Abstract
We examined the effects of 3 rare earth elements (La, Sm and Yb) on germination of plants and AM colonization. In addition, the effects of 3 rare earth elements and arbuscular mycorrhizal (AM) colonization on plant growth were examined by a pot experiment. The results are summarized as follows.1) The effects of rare earth elements on germination were investigated by comparing the root length of germinated seeds of marigold (Tagetes patula L.), onion (Allium cepa L.) and tall fescue (Festuca arundinacea Schreb.) in quartz sand treated with La, Sm and Yb. The root length of all the plants was markedly lowered by the addition of La, Sm and Yb at the rate of 100μmol kg^<-1>. At the rate of 10μmol kg^<-1>, although the root length of marigold was not lowered, those of onion and tall fescue were slightly lowered by the addition of Yb and Sm, respectively. From the results above, it is suggested that the addition of La, Sm and Yb at the rate of 10 or 100μmol kg^<-1> probably causes the inhibition of germination. 2) The effects of rare earth elements on AM colonization were examined by use of marigold colonized by Glomus etunicatum. We found that AM colonization of marigold root was not inhibited by the addition of La, Sm and Yb at the rate of 10μmol kg^<-1>. 3) To examine the effects of AM colonization and rare earth elements on plant growth, mycorrhizal (AM fungus ; Glomus etunicatum) and non-mycorrhizal marigolds were grown for 50 d in river sand with or without application of La, Sm and Yb at the rate of 10μmol kg^<-1>. The growth of non-mycorrhizal marigold, especially aerial parts, was inhibited by the addition of La and Yb. However, the growth of mycorrhizal marigold was not inhibited by the addition of La, Sm and Yb. Therefore, AM colonization would be attributed to the amelioration of phytotoxicity of La and Yb.
