Mutagenesis-induced Ultrastructural Changes in Suspension-cultured Rice Cells

The two-year old suspensions derived from the calli of japonica rice (CV. 02428) were normal in cell ultrastructures with well developed organs. However, the number of mitochondrion per cell decreased and starch grains in plastids and vacuoles in cytoplasm appeared 3 days after irradiation with 500R γ-rays. Cell structure changed dramatically with all cell organs disintegrated 6 to 12 days after the radiation indicating that the damage of cell ultrastructure caused by the irradiation is irreversible. Treatement with 5000R γ-rays brought about even greater damage to the suspensions, accelerating the disintegration of cell organs. The suspension cells treated with 1 mmol/L and 5 mmol/L of SA caused loss of growth ability. The suspension cells of 02428 showed a higher sensitivity to both physical and chemical mutagens as compared to the young panicle of the rice.