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.