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Thesis (M.S.)--Miami University, Dept. of Chemistry and Biochemistry, 2003. / Title from first page of PDF document. Document formatted into pages; contains ix, 87 p. : ill. Includes bibliographical references (p. 85-87).

Viena svarbiausių augalų genetikos problemų yra jų atsparumas abiotiniams veiksniams. Tokie veiksniai kaip šaltis, ozonas ar ultravioletinė spinduliuotė sukelia oksidacinį stresą ir ROS formavimąsi augalų ląstelėse. Visi augalai turi antioksidantines sistemas, vykdančias ROS detoksikaciją. Žalioji kreisvė (Crepis capillaris L.(Wallr.)) ir atsparūs šalnoms bulvių somatiniai asimetriniai hibridai buvo tiriami atsparumui abiotiniams veiksniams, įvertinant morfometrinius, biocheminius ir genetinius rodiklius po UV-B –(2, 4, 8 kJ/m2) ir ozono (40 ir 80 ppb) poveikio. Nustatyta, kad jautrūs stresiniams veiksniams yra morfometriniai parametrai- žalia ir sausa biomasė, lapų plotas ir skaičius. Biocheminiai parametrai, tirpių baltymų kiekis ir antioksidantinio fermento superoksido dismutazės (SOD) aktyvumas, tirtuose augaluose proporcingai didėjo priklausomai nuo dozės dydžio. Padidėjęs antioksidantinio SOD fermento aktyvumas po abiotinių veiksnių poveikio vertintinas kaip augalo adaptacinis atsakas į UV-B sukeltą oksidacinį stresą. Tiriant atsparumą šalčiui nustatyta, kad atsparus šalčiui bulvių hibridas H269, įgijo iš donoro Solanum commersonii DNR fragmentą, susijusį su padidinta mitochondrijų elektronų pernašos sistemos genų raiška, kuri siejama ROS koncentracijos reguliavimu ląstelėje ir šalčio atsako genų reguliavimu branduoliniame genome. Parodėme, kad atsparumai abiotiniams veiksniams- ozonui, UV-B ir šalčiui augaluose funkcionuoja kaip vientisa gynybos sistema, apimanti... [toliau žr. visą tekstą] / One of the major issues of plant genetics is their tolerance and resistance to abiotic factors. Low temperatures, ozone and ultraviolet radiation are the factors that increase ROS formation and oxidative stress in a plant cell. All plants have effective antioxidant systems to detoxify ROS. Researches were carried out to evaluate the resistance of Smooth Hawksbeard (Crepis capillaris L. (Wallr)) and frost resistant asymmetric somatic potato hybrids to abiotic stresses, estimating the morphometrical, biochemical and genetic data after treating the plants with UV-B (2, 4, 8 kJ/m2) and ozone (40 ir 80 ppb) doses. Test data shows, that morphometrical parameters such as fresh and dry weight along with leaf area and count are very sensitive to stress factors. Biochemical parameters such as soluble protein content and the activity of antioxidant enzyme superoxide dismutase (SOD) have risen pro rata from the dose given. The increment of SOD after treating the plants with simulated abiotic factors is annotated as adaptation to UV-B stress. Analysis of the cold acclimation has shown, that potato hybrid H269 has gained DNA fragment from the donor species Solanum commersonii. This fragment is associated with over-expressed genes of mitochondrial electron transfer system which regulates the concentration of ROS in the cell and controls the expression of nuclear genes related with cold-acclimation. With this analysis we have showed that plant resistance to abiotic factors such as ozone... [to full text]

While boreal forest habitats have historically been relatively free from invasive plants, there have been recent increases in the diversity and range of invasive plants in Alaska. It is critical that we understand how disturbances influence invasibility in northern boreal forests, to avoid the economic damage other regions have experienced from invasive plants. Black spruce (Picea mariana) is the dominant forest type in interior Alaska, and wildfire is the dominant disturbance in these forests. Furthermore, disturbances in the form of management for fire suppression are common in forests close to urban areas. I surveyed recently burned, managed, and undisturbed black spruce forests for invasive plants to determine if fire and management facilitate invasive plant colonization. I also conducted an experimental seeding trial with three invasive plants common to Alaska (bird vetch (Vicia cracca), common dandelion (Taraxacum officinale), and white sweetclover (Melilotus officinalis) in burned and mature black spruce forest to determine if fire facilitates invasive plant germination. To determine the effect of substrate type on invasive plant germination, I planted seeds on a variety of substrates in the burned forest. Results indicate that fire and fire suppression treatments promote invasive plant colonization, as invasive plants were observed in burned and managed areas, but not in mature stands. Analysis of environmental data taken at survey sites indicate that fire mediates invasibility through its effects on substrate quality. In burned stands, invasive plants are most likely to colonize areas of shallow post-fire organic depth. Results from the seeding trials were consistent with results from invasive plant surveys, with reduced germination in mature compared to burned forest, and no germination on the residual organic layer in the burned forest. The highest germination occurred on mineral soil in burned forest, indicating that severe fires that combust the organic layer are likely to increase invasibility. The results of this study suggest that invasive species control efforts should be prioritized to disturbed forests, particularly areas where the disturbance has exposed mineral soil.

Objective of the work was to identify with using pollen analysis botanical origin of bee pollens. Pollen analysis consisted in the distribution of samples to individual sub-samples . Samples were weighed and a part of them was dissolved in a solution of glycerin and water. Dissolved samples were viewed under a microscope. Pollen was removed by the beekeeper Mgr .Milan Trhlín with using a device called pollen catcher. The samples were collected in the year 2011 in the spring and early summer period from beehive location on the hill Lískovec, of the protected landscape Šumava 1,8 km west of city Volary, at a time of 25. march to 24. june. Another objective of the work was with using phytocenology study, in the distance 1,5 km from the beehive habitat, evaluate the structure of plant association from the point of nutrition honeybees. The work also includes evaluation preference bees for individual plant species. There were detected, that bees prefer the plants that provide the best digest pollen and the plants which grows up to 1,5 km from beehive habitat. There were distinguised 32 types of pollen grains.

This study provides insight into the structure/function relationship between desaturases and acetylenases, and indicates amino acid residues within acetylenases which influence reaction outcome. <i>Oleate desaturases</i> belong to a family of enzymes capable of introducing cis double bonds between C12 - C13 in oleate esters. Acetylenases are a subset of oleate desaturase enzymes which introduce a triple bond in the C12 - C13 position of linoleate. To better understand which amino acids could be responsible for differentiating the activity of acetylenases from typical desaturases, a total of 50 protein sequences were used to compare the two classes of enzymes resulting in the identification of 11 amino acid residues which are conserved within either separate family but differ between the two groups of enzymes. These identified amino acid residues were then singularly altered by site-directed mutagenesis to test their role in fatty acid modification. Specifically, the wild type acetylenase, Crep1 from <i>Crepis alpina</i>, and a number of point mutants have been expressed in <i>Saccharomyces cerevisiae</i>, followed by fatty acid analysis of the resulting cultures. Results indicate the importance of 4 amino acid residues within Crep1 (Y150, F259, H266, and V304) with regards to desaturase and acetylenase chemoselectivity, stereoselectivity, and/or substrate recognition. The F259L mutation affected the acetylenase by converting it to an atypical FAD2 capable of producing both cis and trans isomers. The V304I mutation resulted in the conversion of Crep1 into a stereoselective FAD2, where only the cis isomers of 16:2 and 18:2 were produced. The Y150F mutation led to a loss of acetylenase activity without affecting the inherent desaturase activity of Crep1. The H266Q mutation appears to affect substrate selection causing an inability to bind substrate (16:1-9c and/or 18:1-9c) in a cisoid conformation, resulting in an increased accumulation of trans product. The changes in enzyme activity detected in cultures expressing Crep1 mutants demonstrate the profound effect that exchanging as little as one amino acid can have on an enzyme properties. Enzymes retain some conservation of amino acids necessary for activity, such as those involved in metal ion binding, whereas subtle changes can affect overall enzyme function and catalysis.

This study provides insight into the structure/function relationship between desaturases and acetylenases, and indicates amino acid residues within acetylenases which influence reaction outcome. <i>Oleate desaturases</i> belong to a family of enzymes capable of introducing cis double bonds between C12 - C13 in oleate esters. Acetylenases are a subset of oleate desaturase enzymes which introduce a triple bond in the C12 - C13 position of linoleate. To better understand which amino acids could be responsible for differentiating the activity of acetylenases from typical desaturases, a total of 50 protein sequences were used to compare the two classes of enzymes resulting in the identification of 11 amino acid residues which are conserved within either separate family but differ between the two groups of enzymes. These identified amino acid residues were then singularly altered by site-directed mutagenesis to test their role in fatty acid modification. Specifically, the wild type acetylenase, Crep1 from <i>Crepis alpina</i>, and a number of point mutants have been expressed in <i>Saccharomyces cerevisiae</i>, followed by fatty acid analysis of the resulting cultures. Results indicate the importance of 4 amino acid residues within Crep1 (Y150, F259, H266, and V304) with regards to desaturase and acetylenase chemoselectivity, stereoselectivity, and/or substrate recognition. The F259L mutation affected the acetylenase by converting it to an atypical FAD2 capable of producing both cis and trans isomers. The V304I mutation resulted in the conversion of Crep1 into a stereoselective FAD2, where only the cis isomers of 16:2 and 18:2 were produced. The Y150F mutation led to a loss of acetylenase activity without affecting the inherent desaturase activity of Crep1. The H266Q mutation appears to affect substrate selection causing an inability to bind substrate (16:1-9c and/or 18:1-9c) in a cisoid conformation, resulting in an increased accumulation of trans product. The changes in enzyme activity detected in cultures expressing Crep1 mutants demonstrate the profound effect that exchanging as little as one amino acid can have on an enzyme properties. Enzymes retain some conservation of amino acids necessary for activity, such as those involved in metal ion binding, whereas subtle changes can affect overall enzyme function and catalysis.