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Lateral root and their origin
Nováková, Hana ; Soukup, Aleš (advisor) ; Sekereš, Juraj (referee)
The origin of lateral roots is one of the determinants of the structure of the overall architecture of the root system of plants. Individual plant species differs in point of initiation of lateral roots in the longitudinal and transverse plane of the parent root. This paper briefly summarizes the findings relating to the establishment and development of lateral roots in the model of plant Arabidopsis thaliana and on the sample of several species of ferns and monocots and dicots of literature outlines the variability that manifests itself especially during initiation of lateral roots. The ferns initiation site located in the endodermis of the parent root, for other species to form the lateral root primordium of pericycle cells that are found in a certain position in relation to vascular elements in the central cylinder of the parent root. Another highly variable factor in the development of lateral root initiation site is the distance from the root apical meristem, which is related to the place of the auxin signal competent cells and also the rate of growth and progress of cells from the parent root apical meristem. Powered by TCPDF (www.tcpdf.org)
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Mechanisms of exodermal response to nutrient availability in the environment
Gargoš, Ondřej ; Tylová, Edita (advisor) ; Kummerová, Marie (referee)
in English The apoplastic barriers of the root (endodermis and exodermis) represent an important regulatory mechanism for the uptake of water and nutrients from the environment, ensuring its selectivity. In addition, both layers respond to stress factors by altering its rate and degree of cell wall modification, which affects the transport properties of the root and represents adaptive plants to high heterogeneity of the soil environment. Apoplastic barriers also respond to the availability of mineral nutrients. This issue has recently been intensively studied and a number of ambiguities persist. Interestingly, the deficiency of some mineral nutrients stimulates the differentiation of barriers, while the deficiency of other mineral nutrients delays the differentiation. In addition, different plant species react differently to the deficiency of the same element. Another interesting aspect is the fact that the reaction of the endodermis and exodermis is localized and takes place mainly in that part of the root system which is directly exposed to the stress factor. This phenomenon has been observed with cadmium toxicity, but more recently with local nutrient deficiencies (nitrogen and potassium) in Zea mays. This diploma thesis deals with the functional significance of localized enhancing or delaying...
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Function study of EXO70H7 and EXO70H8 genes in Arabidopsis thaliana development.
Modráčková, Jana ; Kubátová, Zdeňka (advisor) ; Soukup, Aleš (referee)
Complex Exocyst consists of eight proteins and it is known as a Sec6/8. Its composition is evolutionarily highly conserved amongst all the species. This complex is involved in vesicle trafficking as a part of attaching mechanism to a specific place on the plasma membrane. EXO70 subunit has been found in 23 copies in Arabidopsis thaliana genome. In this study we have been examine paraloges EXO70H7 and EXO70H8. There have been suggestions that these genes are important in development of roots according to the previous studies. We have not been able to identify any significant phenotype within the mutant plants in these genes. There has been studied other mutant appearance during the stress experiments. Most of these experiments did not identify any divergence. Only experiments with germination during stress conditions revealed significantly worse germination of exo70H7 mutant seeds on the medium containing sorbitol. This suggests that mutant seeds have a worse protection against osmotic stress. Significantly worse germination of exo70H8 seeds on the medium with excess NaCl indicates that these seeds incriminate to higher absorption of sodium ions. Analysis of the cell localization of GFP constructs brought knowledge of appearance EXO70H7 and EXO70H8 proteins. EXO70H7 locates in the cytoplasm and in...
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Cellular mechanisms of differentiation of root apoplastic barriers
Namyslov, Jiří ; Tylová, Edita (advisor) ; Konrádová, Hana (referee)
Apoplastic barriers (exodermis and endodermis) are primarily used to regulate the free movement of substances within apoplast due to modifications of cell walls. While at the anatomical level, the barriers are studied for a long time, only recently the molecular mechanisms that are behind the emergence of these modifications are gradually identified. The most important modifications are Casparian strips that fill the space between the adjacent cells in exodermis and endodermis. Casparian strips are lignin-based structures formed with the help of CASP proteins located in equatorial region of plasmalema (called CSD membrane domain). In addition to CASP proteins, the formation of Casparian strip involves activity of site-specific enzymes of lignin synthesis (PER64 peroxidase, NADPH oxidase RBOHF). In these cell layers shortly after differentiation of Casparian strips, the deposition of suberin occurs between plazmalema and primary cell wall leading to formation of suberin lamellae also serving to block the apoplast. Next step of differentiation is the formation of U-shaped tertiary thickenings that are formed by deposition of secondary cell wall, whose formation mechanism in the root endodermis is not yet well-known. Processes responsible for formation of apoplastic barriers are thus related to the...
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Phylogenic and developmental plasticity of structure of endo and exodermis in roots of higher plants
Szutkowská, Veronika ; Soukup, Aleš (advisor) ; Srba, Miroslav (referee)
Root endodermis and exodermis form apoplastic barriers for the movement of water and solutes into and out of the plant root system. Both layers have modified cell walls with Casparian strips. They often develope suberin lamela as a secondary development stage and thickened cellulose, sometimes lignified, wall as a tertiary development stage. Endodermis, as the innermost layer of cortex, is generally present in all vascular plant roots except Lycopodium. It is very phylogenetically and developmentally stable and in most cases single-layered. Exodermis can be often multi-layered or dimorphic and is formed on the periphery of the root. This layer can be found in a large number of angiosperms but according to the data gathered so far it seems that most of the seedless plants and gymnosperms lack it. Its presence correlates with the environmental conditions in which plants grow and its high structural and developmental plasticity helps roots to resist stress conditions such as drought, salinity, anoxic conditions and the presence of toxic substances. This paper aims to summarize the current knowledge of interspecies variability and developmental plasticity of endodermis and exodermis in roots of vascular plants.
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Lateral root and their origin
Nováková, Hana ; Soukup, Aleš (advisor) ; Sekereš, Juraj (referee)
The origin of lateral roots is one of the determinants of the structure of the overall architecture of the root system of plants. Individual plant species differs in point of initiation of lateral roots in the longitudinal and transverse plane of the parent root. This paper briefly summarizes the findings relating to the establishment and development of lateral roots in the model of plant Arabidopsis thaliana and on the sample of several species of ferns and monocots and dicots of literature outlines the variability that manifests itself especially during initiation of lateral roots. The ferns initiation site located in the endodermis of the parent root, for other species to form the lateral root primordium of pericycle cells that are found in a certain position in relation to vascular elements in the central cylinder of the parent root. Another highly variable factor in the development of lateral root initiation site is the distance from the root apical meristem, which is related to the place of the auxin signal competent cells and also the rate of growth and progress of cells from the parent root apical meristem. Powered by TCPDF (www.tcpdf.org)
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