22G12
Effect of atmospheric pressure torch plasma irradiation on plant growth
大気圧トーチプラズマ照射による植物成長への効果
Yusuke Akiyoshi*, Akari Nakahigashi*, Nobuya Hayashi*, Satoshi Kitazaki**, Kazunori Koga**,
Masaharu Shiratani**
秋吉雄介*，中東朱里*，林 信哉*，北崎 訓**，古閑一憲**，白谷正治***Faculty of Science and Engineering, Saga University
1 Honjo-machi, Saga-shi, Saga 840-8502, Japan**Department of Electrical and Electronic Engineering, Faculty of Information
Science and Electrical Engineering, Kyushu University744 Motooka, Nishi-ku, Fukuoka-shi, Fukuoka 819-0395, Japan*佐賀大学理工学部 〒840-8502 佐賀県佐賀市本庄町１番地**九州大学システム情報科学府 〒819-0395 福岡県福岡市西区元岡744
Growth stimulation characteristics of plants seeds are investigated by an atmospheric discharge plasma.
Atmospheric pressure plasma torch is consisted of alumina ceramics tube and the steel mesh electrodes
wound inside and outside of the tube. The growth stimulation was observed in the length of a stem and aroot after the plasma irradiation. The stem length increases approximately 2.8 times at the cultivation timeof 24 h. And the growth stimulation effect is found to be maintained for 40 h, after sowing seeds. The
mechanism of the growth stimulation would be the redox reaction inside plant cells induced by oxygenradicals.

1. Introduction
Recently, the growth stimulation of living
bodies such as cells, microorganisms, and plants
has been studied utilizing electrical pulses [1] anddischarge plasmas [2-5]. When seeds of plants
such as radish sprout are irradiated with discharge
plasma, the growth speed of the sprout isobserved to be accelerated throughout its lifetime.
Stress responses that have been maintained forlong periods, i.e., on the order of a lifetime, arerelated to the genome. The above stresses would
modify the structures of the genome such as DNA,RNA, and transcription factors. Transcription
factors are types of protein that transcribe
genome information from DNA to RNA; they are
activated by external stresses like heat andimpact.
One of the promising candidates of the growth
acceleration mechanism is associated with heatshock factors (HSFs). HSFs generate heat shockproteins when a living body receives externalstresses, and accelerate cell growth for survival
against the stresses. The control of plant growthby external stresses is possible by themodification of the structures of HSFs. Theswitch of HSFs would be the cystein-cystine
redox reaction of Thiol compounds such asthioredoxin and Gultathione in HSFs forming
disulfide bonds. Therefore, thiol compounds aremajor substances that cope with external stresses
to living bodies. In this study, radicals were used
to characterize and control the redox treatment ofthiol compounds. Also, the quantity of total thiol,
which mainly comprises thioredoxin andGultathione in plants, is measured in order toconfirm redox reactions using radicals in oxygen
plasma. The correlation between the thiol
quantity and the stimulation of plant growth
clarifies the mechanism of the growth stimulation
phenomenon induced by plasma irradiation.
Gas
Alumina tube
Tungsten wire～

Radish sprouts
seeds

Atmosphericpressure plasma

Fig.1: Atmospheric pressure torch plasma
apparatus

3. Results And Discussion
3.1 Enhancement of Plant Growth Speed by Plasma
Irradiation
The growth stimulation was observed in thelength of a stem and a root after the plasma
irradiation. Fig.2 relation between cultivation
period and sprout length The stem length increases
approximately 2.8 times at the cultivation time of
24 h. And the growth stimulation effect is found to
be maintained for 40 h, after sowing seeds.
Therefore, the mechanism of the growth stimulation
would be the redox reaction inside plant cells
induced by oxygen radicals.
3.2 Redox Reaction of Thiol Compound and Growth
Enhancement Mechanism
Fig.3 illustrates the relation between the thiol
quantity of plant seeds and the oxygen plasma
irradiation period. The oxygen plasma irradiationdecreases the thiol quantity with the treatment period.
This result indicates that the reduction type thiol isoxidized by oxygen radical. Increase of the reduction
type thiol in cells tends to activate transcription
factors and related growth-promoting factor
activated by reduction type thiol are one ofcandidates of plants growth mechanism.
4. Conclusion
The growth stimulations in plant length arestudied using radicals produced in atmosphericplasmas. The thiol quantity of radish sprouts, whichis related to the redox reaction between cystein,cystine and the growth factors, would be modified
by plasma irradiation. Therefore, reactive plasma
would be served as a good tool for the control ofredox reactions in plants and plant growth.

Average sprout lenght (cm)8Controlatmospheric air pressure 30min

765432
10020
40
60
80
Cultivation period (h)100Fig.2: Relation between cultivation period andsprout length
0.8
0.7
Thiol amount (arb.units)

2. Experimental Procedure
Fig.1 shows the schematic diagram of theatmospheric pressure plasma torch apparatus.
Atmospheric pressure plasma torch is consisted ofalumina ceramics tube and the steel mesh electrodes
wound inside and outside of the tube, with thedimension of 130 mm in length and 3 mm in adiameter. When AC high voltage (8 kHz) is applied
to the electrode gap, the barrier discharge plasma is
produced inside the alumina ceramics tube. Thebarrier discharge plasma is blown outside with thegas flow in ceramics tube. The gas served in thisexperiment is pure oxygen and nitrogen.
Radish sprouts seeds locate at 1 cm from thetorch edge. After the irradiation of the plasma for
10 min or 20 min or 30 min or 60 min, the seeds aresown to the cultivation pot after the plasma
irradiation. The length of the radish sprouts isrecorded every 24 hours.

0.6
0.5
0.4
0.3
0.2
0.1
0.0051015202530

Treatment period (min)Fig.3 Relation between thiol quantity of plantseeds and O2 plasma irradiation period.

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