Somatic crossing over in Glycine max L. (Merrill): sensitivity to and saturation of the system at low levels of tritium emitted beta-radiation.

Seeds of varieties L65-1237 and T219 of soybean were soaked in 20-50 ml of tritiated water (HTO) containing between 0.01 and 50 μCi/ml of tritium (T) for various periods from 24 to 142hr. Genetic damage was determined by counting the number of Y11Y11-y11y11 spots on the Y11y11 leaves. No effect was noticeable in treatments lasting up to 24hr independent of the concentration. However, somatic crossing over occurred when the seeds were treated with tritium for 92 hr or longer even with concentrations as low as 0.01 μCi/ml. The data indicate that the soybean system being used is sensitive to very low doses of beta radiation. The damage to the seeds treated with the lowest concentration was not significantly different in quality or quantity from that induced by higher concentrations. This indicates some type of saturation effect to tritium-emitted beta radiation. Analytical results showed that synthesis of organic matter and incorporation of tritium into the organic fraction was delayed until about 96 hr after the imbibition was started. This indicates a relationship between spot induction by tritium and organic synthesis.