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Arzen (As) je za rastline in živali potencialno strupen. Zaradi kemične podobnosti z rastlinam dostopno obliko fosforja, As lahko vstopa v korenine in je znotraj rastline mobilen. Tako se lahko kopiči tudi v užitnih delih in se vključi v prehranjevalno verigo ter ogroža zdravje ljudi. Ena od rastlin, ki predstavlja tveganje za vnos As v človeško telo, je tudi rastlina arašida (Arachis hypogaea L.), ki predstavlja pomemben pridelek v provinci Córdoba v Argentini, kjer več pridelovalnih območij vsebuje visoko koncentracijo As. Zaradi občasne poplavljenosti kmetijskih površin, pa se možnost kontaminacije rastlin z As še poveča. Namen magistrskega dela je bil preučiti porazdelitev As v različnih delih rastline arašida ter določiti tkivno-specifično lokalizacijo As v koreninah in nodulih v poplavljenih in nepoplavljenih pogojih. Z metodo rentgenske fluorescenčne spektrometrije (XRF) smo največjo koncentracijo As izmerili v koreninah, sledili so noduli, najnižjo koncentracijo pa smo izmerili v steblih in listih. Z metodo z delci inducirane emisije rentgenskih žarkov (mikro-PIXE) smo določili tkivno-specifično lokalizacijo As. V nodulih nismo opazili tkivno-specifičnega kopičenja As. V koreninah je bilo večina As nakopičenega v določenih delih žile, kjer smo opazili kolokalizacijo As in žvepla (S) kar nakazuje na tvorbo kompleksov As s tiolnimi skupinami peptidov, kar verjetno omejuje mobilnost As v rastlini. Poplavljanje ni vplivalo na privzem As, smo pa opazili nastanek železove oborine na površini korenin kar predstavlja bariero na katero se je adsorbiral As. Predlagani strategiji za zmanjšanje privzema in prenosa As do nadzemnih delov rastline bi torej bilo dodajanje S v obdelovalne površine ter omejevanje poplavljanja, vendar bi bilo učinka teh dveh dejavnikov na rastline arašidov v prihodnosti potrebno še bolj podrobno raziskati. Arsenic (As) is potentially toxic to plants and animals. Because of its chemical similarity to the plant-available form of phosphorus, As can be taken up by roots and transported within the plant. It can thus accumulate in edible plant parts and enter the food chain, posing a risk to human health. One of the plants that causes a risk of As intake is peanut (Arachis hypogaea L.), which is an important crop in the province of Córdoba, Argentina, where several cultivated areas contain high background concentrations of As. In addition, occasional local flooding episodes further aggravate the As-contamination problem. The aim of this thesis was to evaluate the uptake and partitioning of As in the peanut plant and to determine the tissue-specific localisation of As in roots and nodules under flooded and non-flooded conditions. Using X-ray fluorescence, the highest concentration of As was measured in roots, followed by nodules, and the lowest concentration was measured in stems and leaves. Tissue-specific localisation of As was determined using micro-particle-induced X-ray emission. No tissue-specific accumulation of As was observed in nodules. In roots, most As was accumulated in specific parts of the vascular tissue, where we observed co-localisation of As and sulphur (S), suggesting the complexation of As with sulphydryl groups of peptides, which presumably limits As mobility within the plant. Flooding did not affect As uptake but resulted in the formation of iron-plaque on the root surface, which represents a barrier to which As can be adsorbed. The proposed strategies to reduce the uptake and transport of As to the aerial parts of the plant are thus the supplementation of peanut crop with S and flooding management. Further, ideally field investigations are required to determine these two potential practices as efficient in a realistic agricultural situation. |
