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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Didaktické využití vybraných čeledí krytosemenných rostlin ve výuce na ZŠ a víceletých gymnáziích / Didactic Utilization of Selected Angiosperms in Teaching at Elementary and High Schools

Moldaschlová, Jana January 2019 (has links)
The diploma thesis deals with a didactic use of selected angiosperms in teaching at elementary and high schools. It provides theoretical knowledge concerning angiosperms, selected families, and plant species. Furthermore, it describes selected teaching techniques and methodology which can be used in teaching of the angiosperms. This thesis contains specific suggestions of the teaching methodology dependent on the selected plant families. A part of the thesis is a questionnaire survey, which contains the use of various forms and methods of teaching in natural science lessons at elementary schools and high schools. The results of the practical work are represented by practical exercises, worksheets and didactic games which teachers could use in teaching of the angiosperms. Key words: teaching techniques and methodology, questionnaire suvey, angiosperms
42

Developmental Evolution of the Progamic Phase in Nymphaeales

Taylor, Mackenzie Lorraine 01 May 2011 (has links)
The period between pollination and fertilization, or the progamic phase, is a critical life history stage in seed plants and innovations in this life history stage are hypothesized to have played an important role in the diversification of flowering plants. Over the course of this dissertation research, I investigated programic phase development in Nymphaeales (water lilies), an ancient angiosperm lineage that diverged from the basalmost or next most basal node of the angiosperm phylogenetic tree and that is represented in the oldest angiosperm fossil record. I used field experiments and microscopy to document pollination biology, breeding system, and reproductive developmental traits in two families of Nymphaeales: Cabombaceae (Brasenia, Cabomba) and Hydatellaceae (Trithuria). Nymphaeales exhibits considerable variation in reproductive traits and true carpel closure, wind-pollination, and a primarily selfing breeding system have arisen independently in the lineage. Pollen tube pathway length, timing of stigma receptivity, and pollen tube growth rates are conspicuous traits that have undergone considerable modification in concert with shifts in pollination biology and breeding system. Post-pollination developmental processes in Nymphaeales appear to experience selective pressures similar to those experienced by more derived angiosperms and to evolve in similar ways. Nymphaeales also exhibits traits, such as accelerated pollen tube growth, callosic pollen tube walls, and the formation of callose plugs, that are almost certainly plesiomorphic in angiosperms and may have facilitated modification of carpel structure and progamic phase ontogenies. The finding that pollen tube traits that underlie developmental flexibility were already in place before the divergence of Nymphaeales supports the hypothesis that innovations in male gametophyte development were instrumental in facilitating early angiosperm diversification.
43

Under which conditions is the C4metabolic pathway favored? : When does the C4 metabolic pathway become less costlythan the C3 metabolic pathway?

Lindgren, Kim January 2011 (has links)
C4 photosynthesis is an advanced complement to the more ancestral and more commonpathway refereed to as C3. C4 metabolism has evolved in several taxa, and it is theorized thatit worked as an adaptation to the low CO 2 levels characteristic of late geological time. Theadaptation also carries with it some resistance to the negative effects brought on by hightemperatures and drought. C4 metabolism is, however, not free, meaning that underconditions of lower temperature and higher CO2-levels, C3 photosynthesis is still moreviable. This makes it interesting to study how C4-species might shift their ranges in responseto climate change, as it implies both elevated CO 2 levels and higher mean temperatures inmost parts of the world. In this report, I develop a model based on the CO 2/O2 specificity of Rubisco from Spinach(Spinacia oleracea) at different temperatures, using data found in literature on the subject.The resulting model has some success in describing the current distribution of C4 species,using temperature and CO2 concentration as explanatory variables.
44

Evolution of the genus Aristolochia (Aristolochiaceae) in the Eastern Mediterranean including the Near East and Caucasia

Mahfoud, Hafez M. 19 February 2010 (has links) (PDF)
The Aristolochiaceae are one of the largest angiosperm families, the family has been divided into two subfamilies: Asaroideae, which include Asarum and Saruma, and Aristolochioideae, which includes Thottea sensu lato and Aristolochia sensu lato (Kelly and Gonzales, 2003). Aristolochia sensu lato comprise between 450 and 600 species, distributed throughout the world with centers of diversities in the tropical and subtropical regions (Neinhuis et al., 2005, Wanke et al., 2006a, 2007). However, the extended Mediterranean region including Turkey, the Caucasus and the Near East is likely to be the only diversity hotspot of the genus Aristolochia in the northern hemisphere were up to 60 species and subspecies could be observed (Wanke 2007). Most important contributions to the knowledge of these species were published by Nardi (1984, 1988, 1991, 1993) and Davis & Khan (1961, 1964, 1982), all of these studies were based on morphological characters only. In recent years, with the progress of molecular techniques and in light of the systematic chaos, a detailed study was needed to unravel the evolutionary history prior to a taxonomic revision of this group. The first chapter of my thesis should be regarded as the starting point for more detailed investigation on population level. Preliminary molecular phylogenitic analysis recovered the Mediterranean Aristolochia species as monophyletic (de Groot et al 2006). However, only very few members were included in that study. The latest phylogenetic study by Wanke (2007) dealed with west Mediterranean Aristolochia species and sampled also few members belonging to the east Mediterranean and Caucasian species (3 from Greece, 2 from Georgia and 1 from Turkey). This study reported the Mediterranean Aristolochia species as two molecular and morphologically well supported clades, which were sister to each other. Furthermore, the two closely related species A. sempervirens and A. baetica which have an east west vicariance and are known as Aristolochia sempervirens complex has been recovered as sister group to the remaining west Mediterranean species. A detailed investigation of the evolutionary history of this group is the topic of the second chapter of my thesis (Chapter 2). The Aristolochia sempervirens complex is characterized by an unusual growth form and has a circum Mediterranean distribution. The investigation of these species complex seem to be of great importance to understand speciation and colonization of the Mediterranean by the genus Aristolochia and might shade light in historical evolutionary processes of other plant lineages in the Mediterranean. Furthermore, I test applicability and phylogenetic power of a nuclear single copy gene (nSCG) region to reconstruct well resolved and highly supported gene genealogies as a prerequisite to study evolutionary biology questions in general. Furthermore, a comprehensive overview of leaf epicuticular waxes, hairs and trichomes of 54 species from the old and new world taxa of the genus Aristolochia were investigated using scanning electron microscopy (SEM) to clarify taxonomic status of theses species in contrast to their molecular position. Also this study which is the third chapter of this thesis (Chapter 3), has a strong focus on Mediterranean Aristolochia and tries to provide additional support for molecular findings based on epicuticular waxes and to test them as synapomorphies. Each chapter has its own introduction and abstract resulting in a short general introduction here.
45

Bumblebees in a region of northwestern Scania: Is species number correlated to the number of flowering angiosperms and does gene flow occur between four locations?

Dahlgren, Linnea January 2014 (has links)
Pollination, one of our ecosystem services, is considered to be in critical condition due to a worldwide reduction in pollinators and their biodiversity. As the agricultural landscape becomes more and more intense, the pollinators lose important food and living resources.     In temperate ecosystems, bumblebees (Bombus spp) are an important group of wild pollinators, and as with pollinators in general, they are declining in both abundance and richness, in Sweden as well as other countries.      The purpose of this study was to see if bumblebee species number of a location is linked to the location’s number of flowering angiosperm species in northwestern Scania when examining eight locations, and to see if gene flow existed between four chosen locations.        The result of this study suggests that it is not possible to tell from the flowering angiosperm species how many bumblebee species that will be abundant, but that it might be possible to tell the number of bumblebee individuals. With the number of bumblebee species, the abundant Fabaceae species was more important than the total number of flowering angiosperms of the location. The number of abundant Fabaceae species was strongly correlated to the bumblebee diversity index of the locations, indicating that it is a group of flowers closely linked to bumblebees.      To see if gene flow occurred between the chosen locations, mtDNA sequences were compared in neighbor joining trees. The result showed that though some tendencies of isolation existed, gene flow seemed to occur in general between the locations in that fragmented and human dominated landscape of northwestern Scania.
46

Investigating the Expansion of Angiosperms during the Cretaceous Period using a Modeling Approach

Gousseva, Anastasia 31 December 2010 (has links)
The use of Dynamic Global Vegetation Models (DGVMs) in paleo-vegetation studies is a practical new approach in paleo-ecology as it allows for process-based investigations within a flexible framework. The goal of this study is to evaluate the applicability of Lund Potsdam Jena (LPJ) – DGVM in a paleo-study of Cretaceous angiosperm spread, while testing several pre-existing theories regarding the spread through model experimentation. I assessed the independent and interactive role of climate variables (temperature, precipitation, atmospheric CO2 concentration, and seasonality), latitudinal light regime, soil structure, and plant characteristics (tree versus grass, and deciduousness) in influencing angiosperm expansion by simulating the response of Cretaceous land cover to changes in each factor. I found that temperature and light were the most influential variables in determining angiosperm success, while plant structure and deciduousness may carry implications for early angiosperm establishment and community competition dynamics. LPJ showed great potential for refinement and effective future use in paleo-applications.
47

Patterns and biological implications of DNA content variation in land plants

Bainard, Jillian D. 21 October 2011 (has links)
DNA content varies significantly over land plants, and is known to correlate with various aspects of plant form and function. In the present study, two measures of DNA content were examined in taxa across the land plant phylogeny: genome size (or C-value) and endopolyploidy (or endoreduplication index, EI). Additionally, the relationships between DNA content and various morphological and ecological traits were assessed. DNA content was determined for 64 liverwort species from 33 families. There was a large range in 1C-values from 0.27 to 20.46 pg, but no endopolyploidy was observed. There was no correlation between genome size and breeding system (monoecy vs. dioecy). Genome size and degree of endopolyploidy were determined for 74 moss species from 21 families. Genome sizes were constrained in this group, with 1C-values ranging from 0.25 to 1.21 pg. Endopolyploidy was high in all species except from the Sphagnaceae. Additionally, 1C-value was negatively correlated with desiccation tolerance but was not correlated with breeding system. DNA content variation was determined in 31 monilophyte (fern) species (including three horsetails) and 6 lycophyte (clubmoss) species. There was a wide range in 1C-values from 2.79 to 26.90 pg, and there was no indication of endopolyploidy in any of the species. Multivariate analyses were used to explore the relative contribution of traits and phylogenetic placement to DNA content varation in 41 angiosperm species. Six measures of DNA content (2C-value, 1Cx-value, leaf EI, stem EI, petal EI and root EI) were assessed. Phylogeny explained more of the variation observed in the six measures of DNA content than 21 ecological and morphological traits. However, many of the traits were able to explain some of the variation in DNA content, both with and without phylogeny included as a covaraite. One trait that was consistently correlated with DNA content was the association with arbuscular mycorrhizal (AM) fungi. In a controlled experiment, the EI in root cells colonized by AM fungi significantly increased compared to non-mycorrhizal plants. This thesis increases our knowledge regarding the extent and significance of variation in DNA content in land plants.
48

Investigating the Expansion of Angiosperms during the Cretaceous Period using a Modeling Approach

Gousseva, Anastasia 31 December 2010 (has links)
The use of Dynamic Global Vegetation Models (DGVMs) in paleo-vegetation studies is a practical new approach in paleo-ecology as it allows for process-based investigations within a flexible framework. The goal of this study is to evaluate the applicability of Lund Potsdam Jena (LPJ) – DGVM in a paleo-study of Cretaceous angiosperm spread, while testing several pre-existing theories regarding the spread through model experimentation. I assessed the independent and interactive role of climate variables (temperature, precipitation, atmospheric CO2 concentration, and seasonality), latitudinal light regime, soil structure, and plant characteristics (tree versus grass, and deciduousness) in influencing angiosperm expansion by simulating the response of Cretaceous land cover to changes in each factor. I found that temperature and light were the most influential variables in determining angiosperm success, while plant structure and deciduousness may carry implications for early angiosperm establishment and community competition dynamics. LPJ showed great potential for refinement and effective future use in paleo-applications.
49

Phylogenetic studies in the Euasterids II : with particular reference to Asterales and Escalloniaceae /

Lundberg, Johannes, January 2001 (has links)
Diss. (sammanfattning) Uppsala : Univ., 2002. / Härtill 5 uppsatser.
50

Recherches sur les Dicotylédones apocarpiques contribution a l'étude des Angiospermes dites primitives /

Ozenda, Paul. January 1949 (has links)
Thesis--Paris, 1948. / Includes bibliographical references (p. [177]-183).

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