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 hyperaccumulators is the key to developing practical phytoremediation methods.
This study aims to select or develop hyperaccumulators 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 hyperaccumulators for Cs, Sr and I fromcrops and wild plants, and to employ a genetic approach to develop transgenic plants using genes controllingCs resistance in Arabidopsis mutants.
Several crops were selected as candidate accumulators of each element according to their ability toremove the element when the plants were cultivated in an experimental field by conventional practice. The
selected candidate Cs accumulators were Portulaca oleracea, Amaranthus hypochondriacus, Helianthus
annuus and Lactuca sativa var. angustana. The candidate Sr and I accumulators were Amaranthus
hypochondriacus and Helianthus annuus. Those candidates will be examined further for removal of theelements under different cultivation conditions in the experimental field. The best accumulator for eachelement will then be selected based on the removal results.
Eight wild plants were selected by analysis results with ICP-MS after screening of 282 species by X-ray
fluorescence analysis. Those plants will be cultivated in the experimental field and their removal of the target
elements from soil will be checked.
For a genetic approach, thirteen lines of Cs-resistant Arabidopsis mutants have already been established.
The causative genes of two lines of the mutants were identified. The causative genes of the CsR33 andCsR80 lines were a chloroplast signal recognition particle subunit (cpSRP54) gene and glutamyl-tRNA
reductase (HEMA1) gene, respectively. Since the causative genes are related to chlorophyll synthesis andmost of the mutants showed yellowish leaves, Cs-resistance was considered to be linked to chlorophyll
metabolism. Arabidopsis knockout mutants of chlorophyll synthesizing enzyme genes were examined for
Cs resistance, and six knock-out lines were found to have it.

Removal of Cs per unit landarea （μg m-2)

60Cs
40

200A B C D E F G H I J K L M N O P Q R S T

A : Portulaca oleracea var. sativa 'Suberihiyu'
B : Amaranthus hypochondriacus 'Amaransasu. taiwan'
C : Helianthus annuus 'Himawari'
D : Amaranthus hypochondriacus 'Amaransasu. nagano'
E : Amaranthus hypochondriacus 'Amaransasu. ichinohe'
F : Amaranthus tricolor 'Amaransasu.'
G : Lactuca sativa var. angustana 'Kakichisha. red'
H : Brassica rapa var.amplexicaulis 'Santousai'
I : Kochia scoparia 'Houkigusa'
J : Celosia argentead 'Keitou. kurume'

Removal of Cs per unit land area in an experimental field by 20 crops.

Removal of Sr per unit landarea （mg m-2)

Fig. 1

K : Lactuca sativa var. angustana 'Kakichisha.green'
L : Thymus vulgaris 'Taimu'
M : Amaranthus hypochondriacus 'Amaransasu. summer red'N : Brassica rapa 'Kabu. tsugarubeni'O : Brassica rapa 'Kabu. atsumi-kabu'
P : Celosia argentead 'Keitou. candle'
Q : Brassica oleracea var. gongylodes 'Kôrurabi. purple bird'
R : Perilla frutescens var.crispa 'Siso. ao-chirimen'
S : Cucubita maxima 'Kabocha'
T : Brassica napus var.napobrassica 'Kabu. rutabaka'

150

Sr
100

500

A B C D E F G H I J K L M N O P Q R S T

A : Helianthus annuus 'Himawari'
K : Brassica oleracea var.gongylodes ' Kôrurabi. gland duke'
B : Amaranthus tricolor 'Amaransasu.'
L : Celosia argentead 'Keittou. kurume'
C : Amaranthus hypochondriacus 'Amaransasu. taiwan'
M : Perilla frutescens var.crispa 'Siso. ao-chirimen'
D : Amaranthus hypochondriacus 'Amaransasu. nagano'
N : Brassica rapa ' Kabu. ayameyuki'
E : Brassica rapa var. amplexicaulis ' Santousai'
O : Celosia argentead 'Keitou. candle'
F : Brassica napus var.napobrassica 'Kabu. rutabaka'P : Raphanoth sativus 'Daikon. milano-daikon'
G : Brassica oleracea var. gongylodes 'Kôrurabi. purple bird' Q : Brassica rapa 'Kabu. tsugarubeni'H : Amaranthus hypochondriacus 'Amaransasu. summer red' R : Raphanoth sativus ' Daikon. aokubi-daikon'
I : Brassica napus ' Kabu. turnip'
S : Portulaca oleracea var. sativa 'Suberihiyu'
J : Amaranthus hypochondriacus 'Amaransasu. ichinohe'
T : Hyssopus officinalis 'Hisoppu'

Fig. 2

Removal of Sr per unit land area in an experimental field by 20 crops.
Removal of I per unit landarea （mg m-2)

600I
4002000A B C D E F G H I J K L M N O P Q R S T

A : Helianthus annuus 'Himawari'
B : Amaranthus hypochondriacus 'Amaransasu. summer red'C : Amaranthus hypochondriacus 'Amaransasu. taiwan'
D : Thymus vulgaris 'Taimu'
E : Amaranthus tricolor 'Amaransasu.'
F : Agastache urticifolia ' Agasutâshe. butterfly blue'
G : Amaranthus hypochondriacus 'Amaransasu. nagano'
H : Echinochloa esculenta ' Hie. yariko-hie'
I : Amaranthus hypochondriacus 'Amaransasu. ichinohe'
J : Ocimum basilicum ' Suîto bagiru'

Fig. 3

K : Cucubita maxima 'Kabocha'
L : Perilla frutescens ' Egoma. siro-egoma'
M : Portulaca oleracea var. sativa 'Suberihiyu'
N : Hyssopus officinalis 'Hisoppu'
O : Agastache rugosa 'Agasutâshe. golden jubilee'
P : Brassica rapa var. amplexicaulis ' Santousai'
Q : Sorghum bicolor 'Morokosi'
R : Stipa tenuissima ' Sutipa. pony tail'S : Raphanoth sativus 'Daikon. milano-daikon'
T : Brassica rapa ' Kabu. ayameyuki'

Removal of I per unit land area in an experimental field by 20 crops.