The results relating to the selenium applied as micro-fertilizer in order to increase its content in some medicinal plants (nettle, chamomile, peppermint, and marigold) are presented in this paper.
The research was carried out through the field experiment conducted on humoglay soil at the Experimental stationof the Institute for the medicinal plant research in Pančevo. The selenium was applied in the following doses: 0, 50, 500 and 1000 g/ha, with the usual argotechnique for the medicinal plants production in our country. Each variant was replicated three times, while the area of each parcel was 9 m2. Selenium was applied in a form of Na2SeO4 solution, uniformly spread over soil and plants at the early vegetation phases.
Since the soil where experiment was conducted, as well as the most soils in FR Yugoslavia, has a very low selenium content (0.2 ppm), its content in control variant in each one of the four grown medicinal plant species was lower then optimal and ranged from 0.04 to 0.07 ppm. The optimal Se level was obtained even with the lowest dose of applied Se (50 g Se/ha) in chamomile, peppermint and marigold. It ranged from 0.2 to 0.5 ppm. The greatest response was noticed for nettle plants, where the toxic Se level (about 12 ppm) was found. The selenium content in all four grown species increased with the increment of Se dose. It was the highest in nettle (95 ppm) and the lowest in the marigold (4.5 ppm). Rapid decrease of Se content in the plants was noticed for the second and the third harvest, due to its little residual effect, caused by leaching and evaporating losses.
The grown medicinal plants had taken 0.5-2.0% of the applied selenium, 30% remained in the soil plow layer (0-30 cm), while 70% have been subjected to losses.
The accumulated Se was found to be in the organic compounds (proteins), since none of the inorganic Se was obtained by the analysis of water extracts. Much more Se was extracted by hot water (tea making procedure) compared with alcohol (ethanol). The highest Se extraction was obtained for chamomile (30%) and then for peppermint (26%) and nettle (11%). The percentage of extraction in ethanol ranged from 2.7 to 7.5.
Such extracts could be used for human supply with selenium, while ground nettle could be used for enrichment of animal food.
Key words: selenium, chamomile, nettle, peppermint, marigold, extracts, tea.