The X-Ray Sensitivity of Brassica Rapa L. Seeds

Summary

Brassica rapa seeds were subjected to doses of X-rays from 10,000 to 100,000 r. The higher doses caused a small but significant decrease in seed germination. The survival of plants, 108 days after sowing, from seeds which had received the highest dose was approximately 15% of the survival of the control plants.

The LD 50 for B. rapa seeds was about 75,000 r, and the critical dose for mutation breeding purposes was about 80,000 r.

The curve relating plant survival to dose of X-rays was sigmoidal and characteristic of about 8 or 9 hits. While this might indicate a critical number of meristematic cells which have to be killed to cause embryo death, it was considered that the dose/survival relationship was complicated by lethal physiological effects of the X-irradiation.