealt with the diversity of macroscopic symbiotic...
|
|
|
Lichens and (heavy) metals
Hrdinová, Aneta ; Peksa, Ondřej (advisor) ; Malíček, Jiří (referee)
My thesis is focused on liches and heavy metals. In first part includes the general characteristics of lichens, the short description of their biology, morphology and anatomy. The next part is focused on the characteristics of the methods of absorption of metals by lichens, their physiological effects on the body and the mechanisms of defense against the toxicity of metals lichens. The work includes the list of species of lichen, and their relationships to particular heavy metals. Key words: Lichens, heavy metals, metal tolerance, detoxification, copper
|
|
|
Photobiont diversity in the lichen genus Stereocaulon (Lecanoromycetes, Ascomycota)
Vančurová, Lucie ; Škaloud, Pavel (advisor) ; Peksa, Ondřej (referee)
This thesis is focused on the diversity of lichen photobionts and its relation to the mycobionts and environmental factors. The key objective is to map the diversity of lichen photobionts of the genus Stereocaulon, which has been insufficiently examined in comparison with related lichens Cladonia and Lepraria. In total, 92 samples belonging to 12 species of genus Stereocaulon were examined, being found in four continents, at the altitude of 50 to 2 900 metres a. s. l., and variety of natural and artificial substrata. Phylogenetic analyses were inferred on the basis of ITS rDNA, actin type I, 18S rDNA and rbcL sequences. Photobionts belonging to two unrelated genera within Trebouxiophyceae, Asterochloris and Chloroidium, were found in thalli of Stereocaulon lichens. While Asterochloris represents one of the most frequent photobionts of various lichens, Chloroidium has been until now recorded as a lichen photobiont very rarely. The content of heavy metals in substratum can be considered as a determinative factor for its occurrence. A new lineage affiliated to genus Asterochloris was discovered on the island La Palma (the Canary Islands). Interestingly, none of common, widespread Asterochloris lineages has been found in this locality. The lichen photobionts of the genus Stereocaulon were discovered in 12 of...
|
guest ::
