Fujita Technical Research
ReportNo.55 2019

Development of Plant for Practical Cd Phytoextraction
on Agricultural Land

Nobuyuki Kitajima
Abstract
This report shows, the process of developing a phytotechnology-based countermeasure to lower therisk of cadmium in the agricultural land.
The three hazardous substances, cadmium, copper, and arsenic had been determined in Japanese
act for an agricultural land.
The risk management for the contaminated agricultural land requires the widely applicablecountermeasures including continuous implementation of the existing countermeasures, e.g. soil
dressing, well controlled irrigation procedure, maintaining adequate soil pH, and additional
introduction of technique recently developed to reduce the concentration of the hazardous
sub-stances.
In Japan, the phytoextraction of Cd had been developed as phytotechnology could to meet tofarmer’s benefit. There are two strategies for the Cd phytoextraction to be developed that theutilization of existing crop cultivar accumulating relatively high Cd or the newly seeking a plant
species hyper-accumulating Cd.
In this report, the actual development processes according to these strategies are introduced, thatthe cultivation method establishment of the Cd hyperaccumulator,.Arabidopsis helleri ssp.

gemmifera. The efficacy criterion of plant selection for the phytoextraction purpose is not only thetolerance to toxic heavy metals, but also the high biomass production to ensure the total removal of
metals. Basically, the hyperacumulators are the wild plants living in a natural habitat, thus thepractices of utilization must include a process for the domestication of the hyperaccumulators.
New line of A. h. gemmifera, named as ‘AHG347 winter clean, had been registered by Ministry ofAgriculture, Forestry and Fisheries Japan

Keywords: Contaminated agricultural land, Phytoextraction using accumulator
plant species, Domestication of wild plants, Arabidopsis halleri ssp.
gemmifera of hyperaccumulator−73−㻙㻌 㻝㻌 㻙㻌

Fujita Technical Research Report No.55§1. Introduction:
Soil contamination in agricultural land underhuman health risk caused by Cd intake through aJapanese regulation

food chain. Then, the designation requirements for
Under the Japanese act, the Act to Prevent Soil
Contaminationon

Agricultural

Land

Cd

would

be

unavoidabletoambiguously(1971,

determining due to a Cd content in rice varies

hereafter called as “Prevention Act”), the threedepending on the complicated factors (e.g. Cd

hazardous substances, cadmium (Cd), copper (Cu),content in soil, soil pH, chemical forms of Cd in soil,

and arsenic (As), are determined for an agricultural

redox condition of soil etc.). Whereas, the other two

land. The regulatory standards of which listed as

standards, for Cu and As, had been examined in

the Environmental Quality Standards for Soilterms of preventing the decrease of crop production

Pollution for each substance are the followings:

influenced by the elements in soil with the toxic
levels.

Cd: less than 0.4 mg kg-1 in rice for agricultural

It would be said that the difference of the criteria

landreflects many designation cases for Cd according to

Cu: less than 125 mg kg-1 for agricultural landthe(paddy field only)

Environment Japan. The wastewater and smoke

As: less than 15 mg kg-1 for agricultural landdischarged from the metal mine and/or smelter(paddy field only)

processes are the major Cd pollution causes on thesurveyresults

oftheMinistryoftheagricultural lands. In actual, the publicized handout
Under the Prevention Act, the designation

at fiscal year 2007 by the Ministry of therequirements for the agricultural land are defined

Environment shows 88.4% (5651.9 ha) of thefor each hazardous substance, as follows:

cumulativeareas

designatedrequiringthecountermeasures had been impacted by discharge
from the metal mine and/or smelter processes [1].

Cd: An area of which produce a rice exceeding thestandard value in cadmium content deter-mined byAmong these three hazardous substances, as

an acid digestion. Additionally, the nearby area is

specified by the Act, Cd is different from other two

also designated as the area to be suspected

elements that the Cd pollution in the agricultural

producing the substandard rice, the relevant

land was realized from beginning of issue as therequirements should be considered that combine Cd

hazard risk of an intake of staple food. In general,content in soil (0.1M HCl extractable) with soil

Cd may be the element of which tends to be

texture for this additional designation.

relatively easier accumulated in plant body from themedia regarding a ratio of Cd concentration in plant

Cu: An area that a copper content in soil (0.1M

to its concentration in soil [2].

HCl extractable) is equal to or more than the

The peoples who, like Japanese, eat rice as theirstandard value.
As: An area that a copper content in soil (1M HCl

staple diet that Cd-induced risk in rice should haveextractable) is equal to or more than the standard

been great concern for all persons on a food-chain

value.

including a farmer, distributor, and consumer. The
Japanese government, the Ministry of Agriculture,
Forestry and Fisheries (2016), had implemented theIt can be understood that for the Japanesestandard of Cd to be determined as a Cd content inmonitoring

rice, the standard should be considered in view of adomestically produced crops from fiscal year 2009 to

−74−
2

for

the

Cd

concentrationsinDevelopment of Plant for Practical Cd Phytoextraction on Agricultural Land2014. The purpose of this monitoring to verify thedevelopment of using plants technology for thiseffectiveness of means for reducing the Cd risk inpurpose, two strategies can be driven that removing

farm produce, that to be assessed by comparison

the specified substances from soils and causingwith previous survey results of Cd in crops. Thisdecreased

latest monitoring results publicized at February

for-instance appears that as the phytoextraction is2016, concluded that the health risks induced byassumed adaptable technique for the purpose, that

dietary intake of Cd have been decreased withthe hazardous substances are removed by plant

reducing the Cd concentrations in crops as low as nofunctions of which absorption from soil andpractical impact under ordinary eating habits [3].

accumulation in plant body. Then, the latter include

Whereas,forthefarmerworking

on

the

the

means

absorption

of

into

biologicalcrops.

andThe

formerphysicochemical

moderately contaminated agricultural land, themethodologies that choosing or breeding the low

possibility would remain that of crop production

absorption crop varieties, optimizing soil properties

withto restrict the absorption, i.e., soil pH, water

relatively

higherconcentrations

of

the

hazardous substances potentially or incidentally.
The

risk

management

for

the

condition.

moderately§3. Phytoextraction for agricultural land

contaminated agricultural land needs the widely
applicable countermeasures including continuous
implementation of the existing countermeasures, e.g.

As is emphasized by Ebbs et al. [4], the requisites

soil dressing, well controlled irrigation procedure,of phytoextraction procedure to be successful thatmaintaining adequate soil pH, and additional

should be the rapid identification of the effective

introduction of technique reducing the concentration

plant species and establishment the agronomicof the hazardous substances.

practices increasing metal uptake and accumulation

The agricultural lands are places basically to be

into plant body. This concept leads two policies todeveloped for plant production. Thus, using plants

develop the phytoextraction procedure (Figure 1),technology should be reasonably practicable for thethat the utilization of existing crop with the ability

rehabilitation of the mine-impacted agriculturalto accumulate metals and the finding a favorable

land.

wild plant species with the ability to produce highThisreportreviews

mainlythebiomass.

developed

Table 1 shows the Cd removal on field trials ofphytotechnologies reducing Cd risk to be most

phytoextraction researches in Japan. These results

significant issue on the agricultural land in Japan.

are selected from which the reports describe the§2. Strategy of reducing Cd risk; Phytoextraction

basic data set, Cd removal, soil Cd concentration,and shoot Cd concentration, directly in its tables orremoving Cd from soil

text. Basically, it is difficult to evaluate theThe basic concept is clear that for the recovery

performance of plant species comparing solely theprocedure for the Cd contaminated agricultural

Cd removals between the experiments underlands to be successful for all participants, a farmer’s

different conditions. Then a calculation of ratio of Cd

benefit

The

concentrations in shoot to its in soil should be

purposely designed methods to recover must be

helpful index to represent an effectiveness ofpracticable for farmer, i.e., restarting easier a crop

accumulation comparing the results in combination

production

with the Cd removals.

shouldorbeconsidered

reducing

risk

primarily.

tobepromoted

simultaneously with a crop production. Thus, the㻙㻌 㻟㻌 㻙㻌−75−

Fujita Technical Research Report No.55

Phase 1: Selection of plant to be applied for phytoextraction
Crops

Wild plants• Modification ofexisting cultivation method• Establishment of cultivation
method newly required
Inquest of adaptable conditions for cultivation
based on identified life cycle• Guaranteed supply ofseed/seedling• Seed/ Seedling production• Fertilization (level-response, timing)• Pest control•Weed control

Phase 2: Breeding of selected plant to be more practical for phytoextraction
Cultivar

Wild species• Accumulated information ofgenetic background• No or less information ofgenetic background

Systematized breeding plan

Breeding plan with uncertainties• Crossing inter-cultivar focused on
identified traits• Mutant: Selection and analysis ingene level• Crossing intra-specificfocused on visual traits
Additional item: Promoting germination• Inimitably determination of priming condition
to be required due to its low germination rate of seeds

Figure 1. Two strategies for development of plant for phytoextraction

Table 1. Cd removal on field trials of phytoextraction researchers in Japan
Plant species
Crop

Wild plant

Scientific name
Oriza sativa

Cd removal

Soil Cd
Shoot Cd
concentration concentration

Shoot to soil
ratio

References

Cultivar name
MORETSU
IR-8
Chokoukoku
Chokoukoku*
IR-8*
Chokoukoku
IR-8

g ha-1
516
657
377
204
70
153
63

mg kg-1 DW
2.91
2.52
0.67
0.66
0.69
0.64
0.76

mg kg-1 DW
40.0
49.7
33.7
28.6
6.7
13.5
7.0

13.7
19.7
50.3
43.3
9.7
21.1
9.2

[5]
[5]
[6]
[7]
[7]
[7]
[7]

Hibiscus moscheutos

-

347

2.1

9.6

4.6

[8]

Crassocephalum
crepidioides

-

184

2.9

28.6

9.9

[9]

Solidago altissima

-

2820
3687

30.1
4.9

14.5
18.0

0.5
3.7

[10]
[10]

Arabidopsis halleri
ssp. gemmifera

-

1408
259
1560
3000

3.1
1.2
3.6
3.5

354
91
421
908

114.2
75.8
118.6
263.2

[11]
[11]
unpublishedunpublished* upland condition
For a multi-year experiments, the maximum Cd removal is trascribed. The soil Cd concentrations are 0.1M HCl extractable.

㻙㻌 㻠㻌 㻙㻌−76−

Development of Plant for Practical Cd Phytoextraction on Agricultural LandIn the studies using crop, the experiments

maximizing the biomass production. Meanwhile, if

conducted with rice plant have a predominantly

it has been achieved, the results of field trials

high number of study case, inevitably have beenutilizing

carriedhyperaccumulators can became strong candidates

out

an

inter

cultivarevaluation

of

A.

h.

gemmifera

mean

that

the

for the practical phytoextraction.

performances. Japanese researchers who oriented in
the rice plant utilization for Cd phytoextraction
illustrate the advantages to meet appreciably the§4. Development of wild plants for practical Cd

requirements of which Ibaraki and Taniguchi

phytoextraction[12]

pointed, as followings:· Stability of transplanting cultivation

4.1 Established cultivation method for Arabidopsis· The consistent cultivation method had beenhalleri ssp. gemmifera
As described above, the utilizing wild plants species

established with increased mechanization.
· Most of the farmers are proficient in riceneeds a huge effort to establish the cultivation method tocultivation i.e. without hesitation to cultivate.

domesticate wild plants for phytoextraction procedure.

In actual, as shown in Table 1 rice cultivar like

Then, the behavior of that species growing in the natural‘Chokoukoku’ with high Cd accumulation ability

habitat should be observed and used as a reference tomust be fit to practical phytoextraction for thebuild a cultivation schedule.

Arabidopsis halleri ssp. gemmifera, a member of the

agricultural lands.
On the other hand, using wild plant trials, theBrassicaceae, is perennial, wintering ability herbal plantamount of Cd removal achieved by Solidago

living in Russian Far East, north-eastern China, Korea,

altissima cultivation is extremely high. However,and Japan.

the Cd concentrations in shoot and its ratios shoot to

A. h. gemmifera spends the winter season in the form

root represent clearly that the large amount of Cd

of rosette, then moves into bolting and flowering phase atremoval is brought by remarkably high biomass

the next spring season. Thus, the basic cropping patternproduction that makes post-harvest process difficult

was built up to be started from midsummer or early

to collect and treat plenty of plant residue.

autumn then harvested by the end of flowering season,

Arabidopsis halleri ssp. gemmifera performed

typically by the middle of May.

high amount of Cd removal as shown in Table 1,

Transplanting of seedling was selected as the start ofwould be considered plant species to be ideal for

cultivation for A. h. gemmifera due to its low germination

phytoextraction

thathyperaccumulator

of

is

known

as

a

rate being inherent in wild plants. The usual germination

and

Zn

[13],

[14].

rate of its seed is of around 30% by two weeks on wetted

Hyperaccumulator plants have peculiarly highfilter paper and is not practically high to start theability to absorb and storage toxic heavy metal in its

cultivation with direct seed sowing on a field. The

body. The amount of the hazardous substrate

systematic way was employed that produce plug-shaped

removal of phytoextraction is expressed as theseedlings grown on the standardized plastic tray for

multiplication of a plant biomass by the hazardous

approx. 45 days growing.

Cd

[11],

substrate concentration of plant body. Thus, theThe response to fertilization of A. h. gemmifera

primal benefit is that for phytoextraction whichindicates that the favorable nitrogen application level isused hyperaccumulator performed likewise for A. h.

15 to 20 gN per m2 within the cropping period using

gemmifera, lesser plant residual can bring out

ordinal chemical fertilizer, then the density of cropping isbiggerstandardized on 16 to 20 plants per m2.

hazardous

risk

from

the

agricultural

An insecticide treatment for seedlings just before

production.

transplanting would be effective not only avoiding an

The development for wild plants requires a huge
efforttoestablishthecultivation

insect damage but also labor-saving. For the weed control

method㻙㻌 㻡㻌 㻙㻌−77−

Fujita Technical Research Report No.55

using the selective herbicide to Poaceae, is predictably

combinations of selected three lines

effective that combines a soil-applied herbicide priorcropping with a foliage treatment herbicide for early

Figure 2 and 3 show the process and result of selection

spring.

and crossing for A. h. gemmifera to be uniformed,
respectively. New line of A. h. gemmifera, named as

4.2 Selection and crossing for A. h. gemmifera to be‘AHG347 winter clean, had been registered by Ministry of

uniformed

Agriculture, Forestry and Fisheries Japan.

Non-uniformity among the individuals must be great
concern of wild plants to be utilized commercial basis. The

4.3 Treatment for promoting germination

policy for A. h. gemmifera to be uniformed was built upon
the selection focused on visually apparent traits and then

For the purpose of more labor-saving, A. h. gemmifera

observation of reproducibility after crossing due to no

cultivation starting directly sowing of seed should be meetinformation of genetic background. The processes of

to former’s desirability. However, inherent germination

selection and crossing were as follows;

rate must be too low for this purpose. Then, the conditions· Selection of relatively bigger individuals fromof priming treatment had to have been investigated forcommunity of over a thousand of individuals cultivated on

seeds of bred A. h. gemmifera line. It has been found thatthe same field conditions

the priming treatment in an original way should be· Secondary selection for a hundred individuals toeffective but the protocol for priming must be modified

identity the line with bigger size and surviving throughappropriately for each lot of seed production (Figure 4).

summer season

The germination ability of primed seeds is certified as· Selected ten lines were tested to certify thepractical for the field trials, in fact the emergence of A. h.

reproducibility of visual property focused on

gemmifera could be observed at two weeks after sowing·Crossing and observation of uniformity for theon the actual field as shown in Figure 5.

Crossing

100 individuals

Selected 10 lines

Seed production

Vegetative propagation of
3 lines with fineness properties

Figure 2. Breeding process of A. h. gemmifera to be uniformed㻙㻌 㻢㻌 㻙㻌−78−

Development of Plant for Practical Cd Phytoextraction on Agricultural Land

Figure 3. Improved uniformity of A. h. gemmifera , AHG347 winter clean (right), compared with inbred lines (left)
substances. The phytoextraction, one of the such

Germination rate (%)

70

non-Treat.

trials, based on plant-technologies could provide an

Primed A

60

agricultural solution for the industrial generation

Primed B

source of pollution.

50

developed

40

areThen, the countermeasuresresource

should

to

be

taken

depending on its features. If the phytoextraction is30

applied for the contaminated agricultural lands in20

accord with the crop production, it brings the10

sustainable and safe crop production.

0

0

2

4

6

8

10

12

14

References

Days fromsowingFigure 4. Effectivenessof priming
treatment[1] Ministry of the Environment: Committee handouts,
Expert Committee for Soil Environmental Standards ofAgricultural Land. Central Environment Council,
Ministry of the Environment, Government of Japan,
http://www.env.go.jp/council/10dojo/yoshi10-06.html,
2016 (in Japanese)[2] Kabata-Pendias A, Pendias H: Chapter 5, Traceelememts in plants. In Kabata-Pendias A editor: Traceelements in soils and plants Third edition, Boca Raton,
2000, CRC Press, pp 73–98.
[3] Ministry of Agriculture, Forestry and Fisheries: Press
Release, Ministry of Agriculture, Forestry and Fisheries,
Government of Japan,

Figure 5. Emergence of primed seed on the actual

http://www.maff.go.jp/j/press/syouan/nouan/160223.html,

contaminated field, 2 weeks after sowing

2016. (in Japanese)[4] Ebbs SD, Lasat MM, Brady DJ, Cornish J, Gordon R,§5. Overview

Kochian LV: Phytoextraction of cadmium and zinc fromThe status of pollution in the agricultural lands

a contaminated soil, Journal of Environmental Quality

had

26(5): 1424-1430, 1997.

been

monitoring

andcontrolling

underJapanese regulation. Whereas, the possibility would[5] Ibaraki T, Kuroyanagi N, Murakami M: Practicalremain that of crop production with relatively

phytoextraction in cadmium-polluted paddy fields using

higher concentrations of the hazardous substances.

a high cadmium accumulating rice plant cultured by

The efforts of the people involved in this issue

early drainage of irrigation water Soil Science and Plant

maintainlowering

the

risks

of

Nutrition 55(3): 421-427, 2009

hazardous㻙㻌 㻣㻌 㻙㻌−79−

Fujita Technical Research Report No.55[6] NARO (National Agriculture and Food Research[12] Ibaraki T, Taniguchi A: Leading edge technologies

Organization): Utilization of cadmium high absorption

for remedying heavy metal-contaminated agricultural

rice variety ‘Chokoukoku’ for soil remediation technology

soils

Information of research progress,-contaminated agricultural soils-Aiming toward the

http://www.naro.affrc.go.jp/org/tarc/seika/jyouhou/H19/su

practicable phytoremediation. Japanese Journal of Soil

itou/H19suitou020.html, 2007. (in Japanese).

Science and Plant Nutrition 78(6): 627-632, 2007. (in[7] Honma T: The study on phytoremediation by

Japanese)

High-Cd-Accumulating rice in low-level cadmium[13] Kubota H, Takenaka C: Arabis gemmifera is acontaminated paddy field and control of cadmium

hyperaccumulator of Cd and Zn. International Journal ofabsorption of rice Journal of the Niigata Agricultural

Phytoremediation 5: 197-201, 2003.

Re-search Institute 12: 1-100, 2014. (in Japanese with

[14] Kubota H, Sugawara R, Kitajima N, Yajima S, Tani

English summary)

S: Cadmium phytoremediation by Arabidopsis halleri

4.

Phytoremediation

for theheavy metalT:ssp. gemmifera Japanese Journal of Soil Science andPhytoremediation with kenaf (Hibiscus cannabinus) for

Plant Nutrition 81(2): 118-124, 2010. (in Japa-nese withcadmi-um-contaminated paddy field in southwest area ofEnglish abstract)[9]

Kurihara

H,

WatanabeM,

Hayakawa

Japan. Japanese Journal of Soil Science and Plant
Nutrition 76(1): 27-34, 2005. (in Japanese with English
abstract)[10] Tatekawa H: Using plants decontamination method
for soil cadmium Journal of JSIDRE 43: 674-677, 1974.
(in Japanese)[11] Kameyama K, Tani S, Sugawara R, Kitajima N,
Ishikawa Y: Remediation of Cd-contaminated andisol by

Nobuyuki
Kitajima

Arabidopsis halleri ssp. gemmifera IRDE Journal 276:
55-62, 2011. (in Japanese with English abstract)㻙㻌 㻤㻌 㻙㻌−80−

Short comment
The developed plant for practical
phytoextraction on the agricultural land,
had been registered as a variety of“AHG347 winter clean”. It means
symbolic milestone of the domestication ofwild plant to be completed, and also of the
product commercialization.