Abstract
The cell cycle kinetics of Allium cepa meristematic cells has been studied when BrdU was incorporated into DNA at different moments of the S period. When incorporation occurred late in the S period, no delay was observed in the total duration of the interphase, while a significant delay was detected when BrdU was incorporated into DNA during early and middle S, suggesting that a relation may exist in plant cells between time of exposure to BrdU and FdU and the conclusion of the interphase. Furthermore, the high resolution power obtained by the FPG technique after BrdU incorporation into DNA allowed us to calculate the approximate amount of late replicating DNA in the S period. The results indicate that DNA replication is specially active at the end of S.
