| Abstract: | 1. Primary roots of Vicia faba were irradiate after one day'sgermination. The X-ray dose was 620 r 2. Cells with changed chromosome complements appeared in lateralroots. It is inferred that these cells are descended from cellsdamaged by irradiation; chromosome breakage was seen in thefirst mitoses in the irradiated roots but was not scored. 3. Six types of chromosomal rearrangements were found. One typehad been reported previously in primary roots of V. faba afterX-raying. 4. The new complements appear to be stable because they occurseveral cells of a lateral. Affected laterals could containup to five new complements. The primordium of such a lateralmust have consisted of five changed and at least one normalcell. It had previously been suggested that a root of Viciahad three or four initial cells. 5. The survival of the cells with changed complements is notdue solely to successful competition with, not to support by,normal cells, otherwise other types of changes should also havebeen found. 6. It is suggest that the changes found were perpetuated becausethey were induced in initial cells of the primary root, andthat cells in which they were present beca,e part of the primordialand continued as initial cells in apical meristems of lateralroots. 7. Apical cells appear to have a lower sensitivity than othermeristematic cells, so providing, after treatment, a reservoirof normal cells from which regeneration can occur. |
