ABSTRACT
The description of cellular and molecular events in transforming meristems is a relative field of investigations. The apparent lack of interest in the past for the internal changes at the site of flower initiation, that is the meristem, probably rests on two assumptions. Firstly, the refined study of meristems is made difficult because of their small size and inaccessibility that hinder their handling and analysis. Secondly, there was and perhaps still is a belief among physiologists working with photoperiodic plants that once the floral stimulus is produced in the leaves and transported to the receptor meristems subsequent morphogenetic changes follow almost automatically. In Sinapis, there are two mitotic waves during the transition: the first one is clearly associated with cell synchronization while the second, which occurs concurrently with the onset of flower initiation, is related to the increased rate of cell division.
