Abstract
[Purpose]
Frequency of micronuclei observed in germinating onion seed root tip cells 18 hours after irradiation increased with increase of absorbed dose in the low absorbed dose region and decreased with further amount of the dose. We firstly supposed that the disappearance was caused by cell death. However growth of the root was not stopped with as high as 160 Gy of γ-ray. No remarkable effects were observed about the growth of the seedlings with the high dose.
Therefore, we turned the idea that the main cause of the disappearance was not cell death but temporal division delay after the irradiation. To verify the idea, we studied relationship between delay of cell division and micronuclei occurrence frequency in germinating onion seed root tip cells irradiated with gamma ray.
[Method]
Cs-137 γ-ray was irradiated to germinating onion seed at the irradiator at Division of Radiation Biology and Protection, Center for Frontier Life Sciences, Nagasaki University.
Time dependence of micronucleus frequency after irradiation was observed.
[Results]
As increase of absorbed dose, peak of micronuclei incidence became late.
Occurrence frequency of micronuclei increased with increasing absorbed dose until 4 Gy and decreased with further amount of the dose.
As increase of absorbed dose, mitotic index peak of cell became late too.
