Cell Cycle Patterns in the Shoot Apex of Lolium temulentum L. cv. Ceres During the Transition to Flowering Following a Single Long Day

Six-week-old Lolium temulentum cv. Ceres plants were induced to flower by a single long day (day 1). The ‘double ridge’ stage was reached on days 4/5. A detailed analysis of apices every 4 h on days 3 to 5 demonstrated synchronized cell division in the apex. However, this synchronized cell division occurred only in the apical summit and axillary bud sites, i.e. only in those regions of the apex which give rise to the spikelets. This indicates a specific activation of the cells in these regions, rather than a general activation of the whole apex.