SOME OBSERVATIONS ON THE GROWTH OF LATERAL ROOTS OF VICIA FABA L. AND THEIR RESPONSE TO COLCHICINE TREATMENT

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Abstract
Summary: The effect of colchicine treatment on the number of cells in prophase was investigated in the apical meristems of 2‐mm‐, 1‐cm‐and 4‐cm‐ long lateral roots of Vicia faba. 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 1‐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 1‐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.