Studies on sprout inhibition of onions by gamma irradiation—I. influence of time interval between harvest and irradiation, radiation dose and environmental conditions on sprouting

Sprout inhibition of onions by gamma irradiation was found to be influenced by the physiological state of the bulbs at the time of irradiation, radiation dose and the storage temperature after irradiation. Sprouting was minimal during storage at ambient temperature (26 to 32°C) while exposure to low temperature (4 to 20°C) or widely fluctuating diurnal temperature (20°C min to 30°C max) accelerated it. Six to nine Krad inhibited sprouting during storage under the above conditions only if the bulbs were irradiated within a fortnight of harvest when they were in the dormant state. Twenty-five Krad caused a transient stimulation of sprouting regardless of the time of irradiation while 6 to 12 Krad only stimulated sprouting when the time interval between harvest and irradiation exceeded three weeks. Irradiation at all dose levels caused discoloration of the growth centre, the extent of which was minimal in bulbs exposed to low doses soon after harvest and in those stored at ambient temperature.