Idrija is a small city known for its continuous five-hundred-year long mercury (Hg) mining. During the process, a quarter of the processed Hg was released in the surrounding environment, which had and is still having a negative impact on the local organisms. Plants are first in direct contact with the soil and they can as a primary source of nourishment to people and animals, transfer the accumulated Hg from the ground and air to the food chain. The goal of this master thesis was to investigate how the secondary metabolites (polyphenolic compounds) of the common (Fagopyrum esculentum) and Tartary (Fagopyrum tataricum) buckwheat affect the transfer and effects of Hg in combination with selenium (Se) in plants and further on through the food chain. Secondary metabolites are the main components of defence mechanisms against oxidative stress, which can be caused by different environmental conditions, such as UV radiation, metals or microorganisms. In contact with the organism, they can form reactive oxygen compounds (ROS) and can therefore damage cellular structures. It is known that the Tartay buckwheat has higher antioxidant potential than common buckwheat. This can be attributed to the higher content of some flavonoids, which prevent oxidative stress by catching free radicals and greater reducing power. Selenium also has a positive influence on the growth and survival of plants and on the defence against oxidative stress, because it can react with Hg and reduce negative effects of Hg on plants. As test plants a common and Tartary buckwheat were used and as a test animal the snail, Spanish lazarus (Arion vulgaris) was used. Common and Tartary buckwheat were grown in the soil, contaminated with Hg. Half of them were foliarly enriched with Se, which was applied as a prepared solution of dipotassium selenate (K2SeO4). The effects of Hg accumulation (in combination with Se) on the content of photosynthetic pigments, level of lipid peroxidation and the content of polyphenolic compounds in the common and Tartary buckwheat were spectrophotometrically measured. The grown plants were used to feed the snails from the family Spanish Lazarus (Arion vulgaris). With the use of X-Ray fluorescent spectrometry, we defined to what extent the buckwheats accumulated the Hg and Se from the plant material. The level of lipid peroxidation of the digestive gland and muscle tissue in snails was spectrophotometrically defined. The results showed that the combination of Hg and Se had a different effect on the physiological properties on both types of buckwheat. Both species of buckwheat in combination with Se accumulated Hg differently. The transport of Hg along the food chain was in combination with Se specific to the species. Because plants were grown under controlled conditions, there was no significant difference in the antioxidant potential between the two species and no antioxidants effects on the snail’s tissue in the presence of Hg were observed. Mercury has mostly accumulated in the roots of common and Tartary buckwheat and in the digestive gland of the Spanish Lazarus snails, while Se accumulated in the sprouts of the common and Tartary buckwheat and in muscle tissue of the Spanish Lazarus snails.
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