The effect of 60Co irradiation on dry seeds of Zoysia japonica

The dry seeds of Zoysia japonica were irradiated by 60Coray at dosage of 25～500 Gy. The germination of seeds and growth of seedlings were investigated both in laboratory and field. The results indicated that irradiation of low dosage could promote seed germination and increase germination rate.But the germination rate decreased with the increasing of irradiation dosage, the critical dosage (dosage rate was 1.0 Gy/min) is 450 Gy; the critical dosage for field germination rate was 250 Gy, when the dosage below the critical was applied, the field germination rate increased with the increasing of the irradiation dosage, and decreased when the dose was over the critical; significant difference(P＜0.05) observed in taproot and seedling growth when the dry seeds were irradiated at different dosage; the length of taproot, height and fresh weight of seedling were all promoted firstly and declined later, their critical dosage was 400 Gy, 300 Gy and 250 Gy, respectively. The half lethal dosage of Z. japonica dry seeds was 480 Gy based on correlated broken line graph between irradiation dosage and relative germination rate.