Root growth of onion seedlings irradiated by accelerated heavy ions.

Abstract

Micronuclei of the onion root tip cells irradiated by accelerated heavy ions showed upward convex bell shaped dose-effect relationships. The shape can be accounted for by a simple mathematical model. The analysis with the model implies that the micronuclei and the damages to induce interphase death or division delay were both formed averagely proportionally to the square of LET. To evaluate the interphase death, we investigated shortening of the root growing. We expected the shortening to be proportional to the interphase death. But the root length L(D) with absorbed dose D follows the expression L(D)= L(∞)−Aexp(-αD), and the growth did not stop even with extremely high absorbed dose. LET dependence of α existed, but it was slower than the micronuclei induction.