RESPONSE OF PRIMORDIAL CELLS OF VICIA FABA TO COLCHICINE

Whole root systems of Vicia faba were treated with 0.025 per cent colchicine for 3 h. Meristems of roots and developing primordia were examined immediately after treatment and 24 and 48 h later. Large primordia, i.e. those primordia that would emerge as lateral roots within approximately 24 h, are induced to form tetraploid cells. However, unlike lateral roots, they do not form a typical c-tumour, their longitudinal growth is not inhibited, and their mitotic index does not fall. Furthermore, the tetraploid cells induced in large primordia are not maintained when the primordia emerge as lateral roots. Since the response of the very largest primordia to a 3-h treatment with 0.025 per cent colchicine is similar in every way to that of lateral roots, it appears that the cells of primordia acquire the characteristics of lateral root meristematic cells before the primordia emerge. From the evidence that induced tetraploid cells fail to survive as a primordium grows out to form a lateral, it also seems that a structural reorganization accompanies the physiological reorganization that occurs as a primordium emerges. © 1969 OXFORD UNIVERSITY PRESS.