Sürdürülebilir Yeşil Kampüs Koleksiyonu / Sustainable Green Campus Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7755

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2002 - 200912010 - 20181

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Subject: search.filters.subject.Selenium

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  • Master Thesis
    Elecidation of Selenium Tolerance Mechanisms in Puccinellia Distans (jacq.) Parl, Using a Transcriptomic Approach
    (Izmir Institute of Technology, 2018) Kök, Aysu Başak; Frary, Anne; Eroğlu, Seçkin
    Selenium (Se) has a versatile chemistry. Therefore, it is present in a wide variety of materials on Earth. Although it is not an essential element for plants, Se provides several survival and ecological advantages. Puccinellia distans (P.distans) is weeping alkali grass which has a relatively fast growth rate and produces a large biomass. It can also hyperaccumulate extreme concentrations of boron and tolerate high levels of salinity. It is known that some plant species can tolerate high concentrations of soil salts and boron while hyperaccumulating Se in their leaves. Therefore, in this study, the Se accumulation and tolerance capacity of P. distans were investigated, and the plant’s Se tolerance mechanism was elucidated using a transcriptomic approach. The results of this study indicated that P. distans accumulated more than 100 mg Se kg-1 in its shoots. Therefore, P. distans was discovered to be a novel Se accumulator plant. Biochemical analyses and RNA sequencing results helped us to decipher the Se tolerance and accumulation mechanism of P. distans. Accordingly, the tolerance mechanism was found to be associated with the upregulation of genes involved in sulfate, selenocompound and antioxidant pathways. Here, we suggest that upregulation of Se assimilation and stress responses genes may have been due to induction of jasmonic acid signaling. In addition, we propose that the cell wall may play an important role in restriction of Se movement to the cytoplasm. Also, we put forward that sequestration of selenate inside the vacuole may be a way that Se accumulates in cells.
  • Master Thesis
    B and Se Transport Modeling in Saturated/Unsaturated Zones
    (Izmir Institute of Technology, 2002) Yüreklitürk, O. Emin; Tayfur, Gökmen
    There has been renewed interest in the application of models to the transport of non-point source pollutants. However, very little work has been done to evaluate the performance of a functional transient-state model for the transport of a reactive solute over an extensive study period. This research consists of mathematical modeling to simulate water flow, boron and selenium transport through soil in tile-drained croplands.For Boron part a mathematical model was developed to simulate non-conservative boron transport. The dynamic two-dimensional finite element model simulates water flow and boron transport in saturated-unsaturated soil system, including boron sorption and boron uptake by root-water extraction. Two different models have been employed for the sorption of boron. Similarly, for selenium part a finite element model is developed to simulate species of selenium transport in two dimensions in saturated/unsaturated zones. The model considers water, selenate, selenite and selenomethionine uptake by plants. It also considers oxidation/reduction, volatilization, and chemical and biological transformations of selenate, selenite, and selenomethionine. Comparison of boron transport model results with observed data is satisfactory. The model employed with Langmuir isotherm was found to give slightly better simulation results when compared with the model employed with Freundlich. The sensitivity analysis results indicate that the irrigation scheduling and the irrigation water quality are very important parameters for boron accumulation in the soil. Also the adsorption isotherm parameters, which reflect us the soil properties, are found to be important for the boron movement in the soil. Comparison of selenium transport model with observed data is not quite satisfactory in accuracy when compared with the model for boron transport. This may be the result of the complexity of the mechanisms affecting the selenium transport in soil. There are too many parameters, and due to the errors depending on the parameters, the total error for the estimation of the total selenium increases.