Research on Element-accumulating Capacity of Plants
Mutsumi YAMAGAMI, Masumi YANAI, Shun’ichi HISAMATSU
Department of Radioecology
Abstract
Phytoremediation is a possible countermeasure against soil contamination with radionuclides.
Identifying and establishing accumulators is the key to developing practical phytoremediation methods. This
study aimed at selecting or developing accumulators usable for radionuclides that could potentially bereleased in Aomori Prefecture due to the location of a nuclear fuel reprocessing facility there. For that
purpose, we focused on the following two approaches: to search for accumulators for Cs, Sr and I from crops
and wild plants, and to employ a genetic approach to develop transgenic plants using genes controlling Cs
resistance in Arabidopsis mutants.
The candidate accumulators, in FY 2008, Amaranthus hypochondriacus, Helianthus annuus andPortulaca oleracea were selected from crops based on their removal capacity of the target elements fromsoil. In FY 2009, they were cultivated in an experimental field with different planting densities to establish
the optimal cultivation condition. The suitable planting density was determined for each candidate from theanalysis of the plants harvested.
To search for candidate accumulators from wild plants, 44 species were cultivated in the same
experimental field, and removal rate of Cs, Sr and I per unit land area were obtained from their elemental
content and planting density. The selected candidate Cs accumulators were Amaranthus retroflexus andAmaranthus caudatus. Persicaria lapathifolia was also selected as the candidate accumulator of Sr and I.
Those candidates will be examined further for establishing the optimal cultivation condition. The best
accumulator for each element will then be selected based on the removal results.
We have already reported that the causative genes of CsR33 and CsR80, which are Cs-resistant mutantlines, were found as a chloroplast signal recognition particle subunit (cpSRP54) gene and a glutamyl-tRNA
reductase (HEMA1) gene, respectively. In FY 2009 work, we found that the mutation sites of CsR33 andCsR80 were located near the p-loop domain in the cpSRP54 gene and the t-RNA/NADP binding domain inthe HemA1 gene, respectively. Uptake capacity of Cs was also examined for the two lines with different Cs
concentrations in cultivating medium. The Cs uptake capacity of CsR33 was similar to that of the wild typestrain, while that of CsR80 was three times higher than the wild type strain.
We previously identified AtCNGC17 as a gene of Cs transporter. We tried to overexpress AtCNGC17 inCsR33 and CsR80 to produce Cs accumulator. In FY 2009, we produced the transgenic plants of CsR33 andCsR80 by the gene transfection method of AtCNGC17, and we will examine their Cs uptake capacity next.

Rubia argyi (H.Lév. et Vaniot) H.Hara ex Lauener
Arabis stelleri DC. var. japonica (A.Gray) F.Schmidt
Boehmeria silvestrii (Pamp.) W.T.Wang
Laportea cuspidata (Wedd.) Friis
Schoenoplectus tabernaemontani (C.C.Gmel.) Palla “Rokkasho”
Schoenoplectus tabernaemontani (C.C.Gmel.) Palla “Mutsu”
Schoenoplectus sp.
Lactuca indica L.
Ambrosia trifida L.
Sonchus asper (L.) Hill
Cichorium intybus L.
Galinsoga quadriradiata Ruiz et Pav.
Sonchus brachyotus DC.
Tagetes patula L.
Artemisia princeps Pamp.
Verbascum blattaria L.
Lysimachia clethroides Duby “Oohata”
Lysimachia clethroides Duby “Rokkasho”
Lysimachia japonica Thunb.
Tetragonia tetragonoides (Pall.) Kuntze
Portulaca oleracea L.
Portulaca oleracea var. sativa
Portulaca pilosa L. subsp. grandiflora (Hook.) R.Geesink
Persicaria lapathifolia (L.) Delarbre
Persicaria orientalis (L.) SpachRumex japonicus Houtt.
Persicaria thunbergii (Siebold et Zucc.) H.Gross
Chamaesyce nutans (Lag.) Small
Nicotiana x sanderae Hort. ex Sander
Amaranthus retroflexus L. “Hashikami”
Amaranthus retroflexus L. “Hachinohe”
Achyranthes bidentata Blume var. japonica Miq.
Amaranthus caudatus L.
Cayratia japonica (Thunb.) Gagnep.
Phytolacca acinosa Roxb.
Amaranthus hypochondriacus L.‘ichinohe’(mg m-2)(mg m-2)(μg m-2)

Removal of Cs per unit land area

Removal of Sr per unit land area
Removal of I per unit land area

400300400

Cs

200

1000600

Sr200064I

20Fig. 1
Removal of Cs, Sr and I per unit land area in an experimental field