CELL DOUBLING TIME IN THE APICAL MM OF ELONGATING LATERAL ROOTS OF VICIA FABA L.

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Abstract
Cell doubling time was determined in several ways in the apical mm of newly emerged, 0.2, 1 and 4 cm long lateral roots of V. faba L.; in every case it tended to decrease with increase in root length. Similar values were obtained in the roots of each length investigated when cell doubling time was calculated from the rate of passage of cells into the period of DNA synthesis (S) in both control and colchicine treated roots and from the rate of accumulation of cells in metaphase in the presence of colchicine, assuming cell number increased exponentially, i.e., colchicine had not affected the rate of entry of cells into mitosis of S during the 3-6 h period over which measurements were taken. A discrepancy was found between the values determined for cell doubling time obtained from these rates and those calculated on the basis of the method devised by Evans and his co-workers. Possible reasons for such a discrepancy are discussed.