We have investigated plant growth response to atmospheric air plasma treatments of seeds on their growth for 5 plant speces; Radish sprout (Raphanus sativus L.), rice (Oryza Sativa), Zinnia, Arabidopsis L. Thaliana and Plumeri. The average length of Radish sprout, rice, Arabidopsis Thaliana, Plumeria and Zinnia, are 250%, 80%, 60%, 30% and 20% longer than those without plasma treatments, respectively. We have obtained correlation between the growth enhancement and O3 and NOx concentration. The optimum radical dose for the growth enhancement depends on plant species.

We studied effects of atmospheric air dielectric barrier discharge plasma irradiation to seeds of radish sprouts on chlorophyll and carotenoid concentrations in their leaves. Plasma irradiation increases chlorophyll concentration under some irradiation conditions, whereas the irradiation has little effects on carotenoid concentration. These results show that plasma irradiation to seeds has influence on cell activities in a selective way.

We have studied multigeneration effects of plasma irradiation to seeds of Arabidopsis thaliana (L.) and Zinnia peruviana (L.) on their growth using a scalable DBD device. Atmospheric plasma irradiation enhances growth of these plants in multi-generations. For Arabidopsis thaliana (L.) in the third generation, the leaf area is 2 times larger than that without plasma irradiation and the stem length is 1.5 times longer than that without plasma. For Zinnia peruviana (L.) in the second generation, the stem length is 2 times longer than that without plasma.

We investigated effects of atmospheric pressure dielectric barrier discharge (DBD) plasma irradiation on growth characteristics of bread yeast (Saccharomyces cerevisie). Nitric oxide of 400 ppm and O3 above 200 ppm are produce by the DBD plasmas. DBD plasma irradiation of 50 and 100 s enhances the growth of yeast in the lag phase, whereas 150 s irradiation suppresses the growth. There is an optimum duration of plasma irradiation for the growth promotion.

Growth enhancement characteristics of plants are investigated using 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 enhancement was observed in the length of stem and root of plants after the plasma irradiation to seeds. The stem length increases approximately 2.8 times after the cultivation time of 24 h. And the effect is found to be maintained for 40 h, after sowing seeds. The mechanism of the growth enhancement would be the redox reaction inside plant cells induced by oxygen radicals.

We compared growth enhancement of radish induced by O2, air, and Ar plasma irradiation. The average length of radish sprouts cultivated for 4 days after O2 plasma irradiation is 70% longer than that of sprouts without irradiation. The O2 plasma irradiation is more effective in enhancing growth than air and Ar radio frequency plasma irradiation. Cell morphology and cell size of sprouts with O2 plasma irradiation is nearly the same as those without irradiation. These results suggest that plasma induced acceleration of cell proliferation brings about the rapid growth.