Some Observations on the Growth of Lateral Roots of Vicia Faba L. And Their Response to Colchicine Treatment

Abstract

SUMMARYThe effect of colchicine treatment on the number of cells in prophase was investigated in the apical meristems of 2-mm-, i-cm-and 4-cm-long lateral roots of Viciafaba. Colchicine was most effective in causing an initial drop in prophase numbers in the 2-mm-long roots, while it had a less drastic effect on the i-cm laterals and no significant effect at all on the 4-cm ones. Also, while a significant increase in the number of cells in prophase was found 24 h following the start of treatment in the i-cm-long roots, no significant increase took place in the 2-mm or 4-cm laterals. Thus, elongating lateral roots at different developmental stages do not respond to colchicine in the same way.Mitotic index and labelling index were also found to differ in control lateral roots of different lengths, as a result of fluctuations in the proportion of cells with a short cycle time during root elongation. These results, and the changes found in the response of lateral roots to colchicine as they lengthen, have been discussed with respect to growth hormone levels in developing roots.

CELL PROLIFERATION IN, AND DEVELOPMENT OF, THE APICAL MERISTEM IN ELONGATING LATERAL ROOTS OF VICIA FABA L.

“…Similarly, labelling index {LI), the percentage frequency of tritiated thymidine ([^H]TdR) labelled nuclei, is low, i mm basal to the cap apex in NE, but increases as the secondary root elongates (MacLeod and McLachlan, 1974b). Changes in MI and LI in a tissue do not in themselves indicate that changes bave also taken place in the rate of cell proliferation in that tissue (Clowes, 1972;MacLeod, 1974). However, it is known that the proportion of proliferating cells, or growth fraction (GF), in the apical 2 mm of secondary roots of V.faba, increases as the laterals elongate from 0.2 to i cm (MacLeod, 1973).…”