Abstract: Selenium (Se) is an essential trace element for human and animals, and it may be beneficial to increase Se content of tobacco (Nicotiana tabacum L.), but the relationship between Se availability and forms in soil for plant growth had been rarely reported so far. In order to understand the relationship between the Se content in tobacco and soil, and to develop Se-enriched tobacco, we performed a pot experiment using cultivar NC89 with natural Se-enriched and Se-supplied soil treatments. The Se content in seedlings and the Se forms in rhizospheric and nonrhizospheric soil were analyzed. The results showed that selenium content was higher in roots than in shoots of tobacco at seedling stage; it increased both in roots and shoots of tobacco with increase of Se level in natural Se-enriched soil, and there was a significant correlation between Se content and soil Se applications. In natural Se-enriched soil, the residual Se (Res-Se) content was the highest which accounted for more than 2/3 of the total Se in middle and high Se-enriched soil, while in Se-supplied soil, the content of extractable Se with KH₂PO₄ (KH₂PO₄-Se) was the highest which accounted for 43%–46% of total Se and was significantly correlated to Se content in tobacco. Both in natural Se-enriched and Se-supplied soil, content of extractable selenium with K₂SO₄ (K₂SO₄-Se) was the least which was less than 1% of total selenium, but the contents of total selenium, KH2PO4-Se and NH₃·H₂O-Se were significantly higher in rhizospheric soil than in nonrhizospheric soil. In Se-supplied soil, the percentage of NH₃·H₂O-Se was higher and the percentage of Res-Se was lower in rhizosphere than in nonrhizosphere. Our experiment showed that tobacco could accumulate Se well from soil, and absorb Se easier from Se-supplied soil than natural Se-enriched soil. The rhizosphere of tobacco, where distributed more available Se, can promote the formation of NH₃·H₂O-Se and reduce the Se fixation with minerals in soil, therefore increase Se availability in soil.

Key words: Nicotiana tabacum L., Seedling stage, Natural Se-enriched soil, Se application in soil, Rhizosphere, Se form