National Repository of Grey Literature 44 records found  beginprevious16 - 25nextend  jump to record: Search took 0.00 seconds. 
Resource sharing in clonal plants - a review of labelling studies
Nováková, Tereza Anna ; Duchoslavová, Jana (advisor) ; Weiser, Martin (referee)
Clonal plants are characterised by their ability to reproduce without sexual reproduction. This is done by the formation of daughter rhizomes or ramets. By maintaining a functional link between them, ramets can share information and resources. The effect of sharing on the growth of clonal plants by sharing can be investigated using biomass experiments. To follow the movement of substances in more detail, labelled substances are used. I will discuss the work on tagging substances and recording their translocation in this thesis. These are carbon, water, nitrogen, phosphorus and calcium. The translocation of substances appears in many cases to be in the direction from the parent ramet to the daughter ramet, but there are plants translocating in the opposite direction. This is influenced by many factors such as plant species, anatomical structure, the age of the ramets and their current needs, as well as abiotic factors and the mobility of the particular element. Water as a carrier medium for minerals may also indicate some dependence of one on the other during translocation. In the future, it would be useful to add comprehensive information on sharing in individual species. Information on how sharing changes during ontogeny, multi-element clonal fragments and tracking of multiple elements in a plant...
Totalitarian tendencies of German colonial policies
Weiser, Martin ; Moravcová, Dagmar (advisor) ; Nálevka, Vladimír (referee)
The diploma thesis Totalitarian tendencies of German colonial policies deals with German colonial policies towards Africans in the period between 1884-1914. The main focus is placed on the characteristics and analysis of German native policy in the most important of German colonies - German South West Africa. This piece attempts to pinpoint the relationship between the colonizers and the colonized, to illustrate the racist prejudice of the Germans and to describe the impact of these ideas on the colonial reality. Furthermore, this work reflects upon the Herero war, with particular interest being paid to the German war strategy, and tries to identify the reasons behind its radicalization as well as to resolve the query concerning the genocidal intent. The totalitarianism section of this thesis explores the totalitarian aspects of German native policy in German South West Africa and their development following the Herero war. A comparison of German colonial policies towards the natives with colonial policies of the other major powers active on the African continent follows. The final chapter endeavours to answer the question regarding the continuity of German history and continuity between German colonialism and National Socialism.
The effects and mechanisms of mutual identification in plant competition
Martincová, Aneta ; Weiser, Martin (advisor) ; Kuťáková, Eliška (referee)
Plants, being sessile organisms, need to find some way to cope with insufficient resources and resource competition with their neighbours. In order to be able to react as effectively as possible, it would be advantageous for them to have some mechanism for identifying other plants in the environment and easily detemining how to treat them. In the last few decades a number of works have been published that suggest the existence of such abilities in plants. After the performed experiments, some of the proposed types of such recognition seem to be very close to reality. The main aim of this thesis is to present the individual above-ground and below-ground types of plant identification - mechanical contact, light signaling, volatile stimuli, root exudates, acoustic emissions and electrical signaling, and summarize their possible effect and use in communication between plants. Key words: plant communication, plant ecology, kin recognition, mechanical signaling, light signaling, volatile signaling, root exudates
Plant perception of soil heterogeneity in the field
Hrouda, Adam ; Weiser, Martin (advisor) ; Martínková, Jana (referee)
Nutrients are usually patchily distributed in natural soils. Plants are often able to respond to nutrient heterogeneity in artificial conditions by active plastic changes of root system morphology. The occurrence or magnitude of a foraging response can be altered by the presence of competition. However, it is unclear to what extent root foraging takes place in the field. I conducted a field experiment in order to determine the effect of an artificial nutrient patch on fine belowground biomass of (a) an established community and (b) model plants. The study array consisted of a grid of 30×30 cm plots with model plants located in the centre. Half of the plots contained the artificial patch located 5.5 cm from the model plant. Fertilizer patch treatment did not increase mean plot fine underground biomass. Instead, fine underground biomass was higher in places of greater soil moisture estimated from mean plot EIVs. Neither total model plant root biomass nor proportion of roots in the enriched quarter increased in the fertilizer treatment. Competition was probably higher in fertilized than in control plots judging by a 2-fold increase in death rate of model plants. However, greater proportion of model plants flowered in the treatment plots. Possible causes include a plastic response to the patch as well...
Ecological specializations of birds based on spatial co-existence patterns
Petrová, Kristýna ; Hořák, David (advisor) ; Weiser, Martin (referee)
Ecological specialization based on co-existence patterns is new methodology used for niche breadth measurement using co-existing community with occupancy data. It results in generalist-specialist continuum according to value of speciali- zation index. The aim of this thesis was testing index stability at spatial and tem- poral scale, compare this specialization index with other specialization indices and study changes in specialization with time changes in occupancy. Specialization was quantified using data of breeding birds atlases in the Czech Republic and Europe using two selected indices Theta and Simpson. Methodology seems to be sensitive to spatial scale. Instability appears at small scale for birds, stability and correlation between indices increase with gre- ater scale. Problems with using point counts corresponds to their unsuitability encompass birds' habitats, especially for water dependent birds. Correlations be- tween different time periods are stronger at greater spatial scale. Specialization based on co-existence patterns correlates with specialization according to experts' opinions. Results from comparing changes in specialization with changes in occu- pancy suggest, that most of species tend to leave more diverse sites with occupancy decline.
Spatial distribution of plant roots in heterogeneous soils
Hrouda, Adam ; Weiser, Martin (advisor) ; Kuťáková, Eliška (referee)
In natural ecosystems, water and mineral nutrients are unevenly distributed in soil. Plants respond to this heterogeneity with active phenotypic plasticity of their root system. This plasticity can be either morphological, physiological or their combination. Both single-plant and competition experiments reveal that species differ in responses to heterogeneous distribution of nutrients. Based on observed differences, several theories emerged that describe the mechanisms of species coexistence in plant communities. Thanks to many experimental studies we currently have a better understanding of plastic root responses to soil heterogeneity, but the role of root plasticity in community establishment and development remains unclear. Precise observation of field soil heterogeneity is needed together with more realistic experiments reflecting the natural environment.
Seasonal variability of plant secondary metabolism (Artemisia sp.)
Koutská, Barbora ; Weiser, Martin (advisor) ; Dostál, Petr (referee)
Plant secondary metabolites (SM) are widely used by humans in many ways (pharmacy, biotechnology etc.). For making their use even more effective, it is important to know the seasonality of these chemicals in plants and what affect those changes. Three Artemisia species (Artemisia annua, A. absinthium, A. vulgaris) were cultivated during one vegetation season (from April to September 2016). Plant growth parameters and the beginning of their generative stages were observed, and leaf samples were collected regularly. Samples of some plants were collected repeatedly. A generalist herbivore (migratory locust), was used as a proxy for studying changes in plant secondary metabolism during the vegetation season. The results proved presence of defence secondary metabolites in plants except A. vulgaris species where the role of SM in defence was not shown. Levels of SM changed nonlinearly during the vegetational season and were time-dependent. Plant size did not influence the levels of SM in plants. Levels of SM were low at the beginning of the experiment followed by rapid increase and remaining on maximal levels. The plants which lost their biomass repetitively grew slowly and bloomed later than the plants which were clipped only once. A delay trend showing seasonality of the plant SM was not proved. In...
Changes in timing of germination caused by neighbouring seeds and how it is connected with species traits.
Kos, Pavel ; Weiser, Martin (advisor) ; Hadincová, Věroslava (referee)
The time when the seed germinates is very important. Ability to change the time of germination may be very advantageous. It allows the emerging seed to choose the best time according to abiotic conditions, and also to avoid of competition with neighbouring individuals. The seed reacts not only on adult plants and seedlings, but also on other seeds, with which is able to communicate. For a better understanding to this mechanism I conducted an experimental study with twenty-six species. The species were selected according to their position in long succession seres of mesic/xeric abandoned fields in Český kras. The seeds were left to germinate in pairs in all combinations among them. Here I present the results where I show how the time of emergence changes, depending on presence of neighbouring seed. Also, I show how these changes in germination are related to species specific traits. Out of this, I tried to influence communication between seeds by adding activated carbon. Activated carbon should stop the communication by highly absorbing surface. The time of germination of seeds which germinated alone was not proportional to the time of germination of seeds which germinated with neighbours. This correlation showed up like nonlinear, late-emerging seeds emerging unproportionally later when emerging...

National Repository of Grey Literature : 44 records found   beginprevious16 - 25nextend  jump to record:
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2 Weiser, Michael
2 Weiser, Michal
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