Arabidopsis thaliana seedlings were cultivated in 0-500μmol/L of extraneous cerium(Ce)for 7 d to investigate the toxicity,uptake and translocation of rare earth elements(REEs).The results showed that Ce could be largely absorbed by the roots of A.thaliana and translocated to the shoots.But the uptake rates of Ce by the roots were much higher than the translocation rates from roots to shoots.Ultra-structural analysis revealed that Ce was mainly distributed on the cell wall.At higher concentration,Ce could also enter cell,destroy the ultra-structure of cells and disturb the intrinsic balance of nutrient elements of A.thaliana.Addition of Ce(50-500μmol/L)to the culture medium significantly inhibited the elongation of primary roots,decreased chlorophyll content,rosette diameter and fresh mass of plants.The damage increased with the increase of Ce concentration in culture medium,although primary root elongation,chlorophyll content,and rosette diameter were stimulated by relatively low concentration(0.5μmol/L)of Ce.Thus,it is speculated that REEs may become a new type contamination if we don't well control the release of REEs into the environment.
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.
Shengnan ZhengCaiyun ZhangKailun ShiJinxiao WangGuanjun SunQiaochu HuFengyun ZhaoXue Wang
