Bioaccumulation, subcellular distribution and chemical forms of yttrium in rice seedling

Yttrium（Y） accumulation in soil is a serious environment problem in China. To understand the mechanisms involved in Y tolerance and detoxification in rice seedling, the bioaccumulation, subcellular distribution, and chemical forms of Y was investigated in the present study. The results show that the content of Y both in roots and shoots increases with the increasing concentration of Y, and a large amount of Y is stored in roots. Subcellular distribution of Y in rice indicates that the majority of Y is bound to cell wall. Meanwhile, various chemical forms of Y is absorbed by rice. The greatest amount of Y is extracted by 2% hydrate acetic acid（HAc） and 0.6 mol/L HCl（particularly 2% HAc）, which indicates that most of Y is combined with un-dissolved phosphate and oxalate（particularly phosphate）. Cluster analysis, based on Y abundance levels, reveals the relationship between Y distribution patterns and chemical forms. Our results imply that Y forming of precipitates with phosphate（and/or oxalate） and depositing in the cell wall may be a key strategy for Y detoxicity and tolerance in rice.