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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.
1

Ekologická studie epixylických druhů \kur{Lophozia ascendens} a \kur{Anastrophyllum hellerianum (Lophoziaceae)} / Ecological study of epixylic species \kur{Lophozia ascendens} and \kur{Anastrophyllum hellerianum (Lophoziaceae)}

HOLÁ, Eva January 2008 (has links)
Seasonal pattern and extent of asexual reproduction in liverwort species Lophozia ascendens, L. ventricosa and L. longiflora were studied in the Boubínský prales and Milešický prales old-growth forest reserves in the Šumava Mts., South Bohemia. Asexual reproduction was quantified as the number of 1{--}2 -celled gemmae produced per individual shoot. Numbers of gemmae per shoot among sampling months differed significantly as did the numbers of gemmae in samples among Lophozia ascendens, L. ventricosa and L. longiflora among sampling months. Germinability of gemmae was low in early spring, highest in August and September and slightly decreased in October. Spreading potential of gemmae was investigated in the epixylic hepatic Anastrophyllum hellerianum. Gemmae were trapped at different distances (0 {--} 10 m) and directions from the source colonies in two experiments: one was realized in the natural habitat within a forest and the other in an artificial set-up in the open habitat. Dispersal of gemmae showed slight distance dependence both in the natural and open habitats. Habitat requirements (e. g. decay degree, texture, bark cover, log diameter) of the L. ascendens and A. hellerianum were investigated in both reserves, 126 logs were found. Mostly tiny liverworts grew with L. ascendens and A. hellerianum. Both studied species occurred on logs with degree of decay 2 {--} 7 and degree of texture 2 {--} 6.
2

Frameworks for reprogramming early diverging land plants

Pollak Williamson, Bernardo January 2018 (has links)
Plant form is a product of emergent processes of cell division, patterning and morphogenesis. These fundamental processes remain poorly characterised in plants. However, engineering approaches can provide new tools and frameworks for the study and manipulation of plant development. This dissertation describes the development of engineering frameworks for reprogramming of the early diverging land plant Marchantia polymorpha (Marchantia). I describe the generation of genomic and transcriptomic datasets for Marchantia, which has provided the basis for the compilation of a gene-centric registry of DNA parts for engineering (MarpoDB). I describe the development of Loop assembly, an efficient and standardised DNA assembly system based on Type IIS restriction enzymes for recursive fabrication of DNA circuits with high efficiency. MarpoDB was used to mine new DNA parts compatible with Loop assembly which were used to generate plant transformation vectors for labelling of cellular features to study aspects of growth and development. I performed image analysis of genetic markers for segmentation and quantification of cellular properties in germinating gemmae. I implemented high-efficiency Cas9-mediated mutagenesis in Marchantia for use in functional molecular genetics studies. Furthermore, I produced inducible systems for expression of heterologous elements by transactivation which showed negligible levels of basal activity. It was possible to use this system for induction of gene expression in single cells. Finally, these new frameworks were applied to study the gametophytic meristem in Marchantia gemmae. I mapped the expression of several putative candidate homologues for higher plant meristem regulators, performed overexpression and loss-of-function studies for homologues of WUSCHEL, CLAVATA3 and SHOOT MERISTEMLESS. A strategy for misregulation of endogenous genes was developed using inducible transactivation, and was used with cellular markers for WUSCHEL and CLAVATA3 homologues in Marchantia.

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