COLCHICINE-INDUCED SOMATIC CHROMOSOME REDUCTION IN SORGHUM V. DIPLOIDIZATION OF THE STEM APEX AFTER TREATMENT OF TETRAPLOID SEEDLINGS

Publisher Website
Google Scholar
Abstract
In order to study the manner in which diploidization of tetraploid stem apices in tetraploid seedlings of sorghum occurs after colchicine treatment, paraffin sections of stem apices at periods from 0 to 14 days after colchicine application were studied. It was found that diploid cells occur as early as 48 hr. after application and that they may comprised all or almost all of the apical dome by the 5th to 9th day. The tetraploid cells within the apical dome may be replaced by more competitive diploid cells formed, either within the corpus followed by replacement of cells in the tunica layer, or within the tunica layer followed by periclinal division to replace cells in the corpus. The location of the original aiploid cell may determine at what rate diploidization occurs. Evidence that the original diploid cell may have been cut off from a multinucleate cell was observed. The chromosome number may have been reduced from the tetraploid through nondisjunction or possibly by a mechanism giving an immediate precise separation of a balanced genome.