Physiological and biochemical changes in γ-irradiated rice

Metabolic disturbances resulting in growth retardation and death of rice irradiated with ⁶⁰Co γ-rays at 10 to 40 kR dose levels were investigated. Seedling growth, release of storage products (reducing sugar and free amino acids) and incorporation of radioisotopic substances ([³H]-uridine, [³h]-thymidine and [³h]-leucine) remained almost uninhibited at doses up to 20 kR but were much reduced at 40 kR. Following the 40 kR treatment, shoot elongation was terminated at the 5th day of germination, corresponding to an interruption in the release of reducing sugar. Furthermore, the onset of active increase in [³h]-thymidine incorporation after germination was also delayed in the 40 kR irradiated samples.

When the seeds had been cultured in glucose-medium immediately after irradiation there were significant regular increases of survival and a disappearance in the delay in [³h]-thymidine incorporation. However, glucose had no marked effect on subsequent growth and overall metabolic damage even though incorporation of [¹⁴C]-glucose was slightly higher in the irradiated than in the control in the early stage of germination.

It is suggested that the recovery from radiation damage in the early stages of germination can be enhanced by the provision of glucose while recovery from damage leading to reduction of subsequent growth is less sensitive to glucose.