Effects of acute gamma irradiation and developmental stages on growth and yield of rice plants

Rice plants were exposed to 1, 2·5, 5, 7·5 and 10 kR of acute gamma rays at 4 critical developmental stages, i.e. pre-tillering, earprimordia formation, meiosis and heading.

Doses of 1 and 2·5 kR, in general, had a stimulatory effect on culm length, tillering, ear number per plant, spikelet number per ear and seed yield per plant, at the first two developmental stages, particularly at the pre-tillering stage. There was a significant reduction in all the above characters at 5 and 7·5 kR for all irradiated stages. Of the different developmental stages, pre-tillering was most radiosensitive (LD₁₀₀-7·5kR), followed by meiotic and heading stage.

Stage of development, exposure rate and differences in interphase chromosome volume (ICV) are discussed as possible factors affecting radiosensitivity.