Satoshi Kitazaki

Growth Enhancement of Radish Sprouts Induced by Low Pressure O2 Radio Frequency Discharge Plasma Irradiation

We studied growth enhancement of radish sprouts (Raphanus sativus L.) induced by low pressure O2 radio frequency (RF) discharge plasma irradiation. The average length of radish sprouts cultivated for 7 days after O2 plasma irradiation is 30–60% greater than that without irradiation. O2 plasma irradiation does not affect seed germination. The experimental results reveal that oxygen related radicals strongly enhance growth, whereas ions and photons do not.

Redox Characteristics of Thiol Compounds Using Radicals Produced by Water Vapor Radio Frequency Discharge

The redox reaction between cystein and cystine is observed using radicals produced in water vapor plasma for the control of plant growth. Cystein is oxidized to cystine using the OH radical in the higher-pressure regime and cystine is reduced to cystein by the H radical generated in the lower-pressure regime. Also, the oxidative stress reaction of plants is observed when water vapor plasma is irradiated onto seeds of plants such as radish sprouts. The mechanism of the control of plant growth is explained by the change in thiol compound quantity of the plant cells induced by the radical reaction.

Growth enhancement effects of radish sprouts: atmospheric pressure plasma irradiation vs. heat shock

We compare growth enhancement effects due to atmospheric air dielectric barrier discharge plasma irradiation and heat shock to seeds of radish sprouts (Raphanus sativus L.). Interactions between radicals and seeds in a short duration of 3 min. lead to the growth enhancement of radish sprouts in a long term of 7 days and the maximum average length is 3.7 times as long as that of control. The growth enhancement effects become gradually weak with time, and hence the ratio of the average length for plasma irradiation to that for control decreases from 3.7 for the first day to 1.3 for 7 day. The average length for heat shock of 60°C for 10 min. and 100°C for 3 min. is longer than that for control, and the maximum average length is 1.3 times as long as that of control. Heat shock has little contribution to the growth enhancement due to plasma irradiation, because the maximum temperature due to plasma irradiation is less than 60°C.

Growth control of dry yeast using scalable atmospheric-pressure dielectric barrier discharge plasma irradiation

We have investigated the effects of plasma irradiation on the growth of dry yeast (Saccharomyces cerevisiae) using a scalable atmospheric-pressure dielectric barrier discharge (DBD) device. NO of 380 ppm, NO2 of 10 ppm and O3 of 560 ppm were detected 1 mm below the discharges, which were produced by the DBD plasmas. DBD plasma irradiation of 10 to 100 s enhances the growth of yeast in the lag phase, whereas that of 120 and 150 s suppresses the growth. O3, NO2, photons, and heat generated by the plasma irradiation are not responsible for the growth enhancement of the dry yeast. Plasma etching has little effect on the growth of dry yeast cells. NO plays a key role in the growth enhancement of dry yeast cells.

Effects of Atmospheric Air Plasma Irradiation on pH of Water

We have studied the effects of atmospheric air plasma irradiation to water using a scalable dielectric barrier discharge device. Measurements of the pH of water treated by the plasmas have shown the pH decreases due to peroxide molecules generated by plasma irradiation and depends on material of water container. We also found this plasma treated water has little effect on the growth enhancement on Radish sprouts compare with plasma irradiation on dry seeds and the plasma irradiation can affect them through the water buffer of 0.2 mm in thickness.

Growth stimulation of radish sprouts using discharge plasmas

We have investigated growth stimulation of radish sprouts using nonthermal atmospheric pressure He discharge plasmas and low pressure O2 RF discharge plasmas. Seeds of radish sprouts were irradiated by one of these plasmas. After 7 days cultivation, the average length of sprouts with irradiation was 15–60 % longer than those without irradiation. Reactive oxygen species may be involved in the growth stimulation mechanism.

Redox characteristics of amino acids using low pressure water vapor RF plasma

The redox reaction between cystein and cystine is studied using water vapor plasma produced by the RF discharge concerning the growth control of plants. The stress reaction of plants has been achieved, when the water vapor plasma is irradiated to the seeds or stem, leaf of plants such as radish sprout. The mechanism of the growth control is investigated by analyzing amino acids of cystein and cystine. The water vapor plasma can oxidize and reduce the cystein and cystine, respectively by choosing the plasma parameters. The redox reaction of cystein and cystine in thioredoxin would be the mechanism of the plant control.