XVI International Botanical Congess
In mature plant organs, cell size varies within narrow limits so cell number is well correlated with organ size. However, as pointed out by PB Green, cell division per se does not make an organ grow. When maize plants are transferred to low light, primary roots reduce progressively their elongation rate. This is related to an early reduction of the cell flux produced by the meristem. This reduction is due to a shortening of the meristematic zone, not to a lengthening of the cell cycle. It is suggested that sucrose concentration in the meristem controls meristem length ie. whether a cell crossing the meristematic zone will enter a new cycle or not [Muller et al 98 PCE 21 149-]. In parallel, many secondary roots stop elongating and display abnormally long cells in their apical region. En early arrest of cell division probably causes the arrest of elongation of these roots