Evaluation of Sequence and Rate of Lateral-Root Initiation in Pontederia cordata L. by Means of Colchicine Inhibition of Cell Division

Treatment of roots of Pontederia cordata with colchicine for 2 or 4 days led to the production of primordiomorphs, structures resembling lateral-root primordia but formed without cell division. The distribution pattern of primordiomorphs was identical with that previously described for lateral roots in Pontederia; they were regularly spaced along protoxylem-based ranks and there was some coordination of lateral production between ranks. It was therefore assumed that the primordiomorphs represent lateral-root primordia initiated without cell division under the influence of colchicine. The rate of production of primordiomorphs during the experimental period varied between different ranks, and it is suggested that fluctuations in rate of lateral production occur normally within each rank in the root. This would result, at different times, in any given rank initiating laterals either in advance of other ranks or beside preexisting laterals of other ranks, and such circumstances could give rise to the observed degree of correlation between lateral positions in the different ranks.