In this study, the bioaccumulation and toxicity of neodymium （Nd） in pla-narian Dugesia japonica were investigated. The results showed that with the in-creasing dietary Nd supplementation, the concentration of Nd in the planarian showed a significant linear increase and the balance of mineral elements was bro-ken with the decrease of Ca, Fe and Mo, and the increase of K and Mg. The content of soluble proteins and the activities of superoxide dismutase （SOD） and catalase （CAT） decreased with the increase of Nd concentration, while the content of H2O2 rose gradual y. The mortality was directly proportional to the Nd concentra-tion. The results indicated that planarian is a very sensitive aquatic animal to Nd contamination and can be an indicator organism for Nd pol ution.
Arabidopsis thaliana seedlings were cultivated in 0-500 μmol/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 ofA. 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. Ultrastructural analysis revealed that Ce was mainly distributed on the cell wall. At higher concentration, Ce could also enter cell, destroy the ultrastructure of cells and disturb the intrinsic balance of nutrient elements of A, thaliana, Addition of Ce （50-500 μmol/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 （0.5 μmol/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.
[Objective] This study aimed to investigate the physiological and biochemi- cal effects of lanthanum （La3＋）, cerium （Ce3＋）, zinc （Zn2＋） on rice roots and explore the environmental effects of excessive application of rare earth. [Method] By using rare earth elements La3＋ and Ce3＋, and nutritional and toxic heavy metal element Zn2＋ as stress factors, the effects of these three elements on the germination of rice seeds, growth and development of seedlings were studied and compared by using tissue culture method. [Result] La3＋, Ce3＋ and Zn2＋ had no significant effect on germi- nation rate of rice seeds but significant inhibition effects on the growth of roots and shoots of rice seedlings, and the inhibition effects of rare earth elements in high concentrations were stronger than Zn2＋; the content of soluble protein in rice roots showed a rising-decreasing trend with the increasing concentrations of three metal ions, La3＋ and Ce3＋ were more sensitive than Zn2＋; the activities of CAT and POD increased with the increasing concentrations of La3. and Ce3＋, while the SOD activity had shown the tendency of decreased first and increased later; the three metal ions all could significantly stimulate the rapid accumulation of MDA in rice roots. La3＋ and Ce3＋ had stronger toxic effects at high concentrations than Zn2＋, [Conclusion] Toxic mechanism of rare earth elements La＋ and Ce3. is similar to that of heavy metal el- ement Zn2＋. Rare earth might become a new type of pollution in the long run.
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
[Objective] The aim of this study was to explore the physiological and biochemical responses of Chinese cabbage to La and Zn. [Method] The effects of La and Zn on seed germination and seedling growth were explored by tissue culture method. [Result] La and Zn had little effects on seed germination rate, but significantly inhibited the growth of root and seedling, decreased their fresh weight at higher concentration; the inhibition of La proved higher on Chinese cabbage. The contents of chlorophyll and soluble protein increased at lower concentrations of La and Zn, but decreased at higher concentrations. With increasing doses of La and Zn, the activities of CAT and POD rose gradually, while SOD activity decreased at lower doses and increased at higher doses. Both of La and Zn would promote Of. producing and MDA accumulation. [Conclusion] In higher concentration, La was more poisonous than Zn. It is clear that the poisonous mechanism of La is similar to that of Zn. Hence, La is possibly a kind of new pollutant.
