Effects of fission neutron, beta and gamma radiation on seedling growth of dormant and germinating seeds of barley

Abstract

Experiments were designed to study the effects of fission neutron (N f ), 60 Co γ- and 90 Y β-radiation on dormant and germinating seeds (caryopses) of barley, Hordeum vulgare L. cv. Himalaya. All seeds were adjusted to a water content of ~ 14 per cent and the irradiations carried out in air. For studies with dormant seeds, the seeds were soaked after irradiation in nitrogen-bubbled water at 0 °C for ~ 18 hr and then planted in blotter “sandwiches”. For studies with germinating seeds, the seeds were soaked ~ 16 hr at 0 °C and then planted either in blotter “sandwiches” or with the embryo oriented up on blotters in Petri dishes and allowed to germinate for 24 hr before irradiation. The mean doses for the β-radiation were calculated for that absorbed in the embryo by the first leaf, the endpoint measured. The results showed that γ- and β-radiation were equally effective in reducing seedling growth of both dormant and germinating seeds. Fission neutron radiation was ~ 40 times more effective than either β- or γ-radiation on dormant seeds at the D 50 level of damage but only 6·8 times more effective on germinating seeds. The RBE's for γ/N f and β/N f decreased with increased dose and level of damage for germinating seeds but remained nearly constant for the dormant seeds. The germinating seeds were 5·0, 29·3 and 30·0 times more sensitive to N f− , β- and γ-radiation, respectively, than the dormant seeds at the D 50 level of damage. These values also decreased with increasing dose and level of damage.