烤烟苗期含硒量和根际硒形态的研究

以烤烟品种NC89为试材, 通过天然含硒和低硒土施硒处理的盆栽试验，对烤烟苗期含硒量和根际-根外土壤硒的存在形态进行了分析。结果表明，烤烟苗期根系含硒量高于地上部，并随天然含硒和施硒量的增加而增加，且与施硒量呈极显著的正相关。天然含硒土中，残渣态硒（Res-Se）占2/3以上，而低硒土施硒下，KH₂PO₄-Se所占比例最大。无论天然含硒土还是施硒低硒土，水溶性硒（H₂SO₄-Se）所占比例均不到1%，而根际土壤总硒、KH₂PO₄-Se和NH₃·H₂O-Se的含量均高于根外土。土壤施硒处理的NH₃·H₂O-Se占总硒的比例高于根外土壤，而Res-Se所占比例低于根外土。由此可见，烤烟能够富集土壤中的硒，天然含硒土和低硒土施硒的硒形态分布不同，施硒土壤硒的有效性高于天然含硒土，烤烟根际硒的有效性高于根外土，烤烟根际通过促进有机态硒的形成而减少土壤矿物对硒的固定来提高土壤施硒的有效性。

Selenium Content in Seedling and Selenium Forms in Rhizospheric Soil of Nicotiana tabacum L.

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.